ENVIRONMENT-FRIENDLY PRECURSOR, CATHODE MATERIAL FOR LITHIUM-ION BATTERY, AND PREPARATION METHODS THEREOF

Abstract

The present invention belongs to the field of materials, and relates to an environment-friendly precursor, a cathode material for a lithium-ion battery, and preparation methods thereof. The method for preparing an environment-friendly precursor provided in the present invention includes: subjecting a metal and/or a metal oxide, an oxidant, water, and a complexing agent to a chemical corrosion crystallization reaction at an electrical conductivity equal to or greater than 200 uS/cm, a redox potential ORP value equal to or less than 100 my, and a complexing agent concentration of 3-50 g/L. The precursor prepared by using the method provided in the present invention has advantages that no waste water is produced during dissolution and crystallization, and that water is constantly consumed, so that the purpose of environmental friendliness can be achieved. Moreover, the first charge and discharge efficiency of a lithium-ion battery can be effectively improved by means of the precursor.

Claims

1. A method for preparing a precursor, comprising: subjecting at least one of a metal or a metal oxide, an oxidant, water, and a complexing agent to a chemical corrosion crystallization reaction at an electrical conductivity equal to or greater than 200 uS/cm, a redox potential oxidation/reduction potential (ORP) value equal to or less than 100 my, and a complexing agent concentration of 3-50 g/L, wherein the at least one of the metal or the metal oxide is at least one selected from nickel, cobalt, manganese, aluminum, zirconium, tungsten, magnesium, strontium, and yttrium metal elements and metal oxides thereof; after the reaction is complete, conducting magnetic separation on an obtained reaction product to obtain a magnetic particle and a slurry; then, conducting solid-liquid separation on the slurry to obtain a solid particle and a filtrate; and finally, washing and drying the solid particle to obtain the precursor.

2. The method for preparing a precursor according to claim 1, wherein quantities of the oxidant and the water are such that the at least one of the metal or the metal oxide is converted into a corresponding metal hydroxide.

3. (canceled)

4. The method for preparing a precursor according to claim 1, wherein the at least one of the metal or the metal oxide is Ni—Co—Mn—Zr—W, Ni—Mg—Zr—W, Co—Al—Mg—Ti, or Ni—Co—Al—Zr—Ti.

5. The method for preparing a precursor according to claim 1, wherein the oxidant is at least one selected from nitric acid, oxygen, air, sodium chlorate, potassium permanganate, and hydrogen peroxide.

6. The method for preparing a precursor according to claim 1, wherein the complexing agent is at least one selected from ammonia, ammonium sulfate, ammonium chloride, ethylenediamine tetraacetic acid, and ammonium nitrate.

7. The method for preparing a precursor according to claim 1, wherein the electrical conductivity is 200-50,000 uS/cm.

8. The method for preparing an environment friendly precursor according to claim 1, wherein the electrical conductivity is controlled by adding a salt into a reaction system, and the salt is at least one selected from a sulfate, a chloride, and a nitrate of sodium and lithium.

9. The method for preparing a precursor according to claim 1, wherein the chemical corrosion crystallization reaction is a continuous reaction or an intermittent reaction.

10. The method for preparing a precursor according to claim 1, wherein during the chemical corrosion crystallization reaction, a stirring intensity is determined at an input power of 0.1-1.0 kw/m.sup.2.Math.h, metal ions in a reaction system have a concentration of 1-30 g/L, a pH value is 6-12, and the reaction is carried out at a temperature of 20-90° C. for 10-150 h.

11. The method for preparing a precursor according to claim 1, wherein the magnetic separation is intermittent magnetic separation or continuous magnetic separation at an intensity of 100-5,000 Gas.

12. The method for preparing a precursor according to claim 1, wherein the method further comprises returning all the magnetic particle, the filtrate, and washing water to a chemical corrosion crystallization reaction system, and supplementing water consumed during crystallization.

13. A precursor prepared by the method according to claim 1.

14. A method for preparing a cathode material for a lithium-ion battery, comprising: (1) preparing a precursor by the method according to claim 1; and (2) subjecting the precursor and a lithium source to mixing and calcination to obtain the cathode material for the lithium-ion battery.

15. The method for preparing a cathode material for a lithium-ion battery according to claim 14, wherein in step (2), a Li/Me molar ratio of the precursor to the lithium source is (0.9-1.3):1.

16. The method for preparing a cathode material for a lithium-ion battery according to claim 14, wherein in step (2), the calcination is conducted at a temperature of 600-1,100° C. for 5-40 h under an atmosphere of air or oxygen.

17. The method for preparing a cathode material for a lithium-ion battery according to claim 14, wherein in step (2), the lithium source is at least one selected from lithium hydroxide, lithium acetate, lithium nitrate, lithium sulfate, and lithium bicarbonate.

18. A cathode material for a lithium-ion battery prepared by the method according to claim 14.

19. (canceled)

20. The precursor according to claim 13, wherein the precursor has uniform particle distribution, spherical morphology, and a loose and porous surface.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0026] FIG. 1 is a scanning electron microscope image of an environment-friendly precursor obtained in Example 1.

[0027] FIG. 2 is a scanning electron microscope image of a composite oxide powder obtained in Example 1.

DESCRIPTION OF EMBODIMENTS

[0028] The present invention is described in detail below with examples.

Example 1

[0029] (1) A metal mixture (Ni, Co, Mn, Zr, and W five metals were mixed at a molar ratio of 1:1:1:0.03:0.05), nitric acid, highly pure water, and sodium sulfate were mixed at a molar ratio of 10:1:1:1, and then added into a reactor for a chemical corrosion crystallization reaction. Then, 10 g/L of ammonium sulfate was added. Under normal pressure conditions, the redox potential ORP value was controlled at −1,000 mv, the electrical conductivity was controlled at 200 uS/cm, the stirring input power was controlled at 1 kw/m.sup.3.Math.h, the concentration of metal ions was controlled at 5 g/L, the pH value was controlled at 6-8, the reaction temperature was controlled at 20° C., and the residence time of the above materials in the reactor was controlled at 30 h. The water was constantly consumed during crystallization, and no excess waste water is produced. After the complete reaction, magnetic separation was conducted at an intensity of 100 Gas to obtain a magnetic particle and a slurry. The slurry was subjected to solid-liquid separation to obtain a solid particle and a filtrate. The solid particle was washed and dried to obtain a precursor. The magnetic particle, the filtrate, and washing water were returned to the reactor for a continuous reaction. The water consumed during crystallization was supplemented. A scanning electron microscope (SEM) image of the precursor is shown in FIG. 1. From FIG. 1, it can be seen that the precursor has uniform particle distribution, spherical morphology, and a loose and porous surface.

[0030] (2) The precursor and a lithium source were uniformly mixed at a Li/Me molar ratio of 1.08:1, and then calcined at 740° C. for 12 h to finally obtain a composite oxide powder with Li/Me=1.08, which was recorded as QL-1. An SEM image of the composite oxide powder is shown in FIG. 2. From FIG. 2, it can be seen that the composite oxide powder obtained after sintering is a monocrystal product.

Example 2

[0031] (1) A metal mixture (NiO, MgO, ZrO, and WO.sub.3 four metals were mixed at a molar ratio of 1:0.005:0.006:0.004), nitric acid, highly pure water, and sodium chloride were mixed at a molar ratio of 10:1:1:2, and then added into a reactor for a chemical corrosion crystallization reaction. Then, 50 g/L of ethylenediamine tetraacetic acid was added. Under normal pressure conditions, the redox potential ORP value was controlled at 100 my, the electrical conductivity was controlled at 500 uS/cm, the stirring input power was controlled at 0.7 kw/m.sup.3.Math.h, the concentration of metal ions was controlled at 5 g/L, the pH value was controlled at 8-10, the reaction temperature was controlled at 60° C., and the residence time of the above materials in the reactor was controlled at 15 h. The water was constantly consumed during crystallization, and no excess waste water is produced. After the complete reaction, magnetic separation was conducted at an intensity of 5,000 Gas to obtain a magnetic particle and a slurry. The slurry was subjected to solid-liquid separation to obtain a solid particle and a filtrate. The solid particle was washed and dried to obtain a precursor. The magnetic particle, the filtrate, and washing water were returned to the reactor for a continuous reaction. The water consumed during crystallization was supplemented.

[0032] (2) The precursor and a lithium source were uniformly mixed at a Li/Me molar ratio of 1.06:1, and then calcined at 740° C. for 20 h to finally obtain a composite oxide powder with Li/Me=1.06, which was recorded as QL-2.

Example 3

[0033] (1) A metal mixture (Co, Al, Mg, and Ti four metals were mixed at a molar ratio of 1:0.01:0.004:0.005), nitric acid, highly pure water, and sodium nitrate were mixed at a molar ratio of 10:1:1:4, and then added into a reactor for a chemical corrosion crystallization reaction. Then, 30 g/L of ammonium nitrate was added. Under normal pressure conditions, the redox potential ORP value was controlled at −200 my, the electrical conductivity was controlled at 1,000 uS/cm, the stirring input power was controlled at 0.1 kw/m.sup.3.Math.h, the concentration of metal ions was controlled at 5 g/L, the pH value was controlled at 10-12, the reaction temperature was controlled at 90° C., and the residence time of the above materials in the reactor was controlled at 10 h. The water was constantly consumed during crystallization, and no excess waste water is produced. After the complete reaction, magnetic separation was conducted at an intensity of 2,000 Gas to obtain a magnetic particle and a slurry. The slurry was subjected to solid-liquid separation to obtain a solid particle and a filtrate. The solid particle was washed and dried to obtain a precursor. The magnetic particle, the filtrate, and washing water were returned to the reactor for a continuous reaction. The water consumed during crystallization was supplemented.

[0034] (2) The precursor and a lithium source were uniformly mixed at a Li/Me molar ratio of 1.06:1, and then calcined at 960° C. for 20 h to finally obtain a composite oxide powder with Li/Me=1.06, which was recorded as QL-3.

Example 4

[0035] (1) A metal mixture (Ni, Co, Al, Zr, and Ti five metals were mixed at a molar ratio of 1:0.12:0.15:0.01:0.012), nitric acid, highly pure water, and sodium sulfate were mixed at a molar ratio of 10:1:1:1, and then added into a reactor for a chemical corrosion crystallization reaction. Then, 30 g/L of ammonium chloride was added. Under normal pressure conditions, the redox potential ORP value was controlled at 100 mv, the electrical conductivity was controlled at 5,000 uS/cm, the stirring input power was controlled at 0.7 kw/m.sup.3.Math.h, the concentration of metal ions was controlled at 5 g/L, the pH value was controlled at 6-8, the reaction temperature was controlled at 60° C., and the residence time of the above materials in the reactor was controlled at 15 h. The water was constantly consumed during crystallization, and no excess waste water is produced. After the complete reaction, magnetic separation was conducted at an intensity of 2,000 Gas to obtain a magnetic particle and a slurry. The slurry was subjected to solid-liquid separation to obtain a solid particle and a filtrate. The solid particle was washed and dried to obtain a precursor. The magnetic particle, the filtrate, and washing water were returned to the reactor for a continuous reaction. The water consumed during crystallization was supplemented.

[0036] (2) The precursor and a lithium source were uniformly mixed at a Li/Me molar ratio of 1.05:1, and then calcined at 790° C. for 24 h to finally obtain a composite oxide powder with Li/Me=1.05, which was recorded as QL-4.

Example 5

[0037] A precursor and a composite oxide powder were prepared according to the method in Example 1. The difference was that the metal raw material was changed from a mixture of Ni, Co, Mn, Zr, and W five metals to a mixture of Ni, Co, and Mn at a molar ratio of 1:1:1, other conditions were the same as those in Example 1, and a precursor and a composite oxide powder with Li/Me=1.08 were obtained. The composite oxide powder was recorded as QL-5.

Example 6

[0038] A precursor and a composite oxide powder were prepared according to the method in Example 1. The difference was that the metal raw material was changed from a mixture of Ni, Co, Mn, Zr, and W five metals to a mixture of Ni, Co, and Mn at a molar ratio of 5:2:3, other conditions were the same as those in Example 1, and a precursor and a composite oxide powder with Li/Me=1.08 were obtained. The composite oxide powder was recorded as QL-6.

Example 7

[0039] A precursor and a composite oxide powder were prepared according to the method in Example 1. The difference was that the metal raw material was changed from a mixture of Ni, Co, Mn, Zr, and W five metals to a mixture of Ni, Co, and Mn at a molar ratio of 10:1:1.5, other conditions were the same as those in Example 1, and a precursor and a composite oxide powder with Li/Me=1.08 were obtained. The composite oxide powder was recorded as QL-7.

Example 8

[0040] A precursor and a composite oxide powder were prepared according to the method in Example 1. The difference was that the metal raw material was changed from a mixture of Ni, Co, Mn, Zr, and W five metals to a mixture of Ni and Co at a molar ratio of 4:1, other conditions were the same as those in Example 1, and a precursor and a composite oxide powder with Li/Me=1.08 were obtained. The composite oxide powder was recorded as QL-8.

Example 9

[0041] A precursor and a composite oxide powder were prepared according to the method in Example 1. The difference was that the metal raw material was changed from a mixture of Ni, Co, Mn, Zr, and W five metals to a mixture of Ni and Mg at a molar ratio of 9.5:0.5, other conditions were the same as those in Example 1, and a precursor and a composite oxide powder with Li/Me=1.08 were obtained. The composite oxide powder was recorded as QL-9.

Comparative Example 1

[0042] A precursor and a composite oxide powder were prepared according to the method in Example 5. The difference was that the ammonium sulfate was added in an amount of 1 g/L, other conditions were the same as those in Example 5, and a precursor and a composite oxide powder with Li/Me=1.08 were obtained. The composite oxide powder was recorded as DQL-1.

Comparative Example 2

[0043] A precursor and a composite oxide powder were prepared according to the method in Example 5. The difference was that the molar ratio of the metal mixture to the nitric acid to the highly pure water to the sodium sulfate was changed from 10:1:1:1 to 10:1:1:0.5 to control the electrical conductivity of the system at 100 uS/cm, other conditions were the same as those in Example 5, and a precursor and a composite oxide powder with Li/Me=1.08 were obtained. The composite oxide powder was recorded as DQL-2.

Comparative Example 3

[0044] A precursor and a composite oxide powder were prepared according to the method in Example 5. The difference was that the redox potential ORP value was controlled at 150 mv, and a precursor and a composite oxide powder with Li/Me=1.08 were obtained. The composite oxide powder was recorded as DQL-3.

Test Example

[0045] (1) Properties of Precursors:

[0046] Results of the particle size, tap density, and consistency are shown in Table 1. The particle size and the consistency were determined by using a Malvern laser particle size analyzer.

[0047] (2) Electrochemical Performance of Lithium-Ion Batteries:

[0048] The composite oxide powders obtained in Examples 1 to 9 and the reference composite oxide powders obtained in Comparative Examples 1 to 3 were separately used as a cathode material. The cathode material, conductive carbon black, and polyvinylidene fluoride (PVDF) were dissolved in an NMP solvent at a mass ratio of 80:10:10 under a vacuum condition to obtain a positive slurry with a solid content of 70% by weight. The positive slurry was spread on an aluminum foil current collector, dried at 120° C. under vacuum for 12 h, and then punched to obtain a positive wafer with a diameter of 19 mm Composite modified graphite, CMC, and SBR were dissolved in deionized water at a mass ratio of 90:5:5 under a vacuum condition to obtain a negative slurry with a solid content of 40% by weight. The negative slurry was spread on a copper foil current collector, dried at 100° C. under vacuum for 12 h, and then punched to obtain a negative wafer with a diameter of 19 mm A ratio of a negative capacity to a positive capacity was 1.1:1. A battery was assembled in a glove box filled with argon in the following sequence: a positive shell, a positive plate, a diaphragm, a negative plate, a stainless steel plate, a spring plate, and a negative shell. 1 mol/L of a mixture of LiPF.sub.6/EC and DMC (at a volume ratio of 1:1) supplemented with 10% (by volume fraction) fluoroethylene carbonate (FEC) was used as an electrolyte, a polypropylene microporous membrane was used as the diaphragm, and lithium-ion batteries C1-C9 and reference lithium-ion batteries DC1-DC3 were obtained. The first discharge performance of the lithium-ion batteries C1-C9 and reference lithium-ion batteries DC1-DC3 was tested, and results are shown in Table 1.

TABLE-US-00001 TABLE 1 Tap First Serial D10 D50 D90 density discharge Number number (μm) (μm) (μm) (μm) Consistency performance Example 1 QL-1 2.14 4.04 8.4 2.35 0.45 162 mAh/g Example 2 QL-2 4.70 9.80 18.9 2.67 0.41 228 mAh/g Example 3 QL-3 4.90 14.6 35.6 2.91 0.48 193 mAh/g Example 4 QL-4 5.00 10.4 19.7 2.59 0.43 218 mAh/g Example 5 QL-5 2.24 4.12 6.6 2.34 0.31 160 mAh/g Example 6 QL-6 2.24 3.89 8.1 2.37 0.41 171 mAh/g Example 7 QL-7 2.14 4.04 7.1 2.23 0.45 214 mAh/g Example 8 QL-8 1.10 3.13 8.5 2.34 0.46 210 mAh/g Example 9 QL-9 2.14 4.04 6.1 2.23 0.45 214 mAh/g Comparative DQL-1 4.40 7.90 13.7 2.48 0.41 156 mAh/g Example 1 Comparative DQL-2 3.20 6.80 15.5 2.55 0.42 154 mAh/g Example 2 Comparative DQL-3 2.34 4.34 8.9 2.45 0.45 157 mAh/g Example 3

[0049] Although the examples of the present invention have been illustrated and described above, it may be understood that the above examples are exemplary and should not be understood as a limitation of the present invention. Changes, modifications, substitutions, and variations may be made by those of ordinary skill in the art to the above examples within the scope of the present invention without departing from the principle and purpose of the present invention.