CN116111224A

CN116111224A - Recycling method of waste lithium iron phosphate battery positive electrode material, lithium iron phosphate positive electrode material and application thereof

Info

Publication number: CN116111224A
Application number: CN202310198958.5A
Authority: CN
Inventors: 林晓; 刘刚锋; 王雪
Original assignee: Suzhou Bocui Recycling Technology Co ltd
Current assignee: Suzhou Bocui Recycling Technology Co ltd
Priority date: 2023-03-03
Filing date: 2023-03-03
Publication date: 2023-05-12

Abstract

The invention provides a recovery method of a waste lithium iron phosphate battery anode material, the lithium iron phosphate anode material and application thereof, wherein the method comprises the following steps: (1) Soaking the defective positive plate in an organic solvent, and drying at a low temperature to obtain recovered coarse powder; wherein the temperature of the low-temperature drying is not more than 100 ℃; (2) Soaking the recovered coarse powder in an organic solvent, separating and sieving to obtain a positive current collector and positive powder; (3) And mixing the anode powder with a lithium source compound, and sintering to obtain the lithium iron phosphate anode material. The recovery method provided by the invention simplifies the recovery process of the anode material of the waste lithium iron phosphate battery, reduces the loss of valuable metals in the recovery process, greatly reduces the treatment cost, and can be directly used for preparing new anode slurry, and simultaneously ensures that the prepared battery has excellent electrochemical performance.

Description

Recycling method of waste lithium iron phosphate battery positive electrode material, lithium iron phosphate positive electrode material and application thereof

Technical Field

The invention belongs to the field of recovery of waste lithium ion batteries, and particularly relates to a recovery method of a waste lithium iron phosphate battery positive electrode material, a lithium iron phosphate positive electrode material and application thereof.

Background

With the large-scale popularization of electric automobiles, the demand of power batteries is greatly increased, a large number of defective products of the pole pieces inevitably appear in the production process of the battery pole pieces, and the battery pole pieces cannot be used in batteries. The structure, performance and the like of the positive electrode active material in the defective product of the part of positive electrode plate are not destroyed, and the positive electrode plate has perfect functions, so the defective product generated in the process of manufacturing the positive electrode plate has great recovery value and recovery significance.

At present, pole piece recovery is mainly achieved by a wet recovery mode, for example, CN113802002A discloses a method for recovering valuable metals in a lithium battery by a wet method, black powder of the waste battery is subjected to acid leaching to extract the valuable metals from the waste battery, and an alkali solution is needed to be used for adjusting the pH value during the acid leaching to obtain a specific product. CN110724818B discloses a full wet recovery process of waste lithium batteries, wherein the waste lithium batteries are crushed by electrification, battery crushed aggregates are directly leached, and the leaching liquid is subjected to in-situ impurity removal, acid leaching and extraction to obtain related metal salt products.

However, in the conventional wet recovery process, a large amount of auxiliary materials such as acid, alkali, organic solution and the like are used, and the wastewater yield is high. In addition, the material is subjected to crushing and screening, acid leaching and extraction to obtain a metal salt product, and then a new material is synthesized for manufacturing the anode material.

Therefore, how to simplify the recovery process and reduce the treatment cost, and simultaneously, the recovered lithium iron phosphate material can be directly used for preparing new positive electrode slurry is a technical problem to be solved.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a recovery method of a waste lithium iron phosphate battery anode material, the lithium iron phosphate anode material and application thereof. The recovery method provided by the invention simplifies the recovery process of the waste lithium iron phosphate battery anode material, reduces the loss of valuable metals in the recovery process, greatly reduces the recovery cost, and can directly use the recovered lithium iron phosphate material for preparing new anode slurry, and simultaneously can ensure that the battery can obtain excellent electrochemical performance.

In order to achieve the aim of the invention, the invention adopts the following technical scheme:

in a first aspect, the invention provides a method for recycling a positive electrode material of a waste lithium iron phosphate battery, comprising the following steps:

(1) Soaking the defective positive plate in an organic solvent, and drying at a low temperature to obtain recovered coarse powder;

wherein the temperature of the low-temperature drying is not more than 100 ℃;

(2) Soaking the recovered coarse powder in an organic solvent, separating and sieving to obtain a positive current collector and positive powder;

(3) And mixing the anode powder with a lithium source compound, and sintering to obtain the lithium iron phosphate anode material.

The recovery method provided by the invention not only simplifies the recovery process of the waste lithium iron phosphate battery anode material, reduces the loss of valuable metals in the recovery process and greatly reduces the treatment cost, but also can directly use the treated material for preparing new anode slurry, and can ensure that the battery can obtain excellent electrochemical performance.

In the present invention, the low-temperature drying temperature is not more than 100℃and may be, for example, 100℃and 90℃and 80℃and 70℃and 60 ℃.

According to the invention, the low-temperature drying is adopted, so that the falling-off efficiency of the positive electrode material on the pole piece can be improved, and other side reactions of the positive electrode active material can not be caused.

According to the invention, the recovered coarse powder is mixed with the organic solvent, so that the falling efficiency of the positive electrode material on the pole piece can be improved, and the risk of valuable metal loss is reduced.

According to the invention, the lithium source compound is added to be mixed with the positive electrode powder and sintered, so that lithium ions can be supplemented for the positive electrode powder, and the lithium deficiency is prevented. Meanwhile, the organic matters and a small amount of impurities remained in the anode powder can be removed by sintering.

Preferably, the organic solvent of step (1) comprises any one or a combination of at least two of N-methylpyrrolidone, ethylene glycol or N-dimethylacetamide.

Preferably, the soaking time in the step (1) is 8-12h, for example, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h or 12h, etc.

Preferably, the solid-to-liquid ratio of the defective positive electrode sheet in the step (1) to the organic solvent is 1g (3-4) mL, and may be 1 g/3 mL, 1 g/3.5 mL, 1 g/4 mL, or the like.

Preferably, the low temperature drying in step (1) is carried out at a temperature of 60 to 100 ℃, for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, or 100 ℃, etc., preferably 80 to 100 ℃.

In the invention, if the low-temperature drying temperature is too low, the drying time is too long, and the powder falling efficiency on the pole piece is reduced; if the temperature of low-temperature drying is too high, the aluminum foil of the positive electrode current collector becomes brittle, and the powder removal efficiency and the purity of the powder are affected.

It should be noted that the step is completed by drying the organic solvent on the surface of the pole piece at low temperature and evaporating the organic solvent.

Preferably, the organic solvent of step (2) comprises any one or a combination of at least two of N-methylpyrrolidone, ethylene glycol or N-dimethylacetamide.

Preferably, the soaking in step (2) is accompanied by stirring.

Preferably, the soaking temperature in the step (2) is 60-80 ℃, and can be 60 ℃, 63 ℃, 66 ℃, 69 ℃, 72 ℃, 75 ℃, 78 ℃, 80 ℃ or the like.

Preferably, the soaking time in the step (2) is 1-3h, for example, 1h, 1.5h, 2h, 2.5h, 3h, etc.

The separation method in the present invention is not limited, and may be, for example, filtration, suction filtration, standing, centrifugation, or the like, and if the product obtained after separation is a solid, the solid is sieved; if the product obtained after separation is a solid-liquid mixture, the solid-liquid mixture is sieved.

Preferably, the specific steps of the separation in step (2) are:

and (3) soaking the recovered coarse powder in an organic solvent to obtain a suspension, and standing and separating the suspension to obtain a solid-liquid mixture. The standing separation can improve the efficiency of the subsequent filter pressing step and reduce the time used for filter pressing.

In the invention, the separation can be completed after standing until the solution is layered and the supernatant is poured out. It should be noted that the upper organic solvent is collected by distillation and can be reused.

In one embodiment, sieving and press-filtering the solid-liquid mixture obtained after standing separation in sequence to obtain the positive electrode current collector and the positive electrode powder.

Preferably, the lithium source compound of step (3) comprises any one or a combination of at least two of lithium hydroxide, lithium nitrate or lithium carbonate.

Preferably, the mass fraction of the lithium source compound is 5 to 10%, for example, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10% based on 100% of the mass of the positive electrode powder in step (3).

According to the invention, a small amount of lithium source compound is added in the grinding process, so that not only can a lithium source and a lithium iron phosphate material be fully mixed, but also lithium supplementation can be more uniform, and if the mass fraction of the lithium source compound is too low, insufficient lithium supplementation is caused, and the electric performance is not up to the standard; if the mass fraction of the lithium source compound is too high, excessive impurities may be introduced, resulting in capacity skip.

Preferably, the mixing in step (3) is performed by wet ball milling.

It should be noted that, as will be understood by those skilled in the art, in the wet ball milling process, a solvent is present in the ball milling system, so as to disperse the positive electrode powder more uniformly, for example, ethanol, etc. The wet grinding can reduce the average particle size of the positive electrode powder, so that the particle size distribution is more uniform, and the aggregated particles are more dispersed, thereby preparing more standard lithium iron phosphate materials.

Preferably, the ball-to-material ratio in the wet ball milling is (2-4): 1, and for example, may be 2:1, 2.5:1, 3:1, 3.5:1, or 4:1.

In the invention, the ball-material ratio in wet ball milling refers to the mass ratio of grinding balls to positive electrode powder. In one embodiment, the size of the particle size of the grinding balls varies.

Preferably, the wet ball milling is performed at a rate of 300-450rpm, for example, 300rpm, 350rpm, 400rpm, 450rpm, or the like.

Preferably, the mixing time in step (3) is 8-12h, for example, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h or 12h, etc.

Preferably, the mixing in step (3) is followed by drying.

Preferably, the atmosphere of the sintering in the step (3) is an inert atmosphere, and the gas in the inert atmosphere comprises nitrogen, argon or the like.

Preferably, the sintering temperature in the step (3) is 700-800 ℃, and may be 700 ℃, 720 ℃, 740 ℃, 760 ℃, 780 ℃, 800 ℃ or the like.

Preferably, the sintering time in the step (3) is 2-3h, for example, 2h, 2.2h, 2.4h, 2.6h, 2.8h or 3h, etc.

Preferably, the positive electrode powder of step (3) is washed, dried and sieved before being mixed with the lithium source compound.

In the present invention, the number of times the positive electrode powder is washed is not limited, and may be, for example, 1, 2, 3, or the like. The purpose of sieving is to remove impurities and small-particle aluminum slag, and clean anode powder is obtained.

As a preferred technical solution, the method comprises the following steps:

(1) Soaking the defective positive plate in an organic solvent for 8-12h, and drying at 60-100 ℃ to obtain recovered coarse powder;

wherein the solid-to-liquid ratio of the defective positive electrode sheet to the organic solvent is 1g (3-4) mL;

(2) Soaking the recovered coarse powder in an organic solvent at 60-80 ℃ and stirring for 1-3 hours, standing and separating, and sieving to obtain a positive electrode current collector and positive electrode powder;

(3) Washing, drying and sieving the positive electrode powder, mixing the positive electrode powder with a lithium source compound, performing wet ball milling for 8-12h, and sintering for 2-3h in an inert atmosphere at 700-800 ℃ to obtain a lithium iron phosphate positive electrode material;

wherein, the mass fraction of the lithium source compound is 5-10% based on 100% of the mass of the positive electrode powder in the step (3), the ball-to-material ratio in the wet ball milling is (2-4): 1, and the wet ball milling speed is 300-450rpm.

In a second aspect, the present invention provides a lithium iron phosphate positive electrode material, which is recovered by the method described in the first aspect.

In a third aspect, the present invention provides a use of the lithium iron phosphate cathode material according to the second aspect for the preparation of a cathode slurry in a lithium ion battery.

The lithium iron phosphate anode material prepared by the method disclosed by the invention does not need modification or other treatment, can be directly used for preparing new anode slurry, and can ensure that the prepared battery has excellent electrochemical performance.

The numerical ranges recited herein include not only the recited point values, but also any point values between the recited numerical ranges that are not recited, and are limited to, and for the sake of brevity, the invention is not intended to be exhaustive of the specific point values that the recited range includes.

Compared with the prior art, the invention has the following beneficial effects:

the recovery method provided by the invention simplifies the recovery process of the anode material of the waste lithium iron phosphate battery, reduces the loss of valuable metals in the recovery process, greatly reduces the treatment cost, and the treated material does not need modification or other treatment, can be directly used for manufacturing new anode slurry, and can ensure that the manufactured battery has excellent electrochemical performance.

Drawings

Fig. 1 is a process flow diagram of recovery of lithium iron phosphate positive electrode material in example 1 of the present invention.

Fig. 2 is a graph showing the reversible specific discharge capacity and the initial efficiency of the lithium iron phosphate positive electrode materials recovered in examples 1, 6 and 7 according to the present invention.

Fig. 3 is a graph showing the comparison of electrical properties of lithium iron phosphate cathode materials recovered in examples 1 and 7 of the present invention.

Detailed Description

The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.

Example 1

The embodiment provides a method for recycling a positive electrode material of a waste lithium iron phosphate battery, which comprises the following steps:

(1) Soaking the defective positive plate in an organic solvent N-methyl pyrrolidone for 10 hours, and drying at a low temperature of 100 ℃ to obtain recovered coarse powder;

wherein the solid-to-liquid ratio of the defective positive electrode sheet to N-methylpyrrolidone is 1g:4mL;

(2) Soaking the recovered coarse powder in an organic solvent N-methylpyrrolidone, stirring at 80 ℃ for 3 hours, standing for separation, removing supernatant to obtain a solid-liquid mixture, and sequentially sieving and press-filtering the solid-liquid mixture to obtain a positive electrode current collector and a positive electrode powder;

(3) Washing the positive electrode powder with deionized water for 3 times, drying and sieving, mixing the positive electrode powder with lithium hydroxide and an ethanol solvent, performing wet ball milling for 10 hours, and sintering for 2.5 hours in a nitrogen atmosphere at 750 ℃ to obtain a lithium iron phosphate positive electrode material;

wherein, the mass fraction of lithium hydroxide is 8% based on 100% of the mass of the positive electrode powder in the step (3), the ball-to-material ratio in the wet ball milling is 3:1, and the wet ball milling speed is 400rpm.

Fig. 1 shows a process flow diagram of the recycling method provided in this embodiment.

Example 2

(1) Soaking the defective positive plate in ethylene glycol for 12 hours, and drying at 80 ℃ to obtain recovered coarse powder;

wherein the solid-to-liquid ratio of the defective positive electrode sheet to ethylene glycol is 1g:3.5mL;

(2) Soaking the recovered coarse powder in ethylene glycol, stirring at 60 ℃ for 1h, standing for separation, removing supernatant to obtain a solid-liquid mixture, and sequentially sieving and press-filtering the solid-liquid mixture to obtain a positive electrode current collector and a positive electrode powder;

(3) Washing the positive electrode powder with deionized water for 2 times, drying and sieving, mixing the positive electrode powder with lithium nitrate and ethanol solvent, performing wet ball milling for 8 hours, and sintering for 3 hours in nitrogen atmosphere at 700 ℃ to obtain a lithium iron phosphate positive electrode material;

wherein, the mass fraction of lithium hydroxide is 5% based on 100% of the mass of the positive electrode powder in the step (3), the ball-to-material ratio in the wet ball milling is 2:1, and the wet ball milling speed is 450rpm.

Example 3

(1) Soaking the defective positive plate in N-dimethylacetamide for 8 hours, and drying at 60 ℃ to obtain recovered coarse powder;

wherein the solid-to-liquid ratio of the defective positive electrode sheet to the N-dimethylacetamide is 1 g/3 mL;

(2) Soaking the recovered crude powder in N-dimethylacetamide, stirring at 70 ℃ for 2 hours, standing and separating to obtain a solid-liquid mixture, and sequentially sieving and press-filtering the solid-liquid mixture to obtain a positive electrode current collector and a positive electrode powder;

(3) Washing the positive electrode powder with deionized water for 3 times, drying and sieving, mixing the positive electrode powder with lithium carbonate and an ethanol solvent, performing wet ball milling for 12 hours, and sintering for 2 hours in an argon atmosphere at 800 ℃ to obtain a lithium iron phosphate positive electrode material;

wherein, the mass fraction of lithium hydroxide is 10% calculated by taking the mass of the positive electrode powder in the step (3) as 100%, the ball-to-material ratio in the wet ball milling is 4:1, and the wet ball milling speed is 300pm.

Example 4

This example differs from example 1 in that the drying temperature in step (1) is 50 ℃.

The remaining preparation methods and parameters remain the same as in example 1.

Example 5

This example differs from example 1 in that the drying temperature in step (1) is 110 ℃.

Example 6

This example differs from example 1 in that the wet ball milling time in step (3) was 4 hours.

Example 7

This example differs from example 1 in that the positive electrode powder was obtained only through step (1) and step (2).

Fig. 2 shows a comparative graph of the reversible discharge specific capacity and the first effect of the lithium iron phosphate cathode materials recovered in example 1, example 6 and example 7, wherein T-LFP-3, T-LFP-2 and T-LFP-1 are sample numbers of the lithium iron phosphate cathode materials recovered in example 1, example 6 and example 7, respectively, and it is known that the first-turn reversible discharge specific capacity and the first effect of the lithium iron phosphate cathode materials recovered in example 1 are excellent, and the first-discharge specific capacity can reach 164.4mAh/g and approach to the theoretical capacity of 170 mAh/g.

Fig. 3 shows a comparative graph of the electrical properties of the lithium iron phosphate cathode materials recovered in examples 1 and 7, and it can be seen from the graph that the reversible charge-discharge capacity of the milled lithium iron phosphate material is significantly higher than that of the lithium iron phosphate material directly subjected to the powder removal, and the capacity retention rate also shows a better level.

Particle size tests of D50 and D90 were performed on the lithium iron phosphate cathode materials recovered in example 1, example 6 and example 7, and the test results are shown in table 1.

TABLE 1

Analysis:

the table shows that the average particle size of the lithium iron phosphate anode material recovered after wet grinding treatment in the protection time of the invention is effectively improved, and the uniformity of the material is also obviously improved.

Example 8

This example differs from example 1 in that the mass fraction of lithium hydroxide in step (3) is 3%.

Example 9

This example differs from example 1 in that the mass fraction of lithium hydroxide in step (3) is 12%.

Comparative example 1

This comparative example differs from example 1 in that step (2) was not performed.

Comparative example 2

This comparative example differs from example 1 in that no lithium source compound was added in step (3).

Comparative example 3

This comparative example differs from example 1 in that the temperature of drying in step (1) was 300 ℃.

Performance testing

The lithium iron phosphate cathode materials recovered in examples 1 to 9 and comparative examples 1 to 3 were directly used for the preparation of cathode slurry, and then made into a cathode sheet, and assembled with an anode sheet, an electrolyte and a separator to obtain a lithium iron phosphate battery.

Test conditions: room temperature, 1C.

The test results are shown in Table 2.

TABLE 2

Analysis:

the data results of examples 1-3 show that the lithium iron phosphate obtained by the recovery method provided by the invention can be directly used for manufacturing a new positive electrode plate while ensuring the battery performance.

As can be seen from comparison of the data results of the embodiment 1 and the embodiment 4-5, the too low drying temperature can result in too long drying time, lower efficiency of powder falling off on the pole piece and influence the battery performance; when the drying temperature is too high, the positive electrode active material undergoes a side reaction, and therefore the purity of the powder removing material is affected, and the battery performance is affected.

From comparison of the data results of example 1 and examples 6-7, it is seen that both short-time wet milling and direct mixing result in a decrease in the first-turn reversible discharge specific capacity and first efficiency of the recovered lithium iron phosphate cathode material.

As can be seen from comparison of the data obtained in examples 1 and 8-9, the addition of too little lithium source compound resulted in insufficient lithium supplementation and insufficient electrical performance; the addition of too much lithium source compound can introduce too much impurities, resulting in capacity chunking.

As is clear from comparison of the data results of example 1 and comparative example 1, the positive electrode material on the positive electrode current collector was less likely to fall off without mixing the obtained coarse powder with an organic solvent after drying at low temperature.

As is clear from comparison of the data results of example 1 and comparative example 2, the performance of the material does not reach the market index without adding the lithium source compound, and the capacity is low.

As can be seen from comparison of the data results of example 1 and comparative example 3, high temperature drying can cause embrittlement of the aluminum foil of the current collector, and the aluminum content of the material obtained by powder removal is high, which seriously affects the battery performance.

The applicant states that the process of the invention is illustrated by the above examples, but the invention is not limited to, i.e. does not mean that the invention must be carried out in dependence on the above process steps. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of selected raw materials, addition of auxiliary components, selection of specific modes, etc. fall within the scope of the present invention and the scope of disclosure.

Claims

1. The method for recycling the anode material of the waste lithium iron phosphate battery is characterized by comprising the following steps of:

wherein the temperature of the low-temperature drying is not more than 100 ℃;

2. The method of claim 1, wherein the organic solvent of step (1) comprises any one or a combination of at least two of N-methylpyrrolidone, ethylene glycol, or N-dimethylacetamide;

preferably, the soaking time in the step (1) is 8-12 hours;

preferably, the solid-to-liquid ratio of the defective positive electrode sheet to the organic solvent in the step (1) is 1g (3-4) mL;

preferably, the low temperature drying in step (1) is at a temperature of 60-100 ℃, preferably 80-100 ℃.

3. The method according to claim 1 or 2, wherein the organic solvent of step (2) comprises any one or a combination of at least two of N-methylpyrrolidone, ethylene glycol, or N-dimethylacetamide;

preferably, stirring is carried out during the soaking in the step (2);

preferably, the soaking temperature in the step (2) is 60-80 ℃;

preferably, the soaking time in the step (2) is 1-3h.

4. A method according to any one of claims 1-3, wherein the specific step of separating in step (2) is:

and (3) soaking the recovered coarse powder in an organic solvent to obtain a suspension, and standing and separating the suspension to obtain a solid-liquid mixture.

5. The method of any one of claims 1-4, wherein the lithium source compound of step (3) comprises any one or a combination of at least two of lithium hydroxide, lithium nitrate, or lithium carbonate;

preferably, the mass fraction of the lithium source compound is 5 to 10% based on 100% of the mass of the positive electrode powder in step (3).

6. The method according to any one of claims 1 to 5, wherein the mixing in step (3) is by wet ball milling;

preferably, the ball-to-material ratio in the wet ball milling is (2-4): 1;

preferably, the wet ball milling speed is 300-450rpm;

preferably, the mixing time of step (3) is 8-12 hours;

preferably, after the mixing in step (3), drying is performed;

preferably, the atmosphere of the sintering in the step (3) is an inert atmosphere, and the gas in the inert atmosphere comprises nitrogen or argon;

preferably, the sintering temperature in the step (3) is 700-800 ℃;

preferably, the sintering time in the step (3) is 2-3h.

7. The method of any one of claims 1-6, wherein the positive electrode powder of step (3) is washed, dried, and sieved prior to mixing with the lithium source compound.

8. The method according to any one of claims 1-7, characterized in that the method comprises the steps of:

9. A lithium iron phosphate positive electrode material, characterized in that the lithium iron phosphate positive electrode material is recovered by the method of any one of claims 1 to 8.

10. Use of the lithium iron phosphate positive electrode material according to claim 9 for the preparation of positive electrode slurry in a lithium ion battery.