Direct repair method of waste ternary lithium battery positive electrode material

Abstract

The invention provides a direct repair method of a waste ternary lithium battery positive electrode material, and belongs to the technical field of lithium battery positive electrode materials. According to the invention, the molten salt is adopted to supplement lithium, the method has the characteristics of low melting point and high reaction activity, the potassium salt is added as a fluxing agent, a good environment can be provided for the lithium supplement reaction, the transportation and conduction of lithium ions are facilitated, and the potassium salt is matched with the lithium supplement salt, so that the usage amount of the lithium supplement salt can be reduced. By adding a compound system of the graphite and the carbon powder, the advantage of point-line contact between a layered conductive network of the graphite and the carbon powder can be combined, the processability is optimized while high conductivity is ensured, the graphite provides a basic conductive skeleton, and the carbon powder fills micro pores, so that the compaction density of the material is improved. By adopting the repairing method disclosed by the invention, the obtained positive electrode material is good in structure recovery and excellent in electrochemical performance, and is basically consistent with commercial ternary positive electrode powder.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery positive electrode materials, and in particular to a method for directly repairing waste ternary lithium battery positive electrode materials. Background Art

[0002] Lithium-ion batteries offer unique advantages in chemical energy storage, including high energy density, light weight, compact size, long lifespan, and low self-discharge. Since their introduction, they have rapidly dominated the battery market, driving a shift in the electronics market from small consumer products to electric vehicles and power storage. Used lithium batteries contain significant amounts of precious metals such as cobalt, nickel, manganese, and lithium. Direct disposal not only wastes resources but also pollutes and damages the environment. Therefore, repairing the cathode materials in used ternary lithium batteries and enabling battery recycling is crucial for environmental protection and the resourceful utilization of precious metals.

[0003] A typical repair process for waste ternary lithium battery positive electrode materials should include: (1) impurity removal, mainly through solvent dissolution and high-temperature burning; (2) lithium replenishment, mainly through solvent lithium replenishment and molten salt lithium replenishment.

[0004] Currently, the molten salt method for lithium replenishment has shown many advantages, such as being environmentally friendly and energy-saving. However, the current molten salt method for lithium replenishment often has the following disadvantages: (1) impurity removal and lithium replenishment are performed separately, which increases the production process and cost; (2) simply adding lithium salt as a lithium replenisher results in poor capacity retention of the repaired cathode material. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for directly repairing the positive electrode material of waste ternary lithium batteries. The repair method provided by the present invention can repair the positive electrode material of waste ternary lithium batteries simply, efficiently, and at low cost, and the resulting repaired positive electrode material has good cycle performance.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a direct repair method for waste ternary lithium battery positive electrode materials, comprising the following steps:

[0008] Mixing cathode material powder with lithium salt, potassium salt, graphite, carbon powder and a binder, and performing a first heat treatment to obtain lithium-supplemented powder;

[0009] The lithium-supplemented powder is sequentially washed, dried and subjected to a second heat treatment to obtain a repaired positive electrode material.

[0010] Preferably, the lithium salt includes one or more of lithium hydroxide, lithium carbonate and lithium nitrate;

[0011] The potassium salt includes one or more of potassium carbonate, potassium nitrate, potassium hydroxide and potassium acetate.

[0012] Preferably, the carbon powder comprises one or more of sucrose, glucose and charcoal;

[0013] The binder includes polyvinylidene fluoride and / or polyhexafluoropropylene.

[0014] Preferably, the mass ratio of the positive electrode material powder to the lithium salt is 1:0.5-4;

[0015] The mass ratio of the positive electrode material powder to the potassium salt is 1:2-8.

[0016] Preferably, the mass ratio of the positive electrode material powder to graphite is 1:0.2-1.6;

[0017] The mass ratio of the positive electrode material powder to the carbon powder is 1:0.15-1.2;

[0018] The mass ratio of the positive electrode material powder to the binder is 1:0.15-1.2.

[0019] Preferably, the graphite D 90 Particle size is 10nm~1μm;

[0020] The particle size of the carbon powder is 1 μm to 500 μm.

[0021] Preferably, the temperature of the first heat treatment is 450-600°C and the time is 2-5 hours;

[0022] The heating rate for heating to the first heat treatment temperature is 1-5°C / min.

[0023] Preferably, the temperature of the second heat treatment is 600-1000°C and the time is 2-5 hours;

[0024] The heating rate for heating to the second heat treatment temperature is 1-5°C / min.

[0025] Preferably, the positive electrode material powder comes from NCM batteries and / or NCA batteries.

[0026] The present invention provides a repaired positive electrode material obtained by the above method.

[0027] The present invention provides a direct repair method for waste ternary lithium battery positive electrode materials, comprising the following steps: mixing positive electrode material powder with lithium salt, potassium salt, graphite, carbon powder and a binder, performing a first heat treatment to obtain lithium-supplemented powder; and sequentially washing, drying and performing a second heat treatment on the lithium-supplemented powder to obtain a repaired positive electrode material. The present invention adopts molten salt to supplement lithium, which has the characteristics of low melting point and high reaction activity. By adding potassium salt as a flux, it can provide a good environment for the lithium-supplementing reaction, which is conducive to the transport and conduction of lithium ions. The combination of potassium salt and lithium-supplementing salt can reduce the amount of lithium-supplementing salt used. By adding a composite system of graphite and carbon powder, the present invention can combine the advantages of the layered conductive network of graphite and the point-line contact of carbon powder, optimize the processing performance while ensuring high conductivity. Graphite provides a basic conductive skeleton, and carbon powder fills microscopic pores, thereby improving the compaction density of the material.

[0028] In addition, the present invention does not require additional impurity removal operations. The conductive agent (such as acetylene black) and the binder can be removed simultaneously with the help of a molten medium and a first heat treatment. The process is simple, efficient, and low-cost. Using the repair method of the present invention, the obtained positive electrode material has good structural restoration and excellent electrochemical performance, which is basically consistent with the commercial ternary positive electrode powder. The repair method provided by the present invention has universal applicability and can repair all positive electrode materials (such as nickel-cobalt-manganese or nickel-cobalt-aluminum) in which the metal elements in the waste ternary lithium battery positive electrode material are combined in any proportion. DETAILED DESCRIPTION

[0029] The present invention provides a direct repair method for waste ternary lithium battery positive electrode materials, comprising the following steps:

[0030] Mixing cathode material powder with lithium salt, potassium salt, graphite, carbon powder and a binder, and performing a first heat treatment to obtain lithium-supplemented powder;

[0031] The lithium-supplemented powder is sequentially washed, dried and subjected to a second heat treatment to obtain a repaired positive electrode material.

[0032] The present invention mixes the positive electrode material powder with lithium salt, potassium salt, graphite, carbon powder and a binder, and performs a first heat treatment to obtain lithium-supplemented powder. In the present invention, the positive electrode powder is the positive electrode material powder of waste ternary lithium batteries. In the present invention, the positive electrode material powder is preferably derived from NCM batteries and / or NCA batteries. In the present invention, the particle size of the positive electrode material powder is preferably 1 μm to 500 μm, more preferably 10 to 400 μm, and further preferably 100 to 300 μm. The present invention has no special requirements for the elemental composition of the positive electrode material powder. All positive electrode materials derived from NCM batteries and / or NCA batteries and combined in any proportion are applicable to the repair method of the present invention.

[0033] In the present invention, the lithium loss amount of the positive electrode material is preferably 5 to 30%, and more preferably 10 to 20%.

[0034] In the present invention, the lithium salt preferably includes one or more of lithium hydroxide, lithium carbonate and lithium nitrate; the mass ratio of the positive electrode material powder to the lithium salt is preferably 1:0.5-4, more preferably 1:2-3.

[0035] In the present invention, the potassium salt preferably includes one or more of potassium carbonate, potassium nitrate, potassium hydroxide, and potassium acetate; the mass ratio of the positive electrode material powder to the potassium salt is preferably 1:2-8, more preferably 1:4-6. In the present invention, the potassium salt acts as a flux, providing a favorable environment for the lithium replenishment reaction and facilitating the transport and conduction of lithium ions. The combination of the potassium salt and the lithium replenishment salt can reduce the amount of lithium replenishment salt used.

[0036] In the present invention, the D of the graphite 90 The particle size is 10 nm to 5 μm, preferably 100 nm to 1 μm. In the present invention, the mass ratio of the positive electrode material powder to graphite is preferably 1:0.2 to 1.6, more preferably 1:0.8 to 1.2.

[0037] In the present invention, the carbon powder preferably includes one or more of charcoal powder, sucrose powder, and glucose powder. The sucrose powder and glucose powder are obtained by calcining sucrose and glucose, and the calcination temperature is preferably 500-600°C. The particle size of the carbon powder is preferably 1 μm to 500 μm, more preferably 50-400 μm, and even more preferably 100-300 μm. In the present invention, the mass ratio of the positive electrode material powder to the carbon powder is preferably 1:0.15-1.2, and more preferably 1:0.6-0.9.

[0038] In the present invention, the binder comprises polyvinylidene fluoride and / or polyhexafluoropropylene. In the present invention, the mass ratio of the positive electrode material powder to the binder is preferably 1:0.15-1.2, more preferably 1:0.6-0.9.

[0039] In the present invention, the mass ratio of the positive electrode material, lithium salt, potassium salt, graphite, carbon powder and binder preferably satisfies the following: positive electrode material: lithium salt: potassium salt: graphite: carbon powder: binder = 1:x:2x:0.4x:0.3x:0.3x, where x = 0.5 to 4, preferably 2 to 3.

[0040] The present invention has no special requirements for the mixing method, and any mixing method well known to those skilled in the art can be used, such as stirring mixing.

[0041] In the present invention, the atmosphere for the first heat treatment is preferably one or more of air, oxygen, argon, and nitrogen. In the present invention, the temperature for the first heat treatment is preferably 450-600°C, more preferably 500-550°C, and the holding time is preferably 2-5 hours, more preferably 3-4 hours. In the present invention, the heating rate for the first heat treatment is preferably 1-5°C / min. By performing the first heat treatment at 450-600°C, the present invention can simultaneously achieve lithium replenishment and impurity removal.

[0042] After obtaining the lithium-supplemented powder, the present invention sequentially washes, dries, and then performs a second heat treatment to obtain a repaired positive electrode material. In the present invention, the washing is preferably performed with water, and the washing time is preferably 10 minutes. The water washing can remove excess lithium salts from the lithium-supplemented powder. After the water washing, the present invention preferably performs centrifugation.

[0043] The present invention has no special requirements for the drying method, and any drying method known in the art may be used, such as drying in a blast drying oven.

[0044] In the present invention, the atmosphere of the second heat treatment is preferably one or more of air, oxygen, argon, and nitrogen. In the present invention, the temperature of the second heat treatment is preferably 600-1000°C, specifically 600°C, 700°C, 800°C, 900°C, or 1000°C. The holding time of the second heat treatment is preferably 2-5 hours, more preferably 3-4 hours. In the present invention, the heating rate to the second heat treatment is preferably 1-5°C / min. By performing the second heat treatment at 600-1000°C, the present invention can stabilize the crystal structure of the lithium-supplementing material and increase the compaction density.

[0045] After the second heat treatment, the present invention preferably cools the repaired positive electrode material to room temperature, and the cooling rate is preferably 10° C. / min.

[0046] The present invention provides a repaired positive electrode material obtained by the above method.

[0047] The direct repair method of waste ternary lithium battery positive electrode materials provided by the present invention is described in detail below with reference to the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] A method for directly repairing the positive electrode material of waste ternary lithium batteries comprises the following steps:

[0050] Weigh 1g of 523 type ternary lithium battery positive electrode material powder (lithium loss is 21.5%), with a particle size of 1μm, and weigh 0.5g of lithium hydroxide, 1g of potassium carbonate, 0.2g of graphite (D 90 Particle size 5μm), 0.15g wood charcoal powder (D 50 The mixture was mixed evenly with 0.15 g PVDF and placed in a muffle furnace at 500 ° C for 4 h at a heating rate of 5 ° C / min in a nitrogen atmosphere. After the insulation was completed, the mixture was naturally cooled to obtain lithium supplement powder.

[0051] The lithium-replenished powder was poured into a beaker containing deionized water and stirred for 10 minutes. The excess lithium salts were removed by centrifugation three times, and the resulting precipitate was dried in a forced-air drying oven. 0.6 g of the dried powder was placed in an Al2O3 crucible and heated at 750°C in a tube furnace for 5 hours with oxygen as a protective atmosphere. The temperature was increased at a rate of 5°C / min. After the temperature was maintained at 750°C, the material was cooled to room temperature at a rate of 10°C / min to obtain the repaired cathode material.

[0052] Example 2

[0053] A method for directly repairing the positive electrode material of waste ternary lithium batteries comprises the following steps:

[0054] Weigh 1g of 523 type ternary lithium battery positive electrode material powder (lithium loss is 30%), with a particle size of 100μm, and weigh 2g of lithium carbonate, 4g of potassium carbonate, 0.8g of graphite (D 90 Particle size 5μm), 0.6g wood charcoal powder (D 50 The mixture was mixed evenly with 0.6 g PVDF and placed in a muffle furnace at 550 ° C for 4 h at a heating rate of 5 ° C / min in an argon atmosphere. After the insulation was completed, the mixture was naturally cooled to obtain lithium-supplemented powder.

[0055] The lithium-replenished powder was poured into a beaker containing deionized water and stirred for 10 minutes. The mixture was centrifuged three times to remove excess lithium salts, and the resulting precipitate was dried in a forced-air drying oven. 0.6 g of the dried powder was placed in an Al2O3 crucible and heated in a tube furnace at 700°C for 5 hours with oxygen as a protective atmosphere. The temperature was increased at a rate of 5°C / min. After the temperature was maintained at this temperature, the material was cooled to room temperature at a rate of 10°C / min to obtain the repaired cathode material.

[0056] Example 3

[0057] A method for directly repairing the positive electrode material of a waste ternary lithium battery comprises the following steps:

[0058] Weigh 1g of 523 type ternary lithium battery positive electrode material powder (lithium loss is 30%), with a particle size of 200μm, and weigh 3g of lithium hydroxide, 6g of potassium carbonate, 1.2g of graphite (D 90 Particle size 5μm), 0.9g wood charcoal powder (D 50 The mixture was mixed evenly with 0.9 g PVDF and placed in a muffle furnace at 550 ° C for 5 h at a heating rate of 5 ° C / min in an air atmosphere. After the insulation was completed, the mixture was naturally cooled to obtain lithium supplement powder.

[0059] The lithium-replenished powder was poured into a beaker containing deionized water and stirred for 10 minutes. The mixture was centrifuged three times to remove excess lithium salts, and the resulting precipitate was dried in a forced-air drying oven. 0.6 g of the dried powder was placed in an Al2O3 crucible and heated in a tube furnace at 800°C for 4 hours with oxygen as a protective atmosphere. The temperature was increased at a rate of 5°C / min. After the temperature was maintained at this temperature, the mixture was cooled to room temperature at a rate of 10°C / min to obtain the repaired cathode material.

[0060] Comparative Example 1

[0061] Referring to Example 1, the addition of graphite was omitted and the performance was tested.

[0062] Comparative Example 2

[0063] Referring to Example 1, the addition of carbon powder was omitted and the performance was tested.

[0064] Comparative Example 3

[0065] Referring to Example 1, the addition of PVDF was omitted and the performance was tested.

[0066] Comparative Example 4

[0067] Commercial 523 type ternary cathode powder produced by a certain company.

[0068] Performance Testing

[0069] The electrochemical performance of the cathode materials obtained in the examples and comparative examples was tested according to the test method in accordance with GB / T30835-2014 "Test methods for electrochemical performance of cathode materials for lithium-ion batteries". The results are listed in Table 1.

[0070] Table 1 Electrochemical performance test results of the embodiments and comparative examples

[0071] sample First cycle (mAh / g) 100 cycles (mAh / g) Capacity retention rate% Example 1 150.7 143.2 95.02 Example 2 152.1 145.1 95.39 Example 3 155.2 146.4 94.32 Comparative Example 1 142 136 92.2 Comparative Example 2 141.3 137.3 93.1 Comparative Example 3 145.8 134.2 92.9 Comparative Example 4 159.3 152.8 95.92

[0072] As can be seen from Table 1, the positive electrode material obtained by the repair method of the present invention has a discharge capacity of more than 150 mAh / g in the first cycle, and it still has a relatively high capacity after 100 cycles, with a capacity retention rate of up to 95%, which is basically consistent with commercial ternary positive electrode powder.

[0073] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A direct repair method for waste ternary lithium battery positive electrode materials, characterized in that: The following steps are involved: Mixing cathode material powder with lithium salt, potassium salt, graphite, carbon powder and a binder, and performing a first heat treatment to obtain lithium-supplemented powder; The lithium-supplemented powder is sequentially washed, dried and subjected to a second heat treatment to obtain a repaired positive electrode material.

2. The method according to claim 1, characterized in that The lithium salt includes one or more of lithium hydroxide, lithium carbonate and lithium nitrate; The potassium salt includes one or more of potassium carbonate, potassium nitrate, potassium hydroxide and potassium acetate.

3. The method according to claim 1, characterized in that The carbon powder includes one or more of charcoal powder, sucrose carbon powder and glucose carbon powder; The binder includes polyvinylidene fluoride and / or polyhexafluoropropylene.

4. The method according to claim 1 or 2, characterized in that The mass ratio of the positive electrode material powder to the lithium salt is 1:0.5-4; The mass ratio of the positive electrode material powder to the potassium salt is 1:2-8.

5. The method according to claim 1 or 3, characterized in that The mass ratio of the positive electrode material powder to graphite is 1:0.2-1.6; The mass ratio of the positive electrode material powder to the carbon powder is 1:0.15-1.2; The mass ratio of the positive electrode material powder to the binder is 1:0.15-1.

2.

6. The method according to claim 1, wherein The graphite D 90 Particle size is 10nm~5μm; The particle size of the carbon powder is 1 μm to 500 μm.

7. The method according to claim 1, characterized in that The temperature of the first heat treatment is 450-600°C and the time is 2-5 hours; The heating rate for heating to the first heat treatment temperature is 1-5°C / min.

8. The method according to claim 1 or 7, characterized in that The second heat treatment temperature is 600-1000°C and the time is 2-5h; The heating rate for heating to the second heat treatment temperature is 1-5°C / min.

9. The method according to claim 1, characterized in that The positive electrode material powder comes from NCM batteries and / or NCA batteries.

10. The repaired positive electrode material obtained by the method according to any one of claims 1 to 9.