METHOD FOR PREPARING SILICON-CARBON COMPOSITE ANODE MATERIAL AND USE THEREOF

Abstract

The present disclosure discloses a preparation method for a silicon/carbon composite anode material and use of thereof. The preparation method includes the following steps: heating a hypercrosslinked polymer in an inert atmosphere for carbonization to obtain a porous carbide; mixing the porous carbide with a silicon-containing solution to obtain a silicon-containing porous carbide suspension; and adding a complexing agent, a metal salt, and a reducing agent to the silicon-containing porous carbide suspension to allow a reaction, and after the reaction is completed, conducting solid-liquid separation to obtain a solid, and heating the solid in an inert atmosphere to obtain the silicon/carbon composite anode material. In the present disclosure, the metal salt is reduced with the reducing agent under an action of the complexing agent through a metal-embedded-into-silicon treatment, such that a metal layer is formed on a silicon layer adsorbed on the porous carbide.

Claims

1. A preparation method for a silicon/carbon composite anode material, comprising the following steps: S1: heating a hypercrosslinked polymer in an inert atmosphere for carbonization to obtain a porous carbide; S2: mixing the porous carbide with a silicon-containing solution to obtain a silicon-containing porous carbide suspension; and S3: adding a complexing agent, a metal salt, and a reducing agent to the silicon-containing porous carbide suspension to allow a reaction, and after the reaction is completed, conducting solid-liquid separation to obtain a solid, and heating the solid in an inert atmosphere to obtain the silicon/carbon composite anode material.

2. The preparation method according to claim 1, wherein the step S1 further comprises preparation of the hypercrosslinked polymer which comprises: in an inert atmosphere, mixing a benzenediol compound, a solvent, and a crosslinking agent, after cooling, adding a catalyst and mixing, and heating a resulting mixture to allow a reaction to obtain the hypercrosslinked polymer.

3. The preparation method according to claim 1, wherein in step S1, the heating for carbonization is conducted as follows: heating at a temperature from 100 C. to 320 C. for 0.1 h to 3 h, and then heating at a temperature from 600 C. to 1,000 C. for 8 h to 24 h, during the heating for carbonization, an inert gas is introduced to allow pore-expansion treatment under an action of gas flow.

4. The preparation method according to claim 1, wherein in step S1, the porous carbide has a particle size D50 of 2 m to 26 m and a specific surface area of 200 m.sup.2/g to 350 m.sup.2/g.

5. The preparation method according to claim 1, wherein in step S2, the silicon-containing solution is a nano-silicon oxide suspension or a nano-silicon suspension, and a mass percentage of silicon in the silicon-containing solution is in a range from 0.001 to 0.75.

6. The preparation method according to claim 1, wherein in step S3, the complexing agent is at least one selected from the group consisting of potassium sodium tartrate, ethylene diamine tetraacetic acid, and tartaric acid.

7. The preparation method according to claim 1, wherein in step S3, the metal salt is at least one selected from the group consisting of a soluble sulfate, a soluble chloride, a soluble nitrate, a soluble bromide, and a soluble phosphate of copper or silver; and the reducing agent is at least one selected from the group consisting of hypophosphorous acid and sodium hypophosphite.

8. The preparation method according to claim 1, wherein in step S3, the heating is conducted at a temperature from 550 C. to 1,100 C. for 1 h to 5 h.

9. The preparation method according to claim 1, wherein in step S3, the silicon/carbon composite anode material has a particle size D50 of 0.5 m to 23 m.

10. Use of the preparation method according to claim 1 in preparation of a lithium-ion battery.

11. Use of the preparation method according to claim 2 in preparation of a lithium-ion battery.

12. Use of the preparation method according to claim 3 in preparation of a lithium-ion battery.

13. Use of the preparation method according to claim 4 in preparation of a lithium-ion battery.

14. Use of the preparation method according to claim 5 in preparation of a lithium-ion battery.

15. Use of the preparation method according to claim 6 in preparation of a lithium-ion battery.

16. Use of the preparation method according to claim 7 in preparation of a lithium-ion battery.

17. Use of the preparation method according to claim 8 in preparation of a lithium-ion battery.

18. Use of the preparation method according to claim 9 in preparation of a lithium-ion battery.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present disclosure is further described below with reference to accompanying drawings and examples, in which,

[0031] FIG. 1 is a scanning electron microscopy (SEM) image of the silicon/carbon composite anode material according to Example 1 of the present disclosure.

DETAILED DESCRIPTION

[0032] The concepts and technical effects of the present disclosure are clearly and completely described below in conjunction with examples, such as to allow the objectives, features and effects of the present disclosure to be fully understood. Apparently, the described examples are merely some rather than all of the examples of the present disclosure. All other examples obtained by those skilled in the art based on the examples of the present disclosure without creative efforts should fall within the protection scope of the present disclosure.

Example 1

[0033] In this example, a silicon/carbon composite anode material was prepared, and a specific preparation process was as follows:

[0034] 1. p-Benzenedimethanol (100 g), tetrachloromethane, ferric chloride, and dimethoxymethane were weighed out according to a ratio of 5 g:15 mL:2 g:1.2 mL; and the p-benzenedimethanol, tetrachloromethane, and dimethoxymethane were mixed and stirred for 2 h in a vessel with a nitrogen atmosphere and then cooled for 0.5 h in an ice water bath at 2 C., then the weighed ferric chloride was added, and a resulting mixture was further stirred for 6 h to obtain a homogeneous mixture.

[0035] 2. The homogeneous mixture was heated for a reaction at 75 C. for 3 h to obtain an hypercrosslinked polymer, and the hypercrosslinked polymer was washed repeatedly with a mixed solution of ethanol and water to remove excess tetrachloromethane and ferric chloride; the vessel containing the hypercrosslinked polymer was transferred to a heating device, and the hypercrosslinked polymer was subjected to first-stage heating at 110 C. for 3 h and then to second-stage heating at 865 C. for 15 h, nitrogen was introduced during heating such that a pore-expansion treatment was allowed under an action of gas flow (0.01 m.sup.3/min) to obtain a porous carbide; and the porous carbide was subjected to ball-milling in a ball mill to obtain a porous carbide material with a particle size D50 of about 6.3 m.

[0036] 3.80 g of the porous carbide material obtained after the ball-milling in step 2 was mixed with 100 mL of a nano-silica suspension for 5 h (a particle size of nano-silica being about 40 nm, and a mass percentage of silicon in the nano-silica suspension being 0.13) to obtain a silicon-containing porous carbide suspension; and a half of the silicon-containing porous carbide suspension was not further treated, i.e., it was not subjected to metal-embedded treatment, rather allowed to stand for 3 h, and subjected to solid-liquid separation to obtain a solid, and the solid was heated at 845 C. for 3 h in an argon atmosphere to obtain a silicon-containing porous carbide with a mass percentage of silicon of 0.07.

[0037] 4. The other half of the silicon-containing porous carbide suspension, ethylene diamine tetraacetic acid, copper sulfate, and hypophosphorous acid were mixed (a mass ratio of ethylene diamine tetraacetic acid to copper sulfate to hypophosphorous acid added into the other half of the silicon-containing porous carbide suspension being 1.2:1.7:12, and a mass ratio of the copper sulfate to silicon in the silicon-containing porous carbide suspension being 0.2:3), and a resulting mixture was stirred at 75 C. to allow a reaction; after the reaction was completed, a reaction system was allowed to stand for 3 h and subjected to solid-liquid separation, and a resulting solid was washed to remove impurities and then heated at 845 C. for 3 h in an argon atmosphere to obtain a porous carbide with a silicon-copper alloy; and the porous carbide with the silicon-copper alloy was subjected to ball-milling (D50 controlled at about 6.5 m) and demagnetization to obtain the silicon/carbon composite anode material, with mass percentages of silicon and copper of 0.07 and 0.004, respectively.

Example 2

[0038] In this example, a silicon/carbon composite anode material was prepared, and a specific preparation process was as follows:

[0039] 1. p-Benzenedimethanol (100 g), tetrachloromethane, ferric chloride, and dimethoxymethane were weighed out according to a ratio of 6 g:20 mL:2.7 g:1.5 mL; and the p-benzenedimethanol, tetrachloromethane, and dimethoxymethane were mixed and stirred for 2 h in a vessel with a nitrogen atmosphere and then cooled for 0.5 h in an ice water bath at 2 C., then the weighed ferric chloride was added, and a resulting mixture was further stirred for 6 h to obtain a homogeneous mixture.

[0040] 2. The homogeneous mixture was heated for a reaction at 75 C. for 3 h to obtain an hypercrosslinked polymer, and the hypercrosslinked polymer was washed repeatedly with a mixed solution of ethanol and water to remove excess tetrachloromethane and ferric chloride; the vessel containing the hypercrosslinked polymer was transferred to a heating device, and the hypercrosslinked polymer was subjected to first-stage heating at 110 C. for 2 h and then to second-stage heating at 865 C. for 15 h, nitrogen was introduced during heating such that a pore-expansion treatment was allowed under an action of gas flow (0.01 m.sup.3/min) to obtain a porous carbide; and the porous carbide was subjected to ball-milling in a ball mill to obtain a porous carbide material with a particle size D50 of about 5.3 m.

[0041] 3. 80 g of the porous carbide material obtained after the ball-milling in step 2 was mixed with 100 mL of a nano-silica suspension for 5 h (a particle size of nano-silica being about 40 nm, and a mass percentage of silicon in the nano-silica suspension being 0.13) to obtain a silicon-containing porous carbide suspension; and a half of the silicon-containing porous carbide suspension was not further treated, i.e., it was not subjected to metal-embedded treatment, rather allowed to stand for 3 h, and subjected to solid-liquid separation to obtain a solid, and the solid was heated at 870 C. for 3 h in an argon atmosphere to obtain a silicon-containing porous carbide, with a mass percentage of silicon of 0.11.

[0042] 4. The other half of the silicon-containing porous carbide suspension, ethylene diamine tetraacetic acid, copper sulfate, and hypophosphorous acid were mixed (a mass ratio of ethylene diamine tetraacetic acid to copper sulfate to hypophosphorous acid added into the other half of the silicon-containing porous carbide suspension being 1.6:2.3:22, and a mass ratio of the copper sulfate to silicon in the silicon-containing porous carbide suspension being 0.27:3), and a resulting mixture was stirred at 75 C. to allow a reaction; after the reaction was completed, a reaction system was allowed to stand for 3 h and subjected to solid-liquid separation, and a resulting solid was washed to remove impurities and then heated at 870 C. for 3 h in an argon atmosphere to obtain a porous carbide with a silicon-copper alloy; and the porous carbide with the silicon-copper alloy was subjected to ball-milling (D50 controlled at about 5.9 m) and demagnetization to obtain the silicon/carbon composite anode material, with mass percentages of silicon and copper of 0.11 and 0.007, respectively.

Example 3

[0043] In this example, a silicon/carbon composite anode material was prepared, and a specific preparation process was as follows:

[0044] 1. p-Benzenedimethanol (100 g), tetrachloromethane, ferric chloride, and dimethoxymethane were weighed out according to a ratio of 6 g:20 mL:2.7 g:1.5 mL; and the p-benzenedimethanol, tetrachloromethane, and dimethoxymethane were mixed and stirred for 2 h in a vessel with a nitrogen atmosphere and then cooled for 0.5 h in an ice water bath at 2 C., then the weighed ferric chloride was added, and a resulting mixture was further stirred for 6 h to obtain a homogeneous mixture.

[0045] 2. The homogeneous mixture was heated for a reaction at 75 C. for 3 h to obtain an hypercrosslinked polymer, and the hypercrosslinked polymer was washed repeatedly with a mixed solution of ethanol and water to remove excess tetrachloromethane and ferric chloride; the vessel containing the hypercrosslinked polymer was transferred to a heating device, and the hypercrosslinked polymer was subjected to first-stage heating at 110 C. for 2 h and then to second-stage heating at 865 C. for 15 h, neon was introduced during heating such that a pore-expansion treatment was allowed under an action of gas flow (0.015 m.sup.3/min) to obtain a porous carbide; and the porous carbide was subjected to ball-milling in a ball mill to obtain a porous carbide material with a particle size D50 of about 5.6 m.

[0046] 3. 80 g of the porous carbide material obtained after the ball-milling in step 2 was mixed with 100 mL of a nano-silica suspension for 5 h (a particle size of nano-silica being about 40 nm, and a mass percentage of silicon in the nano-silica suspension being 0.23) to obtain a silicon-containing porous carbide suspension; and a half of the silicon-containing porous carbide suspension was not further treated, i.e., it was not subjected to metal-embedded treatment, rather allowed to stand for 3 h, and subjected to solid-liquid separation to obtain a solid, and the solid was heated at 960 C. for 2.5 h in an argon atmosphere to obtain a silicon-containing porous carbide with a mass percentage of silicon of 0.14.

[0047] 4. The other half of the silicon-containing porous carbide suspension, ethylene diamine tetraacetic acid, copper sulfate, and hypophosphorous acid were mixed (a mass ratio of ethylene diamine tetraacetic acid to copper sulfate to hypophosphorous acid added into the other half of the silicon-containing porous carbide suspension being 3:3.5:28, and a mass ratio of the copper sulfate to silicon in the silicon-containing porous carbide suspension being 0.3:3), and a resulting mixture was stirred at 75 C. to allow a reaction; after the reaction was completed, a reaction system was allowed to stand for 3 h and subjected to solid-liquid separation, and a resulting solid was washed to remove impurities and then heated at 960 C. for 2.5 h in an argon atmosphere to obtain a porous carbide with a silicon-copper alloy; and the porous carbide with the silicon-copper alloy was subjected to ball-milling (D50 controlled at about 5.1 m) and demagnetization to obtain the silicon/carbon composite anode material, with mass percentages of silicon and copper of 0.14 and 0.006, respectively.

Example 4

[0048] In this example, a silicon/carbon composite anode material was prepared, and a specific preparation process was as follows:

[0049] 1. o-Benzenedimethanol (100 g), tetrachloromethane, ferric chloride, and dimethoxymethane were weighed out according to a ratio of 6 g:40 mL:4.2 g:2.0 mL; and the o-benzenedimethanol, tetrachloromethane, and dimethoxymethane were mixed and stirred for 2 h in a vessel with a nitrogen atmosphere and then cooled for 0.5 h in an ice water bath at 6 C., then the weighed ferric chloride was added, and a resulting mixture was further stirred for 6 h to obtain a homogeneous mixture.

[0050] 2. The homogeneous mixture was heated for a reaction at 75 C. for 3 h to obtain an hypercrosslinked polymer, and the hypercrosslinked polymer was washed repeatedly with a mixed solution of ethanol and water to remove excess tetrachloromethane and ferric chloride; the vessel filled with the hypercrosslinked polymer was transferred to a heating device, and the hypercrosslinked polymer was subjected to first-stage heating at 110 C. for 2 h and then to second-stage heating at 735 C. for 15 h, neon was introduced during heating such that a pore-expansion treatment was allowed under an action of gas flow (0.015 m.sup.3/min) to obtain a porous carbide; and the porous carbide was subjected to ball-milling in a ball mill to obtain a porous carbide material with a particle size D50 of about 3.4 m.

[0051] 3. 80 g of the porous carbide material obtained after the ball-milling in step 2 was mixed with 100 mL of a nano-silica suspension for 5 h (a particle size of nano-silica being about 40 nm, and a mass percentage of silicon in the nano-silica suspension being 0.24) to obtain a silicon-containing porous carbide suspension; and a half of the silicon-containing porous carbide suspension was not further treated, i.e., it was not subjected to metal-embedded treatment, rather allowed to stand for 3 h, and subjected to solid-liquid separation to obtain a solid, and the solid was heated at 960 C. for 2.5 h in an argon atmosphere to obtain a silicon-containing porous carbide with a mass percentage of silicon of 0.15.

[0052] 4. The other half of the silicon-containing porous carbide suspension, potassium sodium tartrate, silver chloride, and hypophosphorous acid were mixed (a mass ratio of potassium sodium tartrate to silver chloride to hypophosphorous acid added into the other half of the silicon-containing porous carbide suspension being 8:3.2:36, and a mass ratio of the silver chloride to silicon in the silicon-containing porous carbide suspension being 0.3:3), and a resulting mixture was stirred at 60 C. to allow a reaction; after the reaction was completed, a reaction system was allowed to stand for 3 h and subjected to solid-liquid separation, and a resulting solid was washed to remove impurities and then heated at 960 C. for 2.5 h in an argon atmosphere to obtain a porous carbide with a silicon-silver alloy; and the porous carbide with a silicon-silver alloy was subjected to ball-milling (D50 controlled at about 3.5 m) and demagnetization to obtain the silicon/carbon composite anode material, with mass percentages of silicon and silver of 0.15 and 0.003, respectively.

Test Example

[0053] 1. The electrical conductivity was tested by the four-point-probe method for the silicon-containing porous carbides and silicon/carbon composite anode materials obtained in Examples 1 to 4, and results were shown in Table 1.

[0054] 2. An anode sheet expansion ratio was calculated according to the following formula: anode sheet expansion ratio=(thickness of an anode sheet fully charged-thickness of the anode sheet being dried)/thickness of the anode sheet being dried*100%, and calculation results were shown in Table 1.

TABLE-US-00001 TABLE 1 Specific surface area, electrical conductivity, and anode sheet expansion ratio of the anode materials Electrical conductivity Anode sheet Specific (S .Math. cm.sup.1) expansion ratio (%) surface Silicon/ Silicon/ area Silicon- carbon Silicon- carbon (m.sup.2/g) containing composite containing composite Porous porous anode porous anode carbide carbide material carbide material Example 1 272.86 0.0033 0.0096 27.1 23.3 Example 2 278.65 0.0028 0.0103 29.4 24.7 Example 3 285.19 0.0023 0.0109 31.2 25.3 Example 4 300.21 0.0012 0.0103 36.4 26.5

[0055] It can be seen from the test results in Table 1 that the porous carbides obtained in step 2 have higher specific surface area, and the silicon/carbon composite anode materials have significantly improved electrical conductivity compared with the materials in which silicon and carbon are not composed. In addition, the silicon/carbon composite anode materials have better expansion ratios during a charge and discharge process than the materials in which silicon and carbon are not composed.

[0056] 3. Electrochemical performance test: An anode sheet of a battery was manufactured by scraping. Each of the silicon-containing porous carbides and silicon/carbon composite anode materials prepared in Examples 1 to 4, a conductive agent SuperP, and polyvinylidene fluoride (PVDF) were weighed out according to a mass ratio of 8:1:1 and mixed thoroughly in N-methylpyrrolidone (NMP) as a solvent, and a resulting mixture was coated on a copper foil with a scraper, then pressed, and dried in a vacuum oven at 80 C. for 3 h; and a coated sheet was punched and cut to a disc with a diameter of 12 mm. In a half cell, a dry electrode sheet was used at an anode side, a lithium sheet was used as a counter electrode at a cathode side, Celgard 2400 was used as a separator, and 1 M LiPF.sub.6 in a mixture of EC, DMC, and DEC (in a volume ratio of 1:1:1) was used as an electrolyte. A CT2001A battery detection system was used to test the prepared half-cell for charge-discharge performance at a voltage in a range from 0.01 V to 2.0 V and a current density of 100 mA/g, and test results were shown in Table 2.

TABLE-US-00002 TABLE 2 Electrochemical performance of anode materials Initial charge specific capacity Capacity retention after 200 cycles (mAh/g) Initial coulombic efficiency (%) (%) Silicon- Silicon/carbon Silicon- Silicon/carbon Silicon- Silicon/carbon containing composite containing composite containing composite porous anode porous anode porous anode carbide material carbide material carbide material Example 1 508.7 523.5 76.3 86.3 71.6 83.1 Example 2 701.8 722.8 75.8 86.8 71.1 83.6 Example 3 795.1 812.6 75.4 87.4 70.7 84.2 Example 4 802.3 835.9 73.9 87.5 69.3 84.3

[0057] It can be seen from the test results in Table 2 that the silicon/carbon composite anode materials are superior to the silicon-containing porous carbides in which silicon and carbon are not composed in terms of the initial charge specific capacity, the coulombic efficiency, and the capacity retention rate after 200 cycles, indicating that the composite metal layer can effectively bear a stress due to a volume change caused by silicon expansion and further reduce a volume effect of a silicon-based anode material during a lithium deintercalation/intercalation process.

[0058] The examples of the present disclosure are described in detail with reference to the accompanying drawings, but the present disclosure is not limited to the above examples. Within the scope of knowledge possessed by those of ordinary skill in the technical field, various changes can also be made without departing from the purpose of the present disclosure. In addition, the examples and features in the examples of the present disclosure may be combined with each other in a non-conflicting situation.