Method for recycling waste lithium ion battery negative electrode graphite

Abstract

The application discloses a method for recycling waste lithium ion battery negative electrode graphite, wherein the waste lithium ion battery negative electrode graphite is a filter residue obtained by filtering a mixture of positive and negative electrode powders obtained by crushing and sorting waste lithium ion batteries, and then by H2SO4-H2O2 leaching, and the main component of the filter residue is negative electrode graphite; and the obtained negative electrode graphite is treated to realize resource recycling.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of new energy lithium battery negative graphite, and particularly relates to a method for recycling waste lithium ion battery negative graphite.

BACKGROUND TECHNIQUE

[0002] In the past decade, new energy vehicles have developed rapidly in China. The power battery, which is called the "heart" of new energy vehicles, generally has a service life of 5-8 years. In recent years, the amount of waste batteries for new energy vehicles has gradually increased. The research institute EVTank and the IVEY Economic Research Institute studied the development of the waste lithium ion battery recycling and disassembly and tier utilization industry in China. The results show that the actual recycling amount of waste lithium ion batteries in China in 2022 was 415,000 tons, an increase of 75.8% year on year. The market size of the entire industry increased to 15.44 billion yuan, an increase of 182.8% year on year.

[0003] As the peak of power battery retirement approaches, the industry generally has a good outlook for the waste lithium ion battery recycling industry. It is estimated that the amount of retired batteries will reach 437 GWh in 2030, and the recycling market value will reach 169.5 billion yuan. Some research institutions are even more optimistic, predicting that the industry size will exceed 100 billion yuan in 2025. However, the development of the power battery recycling industry still faces many problems.

[0004] Negative graphite is the carrier of lithium ions and electrons during the charging process of the battery, and plays a role in energy storage and release. In the cost of the battery, the negative graphite accounts for about 5%-15%, and is one of the important raw materials of lithium ion batteries.

[0005] Based on the application of lithium battery negative graphite in power batteries, consumer batteries and energy storage batteries in the future, it is preliminarily predicted that the demand for lithium battery negative graphite will reach 1.27 million tons by 2026, with an annual compound growth rate of 25%.

[0006] If the graphite in the negative active material of the waste battery can be recycled and treated for recycling, the social and economic value will be very significant.

SUMMARY OF THE INVENTION

[0007] In view of the problems of the existing resource recycling and regeneration technology of waste lithium ion battery negative graphite and the low material performance, the application provides a method for recycling waste lithium ion battery negative graphite, so as to solve the problems of the existing resource recycling and regeneration technology of waste lithium ion battery negative graphite and the low material performance, and further realize efficient treatment, performance improvement and the like.

[0008] The purpose of the application is achieved by the following technical scheme.

[0009] A method for recycling negative electrode graphite of waste lithium ion batteries, the filter residue after leaching of the positive and negative electrode powder of the lithium ion battery is rinsed, the pH of the solution after rinsing is controlled at 1-4, secondary pressure filtration is carried out after rinsing, secondary pressure filtration residue is obtained, analysis and detection are carried out, and it is determined that the main component of the secondary pressure filtration residue is negative electrode graphite; the obtained secondary pressure filtration residue is subjected to deep purification and impurity removal cleaning, dryness, high-temperature impurity removal and multiple rinsing are adopted to remove acid and heavy metal ions, until the pH of the graphite slurry is 6-8, high-purity negative electrode graphite slurry after purification and impurity removal cleaning is obtained; the obtained high-purity negative electrode graphite slurry is subjected to ultrasonic dispersion, the ultrasonic power is controlled at 100-200W, and drying is carried out, graphite material is obtained; the graphite material obtained in the above step is subjected to modification treatment under high temperature and in an atmosphere keeping weak oxidizability, the temperature is controlled at 750-950℃, and the time is controlled at 10-30min, modified graphite material is obtained.

[0010] Specifically, the method for recycling negative electrode graphite of waste lithium ion batteries comprises the following steps:

[0011] 1) The collected waste lithium ion batteries are crushed and sorted to obtain positive and negative electrode mixed powder;

[0012] 2) The positive and negative electrode mixed powder obtained in the above step is subjected to H2SO4-H2O2 leaching, the positive electrode material is dissolved, the negative electrode material is not dissolved, and first pressure filtration residue is obtained through first pressure filtration;

[0013] 3) The first pressure filtration residue obtained in the above step is rinsed, the pH of the solution after rinsing is controlled at 1-4, secondary pressure filtration is carried out after rinsing, secondary pressure filtration residue is obtained, analysis and detection are carried out, and it is determined that the main component of the secondary pressure filtration residue is negative electrode graphite;

[0014] 4) The secondary pressure filtration residue obtained in the above step is subjected to deep purification and impurity removal cleaning, dryness, high-temperature impurity removal and multiple rinsing are adopted to remove acid and heavy metal ions, until the pH of the graphite slurry is 6-8, high-purity negative electrode graphite slurry after purification and impurity removal cleaning is obtained;

[0015] 5) The high-purity negative electrode graphite slurry obtained in the step is subjected to ultrasonic dispersion, the ultrasonic power is controlled at 100-200W, and drying is carried out, graphite material is obtained;

[0016] 6) The graphite material obtained in the above step is subjected to modification treatment under high temperature and in an atmosphere keeping weak oxidizability, the temperature is controlled at 750-950℃, and the time is controlled at 10-30min, modified graphite material is obtained.

[0017] In the present application:

[0018] In step 2), the water content of the first pressure filtration residue is ensured to be ≤50%.

[0019] In step 3), the medium used for rinsing is selected from pure water or an alkaline solution.

[0020] In step 3), the moisture content of the secondary pressure filtration residue is ensured to be ≤50%.

[0021] In step 4), the drying is performed at a low temperature, with the temperature controlled at 80-120℃, and the moisture content of the dried material controlled at 8-15%.

[0022] In step 4), the high-temperature impurity removal is performed at a temperature of 700-900℃ for 10-30min.

[0023] In step 4), the multiple rinsing for removing acid and heavy metal ions is performed after the material after high-temperature impurity removal is cooled to room temperature, and the rinsing is performed multiple times until the pH of the graphite slurry is 6-8.

[0024] In step 5), the drying is preferably spray drying.

[0025] In step 6), the weakly oxidizing atmosphere is an inert gas to which H2O and CO2, which are relatively weakly oxidizing gases, are added, with the addition amount of H2O and CO2 being 5-20% by volume, and the graphite is oxidized at a high temperature.

[0026] In step 6), the modified graphite material is obtained, and relevant electrochemical performance tests are performed.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] The method for recycling waste lithium ion battery negative graphite according to the present application uses waste lithium battery negative graphite, which is a pressure filtration residue obtained by H2SO4-H2O2 leaching and pressure filtration of a positive and negative electrode powder mixture obtained by crushing and sorting of waste lithium ion batteries, and the main component of the pressure filtration residue is negative graphite. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a process flow diagram of the method for recycling waste lithium ion battery negative graphite according to the present application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present application clearer and more apparent, the present application will be further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0031] The specific embodiments of the present application will be further described below with reference to examples.

[0032] Embodiment 1

[0033] A method for recycling waste lithium-ion battery negative electrode graphite, comprising the following steps:

[0034] Step 1: The collected waste lithium-ion battery is crushed and sorted to obtain positive and negative electrode mixed powder;

[0035] Step 2: The positive and negative electrode mixed powder is immersed in H2SO4-H2O2, the positive electrode material is dissolved, the negative electrode material is not dissolved, and then the first pressure filtration is performed to obtain pressure filtration residue, and the water content of the obtained pressure filtration residue is 45%;

[0036] Step 3: The pressure filtration residue obtained in step 2 is first rinsed with pure water, the rinsing liquid pH is 3.5, then the second pressure filtration is performed after rinsing, the pressure filtration residue is analyzed and detected, and the main component is negative electrode graphite; the water content of the obtained pressure filtration residue is 43%;

[0037] Step 4: The negative electrode graphite obtained in step 3 is first dried at low temperature, the drying temperature is 80℃, the water content is 10%; then the residual organic matter is treated at high temperature, the temperature is 800℃, the high-temperature heat treatment time is 20min; after high-temperature treatment, cooling to room temperature, then cleaning to remove heavy metal ions, stopping cleaning when the cleaning liquid pH is 7, obtaining high-purity negative electrode graphite slurry after purification and impurity removal and cleaning;

[0038] Step 5: The high-purity negative electrode graphite slurry obtained in step 4 is further subjected to ultrasonic dispersion and drying, and the graphite material is obtained; the ultrasonic power is controlled at 100W; the drying is performed by spray drying;

[0039] Step 6: The graphite material obtained in step 5 is modified under high temperature and relatively weak oxidizing atmosphere; the temperature is 800℃, the high-temperature heat treatment time is 20min; CO2 gas is passed to maintain weak oxidizing property;

[0040] Step 7: The modified graphite material obtained in step 6 is subjected to related electrochemical performance test.

[0041] Embodiment 2

[0042] A method for recycling waste lithium-ion battery negative electrode graphite, comprising the following steps:

[0043] Step 1: The collected waste lithium-ion battery is crushed and sorted to obtain positive and negative electrode mixed powder;

[0044] Step 2: The positive and negative electrode mixed powder is immersed in H2SO4-H2O2, the positive electrode material is dissolved, the negative electrode material is not dissolved, and then the first pressure filtration is performed to obtain pressure filtration residue, and the water content of the obtained pressure filtration residue is 45%;

[0045] Step 3: The filter cake obtained in Step 2 is first rinsed with pure water, the rinsing liquid has a pH of 2.0, and after rinsing, secondary filtration is performed to obtain a filter cake for analysis and detection, which mainly contains negative electrode graphite; the filter cake obtained has a water content of 40%;

[0046] Step 4: The negative electrode graphite obtained in Step 3 is first dried at a low temperature of 120°C, with a water content of 8%; then the residual organic matter is treated at a high temperature of 900°C for 10 minutes; after high-temperature treatment, it is cooled to room temperature and then washed to remove heavy metal ions, and the washing is stopped when the washing liquid has a pH of 7, to obtain high-purity negative electrode graphite slurry after purification and impurity removal and washing;

[0047] Step 5: The high-purity negative electrode graphite slurry obtained in Step 4 is further subjected to ultrasonic dispersion and drying to obtain the graphite material; the ultrasonic power is controlled at 100W; and the drying is performed by spray drying;

[0048] Step 6: The graphite material obtained in Step 5 is modified at a high temperature and in an atmosphere with relatively weak oxidation; the temperature is 750°C, and the high-temperature treatment time is 30 minutes; CO2 gas is passed to maintain weak oxidation;

[0049] Step 7: The modified graphite material obtained in Step 6 is subjected to relevant electrochemical performance tests.

[0050] Example 3:

[0051] A method for recycling waste lithium ion battery negative electrode graphite, comprising the following steps:

[0052] Step 1: The collected waste lithium ion battery is crushed and sorted to obtain positive and negative electrode mixed powder;

[0053] Step 2: The positive and negative electrode mixed powder is subjected to H2SO4-H2O2 leaching, the positive electrode material is dissolved, the negative electrode material is not dissolved, and then a filter cake is obtained by primary filtration; the filter cake obtained has a water content of 45%;

[0054] Step 3: The filter cake obtained in Step 2 is first rinsed with pure water, the rinsing liquid has a pH of 3.5, and after rinsing, secondary filtration is performed to obtain a filter cake for analysis and detection, which mainly contains negative electrode graphite; the filter cake obtained has a water content of 43%;

[0055] Step 4: The negative electrode graphite obtained in step 3 is first dried at a low temperature of 100 DEG C, and the water content is 15%; then the residual organic matter is treated at a high temperature of 700 DEG C for 30 min; after high-temperature treatment, the temperature is cooled to room temperature, and then the heavy metal ions are removed by cleaning; the cleaning is stopped when the pH of the cleaning solution is 7, and the high-purity negative electrode graphite slurry after purification and impurity removal is obtained;

[0056] Step 5: The high-purity negative electrode graphite slurry obtained in step 4 is further subjected to ultrasonic dispersion and drying, and the graphite material is obtained; the ultrasonic power is controlled at 100 W; and the drying is performed by a spray drying method;

[0057] Step 6: The graphite material obtained in step 5 is modified at a high temperature and in an atmosphere with relatively weak oxidation; the temperature is 950 DEG C, and the high-temperature treatment time is 10 min; and CO2 gas is passed to maintain weak oxidation;

[0058] Step 7: The modified graphite material obtained in step 6 is subjected to related electrochemical performance tests.

[0059] The regeneration and utilization method of the waste lithium ion battery negative electrode graphite according to the application can achieve a removal rate of metal (nickel, cobalt, manganese, copper, aluminum, iron) impurities of more than 99.9%, and a removal rate of organic matter of 100%; the purity of the regenerated negative electrode graphite material is more than 99%, and the initial charge capacity and retention rate are 310 mAh / g and 98%, respectively.

[0060] Comparative test:

[0061] Comparative example 1:

[0062] According to the invention patent with publication No. CN110176647B, the waste lithium ion battery negative electrode material step-by-step utilization method is used for the waste lithium ion battery negative electrode material graphite negative electrode with a capacity retention rate of 50% to 75%; the stirring speed is 100-300 r / min, the leaching temperature is 25-65 DEG C, and the leaching time is 2-8 h;

[0063] The waste lithium ion battery negative electrode material step-by-step utilization method is used for the waste lithium ion battery negative electrode material graphite negative electrode with a capacity retention rate of 25% to 50%; the ultrasonic power is 100-500 W, the stirring speed during leaching is 50-300 r / min, the leaching temperature is 25-65 DEG C, and the leaching time is 1-6 h;

[0064] The waste lithium ion battery negative material gradient utilization method, for the waste lithium ion battery negative material graphite negative electrode with a capacity retention rate < 25%, the ultrasonic power is 300-1000W, the stirring speed in the leaching process is 50-300r / min, the leaching temperature is 25-85℃, and the leaching time is 1-6h;

[0065] The waste lithium ion battery negative material gradient utilization method, the water used in the leaching process is ultrapure water, pure water or deionized water, and the solid-liquid ratio S / L is 1:3-1:8g / ml.

[0066] The waste lithium ion battery negative material gradient utilization method, the acid used in the leaching process includes various strong polar acids: hydrochloric acid or sulfuric acid, and the acid concentration is controlled at 0.5-2.5mol / L.

[0067] The results show that:

[0068] According to the treatment method of the waste battery negative material in Example 1 of the invention patent with publication number CN110176647B, the waste lithium ion battery needs to be divided into 1-4 levels according to the capacity retention rate, and this section will consume a lot of time. When a large number of waste batteries are scrapped, this section will occupy a lot of test resources and manpower to continue to complete, and the efficiency is very low.

[0069] In Example 1, when treating the waste battery negative powder, the battery does not need to be classified, and compatible and efficient treatment can be achieved, and the treatment process is simple.

[0070] Comparative Example 2:

[0071] Referring to the invention patent with publication number CN115818618A, the method for regenerating waste lithium ion battery negative graphite, the acid leaching dry residue powder is mixed with alkali to obtain a mixed powder;

[0072] The mixed powder is calcined;

[0073] The calcined powder is subjected to multiple acid pickling and multiple water washing, and finally dried to obtain dry materials;

[0074] The dry materials are crushed, and the obtained powder and a sugar substance are added to a solvent, heated and stirred until the solvent is completely volatilized, and then the materials are dried to further remove the solvent inside the materials;

[0075] The above obtained materials are high-temperature calcined, the sugar substance is rapidly expanded by the generated gas to form a loose and porous structure, and the graphite is attached to the structure as a support;

[0076] The above obtained loose and porous materials are graphitized at high temperature to finally form a composite material of hard carbon and graphite.

[0077] The results show that:

[0078] According to the invention patent with publication number CN 115818618 A, the waste lithium ion battery negative electrode graphite in embodiment 1 needs to be mixed with alkali, which will consume a large amount of alkali solution in this step, increase the treatment cost, and subsequently need to be calcined, pickled and other steps for multiple times. In comparative example 2, the loose and porous bulk material is placed in a graphitization furnace to be graphitized at 2800 DEG C for 4h, which is extremely high in cost.

[0079] In embodiment 1, by controlling the water content of the filter cake to reduce the pickling frequency, the process flow is shortened and the cost is reduced. In embodiment 1, ultrasonic dispersion and spray drying are designed to prevent caking, and then a negative electrode material with good particle size and performance can be obtained through low-temperature calcination.

[0080] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled persons in the art, some improvements and changes can be made without departing from the inventive concept, which are within the protection scope of the present application.

Claims

1. A method for recycling spent lithium-ion battery negative electrode graphite, characterized in that: It comprises the following steps: ​ 1) crushing and sorting the collected waste lithium ion battery to obtain positive and negative mixed powder; 2) the positive and negative mixed powder obtained in the above step is leached by H2SO4-H2O2, the positive material is dissolved, the negative material is not dissolved, and then primary pressure filtration is carried out to obtain primary pressure filtration residue, and the water content of the primary pressure filtration residue is ensured to be ≤50%; 3) the primary pressure filtration residue obtained in the above step is rinsed, the pH of the solution after rinsing is controlled at 1-4, and then secondary pressure filtration is carried out, and the water content of the secondary pressure filtration residue is ensured to be ≤50%, to obtain secondary pressure filtration residue, and analysis and detection are carried out to determine that the main component of the secondary pressure filtration residue is negative graphite; the medium used for rinsing is selected from pure water or alkaline solution; 4) the secondary pressure filtration residue obtained in the above step is deeply purified and cleaned to remove impurities, dry, high-temperature impurity removal, multiple rinsing to remove acid and heavy metal ions are adopted until the pH of the graphite slurry is 6-8, and high-purity negative graphite slurry after purification, impurity removal and cleaning is obtained; the high-temperature impurity removal is controlled at a temperature of 700-900℃ and a time of 10-30min; the multiple rinsing to remove acid and heavy metal ions is to cool the material after high-temperature impurity removal, rinse after cooling to room temperature, multiple cleaning and multiple pressure filtration until the pH of the graphite slurry is 6-8, and then stop cleaning; 5) the high-purity negative graphite slurry obtained in the step is ultrasonically dispersed, the ultrasonic power is controlled at 100-200W, and the graphite material is obtained after drying; 6) the graphite material obtained in the above step is modified under high temperature and in an atmosphere keeping weak oxidizability, the temperature is controlled at 750-950℃, and the time is controlled at 10-30min, and the modified graphite material is obtained; The atmosphere keeping weak oxidizability is to add H2O and CO2 in inert gas, wherein the volume ratio of H2O and CO2 is 5-20%, and the graphite is oxidized at high temperature.

2. The method for recycling and utilizing waste lithium-ion battery negative electrode graphite according to claim 1, characterized in that: The drying in step 4) is low-temperature drying, the temperature is controlled at 80-120℃, and the water content of the dried material is controlled at 8-15%.

3. The method for recycling and utilizing waste lithium-ion battery negative electrode graphite according to claim 1, characterized in that: The modified graphite material obtained in step 6) is subjected to relevant electrochemical performance test.

Images