Method for separating and recycling lithium and cobalt in lithium cobalt oxide positive plate and application

Abstract

The invention provides a method for separating and recycling lithium and cobalt in a lithium cobalt oxide positive plate and application. The method for separating and recycling lithium and cobalt in the lithium cobalt oxide positive plate comprises the following steps: disassembling a waste battery to obtain a lithium cobalt oxide positive plate; a lithium cobalt oxide positive pole piece is used as a cathode of an electrolysis system, a platinum metal electrode is used as an anode of the electrolysis system, an extracting agent-sulfuric acid mixed solution is used as electrolyte for electrolysis to obtain a water phase and an organic phase, and the extracting agent-sulfuric acid mixed solution comprises dilute sulfuric acid and a composite extracting agent. The composite extraction agent comprises 2-ethylhexyl phosphoric acid-2-ethylhexyl ester and bis (2, 4, 4-trimethylpentyl) phosphonic acid, and the volume ratio of an organic phase to a water phase in the extraction agent-sulfuric acid mixed solution is 1: (1-3); and recovering the water phase to obtain a Li2SO4 solution, and carrying out back extraction on the organic phase to obtain a cobalt-containing solution. According to the separation and recovery method, the valuable metal lithium and cobalt can be recovered from the waste positive pole piece to the greatest extent in an integrated step, and the use of high-energy-consumption and high-content strong acid and alkali agents can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling and utilization of lithium-ion batteries, in particular to the recycling of positive electrode materials, and more particularly to a method for separating and recovering lithium and cobalt in lithium cobalt oxide positive electrode sheets, and applications thereof. Background Art

[0002] Lithium cobalt oxide is the earliest commercially used cathode material for lithium-ion batteries. It has the characteristics of high energy density and good safety and is widely used in mobile electronic devices such as mobile phones, laptops, cameras, etc. Waste lithium cobalt oxide secondary batteries have become the main type of waste lithium-ion batteries, which contain a large amount of cobalt resources. Therefore, waste lithium cobalt oxide secondary batteries have been studied earlier, and their recycling methods are also applicable to the recycling of waste ternary, lithium manganese oxide and other types of lithium batteries.

[0003] At present, the research on the recycling of waste lithium cobalt oxide secondary batteries mainly focuses on the recovery of valuable metals such as cobalt and lithium with high value and large content. The main recovery methods are wet process and pyrometallurgical process. The wet process has become the mainstream recovery solution due to its mild conditions and low energy consumption. It mainly includes pretreatment, leaching, recovery and other links.

[0004] Pretreatment is mainly to selectively separate higher-value cathode materials, remove lower-value components or organic solvents, and reduce the adverse effects of subsequent cobalt and lithium metal leaching processes. The main methods include discharge, crushing, dissolution, pyrolysis, etc. Leaching is mainly the process of selectively extracting and recovering cobalt and lithium from the cathode materials obtained by pretreatment. The main methods include wet leaching, microbial leaching, water leaching, etc. Recovery is the process of recovering cobalt, lithium and other ions from the leachate using extraction, precipitation, electrochemical and other methods. Among them, the leaching process is a key step in the recovery of waste lithium cobalt oxide secondary batteries. The leaching rate directly affects the subsequent recovery rate. Although the current leaching process is very mature, there are still many problems.

[0005] For example, the purpose of wet leaching is to transfer the valuable metals in the positive electrode material to the leachate, which is beneficial to the subsequent precipitation and purification process. The wet leaching of waste lithium-ion battery positive electrode materials is mainly acid leaching. At the same time, because trivalent cobalt compounds are not easy to dissolve and leach, inorganic acid (sulfuric acid, hydrochloric acid or nitric acid) + hydrogen peroxide is used as the most common leaching system. The combination of inorganic acid + hydrogen peroxide can leach positive electrode materials well, but inorganic acids are highly corrosive, have high requirements for equipment, and are prone to produce harmful gases.

[0006] Microbial leaching utilizes the complexation, reduction, oxidation, and leaching of certain specific microorganisms and metabolites to achieve the purpose of recovering and dissolving valuable metals. Although microbial leaching has advantages such as environmental friendliness, low cost, and low acid consumption, it also has shortcomings such as long cycle, difficulty in strain cultivation, and low efficiency. The valuable metal content in waste lithium cobalt oxide secondary batteries is relatively high, and the microbial leaching cycle is even longer.

[0007] Water leaching is to convert the cathode material obtained by pretreatment into lithium carbonate components by reduction roasting, and then recover lithium by water leaching / carbonation water leaching. Water leaching of lithium elements in waste materials has the characteristics of high efficiency and easy product processing, but most of them need roasting treatment, which still has the disadvantages of slightly high energy consumption and easy pollution.

[0008] Therefore, the above-mentioned leaching process has environmental problems, long cycle, high energy consumption and other problems, and further post-processing is required after leaching, and the recovery cost is high. Summary of the invention

[0009] Based on the above problems, the purpose of the present invention is to provide a method for separating and recovering lithium and cobalt in lithium cobalt oxide positive electrode sheets, and its application. This separation and recovery method can maximize the recovery of valuable metal lithium and cobalt from waste positive electrode sheets in a single integrated step, and can avoid high energy consumption and the use of high-content strong acid and alkaline agents.

[0010] To achieve the above object, the present invention provides a method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet, comprising:

[0011] (1) Preparation

[0012] Dismantle waste batteries to obtain lithium cobalt oxide positive electrode sheets;

[0013] (2) Electrolytic leaching-extraction integration

[0014] The lithium cobalt oxide positive electrode sheet is used as the cathode of the electrolysis system, the platinum metal electrode is used as the anode of the electrolysis system, and the extractant-sulfuric acid mixed solution is used as the electrolyte for electrolysis to obtain an aqueous phase and an organic phase, the extractant-sulfuric acid mixed solution includes dilute sulfuric acid and a composite extractant, the composite extractant includes 2-ethylhexyl phosphate-2-ethylhexyl ester and bis(2,4,4-trimethylpentyl)phosphonic acid, and the volume ratio of the organic phase to the aqueous phase in the extractant-sulfuric acid mixed solution is 1:1-3;

[0015] (3) Recycling

[0016] The aqueous phase is recovered to obtain a Li2SO4 solution, and the organic phase is stripped to obtain a cobalt-containing solution.

[0017] In the technical solution adopted by the present invention, electrolysis and extraction are integrated into one, and valuable metals lithium and cobalt can be recovered from waste positive electrode plates to the maximum extent through a single integrated step. The electrolyte uses an aqueous phase of sulfuric acid and an organic phase of an extractant to mix for proton exchange, which can promote the reaction and greatly improve the metal leaching efficiency. Specifically, during electrolysis, the platinum metal electrode serving as the anode loses electrons when powered on, which is manifested as water decomposing into oxygen to produce an oxygen evolution reaction. The lithium cobalt oxide plate serving as the cathode gains electrons, and the trivalent Co(III) is reduced to divalent Co(II) and enters the electrolyte. The Li in the plate + Also released, Li + and Co 2+ released into the water phase, consuming protons (H + ). With the 2+ As the concentration increases and the pH of the solution rises, the organic phase extractant begins to extract Co from the aqueous solution. 2+ ,Co 2+ Enter the organic phase to separate from Li+. 2+ will continue to enter the organic phase, thus ensuring that Co 2+ The synergistic effect between electrolytic leaching and solvent extraction significantly reduces the consumption of sulfuric acid and increases the proton (H + ) utilization efficiency, which can avoid high energy consumption and the large-scale use of strong acid and alkaline agents.

[0018] In addition, 2-ethylhexyl phosphate-2-ethylhexyl ester (P507) and bis(2,4,4-trimethylpentyl)phosphonic acid (C272) in a volume ratio of 1 to 5:1 were used as composite extractants. Since the extraction reaction of 2-ethylhexyl phosphate-2-ethylhexyl ester would release H + , bis(2,4,4-trimethylpentyl)phosphonic acid can accelerate the extraction reaction, thus achieving the self-saponification of the extractant P507 / C272 (generally speaking, the extractant needs to be fully mixed with alkaline compounds (sodium hydroxide and ammonia) and saponified before the extraction process can be carried out), avoiding the use of alkali solution and the corresponding post-treatment operations, and reducing the input of materials. And the released H + Can enter the water phase and replenish the H consumed by the lithium cobalt oxide cathode leaching + .

[0019] As a technical solution of the present invention, the lithium cobalt oxide positive electrode sheet comprises a positive electrode active material, a binder and a conductive agent, wherein the chemical formula of the positive electrode active material is Li a Co b M (1-b)O2, wherein M is at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0.95≤a≤1.05, 0.95≤b≤1.00, the binder includes PVDF, and the conductive agent includes at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotube and graphene.

[0020] As a technical solution of the present invention, the concentration of the dilute sulfuric acid is 0.01-0.05 mol / L.

[0021] As a technical solution of the present invention, the volume ratio of the 2-ethylhexyl phosphate-2-ethylhexyl ester to the bis(2,4,4-trimethylpentyl)phosphonic acid is 1 to 5:1.

[0022] As a technical solution of the present invention, there may be multiple cathodes and multiple anodes, and multiple electrodes may be connected in parallel.

[0023] As a technical solution of the present invention, the operating voltage of the electrolysis is 2 to 5V.

[0024] As a technical solution of the present invention, the electrolysis temperature is 40-60°C.

[0025] As a technical solution of the present invention, the electrolysis system further comprises a stirring device for stirring the extractant-sulfuric acid mixed solution, and the rotation speed of the stirring device is 300 to 600 rpm / min.

[0026] As a technical solution of the present invention, the solution used for the back extraction is sulfuric acid, and the concentration of the sulfuric acid is 1.5 to 4.0 mol / L.

[0027] On the other hand, the present invention provides a method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet and applying the method to a lithium cobalt oxide secondary battery, wherein the recovery rate of lithium is ≥97.5% and the recovery rate of cobalt is ≥94.0%. DETAILED DESCRIPTION

[0028] The invention provides a method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet, which can realize the separation and purification of Li and Co.

[0029] The lithium cobalt oxide positive electrode sheet of the present invention refers to a positive electrode sheet containing a lithium cobalt oxide positive electrode active material. The lithium cobalt oxide positive electrode sheet includes a positive electrode active material, a binder and a conductive agent. The positive electrode active material includes a lithium cobalt oxide positive electrode active material, and its chemical formula is Li a Co b M (1-b)O2, wherein M is at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0.95≤a≤1.05, 0.95≤b≤1.00. The binder includes PVDF. The conductive agent includes at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes and graphene. The mass ratio of the positive electrode active material, the binder and the conductive agent can be, but is not limited to, 85 to 98:0.5 to 3.0:0.5 to 3.0. The positive electrode sheet can be obtained by using a solvent to make a slurry of the positive electrode active material, the binder and the conductive agent and coating the slurry on the positive electrode current collector, drying, rolling, etc.

[0030] The method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet of the present invention comprises the following steps.

[0031] (1) Preparation

[0032] Disassemble the waste batteries to obtain lithium cobalt oxide positive electrode sheets.

[0033] (2) Electrolytic leaching-extraction integration

[0034] A lithium cobalt oxide positive electrode sheet is used as the cathode of the electrolysis system, a platinum metal electrode is used as the anode of the electrolysis system, and an extractant-sulfuric acid mixed solution is used as the electrolyte for electrolysis to obtain an aqueous phase and an organic phase.

[0035] (3) Recycling

[0036] The aqueous phase is recovered to obtain a Li2SO4 solution, and the organic phase is stripped to obtain a cobalt-containing solution.

[0037] Among them, if the lithium cobalt oxide positive electrode sheet obtained from dismantling waste batteries is large in size, it can be cut into a suitable size and then used as a cathode for electrolysis.

[0038] The extractant-sulfuric acid mixed solution includes dilute sulfuric acid and a composite extractant. The composite extractant includes 2-ethylhexyl phosphate-2-ethylhexyl ester (P507) and bis(2,4,4-trimethylpentyl)phosphonic acid (C272). The volume ratio of 2-ethylhexyl phosphate-2-ethylhexyl ester (P507) and bis(2,4,4-trimethylpentyl)phosphonic acid (C272) is 1 to 5:1, and as an example, it can be but not limited to 1:1, 2:1, 3:1, 4:1, 5:1. P507 and C272 are controlled to a certain volume ratio to release sufficient H +, reduce the amount of dilute sulfuric acid used. The volume ratio of the organic phase to the aqueous phase in the extractant-sulfuric acid mixed solution is 1:1-3. As an example, the volume ratio can be but not limited to 1:1, 1:2, 1:3. The concentration of dilute sulfuric acid is 0.01-0.05 mol / L. As an example, the concentration can be but not limited to 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L. The use of low-concentration dilute sulfuric acid can avoid the negative effects caused by the large-scale use of strong acid reagents.

[0039] The cathode and the anode may be multiple, and multiple electrodes may be connected in parallel to improve the recovery efficiency of the system. The operating voltage of the electrolysis is 2 to 5 V. The temperature of the electrolysis is 40 to 60°C. As an example, the temperature may be, but is not limited to, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C, and 60°C. The temperature is 40 to 60°C to prevent the effect of excessive reaction temperature on the extraction of the organic phase. The electrolysis system also includes a stirring device for stirring the extractant-sulfuric acid mixed solution. The speed of the stirring device is 300 to 600 rpm / min. As an example, the speed may be, but is not limited to, 300 rpm / min, 350 rpm / min, 400 rpm / min, 450 rpm / min, 500 rpm / min, 550 rpm / min, and 600 rpm / min. Stirring the extractant-sulfuric acid mixed solution while electrolyzing can make the reaction sufficient and avoid excessive temperature.

[0040] The solution used for back extraction is sulfuric acid, and the concentration of sulfuric acid is 1.5-4.0 mol / L. As an example, the concentration can be but not limited to 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L.

[0041] In order to better illustrate the purpose, technical scheme and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the following implementation method is a further explanation of the present invention and should not be used as a limitation of the present invention.

[0042] Example 1

[0043] This embodiment is a method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet, and the steps are as follows.

[0044] (1) Preparation

[0045] Dismantle waste 1# lithium cobalt oxide secondary batteries to obtain lithium cobalt oxide positive electrode sheets.

[0046] (2) Electrolytic leaching-extraction integration

[0047] The lithium cobalt oxide positive electrode sheet was cut into 3 suitable sizes as the cathode of the electrolysis system, and 3 lithium cobalt oxide positive electrode sheets were connected in parallel. Three platinum metal electrodes were connected in parallel as the anode of the electrolysis system. The extractant-sulfuric acid mixed solution was used as the electrolyte for electrolysis to obtain an aqueous phase and an organic phase. The volume ratio of the organic phase to the aqueous phase in the extractant-sulfuric acid mixed solution was 1:3, and the extractant-sulfuric acid mixed solution included dilute sulfuric acid and a composite extractant. The concentration of dilute sulfuric acid was 0.02 mol / L, and the composite extractant was 2-ethylhexyl phosphate-2-ethylhexyl ester and di(2,4,4-trimethylpentyl)phosphonic acid in a volume ratio of 3:1. The operating voltage of the electrolysis was 3-4 V, the temperature was 50±2°C, and the extractant-sulfuric acid mixed solution was stirred by a stirring device during electrolysis, and the stirring speed was 450 rpm / min.

[0048] (3) Recycling

[0049] The aqueous phase is recovered to obtain Li2SO4 solution, and the organic phase is stripped with 2.0 mol / L sulfuric acid to obtain CoSO4 solution. The recovery rates of lithium and cobalt are calculated to be 98.9% and 95.8% respectively, indicating that the recovery rates of lithium and cobalt obtained by the recovery method of the present invention are relatively high.

[0050] Example 2

[0051] This embodiment is a method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet, and the steps are as follows.

[0052] (1) Preparation

[0053] Dismantle waste 2# lithium cobalt oxide secondary batteries to obtain lithium cobalt oxide positive electrode sheets.

[0054] (2) Electrolytic leaching-extraction integration

[0055] The lithium cobalt oxide positive electrode sheet was cut into two suitable sizes as the cathode of the electrolysis system, and two lithium cobalt oxide positive electrode sheets were connected in parallel. Two platinum metal electrodes were connected in parallel as the anode of the electrolysis system. The extractant-sulfuric acid mixed solution was used as the electrolyte for electrolysis to obtain an aqueous phase and an organic phase. The volume ratio of the organic phase to the aqueous phase in the extractant-sulfuric acid mixed solution was 1:2, and the extractant-sulfuric acid mixed solution included dilute sulfuric acid and a composite extractant. The concentration of dilute sulfuric acid was 0.05 mol / L, and the composite extractant was 2-ethylhexyl phosphate-2-ethylhexyl ester and di(2,4,4-trimethylpentyl)phosphonic acid in a volume ratio of 5:1. The operating voltage of the electrolysis was 3-4 V, the temperature was 55±2°C, and the extractant-sulfuric acid mixed solution was stirred by a stirring device during electrolysis, and the stirring speed was 300 rpm / min.

[0056] (3) Recycling

[0057] The aqueous phase is recovered to obtain Li2SO4 solution, and the organic phase is stripped with 3.5 mol / L sulfuric acid to obtain CoSO4 solution. The recovery rates of lithium and cobalt are calculated to be 98.4% and 95.1%, respectively, indicating that the recovery rates of lithium and cobalt obtained by the recovery method of the present invention are relatively high.

[0058] Example 3

[0059] This embodiment is a method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet, and the steps are as follows.

[0060] (1) Preparation

[0061] Dismantle waste 3# lithium cobalt oxide secondary batteries to obtain lithium cobalt oxide positive electrode sheets.

[0062] (2) Electrolytic leaching-extraction integration

[0063] The lithium cobalt oxide positive electrode sheet is used as the cathode of the electrolysis system, and the platinum metal electrode is used as the anode of the electrolysis system. The extractant-sulfuric acid mixed solution is used as the electrolyte for electrolysis to obtain an aqueous phase and an organic phase. The volume ratio of the organic phase to the aqueous phase in the extractant-sulfuric acid mixed solution is 1:1, and the extractant-sulfuric acid mixed solution includes dilute sulfuric acid and a composite extractant. The concentration of dilute sulfuric acid is 0.05 mol / L, and the composite extractant is 2-ethylhexyl phosphate-2-ethylhexyl ester and di(2,4,4-trimethylpentyl)phosphonic acid in a volume ratio of 4:1. The operating voltage of the electrolysis is 2.5-4.0 V, the temperature is 45±2°C, and the extractant-sulfuric acid mixed solution is stirred by a stirring device during electrolysis, and the stirring speed is 550 rpm / min.

[0064] (3) Recycling

[0065] The aqueous phase is recovered to obtain Li2SO4 solution, and the organic phase is stripped with 2.5 mol / L sulfuric acid to obtain CoSO4 solution. The recovery rates of lithium and cobalt are calculated to be 97.9% and 94.1%, respectively, indicating that the recovery rates of lithium and cobalt obtained by the recovery method of the present invention are relatively high.

[0066] Comparative Example 1

[0067] This comparative example is a method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet, and the steps are as follows.

[0068] (1) Preparation

[0069] Dismantle waste 1# lithium cobalt oxide secondary batteries to obtain lithium cobalt oxide positive electrode sheets.

[0070] (2) Electrolytic leaching

[0071] The lithium cobalt oxide positive electrode sheet was cut into 3 suitable sizes as the cathode of the electrolysis system, and the 3 lithium cobalt oxide positive electrode sheets were connected in parallel. 3 platinum metal electrodes were connected in parallel as the anode of the electrolysis system. The electrolysis was carried out using sulfuric acid with a concentration of 1.0 mol / L as the electrolyte, the operating voltage of the electrolysis was 3-4 V, the temperature was 50±2°C, and the electrolyte was stirred with a stirring device during the electrolysis, and the stirring speed was 450 rpm / min.

[0072] (3) Extraction

[0073] 2-Ethylhexyl phosphate-2-ethylhexyl ester and bis(2,4,4-trimethylpentyl)phosphonic acid in a volume ratio of 3:1 were used as a composite extractant, and 0.5 mol / L sodium hydroxide solution was stirred at 1000 rpm for 45 min, followed by oil-water phase separation to obtain a saponified extractant, which was then used to extract the electrolyte to obtain an aqueous phase and an organic phase.

[0074] (4) Recycling

[0075] The aqueous phase was recovered to obtain Li2SO4 solution, and the organic phase was stripped with 2.0 mol / L sulfuric acid to obtain CoSO4 solution. The recovery rates of lithium and cobalt were calculated to be 88.5% and 86.7% respectively.

[0076] Comparative Example 2

[0077] This comparative example is a method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet, and the steps are as follows.

[0078] (1) Preparation

[0079] Dismantle waste 1# lithium cobalt oxide secondary batteries to obtain lithium cobalt oxide positive electrode sheets.

[0080] (2) Electrolytic leaching-extraction integration

[0081] The lithium cobalt oxide positive electrode sheet was cut into 3 suitable sizes as the cathode of the electrolysis system, and 3 lithium cobalt oxide positive electrode sheets were connected in parallel. Three platinum metal electrodes were connected in parallel as the anode of the electrolysis system. The extractant-sulfuric acid mixed solution was used as the electrolyte for electrolysis to obtain an aqueous phase and an organic phase. The volume ratio of the organic phase to the aqueous phase in the extractant-sulfuric acid mixed solution was 1:3, and the extractant-sulfuric acid mixed solution included dilute sulfuric acid and an extractant. The concentration of dilute sulfuric acid was 0.02 mol / L, and the extractant was 2-ethylhexyl phosphate-2-ethylhexyl ester. The operating voltage of the electrolysis was 3-4 V, the temperature was 50±2°C, and the extractant-sulfuric acid mixed solution was stirred by a stirring device during electrolysis, and the stirring speed was 450 rpm / min.

[0082] (3) The aqueous phase is recovered to obtain Li2SO4 solution, and the organic phase is stripped with 2.0 mol / L sulfuric acid to obtain CoSO4 solution. The recovery rates of lithium and cobalt are calculated to be 92.7% and 89.5%, respectively.

[0083] Comparative Example 3

[0084] This comparative example is a method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet, and the steps are as follows.

[0085] (1) Preparation

[0086] Dismantle waste 1# lithium cobalt oxide secondary batteries to obtain lithium cobalt oxide positive electrode sheets.

[0087] (2) Electrolytic leaching-extraction integration

[0088] The lithium cobalt oxide positive electrode sheet was cut into 3 suitable sizes as the cathode of the electrolysis system, and 3 lithium cobalt oxide positive electrode sheets were connected in parallel. Three platinum metal electrodes were connected in parallel as the anode of the electrolysis system. The extractant-sulfuric acid mixed solution was used as the electrolyte for electrolysis to obtain an aqueous phase and an organic phase. The volume ratio of the organic phase to the aqueous phase in the extractant-sulfuric acid mixed solution was 1:3, and the extractant-sulfuric acid mixed solution included sulfuric acid and an extractant. The concentration of sulfuric acid was 1.0 mol / L, and the extractant was di(2,4,4-trimethylpentyl)phosphonic acid. The operating voltage of the electrolysis was 3-4 V, and the temperature was 50±2°C. During the electrolysis, the extractant-sulfuric acid mixed solution was stirred with a stirring device at a stirring speed of 450 rpm / min.

[0089] (3) The aqueous phase is recovered to obtain Li2SO4 solution, and the organic phase is stripped with 2.0 mol / L sulfuric acid to obtain CoSO4 solution. The recovery rates of lithium and cobalt are calculated to be 94.8% and 90.3%, respectively.

[0090] From the comparison between Examples 1 to 3 and Comparative Examples 1 to 3, it can be seen that the recovery method of the present invention can recover high content of cobalt and lithium. However, if the electrolytic leaching and extraction are performed in separate steps, the extractant cannot release H into the electrolyte. + , a higher content of sulfuric acid is required, and an alkali is also required to achieve saponification of the extractant. In Comparative Example 2, a single 2-ethylhexyl phosphate-2-ethylhexyl ester is used as the extractant. Although the system can still spontaneously generate H + , but lacks the synergistic effect of bis(2,4,4-trimethylpentyl)phosphonic acid, so the extraction rate will slow down, which is ultimately reflected in the decrease of overall extraction efficiency. In Comparative Example 3, a single bis(2,4,4-trimethylpentyl)phosphonic acid is used as the extractant, which cannot spontaneously generate H + Not only does the recovery rate decrease, but the content of dilute sulfuric acid required for electrolytic leaching needs to be increased, otherwise it is difficult to fully leach lithium cobalt oxide.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for separating and recovering lithium and cobalt from a lithium cobalt oxide positive electrode sheet, characterized in that: include: (1) Preparation Dismantle the waste batteries to obtain lithium cobalt oxide positive electrode sheets; (2) Electrolytic leaching-extraction integration The lithium cobalt oxide positive electrode sheet is used as the cathode of the electrolysis system, the platinum metal electrode is used as the anode of the electrolysis system, and the extractant-sulfuric acid mixed solution is used as the electrolyte for electrolysis to obtain an aqueous phase and an organic phase, the extractant-sulfuric acid mixed solution includes dilute sulfuric acid and a composite extractant, the composite extractant includes 2-ethylhexyl phosphate-2-ethylhexyl ester and bis(2,4,4-trimethylpentyl)phosphonic acid, and the volume ratio of the organic phase to the aqueous phase in the extractant-sulfuric acid mixed solution is 1:1-3; (3) Recycling The aqueous phase is recovered to obtain a Li2SO4 solution, and the organic phase is stripped to obtain a cobalt-containing solution.

2. The method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The lithium cobalt oxide positive electrode sheet comprises a positive electrode active material, a binder and a conductive agent. The chemical formula of the positive electrode active material is Li a Co b M (1-b) O2, wherein M is at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0.95≤a≤1.05, 0.95≤b≤1.00, the binder includes PVDF, and the conductive agent includes at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotube and graphene.

3. The method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The concentration of the dilute sulfuric acid is 0.01-0.05 mol / L.

4. The method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The volume ratio of the 2-ethylhexyl phosphate-2-ethylhexyl ester to the bis(2,4,4-trimethylpentyl)phosphonic acid is 1 to 5:

1.

5. The method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: There may be a plurality of cathodes and anodes, and multiple electrodes may be connected in parallel.

6. The method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The operating voltage of the electrolysis is 2-5V.

7. The method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The electrolysis temperature is 40-60°C.

8. The method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The electrolysis system further comprises a stirring device for stirring the extractant-sulfuric acid mixed solution, and the rotation speed of the stirring device is 300-600 rpm / min.

9. The method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet according to claim 1, characterized in that: The solution used for the back extraction is sulfuric acid, and the concentration of the sulfuric acid is 1.5-4.0 mol / L.

10. Use of the method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet according to any one of claims 1 to 9 in a lithium cobalt oxide secondary battery, characterized in that: The recovery rate of lithium is ≥97.5%, and the recovery rate of cobalt is ≥94.0%.