Method for separating and recovering lithium and cobalt in lithium cobalt oxide-based positive electrode sheet and application thereof

Abstract

The application provides a lithium cobalt separation and recovery method for a lithium cobalt oxide positive electrode sheet and an application. The lithium cobalt separation and recovery method for the lithium cobalt oxide positive electrode sheet comprises the following steps: disassembling waste batteries to obtain lithium cobalt oxide positive electrode sheets; taking the lithium cobalt oxide positive electrode sheets as cathodes of an electrolysis system, taking platinum metal electrodes as anodes of the electrolysis system, and electrolyzing the lithium cobalt oxide positive electrode sheets in an extractant-sulfuric acid mixed solution as an electrolyte to obtain an aqueous phase and an organic phase, wherein the extractant-sulfuric acid mixed solution comprises dilute sulfuric acid and a composite extractant, the composite extractant comprises 2-ethylhexyl phosphoric acid-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; recycling the aqueous phase to obtain a Li2SO4 solution, and back-extracting the organic phase to obtain a cobalt-containing solution. The separation and recovery method can maximize the recovery of valuable metals lithium and cobalt from waste positive electrode sheets in one integrated step, and can avoid the use of high-energy consumption and high-content strong acid and alkaline reagents.

Description

TECHNICAL FIELD

[0001] The present application relates to the recycling and utilization technical field of lithium ion batteries, in particular to the recycling and utilization of positive electrode materials, and more particularly to a lithium cobalt oxide-based positive electrode sheet lithium cobalt separation and recycling method and application. BACKGROUND

[0002] Lithium cobalt oxide is the earliest commercialized positive electrode material of lithium ion batteries, has the characteristics of high energy density and good safety, and is widely used in mobile electronic devices such as mobile phones, notebook computers, 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 early, and their recycling methods are also suitable for the recycling of waste ternary, lithium manganate, etc. lithium batteries.

[0003] At present, the recycling research of waste lithium cobalt oxide secondary batteries mainly recovers valuable metals such as cobalt and lithium with high content, and the main recycling methods include wet process and pyrometallurgical process. Wet process has become the mainstream recycling scheme due to its mild conditions and low energy consumption, which mainly includes pretreatment, leaching, and recovery.

[0004] Pretreatment mainly selectively separates high-value positive electrode materials, removes slightly lower value components or organic solvents, and reduces the adverse effects of subsequent cobalt and lithium metal leaching processes. The main methods include discharge, crushing, dissolution, and pyrolysis. Leaching is mainly the process of selectively extracting and recovering cobalt and lithium from the positive electrode materials obtained by pretreatment, mainly including wet leaching, microbial leaching, and water leaching. Recovery is the process of recovering cobalt, lithium, and other ions from the leaching solution by extraction, precipitation, and electrochemistry. Among them, the leaching process is the key step in the recycling of waste lithium cobalt oxide secondary batteries, and its 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 valuable metals in the positive electrode material to the leaching solution, which is beneficial to the subsequent precipitation and purification process. Wet leaching of waste lithium ion battery positive electrode materials is mainly an acid leaching scheme. At the same time, due to the difficulty of dissolving and leaching trivalent cobalt compounds, inorganic acid (sulfuric acid, hydrochloric acid, or nitric acid) + hydrogen peroxide is the most common leaching system. The combination of inorganic acid + hydrogen peroxide can better leach the positive electrode material, but inorganic acid has strong corrosion and high equipment requirements, and is easy to produce harmful gases.

[0006] Microbial leaching is to realize the purpose of valuable metal recovery and dissolution by using the complexation, reduction, oxidation, leaching and other effects of certain specific microorganisms and metabolic products. Although microbial leaching has the advantages of environmental friendliness, low cost, and low acid consumption, it also has the disadvantages of long cycle, difficulty in strain cultivation, and low efficiency. The valuable metal content in waste lithium cobalt oxide batteries is relatively high, and the microbial leaching cycle is longer.

[0007] Water leaching is to convert the positive electrode material obtained by pretreatment into lithium carbonate component 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 processing of products, but most of them need to be roasted. This link still has the disadvantages of slightly high energy consumption and easy pollution.

[0008] Therefore, the above leaching process has problems of environmental protection, long cycle, high energy consumption, etc., and further post-treatment is required after leaching, and the recovery cost is high. SUMMARY

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

[0010] To achieve the above purpose, one aspect of the present application provides a lithium cobalt separation and recovery method in lithium cobalt oxide positive electrode sheet, comprising:

[0011] (1) Preparation of materials

[0012] The waste battery is disassembled to obtain a lithium cobalt oxide positive electrode sheet;

[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 to carry out electrolysis to obtain an aqueous phase and an organic phase. The extractant-sulfuric acid mixed solution comprises dilute sulfuric acid and a composite extractant, the composite extractant comprises 2-ethylhexyl phosphoric acid-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) Recovery

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

[0017] The technical scheme of the present application integrates electrolysis and extraction into one, and through one single integrated step, valuable metals lithium and cobalt can be recovered from waste positive electrode sheet to the maximum extent. The mixture of water phase of sulfuric acid and organic phase of extractant is used to promote the reaction, and the leaching efficiency of the metal is greatly improved. Specifically, in the electrolysis, the platinum metal electrode as the anode loses electrons under the condition of power supply, and the oxygen evolution reaction occurs. The lithium cobalt oxide sheet as the cathode obtains electrons, and the trivalent Co(III) is reduced to the divalent Co(II) and enters the electrolyte. The Li + in the sheet is released, and the Li + and Co 2+ are released into the water phase, and the protons (H + ) of the water phase are consumed. With the increase of the Co 2+ concentration and the increase of the solution pH, the organic phase extractant begins to extract Co 2+ from the water solution, and the Co 2+ enters the organic phase to realize the separation from the Li+. Since the Co 2+ of the water phase enters the organic phase, the low concentration of Co 2+ in the water phase is ensured, so that the electrolysis reaction continuously proceeds, and the high-efficiency leaching of the lithium cobalt oxide is realized. The synergistic effect between the electrolytic leaching and the solvent extraction significantly reduces the consumption of sulfuric acid, improves the utilization efficiency of the protons (H + ), and avoids the use of high energy consumption and large amount of strong acid and alkali reagents.

[0018] In addition, 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (P507) and bis(2,4,4-trimethylpentyl) phosphonic acid (C272) with a volume ratio of 1-5:1 are used as the composite extractant. Since the extraction reaction of 2-ethylhexyl phosphoric acid-2-ethylhexyl ester releases H + , and bis(2,4,4-trimethylpentyl) phosphonic acid can accelerate the extraction reaction, the self-saponification of the extractant P507 / C272 can be realized (generally, the extractant needs to be mixed with an alkali compound (sodium hydroxide and ammonia) and saponified before extraction), the use of lye and the corresponding post-processing operation are avoided, and the material input is reduced. The released H + can enter the water phase to replenish the H + consumed by the cathode leaching of the lithium cobalt oxide.

[0019] As a technical scheme of the present application, the lithium cobalt oxide positive electrode sheet comprises a positive electrode active material, a binder and a conductive agent, and 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 comprises PVDF, and the conductive agent comprises at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotube and graphene.

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

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

[0022] As a technical scheme of the present application, the cathode and the anode can be multiple and connected in parallel.

[0023] As a technical scheme of the present application, the operating voltage of the electrolysis is 2-5 V.

[0024] As a technical scheme of the present application, the temperature of the electrolysis is 40-60 DEG C.

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

[0026] As a technical scheme of the present application, the solution used in the back extraction is sulfuric acid, and the concentration of the sulfuric acid is 1.5-4.0 mol / L.

[0027] The application further provides a method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet and application of the method in a lithium cobalt oxide secondary battery, wherein the recovery rate of lithium is greater than or equal to 97.5%, and the recovery rate of cobalt is greater than or equal to 94.0%. DETAILED DESCRIPTION

[0028] The application provides a method for separating and recovering lithium and cobalt in a lithium cobalt oxide positive electrode sheet, which can separate and purify Li and Co.

[0029] The lithium cobalt oxide positive electrode sheet of the application refers to a positive electrode sheet containing a lithium cobalt oxide positive electrode active material. 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 nanotube and graphene. The mass ratio of the positive electrode active material, the binder and the conductive agent can be, but is not limited to, 85-98:0.5-3.0:0.5-3.0. The positive electrode sheet can be prepared by preparing a slurry of the positive electrode active material, the binder and the conductive agent with a solvent and coating the slurry on a positive electrode current collector and drying, rolling, etc.

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

[0031] (1) Preparation

[0032] The lithium cobalt oxide positive electrode sheet is obtained by disassembling the waste battery.

[0033] (2) Electrolytic leaching-extraction integration

[0034] 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 to perform electrolysis to obtain the aqueous phase and the organic phase.

[0035] (3) Recovery

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

[0037] Among them, if the lithium cobalt oxide positive electrode sheet obtained by disassembling the waste battery is relatively large in size, it can be cut into a suitable size before being used as the cathode for electrolysis.

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

[0039] The cathode and the anode can be multiple and connected in parallel to improve the recovery efficiency of the system, and the operating voltage of electrolysis is 2-5 V. The temperature of electrolysis is 40-60°C, and as an example, the temperature can 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, 60°C, and the temperature of 40-60°C can prevent the influence of high reaction temperature on the extraction organic phase. The electrolysis system further comprises a stirring device for stirring the mixed solution of the extractant and sulfuric acid, and the stirring speed of the stirring device is 300-600 rpm / min, and as an example, the stirring speed can be but is not limited to 300 rpm / min, 350 rpm / min, 400 rpm / min, 450 rpm / min, 500 rpm / min, 550 rpm / min, 600 rpm / min, and the mixed solution of the extractant and sulfuric acid is stirred at the same time of electrolysis, so that the reaction is sufficient and the temperature is prevented from being too high.

[0040] The solution used in the back extraction is sulfuric acid, and the concentration of the sulfuric acid is 1.5-4.0 mol / L, and as an example, the concentration can be but is 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 application, the present application will be further described below in combination with specific examples. It should be noted that the following implementation of the method is a further explanation and description of the present application, and should not be regarded as a limitation of the present application.

[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 of materials

[0045] The lithium cobalt oxide positive electrode sheet is obtained by disassembling the waste 1# lithium cobalt oxide secondary battery.

[0046] (2) Electrolytic leaching-extraction integration

[0047] Cutting the lithium cobalt oxide positive electrode sheet into three appropriate sizes as cathode of electrolysis system, and connecting the three lithium cobalt oxide positive electrode sheets in parallel. Connecting the three platinum metal electrodes in parallel as anode of electrolysis system. Using the extractant-sulfuric acid mixed solution as electrolyte to carry out electrolysis to obtain water phase and organic phase. The volume ratio of organic phase to water phase in the extractant-sulfuric acid mixed solution is 1:3, and the extractant-sulfuric acid mixed solution comprises dilute sulfuric acid and composite extractant. The concentration of dilute sulfuric acid is 0.02 mol / L, and the composite extractant is 2-ethylhexyl phosphoric acid-2-ethylhexyl ester and bis(2,4,4-trimethylpentyl) phosphonic acid with a volume ratio of 3:1. The running voltage of electrolysis is 3-4 V, and the temperature is 50±2 ℃. The extractant-sulfuric acid mixed solution is stirred by a stirring device during electrolysis, and the stirring speed is 450 rpm / min.

[0048] (3) Recovery

[0049] The water phase is recovered to obtain Li2SO4 solution, and the organic phase is stripped by using sulfuric acid with a concentration of 2.0 mol / L 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 application are relatively high.

[0050] Example 2

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

[0052] (1) Preparation

[0053] The waste 2# lithium cobalt oxide secondary battery is disassembled to obtain lithium cobalt oxide positive electrode sheet.

[0054] (2) Electrolytic leaching-extraction integration

[0055] Cutting the lithium cobalt oxide positive electrode sheet into two appropriate sizes as cathode of electrolysis system, and connecting the two lithium cobalt oxide positive electrode sheets in parallel. Connecting the two platinum metal electrodes in parallel as anode of electrolysis system. Using the extractant-sulfuric acid mixed solution as electrolyte to carry out electrolysis to obtain water phase and organic phase. The volume ratio of organic phase to water phase in the extractant-sulfuric acid mixed solution is 1:2, and the extractant-sulfuric acid mixed solution comprises dilute sulfuric acid and composite extractant. The concentration of dilute sulfuric acid is 0.05 mol / L, and the composite extractant is 2-ethylhexyl phosphoric acid-2-ethylhexyl ester and bis(2,4,4-trimethylpentyl) phosphonic acid with a volume ratio of 5:1. The running voltage of electrolysis is 3-4 V, and the temperature is 55±2 ℃. The extractant-sulfuric acid mixed solution is stirred by a stirring device during electrolysis, and the stirring speed is 300 rpm / min.

[0056] (3) Recovery

[0057] The water phase is recovered to obtain a Li2SO4 solution, and the organic phase is back-extracted by using sulfuric acid with a concentration of 3.5 mol / L to obtain a 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 using the recovery method are relatively high.

[0058] Example 3

[0059] The present embodiment is a lithium-cobalt separation and recovery method for a lithium cobalt oxide positive electrode sheet, and the steps are as follows.

[0060] (1) Preparation

[0061] The lithium cobalt oxide positive electrode sheet is obtained by disassembling a waste 3# lithium cobalt oxide secondary battery.

[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 electrolyte is an extractant-sulfuric acid mixed solution, and the electrolysis is performed to obtain the water phase and the organic phase. The volume ratio of the organic phase to the water 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 the dilute sulfuric acid is 0.05 mol / L, and the composite extractant is 2-ethylhexyl phosphoric acid-2-ethylhexyl ester and bis(2,4,4-trimethylpentyl) phosphonic acid with a volume ratio of 4:1. The operating voltage of the electrolysis is 2.5-4.0 V, and the temperature is 45±2℃. The extractant-sulfuric acid mixed solution is stirred by using a stirring device during the electrolysis, and the stirring speed is 550 rpm / min.

[0064] (3) Recovery

[0065] The water phase is recovered to obtain a Li2SO4 solution, and the organic phase is back-extracted by using sulfuric acid with a concentration of 2.5 mol / L to obtain a 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 using the recovery method are relatively high.

[0066] Comparative Example 1

[0067] The present comparative example is a lithium-cobalt separation and recovery method for a lithium cobalt oxide positive electrode sheet, and the steps are as follows.

[0068] (1) Preparation

[0069] The lithium cobalt oxide positive electrode sheet is obtained by disassembling a waste 1# lithium cobalt oxide secondary battery.

[0070] (2) Electrolytic leaching

[0071] Cutting the lithium cobalt oxide positive electrode sheet into three appropriate sizes as the cathode of the electrolysis system, and connecting the three lithium cobalt oxide positive electrode sheets in parallel. Connecting three platinum metal electrodes in parallel as the anode of the electrolysis system. Using sulfuric acid with a concentration of 1.0 mol / L as the electrolyte for electrolysis, the running voltage of electrolysis is 3-4 V, the temperature is 50±2℃, and the electrolyte is stirred by a stirring device at a stirring speed of 450 rpm / min while electrolysis is being carried out.

[0072] (3) Extraction

[0073] Using 2-ethylhexyl phosphonic acid-2-ethylhexyl ester and bis(2,4,4-trimethylpentyl) phosphonic acid with a volume ratio of 3:1 as the composite extractant, and stirring 0.5 mol / L sodium hydroxide solution at a stirring speed of 1000 rpm for 45 min, then separating the oil and water phases to obtain the saponified extractant. The extractant is used to extract the electrolyte to obtain the aqueous phase and the organic phase.

[0074] (4) Recovery

[0075] The aqueous phase is recovered to obtain a Li2SO4 solution, and the organic phase is back-extracted using sulfuric acid with a concentration of 2.0 mol / L to obtain a CoSO4 solution. The recovery rates of lithium and cobalt are 88.5% and 86.7%, respectively.

[0076] Comparative Example 2

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

[0078] (1) Preparation of materials

[0079] The lithium cobalt oxide positive electrode sheet is obtained by disassembling a waste 1# lithium cobalt oxide secondary battery.

[0080] (2) Electrolytic leaching-extraction integration

[0081] Cutting the lithium cobalt oxide positive electrode sheet into three appropriate sizes as the cathode of the electrolysis system, and connecting the three lithium cobalt oxide positive electrode sheets in parallel. Connecting three platinum metal electrodes in parallel as the anode of the electrolysis system. Using the extractant-sulfuric acid mixed solution as the electrolyte for electrolysis to obtain the aqueous phase and the organic phase. The volume ratio of the organic phase to the aqueous phase in the extractant-sulfuric acid mixed solution is 1:3, and the extractant-sulfuric acid mixed solution includes dilute sulfuric acid and an extractant. The concentration of the dilute sulfuric acid is 0.02 mol / L, and the extractant is 2-ethylhexyl phosphonic acid-2-ethylhexyl ester. The running voltage of electrolysis is 3-4 V, the temperature is 50±2℃, and the extractant-sulfuric acid mixed solution is stirred by a stirring device at a stirring speed of 450 rpm / min while electrolysis is being carried out.

[0082] (3) The water phase is recovered to obtain a Li2SO4 solution, and the organic phase is back-extracted with 2.0 mol / L sulfuric acid to obtain a 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 lithium cobalt oxide-based positive electrode sheet lithium cobalt separation and recovery method, and the steps are as follows.

[0085] (1) Preparation

[0086] The waste 1# lithium cobalt oxide secondary battery is disassembled to obtain lithium cobalt oxide positive electrode sheets.

[0087] (2) Electrolytic leaching-extraction integration

[0088] The lithium cobalt oxide positive electrode sheets are cut into three appropriate sizes as cathodes of the electrolysis system, and the three lithium cobalt oxide positive electrode sheets are connected in parallel. Three platinum metal electrodes connected in parallel are used as anodes of the electrolysis system. An extractant-sulfuric acid mixed solution is used as an electrolyte to perform electrolysis to obtain a water phase and an organic phase. The volume ratio of the organic phase to the water phase in the extractant-sulfuric acid mixed solution is 1:3, and the extractant-sulfuric acid mixed solution includes sulfuric acid and an extractant. The concentration of sulfuric acid is 1.0 mol / L, and the extractant is bis(2,4,4-trimethylpentyl) phosphonic acid. The operating voltage of electrolysis is 3-4 V, and the temperature is 50±2°C. While electrolysis is being performed, the extractant-sulfuric acid mixed solution is stirred using a stirring device, and the stirring speed is 450 rpm / min.

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

[0090] From the comparison of Examples 1-3 and Comparative Examples 1-3, it can be seen that the recovery method of the present application can recover high content of cobalt and lithium. The electrolytic leaching and extraction are operated in steps, and the extractant cannot release H + in the electrolyte, so a high content of sulfuric acid is required, and an alkali needs to be used to realize the saponification of the extractant. In Comparative Example 2, a single 2-ethylhexyl phosphonic acid-2-ethylhexyl ester is used as the extractant. Although this system can still spontaneously generate H + , but it lacks the synergistic effect of bis(2,4,4-trimethylpentyl) phosphonic acid, so the extraction rate is slowed down, and ultimately the overall extraction efficiency is reduced. 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 is the recovery rate reduced, but the content of dilute sulfuric acid required for electrolytic leaching needs to be increased, otherwise it is difficult to fully leach the lithium cobalt oxide.

[0091] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application, and although the present application has been described in detail with reference to the preferred embodiments, it is not limited to the listed in the embodiments, and those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for separating and recovering lithium and cobalt in a lithium cobalt oxide-based positive electrode sheet, characterized by, The application relates to a method for recycling lithium cobalt oxide positive pole pieces from waste batteries. The method comprises the following steps: (1) preparing materials The waste batteries are disassembled to obtain lithium cobalt oxide positive pole pieces; (2) electrolytic leaching-extraction integration The lithium cobalt oxide positive pole pieces are used as cathodes of an electrolysis system, a platinum metal electrode is used as an anode of the electrolysis system, and an extractant-sulfuric acid mixed solution is used as an electrolyte to perform electrolysis to obtain an aqueous phase and an organic phase, the extractant-sulfuric acid mixed solution comprises dilute sulfuric acid and a composite extractant, the composite extractant comprises 2-ethylhexyl phosphonic acid-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 2. The method of claim 1, wherein the lithium cobalt separation and recovery method is characterized by, The lithium cobalt oxide-based positive electrode sheet includes a positive electrode active material, a binder, and a conductive agent, the positive electrode active material has a chemical formula of 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 of claim 1, wherein the lithium cobalt separation and recovery method is characterized by, The aqueous phase is recycled to obtain a Li2SO4 solution, and the organic phase is subjected to stripping to obtain a cobalt-containing solution.

4. The method of claim 1, wherein the lithium cobalt separation and recovery method of the lithium cobalt oxide-based cathode sheet is characterized by, The concentration of the dilute sulfuric acid is 0.01-0.05 mol / L.

5. The method of claim 1, wherein the lithium cobalt separation and recovery method of the lithium cobalt oxide-based cathode sheet is characterized by, The volume ratio of the 2-ethylhexyl phosphonic acid-2-ethylhexyl ester to the bis (2, 4, 4-trimethylpentyl) phosphonic acid is 1-5:

1.

6. The method of claim 1, wherein the lithium cobalt separation and recovery method of the lithium cobalt oxide-based cathode sheet is characterized by, The cathode and the anode can be multiple and are connected in parallel.

7. The method of claim 1, wherein the lithium cobalt separation and recovery method is characterized by, The operation voltage of the electrolysis is 2-5 V.

8. The method of claim 1, wherein the lithium cobalt separation and recovery method of the lithium cobalt oxide-based cathode sheet is characterized by, The temperature of the electrolysis is 40-60 DEG C.

9. The method of claim 1, wherein the lithium cobalt separation and recovery method of the lithium cobalt oxide-based cathode sheet is characterized by, The electrolysis system further comprises a stirring device for stirring the extractant-sulfuric acid mixed solution, and the rotating speed of the stirring device is 300-600 rpm / min.

10. Use of the lithium cobalt separation and recovery method for the lithium cobalt oxide positive electrode sheet according to any one of claims 1 to 9 in a lithium cobalt oxide secondary battery, characterized by, The solution used for the stripping is sulfuric acid, and the concentration of the sulfuric acid is 1.5-4.0 mol / L. The recovery rate of lithium is greater than or equal to 97.5%, and the recovery rate of cobalt is greater than or equal to 94.0%.