Retired lithium battery ternary material recovery method based on agricultural straw

Abstract

The invention discloses an agricultural straw-based retired lithium battery ternary material recovery method, which comprises: S1, mixing straw powder and a retired lithium battery positive electrode material, tabletting, carrying out anaerobic roasting, sequentially carrying out grinding, water immersion and filtration on the product, carrying out evaporative crystallization recovery on the filtrate to obtain a lithium carbonate solid, and drying the filter residue; s2, dissolving the filter residue with nitric acid, dissolving the recovered lithium carbonate solid, adding a lithium salt, adding citric acid after the dissolution is completed, dropwise adding ammonia water to adjust the pH value to be neutral, heating in a water bath, drying to form sol, heating, and continuously drying to form gel; and S3, carrying out high-temperature calcination, grinding the calcined product, washing with water, and carrying out vacuum drying to obtain the regenerated lithium battery positive electrode material. According to the method for recovering the retired lithium battery ternary material based on the agricultural straws, the lithium recovery rate in the positive electrode material of the retired lithium battery is greater than or equal to 90%; the regenerated lithium battery has excellent performance and meets the reuse performance requirement.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a method for recycling ternary materials of retired lithium batteries based on agricultural straw. Background Art

[0002] With the continuous development of science and technology, lithium batteries are being used more and more widely. However, due to the service life of lithium batteries, the number of retired lithium batteries due to retirement or other reasons is increasing. Retired lithium batteries, especially nickel-cobalt-manganese (Ni, Co, Mn, referred to as NCM) ternary lithium batteries, contain a large amount of non-renewable metals such as lithium, nickel, cobalt, and manganese. Improper disposal will not only cause environmental pollution, but also cause a large amount of resource waste. Therefore, recycling these metals is of vital importance.

[0003] The method of using carbon thermal reduction method to react retired lithium battery positive electrode materials with agricultural straw to achieve preferential and efficient recovery of lithium batteries has not been reported in the field of recycling retired lithium batteries. Although many methods for recycling retired lithium battery materials have been proposed in the prior art, in general, the recycling efficiency of the prior art is not ideal enough. Summary of the invention

[0004] In view of the shortcomings of the above-mentioned technology, the present invention provides a method for recycling ternary materials of retired lithium batteries based on agricultural straw to solve the problems of low recovery efficiency of positive electrode materials of existing retired lithium batteries and low performance of regenerated lithium batteries.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A method for recycling ternary materials of retired lithium batteries based on agricultural straw, the recycling method comprising the following steps:

[0007] S1: A certain amount of straw powder is mixed with retired lithium battery positive electrode materials, and the tablets are pressed, and then placed in a tubular furnace for oxygen-free roasting for carbon thermal reduction reaction, the roasted product is taken out for grinding, and then the roasted product is soaked in water with a certain solid-liquid ratio, and then filtered after soaking for a certain period of time, and the filtrate is evaporated and crystallized to recover lithium carbonate solid, and the filter residue is dried;

[0008] S2: dissolving the filter residue dried in step S1 with a certain concentration of nitric acid at room temperature, dissolving the lithium carbonate solid recovered in step S1, and adding a small amount of lithium salt, adding a certain amount of citric acid after the dissolution is completed, and then dropping ammonia water to adjust the pH to neutral, while heating in a water bath and magnetic stirring, drying to form a sol, and then placing in a 120°C oven to dry overnight to form a gel;

[0009] The gel obtained in step S2 is placed in a muffle furnace for medium-temperature pre-sintering and high-temperature calcining in steps. The calcined product is ground, washed with water, and vacuum-dried to obtain a regenerated lithium battery positive electrode material.

[0010] As a preferred technical solution, the straw powder is at least one of rice straw, corn straw, and soybean straw, and is not limited to the above three types of straw.

[0011] As a preferred technical solution, the retired lithium battery positive electrode material is a retired nickel-cobalt-manganese ternary lithium battery positive electrode material.

[0012] As a preferred technical solution, the positive electrode material of the nickel-cobalt-manganese ternary lithium battery is LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O 2、 LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 At least one of O2, and not limited to the above four components.

[0013] As a preferred technical solution, in step S1, the roasting condition is that the ratio of straw powder to retired lithium battery positive electrode material raw material is 0.8 to 2:1.

[0014] As a preferred technical solution, in step S1, the reaction temperature of the calcination operation is 670-740°C, and the insulation time is 0.5-1.5h.

[0015] As a preferred technical solution, in step S2, after adding a small amount of lithium salt, the molar ratio of Li:NCM is controlled to be 1.05-1.15:1.

[0016] As a preferred technical solution, in step S2, the molar ratio of citric acid to the total amount of Li and NCM is 1.5 to 3:1.

[0017] As a preferred technical solution, in step S3, the pre-firing temperature in the muffle furnace is 300-450°C, the pre-firing time is 4-6 hours, the high-temperature calcination temperature is 700-900°C, and the calcination time is 10-15 hours.

[0018] The present invention utilizes the reducing products generated by pyrolysis of agricultural straw in an oxygen-free environment and the positive electrode materials (LiNi 1-x-y Co x Mn yFor the carbon thermal reduction reaction of LiNixCoyMn1 - x - yO2 (abbreviated as LNCMO, where 0 < x < 1 and 0 < y < 1), the oxygen atoms in the cathode material of retired lithium batteries can combine with the reducing substances after the pyrolysis of straw powder, and Ni, Co, and Mn are reduced from high valence states to low valence states or even elemental states. Specifically, the transition metal oxides in the cathode material of retired lithium batteries of the present invention can promote the pyrolysis of agricultural straw, while the reducing atmosphere generated by the pyrolysis of agricultural straw helps the lattice collapse of the cathode material of lithium batteries, promoting the carbon thermal reduction process of the cathode material of retired lithium batteries. After the carbon thermal reduction reaction, the cathode material changes from an ellipsoidal shape with uniform and smooth particles to a rough surface, with many holes and cracks, particle adhesion, and a large number of graphite carbon layers. After the NCM ruptures, the lattice collapses, and the gas generated by the reduction reaction between the metal and carbon escapes from the lattice. After the cathode material obtained by carbon thermal reduction of the present invention is ground and water-leached, lithium exists in the filtrate in the form of lithium carbonate, and an aqueous solution of lithium carbonate is obtained by simple filtration; while nickel, cobalt, and manganese in the cathode material of retired lithium batteries exist in the filter residue in the form of Co, Ni, and MnO. Further, first, the Li2CO3 powder generated by evaporation and crystallization of the filtrate is mixed with the acid-treated filter residue, and then through the sol-gel method and the step-by-step high-temperature calcination method in sequence, a recycled cathode material for lithium batteries is obtained; the recycling method of the present invention not only realizes the efficient recycling of lithium elements in the cathode material of retired lithium batteries, but also can prepare and assemble a ternary lithium battery with performance similar to that of commercial NCM ternary lithium-ion batteries.

[0019] Advantages of the present invention:

[0020] The method for recycling ternary materials of retired lithium batteries based on agricultural straw of the present invention has a relatively high efficiency (greater than or equal to 90%) in selectively recycling Li, relatively simple operation, a short preparation cycle, uses the ubiquitous agricultural straw as a catalyst, has a low cost, controllable synthesis conditions, and has the potential for large-scale preparation.

[0021] The recycled cathode material for lithium batteries obtained by the present invention has good discharge stability, and its rate performance is also close to that of lithium-ion batteries prepared from commercial NCM. After experiencing a discharge rate of 0.2C, the initial discharge capacity is greater than or equal to 170 mAh / g, and the Coulomb efficiency of the first cycle is greater than or equal to 90%. The recycling method of the present invention has broad development prospects. The method of the present invention is simple and has good economic benefits.

[0022] The recycling and reuse of the ternary materials of retired lithium batteries of the present invention not only alleviates the environmental pollution caused by waste lithium batteries, but also effectively utilizes the abundant metal elements in waste lithium batteries, reducing the economic pressure of imports. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the carbon thermal reduction reaction and water-leaching treatment process of the cathode material powder of retired lithium batteries;

[0024] Figure 2 This is an XRD comparison diagram of the retired lithium battery positive electrode material raw material, the calcined product, and the filter residue after water immersion treatment in Example 1 of the present invention;

[0025] Figure 3 This is a comparison chart of lithium leaching efficiency obtained under the roasting conditions of Example 1 of the present invention, where the mass ratio of corn straw powder to retired lithium battery positive electrode material powder is 1:1, the roasting reaction temperature is 700° C., and the holding time is 1 h, and other different roasting conditions;

[0026] Figure 4 This is an XRD comparison diagram of the recycled lithium battery positive electrode material recovered at a calcination temperature of 900° C. and other different calcination temperatures in Example 1 of the present invention;

[0027] Figure 5 This is the first cycle charge and discharge diagram of the ternary lithium battery assembled using the recycled lithium battery positive electrode material of Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0029] Example 1

[0030] This embodiment is based on the method for recycling ternary materials of retired lithium batteries from agricultural straw, such as Figure 1 As shown, the recovery method comprises the following steps:

[0031] S1: 1g corn stalk powder and 1g retired lithium battery positive electrode material powder (retired lithium battery positive electrode material is composed of LiNi with a mass ratio of 0.43:0.18:0.39) 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2 and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 composition) are fully ground and mixed, and then pressed into a sheet in a mold and placed in a crucible, and then placed in a tube furnace, nitrogen is introduced at an intake rate of 30ml / min for oxygen-free roasting to perform carbon thermal reduction reaction. The heating rate of the roasting operation is 4℃ / min, and the roasting reaction temperature ( Figure 3a) is 700°C, and the heat preservation time is 1h; after the reaction is completed, the calcined product is cooled and taken out for grinding, and then the calcined product is soaked in water at a certain solid-liquid ratio (the solid-liquid ratio of the solid phase of the calcined product to the liquid phase water is 1:30), and then filtered after soaking for 2h, and the filtrate is evaporated and crystallized to recover lithium carbonate solid, and the filter residue is dried.

[0032] S2: Dissolve the dried residue from step S1 with 1 mol / L nitric acid at room temperature while performing magnetic stirring; then add Ni(NO3)2·6H2O and Co(NO3)2·6H2O according to the final component ratio, so that the atomic ratio of nickel, cobalt and manganese reaches 0.6:0.2:0.2, and then dissolve the lithium carbonate solid recovered from step S1, and add a small amount of lithium salt to control the molar ratio of Li:NCM to 1.05:1 (i.e., the molar amount of Li element to NCM is 1.05:1). After the dissolution is completed, a certain amount of citric acid is added as a complexing agent, and the molar ratio of the citric acid to the total amount of Li and NCM is 2:1 (that is, the ratio of the molar amount of citric acid to the total molar amount of Li, Ni, Co, and Mn is 2:1), and then ammonia water is added dropwise to adjust the pH to neutral, and at the same time, heating in a water bath at 85°C and magnetic stirring are performed to dry to form a sol, and then placed in an oven at 120°C to dry overnight to form a gel;

[0033] S3: The gel obtained in step S2 is placed in a muffle furnace, first pre-fired at 450°C for 5 hours, then calcined at 900°C for 12 hours, the calcined product is cooled to room temperature and then ground, the lithium salt water therein is washed clean, and then dried in a vacuum drying oven at 120°C to obtain the regenerated lithium battery positive electrode material.

[0034] The test results show that the recovery rate of lithium in the retired lithium battery positive electrode material reaches 95.8%. Figure 2 It can be seen that there is a Li2CO3 peak in the retired lithium battery raw materials, a Li2CO3 peak is produced in the calcined product after the carbon thermal reduction reaction, and the Li2CO3 peak disappears in the filter residue after water immersion, indicating that the carbon thermal reduction method combined with water immersion treatment can effectively recover the lithium element in the retired lithium battery positive electrode material. Figure 3 (a, b) are the lithium leaching efficiencies under different roasting conditions. Figure 3 It can be seen that the lithium leaching efficiency is highest under the calcination conditions of a mass ratio of corn straw powder to retired lithium battery positive electrode material powder of 1:1, a calcination reaction temperature of 700°C, and a holding time of 1h. Figure 4The X-ray diffraction (XRD) of recycled lithium battery positive electrode materials (or recycled ternary positive electrode materials) prepared at different calcination temperatures. As can be seen from the figure, the recycled materials were prepared into LiNi by the sol-gel method. 0.6 Co 0.2 Mn 0.2 The pure phase of O2, and when calcined at 900℃ in a muffle furnace, the phase structure peaks are most obvious.

[0035] The positive electrode material (0.8g), acetylene black and polyvinylidene fluoride (PVDF) were prepared into a positive electrode mixture in a weight ratio of 8:1:1; the mixture was then added to 3g N-methylpyrrolidone (NMP) and stirred for 6h, the prepared slurry was coated on aluminum foil, and finally vacuum dried at 120℃ for 24h. The dried electrode was pressed at 9MPa, and its loading was 3.2mg / cm; it was assembled into a button-type lithium battery with other lithium battery materials, such as separator, negative electrode material and battery shell (all purchased from commercial channels).

[0036] The test results show that if Figure 5 As shown, the battery exhibits good performance. After experiencing a discharge rate of 0.2C, the first-cycle discharge capacity reaches 172.3mAh / g, and the first-cycle coulombic efficiency reaches 91%, which is close to the performance of lithium-ion batteries prepared by commercial NCM.

[0037] Comparative Example 1

[0038] This control example is a method for recycling ternary materials of retired lithium batteries based on agricultural straw. The specific steps of the recycling method are basically the same as those in Example 1. The difference is that the retired lithium battery positive electrode materials in the recycling method of this control example are not processed in step S1.

[0039] The test results show that the recovery rate of lithium in the retired lithium battery positive electrode material is 78.5%.

[0040] The recycled lithium battery positive electrode material obtained in Control Example 1 was prepared into a positive electrode mixture according to the raw material composition of Example 1, and then assembled into a lithium battery, and the battery performance test was carried out under the same conditions. The test results show that after the battery has undergone a 0.2C discharge rate, the first cycle discharge capacity reaches 147.1mAh / g, and the first cycle coulomb efficiency reaches 80.6%.

[0041] Comparative Example 2

[0042] This control example is a method for recycling ternary materials of retired lithium batteries based on agricultural straw. The specific steps of the recycling method are basically the same as those in Example 1. The difference is that the retired lithium battery positive electrode materials in the recycling method of this control example are not subjected to the water immersion treatment in step S1.

[0043] The test results show that the recovery rate of lithium in the retired lithium battery positive electrode material is 85.3%.

[0044] The recycled lithium battery positive electrode material obtained in Control Example 1 was prepared into a positive electrode mixture according to the raw material composition of Example 1, and then assembled into a lithium battery, and the battery performance test was carried out under the same conditions. The test results show that after the battery has undergone a 0.2C discharge rate, the first cycle discharge capacity reaches 157.3mAh / g, and the first cycle coulomb efficiency reaches 83.6%.

[0045] Comparative Example 3-5

[0046] Control Example 3-5 is a method for recycling ternary materials of retired lithium batteries based on agricultural straw. The specific steps of the recycling method are basically the same as those of Example 1. The difference is that in the recycling method of Control Example 3-5, the retired lithium battery positive electrode material is subjected to carbon thermal reduction reaction at roasting reaction temperatures of 600°C, 800°C, and 900°C, respectively.

[0047] The test results show that the lithium recovery rates in the retired lithium battery positive electrode materials of control examples 3-5 are 65.3%, 84.7% and 80.2% respectively.

[0048] The recycled lithium battery positive electrode materials obtained in control examples 3-5 were respectively proportioned into positive electrode mixtures according to the raw material composition of Example 1, and then assembled into lithium batteries, and the battery performance test was carried out under the same conditions. The test results show that after the battery samples of control examples 3-5 experienced a 0.2C discharge rate, the first cycle discharge capacity was 154.5mAh / g, 163.6mAh / g, and 161.8mAh / g, respectively, and the first cycle coulomb efficiency was 70.3%, 85.6%, and 80.1%, respectively.

[0049] Example 2

[0050] The present embodiment is a method for recycling ternary materials of retired lithium batteries based on agricultural straw. The specific steps of the recycling method are basically the same as those of Example 1. The difference is that in the recycling method of the present embodiment, rice straw powder is used instead of corn straw powder.

[0051] The test results show that the recovery rate of lithium in the retired lithium battery positive electrode material reaches 94.3%.

[0052] The recycled lithium battery positive electrode material obtained in Example 2 was prepared into a positive electrode mixture according to the raw material composition of Example 2, and then assembled into a lithium battery, and the battery performance test was carried out under the same conditions. The test results show that after the battery has undergone a 0.2C discharge rate, the first cycle discharge capacity reaches 170.8mAh / g, and the first cycle coulomb efficiency reaches 90.5%.

[0053] Example 3

[0054] The present embodiment is a method for recycling ternary materials of retired lithium batteries based on agricultural straw. The specific steps of the recycling method are basically the same as those of Example 1. The difference is that in the recycling method of the present embodiment, soybean straw powder is used instead of corn straw powder.

[0055] The test results show that the recovery rate of lithium in the retired lithium battery positive electrode material reaches 92.5%.

[0056] The recycled lithium battery positive electrode material obtained in Example 3 was prepared into a positive electrode mixture according to the raw material composition of Example 3, and then assembled into a lithium battery, and the battery performance test was carried out under the same conditions. The test results show that after the battery has undergone a 0.2C discharge rate, the first cycle discharge capacity reaches 171.5mAh / g, and the first cycle coulomb efficiency reaches 91%.

[0057] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. A method for recycling ternary materials of retired lithium batteries based on agricultural straw, characterized in that: The recovery method comprises the following steps: S1: A certain amount of straw powder is mixed with retired lithium battery positive electrode materials, and the tablets are pressed, and then placed in a tubular furnace for oxygen-free roasting for carbon thermal reduction reaction, the roasted product is taken out for grinding, and then the roasted product is soaked in water with a certain solid-liquid ratio, and then filtered after soaking for a certain period of time, and the filtrate is evaporated and crystallized to recover lithium carbonate solid, and the filter residue is dried; S2: dissolving the filter residue dried in step S1 with a certain concentration of nitric acid at room temperature, dissolving the lithium carbonate solid recovered in step S1, and adding a small amount of lithium salt, adding a certain amount of citric acid after the dissolution is completed, and then dropping ammonia water to adjust the pH to neutral, while heating in a water bath and magnetic stirring, drying to form a sol, and then placing in a 120°C oven to dry overnight to form a gel; S3: placing the gel obtained in step S2 in a muffle furnace for medium-temperature pre-sintering and high-temperature calcining in steps, grinding, washing and vacuum drying the calcined product to obtain a regenerated lithium battery positive electrode material.

2. The method for recycling ternary materials of retired lithium batteries based on agricultural straw as claimed in claim 1, characterized in that: The straw powder is at least one of rice straw, corn straw and soybean straw, and is not limited to the above three types of straw.

3. The method for recycling ternary materials of retired lithium batteries based on agricultural straw as claimed in claim 1, characterized in that: The retired lithium battery positive electrode material is a retired nickel-cobalt-manganese ternary lithium battery positive electrode material.

4. The method for recycling ternary materials of retired lithium batteries based on agricultural straw as claimed in claim 3, characterized in that: The positive electrode material of the nickel-cobalt-manganese ternary lithium battery is LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O 2、 LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 At least one of O2, and not limited to the above four components.

5. The method for recycling ternary materials of retired lithium batteries based on agricultural straw as claimed in claim 1, characterized in that: In step S1, the roasting condition is that the ratio of straw powder to retired lithium battery positive electrode material raw material is 0.8 to 2:

1.

6. The method for recycling ternary materials of retired lithium batteries based on agricultural straw as claimed in claim 1, characterized in that: In step S1, the reaction temperature of the calcination operation is 670-740°C, and the holding time is 0.5-1.5h.

7. The method for recycling ternary materials of retired lithium batteries based on agricultural straw as claimed in claim 1, characterized in that: In step S2, a small amount of lithium salt is added to control the molar ratio of Li:NCM to be 1.05-1.15:

1.

8. The method for recycling ternary materials of retired lithium batteries based on agricultural straw as claimed in claim 1, characterized in that: In step S2, the molar ratio of the citric acid to the total amount of Li and NCM is 1.5 to 3:

1.

9. The method for recycling ternary materials of retired lithium batteries based on agricultural straw as claimed in claim 1, characterized in that: In step S3, the pre-firing temperature in the muffle furnace is 300-450° C., the pre-firing time is 4-6 hours, the high-temperature calcination temperature is 700-900° C., and the calcination time is 10-15 hours.

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