A method for treating waste lithium battery cathode sheets and its application

Abstract

The present invention discloses a method for treating the positive electrode sheets of waste lithium batteries and its application. The method comprises the following steps: (1) crushing and screening the positive electrode sheets of waste lithium batteries to obtain oversize materials and undersize materials, wherein the oversize materials are positive electrode sheet scraps and the undersize materials are positive electrode material powders; (2) baking, passivating, alkali washing, screening and dehydrating the positive electrode sheet scraps, and drying to obtain aluminum foil scraps and positive electrode material washing liquid; (3) pressure filtering the positive electrode material washing liquid and then making it into a slurry for leaching. This method can separate and reuse the aluminum foil and the positive electrode material in the positive electrode sheets of waste lithium batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling of waste lithium - ion batteries, and particularly relates to a method for treating the positive electrode sheets of waste lithium - ion batteries and its application. Background Art

[0002] Lithium - ion batteries are an environmentally friendly and recyclable battery type, with characteristics such as high energy density, light weight, small volume, long cycle life, and no memory effect. They have a wide range of applications in fields such as communication, medical, transportation, aerospace, and energy storage. A lithium - ion battery consists of positive and negative electrode sheets, electrolyte, separator paper, and a casing. The positive electrode sheet contains nickel - cobalt - manganese positive electrode material, which is a core component of the lithium - ion battery. In recent years, with the stable growth of the market demand for lithium - ion batteries, the production capacity of lithium - ion batteries has been continuously expanded. A large number of waste lithium - ion battery electrode sheets have emerged during the production and use processes. These are industrial waste products with relatively high cobalt and nickel content. If not properly treated, it will not only cause waste of resources but also environmental pollution. Therefore, recycling waste electrode sheets is of great significance for reducing environmental pollution and alleviating the shortage of cobalt and nickel resources. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a method for treating the positive electrode sheets of waste lithium - ion batteries and its application, which can separate and reuse the aluminum foil and the positive electrode material in the positive electrode sheets of waste lithium - ion batteries.

[0004] The above - mentioned technical object of the present invention is achieved through the following technical solutions:

[0005] A method for treating the positive electrode sheets of waste lithium - ion batteries, comprising the following steps:

[0006] (1) Crushing and screening the positive electrode sheets of waste lithium - ion batteries to obtain over - size materials and undersize materials. The over - size materials are positive electrode sheet scraps, and the undersize materials are positive electrode material powders;

[0007] (2) Baking, passivating, alkali - washing, screening, dehydrating the positive electrode sheet scraps, and drying to obtain aluminum foil scraps and positive electrode material washing liquid;

[0008] (3) Filter - pressing the positive electrode material washing liquid and then pulping and leaching.

[0009] Preferably, in step (1), the crushing is carried out under a protective atmosphere.

[0010] Preferably, the protective atmosphere is at least one of nitrogen or carbon dioxide.

[0011] Preferably, the mesh number of the sieve used in the screening in step (1) is 50 - 100 meshes.

[0012] Further preferably, the mesh number of the sieve used in the sieving in step (1) is 60-80 meshes.

[0013] Preferably, the baking temperature in step (2) is 100-150 °C.

[0014] Further preferably, the baking temperature in step (2) is 110-130 °C.

[0015] Preferably, in step (2), the passivation is to oxidize and passivate the positive electrode sheet scraps using an oxidant.

[0016] Preferably, the oxidant is hydrogen peroxide.

[0017] Preferably, the concentration of the hydrogen peroxide is 5%-10%, the liquid-solid ratio mL / g of the hydrogen peroxide to the positive electrode sheet scraps is (2-30):1, and the reaction time is 15-60 min.

[0018] Further preferably, the concentration of the hydrogen peroxide is 7%-9%, the liquid-solid ratio mL / g of the hydrogen peroxide to the positive electrode sheet scraps is (15-20):1, and the reaction time is 20-45 min.

[0019] Preferably, the alkaline cleaning solution used for the alkaline cleaning is at least one of sodium hydroxide solution, potassium hydroxide solution, barium hydroxide solution and calcium hydroxide solution.

[0020] Preferably, the concentration of the alkaline cleaning solution is 0.5-5 mol / L.

[0021] Further preferably, the concentration of the alkaline cleaning solution is 1-3 mol / L.

[0022] Preferably, the liquid-solid ratio mL / g of the alkaline cleaning solution to the positive electrode material is (5-10):1.

[0023] Further preferably, the liquid-solid ratio mL / g of the alkaline cleaning solution to the positive electrode material is (6-9):1.

[0024] Preferably, in step (2), the alkaline cleaning further includes adding a phase transfer catalyst to the used alkaline cleaning solution.

[0025] Preferably, the liquid-solid ratio mL / g of the alkaline cleaning solution to the phase transfer catalyst is (5-30):1.

[0026] Further preferably, the liquid-solid ratio mL / g of the alkaline cleaning solution to the phase transfer catalyst is (10-20):1.

[0027] Preferably, the phase transfer catalyst is at least one of chain polyethylene glycol, chain polyethylene glycol dialkyl ether, benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogensulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, 18-crown-6, 15-crown-5, and cyclodextrin.

[0028] Preferably, in step (2), the alkali washing process is also combined with ultrasonic cleaning. Preferably, the ultrasonic frequency is 30 - 120 KHz, and the ultrasonic time is 30 - 120 min.

[0029] More preferably, the ultrasonic frequency is 50 - 90 KHz, and the ultrasonic time is 30 - 60 min.

[0030] Preferably, in step (2), stirring is also performed during the alkali washing process, and the stirring speed is 200 - 800 r / min. Preferably, in step (2), the mesh number of the sieve used for screening is 30 - 80 mesh. More preferably, in step (2), the mesh number of the sieve used for screening is 50 - 60 mesh.

[0031] Preferably, in step (2), the dehydration can be carried out by a centrifuge, and the rotation speed of the centrifuge during dehydration is 700 - 960 r / min.

[0032] More preferably, in step (2), the dehydration can be carried out by a centrifuge, and the rotation speed of the centrifuge during dehydration is 800 - 900 r / min.

[0033] Preferably, in step (2), the drying temperature is 80 - 150 °C. More preferably, in step (2), the drying temperature is 90 - 120 °C.

[0034] Preferably, in step (3), the pressure intensity of pressure filtration is 2 - 8 MPa. More preferably, in step (3), the pressure intensity of pressure filtration is 5 - 6 MPa.

[0035] Application of the method as described above in the recycling of waste batteries.

[0036] The beneficial effects of the present invention are:

[0037] (1) The present invention utilizes strong alkali to degrade PVDF so as to separate the aluminum foil from the cathode material. Specifically, the hydroxide radical of the strong alkali attacks the hydrogen atom on the β-carbon of the PVDF molecular chain, while the fluorine atom leaves to form a double bond. The double bond continues to be oxidized in the strong alkali environment, forming hydroxyl and carbonyl groups on the conjugated polyene carbon chain, and finally forming an unsaturated ketone structure on the molecular chain, achieving the purpose of destroying PVDF and changing its properties. Since the alkali degradation of PVDF mostly occurs in an alkaline environment and the substances participating in the reaction are in two phases (solid phase - liquid phase), the alkali degradation reaction only occurs on the surface polymer chains. For this two-phase interface reaction, the properties of the boundary layer greatly affect the progress of the reaction. Therefore, a phase transfer catalyst is added to accelerate the degradation reaction. To ensure less hydrogen production during the alkali washing process, the crushed cathode sheets are treated with hydrogen peroxide to form a dense oxide film on the surface of the aluminum foil to passivate it, preventing the reaction between the alkali and the aluminum foil to produce hydrogen, thus improving the safety of industrial production.

[0038] Reaction equation (reaction between hydroxide radical and PVDF molecule):

[0039]

[0040] (2) Compared with the existing methods for treating waste lithium battery cathode sheets, the main current methods for treating waste lithium battery cathode sheets mostly use high-temperature pyrolysis. This method uses low-temperature heat treatment for waste lithium battery cathode sheets. Compared with high-temperature pyrolysis treatment, this method requires lower energy consumption; more waste gas is generated during high-temperature pyrolysis, while this method using low-temperature heat treatment basically does not generate waste gas. Compared with high-temperature pyrolysis treatment, this method is more energy-saving and environmentally friendly.

[0041] (3) The present invention separates the cathode material from the aluminum foil of the waste lithium battery cathode sheet to obtain the cathode material. Its process is simple and easy for industrial production. At the same time, the cathode material of the waste lithium battery cathode sheet is efficiently recycled and reused, which can not only solve the pollution problem of waste lithium battery cathode sheets, but also recycle the cathode material of waste lithium battery cathode sheets, providing raw materials for lithium battery manufacturing, and realizing the resource recycling of waste lithium ion battery cathode sheets. Description of the Drawings

[0042] Figure 1 is the process flow chart of the present invention;

[0043] Figure 2 is the schematic diagram of the crushed cathode sheet of Example 1 of the present invention;

[0044] Figure 3 is the schematic diagram of the aluminum foil scraps obtained in Example 1 of the present invention. Detailed Embodiments

[0045] The following further illustrates the present invention with specific embodiments.

[0046] Example 1:

[0047] As Figure 1 shown, a method for treating the positive electrode sheet of waste lithium batteries includes the following steps:

[0048] (1) Under the protection of nitrogen and carbon dioxide, 1 kg of the positive electrode sheet of waste lithium batteries is crushed to 2 cm and screened through a 60-mesh circular vibrating screen to obtain the oversize and the undersize. The oversize is the positive electrode sheet scraps, and the undersize is the positive electrode material powder. The positive electrode sheet scraps are as Figure 2 shown;

[0049] (2) Bake the positive electrode sheet scraps at a temperature of 120 °C for 60 min. To the heat-treated positive electrode sheet scraps, first add 10% hydrogen peroxide with a liquid-solid ratio of mL / g of 2:1, stir for 15 min to fully oxidize and passivate the aluminum foil in the baked positive electrode sheet scraps, then add a sodium hydroxide solution with a liquid-solid ratio of mL / g of 10:1 and a concentration of 5 mol / L, and then add benzyltriethylammonium chloride. The liquid-solid ratio of the sodium hydroxide solution to benzyltriethylammonium chloride is mL / g of 30:1. After stirring evenly at 400 r / min, perform ultrasonic alkali washing at 60 KHz for 60 min; then wash and screen the alkali-washed aluminum foil with a vibrating water sieve. The mesh number of the vibrating water sieve is 30 meshes to wash off the residual alkali and positive electrode material on the aluminum foil; then perform centrifugal dehydration. The rotation speed of the centrifuge during dehydration is 700 r / min, and finally dry at 100 °C to obtain aluminum foil scraps and collect the positive electrode material washing solution obtained after rinsing. The aluminum foil scraps are as Figure 3 shown;

[0050] (3) Filter and pulp-leach the positive electrode material washing solution, where the pressure intensity of filtration is 2 MPa.

[0051] Among them, the weight of the aluminum foil in the unused positive electrode sheet of the lithium battery (brand new) accounts for about 14% of the weight of the positive electrode sheet. The recovery rates of the positive electrode material powder and the aluminum foil are calculated respectively by the following formula: W1 = M2 / (M0 - M1)%; W2 = (M1 / 0.14M0)%, where M2 is the weight of the dried positive electrode material powder, M0 is the weight of the raw material, M1 is the weight of the dried aluminum foil, W1 is the recovery rate of the positive electrode material powder, and W2 is the recovery rate of the aluminum foil.

[0052] The calculated recovery rate of the positive electrode material powder is 99.5%, and the impurity aluminum content is 0.2%. The recovery rate of the aluminum foil is 99.7%.

[0053] Example 2:

[0054] A method for treating the positive electrode sheet of waste lithium batteries includes the following steps:

[0055] (1) Under the protection of nitrogen and carbon dioxide, 1 kg of waste lithium battery cathode sheets are crushed to 2 cm and screened through an 80-mesh circular vibrating screen to obtain oversize and undersize materials. The oversize materials are cathode sheet scraps, and the undersize materials are cathode material powders;

[0056] (2) Bake the cathode sheet scraps at 150 °C for 60 min. Then, add 5% hydrogen peroxide with a liquid-solid ratio of 10:1 mL / g to the heat-treated cathode sheet scraps, stir for 30 min to fully oxidize and passivate the aluminum foil in the baked cathode sheet scraps. Then, add a sodium hydroxide solution with a liquid-solid ratio of 10:1 mL / g and a concentration of 0.5 mol / L, and add benzyltriethylammonium chloride. The liquid-solid ratio of the sodium hydroxide solution to benzyltriethylammonium chloride is 20:1 mL / g. After stirring evenly at 400 r / min, perform ultrasonic alkali washing at 60 KHz for 30 min. Then, wash and screen the alkali-washed aluminum foil with a vibrating water screen. The mesh number of the vibrating water screen is 80 meshes to wash away the residual alkali cathode material on the aluminum foil. Then, perform dehydration. The rotation speed of the centrifuge during dehydration is 960 r / min. Finally, dry at 100 °C to obtain aluminum foil scraps and collect the cathode material washing solution obtained after rinsing;

[0057] (3) Filter the cathode material washing solution by pressure filtration and then make a pulp for leaching. The pressure intensity during pressure filtration is 8 MPa.

[0058] The recovery rate of the cathode material powder is 99.6%, and the aluminum impurity content is 0.12%. The recovery rate of the aluminum foil is 99.5%.

[0059] Example 3:

[0060] A method for treating waste lithium battery cathode sheets, comprising the following steps:

[0061] (1) Under the protection of nitrogen and carbon dioxide, 1 kg of waste lithium battery cathode sheets are crushed to 2 cm and screened through an 80-mesh circular vibrating screen to obtain oversize and undersize materials. The oversize materials are cathode sheet scraps, and the undersize materials are cathode material powders;

[0062] (2) Bake the positive electrode piece scraps at 150 °C for 60 min. Then, add 10% hydrogen peroxide with a liquid-solid ratio of 10:1 mL / g to the heat-treated positive electrode piece scraps, stir for 60 min to fully oxidize and passivate the aluminum foil in the baked positive electrode piece scraps. Next, add a calcium hydroxide solution with a liquid-solid ratio of 10:1 mL / g and a concentration of 5 mol / L, and then add tetrabutylammonium bromide. The liquid-solid ratio of the calcium hydroxide solution to tetrabutylammonium bromide is 10:1 mL / g. After stirring evenly at 400 r / min, perform ultrasonic alkali washing at 60 KHz for 30 min. Then, wash and screen the alkali-washed aluminum foil with a vibrating water sieve. The mesh number of the vibrating water sieve is 50 meshes to wash away the residual alkali positive electrode material on the aluminum foil. Then, perform dehydration. The rotation speed of the centrifuge during dehydration is 800 r / min. Finally, dry at 100 °C to obtain aluminum foil scraps and collect the positive electrode material washing solution obtained after rinsing.

[0063] (3) Pulp and leach the positive electrode material washing solution after pressure filtration, where the pressure intensity of the pressure filtration is 5 MPa.

[0064] The recovery rate of the positive electrode material powder is 99.7%, and the impurity aluminum content is 0.15%. The recovery rate of the aluminum foil is 99.5%.

[0065] Example 4:

[0066] A method for treating waste lithium battery positive electrode pieces includes the following steps:

[0067] (1) Under the protection of nitrogen and carbon dioxide, crush 1 kg of waste lithium battery positive electrode pieces to 2 cm and screen them through an 80-mesh circular vibrating sieve to obtain the oversize and the undersize. The oversize is the positive electrode piece scraps, and the undersize is the positive electrode material powder.

[0068] (2) Bake the positive electrode piece scraps at 150 °C for 60 min. Then, add 5% hydrogen peroxide with a liquid-solid ratio of 15:1 mL / g to the heat-treated positive electrode piece scraps, stir for 30 min to fully oxidize and passivate the aluminum foil in the baked positive electrode piece scraps. Next, add a calcium hydroxide solution with a liquid-solid ratio of 5:1 mL / g and a concentration of 0.5 mol / L, and then add tetrabutylammonium bromide. The liquid-solid ratio of the calcium hydroxide solution to tetrabutylammonium bromide is 10:1 mL / g. After stirring evenly at 400 r / min, perform ultrasonic alkali washing at 60 KHz for 60 min. Then, wash and screen the alkali-washed aluminum foil with a vibrating water sieve. The mesh number of the vibrating water sieve is 60 meshes to wash away the residual alkali positive electrode material on the aluminum foil. Then, perform dehydration. The rotation speed of the centrifuge during dehydration is 900 r / min. Finally, dry at 100 °C to obtain aluminum foil scraps and collect the positive electrode material washing solution obtained after rinsing.

[0069] (3) Pulp and leach the positive electrode material washing solution after pressure filtration, where the pressure intensity of the pressure filtration is 6 MPa.

[0070] The recovery rate of the positive electrode material powder is 99.5%, and the impurity aluminum content is 0.08%. The recovery rate of the aluminum foil is 99.6%.

[0071] Example 5:

[0072] A method for treating waste lithium battery positive electrode sheets, comprising the following steps:

[0073] (1) Under the protection of nitrogen and carbon dioxide, 1 kg of waste lithium battery positive electrode sheets are crushed to 2 cm and screened through an 80-mesh circular vibrating screen to obtain oversize and undersize materials. The oversize material is the positive electrode sheet scraps, and the undersize material is the positive electrode material powder;

[0074] (2) Bake the positive electrode sheet scraps at a temperature of 120 °C for 60 min; then, to the heat-treated positive electrode sheet scraps, first add 5% hydrogen peroxide with a liquid-solid ratio of mL / g of 15:1, stir for 30 min to fully oxidize and passivate the aluminum foil in the baked positive electrode sheet scraps, then add a potassium hydroxide solution with a liquid-solid ratio of mL / g of 5:1 and a concentration of 5 mol / L, and then add tetrabutylammonium bromide, where the liquid-solid ratio of the potassium hydroxide solution to tetrabutylammonium bromide is mL / g of 10:1. After stirring evenly at 600 r / min, perform ultrasonic alkali washing at 60 KHz for 60 min; then wash and screen the alkali-washed aluminum foil with a vibrating water screen. The screen mesh of the vibrating water screen is 60 meshes to wash off the residual alkali positive electrode material on the aluminum foil; then perform dehydration. The rotation speed of the centrifuge during dehydration is 850 r / min, and finally dry at 100 °C to obtain aluminum foil scraps and collect the positive electrode material washing liquid obtained after rinsing;

[0075] (3) Filter the positive electrode material washing liquid by pressure filtration and then make a pulp for leaching, where the pressure intensity of the pressure filtration is 5.5 MPa.

[0076] The recovery rate of the positive electrode material powder is 99.7%, and the impurity aluminum content is 0.06%. The recovery rate of the aluminum foil is 99.7%.

[0077] Example 6:

[0078] A method for treating waste lithium battery positive electrode sheets, comprising the following steps:

[0079] (1) Under the protection of nitrogen and carbon dioxide, 1 kg of waste lithium battery positive electrode sheets are crushed to 2 cm and screened through an 80-mesh circular vibrating screen to obtain oversize and undersize materials. The oversize material is the positive electrode sheet scraps, and the undersize material is the positive electrode material powder;

[0080] (2) Bake the positive electrode piece scraps at a temperature of 150 °C for 60 min; then add 5% hydrogen peroxide with a liquid-solid ratio of 20:1 mL / g to the heat-treated positive electrode piece scraps, stir for 30 min to fully oxidize and passivate the aluminum foil in the baked positive electrode piece scraps, then add a potassium hydroxide solution with a liquid-solid ratio of 10:1 mL / g and a concentration of 5 mol / L, and then add tetrabutylammonium bromide, where the liquid-solid ratio of the potassium hydroxide solution to tetrabutylammonium bromide is 15:1 mL / g. After stirring evenly at 400 r / min, perform ultrasonic alkali washing at 60 KHz for 60 min; then wash and screen the alkali-washed aluminum foil with a vibrating water sieve. The mesh number of the vibrating water sieve is 60 meshes to wash off the residual alkali positive electrode material on the aluminum foil; then perform dehydration. The rotation speed of the centrifuge during dehydration is 850 r / min, and finally dry at 100 °C to obtain aluminum foil scraps and collect the positive electrode material washing liquid obtained after rinsing;

[0081] (3) Pulp and leach the positive electrode material washing liquid after pressure filtration, where the pressure intensity of the pressure filtration is 5.5 MPa.

[0082] The recovery rate of the positive electrode material powder is 99.6%, and the impurity aluminum content is 0.16%. The recovery rate of the aluminum foil is 99.4%.

[0083] Example 7:

[0084] A method for treating waste lithium battery positive electrode pieces includes the following steps:

[0085] (1) Under the protection of nitrogen and carbon dioxide, crush 1 kg of waste lithium battery positive electrode pieces to 2 cm and screen them through a 70-mesh circular vibrating sieve to obtain the oversize and undersize materials. The oversize material is positive electrode piece scraps, and the undersize material is positive electrode material powder;

[0086] (2) Bake the positive electrode piece scraps at a temperature of 120 °C for 60 min; then add 8% hydrogen peroxide with a liquid-solid ratio of 18:1 mL / g to the heat-treated positive electrode piece scraps, stir for 30 min to fully oxidize and passivate the aluminum foil in the baked positive electrode piece scraps, then add a potassium hydroxide solution with a liquid-solid ratio of 8:1 mL / g and a concentration of 2 mol / L, and then add tetrabutylammonium bromide, where the liquid-solid ratio of the potassium hydroxide solution to tetrabutylammonium bromide is 15:1 mL / g. After stirring evenly at 400 r / min, perform ultrasonic alkali washing at 60 KHz for 60 min; then wash and screen the alkali-washed aluminum foil with a vibrating water sieve. The mesh number of the vibrating water sieve is 60 meshes to wash off the residual alkali positive electrode material on the aluminum foil; then perform dehydration. The rotation speed of the centrifuge during dehydration is 850 r / min, and finally dry at 110 °C to obtain aluminum foil scraps and collect the positive electrode material washing liquid obtained after rinsing;

[0087] (3) Pulp and leach the positive electrode material washing liquid after pressure filtration, where the pressure intensity of the pressure filtration is 5.5 MPa.

[0088] The recovery rate of the positive electrode material powder is 99.9%, and the impurity aluminum content is 0.032%. The recovery rate of the aluminum foil is 99.9%.

[0089] Example 8:

[0090] A method for treating waste lithium battery positive electrode sheets, comprising the following steps:

[0091] (1) Under the protection of nitrogen and carbon dioxide, 1 kg of waste lithium battery positive electrode sheets are crushed to 2 cm and screened through a 60-mesh circular vibrating screen to obtain oversize and undersize materials. The oversize material is positive electrode sheet scraps, and the undersize material is positive electrode material powder;

[0092] (2) Bake the positive electrode sheet scraps at a temperature of 110 °C for 60 min; then, to the heat-treated positive electrode sheet scraps, first add 7% hydrogen peroxide with a liquid-solid ratio of mL / g of 15:1, stir for 20 min to fully oxidize and passivate the aluminum foil in the baked positive electrode sheet scraps, then add a potassium hydroxide solution with a liquid-solid ratio of mL / g of 6:1 and a concentration of 1 mol / L, and then add tetrabutylammonium bromide, where the liquid-solid ratio of the potassium hydroxide solution to tetrabutylammonium bromide is mL / g of 10:1. After stirring evenly at 400 r / min, perform ultrasonic alkali washing at 60 KHz for 60 min; then wash and screen the alkali-washed aluminum foil with a vibrating water screen. The screen mesh of the vibrating water screen is 60 meshes to wash away the residual alkali positive electrode material on the aluminum foil; then perform dehydration. When dehydrating, the rotation speed of the centrifuge is 800 r / min, and finally dry at 90 °C to obtain aluminum foil scraps and collect the positive electrode material washing solution obtained after rinsing;

[0093] (3) Filter the positive electrode material washing solution by pressure filtration and then make it into a slurry for leaching, where the pressure intensity of the pressure filtration is 5 MPa.

[0094] The recovery rate of the positive electrode material powder is 99.9%, and the impurity aluminum content is about 0.035%. The recovery rate of the aluminum foil is 99.9%.

[0095] Example 9:

[0096] A method for treating waste lithium battery positive electrode sheets, comprising the following steps:

[0097] (1) Under the protection of nitrogen and carbon dioxide, 1 kg of waste lithium battery positive electrode sheets are crushed to 2 cm and screened through an 80-mesh circular vibrating screen to obtain oversize and undersize materials. The oversize material is positive electrode sheet scraps, and the undersize material is positive electrode material powder;

[0098] (2) Bake the cathode scrap at 130 °C for 60 min; then add 9% hydrogen peroxide with a liquid-solid ratio of 20:1 mL / g to the heat-treated cathode scrap, stir for 45 min to fully oxidize and passivate the aluminum foil in the baked cathode scrap, then add a potassium hydroxide solution with a liquid-solid ratio of 9:1 mL / g and a concentration of 3 mol / L, and then add tetrabutylammonium bromide, where the liquid-solid ratio of the potassium hydroxide solution to tetrabutylammonium bromide is 20:1 mL / g. After stirring evenly at 400 r / min, perform ultrasonic alkali washing at 60 KHz for 60 min; then wash and screen the alkali-washed aluminum foil with a vibrating water sieve. The mesh number of the vibrating water sieve is 60 meshes to wash off the residual alkali cathode material on the aluminum foil; then perform dehydration, with the centrifuge rotating at 900 r / min, and finally dry at 120 °C to obtain aluminum foil scrap and collect the cathode material washing solution obtained after rinsing;

[0099] (3) Pulp and leach the cathode material washing solution after pressure filtration, where the pressure intensity of the pressure filtration is 6 MPa.

[0100] The recovery rate of the cathode material powder is 99.9%, and the impurity aluminum content is about 0.036%. The recovery rate of the aluminum foil is 99.9%.

[0101] Example 10: (Compared with Example 9, no phase transfer catalyst is added during the treatment process, and the other steps remain unchanged)

[0102] A method for treating waste lithium battery cathode sheets includes the following steps:

[0103] (1) Under the protection of nitrogen and carbon dioxide, crush 1 kg of waste lithium battery cathode sheets to 2 cm and screen them through an 80-mesh circular vibrating screen to obtain oversize and undersize materials. The oversize material is cathode scrap, and the undersize material is cathode material powder;

[0104] (2) Bake the cathode scrap at 130 °C for 60 min; then add 9% hydrogen peroxide with a liquid-solid ratio of 20:1 mL / g to the heat-treated cathode scrap, stir for 45 min to fully oxidize and passivate the aluminum foil in the baked cathode scrap, then add a potassium hydroxide solution with a liquid-solid ratio of 9:1 mL / g, stir evenly at 400 r / min, and then perform ultrasonic alkali washing at 60 KHz for 60 min; then wash and screen the alkali-washed aluminum foil with a vibrating water sieve. The mesh number of the vibrating water sieve is 60 meshes to wash off the residual alkali cathode material on the aluminum foil; then perform dehydration, with the centrifuge rotating at 900 r / min, and finally dry at 120 °C to obtain aluminum foil scrap and collect the cathode material washing solution obtained after rinsing;

[0105] (3) Pulp and leach the cathode material washing solution after pressure filtration, where the pressure intensity of the pressure filtration is 6 MPa.

[0106] The recovery rate of the positive electrode material powder is 83%, and the aluminum impurity content is about 0.1%. The recovery rate of the aluminum foil is 87%.

[0107] Comparative Example 1: (Compared with Example 9, the alkali washing was changed to acid washing during the treatment process, and the remaining steps remained unchanged)

[0108] A method for treating waste lithium battery positive electrode sheets, comprising the following steps:

[0109] (1) Under the protection of nitrogen and carbon dioxide, 1 kg of waste lithium battery positive electrode sheets are crushed to 2 cm and screened through an 80-mesh round vibrating screen to obtain oversize and undersize materials. The oversize material is positive electrode sheet scraps, and the undersize material is positive electrode material powder;

[0110] (2) The positive electrode sheet scraps are baked at 130 °C for 60 min; then, to the heat-treated positive electrode sheet scraps, 9% hydrogen peroxide with a liquid-solid ratio of 20:1 mL / g is first added, and stirred for 45 min to fully oxidize and passivate the aluminum foil in the baked positive electrode sheet scraps. Then, a sulfuric acid solution with a liquid-solid ratio of 9:1 mL / g and a concentration of 3 mol / L is added, and tetrabutylammonium bromide is added. The liquid-solid ratio of the sulfuric acid solution to tetrabutylammonium bromide is 20:1 mL / g. After stirring evenly at 400 r / min, ultrasonic acid washing is carried out at 60 KHz for 60 min; then, the acid-washed aluminum foil is washed and screened with a vibrating water screen. The screen mesh of the vibrating water screen is 60 meshes to wash away the residual acid and positive electrode material on the aluminum foil; then dehydration is carried out. The rotation speed of the centrifuge during dehydration is 900 r / min, and finally, drying is carried out at 120 °C to obtain aluminum foil scraps and collect the positive electrode material washing solution obtained after washing;

[0111] (3) The positive electrode material washing solution is pressure-filtered and then pulped and leached, where the pressure intensity of the pressure filtration is 6 MPa.

[0112] The recovery rate of the positive electrode material powder is 94%, and the aluminum impurity content is about 33%. The recovery rate of the aluminum foil is 75%.

[0113] In summary, by using the method described in the present invention to treat the positive electrode sheet with hydrogen peroxide, a dense oxide film is formed on the surface of the aluminum foil of the positive electrode sheet to passivate it, preventing the reaction between the alkali and the aluminum foil to produce hydrogen. Moreover, the decomposition of hydrogen peroxide generates oxygen bubbles, which promotes the separation of the positive electrode material from the aluminum foil. At the same time, a phase transfer catalyst is added to promote the attack of hydroxide ions on the hydrogen atoms on the β-carbon of the PVDF molecular chain, achieving the purpose of destroying PVDF and changing its properties. This invention not only greatly reduces the generation of combustible gas hydrogen, improves the safety of industrial production, but also reduces the consumption of alkali, can directly recycle the aluminum foil, improves the separation process and reduces the recycling cost. The recovery rates of the positive electrode material powder and the aluminum foil both reach over 99%, and the aluminum impurity content in the obtained positive electrode material powder is less than 0.2%. Meanwhile, when the concentration of hydrogen peroxide, the oxidant used in the present invention, is 7%-9%, the liquid-solid ratio of hydrogen peroxide to the shredded positive electrode sheet is mL / g (15-20):1, the reaction time is 20-45 min, the liquid-solid ratio of the alkali washing solution to the positive electrode material is mL / g (6-9):1, and the liquid-solid ratio of the alkali washing solution to the phase transfer catalyst is mL / g (10-20):1, the recovery rates of the positive electrode material powder and the aluminum foil of the present invention can both reach 99.9%, and the aluminum impurity content in the obtained positive electrode material powder is less than 0.03%.

[0114] In addition, by comparing Example 9 and Example 10, it can be seen that when the phase transfer catalyst is not added during the treatment process, the recovery rates of the finally obtained positive electrode material powder and the aluminum foil will both decrease significantly. By comparing Example 9 and Comparative Example 1, it can be seen that after changing the alkali washing to acid washing during the treatment process, the aluminum impurity content in the finally obtained positive electrode material powder will increase significantly.

[0115] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for treating the positive electrode sheet of waste lithium batteries, characterized in that: It includes the following steps: (1) Crushing and screening the spent lithium battery cathode sheet to obtain oversize material and undersize material, wherein the oversize material is cathode sheet scraps and the undersize material is cathode material powder; (2) Baking, passivating, alkali washing, screening, dehydrating and drying the cathode sheet scraps to obtain aluminum foil scraps and cathode material washing solution; (3) Filter pressing and pulping leaching of the cathode material washing solution; in step (2), the passivation is to oxidize and passivate the cathode sheet scraps using an oxidant; the alkali washing also includes adding a phase transfer catalyst to the used alkali washing solution; the phase transfer catalyst is at least one of chain polyethylene glycol, chain polyethylene glycol dialkyl ether, benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogensulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, 18-crown-6, 15-crown-5, cyclodextrin.

2. The method for treating the cathode sheet of waste lithium batteries according to claim 1, wherein: In step (1), the crushing is carried out under a protective atmosphere.

3. A method for treating waste lithium battery cathode sheets according to claim 1, characterized in that: The alkali washing solution used for the alkali washing is at least one of sodium hydroxide solution, potassium hydroxide solution, barium hydroxide solution and calcium hydroxide solution.

4. A method for treating waste lithium battery cathode sheets according to claim 3, characterized in that: The concentration of the alkali washing solution is 0.5 - 5 mol / L.

5. A method for treating waste lithium battery cathode sheets according to claim 3, characterized in that: The liquid-solid ratio mL / g of the alkali washing solution to the cathode material is (5 - 10):

1.

6. A method for treating waste lithium battery cathode sheets according to claim 1, characterized in that: In step (2), the alkali washing process is also combined with ultrasonic cleaning.

7. Application of the method according to any one of claims 1 - 6 in the recycling of waste batteries.

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