PROCESS AND SYSTEM FOR PRODUCING LIPF[6], AND MIXTURE CRYSTAL, COMPOSITION, ELECTROLYTE SOLUTION, AND LITHIUM BATTERY CONTAINING LIPF[6]

Abstract

Disclosed are a process and continuous system for producing LiPF.sub.6, and a prepared mixture crystal, composition, electrolyte solution and lithium ion battery containing LiPF.sub.6. During preparation, a first feed stream containing PF5 and a second feed stream containing LiF and HF are introduced into a first microchannel reactor, a gas part of a product in the first microchannel reactor is introduced into a second microchannel reactor to react with a third feed stream containing LiPF.sub.6, LiF and HF, and a liquid part of the product in the first microchannel reactor is subjected to crystallization and drying to obtain LiPF.sub.6. The LiPF.sub.6 has the advantages of a high purity, a uniform particle size, a high product quality stability, etc., and is suitable for use as a component of an electrolyte solution of a lithium ion battery.

Claims

1. A process for producing LiPF.sub.6, comprising: introducing a first feed stream containing PF5 and a second feed stream containing LiF and HF into a first microchannel reactor, introducing a gas part of a product in the first microchannel reactor into a second microchannel reactor to react with a third feed stream containing LiPF.sub.6, LiF and HF, subjecting a liquid part of the product in the first microchannel reactor to crystallization and drying to obtain LiPF.sub.6.

2. The process according to claim 1, wherein the liquid part of the product in the second microchannel reactor can be added to the first microchannel reactor as a fourth feed stream.

3. The process according to claim 1, wherein the first feed stream further comprises a mass transfer promoting component.

4. The process according to claim 1, wherein the mass transfer promoting component in the first feed stream is HCl.

5. The process according to claim 1, wherein the first feed stream further comprises HF.

6. The process according to claim 1, wherein the reaction temperature of the first microchannel reactor and the second microchannel reactor is controlled at 0-17° C.

7. The process according to claim 1, wherein the residence time of the first microchannel reactor and the second microchannel reactor is 5-120 seconds.

8. The process according to claim 1, wherein the liquid part of the product in the first microchannel reactor enters the synthetic liquid tank for storage before entering the crystallization tank for crystallization.

9. A LiPF crystal prepared by the process of claim 1, wherein the purity of the LiPF crystal is more than 99.99 wt%, crystal particles have uniform particle size, and the particle size of more than 80 wt% of crystal particles is 0.2-0.3 mm, and the particle size of more than 90 wt% of crystal particles is 0.18-0.35 mm.

10. A continuous system for producing LiPF.sub.6, wherein the continuous system comprises a PF5 generator, a first microchannel reactor, a gas-liquid separator A, a second microchannel reactor, a gas-liquid separator B, the reverse cycle reaction is carried out with the gas containing PF5 and the HF solution dissolved in LiF as raw materials, the gas generated by the PF5 generator is introduced into the first microchannel reactor, the output material of the first microchannel reactor enters the gas-liquid separator A, the gas separated by the gas-liquid separator A enters the second microchannel reactor as a reaction material to continue the reaction, and the output material of the second microchannel reactor enters the gas-liquid separator B, the liquid components separated by gas-liquid separator B are transported to the first microchannel reactor.

11. The continuous system for producing LiPF.sub.6 according to claim 10, wherein the reverse cycle reaction includes the following features: The mixed gas PF5, HCl and entrained HF gas generated in the PF5 generator are introduced into the first microchannel reactor (3), at the same time, a pump is used to transport the HF solution dissolved in LiF in the first microchannel reactor, PF5 and LiF in HF solution react in the first microchannel reactor.

12. The continuous system for producing LiPF.sub.6 according to claim 10, wherein the second microchannel reactor contains at least two feed streams: one is the gas separated by the gas-liquid separator A, which contains unreacted PF5 and the entrained HF and HCl components, and the other is the HF solution with LiF and LiPF.sub.6 dissolved.

13. The continuous system for producing LiPF.sub.6 according to claim 12, wherein the molar ratio of the reaction raw materials PF5 to LiF in the second microchannel reactor is controlled to be 1:(1-2).

14. The continuous system for producing LiPF.sub.6 According to claim 11, the reverse cycle reaction further includes the following features: the liquid component separated by the gas-liquid separator B contains LiPF.sub.6 and unreacted LiF.

15. The continuous system for producing LiPF.sub.6 according to claim 11, the reverse cycle reaction further includes the following features: the output material of the first microchannel reactor enters the gas-liquid separator A, and the liquid mixture material separated by the gas-liquid separator A enters the synthetic liquid tank and the crystallization tank successively for the crystallization of LiPF.sub.6, and the HF solution containing LiPF.sub.6 after crystallization and filtration is transported to the second microchannel reactor (6) as a third feed stream.

16. The continuous system for producing LiPF.sub.6 according to claim 11, the reverse cycle reaction further includes the following features: the gas separated in the gas-liquid separator B is transported to the HF and HCl separation system through a pressurized device, HCl at the top of the separation system is absorbed into industrial hydrochloric acid by water, and HF at the bottom can be recycled as a reaction raw material.

17. The continuous system for producing LiPF.sub.6 according to claim 15, wherein the crystallization tank is used for crystallization of LiPF.sub.6 in a cooling state, and after the crystallization and filtration, the drying system is used for drying and acid removal to obtain a LiPF.sub.6 product.

18. A LiPF.sub.6 product prepared by the continuous system for producing LiPF.sub.6 according to claim 10, wherein the product has a purity of more than 99.98%.

19. The LiPF.sub.6 product according to claim 18, wherein the types and contents of impurities contained are as follows: water≤20 ppm, free acid (calculated as HF)≤90 ppm, insoluble substance≤200 ppm, sulfate (calculated as SO.sub.4) ≤5 ppm, chloride (calculated as Cl)≤2 ppm, other various metal ions≤1 ppm.

20. A mixture crystal containing LiPF.sub.6, wherein the aspect ratio of the mixture crystal containing LiPF.sub.6 is 1-1.5, the average particle size of the crystal is 0.15-0.4 mm, and in more than 90% of the crystals, the family of crystal planes {110} accounts for 20-80%, the family of crystal planes {111} accounts for 20-80%, and the mixture crystal also contains insoluble substance and free acid.

21. The crystal according to claim 20, wherein 68% or more of the crystals have a particle size of 0.2-0.3 mm, and 80% or more of the crystals have a particle size of 0.18-0.35 mm.

22. The crystal according to claim 20, wherein in more than 80% of the crystals, the family of crystal planes{110} accounts for 40-60%, and the family of crystal planes {111} accounts for 40-60%.

23. The crystal according to claim 20, wherein the angle of repose of the crystal is 20-40°.

24. The crystal according to claim 20, wherein the bulk density of the crystal is 1.3-1.8 g/mL.

25. The crystal according to claim 20, wherein the mass percentage of LiPF.sub.6 in the crystal is 99.90-99.995%.

26. The crystal according to claim 20, wherein a method for preparing the crystal comprises: using a stream containing PF5 and a stream containing LiF and HF as raw materials, performing a continuous reverse cycle reaction in a first microchannel reactor and a second microchannel reactor.

27. The crystal according to claim 26, wherein the reaction temperature of the first microchannel reactor and the second microchannel reactor is 0-17° C., and the residence time in the reactors is 5-120 s.

28. The crystal according to claim 27, wherein the molar ratio of PF5 to LiF in the first microchannel reactor is (2-5):1, and the molar ratio of PF5 to LiF in the second microchannel reactor is 1:(1-2).

29. A composition, comprising a LiPF.sub.6 crystal and water, the particle size distribution of LiPF.sub.6 crystal is uniform, 35-50% of the crystal particle size is greater than or equal to 0.2 mm and less than 0.25 mm, and 35-50% of the crystal particle size is greater than or equal to 0.25 mm, less than or equal to 0.3 mm, the water content of the composition is less than 8 ppm.

30. The composition according to claim 29, wherein 40-50% of the crystal particle size is greater than or equal to 0.2 mm and less than 0.25 mm, and 40-50% of the crystal particle size is greater than or equal to 0.25 mm and less than or equal to 0.3 mm.

31. The composition according to claim 29, wherein the preparation of the composition utilizes a microchannel reactor, and there are two microchannel reactors, in the composition preparation process, a gas part of a product in the first microchannel reactor enters a second microchannel reactor, and a liquid part of the product in the second microchannel reactor enters the first microchannel reactor.

32. The composition according to claim 31, wherein in the preparation process, the feed stream entering the first microchannel reactor is the first feed stream containing PF5, the second feed stream containing LiF and HF and the fourth feed stream of a liquid part of a product in the second microchannel reactor, and the feed stream entering the second microchannel reactor is a gas part of a product in the first microchannel reactor and a third feed stream containing LiPF.sub.6, LiF and HF.

33. The composition according to claim 32, wherein in the preparation process, the first feed stream containing PF5 is directly introduced into the first microchannel reactor after being generated from the PF5 generator, and there is no need of a separation process.

34. A non-aqueous electrolyte solution, comprising a lithium salt and an organic solvent, wherein the lithium salt is a mixture crystal containing LiPF.sub.6, the aspect ratio of the mixture crystal is 1-1.5, and the average particle size of the crystal is 0.15-0.4 mm, in more than 90% of the crystals, the family of crystal planes {110} accounts for 20-80%, the family of crystal planes{111} accounts for 20-80%, the mixture crystal also contains insoluble substance and free acid, and the mass percentage of LiPF.sub.6 in the mixture crystal is 99.90-99.995 %.

35. The non-aqueous electrolyte solution according to claim 34, wherein the concentration of LiPF.sub.6 in the non-aqueous electrolyte solution is 0.6-2 mol/L.

36. The non-aqueous electrolyte solution according to claim 34, wherein the non-aqueous electrolyte solution further comprises an additive, the additive comprises at least two of lithium difluorophosphate, lithium bis(trifluoromethanesulphonyl)imide and fluorocarbonate.

37. The non-aqueous electrolyte solution according to claim 36, wherein relative to 100% by weight of the electrolyte solution, the additive is added in an amount of 0.01-5%.

38. The non-aqueous electrolyte solution according to claim 36, wherein the weight ratio of lithium difluorophosphate, lithium bis(trifluoromethanesulphonyl)imide and fluorocarbonate is 1: (0.5-1.5): (2.5-3.5) relative to 100% by weight of the electrolyte solution.

39. The non-aqueous electrolyte solution according to claim 36, wherein the fluorocarbonate comprises fluoroethylene carbonate and/or trifluoropropylene carbonate.

40. The non-aqueous electrolyte solution according to claim 39, wherein the weight ratio of the fluoroethylene carbonate to the trifluoropropylene carbonate is 1:(1-6).

41. The non-aqueous electrolyte solution according to claim 34, wherein the organic solvent comprises a non-aqueous solvent of cyclic carbonate and/or chain carbonate.

42. The non-aqueous electrolyte solution according to claim 41, wherein the volume ratio of the cyclic carbonate to the chain carbonate is 1:(1-9).

43. A secondary lithium battery, wherein the non-aqueous electrolyte solution of claim 34 is used.

44. A highly stable fluorine-containing electrolyte solution, comprising LiPF.sub.6, the LiPF.sub.6 used in the preparation of the fluorine-containing electrolyte solution is LiPF.sub.6 with 68% (wt) or more of the particle size greater than or equal to 0.2 mm and less than or equal to 0.3 mm, the water content of the LiPF.sub.6 is lower than 6 ppm, the purity of LiPF.sub.6 is above 99.99%, and the mass percentage of LiPF.sub.6 in the fluorine-containing electrolyte solution is 5-20 wt%.

45. The fluorine-containing electrolyte solution according to claim 44, wherein the particle size of the LiPF.sub.6 crystal used in the preparation of the fluorine-containing electrolyte solution is uniformly distributed, and 30-50% of the crystal particle size is greater than or equal to 0.2 mm and less than 0.25 mm, and 30-50% of the crystal particle size is greater than or equal to 0.25 mm and less than or equal to 0.3 mm.

46. The fluorine-containing electrolyte solution according to claim 45, wherein the particle size of the LiPF.sub.6 crystal used in the preparation of the fluorine-containing electrolyte solution is uniformly distributed, and 40-50% of the crystal particle size is greater than or equal to 0.2 mm and less than 0.25 mm, and 40-50% of the crystal particle size is greater than or equal to 0.25 mm and less than or equal to 0.3 mm.

47. The fluorine-containing electrolyte solution according to claim 44, wherein the fluorine-containing electrolyte solution further comprises at least one of LiPO.sub.2F.sub.2, LiBF.sub.2C.sub.2O.sub.4, LiBF.sub.4, LiPF.sub.6, LiFSI, LiTFSI, LiAsF.sub.6, LiClO.sub.4, LiSO3CFs, LiC.sub.2O.sub.4BC.sub.2O.sub.4, LiF.sub.2BC.sub.2O.sub.4, LiPO.sub.2F.sub.2, LiPF.sub.2, LiPF.sub.4C.sub.2O.sub.4 and LiPF.sub.2C.sub.4O.sub.8, and the mass percentage thereof in the electrolyte solution is 0.1- 5 wt%.

48. The fluorine-containing electrolyte solution according to claim 47, wherein the fluorine-containing electrolyte solution comprises LiPO.sub.2F.sub.2 and LiBF.sub.2C.sub.2O.sub.4.

49. The fluorine-containing electrolyte solution according to claim 47, wherein the fluorine-containing electrolyte solution further comprises1,2-Bis(trifluoromethyl)benzene, and the mass percentage of 1,2-Bis(trifluoromethyl)benzene in the fluorine-containing electrolyte solution is 0.1-3 wt%.

50. The fluorine-containing electrolyte solution according to claim 44, wherein the fluorine-containing electrolyte solution comprises ethylene carbonate, ethyl methyl carbonate and diethyl carbonate, and the total mass percentage of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in the fluorine-containing electrolyte solution is 70-90 wt%, and the mass ratio of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate is (2.5-3.5): (4.5-5.5): (1.5-2.5).

51. The fluorine-containing electrolyte solution according to claim 44, wherein LiPF.sub.6 is LiPF.sub.6 prepared by using two microchannel reactors.

52. A lithium ion battery using the fluorine-containing electrolyte solution of any one of claims 44.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0165] FIG. 1 is a flow chart of a process for producing LiPF.sub.6 of the present invention.

[0166] FIG. 2 is a process flow diagram of a continuous system for producing LiPF.sub.6 in Example 2.1.

[0167] FIG. 3 is a process flow diagram of a continuous system for producing LiPF.sub.6 in Example 2.2.

[0168] FIG. 4 is a SEM image of a mixture crystal containing LiPF.sub.6 prepared in Example 3.1 and Example 5.1;

[0169] FIG. 5 is a SEM image of a mixture crystal containing LiPF.sub.6 prepared in Comparative Example 3.1;

[0170] FIG. 6 is a XRD pattern of a mixture crystal containing LiPF.sub.6 prepared in Example 3.1.

[0171] Reference numerals: 1-solid conveyor; 2-PF5 generator; 3-first microchannel reactor; 4-first gas-liquid separator; 5-synthetic liquid tank; 6-second microchannel reactor; 7-second gas-liquid separator; 8-separation system; 9-crystallization tank; 10-drying system; 11-mother liquor tank; 12-LiF dissolution tank.

DETIALED DESCRIPTION

[0172] The production process of the present invention will be described in detail through the following embodiments, but the present invention is not limited to these embodiments.

Example 1.1

[0173] PC15 was transported to a PF5 generator 2 with a cooling jacket that stored HF through a solid conveyor 1 with a metering device, and the temperature was controlled to be about 0° C. PCl5 reacted with HF to produce PF5 and HCl. The mixed gas PF5, HCl and entrained HF gas were introduced into a first microchannel reactor 3 to form a first feed stream. In the dissolution tank with cooling jacket and stirrer, HF was added, and LiF was added into the dissolution tank with a solid feeding device while cooling, and the dissolution temperature was controlled at about 0° C., and the mass fraction of LiF to be 2 wt%. The HF solution with dissolved LiF was pumped into the first microchannel reactor 3 to form a second feed stream. The reaction temperature of the first microchannel reactor 3 was 3° C., and the residence time was 5 seconds. The gas- liquid mixture material from the first microchannel reactor 3 entered the first gas-liquid separator 4, and the liquid in the first gas-liquid separator 4 was transported to the synthetic liquid tank 5 for storage, and the gases separated by the first gas-liquid separator included unreacted PF5, HCl and entrained HF. The mixed gas was transported to the second microchannel reactor 6 to react with the third feed stream containing LiPF.sub.6, LiF and HF. The reaction temperature of the second microchannel reactor 6 was 3° C., and the residence time was 5 seconds. The gas-liquid mixture in the second microchannel reactor entered the second gas-liquid separator 7, and the gas separated by the second gas-liquid separator 7 contained HCl and entrained HF, and the mixed gas entered a HF and HCl separation system 8 through a pressurized device. The liquid separated by the second gas-liquid separator 7 contained LiPF.sub.6 in the original mother liquor, LiPF.sub.6 produced by the new reaction and LiF that was not reacted completely. The mixed liquid was transported to the first microchannel reactor 3 as a fourth feed stream. The synthetic liquid in the synthetic liquid tank 5 was transported to a crystallization tank 9 for crystallization of LiPF.sub.6, and LiPF.sub.6 was crystallized in a cooling state. In the crystallization tank 9, the cooling rate of the synthetic liquid was 2° C./h, the stirring rate of the stirrer was 50 rpm, the synthetic liquid was cooled from 20° C. to -45° C., and kept for 6 hours after cooled to -45° C. Then drying and acid removal was carried out in the drying system 10 after solid crystallization and filtration, to obtain a LiPF.sub.6 crystal. The filtered mother liquor was stored in the mother liquor tank 11. After the content of LiPF.sub.6 in mother liquor in mother liquor tank 11 was determined quantitatively, the mother liquor was conveyed to the LiF dissolution tank 12 for the preparation of quantitative LiF solution. The HF solution containing LiPF.sub.6 dissolved a certain amount of LiF and was transported to the second microchannel reactor 6 for reaction to form the third feed stream. The molar ratio of PF5 to LiF in the first microchannel reactor was 2:1, and the molar ratio of PF5 to LiF in the second microchannel reactor was 1:1.

[0174] After testing, the purity of the generated LiPF.sub.6 crystal was 99.99%, the yield was 99.6%, the particle size of more than 82% (wt) of the crystal particles was 0.2-0.3 mm, and the particle size of more than 91% (wt) of the crystal particles was 0.18-0.35 mm.

Example 1.2

[0175] The process of this example was basically the same as that of Example 1.1, except the difference that the reaction temperature of the first microchannel reactor was 5° C., the residence time was 10 seconds, the reaction temperature of the second microchannel reactor was 8° C., and the residence time was 10 seconds.

[0176] After testing, the purity of the generated LiPF.sub.6 crystal was 99.994%, the yield was 99.8%, the particle size of more than 85% (wt) of the crystal particles was 0.2-0.3 mm, and the particle size of more than 93% (wt) of the crystal particles was 0.18 -0.35 mm.

Example 1.3

[0177] The process of this example was basically the same as that of Example 1.2, except the difference that the molar ratio of PF5 to LiF in the first microchannel reactor was 2.5:1, and the molar ratio of PF5 to LiF in the second microchannel reactor was 1:1.1.

[0178] After testing, the purity of the generated LiPF.sub.6 crystal was 99.995%, the yield was 99.8%, the particle size of more than 85% (wt) of the crystal particles was 0.2-0.3 mm, and the particle size of more than 94% (wt) of the crystal particles was 0.18-0.35 mm.

Example 1.4

[0179] The process of this example was basically the same as that of Example 1.1, except the difference that the reaction temperature of the first microchannel reactor was 4° C., the residence time was 10 seconds, the reaction temperature of the second microchannel reactor was 6° C., and the residence time was 12 seconds.

[0180] After testing, the purity of the resulting LiPF.sub.6 crystal was 99.995%, the yield was 99.85%, the particle size of more than 85% (wt) of the crystal particles was 0.2-0.3 mm, and the particle size of more than 94% (wt) of the crystal particles was 0.18 -0.35 mm.

Example 1.5

[0181] The process of this example was basically the same as that of Example 1.1, except the difference that in the crystallization tank, the cooling rate of the synthetic liquid was 35° C./h, the stirring speed of the stirrer was 800 rpm, the synthetic liquid was cooled from 25° C. to -10° C., and kept for 1 hour after cooling to -10° C.

[0182] After testing, the purity of the generated LiPF.sub.6 crystal was 99.994%, the yield was 99.83%, the particle size of more than 86% (wt) of crystal particles was 0.2-0.3 mm, and the particle size of more than 92% (wt) of crystal particles was 0.18 -0.35 mm.

Comparative Example 1.1

[0183] This comparative example was basically the same as that of Example 1.1, except the difference that the first feed stream that was introduced into the first microchannel reactor was purified PF5 gas.

[0184] After testing, the purity of the generated LiPF.sub.6 crystal was 99.91%, the yield was 99.3%, the particle size of more than 70% (wt) of crystal particles was 0.2-0.3 mm, and the particle size of more than 75% (wt) of crystal particles was 0.18-0.35 mm.

Comparative Example 1.2

[0185] This comparative example was basically the same as that of Example 1.1, except the difference that the first feed stream that was introduced into the first microchannel reactor was purified PF5 gas. No second microchannel reactor was set. The molar ratio of PF5 to LiF in the first microchannel reactor was 1.5:1.

[0186] After testing, the purity of the generated LiPF.sub.6 crystal was 99.85%, the yield was 98.3%, the particle size of more than 62% (wt) of crystal particles was 0.2-0.3 mm, and the particle size of more than 67% (wt) of crystal particles was 0.18-0.35 mm.

Comparative Example 1.3

[0187] This comparative example was basically the same as that of Example 1.1, except the difference that the first and second microchannel reactors were replaced by the first and second reactors, respectively. After being replaced with reactors, for batch production, the reaction time of the first and second reactors increased to 5 hours.

[0188] After testing, the purity of the resulting LiPF.sub.6 crystal was 99.7%, the yield was 95.6%, the particle size of more than 55% (wt) of crystal particles was 0.2-0.3 mm, and the particle size of more than 60% (wt) of crystal particles was 0.18-0.35 mm.

Comparative Example 1.4

[0189] This comparative example was basically the same as that of Example 1.2, except the difference that in the crystallization tank, the cooling rate of the synthetic liquid was 10° C./h, the stirring speed of the stirrer was 100 rpm, the synthetic liquid was cooled from 25° C. to -45° C., and kept for 6 hours after cooling to -45° C.

[0190] After testing, the purity of the generated LiPF.sub.6 crystal was 99.96%, the yield was 99.5%, the particle size of more than 72% (wt) of crystal particles was 0.2-0.3 mm, and the particle size of more than 80% (wt) of crystal particles was 0.18-0.35 mm.

Instructions for Examples 2.1 to 2.3

[0191] Examples 2.1 to 2.3 provided a continuous system for producing LiPF.sub.6 based on a microchannel reactor. The continuous system included a PF5 generator (2), a first microchannel reactor (3), a gas-liquid separator A (4), a second microchannel reactor (6), and a gas-liquid separator B (7). The reverse cycle reaction was carried out by using the gas containing PF5 and HF solution with dissolved LiF as raw materials. Wherein, the first microchannel reactor (3) and the second microchannel reactor (6) were reactors with the same structure, which were enhanced hybrid channel structures; the cross-sectional shape of the channel was a heart-shaped structure, the equivalent diameter of the channel was 2 mm, and the liquid holding volume was 50 ml. The hard material of the channel walls was silicon carbide.

[0192] Preferably, the continuous system transported PCl .sub.5 to a PF5 generator (2) that stored HF through a solid conveyor (1) with a metering device, and PCl.sub.5 reacted with HF to generate PF5 and by-product HCl, as shown in the chemical formula (1). Further, the solid conveyor (1) was preferably a solid conveyor (1) with a metering device; the PF5 generator (2) that stored HF was preferably a PF5 generator (2) with a cooling jacket that stored HF, further preferably a PF5 generator with a stirring device.

##STR(1)##

[0193] The mixed gas PF5, HCl and entrained HF gas generated in the PF5 generator (2) were introduced into the microchannel reactor A (3), and the HF solution with dissolved LiF was transported simultaneously with a pump in the first microchannel reactor (3). LiF in PF5 and HF solution reacted rapidly and released the reaction heat, as shown in the chemical formula (2).

##STR(2)##

[0194] The gas-liquid mixture material from the first microchannel reactor (3) mainly contained the target product LiPF.sub.6, unreacted PF5, and HCl and HF that were not involved in the reaction.

[0195] The gas-liquid mixture material from the first microchannel reactor (3) entered the gas-liquid separator A (4) for gas-liquid separation, and the liquid therein, namely the LiPF.sub.6-containing component, was transported to the synthetic liquid tank (5) to store. The separated gas that contained unreacted PF5 and entrained HF and HC components was transported to the second microchannel reactor (6), and reacted with the HF solution in which LiF and LiPF.sub.6 were dissolved. LiF in PF5 and HF solution reacted rapidly and released the reaction heat, as shown in the chemical formula (3).

##STR(3)##

[0196] The gas-liquid mixture material coming out of the second microchannel reactor (6) mainly contained the target product LiPF.sub.6, HCl and HF.

[0197] The gas-liquid mixture coming out of the second microchannel reactor (6) entered the gas-liquid separator B (7), the gas separated in the gas-liquid separator B (7) contained HCl and HF, and the separated liquid contained LiPF.sub.6 and unreacted LiF.

[0198] Preferably, the gas separated in the gas-liquid separator B (7) was transported to the HF and HCl separation system (8) through a pressurized device. The HCl at the top of the separation system (8) was absorbed by water to form industrial hydrochloric acid, and the HF at the bottom could be recycled as the reaction raw material. The HF and HCl separation system (8) was preferably a separating tower.

[0199] The liquid separated in gas-liquid separator B (7), namely, the mixed liquid containing LiPF.sub.6 and unreacted LiF, was transported to the first microchannel reactor (3) to continue to react with the PF5 therein, so that the LiF in the mixed liquid could react completely.

[0200] The synthetic liquid in the synthetic liquid tank (5) was transported to the crystallization tank (9) for crystallization of LiPF.sub.6. LiPF.sub.6 was crystallized in the cooling state. After the crystallization and filtration, drying and acid removal was carried out in a drying system (10), to obtain the LiPF.sub.6 product.

[0201] Further preferably, the filtered mother liquor was stored in the mother liquor tank (11), and after the LiPF.sub.6 content in the mother liquor in the mother liquor tank (11) was quantitatively determined, the mother liquor was delivered to the LiF dissolution tank (12) for the preparation of quantitative LiF solution. The HF solution containing LiPF.sub.6 dissolved a quantitative amount of LiF and was transported to the second microchannel reactor (6) for the reaction. So far, the reaction system could run continuously.

[0202] A LiPF.sub.6 product prepared by the above continuous system for producing LiPF.sub.6 could achieve high purity, and there was no need of further purification. The purity could reach more than 99.98%, preferably more than 99.99%. The types and contents of impurities included were as follows: water ≤20 ppm, preferably ≤15 ppm; free acid (calculated as HF) ≤90 ppm, preferably ≤80 ppm, more preferably ≤50 ppm; insoluble substance ≤200 ppm, preferably ≤160 ppm, more preferably ≤110 ppm; sulfate (calculated as SO.sub.4) ≤5 ppm, preferably ≤4 ppm; chloride (calculated as Cl) ≤2 ppm; other various metal ions ≤1 ppm.

Example 2.1

[0203] Example 2.1 was further described in detail below with reference to FIG. 2. HF was transported by a pump in a dissolution tank with a cooling jacket and a stirrer, and LiF was added through a solid feeding device while cooling. The speed of adding LiF should be appropriate to control the HF temperature at 0° C. The concentration of LiF was 5 wt%. At the same time, PCl.sub.5 was transported to the PF5 generator (2) containing HF through the solid conveyor (1) with a metering device to generate PF5 gas. Under pressurization, the HF solution with dissolved LiF and PF5 gas were transported to the first microchannel reactor (3) by a pump. The molar ratio of the reactant PF5 to LiF in the first microchannel reactor (3) was 2:1, the residence time of the reactants was 30 seconds, and the reaction temperature was 15° C. The reactants entered the first microchannel reactor (3) in a continuous state, and the output materials were output in a continuous state and then entered the gas-liquid separator A (4) for gas-liquid separation. The liquid phase product obtained by separation, namely the component containing LiPF.sub.6, was transported to the synthetic liquid tank (5) for standby. The separated gas phase product, namely, the component containing unreacted PF5 and entrained HF and HCl, was transported to the second microchannel reactor (6), and reacted with the HF solution with dissolved LiF (containing LiPF.sub.6). The molar ratio of the reactant PF5 to LiF in the second microchannel reactor (6) was 1:1.67, the residence time of the reactants was 30 seconds, and the reaction temperature was 15° C. The mixed material coming out of the second microchannel reactor (6) entered the gas-liquid separator B (7), the gas separated in the gas-liquid separator B (7) contained HCl and HF, the separated liquid contained LiPF.sub.6 and unreacted LiF. The gas separated in the gas-liquid separator B (7) was pressurized by entering a compressor, and then transported to the HF and HCl separation system (8), namely, the separating tower. The HCl at the top of the tower was absorbed by water to form industrial hydrochloric acid, and the HF at the bottom of the tower could be recycled.

[0204] The liquid separated in the gas-liquid separator B (7), namely, the mixed liquid containing LiPF.sub.6 and unreacted LiF, was transported to the synthetic liquid tank (5), and the synthetic liquid in the synthetic liquid tank (5) was transported to the crystallization tank (9) by a pump for crystallization of LiPF.sub.6. LiPF.sub.6 was crystallized in a cooling state. After the crystallization and filtration, heating and nitrogen purging and drying, and acid removal were carried out in the drying system (10), to obtain the LiPF.sub.6 product.

Example 2.2

[0205] Example 2.2 was further described in detail below with reference to FIG. 3. HF was transported by a pump in a dissolution tank with a cooling jacket and a stirrer, and LiF was added through a solid feeding device while cooling. The speed of adding LiF should be appropriate to control the HF temperature at 0° C. The concentration of LiF was 4 wt%. At the same time, PCl.sub.5 was transported to the PF5 generator (2) containing HF through the solid conveyor (1) with a metering device to generate PF5 gas. Under pressurization, the HF solution with dissolved LiF and PF5 gas were transported to the first microchannel reactor (3) by a pump. The molar ratio of the reactant PF5 to LiF in the first microchannel reactor (3) was 2:1, the residence time of the reactants was 30 seconds, and the reaction temperature was 15° C. The reactants entered the first microchannel reactor (3) in a continuous state, and the output materials were output in a continuous state and then entered the gas-liquid separator A (4) for gas-liquid separation. The liquid phase product obtained by separation, namely the component containing LiPF.sub.6, was transported to the synthetic liquid tank (5) for standby. The separated gas phase product, namely, the component containing unreacted PF5 and entrained HF and HCl, was transported to the second microchannel reactor (6), and reacted with the HF solution with dissolved LiF (containing LiPF.sub.6). The molar ratio of the reactant PF5 to LiF in the microchannel reactor B (6) was 1:1.67, the residence time of the reactants was 30 seconds, and the reaction temperature was 15° C. The mixed material coming out of the second microchannel reactor (6) entered the gas-liquid separator B (7), the gas separated in the gas-liquid separator B (7) contained HCl and HF, the separated liquid contained LiPF.sub.6 and unreacted LiF. The gas separated in the gas-liquid separator B (7) was pressurized by entering a compressor, and then transported to the HF and HCl separation system (8), namely, the separating tower. The HCl at the top of the tower was absorbed by water to form industrial hydrochloric acid, and the HF at the bottom of the tower could be recycled.

[0206] The liquid separated in the gas-liquid separator B (7), namely, the mixed liquid containing LiPF.sub.6 and unreacted LiF, was transported to the first microchannel reactor (3) by a pump, to continue to react with PF5 therein, so that the LiF in the mixed liquid reacted completely. Namely, the continuous reverse cycle LiPF.sub.6 synthesis reaction consisting of two microchannel reactors was completed. The synthetic liquid in the synthetic liquid tank (5) was transported to the crystallization tank (9) by a pump for crystallization of LiPF.sub.6. LiPF.sub.6 was crystallized in a cooling state. After the crystallization and filtration, heating and nitrogen purging and drying, and acid removal were carried out in the drying system (10), to obtain the LiPF.sub.6 product.

Example 2.3

[0207] Example 2.3 was further described in detail below with reference to FIG. 1. HF was transported by a pump in a dissolution tank with a cooling jacket and a stirrer, and LiF was added through a solid feeding device while cooling. The speed of adding LiF should be appropriate to control the HF temperature at 0° C. The concentration of LiF was 4 wt%. At the same time, PCl.sub.5 was transported to the PF5 generator (2) containing HF through the solid conveyor (1) with a metering device to generate PF5 gas. Under pressurization, the HF solution with dissolved LiF and PF5 gas were transported to the first microchannel reactor (3) by a pump. The molar ratio of the reactant PF5 to LiF in the first microchannel reactor (3) was 2:1, the residence time of the reactants was 30 seconds, and the reaction temperature was 15° C. The reactants entered the microchannel reactor A (3) in a continuous state, and the output materials were output in a continuous state and then entered the gas-liquid separator A (4) for gas-liquid separation. The liquid phase product obtained by separation, namely the component containing LiPF.sub.6, was transported to the synthetic liquid tank (5) for standby. The separated gas phase product, namely, the component containing unreacted PF5 and entrained HF and HCl, was transported to the second microchannel reactor (6), and reacted with the HF solution with dissolved LiF (containing LiPF.sub.6). The molar ratio of the reactant PF5 to LiF in the second microchannel reactor (6) was 1:1.67, the residence time of the reactants was 30 seconds, and the reaction temperature was 15° C. The mixed material coming out of the second microchannel reactor (6) entered the gas-liquid separator B (7), the gas separated in the gas-liquid separator B (7) contained HCl and HF, the separated liquid contained LiPF.sub.6 and unreacted LiF. The gas separated in the gas-liquid separator B (7) was pressurized by entering a compressor, and then transported to the HF and HCl separation system (8), namely, the separating tower. The HCl at the top of the tower was absorbed by water to form industrial hydrochloric acid, and the HF at the bottom of the tower could be recycled.

[0208] The liquid separated in the gas-liquid separator B (7), namely, the mixed liquid containing LiPF.sub.6 and unreacted LiF, was transported to the first microchannel reactor (3) by a pump, to continue to react with PF5 therein, so that the LiF in the mixed liquid reacted completely. Namely, the continuous reverse cycle LiPF.sub.6 synthesis reaction consisting of two microchannel reactors was completed. The synthetic liquid in the synthetic liquid tank (5) was transported to the crystallization tank (9) by a pump for crystallization of LiPF.sub.6. LiPF.sub.6 was crystallized in a cooling state. After the crystallization and filtration, heating and nitrogen purging and drying, and acid removal were carried out in the drying system (10), to obtain the LiPF.sub.6 product.

[0209] The filtered mother liquor was further stored in the mother liquor tank (11), and after the LiPF.sub.6 content in the mother liquor in the mother liquor tank (11) was quantitatively determined, the mother liquor was delivered to the LiF dissolution tank (12) for the preparation of quantitative LiF solution. The HF solution containing LiPF.sub.6 dissolved a certain amount of LiF and was transported to the second microchannel reactor 6 for reaction.

Comparative Example 2.1

[0210] HF was transported by a pump in a dissolution tank with a cooling jacket and a stirrer, and LiF was added through a solid feeding device while cooling. The speed of adding LiF should be appropriate to control the HF temperature at 0° C. The concentration of LiF was 4 wt%. At the same time, PCl.sub.5 was transported to the PF5 generator (2) containing HF through the solid conveyor (1) with a metering device to generate PF5 gas. Under pressurization, the HF solution with dissolved LiF and PF5 gas were transported to the first microchannel reactor (3) by a pump. The molar ratio of the reactant PF5 to LiF in the first microchannel reactor A (3) was 2:1, the residence time of the reactants was 30 seconds, and the reaction temperature was 15° C. The reactants entered the first microchannel reactor A (3) in a continuous state, and the output materials were output in a continuous state and then entered the gas-liquid separator A (4) for gas-liquid separation. The liquid phase product obtained by separation, namely the component containing LiPF.sub.6, was transported to the synthetic liquid tank (5). The synthetic liquid in the synthetic liquid tank (5) was transported to the crystallization tank (9) by a pump for crystallization of LiPF.sub.6. LiPF.sub.6 was crystallized in a cooling state. After the crystallization and filtration, heating and nitrogen purging and drying, and acid removal were carried out in the drying system (10), to obtain the LiPF.sub.6 product.

Comparative Example 2.2

[0211] HF was transported by a pump in a dissolution tank with a cooling jacket and a stirrer, and LiF was added through a solid feeding device while cooling. The speed of adding LiF should be appropriate to control the HF temperature at 0° C. The concentration of LiF was 4 wt%. At the same time, PCl.sub.5 was transported to the PF5 generator (2) containing HF through the solid conveyor (1) with a metering device to generate PF5 gas. Under pressurization, the HF solution with dissolved LiF and PF5 gas were transported to the first microchannel reactor (3) by a pump. The molar ratio of the reactant PF5 to LiF in the microchannel reactor A (3) was 2:1, the residence time of the reactants was 30 seconds, and the reaction temperature was 15° C. The reactants entered the first microchannel reactor (3) in a continuous state, and the output materials were output in a continuous state and then entered the second microchannel reactor (6), the residence time of the reactants was 30 seconds, and the reaction temperature was 15° C. The mixed material coming out of the second microchannel reactor (6) entered the gas-liquid separator A (4) for gas-liquid separation. The liquid phase product obtained by separation, namely the component containing LiPF.sub.6, was transported to the synthetic liquid tank (5). The synthetic liquid in the synthetic liquid tank (5) was transported to the crystallization tank (9) by a pump for crystallization of LiPF.sub.6. LiPF.sub.6 was crystallized in a cooling state. After the crystallization and filtration, heating and nitrogen purging and drying, and acid removal were carried out in the drying system (10), to obtain the LiPF.sub.6 product.

TABLE-US-00001 Test Item Example 2.1 Example 2.2 Example 2.3 Comparative Example 2.1 Comparative Example 2.2 Purity (%) (wt) 99.98 99.98 99.98 99.83 99.79 Insoluble substances (ppm) 150 160 145 240 220 Water (ppm) 14 12 15 28 25 Free acid (calculated as HF) (ppm) 73 76 79 160 180 Sulfate (calculated as SO4.sub.) (ppm) 4 4 4 11 17 chloride (calculated as Cl) (ppm) 4 4 4 25 25 Other metal ions (ppm) 0.8 0.8 0.8 3 3 HF conversion rate (%) 86 88 90 72 75 PCl.sub.5 conversion rate (%) 88 90 91 71 73 LiF conversion rate (%) 85 89 89 69 70

[0212] As shown in Table 1, Example 2.1-2.3 adopted two groups of microchannel reactors. After the reverse cycle reaction, the purity of the product was significantly higher than that of Comparative Example 2.1 using a single microchannel reactor and that of Comparative Example 2.2 directly connecting two groups of microchannel reactors in series; the content of impurities was lower, and the conversion rate of the product was higher.

Example 3.1

[0213] PC15 was transported to a PF5 generator with a cooling jacket that stored HF through a solid conveyor with a metering device, and the temperature was controlled to be about 0° C. PC15 reacted with HF to produce PF5 and HCl. The mixed gas PF5, HCl and entrained HF gas were introduced into a first microchannel reactor to form a first feed stream. In the dissolution tank with cooling jacket and stirrer, HF was added, and LiF was added into the dissolution tank with a solid feeding device while cooling, and the dissolution temperature was controlled at about 0° C., and the mass fraction of LiF to be 2 wt%. The HF solution with dissolved LiF was pumped into the first microchannel reactor to form a second feed stream. The reaction temperature of the first microchannel reactor was 3° C., and the residence time was 5 seconds. The gas- liquid mixture material from the first microchannel reactor entered the first gas-liquid separator, and the liquid in the first gas-liquid separator was transported to the synthetic liquid tank for storage, and the gases separated by the first gas-liquid separator included unreacted PF5, HCl and entrained HF. The mixed gas was transported to the second microchannel reactor to react with the third feed stream containing LiPF.sub.6, LiF and HF. The reaction temperature of the second microchannel reactor was 3° C., and the residence time was 5 seconds. The gas-liquid mixture in the second microchannel reactor entered the second gas-liquid separator, and the gas separated by the second gas-liquid separator contained HCl and entrained HF, and the mixed gas entered a HF and HCl separation system through a pressurized device. The liquid separated by the second gas-liquid separator contained LiPF.sub.6 in the original mother liquor, LiPF.sub.6 produced by the new reaction and LiF that was not reacted completely. The mixed liquid was transported to the first microchannel reactor as a fourth feed stream. The synthetic liquid in the synthetic liquid tank was transported to a crystallization tank for crystallization of LiPF.sub.6, and LiPF.sub.6 was crystallized in a cooling state. In the crystallization tank, the cooling rate of the synthetic liquid was 2° C./h, the stirring rate of the stirrer was 50 rpm, the synthetic liquid was cooled from 20° C. to -45° C., and kept for 6 hours after cooled to -45° C. Then drying and acid removal was carried out in the drying system after solid crystallization and filtration, to obtain a LiPF.sub.6 crystal. The filtered mother liquor was stored in the mother liquor tank. After the content of LiPF.sub.6 in mother liquor in mother liquor tank was determined quantitatively, the mother liquor was conveyed to the LiF dissolution tank for the preparation of quantitative LiF solution. The HF solution containing LiPF.sub.6 dissolved a certain amount of LiF and was transported to the second microchannel reactor for reaction to form the third feed stream. The molar ratio of PF5 to LiF in the first microchannel reactor was 2:1, and the molar ratio of PF5 to LiF in the second microchannel reactor was 1:1.

[0214] The specific performance parameters of the prepared crystal were shown in Table 2, the SEM image of the crystal was shown in FIG. 4, and the XRD pattern of the crystal was shown in FIG. 6.

Example 3.2

[0215] The mixture crystal containing LiPF.sub.6 was prepared according to the steps and conditions of Example 3.1, except that the molar ratio of PF5 to LiF in the first microchannel reactor was 2.5:1, and the molar ratio of PF5 to LiF in the second microchannel reactor was 1:1.1.

[0216] The specific performance parameters of the prepared crystals were shown in Table 2.

Example 3.3

[0217] The mixture crystal containing LiPF.sub.6 was prepared according to the steps and conditions of Example 3.1, except that the reaction temperature of the first microchannel reactor was 4° C., the residence time was 10 seconds, the reaction temperature of the second microchannel reactor was 6° C., and the residence time was 12 seconds.

[0218] The specific performance parameters of the prepared crystals were shown in Table 2.

Comparative Example 3.1

[0219] The LiPF.sub.6 crystal was prepared according to the steps and conditions of Example 3.1, with the difference that no second microchannel reactor was set, and the reaction was only carried out in the first microchannel reactor. The specific performance parameters of the prepared crystal were shown in Table 2, and the SEM image of the crystal was shown in FIG. 5.

TABLE-US-00002 Example 3.1 Example 3.2 Example 3.3 Comparative Example 3.1 Aspect ratio 1-1.5 1-1.3 1-1.4 1-1.6 Average particle size(mm) 0.2 0.25 0.3 0.4 Proportion of crystals with a particle size of 0.2-0.3 mm (wt) 82% 85% 85% 48% Proportion of crystals with a particle size of 0.18-0.35 mm (wt) 91% 94% 94% 60% Proportion of family of crystal planes {110} and family of crystal planes{111} accounting for 20-80% of the crystals (wt) respectively 91% 95% 93% 75% Proportion of family of crystal planes {110} and family of crystal planes{111} accounting for 40-60% of the crystals (wt) respectively 80% 88% 85% 67% Angle of repose 38° 20° 25° 45° Bulk density (g/mL) 1.35 1.8 1.7 1.2 Mass percentage of LiPF.sub.6 99.99% 99.995% 99.995% 99.89% Yield 99.6% 99.8% 99.85% 98% Insoluble substances (ppm) 70 18 20 200 Free acid (calculated as HF) (ppm) 20 5 5 100 Capacity retention rate for 500 cycles 89.32% 90.12% 90.02% 88.16 Capacity retention rate under 6C high-rate charge-discharge conditions 92.51% 93.91% 93.61% 89.56

Example 4.1

[0220] Referring to FIG. 1, the water content in anhydrous HF was reduced to 8 ppm using the F2 foaming method. The foaming time was 2 hours, the temperature was -20° C., and the F2 flow was 20 g/hr. PC15 was transported to a PF5 generator 2 with a cooling jacket that stored anhydrous HF through a solid conveyor 1 with a metering device, and the temperature was controlled to be about 0° C. PCl5 reacted with anhydrous HF to produce PF5 and HCl. The mixed gas PF5, HCl and entrained HF gas were introduced into a first microchannel reactor 3 to form a first feed stream. In the dissolution tank with cooling jacket and stirrer, HF was added, and LiF was added into the dissolution tank with a solid feeding device while cooling, and the dissolution temperature was controlled at about 0° C., and the mass fraction of LiF to be 3 wt%. The HF solution with dissolved LiF was pumped into the first microchannel reactor 3 to form a second feed stream. The reaction temperature of the first microchannel reactor 3 was 5° C., and the residence time was 10 seconds. The gas- liquid mixture material from the first microchannel reactor 3 entered the first gas-liquid separator 4, and the liquid in the first gas-liquid separator 4 was transported to the synthetic liquid tank 5 for storage, and the gases separated by the first gas-liquid separator included unreacted PF5, HCl and entrained HF. The mixed gas was transported to the second microchannel reactor 6 to react with the third feed stream containing LiPF.sub.6, LiF and HF. The reaction temperature of the second microchannel reactor 6 was 5° C., and the residence time was 10 seconds. The gas-liquid mixture in the second microchannel reactor entered the second gas-liquid separator 7, and the gas separated by the second gas-liquid separator 7 contained HCl and entrained HF, and the mixed gas entered a HF and HCl separation system 8 through a pressurized device. The liquid separated by the second gas-liquid separator 7 contained LiPF.sub.6 in the original mother liquor, LiPF.sub.6 produced by the new reaction and LiF that was not reacted completely. The mixed liquid was transported to the first microchannel reactor 3 as a fourth feed stream. The synthetic liquid in the synthetic liquid tank 5 was transported to a crystallization tank 9 for crystallization of LiPF.sub.6, and LiPF.sub.6 was crystallized in a cooling state. In the crystallization tank 9, the cooling rate of the synthetic liquid was 2° C./h, the stirring rate of the stirrer was 50 rpm, the synthetic liquid was cooled from 25° C. to -45° C., and kept for 6 hours after cooled to -45° C. Then drying and acid removal was carried out in the drying system 10 after solid crystallization and filtration, to obtain a LiPF.sub.6 crystal. The filtered mother liquor was stored in the mother liquor tank 11. After the content of LiPF.sub.6 in mother liquor in mother liquor tank 11 was determined quantitatively, the mother liquor was conveyed to the LiF dissolution tank 12 for the preparation of quantitative LiF solution. The HF solution containing LiPF.sub.6 dissolved a certain amount of LiF and was transported to the second microchannel reactor 6 for reaction to form the third feed stream. The molar ratio of PF5 to LiF in the first microchannel reactor was 2:1, and the molar ratio of PF5 to LiF in the second microchannel reactor was 1:1.

[0221] After testing, in the resulting composition, the content of LiPF.sub.6 crystal was 99.995%, the yield was 99.8%, the particle size of 41% crystals was greater than or equal to 0.2 mm and less than 0.25 mm, and the particle size of 42% crystals was greater than or equal to 0.25 mm and less than or equal to 0.3 mm, the water content was 3 ppm. The water content was determined by the method specified in GB/T 19282-2014.

Example 4.2

[0222] The production process of this example different from Example 4.1 was as follows: Heat treatment was performed after drying and acid removal in the drying system, and the dried product was supplied to a heating furnace. The interior of the heating furnace was vacuumized and sealed with PF5 gas, the heating time was 2 hours, the temperature was 98° C., the pressure was atmospheric pressure, after cooled to room temperature, the interior of the container was vacuumized to obtain the composition. After testing, in the generated composition, the content of the LiPF.sub.6 crystal was 99.9952%, the water content was 2 ppm, the particle size of 45% crystals was greater than or equal to 0.2 mm and less than 0.25 mm, and the particle size of 45% crystals was greater than or equal to 0.25 mm and less than or equal to 0.3 mm.

Comparative Example 4.1

[0223] The production process of this comparative example different from Example 4.1 was as follows: the first feed stream introducing into the first microchannel reactor was purified PF5 gas. No second microchannel reactor was set. The molar ratio of PF5 to LiF in the first microchannel reactor was 1.5:1. After testing, in the resulting composition, the content of the LiPF.sub.6 crystal was 99.88%, the yield was 98.5%, the particle size of 34% crystals was greater than or equal to 0.2 mm and less than 0.25 mm, and the particle size of 29% crystals was greater than or equal to 0.25 mm and less than or equal to 0.3 mm. The water content was 9 ppm.

Comparative Example 4.2

[0224] The production process of this comparative example different from Example 4.1 was as follows: the first and second microchannel reactors were replaced by the first and second reactors, respectively. After being replaced with reactors, for batch production, the reaction time of the first and second reactors increased to 8 hours.

[0225] After testing, in the resulting composition, the content of the LiPF.sub.6 crystal was 99.75%, the yield was 96.1%, the particle size of 31% crystals was greater than or equal to 0.2 mm and less than 0.25 mm, and the particle size of 23% crystals was greater than or equal to 0.25 mm and less than or equal to 0.3 mm. The water content was 10 ppm.

Instructions for Examples 5.1 to 5.14

[0226] The preparation method of LiPF.sub.6 mixture crystal used in Examples 5.1 to 5.14:

[0227] PC15 was transported to a PF5 generator with a cooling jacket that stored HF through a solid conveyor with a metering device, and the temperature was controlled to be about 0° C. PC15 reacted with HF to produce PF5 and HCl. The mixed gas PF5, HCl and entrained HF gas were introduced into a first microchannel reactor to form a first feed stream. In the dissolution tank with cooling jacket and stirrer, HF was added, and LiF was added into the dissolution tank with a solid feeding device while cooling, and the dissolution temperature was controlled at about 0° C., and the mass fraction of LiF to be 2 wt%. The HF solution with dissolved LiF was pumped into the first microchannel reactor to form a second feed stream. The reaction temperature of the first microchannel reactor was 3° C., and the residence time was 5 seconds. The gas- liquid mixture material from the first microchannel reactor entered the first gas-liquid separator, and the liquid in the first gas-liquid separator was transported to the synthetic liquid tank for storage, and the gases separated by the first gas-liquid separator included unreacted PF5, HCl and entrained HF. The mixed gas was transported to the second microchannel reactor to react with the third feed stream containing LiPF.sub.6, LiF and HF. The reaction temperature of the second microchannel reactor was 3° C., and the residence time was 5 seconds. The gas-liquid mixture in the second microchannel reactor entered the second gas-liquid separator, and the gas separated by the second gas-liquid separator contained HCl and entrained HF, and the mixed gas entered a HF and HCl separation system through a pressurized device. The liquid separated by the second gas-liquid separator contained LiPF.sub.6 in the original mother liquor, LiPF.sub.6 produced by the new reaction and LiF that was not reacted completely. The mixed liquid was transported to the first microchannel reactor as a fourth feed stream. The synthetic liquid in the synthetic liquid tank was transported to a crystallization tank for crystallization of LiPF.sub.6, and LiPF.sub.6 was crystallized in a cooling state. In the crystallization tank, the cooling rate of the synthetic liquid was 2° C./h, the stirring rate of the stirrer was 50 rpm, the synthetic liquid was cooled from 20° C. to -45° C., and kept for 6 hours after cooled to -45° C. Then drying and acid removal was carried out in the drying system after solid crystallization and filtration, to obtain a LiPF.sub.6 crystal. The filtered mother liquor was stored in the mother liquor tank. After the content of LiPF.sub.6 in mother liquor in mother liquor tank was determined quantitatively, the mother liquor was conveyed to the LiF dissolution tank for the preparation of quantitative LiF solution. The HF solution containing LiPF.sub.6 dissolved a certain amount of LiF and was transported to the second microchannel reactor for reaction to form the third feed stream. The molar ratio of PF5 to LiF in the first microchannel reactor was 2:1, and the molar ratio of PF5 to LiF in the second microchannel reactor was 1:1.

Example 5.1

[0228] The LiPF.sub.6 mixture crystal was added to the organic solvent of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in a volume ratio of 2:4:4; in the prepared non-aqueous electrolyte solution, the concentration of LiPF.sub.6 was 1.2 mol/L, after mixed and dissolved, the aspect ratio of the LiPF.sub.6 mixture crystal was 1-1.5, the average particle size was 0.2 mm, and among the 80% (wt) of the crystal particles, the family of crystal planes{110} accounted for 40-60%, and the family of crystal planes{111} accounted for 40-60%;among 91% (wt) of the crystal particles, the family of crystal planes{110} accounted for 20-80%, the family of crystal planes{111} accounted for 20-80%, and the average particle size of 82% (wt) of the mixture crystal was 0.2-0.3 mm, the average particle size of 91% (wt) of the mixture crystal was 0.18-0.35 mm; the angle of repose of the mixture crystal was 38°, the bulk density was 1.35 g/mL, the mass percentage of LiPF.sub.6 in the mixture crystal was 99.99%; relative to 100% (wt) of the electrolyte solution, the additive was added in an amount of 2% (wt). The additives were lithium difluorophosphate, lithium bis (trifluoromethanesulphonyl) imide and fluorocarbonate, and the weight ratio thereof was 1:1:3, wherein fluorocarbonate was a mixture of fluoroethylene carbonate and trifluoropropylene carbonate in a weight ratio of 1:2, which was used to prepare a non-aqueous electrolyte solution for secondary batteries.

Example 5.2

[0229] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the organic solvent was ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1:4.

Example 5.3

[0230] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that no additive was used.

Example 5.4

[0231] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the amount of the additive was 5%.

Example 5.5

[0232] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the additive was lithium difluorophosphate.

Example 5.6

[0233] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the additives were lithium difluorophosphate and lithium bis(trifluoromethanesulphonyl)imide in a weight ratio of 1:1.

Example 5.7

[0234] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the additives were lithium difluorophosphate, lithium bis(trifluoromethanesulphonyl)imide, fluorocarbonate and bis(4-fluorophenyl) sulfone in a weight ratio of 1: 1:3:0.5.

Example 5.8

[0235] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the additives were lithium difluorophosphate, lithium bis(trifluoromethanesulphonyl)imide, fluorocarbonate and LiF in a weight ratio of 1:1:3:0.5.

Example 5.9

[0236] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the additives were lithium difluorophosphate, lithium bis(trifluoromethanesulphonyl)imide, fluorocarbonate, bis(4-fluorophenyl) sulfone and LiF in a weight ratio of 1:1:3:0.5:0.5.

Example 5.10

[0237] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the fluorocarbonate was fluoroethylene carbonate.

Example 5.11

[0238] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the organic solvents were propylene carbonate, vinylene carbonate, methyl propyl carbonate, dipropyl carbonate in a volume ratio of 1:2:1.1:2.5, and the concentration of LiPF.sub.6 was 0.9 mol/L.

Example 5.12

[0239] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the volume ratio of ethylene carbonate, vinylene carbonate, ethyl methyl carbonate and diethyl carbonate was 1:1:6:6.

Example 5.13

[0240] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the concentration of LiPF.sub.6 was 1.4 mol/L.

Example 5.14

[0241] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the concentration of LiPF.sub.6 was 1.6 mol/L.

Comparative Example 5.1

[0242] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1, except that the amount of the additive was 6%.

Comparative Example 5.2

[0243] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1. The difference was that the aspect ratio of the LiPF.sub.6 mixture crystal was 0.7-1.3, the average particle size was 0.2 mm, and among 70% (wt) of the crystal particles, the family of crystal planes {110} accounted for 40-60%, the family of crystal planes{111} accounted for 40-60%; among 80% (wt) of the crystal particles, the family of crystal planes{110} accounted for 20-80%, the family of crystal planes{111} accounted for 20-80%, and the average particle size of 45%(wt) of the mixture crystal was 0.2-0.3 mm, the average particle size of 62%(wt) of the mixture crystal was 0.18-0.35 mm, and the angle of repose of the mixture crystal was 18°, the bulk density was 1.3 g/mL.

Comparative Example 5.3

[0244] The non-aqueous electrolyte solution was prepared according to the steps and conditions of Example 5.1. The difference was that the aspect ratio of the LiPF.sub.6 mixture crystal was 0.6-0.9, the average particle size was 0.11 mm, and among 55% (wt) of the crystal particles, the family of crystal planes {110} accounted for 40-60%, the family of crystal planes{111} accounted for 40-60%; among 70% (wt) of the crystal particles, the family of crystal planes{110} accounted for 20-80%, the family of crystal planes{111} accounted for 20-80%, and the average particle size of 35%(wt) of the mixture crystal was 0.2-0.3 mm, the average particle size of 50%(wt) of the mixture crystal was 0.18-0.35 mm, and the angle of repose of the mixture crystal was 15°, the bulk density was 1.2 g/mL.

[0245] The secondary lithium batteries in Examples 5.1 to 5.14 and Comparative Examples 5.1 to 5.3 were prepared as follows.

Preparation of Positive Electrode Sheet

[0246] The lithium nickel-cobalt-manganese ternary material LiNi0.5Co0.2Mn0.3O2, the binder polyvinylidene fluoride and the conductive agent acetylene black were mixed in a mass ratio of 97:1.5:2, and N-methylpyrrolidone (NMP) was added to mix and stir evenly, to obtain positive electrode slurry; the positive electrode slurry was uniformly coated on the aluminum foil, positive electrode current collector, with a thickness of 14 .Math.m; the aluminum foil was dried at room temperature and baked to dryness, and then cold-pressed and cut to obtain a positive electrode sheet.

Preparation of Negative Electrode Sheet

[0247] The negative electrode active materials (artificial graphite, carbon black, and the binder polyvinylidene fluoride) were mixed in a mass ratio of 98:1:1, and N-methylpyrrolidone (NMP) was added to mix and stir evenly, to obtain negative electrode slurry. The slurry was uniformly coated on the copper foil, negative electrode current collector, with a thickness of 8 .Math.m; the copper foil is dried at room temperature and baked to dryness, and then cold-pressed and cut to obtain a negative electrode sheet.

Preparation of Separator

[0248] Polyethylene with a thickness of 12 .Math.m was used as a separator.

Preparation of Secondary Lithium Battery

[0249] The positive electrode sheet, separator, and negative electrode sheet were stacked in sequence, and then rolled into a square bare battery cell, put into aluminum plastic film, then dried, injected with corresponding electrolyte solution and sealed, after the processes of standing, hot and cold pressing, pre-forming, clamping and divided capacity, etc., the secondary lithium battery was obtained.

Test Example

[0250] In the following test examples, the performance of batteries prepared in Example 5.1 to 5.14 and Comparative Example 5.1 to 5.3 was tested. Results were shown in Table 3.

High Temperature Storage Performance Test of Secondary Lithium Battery

[0251] At room temperature of 25° C., the secondary lithium battery was charged with a constant current of 1 C to a voltage of 4.2 V, further charged with a constant voltage of 4.2 V to a current of 0.05 C, allowed to standing for 10 minutes, then discharged with a constant current of 1 C to a voltage of 2.75 V to measure the initial discharge capacity. After that, the secondary battery was charged to a voltage of 4.2 V at a room temperature of 25° C. with a constant current of 1 C, further charged with a constant voltage of 4.2 V until a current of 0.05 C, and then stored at 60° C. for 4 weeks. Subsequently, it was charged with a constant current of 1 C to a voltage of 4.2 V, further charged with a constant voltage of 4.2 V to a current of 0.05 C, allowed to standing for 10 minutes, then discharged with a constant current of 1 C to a voltage of 2.75 V, to measure the discharge capacity after storage, and calculate the capacity retention rate.

[0252] Capacity retention rate (%)=[Discharge capacity after 4 weeks of storage/initial discharge capacity] × 100.

High Temperature Cycle Performance Test of Secondary Lithium Battery

[0253] At 60° C., the secondary lithium battery was charged with a constant current of 1 C to a voltage of 4.2 V, further charged with a constant voltage of 4.2 V to a current of 0.05 C, allowed to standing for 10 minutes, then discharged with a constant current of 1 C to 2.75 V; this was a charge-discharge cycle process. The discharge capacity this time was the initial discharge capacity of the secondary lithium battery. The secondary lithium battery was subjected to 500-cycle charging/discharging test according to the above method, to obtain the capacity retention rate after 500 cycles at 60° C.

[0254] Capacity retention rate (%)=(Discharge capacity after 500 cycles/Initial discharge capacity)× 100%.

High-Rate Charging Performance Test of Secondary Lithium Battery

[0255] At room temperature of 25° C., the secondary lithium battery was charged with a constant current rate of 1 C to a voltage of 2.75 V, after standing for 10 minutes, charged to 4.2 V with a constant current rate of 0.5 C, after standing for 10 minutes, discharged to 2.75 V with a constant current rate of 1 C, to obtain the charging capacity under 0.5 C rate charging.

[0256] At 25° C., the secondary lithium battery was charged with a constant current rate of 1 C to a voltage of 2.75 V, after standing for 10 minutes, charged to 4.2 V with a constant current rate of 5 C, after standing for 10 minutes, discharged to 2.75 V with a constant current rate of 1 C, to obtain the charging capacity under 5 C rate charging.

[0257] The charging capacity ratio (%) of the secondary lithium battery under 5 C rate charging = Charging capacity under 5 C rate charging /Charging capacity under 0.5 C rate charging × 100%.

Low-Temperature Discharge Performance Test of Secondary Lithium Battery

[0258] At 25° C., the secondary lithium battery was charged with a constant current of 1 C to a voltage of 4.2 V, further charged with a constant voltage of 4.2 V to a current of 0.05 C, allowed to standing for 10 minutes, after standing for 4 h under different temperatures (25° C., 0° C., -10° C.), discharged with a constant current of 1 C to 2.75 V; after the end of discharging, allowed to standing for 5 minutes, and the discharge capacity of the secondary lithium battery was recorded at this time.

[0259] Discharge capacity ratio (%) of the secondary lithium battery at different temperatures = (Discharge capacity at 0° C., -10° C.)/(Discharge capacity at 25° C.) × 100%.

[0260] Table 3 showed the performance test results of Example 5.1to 5.14 and Comparative Example 5.1 to 5.3.

TABLE-US-00003 Capacity retention rate/% after 4 weeks of storage at 60° C. Capacity retention rate after 500 cycles at 60° C./% Charge capacity ratio under 5 C rate charging/% Discharge capacity ratio at different temperatures 0° C. -10° C. Example 5.1 97.33% 91.67% 90.67% 94.12% 82.32% Example 5.2 91.21% 87.45% 87.59% 89.67% 77.54% Example 5.3 90.15% 85.79% 84.24% 86.54% 76.66% Example 5.4 95.35% 90.64% 89.36% 92.67% 80.95% Example 5.5 91.57% 87.96% 85.95% 87.36% 77.82% Example 5.6 94.54% 89.01% 88.01% 91.37% 81.21% Example 5.7 98.42% 92.62% 91.43% 95.14% 83.54% Example 5.8 98.22% 92.72% 91.55% 95.47% 83.68% Example 5.9 98.97% 93.01% 92.11% 96.34% 84.78% Example 5.10 95.42% 90.21% 88.56% 92.01% 80.95% Example 5.11 96.84% 91.54% 90.63% 93.67% 82.24% Example 5.12 94.36% 89.64 86.56% 89.12% 80.32% Example 5.13 96.89% 92.01% 89.67% 92.86% 81.88% Example 5.14 93.11% 89.21% 86.76% 90.36% 79.42% Comparative Example 5.1 78.67% 79.23% 75.33% 80.45% 70.21% Comparative Example 5.2 80.15% 78.35% 79.43% 77.64% 71.06% Comparative Example 5.3 70.31% 68.54% 69.65% 70.52% 60.85%

[0261] As shown in the above Table 3, the lithium battery prepared by using the LiPF.sub.6 mixture crystal of the present invention as a non-aqueous electrolyte solution of lithium salt had excellent high-temperature cycle performance, high-temperature storage performance, low-temperature discharge performance, and high-rate charging performance. By adding the specific additive and organic solvent of the present invention, the above performance of the secondary lithium battery was obviously improved.

Instructions of Examples 6.1 to 6.3

[0262] The LiPF.sub.6used in Examples 6.1 to 6.3 of the present invention was prepared in Example 4.1.

Example 6.1

[0263] A fluorine-containing electrolyte solution comprised LiPF.sub.6, LiPO.sub.2F.sub.2, LiBF.sub.2C.sub.2O.sub.4, ethylene carbonate, ethyl methyl carbonate and diethyl carbonate. The purity of LiPF.sub.6 used in the preparation of the electrolyte solution was 99.995 wt%, the water content was 3 ppm, 41% of the crystal particle size was greater than or equal to 0.2 mm and less than 0.25 mm, and 42% of the crystal particle size was greater than or equal to 0.25 mm and less than or equal to 0.3 mm. The water content was determined by the method in GB/T 19282-2014. In the fluorine-containing electrolyte solution, the mass fraction of LiPF.sub.6 was 18 wt%, the mass fraction of LiPO.sub.2F.sub.2 was 1 wt%, the mass fraction of LiBF.sub.2C.sub.2O.sub.4 was 1 wt%, the mass fraction of ethylene carbonate was 24 wt%, the mass fraction of ethyl methyl carbonate was 41 wt%, and the mass fraction of diethyl carbonate was 15 wt%.

[0264] After testing, the conductivity of fluorine-containing electrolyte solution was 10.07 mS/cm at 25° C. The capacity retention rate of the assembled LiCoO2/graphite full battery after 500 cycles under 0.5 C rate at a cut-off voltage of 3.0-4.4 V was tested at 25° C., and the result was 90.5%.

Example 6.2

[0265] A fluorine-containing electrolyte solution comprised LiPF.sub.6, LiPO.sub.2F.sub.2, LiBF.sub.2C.sub.2O.sub.4, 1,2-Bis(trifluoromethyl)benzene, ethylene carbonate, ethyl methyl carbonate diethyl carbonate. The purity of LiPF.sub.6 used in the preparation of the electrolyte solution was 99.995 wt%, the water content was 3 ppm, 41% of the crystal particle size was greater than or equal to 0.2 mm and less than 0.25 mm, and 42% of the crystal particle size was greater than or equal to 0.25 mm and less than or equal to 0.3 mm. The water content was determined by the method in GB/T 19282-2014. In the fluorine-containing electrolyte solution, the mass fraction of LiPF.sub.6 was 18 wt%, the mass fraction of LiPO.sub.2F.sub.2 was 1 wt%, the mass fraction of LiBF.sub.2C.sub.2O.sub.4 was 1 wt%, the mass fraction of 1,2-Bis(trifluoromethyl)benzene was 3 wt%, the mass fraction of ethylene carbonate was 24 wt%, the mass fraction of ethyl methyl carbonate was 38 wt%, and the mass fraction of diethyl carbonate was15 wt%.

[0266] After testing, the conductivity of fluorine-containing electrolyte solution was 10.42 mS/cm at 25° C. The capacity retention rate of the assembled LiCoO2/graphite full battery after 500 cycles under 0.5 C rate at a cut-off voltage of 3.0-4.4 V was tested at 25° C., and the result was 91.6%.

Example 6.3

[0267] A fluorine-containing electrolyte solution comprised LiPF.sub.6, LiPO.sub.2F.sub.2, LiBF.sub.2C.sub.2O.sub.4, 1,2-Bis(trifluoromethyl)benzene, ethylene carbonate, ethyl methyl carbonate, diethyl carbonate, diethyl ether, trifluoromethyl ethyl sulfone. The purity of LiPF.sub.6 used in the preparation of the electrolyte solution was 99.995 wt%, the water content was 3 ppm, 41% of the crystal particle size was greater than or equal to 0.2 mm and less than 0.25 mm, and 42% of the crystal particle size was greater than or equal to 0.25 mm and less than or equal to 0.3 mm. The water content was determined by the method in GB/T 19282-2014. In the fluorine-containing electrolyte solution, the mass fraction of LiPF.sub.6 was 12 wt%, the mass fraction of LiPO.sub.2F.sub.2 was 3 wt%, the mass fraction of LiBF.sub.2C.sub.2O.sub.4 was 2 wt%, the mass fraction of 1,2-Bis(trifluoromethyl)benzene was 2 wt%, the mass fraction of ethylene carbonate was 20 wt%, the mass fraction of ethyl methyl carbonate was 38 wt%, and the mass fraction of diethyl carbonate was 13 wt%, the mass fraction of diethyl ether was 5 wt%, the mass fraction of trifluoromethyl ethyl sulfone was 5 wt%.

[0268] After testing, the conductivity of fluorine-containing electrolyte solution was 10.85 mS/cm at 25° C. The capacity retention rate of the assembled LiCoO2/graphite full battery after 500 cycles under 0.5 C rate at a cut-off voltage of 3.0-4.4 V was tested at 25° C., and the result was 92.8%.

Comparative Example 6.1

[0269] The differences between this comparative example and Example 6.1 were as follows: the purity of LiPF.sub.6 used in the preparation of the electrolyte solution was 99.89 wt%, the water content was 20 ppm, 28% of the crystal particle size was greater than or equal to 0.2 mm and less than 0.25 mm, 23% of the crystal particle size was greater than or equal to 0.25 mm and less than or equal to 0.3 mm. The water content was determined by the method in GB/T 19282-2014.

[0270] After testing, the conductivity of fluorine-containing electrolyte solution was 8.77 mS/cm at 25° C. The capacity retention rate of the assembled LiCoO2/graphite full battery after 500 cycles under 0.5 C rate at a cut-off voltage of 3.0-4.4 V was tested at 25° C., and the result was 86.5%.

Comparative Example 6.2

[0271] The difference between this comparative example and Example 6.1 was as follows: 1,2-Bis(trifluoromethyl)benzene was replaced by benzotrifluoride. After testing, the conductivity of fluorine-containing electrolyte solution was 9.56 mS/cm at 25° C. The capacity retention rate of the assembled LiCoO2/graphite full battery after 500 cycles under 0.5 C rate at a cut-off voltage of 3.0-4.4 V was tested at 25° C., and the result was 88.6%.