A membrane separation and concentration method for recycling positive electrode materials of waste lithium batteries and application thereof

Abstract

The present application relates to the technical field of membrane method waste lithium battery recycling, and particularly relates to a membrane separation and concentration method for recovering positive electrode material of waste lithium battery and application thereof. The method comprises the following steps: mixing the positive electrode material of the waste lithium battery after discharging and disassembling with acid liquor and a reducing agent solution, and then performing heating and stirring treatment, filtering insoluble substances, and obtaining leaching liquor; pumping the leaching liquor into a primary nanofiltration membrane system for primary nanofiltration treatment, obtaining primary nanofiltration water and primary nanofiltration concentrated liquid; pumping the primary nanofiltration water into a secondary nanofiltration membrane system for secondary nanofiltration treatment, obtaining secondary nanofiltration water and secondary nanofiltration concentrated liquid; and pumping the secondary nanofiltration water into a reverse osmosis system for reverse osmosis concentration treatment, obtaining reverse osmosis water and reverse osmosis concentrated liquid. The application is the application of the method in recovering lithium ions in the positive electrode material of the waste lithium battery. The present application can efficiently, highly and at low cost recover each metal cation in the positive electrode material of the waste lithium battery.

Description

Technical Field

[0001] This invention relates to the field of membrane-based waste lithium battery recycling technology, and in particular to a membrane separation and concentration method and its application for recycling positive electrode materials from waste lithium batteries. Background Technology

[0002] Lithium-ion batteries have been widely used in new energy vehicles, 3C electronics, and electrochemical energy storage due to their advantages such as high energy density, long lifespan, and environmental friendliness. However, with the widespread use of lithium-ion batteries, the waste lithium battery recycling industry has emerged.

[0003] Existing waste lithium battery recycling methods generally suffer from complex processes, high energy consumption, and high recycling costs. For example, Chinese invention patent CN106848471A discloses a mixed acid leaching and recovery method for metal components in the cathode material of waste lithium-ion batteries. The method involves coarsely crushing and drying the waste material, pre-leaching it with a mixed acid containing a reducing agent, ball milling the pre-separated residue, and then performing primary and secondary leaching. The primary and secondary leaching solutions are mixed with the pre-leaching solution, pH is adjusted, and the solution is filtered to obtain aluminum hydroxide and a cobalt- and lithium-containing residual liquid. The cobalt- and lithium-containing residual liquid is then pH-adjusted at high temperature and filtered again to obtain cobalt hydroxide and a lithium-containing residual liquid. The lithium-containing residual liquid is concentrated at high temperature, and a saturated sodium carbonate solution is added to obtain high-purity lithium carbonate. While this recycling method can recover high-purity lithium carbonate, it requires repeated pH adjustments, making the process complex. Furthermore, the need for high-temperature pH adjustment and high-temperature concentration of the lithium-containing residual liquid results in high energy consumption and high recycling costs.

[0004] In recent years, membrane technology has also been applied to the recycling of spent lithium batteries. However, the membrane materials used in this process have poor acid resistance, while the leaching solution for the cathode material of spent lithium batteries is an acidic solution, which directly limits the application of existing membrane technologies. Furthermore, membrane materials with poor acid resistance have a short lifespan in spent lithium battery recycling operations, requiring frequent replacement and resulting in high recycling costs.

[0005] Therefore, it is necessary to provide a membrane separation and concentration method and its application for recycling waste lithium battery cathode materials to solve the problems of 1) existing recycling methods requiring high-temperature pH adjustment and high-temperature concentration of lithium-containing residual liquid, resulting in high energy consumption and high recycling costs; and 2) the problem of high recycling costs caused by the poor acid resistance of membrane materials in existing membrane processes. Summary of the Invention

[0006] The purpose of this invention is to provide a membrane separation and concentration method for recycling cathode materials from waste lithium batteries and its application. The specific technical solution is as follows:

[0007] In a first aspect, the present invention provides a membrane separation and concentration method for recycling waste lithium battery cathode materials, comprising:

[0008] Step S1: Mix the discharged and disassembled waste lithium battery positive electrode material with acid and reducing agent solution, then heat and stir the mixture, and filter out the insoluble matter to obtain an extract; wherein the extract contains trivalent cations, divalent cations and monovalent cations; the monovalent cations include lithium ions from the waste lithium battery positive electrode material; the molar concentration of the acidic solute in the acid solution is 1~5 mol / L; and the mass of the waste lithium battery positive electrode material in each liter of the acid solution is 0.05~0.3 kg;

[0009] Step S2: The extract is pumped into a primary nanofiltration membrane system for primary nanofiltration treatment to obtain primary nanofiltration permeate and primary nanofiltration concentrate; the primary nanofiltration permeate contains the divalent cation and the monovalent cation; the primary nanofiltration concentrate contains the concentrated trivalent cation; the nanofiltration membrane used in the primary nanofiltration membrane system is an acid-resistant positively charged nanofiltration membrane; the molecular weight cutoff of the acid-resistant positively charged nanofiltration membrane is 280~300 Da;

[0010] Step S3: Pump the primary nanofiltration permeate into a secondary nanofiltration membrane system for secondary nanofiltration treatment to obtain secondary nanofiltration permeate and secondary nanofiltration concentrate; the secondary nanofiltration permeate contains monovalent cations; the secondary nanofiltration concentrate contains concentrated divalent cations; the nanofiltration membrane used in the secondary nanofiltration membrane system is an acid-resistant negatively charged nanofiltration membrane; the molecular weight cutoff of the acid-resistant negatively charged nanofiltration membrane is 180~200 Da;

[0011] Step S4: Pump the secondary nanofiltration permeate into the reverse osmosis system for reverse osmosis concentration treatment to obtain reverse osmosis permeate and reverse osmosis concentrate; the reverse osmosis concentrate contains concentrated monovalent cations; the reverse osmosis membrane used in the reverse osmosis system is an acid-resistant reverse osmosis membrane; the acid-resistant reverse osmosis membrane has a sodium chloride rejection rate of more than 99.7%.

[0012] Optionally, the acidic solute includes at least one of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, citric acid, and oxalic acid.

[0013] Optionally, the reducing agent solution comprises an aqueous solution of hydrogen peroxide; the mass percentage of hydrogen peroxide in the aqueous solution is 30%; and the volume ratio of the aqueous solution of hydrogen peroxide to the acid solution is 2:100.

[0014] Optionally, the heating and stirring process uses a heating temperature of 70-80℃, a stirring rate of 100-1000rpm, and a heating and stirring time of 10-100min.

[0015] Optionally, the primary nanofiltration membrane system includes one primary nanofiltration membrane element or multiple primary nanofiltration membrane elements connected in series; the operating pressure in the primary nanofiltration membrane system is 1~4MPa; and the nanofiltration membrane used in the primary nanofiltration membrane element is the acid-resistant positively charged nanofiltration membrane.

[0016] The trivalent cations include trivalent aluminum ions.

[0017] Optionally, the secondary nanofiltration membrane system includes one secondary nanofiltration membrane element or multiple secondary nanofiltration membrane elements connected in series; the operating pressure in the secondary nanofiltration membrane system is 2~6MPa; and the nanofiltration membrane used in the secondary nanofiltration membrane element is the acid-resistant negatively charged nanofiltration membrane.

[0018] The divalent cations include divalent copper ions.

[0019] Optionally, the reverse osmosis system includes one or more reverse osmosis membrane elements connected in series; the operating pressure in the reverse osmosis system is 4~10MPa; and the reverse osmosis membrane used in the reverse osmosis element is the acid-resistant reverse osmosis membrane.

[0020] Optionally, the acid-resistant positive charge nanofiltration membrane, the acid-resistant negative charge nanofiltration membrane, and the acid-resistant reverse osmosis membrane are all commercially available products.

[0021] Optionally, the trivalent cation in the primary nanofiltration concentrate is 1.2 to 5 times that in the extract;

[0022] The divalent cations in the secondary nanofiltration concentrate are 1.2 to 10 times more numerous than the divalent cations in the primary nanofiltration permeate;

[0023] The monovalent cations in the reverse osmosis concentrate are 1.2 to 2 times the number of monovalent cations in the secondary nanofiltration permeate.

[0024] In a second aspect, the present invention provides an application of the membrane separation and concentration method for recycling waste lithium battery cathode materials in the recovery of lithium ions from waste lithium battery cathode materials.

[0025] The application of the technical solution of the present invention has at least the following beneficial effects:

[0026] (1) The present invention provides a membrane separation and concentration method for recycling waste lithium battery cathode materials, which can efficiently, efficiently, and at low cost recover various metal cations in waste lithium battery cathode materials. Specifically, in this invention, the leachate obtained in step S1 fully dissolves the monovalent, divalent, and trivalent cations in the waste lithium battery cathode material. The monovalent cations include lithium ions from the waste lithium battery cathode material, ensuring that lithium ions are fully recovered in subsequent steps and improving the recovery rate. In step S2, the first-stage nanofiltration process uses an acid-resistant positively charged nanofiltration membrane with a molecular weight cutoff of 280-300 Da. This allows monovalent and divalent cations to pass through the membrane pores to form first-stage nanofiltration permeate, while blocking trivalent cations. Furthermore, the positive charge of the acid-resistant positively charged nanofiltration membrane further synergistically blocks trivalent cations, ensuring that they are efficiently and effectively blocked into the first-stage nanofiltration concentrate. Moreover, the acid resistance of the acid-resistant positively charged nanofiltration membrane ensures its tolerance to acidic leachates, extending its service life and ensuring long-term stable operation while reducing membrane stress. Cost: In the secondary nanofiltration process, this invention uses an acid-resistant negatively charged nanofiltration membrane with a molecular weight cutoff of 180-200 Da. This allows monovalent cations from the primary nanofiltration permeate to pass through the membrane pores while blocking divalent cations. Furthermore, the negative charge of the acid-resistant negatively charged nanofiltration membrane further synergistically allows monovalent cations to pass through, ensuring that they are fully and efficiently introduced into the secondary nanofiltration permeate. Additionally, the acid resistance of the membrane ensures its tolerance to acidic primary nanofiltration permeate, extending its service life and ensuring long-term stable operation, thus reducing membrane costs. Building upon the use of acid-resistant positively charged and negatively charged nanofiltration membranes, this invention employs an acid-resistant reverse osmosis membrane in the reverse osmosis concentration process. This ensures long-term, stable, and effective concentration and enrichment of monovalent cations in the secondary nanofiltration permeate, thereby enabling long-term, stable, and effective recovery of lithium ions from waste lithium battery cathode materials, reducing operating costs. Therefore, the combined use of steps S1-S4 in this invention achieves high efficiency, high recovery rate, and low cost recovery of lithium ions from waste lithium battery cathode materials.

[0027] (2) The present invention controls the trivalent cations in the primary nanofiltration concentrate to be 1.2 to 5 times that in the extract, which facilitates the concentration and recovery of trivalent cations; controls the divalent cations in the secondary nanofiltration concentrate to be 1.2 to 10 times that in the primary nanofiltration permeate, which facilitates the concentration and recovery of divalent cations; the present invention combines primary nanofiltration and secondary nanofiltration treatment, which can effectively retain trivalent and divalent cations, thereby purifying monovalent cations (such as lithium ions). The present invention controls the monovalent cations in the reverse osmosis concentrate to be 1.2 to 2 times that in the secondary nanofiltration permeate, which facilitates the concentration and recovery of purified monovalent cations (such as lithium ions). Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1:

[0030] A membrane separation and concentration method for recycling waste lithium battery cathode materials includes:

[0031] Step S1: The discharged and disassembled waste lithium battery positive electrode material is mixed with acid and reducing agent solution, and then heated and stirred. The insoluble matter is filtered to obtain an extract. The extract contains trivalent cations (such as trivalent aluminum ions), divalent cations (such as divalent copper ions), and monovalent cations. The monovalent cations include lithium ions from the waste lithium battery positive electrode material. The molar concentration of the acidic solute in the acid solution is 1 mol / L. The mass of the waste lithium battery positive electrode material in each liter of acid solution is 0.098 kg.

[0032] Step S2: The extract is pumped into a primary nanofiltration membrane system for primary nanofiltration treatment to obtain primary nanofiltration permeate and primary nanofiltration concentrate; the primary nanofiltration permeate contains the divalent cation and the monovalent cation; the primary nanofiltration concentrate contains the concentrated trivalent cation; the nanofiltration membrane used in the primary nanofiltration membrane system is an acid-resistant positively charged nanofiltration membrane; the molecular weight cutoff of the acid-resistant positively charged nanofiltration membrane is 280~300 Da;

[0033] Step S3: Pump the primary nanofiltration permeate into a secondary nanofiltration membrane system for secondary nanofiltration treatment to obtain secondary nanofiltration permeate and secondary nanofiltration concentrate; the secondary nanofiltration permeate contains monovalent cations; the secondary nanofiltration concentrate contains concentrated divalent cations; the nanofiltration membrane used in the secondary nanofiltration membrane system is an acid-resistant negatively charged nanofiltration membrane; the molecular weight cutoff of the acid-resistant negatively charged nanofiltration membrane is 180~200 Da;

[0034] Step S4: Pump the secondary nanofiltration permeate into the reverse osmosis system for reverse osmosis concentration treatment to obtain reverse osmosis permeate and reverse osmosis concentrate; the reverse osmosis concentrate contains concentrated monovalent cations; the reverse osmosis membrane used in the reverse osmosis system is an acid-resistant reverse osmosis membrane; the acid-resistant reverse osmosis membrane has a sodium chloride rejection rate of more than 99.7%.

[0035] The acidic solute is sulfuric acid.

[0036] The reducing agent solution is an aqueous solution of hydrogen peroxide; the mass percentage of hydrogen peroxide in the aqueous solution is 30%; the volume ratio of the aqueous solution of hydrogen peroxide to the acid solution is 2:100.

[0037] The heating and stirring process uses a heating temperature of 75°C, a stirring rate of 100~1000 rpm (specifically 600 rpm), and a heating and stirring time of 10~100 min (specifically 30 min).

[0038] The primary nanofiltration membrane system uses a single primary nanofiltration membrane element, model 2540; the operating pressure in the primary nanofiltration membrane system is 1~4MPa; the nanofiltration membrane used in the primary nanofiltration membrane element is the acid-resistant positive charge nanofiltration membrane (specifically, ASNF product manufactured by Hunan Aowei Technology Co., Ltd.).

[0039] The secondary nanofiltration membrane system uses a single secondary nanofiltration membrane element, model 2540; the operating pressure in the secondary nanofiltration membrane system is 2~6MPa; the nanofiltration membrane used in the secondary nanofiltration membrane element is the acid-resistant negative charge nanofiltration membrane (specifically, ACNF product manufactured by Hunan Aowei Technology Co., Ltd.).

[0040] The reverse osmosis system uses a reverse osmosis membrane element, model 2540; the operating pressure in the reverse osmosis system is 4~10MPa; the reverse osmosis membrane used in the reverse osmosis element is the acid-resistant reverse osmosis membrane.

[0041] The acid-resistant positive charge nanofiltration membrane, the acid-resistant negative charge nanofiltration membrane, and the acid-resistant reverse osmosis membrane are all commercially available products.

[0042] The trivalent cations in the primary nanofiltration concentrate are 1.2 to 5 times greater than those in the extract.

[0043] The divalent cations in the secondary nanofiltration concentrate are 1.2 to 10 times more numerous than the divalent cations in the primary nanofiltration permeate;

[0044] The monovalent cations in the reverse osmosis concentrate are 1.2 to 2 times the number of monovalent cations in the secondary nanofiltration permeate.

[0045] Comparative Example 1:

[0046] Unlike Example 1, the first-stage nanofiltration process in step S2 is omitted.

[0047] Comparative Example 2:

[0048] Unlike Example 1, the secondary nanofiltration process in step S3 is omitted.

[0049] Comparative Example 3:

[0050] Unlike Example 1, the acid-resistant negatively charged nanofiltration membrane has a molecular weight cutoff of 200~220 Da.

[0051] Comparative Example 4:

[0052] Unlike Example 1, the acid-resistant negatively charged nanofiltration membrane has a molecular weight cutoff of 135~180 Da.

[0053] Comparative Example 5:

[0054] Unlike Example 1, the acid-resistant positively charged nanofiltration membrane has a molecular weight cutoff of 300~500 Da.

[0055] Comparative Example 6:

[0056] Unlike Example 1, the acid-resistant positively charged nanofiltration membrane has a molecular weight cutoff of 220~280 Da.

[0057] In the membrane separation and concentration processes of Examples 1 and 1-6, samples of the nanofiltration permeate after primary and / or secondary nanofiltration treatments were taken and tested. The test results are shown in Table 1 (Table 1 also shows the concentrations of monovalent lithium ions, divalent copper ions, and trivalent aluminum ions in the extract; Table 1 also shows the operating pressures corresponding to the primary and secondary nanofiltration treatments). The testing instrument was an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0058] Table 1 Test Results

[0059]

[0060] From the data in Table 1, we know that:

[0061] Compared with Example 1, Comparative Example 1 omits the primary nanofiltration process in step S2, making it impossible to remove trivalent aluminum ions through primary nanofiltration. Consequently, in the secondary nanofiltration process, both divalent copper ions and trivalent aluminum ions are simultaneously retained by the acid-resistant negatively charged nanofiltration membrane in the secondary nanofiltration membrane element, making effective separation of divalent copper ions and trivalent aluminum ions impossible. At the same time, because both divalent copper ions and trivalent aluminum ions are simultaneously retained by the acid-resistant negatively charged nanofiltration membrane in the secondary nanofiltration membrane element, the operating pressure of the secondary nanofiltration membrane element increases significantly from 3.8 MPa in Example 1 to 6.9 MPa. This causes the acid-resistant negatively charged nanofiltration membrane to be compressed by the high operating pressure, resulting in smaller membrane pores and a significant decrease in the permeability of monovalent lithium ions.

[0062] Compared with Example 1, Comparative Example 2 omits the secondary nanofiltration process in step S3, thus failing to effectively separate divalent copper ions and monovalent lithium ions, and consequently failing to obtain purified monovalent lithium ions.

[0063] Compared with Example 1, Comparative Example 3 increased the molecular weight cutoff of the acid-resistant negatively charged nanofiltration membrane in the secondary nanofiltration process, resulting in a decrease in the retention rate of divalent copper ions. That is, some divalent copper ions passed through the acid-resistant negatively charged nanofiltration membrane along with monovalent lithium ions, thereby reducing the purity of monovalent lithium ions. On the other hand, the permeability of monovalent lithium ions in the secondary nanofiltration permeate increased because, based on the increased molecular weight cutoff of the acid-resistant negatively charged nanofiltration membrane, combined with its negative charge, it can further synergistically allow monovalent lithium ions to pass through, thereby increasing the permeability of monovalent lithium ions.

[0064] Compared with Example 1, Comparative Example 4 reduced the molecular weight cutoff of the acid-resistant negatively charged nanofiltration membrane in the secondary nanofiltration process, resulting in the retention of some monovalent lithium ions by the acid-resistant negatively charged nanofiltration membrane. This not only reduced the permeability of monovalent lithium ions, but also resulted in the retained divalent copper ion concentrate containing more monovalent lithium ions, making it impossible to achieve effective separation of divalent copper ions and monovalent lithium ions.

[0065] Compared with Example 1, Comparative Example 5 increased the molecular weight cutoff of the acid-resistant positive charge nanofiltration membrane in the first-stage nanofiltration process, causing some trivalent aluminum ions to pass through the acid-resistant positive charge nanofiltration membrane. As a result, the divalent copper ion concentrate retained after the second-stage nanofiltration process still contained a large number of trivalent aluminum ions, meaning that the divalent copper ions and trivalent aluminum ions could not be effectively separated.

[0066] Compared with Example 1, Comparative Example 6 reduced the molecular weight cutoff of the acid-resistant positively charged nanofiltration membrane in the primary nanofiltration process. As a result, some divalent copper ions were retained by the acid-resistant positively charged nanofiltration membrane, resulting in a large amount of divalent copper ions remaining in the retained trivalent aluminum ion concentrate. This meant that trivalent aluminum ions and divalent copper ions could not be effectively separated. At the same time, with the reduced molecular weight cutoff of the acid-resistant positively charged nanofiltration membrane, combined with its positive charge, some monovalent lithium ions were retained, thereby reducing the monovalent lithium ion permeability.

[0067] Compared with Comparative Examples 1 to 6, it is evident that the present invention, in Example 1, combines an acid-resistant positive charge nanofiltration membrane and an acid-resistant negative charge nanofiltration membrane with suitable molecular weight cutoff, which can effectively separate trivalent aluminum ions, divalent copper ions, and monovalent lithium ions, achieving high-efficiency, high-recovery-rate, and low-cost recovery of various metal cations in waste lithium battery cathode materials.

[0068] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A membrane separation and concentration method for recycling waste lithium battery cathode materials, characterized in that, include: Step S1: Mix the discharged and disassembled waste lithium battery positive electrode material with acid and reducing agent solution, then heat and stir the mixture, and filter out the insoluble matter to obtain an extract; wherein the extract contains trivalent cations, divalent cations and monovalent cations; the monovalent cations include lithium ions from the waste lithium battery positive electrode material; the molar concentration of the acidic solute in the acid solution is 1~5 mol / L; and the mass of the waste lithium battery positive electrode material in each liter of the acid solution is 0.05~0.3 kg; Step S2: The extract is pumped into a primary nanofiltration membrane system for primary nanofiltration treatment to obtain primary nanofiltration permeate and primary nanofiltration concentrate; the primary nanofiltration permeate contains the divalent cation and the monovalent cation; the primary nanofiltration concentrate contains the concentrated trivalent cation; the nanofiltration membrane used in the primary nanofiltration membrane system is an acid-resistant positively charged nanofiltration membrane; the molecular weight cutoff of the acid-resistant positively charged nanofiltration membrane is 280~300 Da; Step S3: Pump the primary nanofiltration permeate into a secondary nanofiltration membrane system for secondary nanofiltration treatment to obtain secondary nanofiltration permeate and secondary nanofiltration concentrate; the secondary nanofiltration permeate contains monovalent cations; the secondary nanofiltration concentrate contains the concentrated divalent cations; the nanofiltration membrane used in the secondary nanofiltration membrane system is an acid-resistant negatively charged nanofiltration membrane; the molecular weight cutoff of the acid-resistant negatively charged nanofiltration membrane is 180~200 Da; Step S4: Pump the secondary nanofiltration permeate into the reverse osmosis system for reverse osmosis concentration treatment to obtain reverse osmosis permeate and reverse osmosis concentrate; the reverse osmosis concentrate contains the concentrated monovalent cation; the reverse osmosis membrane used in the reverse osmosis system is an acid-resistant reverse osmosis membrane; the acid-resistant reverse osmosis membrane has a sodium chloride rejection rate of more than 99.7%.

2. The membrane separation and concentration method for recycling waste lithium battery cathode materials as described in claim 1, characterized in that, The acidic solute includes at least one of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, citric acid, and oxalic acid.

3. The membrane separation and concentration method for recycling waste lithium battery cathode materials as described in claim 1, characterized in that, The reducing agent solution includes an aqueous solution of hydrogen peroxide; the mass percentage of hydrogen peroxide in the aqueous solution of hydrogen peroxide is 30%; the volume ratio of the aqueous solution of hydrogen peroxide to the acid solution is 2:

100.

4. The membrane separation and concentration method for recycling waste lithium battery cathode materials as described in claim 1, characterized in that, The heating and stirring process uses a heating temperature of 70-80℃, a stirring rate of 100-1000rpm, and a heating and stirring time of 10-100min.

5. The membrane separation and concentration method for recycling waste lithium battery cathode materials as described in any one of claims 1 to 4, characterized in that, The primary nanofiltration membrane system includes one primary nanofiltration membrane element or multiple primary nanofiltration membrane elements connected in series; the operating pressure in the primary nanofiltration membrane system is 1~4MPa; the nanofiltration membrane used in the primary nanofiltration membrane element is the acid-resistant positively charged nanofiltration membrane. The trivalent cations include trivalent aluminum ions.

6. The membrane separation and concentration method for recycling waste lithium battery cathode materials as described in claim 5, characterized in that, The secondary nanofiltration membrane system includes one secondary nanofiltration membrane element or multiple secondary nanofiltration membrane elements connected in series; the operating pressure in the secondary nanofiltration membrane system is 2~6MPa; the nanofiltration membrane used in the secondary nanofiltration membrane element is the acid-resistant negatively charged nanofiltration membrane. The divalent cations include divalent copper ions.

7. The membrane separation and concentration method for recycling waste lithium battery cathode materials as described in claim 6, characterized in that, The reverse osmosis system includes one or more reverse osmosis membrane elements connected in series; the operating pressure in the reverse osmosis system is 4~10MPa; the reverse osmosis membrane used in the reverse osmosis membrane element is the acid-resistant reverse osmosis membrane.

8. The membrane separation and concentration method for recycling waste lithium battery cathode materials as described in claim 7, characterized in that, The acid-resistant positive charge nanofiltration membrane, the acid-resistant negative charge nanofiltration membrane, and the acid-resistant reverse osmosis membrane are all commercially available products.

9. The membrane separation and concentration method for recycling waste lithium battery cathode materials as described in claim 8, characterized in that, The trivalent cations in the primary nanofiltration concentrate are 1.2 to 5 times greater than those in the extract. The divalent cations in the secondary nanofiltration concentrate are 1.2 to 10 times more numerous than the divalent cations in the primary nanofiltration permeate; The monovalent cations in the reverse osmosis concentrate are 1.2 to 2 times the number of monovalent cations in the secondary nanofiltration permeate.

10. The application of the membrane separation and concentration method for recycling waste lithium battery cathode materials as described in claim 9 in the recycling of lithium ions from waste lithium battery cathode materials.

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