A method for recovering metals from waste lithium-ion battery positive electrode materials

Abstract

The present invention discloses a method for recovering metals in positive electrode materials of waste lithium-ion batteries, comprising the following steps: placing an anode and a cathode in an electrolyte, applying a negative voltage to the cathode, and recovering metals in the electrode and / or the electrolyte; the cathode is a positive electrode material of waste lithium-ion batteries. The method for recovering metals in positive electrode materials of waste lithium-ion batteries provided by the present invention is applicable to various positive electrode materials of lithium-ion batteries, has universal applicability, and can avoid the complex pre-treatment process and highly polluting and energy-intensive operations such as strong acid and strong alkali leaching and high-temperature calcination in traditional recovery methods. It is not necessary to separate the active material particles in the positive electrode materials of the battery, and a single or multiple positive electrode sheets can be directly obtained from the disassembly of the waste lithium-ion batteries as cathodes, so that all valuable metals in the positive electrode materials of waste lithium-ion batteries can be efficiently recovered, which is clean and environmentally friendly, and easy to operate and low in cost.

Description

Technical Field

[0001] The invention relates to the field of recycling waste lithium-ion batteries, and in particular to a method for recycling metals in positive electrode materials of waste lithium-ion batteries. Background Art

[0002] The growing global energy demand and environmental pollution make the development of sustainable energy sources and storage technologies a top priority. Lithium-ion batteries, as an energy storage technology that integrates renewable resources and electric transportation, are developing rapidly. The production and sales of various electronic products and new energy vehicles are constantly increasing, which will inevitably lead to a sharp increase in the number of waste lithium-ion batteries. However, the materials used in lithium-ion batteries have certain inherent toxicity and are potentially harmful to the environment. In addition, the large-scale production of batteries consumes a lot of resources, especially some extremely scarce metal resources in positive electrode materials. The demand for key lithium elements such as lithium and cobalt is about to exceed their global reserves. Therefore, the demand for the recycling of key materials for sustainable batteries is crucial. The recycling of key lithium elements in positive electrode materials can not only reduce the harm of lithium-ion batteries to the environment, but also achieve the recycling of resources.

[0003] At present, the main methods for recycling positive electrode materials are: 1) Hydrometallurgy: disassemble the positive electrode materials of discarded batteries, separate the active material powder through complex pre-treatment steps, put the active material into a strong acid-reducing agent system for leaching, and obtain the final valuable metals through post-treatment such as precipitation or extraction. This method has a complicated pre-treatment process, needs to separate the active material particles in the electrode sheet, which is time-consuming. A large amount of chemical reagents are required in the process of dissolving the active material to produce a large amount of acidic waste liquid that pollutes the environment; 2) Pyrometallurgy: put the positive electrode active material separated by complex pre-treatment into a high temperature-reducing agent system to obtain a metal alloy, and then obtain valuable metals through post-treatment such as leaching, extraction, precipitation, etc. This method requires a cumbersome pre-treatment process, needs to separate the active material particles in the electrode sheet, requires high temperature, high energy consumption and produces a large amount of harmful gases.

[0004] The existing technology uses electrochemical methods to recover metals from positive electrode materials of lithium batteries. The positive electrode materials used are single and do not include positive electrode materials such as lithium iron phosphate, ternary composite materials, and lithium cobalt oxide; or they can only recover ion solutions of low value (such as lithium iron phosphate solutions); or they have high selectivity and can only migrate lithium under a certain potential, but are not sensitive to iron ions, aluminum ions, ammonium ions, cobalt ions, manganese ions, etc., and cannot solve the problem of recycling all valuable metals in the positive electrode materials of waste lithium-ion batteries. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a method for recovering metals in waste lithium-ion battery positive electrode materials. The method does not require separation of active material particles in the battery positive electrode materials, can avoid the complex pretreatment process in traditional recovery methods and highly polluting and energy-intensive operations such as strong acid and strong alkali leaching and high-temperature calcination, is clean and environmentally friendly, and is easy and simple to operate with low cost. All valuable metals in various waste lithium-ion battery positive electrode materials can be directly recycled.

[0006] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0007] A method for recovering metals from positive electrode materials of waste lithium-ion batteries comprises the following steps: placing an anode and a cathode in an electrolyte, applying a negative voltage to the cathode, and recovering metals from the electrode and / or the electrolyte; the cathode is a positive electrode material of a waste lithium-ion battery.

[0008] The method for recovering metals in waste lithium-ion battery positive electrode materials provided by the present invention does not require separation of active material particles in the battery positive electrode materials, can avoid the complex pretreatment process in traditional recovery methods and highly polluting and energy-intensive operations such as strong acid and strong alkali leaching and high-temperature calcination, is clean and environmentally friendly, and is easy and simple to operate with low cost. The recovery method achieves efficient recovery of all valuable metals in waste lithium-ion battery positive electrode materials by controlling factors such as the pH value, voltage value, temperature and time of the electrolyte.

[0009] Furthermore, the recycling method of the present invention is applicable to various lithium-ion battery positive electrode materials and has universal applicability. The waste lithium-ion battery positive electrode materials can be one or more of NCM ternary materials, lithium nickel manganese oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate, NCA ternary materials, lithium nickel oxide, lithium cobalt phosphate, quaternary materials and other lithium-ion battery positive electrode materials. These electrode materials can be directly disassembled from waste lithium-ion batteries to obtain positive electrode sheets without other treatment.

[0010] Furthermore, the cathode is a single positive electrode sheet or a plurality of positive electrode sheets connected in series.

[0011] In a specific embodiment, the method for recovering metals in the positive electrode material of waste lithium-ion batteries comprises the following steps:

[0012] (1) Dismantle the positive electrode sheet from the waste lithium-ion battery;

[0013] (2) preparing an electrolyte of a certain concentration and placing it in an electrolytic cell with an anode, and placing the waste lithium-ion battery positive electrode material in step (1) as a cathode in the electrolyte;

[0014] (3) Applying a negative voltage to the cathode for a certain period of time at a certain temperature to recover metals in the electrode and / or electrolyte.

[0015] Furthermore, the voltage applied to a single positive electrode sheet is -10 to 0 V, and the voltage applied to a plurality of positive electrode sheets connected in series is a multiple of the voltage applied to a single positive electrode sheet, and the reference electrode of the voltage is Hg / Hg 2 SO 4 Electrode, the potentials described in the present invention are all relative to this reference electrode, and the potentials of other reference electrodes can be calculated based on this potential.

[0016] Furthermore, the pH value of the electrolyte is ≤7, and the electrolyte can be any solution with a pH value ≤7, such as NH 4 Cl aqueous solution, ammonium formate (HCOONH 4 ) aqueous solution, NaHSO 4 Aqueous solution, NH 4 H 2 PO 4 Aqueous solution, KCl aqueous solution, sodium chloride (NaCl) solution, aluminum chloride (AlCl 3 ) solution, ferric chloride (FeCl 3 ) solution, etc. If the pH changes during the process, acid will be added to maintain the initial pH.

[0017] Furthermore, the pH value of the electrolyte is >7, and the electrolyte can be any solution with a pH value >7, such as KOH aqueous solution, NaOH aqueous solution, Na 2 CO 3 Aqueous solution, (NH 4 ) 2 HPO 4 Aqueous solution, NH 4 HCO 3 Solution, calcium hypochlorite (Ca(ClO) 2 ) solution, sodium hypochlorite (NaClO) solution, etc. If the pH changes during the process, alkali will be added to maintain the initial pH.

[0018] When the pH value of the electrolyte is ≤7 and the voltage applied to a single positive electrode sheet is less than -1.2V, metal elements such as lithium, cobalt, nickel, and manganese exist in the electrolyte in the form of ions. During the application of negative potential, the lithium in the positive electrode material will first dissolve and exist in the solution in the form of ions, and the remaining transition metal oxides will be reduced to a low-valent state and more easily soluble in acidic solutions, so cobalt, nickel, manganese and other metals will dissolve in the form of ions. Because the potential range at this time is not enough to reduce the metal ions in the electrolyte, all metal ions exist in the electrolyte in the form of ions.

[0019] When the pH value of the electrolyte is >7 and the voltage applied to a single positive electrode sheet is less than -1.2V, the lithium element exists in the electrolyte in the form of ions, and metal elements such as cobalt, nickel, manganese, and iron exist in the cathode in the form of solid metal oxides. During the application of a negative potential, the lithium in the positive electrode material will first dissolve and exist in the solution in the form of ions, and the remaining transition metal oxides are almost insoluble in alkaline solutions. Most of them exist in the original cathode in the form of solid metal oxides and can be separated and recycled.

[0020] When the pH value of the electrolyte is ≤7, and the voltage applied to a single positive electrode sheet is -10 to -1.2V, the lithium element exists in the electrolyte in the form of ions, and metal elements such as cobalt, nickel, and manganese are attached to the cathode surface in the form of solid metal elements. In the process of applying a negative potential, the lithium in the positive electrode material will first dissolve and exist in the solution in the form of ions, and the remaining transition metal oxides will be reduced to a low-valent state and more easily dissolved in an acidic solution, so cobalt, nickel, manganese and other metals will dissolve in the form of ions. At this time, the potential at -1.2 to -10V is relatively large, which can reduce the cobalt, nickel, and manganese in the solution to solid metal elements attached to the cathode surface. Therefore, the lithium element is in the electrolyte solution in the form of ions, and cobalt, nickel, manganese and other metal elements are attached to the cathode surface in the form of solid metal elements.

[0021] When the pH value of the electrolyte is > 7, and the voltage applied to a single positive electrode sheet is -10 to -1.2V, the lithium element exists in the electrolyte in the form of ions, and most of the metal elements such as cobalt, nickel, manganese, and iron exist in the positive electrode in the form of solid metal oxides, and a small part is attached to the cathode surface in the form of solid metal elements. In the process of applying a negative potential, the lithium in the positive electrode material will first dissolve and exist in the solution in the form of ions, and the remaining transition metal oxides are almost insoluble in alkaline solutions, and most of them exist in the original positive electrode in the form of solid metal oxides. However, when the negative potential increases, a small amount of transition metal on the surface can combine with hydroxide and be directly reduced to a solid metal element attached to the cathode surface.

[0022] Furthermore, the concentration of the electrolyte is 0.01 to 30 mol / L.

[0023] Furthermore, the applying voltage to the cathode is performed at 0-100°C.

[0024] Furthermore, the time for applying voltage to the cathode is 1 to 500 hours.

[0025] Furthermore, the anode is platinum, nickel, ruthenium, titanium, carbon or a composite electrode thereof, and can also be conductive materials such as stainless steel, copper oxide, positive and negative electrode sheets of waste batteries, etc.

[0026] Beneficial effects of the present invention:

[0027] (1) The present invention can avoid the complex pretreatment process and high-pollution and high-energy-consuming operations such as strong acid and strong alkali leaching and high-temperature calcination in traditional recovery methods, and is clean and environmentally friendly, thereby achieving efficient recovery of all valuable metals in the positive electrode material.

[0028] (2) The present invention does not need to separate the active material particles in the positive electrode material, and can directly recover the valuable metals in the positive electrode material. It is applicable to various waste lithium-ion battery positive electrode materials and has universal applicability. It can realize the recycling of all valuable metals in the positive electrode material. The recovery rate of all valuable metals is as high as 99.9% or more. The operation is convenient and simple, and the cost is low. DETAILED DESCRIPTION

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0030] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0031] The present invention provides a method for recovering metals in positive electrode materials of waste lithium-ion batteries, comprising the following steps: placing an anode and a cathode in an electrolyte, applying a negative voltage to the cathode, and recovering metals in the electrode and / or the electrolyte; the cathode is the positive electrode material of the waste lithium-ion battery.

[0032] The recycling method of the present invention is applicable to various lithium-ion battery positive electrode materials and has universal applicability. The waste lithium-ion battery positive electrode material can be one or more of NCM ternary materials, lithium nickel manganese oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate, NCA ternary materials, lithium nickel oxide, lithium cobalt phosphate, quaternary materials and other lithium-ion battery positive electrode materials. These electrode materials can be directly obtained from the disassembly of waste lithium-ion batteries without other treatment.

[0033] In a specific embodiment, the method for recovering metals in the positive electrode material of waste lithium-ion batteries comprises the following steps:

[0034] (1) Dismantle the positive electrode sheet from the waste lithium-ion battery;

[0035] (2) preparing an electrolyte of a certain concentration and placing it in an electrolytic cell with an anode, and placing the waste lithium-ion battery positive electrode material in step (1) as a cathode in the electrolyte;

[0036] (3) Applying a negative voltage to the cathode for a certain period of time at a certain temperature to recover metals in the electrode and / or electrolyte.

[0037] Example 1

[0038] A method for recovering metals from waste lithium-ion battery positive electrode materials comprises the following steps:

[0039] (1) Dismantle the LiNi in the discarded ternary material nickel-cobalt-manganese lithium-ion battery 0.8 Co 0.1 Mn 0.1 O 2 Electrode sheet;

[0040] The active material in the positive electrode material is weighed to be 15.7982 g, and the mass proportion of the valuable metals in the active material is shown in Table 1:

[0041] Table 1

[0042] Metallic elements Li Co Ni Mn Mass ratio (wt%) 7.1 6.1 48.3 5.5

[0043] (2) Prepare 1000 mL of 0.4 mol / L HCOONH at pH 4 4 The aqueous solution is placed in an electrolytic cell with graphite electrodes, and the LiNi 0.8 Co 0.1 Mn 0.1 O 2 The electrode sheet is used as cathode and the graphite electrode is used as anode, which are placed in the electrolyte;

[0044] (3) A voltage of -0.8 V was applied to the cathode at 100°C for 24 hours. Metal elements such as lithium, cobalt, nickel, and manganese existed in the electrolyte in the form of ions. The ICP-OES test showed that the concentration of lithium ions in the electrolyte was 0.1616 mol / L, the concentration of cobalt ions was 0.01635 mol / L, the concentration of nickel ions was 0.1300 mol / L, and the concentration of manganese ions was 0.01581 mol / L. It was calculated that the leaching rate of all valuable metals reached more than 99.9%. NaOH was added to the electrolyte until the pH of the electrolyte was 11 to obtain Ni x Co y Mn z (OH) 2 The coprecipitate is separated and the solid is recovered. This solid is the precursor for synthesizing the nickel manganese oxide positive electrode material again. The separated solution is added with Na 2 CO 3 You can get Li 2 CO 3 The solid was precipitated and recovered by centrifugation.

[0045] Example 2

[0046] A method for recovering metals from waste lithium-ion battery positive electrode materials comprises the following steps:

[0047] (1) Dismantle LiCoO from discarded lithium cobalt oxide lithium-ion batteries 2 Electrode sheet;

[0048] The active material in the positive electrode material is weighed to be 10.6873 g, and the mass proportion of the valuable metals in the active material is shown in Table 2:

[0049] Table 2

[0050] Metallic elements Li Co Mass ratio (wt%) 7.1 60.2

[0051] (2) Prepare 1000 mL of 5 mol / L NH 4 The Cl aqueous solution is placed in an electrolytic cell with a platinum (Pt) electrode, and the LiCoO 2 The electrode sheet is used as cathode and the Pt electrode is used as anode, which are placed in the electrolyte;

[0052] (3) A voltage of -2 V was applied to the cathode at 25°C for 48 h. The lithium element existed in the electrolyte in the form of ions. The concentration of lithium ions in the electrolyte measured by ICP-OES was 0.1093 mol / L. The calculated lithium ion leaching rate exceeded 99.9%. Na 2 CO 3 Lithium 2 CO 3 Solid precipitation was carried out and centrifugation was performed to recover the cobalt element. The cobalt element was attached to the cathode surface in the form of metal Co. The mass of the metal Co was weighed to be 6.4337 g. The cobalt ion leaching rate was calculated to be 100%. The metal Co attached to the cathode surface was directly scraped off and recovered in the form of solid metal Co.

[0053] Example 3

[0054] A method for recovering metals from waste lithium-ion battery positive electrode materials comprises the following steps:

[0055] (1) Dismantle the LiNi in the discarded ternary material nickel-cobalt-manganese lithium-ion battery 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 Electrode sheet;

[0056] The active material in the positive electrode material is weighed to be 0.3671 g, and the mass percentage of the valuable metals in the active material is shown in Table 3:

[0057] Table 3

[0058] Metallic elements Li Co Ni Mn Mass ratio (wt%) 7.3 20.4 20.3 19.0

[0059] (2) Prepare 1000 mL of 1 mol / L HCOONH at pH 4 4 The aqueous solution is placed in an electrolytic cell with a platinum (Pt) electrode, and the LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 The electrode sheet is used as cathode and the Pt electrode is used as anode, which are placed in the electrolyte;

[0060] (3) A voltage of -8 V was applied to the cathode at 0°C for 500 h. The lithium element existed in the electrolyte in the form of ions. The concentration of lithium ions in the electrolyte measured by ICP-OES was 26.798 ppm. The calculated lithium ion leaching rate reached 99.9%. Na 2 CO 3 Lithium 2 CO 3 Solid precipitation, centrifugal recovery; cobalt, nickel, manganese elements attached to the cathode surface in the form of metal single substance, the metal single substance attached to the cathode surface is directly scraped off, the mass of cobalt, nickel, manganese metal single substance is weighed to be 0.2191g, and the recovery rate of cobalt, nickel, manganese ions is calculated to reach 99.9%, and the scraped nickel, cobalt and manganese metal solid mixture is directly recovered.

[0061] Example 4

[0062] A method for recovering metals from waste lithium-ion battery positive electrode materials comprises the following steps:

[0063] (1) Dismantle the LiNi in discarded lithium nickel manganese oxide lithium ion batteries 0.5 Mn 1.5 O 4 Electrode sheet;

[0064] The active material in the positive electrode material is weighed to be 0.2095 g, and the mass percentage of the valuable metals in the active material is shown in Table 4:

[0065] Table 4

[0066] Metallic elements Li Ni Mn Mass ratio (wt%) 3.8 16.1 45.1

[0067] (2) Prepare 1000 mL of 0.8 mol / L Na 2 CO 3 The aqueous solution is placed in an electrolytic cell with graphite electrodes, and the LiNi 0.5 Mn 1.5 O 4 The electrode sheet is used as cathode and the graphite electrode is used as anode, which are placed in the electrolyte;

[0068] (3) A voltage of -0.6 V was applied to the cathode at 60 °C for 24 h. The lithium element existed in the electrolyte in the form of ions. The concentration of lithium ions in the electrolyte measured by ICP-OES was 7.96 ppm. The calculated lithium ion leaching rate reached 99.99%. The electrolyte was evaporated and concentrated to obtain Li 2 CO 3 Solid precipitation, centrifugal recovery; nickel and manganese metal elements exist in the positive electrode sheet in the form of solid metal oxides. XRD can prove that the positive electrode sheet has been completely converted into nickel-manganese mixed oxides, which can be directly recovered by ultrasonic centrifugation to obtain nickel-manganese mixed oxides.

[0069] Example 5

[0070] A method for recovering metals from waste lithium-ion battery positive electrode materials comprises the following steps:

[0071] (1) Dismantle the waste lithium cobalt oxide (LiCoO 2 )LiCoO in lithium-ion batteries 2 Electrode sheet;

[0072] The active material in the positive electrode material is weighed to be 0.0571 g, and the mass percentage of the valuable metals in the active material is shown in Table 5:

[0073] Table 5

[0074] Metallic elements Li Co Mass ratio (wt%) 7.1 60.2

[0075] (2) Prepare 1000 mL of 0.01 mol / L KOH aqueous solution with a pH of 13.8 and place it in an electrolytic cell with stainless steel electrodes. 2 The electrode sheet is used as cathode and the stainless steel electrode is used as anode, which are placed in the electrolyte;

[0076] (3) A voltage of -1.8 V was applied to the cathode at 60 °C for 10 h. The lithium element existed in the electrolyte in the form of ions. The lithium ion concentration in the electrolyte measured by ICP-OES was 4.054 ppm. The calculated lithium ion leaching rate was close to 99.9%. When H was added to the electrolyte, 3 PO 4 When the pH value is about 7, the lithium element is Li 3 PO 4 It exists in solid form and is recovered by centrifugation; the cobalt element exists in the form of metal Co and Co(OH) 2 The LiCoO in the positive electrode sheet is present in the cathode according to the XRD test results. 2 All converted into metallic cobalt and Co(OH) 2 The electrode sheets were separated by ultrasonic centrifugation, and the mixture was calcined at 500 °C in air for 4 h to obtain 46.82 mg of Co3 O 4 , and it was calculated that the recovery rate of cobalt element reached 99.9%.

[0077] Example 6

[0078] A method for recovering metals from waste lithium-ion battery positive electrode materials comprises the following steps:

[0079] (1) Dismantle the waste lithium cobalt oxide (LiCoO 2 )LiCoO in lithium-ion batteries 2 Electrode sheet;

[0080] The active material in the positive electrode material is weighed to be 0.0256 g, and the mass percentage of the valuable metals in the active material is shown in Table 6:

[0081] Table 6

[0082] Metallic elements Li Co Mass ratio (wt%) 7.1 60.2

[0083] (2) Prepare 1000 mL of 0.2 mol / L NH 4 H 2 PO 4 and (NH 4 ) 2 HPO 4 The buffered aqueous solution is placed in an electrolytic cell with stainless steel electrodes, and the LiCoO 2 The electrode sheet is used as cathode and the stainless steel electrode is used as anode, which are placed in the electrolyte;

[0084] (3) A voltage of -0.5 V was applied to the cathode at 95°C for 15 h. Lithium and cobalt elements were present in the electrolyte in the form of ions. The concentration of lithium ions in the electrolyte measured by ICP-OES was 1.8176 ppm, and the concentration of cobalt ions was 15.411 ppm. It was calculated that the leaching rate of lithium ions and cobalt ions reached 99.9%. NaOH was added to adjust the electrolyte to pH = 9, and Co(OH) was obtained by concentration. 2 The precipitate was recovered by centrifugation and Na 2 CO 3 You can get Li 2 CO 3 , and recover the product by centrifugation.

[0085] Example 7

[0086] A method for recovering metals from waste lithium-ion battery positive electrode materials comprises the following steps:

[0087] (1) Dismantle the waste lithium cobalt oxide (LiCoO 2 ) Two LiCoO sheets in a lithium-ion battery 2Electrode sheet;

[0088] The active material in the positive electrode material is weighed to be 10.716 g, and the mass percentage of the valuable metals in the active material is shown in Table 7:

[0089] Table 7

[0090]

[0091]

[0092] (2) Prepare 1000 mL of 30 mol / L NaHSO at pH 4 4 The buffered aqueous solution is placed in an electrolytic cell with stainless steel electrodes, and the LiCoO 2 The electrode sheet is used as cathode and the stainless steel electrode is used as anode, which are placed in the electrolyte;

[0093] (3) A voltage of -4 V was applied to the cathode at 40 °C for 150 h, which was equivalent to a voltage of -2 V applied to each electrode sheet. The lithium element existed in the electrolyte in the form of ions. The lithium ion concentration in the electrolyte measured by ICP-OES was 760.83 ppm. The calculated lithium ion leaching rate was 99.9%. After the electrolyte was concentrated and crystallized, the lithium element was present in the form of Li 2 SO 4 It exists in solid form and is recovered by centrifugation. The cobalt element is attached to the anode in the form of metallic Co, which can be directly recovered by scraping it off. The weight is 6.451 g, and the recovery rate is calculated to be 99.99%.

[0094] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A method for recovering metals from cathode materials of waste lithium-ion batteries. It is characterized in that The following steps are involved: Placing the anode and cathode in an electrolyte, applying a negative voltage to the cathode, and recovering metals in the electrode and / or the electrolyte; the cathode is a positive electrode material of a waste lithium-ion battery, and the cathode is a single positive electrode sheet or a plurality of positive electrode sheets connected in series; The pH value of the electrolyte is ≤ 7, the voltage applied to a single positive electrode sheet is: -1.2 V < voltage ≤ 0 V, and lithium, cobalt, nickel, and manganese exist in the electrolyte in the form of ions; When the pH value of the electrolyte is ≤ 7, the voltage applied to a single positive electrode sheet is: -10 V ≤ voltage ≤ -1.2 V, the lithium element exists in the electrolyte in the form of ions, and cobalt, nickel, and manganese are attached to the cathode surface in the form of solid metal elements; The pH value of the electrolyte is > 7, the voltage applied to a single positive electrode sheet is: -1.2 V < voltage ≤ 0 V, the lithium element exists in the electrolyte in the form of ions, and cobalt, nickel, manganese, and iron exist in the cathode in the form of solid metal oxides; The pH value of the electrolyte is > 7, and the voltage applied to a single positive electrode sheet is: -10 V ≤ voltage ≤ -1.2 V. The lithium element exists in the electrolyte in the form of ions, and most of the cobalt, nickel, manganese, and iron exist in the original positive electrode in the form of solid metal oxides. When the negative potential increases, a small amount of transition metal on the surface can combine with hydroxide and be directly reduced to a solid metal element attached to the cathode surface.

2. The method for recovering metals from cathode materials of waste lithium-ion batteries according to claim 1, It is characterized in that The positive electrode material of the waste lithium-ion battery is one or more of NCM ternary material, lithium nickel manganese oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate, NCA ternary material, lithium nickel oxide, lithium cobalt phosphate, and quaternary material.

3. The method for recovering metals from cathode materials of waste lithium-ion batteries according to claim 1, It is characterized in that The source of the positive electrode material of the waste lithium-ion battery is the positive electrode sheet after the waste lithium-ion battery is disassembled.

4. The method for recovering metals from waste lithium-ion battery positive electrode materials according to claim 1, It is characterized in that The concentration of the electrolyte is 0.01-30 mol / L.

5. The method for recovering metals from waste lithium-ion battery positive electrode materials according to claim 1, It is characterized in that The voltage is applied to the cathode at 0-100°C for 1-500 hours.

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