Method for stripping positive electrode material of waste lithium ion battery by using subcritical water

Abstract

The invention is suitable for the technical field of battery recovery, and particularly relates to a method for stripping a waste lithium ion battery positive electrode material by using subcritical water, and the method comprises the following steps: carrying out discharge treatment on a waste lithium ion battery, and disassembling the discharged waste lithium ion battery into a positive electrode plate, a negative electrode plate and a diaphragm; the method comprises the following steps: pre-treating a positive plate, treating the positive plate into a positive unit with a preset size, and recycling the positive unit through a hydrothermal reaction to obtain aluminum foil metal and positive material powder. The method has the characteristics of being simple, high in efficiency and environmentally friendly, is suitable for industrial application, has certain economic benefits and social benefits, has the advantages of being environmentally friendly, saving energy and reducing carbon compared with a high-temperature pyrolysis or roasting method, has the characteristics of no generation of harmful gas and low energy consumption, and has a good application prospect. The method has a great industrial application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery recycling, and particularly relates to a method for stripping positive electrode material of a waste lithium ion battery by using subcritical water. BACKGROUND

[0002] Lithium ion batteries are widely used in the fields of new energy vehicles, mobile electronic devices and the like. However, the lithium batteries will gradually fail in the process of cyclic use, and the electric vehicles are generally 5-8 years, and the mobile electronic devices are generally 2-3 years. At present, the recovery rate of waste lithium ion batteries is still very low, and most of them cannot be effectively treated. If these waste lithium ion batteries enter the natural environment in an inappropriate way, it will cause serious environmental pollution problems and harm human health. In addition, the lithium battery contains various valuable metals and materials, including copper foil, aluminum foil, and electrode materials containing lithium, cobalt, nickel, and manganese, and if not recycled, it will cause resource waste.

[0003] It has practical significance to disassemble and process the batteries that cannot be reused, and the pretreatment process can realize the separation of different materials and components, and plays a prerequisite role for the whole recycling process. In order to make the positive electrode material and the aluminum foil tightly combined, a binder polyvinylidene fluoride will be added in the production process of the lithium battery positive electrode sheet, which brings challenges to the battery recycling pretreatment, and makes it difficult to separate the positive electrode material from the aluminum foil. The traditional high-temperature calcination has the problems of high energy consumption and harmful gas generation, and the use of organic solvents will produce toxic wastewater. Therefore, it is necessary to develop a green and efficient method for separating the positive electrode material of the waste lithium ion battery and the aluminum foil. SUMMARY

[0004] The purpose of the present application is to provide a method for stripping positive electrode material of a waste lithium ion battery by using subcritical water, which aims to solve the problems of high energy consumption and harmful gas generation in traditional high-temperature calcination, and the problem of toxic wastewater generated by using organic solvents.

[0005] The present application is realized in that a method for stripping positive electrode material of a waste lithium ion battery by using subcritical water, the method comprises: discharging the waste lithium ion battery, and disassembling the discharged waste lithium ion battery into positive electrode sheets, negative electrode sheets and separators; pretreating the positive electrode sheets to be positive electrode units of a preset size, and recovering the positive electrode units by a hydrothermal reaction to obtain aluminum foil metal and positive electrode material powder.

[0006] Preferably, in the step of disassembling the discharged waste lithium ion battery into the positive plate, the negative plate and the diaphragm, the waste lithium ion battery is discharged by soaking in salt water, wherein the salt water is a NaCl solution, and the mass concentration of the NaCl solution is 5-10%.

[0007] Preferably, the discharging time is 12-24 hours in the process of discharging by salt water.

[0008] Preferably, in the step of pretreating the positive plate into a positive unit of a preset size, the positive plate is washed by dimethyl carbonate for multiple times in the pretreatment process, and after the washing treatment is completed, the positive plate is dried and cut into a positive unit of a preset size, and the preset size is 1-5 cm. 2

[0009] Preferably, in the step of recycling the positive unit by hydrothermal reaction, the positive unit is put into a hydrothermal reaction kettle, water is added, and the reaction is carried out at a temperature of 160-280 DEG C for 1-6 hours to obtain aluminum foil metal and positive material powder.

[0010] Preferably, the drying temperature of the positive plate is 60 DEG C.

[0011] Preferably, the negative plate is treated by water immersion to separate copper foil and negative material.

[0012] Preferably, the material in the hydrothermal reaction kettle is stirred at a stirring speed of 20-200 revolutions per minute.

[0013] Preferably, the pressure in the reaction kettle is 0.5-6.5 MPa.

[0014] The method for stripping positive material of waste lithium ion battery by subcritical water provided by the application has the characteristics of simplicity, high efficiency and environmental protection, is suitable for industrial application, has certain economic benefit and social benefit, has the advantages of environmental friendliness and energy saving and carbon reduction compared with the high-temperature pyrolysis or calcination method, has the characteristics of no harmful gas generation and low energy consumption, and has great industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The flow framework diagram of the method for stripping positive material of waste lithium ion battery by subcritical water provided by the embodiment of the application is shown. DETAILED DESCRIPTION

[0016] ​To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] like Figure 1 The diagram shown is a flowchart of a method for stripping waste lithium-ion battery cathode materials using subcritical water, according to an embodiment of the present invention. The method includes: Discharge the waste lithium-ion batteries and disassemble them into positive electrode plates, negative electrode plates and separators. The positive electrode sheet is pre-treated to form a positive electrode unit of a predetermined size. The positive electrode unit is then recycled through a hydrothermal reaction to obtain aluminum foil metal and positive electrode material powder.

[0018] In this embodiment, waste lithium-ion batteries are immersed in salt water for discharge, and positive electrode sheets, negative electrode sheets, and separators are obtained by manual disassembly. The positive electrode sheets are cleaned, dried, and cut to obtain positive electrode units. A certain amount of positive electrode units are added to a hydrothermal reactor, and a small amount of water is added. The reactor is then reacted at 160–280°C for 1–6 hours to obtain clean aluminum foil metal and black positive electrode material powder. During the hydrothermal reaction, the pressure inside the reactor is 0.5 MPa–6.5 MPa.

[0019] Preferably, during the hydrothermal reaction, the temperature is 240℃, the pressure is 3.3 MPa, the positive electrode is 20 g, the pure water is 20 mL, and the reaction time is 2 hours.

[0020] In this reaction, no chemical reagents are required, only water. In a closed reaction vessel at 160℃-280℃, water exists in a subcritical state (high temperature and high pressure). In terms of sequence, water can be added first and then the positive electrode, or the positive electrode can be added first and then water.

[0021] Reaction principle: The reduced polarity of subcritical water promotes the dissolution of the binder PVDF. Secondly, the increased ionization constant of subcritical water is beneficial to the hydrolysis of PVDF. Furthermore, subcritical water contains redox active species that can participate in the decomposition of PVDF.

[0022] When recycling the diaphragm, cut the diaphragm into pieces of 1-5 cm. 2 Add 10-100g of small cubes to the reaction vessel and add 10-50mL of water to carry out the reaction.

[0023] The water used in this invention is ultrapure water, delithium-ionized water, or tap water.

[0024] The waste lithium ion battery suitable for the application includes a ternary lithium battery, a lithium cobaltate lithium battery, a lithium manganate lithium battery and a Co-Al co-doped lithium nickel oxide lithium battery.

[0025] The salt water used in the application is a NaCl solution with a mass concentration of 5-10%, and the discharge time is 12-24 hours.

[0026] In the application, the positive plate is washed several times by dimethyl carbonate, dried, and cut into pieces.

[0027] In order to verify the effect of the application, the following comparative tests are used for verification: Example 1 A method for stripping positive electrode material of waste lithium ion battery by using subcritical water, steps are as follows: 1. The recovered waste lithium ion battery is discharged by salt water, then washed by ultrapure water and dried; 2. The battery is manually disassembled to obtain the battery shell, positive plate, negative plate and separator; 3. The positive plate is washed several times by dimethyl carbonate, dried, and cut into 2cm 2 small square pieces; 4. 20g of positive plate is added to the reaction kettle, 20mL of water is added, and the reaction is carried out at 280℃ for 2h to obtain clean aluminum foil metal and black positive material powder, the material is washed, dried and collected; 5. The negative electrode material and copper foil are separated by simple water immersion.

[0028] Example 2 A method for stripping positive electrode material of waste lithium ion battery by using subcritical water, steps are as follows: 1. The recovered waste lithium ion battery is discharged by salt water, then washed by ultrapure water and dried; 2. The battery is manually disassembled to obtain the battery shell, positive plate, negative plate and separator; 3. The positive plate is washed several times by dimethyl carbonate, dried, and cut into 2cm 2 small square pieces; 4. 20g of positive plate is added to the reaction kettle, 20mL of water is added, and the reaction is carried out at 240℃ for 2h to obtain clean aluminum foil metal and black positive material powder, the material is washed, dried and collected; 5. The negative electrode material and copper foil are separated by simple water immersion.

[0029] Example 3 A method for stripping positive electrode material of waste lithium ion battery by using subcritical water, steps are as follows: 1. The recovered waste lithium ion battery is discharged by salt water, then washed by ultrapure water and dried; 2. Manually disassemble the battery to obtain the battery casing, positive electrode plate, negative electrode plate, and separator; 3. After washing the positive electrode sheet several times with dimethyl carbonate, dry it and cut it into 2cm pieces. 2 Small square pieces; 4. Add 20g of positive electrode sheet to the reaction vessel, then add 20mL of water, and react at 200℃ for 2h to obtain clean aluminum foil metal and black positive electrode material powder. Wash, dry and collect the materials. 5. The negative electrode material and copper foil are separated by simple water immersion.

[0030] Example 4 A method for stripping cathode materials from spent lithium-ion batteries using subcritical water, comprising the following steps: 1. Discharge the recycled waste lithium-ion batteries with brine, then wash them with ultrapure water and dry them. 2. Manually disassemble the battery to obtain the battery casing, positive electrode plate, negative electrode plate, and separator; 3. After washing the positive electrode sheet several times with dimethyl carbonate, dry it and cut it into 2cm pieces. 2 Small square pieces; 4. Add 20g of positive electrode sheet to the reaction vessel, then add 20mL of water, and react at 160℃ for 2h to obtain clean aluminum foil metal and black positive electrode material powder. Wash, dry and collect the materials. 5. The negative electrode material and copper foil are separated by simple water immersion.

[0031] Comparative Example 1 1. Discharge the recycled waste lithium-ion batteries with brine, then wash them with ultrapure water and dry them; 2. Manually disassemble the battery to obtain the battery casing, positive electrode plate, negative electrode plate, and separator; 3. After washing the positive electrode sheet several times with dimethyl carbonate, dry it and cut it into 2cm pieces. 2 Small square pieces; 4. Add 20g of positive electrode sheet to the reaction vessel, then add 20mL of water, and react at 80℃ for 2h.

[0032] Comparative Example 2 1. Discharge the recycled waste lithium-ion batteries with brine, then wash them with ultrapure water and dry them. 2. Manually disassemble the battery to obtain the battery casing, positive electrode plate, negative electrode plate, and separator; 3. After washing the positive electrode sheet several times with dimethyl carbonate, dry it and cut it into 2cm pieces. 2 Small square pieces; 4. Add 20g of positive electrode sheet to the reaction vessel, then add 20mL of water, and react at 40℃ for 2h.

[0033] Relevant test data and comparisons: The statistics of each embodiment and each comparative example are shown in Table 1; Group Temperature Pressure Time Separation efficiency Example 1 280℃ 6.5 MPa 2h 100% Example 2 240℃ 3.3 MPa 2h 100% Example 3 200℃ 1.5 MPa 2h 96% Example 4 160℃ 0.5 MPa 2h 92% Comparative Example 1 80℃ 0.1 MPa 2h 24% Comparative Example 2 40℃ 0.1 MPa 2h 15% The data in Table 1 shows that: In Comparative Examples 1 and 2, there is a drawback that the separation efficiency decreases at lower temperatures.

[0034] In Examples 1-4, the separation efficiency of the positive electrode material and aluminum foil is higher than 90%, and the obtained positive electrode material contains no residual aluminum foil impurities. Compared with conventional pyrolysis methods, this method uses lower temperatures, does not emit harmful gases, can recover all components, and the material is not damaged, making it suitable for direct regeneration. This invention has advantages such as low cost, simple operation, short process, high economic benefits, and green sustainability.

[0035] This invention's method requires no chemical reagents; only water is added to bring the mixture to a subcritical state. By controlling parameters such as reaction temperature, stirring speed, and solid-liquid ratio, the cathode material can be exfoliated. Compared to traditional high-temperature calcination and organic solvent methods, this method offers significant advantages, particularly in reducing environmental pollution and energy consumption, providing a novel approach for cathode material exfoliation.

[0036] This method utilizes the special properties of subcritical water. The reaction principle is as follows: (1) Subcritical water changes from polar to nonpolar, and the principle of like dissolves like promotes the dissolution of organic binders; (2) The ionization constant of subcritical water increases, and the large number of free ions in the water promotes the hydrothermal hydrolysis of organic binders; (3) Subcritical water has a certain redox ability, and the redox species in the water are conducive to the oxidative degradation of organic binders.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for stripping waste lithium-ion battery cathode materials using subcritical water, characterized in that, The method includes: Discharge the waste lithium-ion batteries and disassemble them into positive electrode plates, negative electrode plates and separators. The positive electrode sheet is pre-treated to form a positive electrode unit of a predetermined size. The positive electrode unit is then recycled through a hydrothermal reaction to obtain aluminum foil metal and positive electrode material powder.

2. The method for stripping waste lithium-ion battery cathode materials using subcritical water according to claim 1, characterized in that, In the step of discharging the waste lithium-ion batteries and disassembling them into positive electrode plates, negative electrode plates and separators, the waste lithium-ion batteries are discharged by soaking in brine, wherein the brine is a NaCl solution with a mass concentration of 5% to 10%.

3. The method for stripping waste lithium-ion battery cathode materials using subcritical water according to claim 2, characterized in that, During the discharge treatment using brine, the discharge time is 12-24 hours.

4. The method for stripping waste lithium-ion battery cathode materials using subcritical water according to claim 1, characterized in that, In the step of pre-treating the positive electrode sheet to form positive electrode units of a predetermined size, the positive electrode sheet is washed multiple times with dimethyl carbonate during the pre-treatment process. After washing, the positive electrode sheet is dried, and then cut into positive electrode units of a predetermined size, with a size of 1-5 cm. 2 between.

5. The method for stripping waste lithium-ion battery cathode materials using subcritical water according to claim 1, characterized in that, In the step of recycling the positive electrode unit through hydrothermal reaction, the positive electrode unit is put into a hydrothermal reactor, water is added, and the reaction is carried out at a temperature of 160℃-280℃ for 1-6 hours to obtain aluminum foil metal and positive electrode material powder.

6. The method for stripping waste lithium-ion battery cathode materials using subcritical water according to claim 4, characterized in that, When drying the positive electrode, the drying temperature is 60℃.

7. The method for stripping waste lithium-ion battery cathode materials using subcritical water according to claim 1, characterized in that, The negative electrode sheet is subjected to water immersion treatment to separate copper foil and negative electrode material.

8. The method for stripping waste lithium-ion battery cathode materials using subcritical water according to claim 5, characterized in that, During the hydrothermal reaction, the materials inside the hydrothermal reactor are stirred at a speed of 20-200 revolutions per minute.

9. The method for stripping waste lithium-ion battery cathode materials using subcritical water according to claim 1, characterized in that, During the hydrothermal reaction, the pressure inside the reactor is between 0.5 MPa and 6.5 MPa.

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