A method for recycling the positive electrode material of waste lithium batteries

Abstract

The present invention provides a method for regenerating the cathode material of waste lithium batteries, belonging to the technical field of lithium-ion battery regeneration and recycling. The method comprises the following steps: S1: Adding an acid to the cathode material of waste lithium batteries, carrying out a selective lithium extraction reaction at 160-240 °C, separating to obtain a filtrate and a filter residue 1, wherein the filter residue 1 is a nickel-cobalt-manganese compound, and the filtrate is a lithium salt solution; S2: Mixing a lithium source 1, a transition metal source, and an additive solution to obtain a mixed solution 1, then mixing with the filter residue 1 obtained in S1 and carrying out a hydrothermal reaction, and separating the reaction product to obtain a filter residue 2 and a filtrate; S3: Ball-milling the filter residue 2 obtained in S2 with a lithium source 2, and calcining the obtained mixture to obtain a regenerated cathode material for lithium batteries. The present invention selectively leaches lithium, eliminates the lithium-nickel mixing defect in the waste cathode material; at the same time, retains the crystal structure and morphology of the cathode material; and repairs the defects of the waste cathode material through hydrothermal lithium supplementation-calcination treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery recycling and regeneration, and particularly relates to a method for regenerating the cathode material of used lithium batteries. Background Art

[0002] Lithium-ion batteries are widely used in new energy vehicles, 3C, and energy storage fields due to their advantages such as high energy density, recyclability, high environmental friendliness, and portability. Currently, the new energy vehicle industry with the largest installed capacity of lithium-ion batteries is developing rapidly, which has driven the rise of the lithium-ion battery industry. Due to the increasing demand for lithium-ion batteries, the lithium, nickel, cobalt, and manganese resources widely required for the preparation of lithium-ion batteries will gradually become in short supply. To alleviate the resource pressure, recycling the reusable resources from used lithium-ion batteries is an effective way.

[0003] The cathode assembly enriches most of the valuable resources of used lithium-ion batteries, mainly because the metal materials such as lithium, nickel, cobalt, and manganese in it have high value. The cathode material has high recycling value due to its rich metal elements. The traditional wet recycling technology follows the process of acid leaching, purification, and extraction / precipitation. This technology uses a large amount of acids and alkalis, and a large amount of waste liquid is discharged. In addition, due to the long steps, the lithium recovery rate is usually lower than 70%. In addition to the wet recycling process, the direct regeneration technology of the cathode has also attracted the attention of researchers. Usually, the defects of used cathodes are repaired through hydrothermal lithium supplementation and calcination processes. Although this process replenishes the missing lithium and reconstructs the defective grain structure, the used cathodes usually have lithium / nickel mixing defects, and these defects cannot be completely repaired by traditional direct regeneration technology. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for regenerating the cathode material of used lithium batteries.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: to provide a method for regenerating the cathode material of used lithium batteries, including the following steps:

[0006] S1: Add acid to the cathode material of used lithium batteries, carry out a selective lithium extraction reaction at 160 - 240 °C, and separate to obtain a filtrate and filter residue 1. The filter residue 1 is a nickel-cobalt-manganese compound, and the filtrate is a lithium salt solution;

[0007] S2: Mix lithium source 1, transition metal source, and additive solution to obtain mixture 1, then mix it with the filter residue 1 obtained in S1 and carry out a hydrothermal reaction. The reaction product is separated to obtain filter residue 2 and a filtrate;

[0008] S3: Ball mill the filter residue 2 obtained in S2 with lithium source 2, and calcine the obtained mixture to obtain the regenerated cathode material of the lithium battery;

[0009] Among them, the molar ratio of H in the acid described in step S1 + to Li in the cathode material of the waste lithium battery is 0.9 - 1.1:1.

[0010] Preferably, the molar ratio of H in the acid + to Li in the cathode material of the waste lithium battery is 1:1.

[0011] Preferably, in step S1, the temperature of the selective lithium extraction reaction is 180 - 220 °C.

[0012] In the present invention, by adding an acid to the cathode material of the waste lithium battery to carry out a selective lithium extraction reaction, lithium in the cathode material of the waste lithium battery is completely extracted. The reaction products are a lithium salt solution and nickel cobalt manganese precipitate (filter residue 1). The chemical formula of the cathode material of the waste lithium battery in the present invention is Li(Ni x Co y Mn z )O2, where x + y + z = 1; the composition of filter residue 1 is H(Ni x Co y Mn z )O2, where x + y + z = 1; Li in the cathode material of the waste lithium battery + is selectively replaced by H + , eliminating the lithium / nickel mixing defect existing in the waste cathode material; the obtained filter residue 1 is then subjected to hydrothermal lithium supplementation and calcination treatment. This method maximally repairs the defects existing in the cathode material of the waste lithium battery. The electrochemical performance of the regenerated cathode material is equivalent to that of the newly prepared cathode material, and the lithium salt solution can be transferred to other processes for recovery treatment.

[0013] Traditional cathode materials are usually prepared by co-precipitation method to obtain precursor materials with uniform particle size. The morphology of the obtained cathode material is spherical particles with closely packed primary particles. The morphology of the cathode material significantly affects the electrochemical performance of the cathode material. In the present invention, through the selective lithium extraction reaction, not only can lithium in the cathode material of the waste lithium battery be completely removed, but also the lattice space group of the cathode material of the waste lithium battery can be retained as R3 - m, and the morphology of the cathode material of the waste lithium battery can be maintained as spherical particles with closely packed primary particles, greatly improving the electrochemical performance of the regenerated cathode material of the lithium battery.

[0014] The waste cathode material used in the present invention can be obtained from retired ternary, quinary, octal, and any other series of ternary lithium-ion batteries. The ternary, quinary, and octal series are judged according to the nickel element content in the cathode of the lithium-ion battery, that is, corresponding to Li(Ni x Co y Mn z )O2 with x values of 30%, 50%, and 80% in the content, and this ratio is the most common in commercial lithium batteries.

[0015] The chemical equation involved in step S1 is: H + +Li(Ni x Co y Mn z )O2 = Li + +H(Ni x Co y Mn z )O2.

[0016] In the present invention, the addition amount of H + and the temperature of the selective lithium extraction reaction are important parameters affecting the selective lithium extraction reaction; if the addition amount of H + is too small, the lithium in the cathode material of waste lithium batteries cannot be completely replaced; if the addition amount of H + is too large, the morphology of the cathode material of waste lithium batteries will be damaged, resulting in a decrease in the electrochemical performance of the regenerated cathode material; if the temperature of the selective lithium extraction reaction is too low or too high, the leaching effect of lithium will be affected. In addition, the inventor found that when the temperature of the selective lithium extraction reaction is 160 - 240 °C, no other substances except acid need to be added, and the lithium in the cathode material of waste lithium batteries can be leached out to the maximum extent. Preferably, the temperature of the selective lithium extraction reaction is 180 - 220 °C, and at 180 - 220 °C, the lithium content in the obtained filter residue 1 is less.

[0017] Preferably, in step S1, the liquid-solid ratio of the selective lithium extraction reaction is 1 - 20 mL / g.

[0018] The liquid-solid ratio of the selective lithium extraction reaction will affect the leaching effect of lithium. If the liquid-solid ratio is too small or too large, the leaching time of lithium is long, the efficiency is low, and the leaching rate is low; preferably, when the liquid-solid ratio of the selective lithium extraction reaction is 1 - 10 mL / g, the lithium extraction effect is the best.

[0019] Preferably, in step S1, the acid is at least one of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, and citric acid.

[0020] In the present invention, by analyzing the component content of filter residue 1, an appropriate amount of lithium salt and transition metal source are supplemented, and the ratio of the lithium salt and the transition metal source is adjusted to be consistent with the ratio of the target product, and then a hydrothermal reaction is carried out; selecting water-soluble lithium salt and water-soluble transition metal source is beneficial to the progress of the hydrothermal reaction.

[0021] Preferably, the lithium source 1 and the lithium source 2 are at least one of lithium sulfate, lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, and lithium acetate.

[0022] Preferably, the lithium source 1 and the lithium source 2 are at least one of lithium hydroxide and lithium carbonate; when the lithium source 1 and the lithium source 2 are at least one of lithium hydroxide and lithium carbonate, it is beneficial to supplement the lacking lithium in filter residue 1.

[0023] Preferably, in step S2, the transition metal source is at least one of a nickel source, a cobalt source, and a manganese source.

[0024] Preferably, the nickel source is at least one of nickel sulfate (NiSO4), nickel carbonate (NiCO3), nickel hydroxide (Ni(OH)2), nickel oxide (NiO), and nickel oxalate (NiC2O4); more preferably, the nickel source is at least one of nickel carbonate and nickel hydroxide.

[0025] Preferably, the cobalt source is at least one of cobalt sulfate (CoSO4), cobalt carbonate (CoCO3), cobalt hydroxide (Co(OH)2), cobalt oxide (CoO), and cobalt oxalate (CoC2O4); more preferably, the cobalt source is at least one of cobalt carbonate and cobalt hydroxide.

[0026] Preferably, the manganese source is at least one of manganese sulfate (MnSO4), manganese carbonate (MnCO3), manganese hydroxide (Mn(OH)2), manganese dioxide (MnO2), and manganese oxalate (MnC2O4); more preferably, the manganese source is at least one of manganese carbonate and manganese hydroxide.

[0027] Preferably, in step S2, the additive is at least one of a primary n-carbon alcohol with less than 12 carbon atoms, ethylene glycol, glycerol, ethylene, and hydrogen peroxide. Preferably, the primary n-carbon alcohol with less than 12 carbon atoms is ethanol.

[0028] In step S2, the additive plays a role in activating the surface of the filter residue 1 in the hydrothermal reaction, inducing rapid lithiation of the filter residue 1, and ensuring that the morphology and crystal structure of the filter residue 1 do not change during the hydrothermal reaction.

[0029] Preferably, in step S2, at least one of the following (a)-(f):

[0030] (a) The molar ratio of lithium in the lithium source 1 to the transition metal in the filter residue 1 is 1-6:1;

[0031] (b) The molar ratio of the transition metal source to the transition metal in the filter residue 1 is 0.01-1:1;

[0032] The addition amounts of the lithium source 1 and the transition metal source are determined according to the components in the filter residue 1. Preferably, the molar ratio of lithium in the lithium source 1 to the transition metal in the filter residue 1 is 1.2-6:1; the molar ratio of the transition metal source to the transition metal in the filter residue 1 is 0.01-0.6:1.

[0033] (c) The volume concentration of the additive in the mixed solution 1 is 1-15%;

[0034] (d) The temperature of the hydrothermal reaction is 100 - 240 °C;

[0035] (e) The time of the hydrothermal reaction is 1 - 24 h;

[0036] (f) The liquid-solid ratio of the filter residue 1 to the mixed liquid 1 is 1 - 20 mL / g.

[0037] By controlling the parameters of the hydrothermal reaction, filter residue 2 with better electrochemical performance is obtained. Preferably, the temperature of the hydrothermal reaction is 100 - 180 °C; the time of the hydrothermal reaction is 12 - 18 h; the liquid-solid ratio of the filter residue 1 to the mixed liquid 1 is 1 - 10 mL / g.

[0038] Preferably, in step S3, at least one of the following (a)-(f):

[0039] (a) The addition amount of the lithium source 2 is 5 - 15% of the mass of the filter residue 2; the purpose of adding the lithium source 2 is to compensate for the lithium loss of the filter residue 2 during the calcination process.

[0040] In order to reduce the impurities of the filter residue 2, when collecting the filter residue 2, it is washed with a solvent, and the solvent is deionized water or ethanol.

[0041] (b) The ball-to-material ratio of the ball milling is 5 - 50:1;

[0042] (c) The time of the ball milling is 0.1 - 12 h;

[0043] By controlling the time and ball-to-material ratio of the ball milling, the lithium source 2 and the filter residue 2 are mixed evenly, avoiding uneven distribution of lithium in the regenerated cathode material caused by uneven dispersion of the lithium source 2 during the calcination process, which leads to a decrease in the electrochemical performance of the regenerated cathode material.

[0044] The ball milling of the present invention can be wet milling or dry milling, and the reagent for the wet milling is at least one of ultrapure water, ethanol, and ethylene glycol.

[0045] (d) The atmosphere for the calcination is at least one of air and oxygen; preferably, the atmosphere for the calcination is oxygen;

[0046] (e) The temperature of the calcination is 750 °C - 950 °C; for different cathode materials, preferably the calcination temperature is different. When the regenerated cathode material is a high-nickel cathode material (Ni content is not less than 0.6), preferably the calcination temperature is 800 - 900 °C; when the regenerated cathode material is a low-nickel cathode material (Ni content is less than 0.6), the preferred calcination temperature is 850 °C - 950 °C.

[0047] (f) The time of the calcination is 12 °C - 36 h; preferably, the time of the calcination is 18 - 24 h.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0049] (1) By selecting a specific reaction temperature and H + content, lithium is selectively leached without the need to additionally add other auxiliaries, eliminating the lithium-nickel mixing defect in the waste cathode material; meanwhile, the crystal structure and morphology of the cathode material are retained.

[0050] (2) Through hydrothermal lithium supplementation-calcination treatment, the lithium deficiency and structural cracking defects of the waste cathode material are repaired, and a regenerated cathode material with electrochemical performance equivalent to that of the newly prepared cathode material is obtained.

[0051] (3) The process flow of the present invention is simple, realizing the comprehensive recycling of the waste battery cathode material. Description of the Drawings

[0052] Figure 1 Scanning electron microscope images of the filter residue 1 obtained in Example 1, the regenerated cathode material, and the cathode materials obtained in Comparative Examples 1-3, where a is the filter residue 1 obtained in Example 1, b is the regenerated cathode material obtained in Example 1, c is the cathode material obtained in Comparative Example 1, d is the regenerated cathode material obtained in Comparative Example 2, and e is the regenerated cathode material obtained in Comparative Example 3;

[0053] Figure 2 Cyclic charge and discharge performance diagrams of the cathode materials obtained in Example 1 and Comparative Example 1. Detailed Embodiments

[0054] To better illustrate the purpose, technical solutions, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments and the drawings.

[0055] Example 1

[0056] This example provides a method for regenerating a waste lithium battery cathode material, including the following steps:

[0057] S1: 10 g of the waste ternary lithium battery cathode material is subjected to a hydrothermal reaction with a H2SO4 solution containing 0.05 mol at a liquid-solid ratio of 10 mL / g at 200 °C, where the molar ratio of H + to lithium in the waste lithium battery cathode material is 1:1. After reacting for 18 h, the filter residue 1 and the filtrate 1 are separated, and the chemical composition of the filter residue 1 is shown in Table 1;

[0058] S2: In order to synthesize the target composition of Li(Ni 0.3 Co 0.3 Mn 0.3)The positive electrode material of O2. Add 9 g of the filter residue 1 obtained in S1 to a solution containing 5 g of lithium carbonate, 0.13 g of nickel hydroxide, 0.3 g of cobalt hydroxide, 0.34 g of manganese hydroxide, and 1 vol.% ethylene at a liquid-solid ratio of 10 mL / g. After mixing evenly, carry out a hydrothermal reaction at 100 °C. After reacting for 24 h, wash the separated precipitate with deionized water and dry it to obtain filter residue 2;

[0059] S3: Mechanically ball-mill the filter residue 2 obtained in S2, 0.7 g of lithium carbonate, and 10 mL of pure water for 0.1 h. The ball-to-material ratio of the mechanical ball milling is 5:1. Calcinate the obtained mixture at 950 °C in an air atmosphere for 12 h to obtain the recycled positive electrode material.

[0060] Example 2

[0061] This example provides a method for recycling the positive electrode material of waste lithium batteries, including the following steps:

[0062] S1: Carry out a hydrothermal reaction on 10 g of the positive electrode material of waste eight-series ternary lithium batteries at a liquid-solid ratio of 1 mL / g with a H2SO4 solution containing 0.05 mol at 200 °C. Among them, H + The molar ratio to lithium in the positive electrode material of waste lithium batteries is 1:1. After reacting for 18 h, separate to obtain filter residue 1 and filtrate 1. The chemical composition of the filter residue 1 is shown in Table 1;

[0063] S2: In order to synthesize the positive electrode material with the target composition of Li(Ni 0.8 Co 0.1 Mn 0.1 )O2, add 9 g of the filter residue 1 obtained in S1 to a solution containing 5.5 g of lithium carbonate, 4 g of nickel sulfate, 0.2 g of cobalt sulfate, 0.1 g of manganese sulfate, and 8 vol.% ethylene glycol at a liquid-solid ratio of 1 mL / g. After mixing evenly, carry out a hydrothermal reaction at 240 °C. After reacting for 1 h, wash the separated precipitate with deionized water and dry it to obtain filter residue 2;

[0064] S3: Mechanically ball-mill the filter residue 2 obtained in S2, 2 g of lithium carbonate, and 20 mL of ethanol for 12 h. The ball-to-material ratio of the mechanical ball milling is 50:1. Calcinate the obtained mixture at 750 °C in an oxygen atmosphere for 36 h to obtain the recycled positive electrode material.

[0065] Example 3

[0066] This example provides a method for recycling the positive electrode material of waste lithium batteries, including the following steps:

[0067] S1: Carry out a hydrothermal reaction on 10 g of the positive electrode material of waste five-series ternary lithium batteries at a liquid-solid ratio of 5 mL / g with a H2SO4 solution containing 0.05 mol at 200 °C. Among them, H +The molar ratio of hydrogen to lithium in the cathode material of waste lithium batteries is 1:1. After reacting for 18 h, filter residue 1 and filtrate 1 are separated. The chemical composition of the filter residue 1 is shown in Table 1;

[0068] S2: To synthesize the cathode material with the target composition of Li(Ni 0.5 Co 0.2 Mn 0.3 )O2, 9 g of the filter residue 1 obtained in S1 is put into a solution containing 2.2 g of lithium hydroxide, 2.6 g of nickel carbonate, 1.05 g of cobalt carbonate, 1.5 g of manganese carbonate and 15 vol.% ethylene according to the liquid-solid ratio of 5 mL / g. After mixing evenly, hydrothermal reaction is carried out at 160 °C. After reacting for 12 h, the separated precipitate is washed with deionized water and dried to obtain filter residue 2;

[0069] S3: The filter residue 2 obtained in S2 and 1.2 g of lithium carbonate are mechanically ball-milled for 6 h. The ball-to-material ratio of the mechanical ball-milling is 30:1. The obtained mixture is calcined at 850 °C in an oxygen atmosphere for 18 h to obtain the recycled cathode material.

[0070] Example 4

[0071] This example provides a method for recycling the cathode material of waste lithium batteries, including the following steps:

[0072] S1: 10 g of the cathode material of waste five-series ternary lithium batteries is subjected to hydrothermal reaction at 200 °C with a solution containing 0.05 mol of H2SO4 according to the liquid-solid ratio of 5 mL / g. Among them, H + The molar ratio of hydrogen to lithium in the cathode material of waste lithium batteries is 1:1. After reacting for 18 h, filter residue 1 and filtrate 1 are separated. The chemical composition of the filter residue 1 is shown in Table 1;

[0073] S2: To synthesize the cathode material with the target composition of Li(Ni 0.5 Co 0.2 Mn 0.3 )O2, 9 g of the filter residue 1 obtained in S1 is put into a solution containing 4 g of lithium hydroxide, 2.6 g of nickel carbonate, 1.05 g of cobalt carbonate, 1.5 g of manganese carbonate and 15 vol.% ethylene according to the liquid-solid ratio of 5 mL / g. After mixing evenly, hydrothermal reaction is carried out at 160 °C. After reacting for 12 h, the separated precipitate is washed with deionized water and dried to obtain filter residue 2;

[0074] S3: The filter residue 2 obtained in S2 and 1.2 g of lithium carbonate are mechanically ball-milled for 6 h. The ball-to-material ratio of the mechanical ball-milling is 30:1. The obtained mixture is calcined at 850 °C in an oxygen atmosphere for 18 h to obtain the recycled cathode material.

[0075] Example 5

[0076] This embodiment provides a method for recycling the cathode material of waste lithium batteries, comprising the following steps:

[0077] S1: Hydrothermally react 10 g of the cathode material of waste lithium batteries of the five-series ternary type with an H2SO4 solution containing 0.05 mol at a liquid-solid ratio of 5 mL / g at 200 °C, where the molar ratio of H + to lithium in the cathode material of the waste lithium battery is 1:1. After reacting for 18 h, filter residue 1 and filtrate 1 are separated, and the chemical composition of the filter residue 1 is shown in Table 1;

[0078] S2: To synthesize the cathode material with the target composition of Li(Ni 0.5 Co 0.2 Mn 0.3 )O2, put 9 g of the filter residue 1 obtained in S1 into a solution containing 8 g of lithium hydroxide, 2.6 g of nickel carbonate, 1.05 g of cobalt carbonate, 1.5 g of manganese carbonate, and 15 vol.% ethylene at a liquid-solid ratio of 5 mL / g. After mixing evenly, carry out hydrothermal reaction at 160 °C. After reacting for 12 h, the separated precipitate is washed with deionized water and dried to obtain filter residue 2;

[0079] S3: Mechanically ball-mill the filter residue 2 obtained in S2 and 1.2 g of lithium carbonate for 6 h. The ball-to-material ratio of the mechanical ball-milling is 30:1. The obtained mixture is calcined at 850 °C in an oxygen atmosphere for 18 h to obtain the recycled cathode material.

[0080] Example 6

[0081] This embodiment provides a method for recycling the cathode material of waste lithium batteries, comprising the following steps:

[0082] S1: Hydrothermally react 10 g of the cathode material of waste lithium batteries of the five-series ternary type with an H2SO4 solution containing 0.05 mol at a liquid-solid ratio of 5 mL / g at 200 °C, where the molar ratio of H + to lithium in the cathode material of the waste lithium battery is 1:1. After reacting for 18 h, filter residue 1 and filtrate 1 are separated, and the chemical composition of the filter residue 1 is shown in Table 1;

[0083] S2: To synthesize the cathode material with the target composition of Li(Ni 0.5 Co 0.2 Mn 0.3 )O2, put 9 g of the filter residue 1 obtained in S1 into a solution containing 12 g of lithium hydroxide, 2.6 g of nickel carbonate, 1.05 g of cobalt carbonate, 1.5 g of manganese carbonate, and 15 vol.% ethylene at a liquid-solid ratio of 5 mL / g. After mixing evenly, carry out hydrothermal reaction at 160 °C. After reacting for 12 h, the separated precipitate is washed with deionized water and dried to obtain filter residue 2;

[0084] S3: Mechanically ball-mill the filter residue 2 obtained in S2 and 1.2 g of lithium carbonate for 6 h. The ball-to-material ratio of the mechanical ball milling is 30:1. Calcinate the obtained mixture at 850 °C for 18 h in an oxygen atmosphere to obtain the regenerated cathode material.

[0085] Comparative Example 1

[0086] This comparative example provides a method for regenerating the cathode material of waste lithium batteries. The only difference from Example 1 is that step S1 is not carried out.

[0087] Comparative Example 2

[0088] This comparative example provides a method for regenerating the cathode material of waste lithium batteries. The only difference between this comparative example and Example 1 is that step S2 is not carried out.

[0089] Comparative Example 3

[0090] This comparative example provides a method for regenerating the cathode material of waste lithium batteries. The only difference between this comparative example and Example 1 is that no additive is added in step S2.

[0091] Table 1 Chemical composition of filter residue 1

[0092]

[0093] Effect Example

[0094] Use a scanning electron microscope to test the morphologies of the filter residue 1 obtained in Example 1, the regenerated cathode material, and the cathode materials obtained in Comparative Examples 1-3. The results are as Figure 1 shown. It can be seen from Figure 1 that the morphologies of the filter residue 1 and the regenerated cathode material obtained in Example 1 are both spherical particles with closely packed primary particles; while the morphologies of the cathode materials in Comparative Examples 1 and 2 are irregular particles with closely packed primary particles; the morphology of the cathode material in Comparative Example 3 is dispersed particles, indicating that the regeneration method of the present invention does not change the morphology of the cathode material.

[0095] Test the electrochemical performance of the regenerated cathode materials obtained in Examples 1-6 and Comparative Examples 1-3. Grind the regenerated cathode material, Super P, and polytetrafluoroethylene (PTFE) binder evenly in a mass ratio of 8:1:1, and then carry out a sufficient rolling process until a uniform electrode film is formed. Then cut the obtained electrode film into electrodes of 6×6 mm 2 to ensure that the loading amount of the active material is 5.5 mg / cm 2Above. The above electrode was assembled as a 2032 type button battery with the positive electrode, a polypropylene (PP) material as the separator, lithium metal as the negative electrode, and an electrolyte of 1.0 M LiPF6 in ethylene carbonate / diethyl carbonate (EC / DMC = 1:1). The assembled battery was subjected to constant current charge / discharge measurements on a Land CT2001A battery test system. The test results are shown in Table 2 and Figure 2 as follows.

[0096] Table 2 Electrochemical properties of the positive electrode materials obtained in Examples 1-6 and Comparative Examples 1-3

[0097]

[0098] As can be seen from Table 2, the lithium battery prepared with the regenerated positive electrode material of the present invention has more excellent electrochemical properties. The first-week discharge specific capacity is 150-155 mAh / g; the capacity retention rate after 100 cycles at 25 °C is 91-94%. The electrochemical performance of the lithium battery prepared with the regenerated positive electrode material decreases significantly if any step in the regeneration method of the present invention is missing.

[0099] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for recycling the cathode material of waste lithium batteries, characterized in that, It includes the following steps: S1: Add an acid to the cathode material of waste lithium batteries, conduct a selective lithium extraction reaction at 160 - 240 °C, separate to obtain a filtrate and filter residue 1. The filter residue 1 is a nickel-cobalt-manganese compound, and the filtrate is a lithium salt solution; S2: Mix lithium source 1, transition metal source, and additive solution to obtain mixture 1, then mix it with the filter residue 1 obtained in S1 and conduct a hydrothermal reaction. The reaction product is separated to obtain filter residue 2 and a filtrate; S3: Ball-mill the filter residue 2 obtained in S2 with lithium source 2, and calcine the obtained mixture to obtain a regenerated cathode material for lithium batteries; Among them, the molar ratio of H in the acid described in step S1 + to lithium in the cathode material of the waste lithium battery is 0.9-1.1:1; In step S2, the additive is at least one of primary n-carbon alcohols with less than 12 carbon atoms, ethylene glycol, glycerol, ethylene, and hydrogen peroxide; the temperature of the hydrothermal reaction is 100 - 240 °C.

2. The method according to claim 1, wherein In step S1, the temperature of the selective lithium extraction reaction is 180 - 220 °C.

3. The method according to claim 1, characterized in that In step S1, the liquid-solid ratio of the selective lithium extraction reaction is 1 - 20 mL / g.

4. The method according to claim 1, wherein In step S1, the acid is at least one of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, and citric acid.

5. The method according to claim 1, wherein The lithium source 1 and lithium source 2 are at least one of lithium sulfate, lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, and lithium acetate.

6. The method according to claim 1, wherein In step S2, the transition metal source is at least one of a nickel source, a cobalt source, and a manganese source.

7. The method according to claim 1, characterized in that In step S2, at least one of the following (a) - (e): (a) The molar ratio of lithium in the lithium source 1 to the transition metal in the filter residue 1 is 1 - 6:1; (b) The molar ratio of the transition metal source to the transition metal in the filter residue 1 is 0.01 - 1:1; (c) The volume concentration of the additive in the mixture 1 is 1 - 15%; (d) The time of the hydrothermal reaction is 1 - 24 h; (e) The liquid-solid ratio of the filter residue 1 to the mixture 1 is 1 - 20 mL / g.

8. The method according to claim 1, wherein In step S3, at least one of the following (a) - (f): (a) The addition amount of the lithium source 2 is 5 - 15% of the mass of the filter residue 2; (b) The ball-to-material ratio of the ball milling is 5 - 50:1; (c) The time of the ball milling is 0.1 - 12 h; (d) The atmosphere of the calcination is at least one of air and oxygen; (e) The temperature of the calcination is 750 °C - 950 °C; (f) The time of the calcination is 12 h - 36 h.

9. A regenerated cathode material for lithium batteries obtained by the method for regenerating the cathode material of waste lithium batteries according to any one of claims 1 - 8.

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