Method for recycling lithium from waste lithium ion battery and repairing lithium iron phosphate material

Abstract

The application discloses a method for recycling lithium from waste lithium ion batteries and repairing lithium phosphate iron material in cooperation, which is characterized in that lithium in the positive material of the waste lithium ion batteries is used as a lithium source, and lithium separated from the waste positive material is embedded into the waste lithium phosphate iron material on the negative side through electric field driving, so that the lithium phosphate iron material is repaired by lithium supplement. The method has three advantages: 1. lithium in the positive material of the waste lithium ion batteries can be selectively separated and effectively recycled; 2. the waste lithium phosphate iron material can be repaired and regenerated by lithium supplement, so that new lithium phosphate iron electrode material is prepared; and 3. useful materials such as iron phosphate, cobalt oxide and manganese oxide can be obtained as by-products after lithium is separated.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for recycling lithium from waste lithium ion batteries and simultaneously repairing regenerated lithium iron phosphate electrode materials, and belongs to the field of lithium ion battery recycling and positive electrode material preparation. BACKGROUND

[0002] With the rapid growth of energy storage demand for consumer electronics, electric vehicles and wind and solar power generation facilities, lithium ion batteries have experienced explosive development. In particular, driven by the development of new energy vehicles, the installed capacity of power batteries has exceeded the consumer electronics market. Therefore, it is of great significance to develop green, efficient and low-carbon processes to recycle and reuse retired lithium ion batteries.

[0003] At present, the mainstream methods for recycling lithium ion batteries include hydrometallurgy and pyrometallurgy. Among them: the hydrometallurgical process usually uses strong acid and strong alkali solution, thereby generating a large amount of wastewater, which is easy to cause secondary pollution and environmental governance problems; the pyrometallurgical process also has problems such as high energy consumption, difficulty in removing metal impurities, and emission of toxic flue gas.

[0004] The existing recycling technology based on hydrometallurgy or pyrometallurgy usually concentrates the lithium-containing solution obtained by evaporation or extraction enrichment, and then adds sodium carbonate or phosphoric acid to form lithium salt precipitate for separation and recovery. In actual process, evaporation concentration will bring huge energy consumption, and the addition of sodium carbonate or phosphoric acid will increase the additional material cost. In addition, the introduction of phosphate and sodium ions will increase the difficulty of separation and purification, resulting in a decrease in lithium recovery rate and a waste of lithium resources. For the above reasons, it is still necessary to develop more green and efficient process technology for the recycling and reuse of lithium resources from waste lithium ion batteries. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provides a method for recycling lithium from waste lithium ion batteries and simultaneously repairing lithium iron phosphate materials, that is, under electrolytic conditions, on the one hand, the lithium ion battery waste positive electrode sheet on the positive side is delithiated, and on the other hand, the delithiated lithium ions are embedded into the waste lithium iron phosphate on the negative side, playing a role in lithium supplementation and repair. This method not only effectively solves the problem of lithium resource recovery of various waste lithium ion battery electrode materials, but also simultaneously recovers and repairs the lithium supplementation of waste lithium iron phosphate electrode materials, thereby solving the following two problems: (1) the problem of non-universality of the recycling process due to the variety and different specifications of waste lithium ion battery positive electrode materials; (2) the problem of complex process and high cost in recycling lithium resources from waste lithium ion batteries.

[0006] To achieve the purpose, the present application adopts the following technical solutions:

[0007] A method for recovering lithium from waste lithium ion batteries and simultaneously repairing lithium iron phosphate material, comprising the following steps:

[0008] Step 1: Discharge and disassemble the retired lithium ion battery to obtain a waste positive electrode sheet, immerse the positive electrode sheet in dimethyl carbonate (DMC) solvent at room temperature, and dissolve and remove the residual electrolyte in the positive electrode sheet; then take out the positive electrode sheet and wash it with deionized water to remove DMC, and obtain a pretreated positive electrode sheet;

[0009] Step 2: Use the pretreated positive electrode sheet obtained in step 1 as the positive electrode, place it in a direct current electrolysis tank, and use a waste lithium iron phosphate positive electrode sheet pretreated by the same method as step 1 as the negative electrode, and use an electrochemical method to electrolyze in a 0.1-2 mol / L lithium salt solution. Lithium ions in the positive electrode sheet are driven by the electric field and enter the solution, and the negative electrode sheet is reduced to obtain a repaired lithium iron phosphate electrode sheet.

[0010] Step 3: Dry the repaired lithium iron phosphate electrode sheet in step 2 in an oven. Since the electrode material and aluminum foil current collector have been layered at the end of electrolysis, the electrode material and aluminum foil current collector can be effectively separated. After drying, aluminum foil and lithium-repaired lithium iron phosphate material can be obtained, and the lithium-repaired lithium iron phosphate material is ball milled to obtain a lithium iron phosphate powder with uniform particle dispersion;

[0011] Step 4: Place the lithium iron phosphate powder obtained in step 3 in an inert atmosphere of nitrogen or argon, and calcine to obtain a repaired regenerated lithium iron phosphate positive electrode material.

[0012] Further, in step 1, the waste positive electrode sheet is one or more of lithium iron phosphate, lithium cobaltate, lithium manganate, nickel cobalt manganese acid lithium, and nickel cobalt aluminum acid lithium positive electrode sheet, preferably lithium iron phosphate. That is, in the electrolysis of step 2, the positive electrode can use any of the above waste positive electrode sheets, and the negative electrode needs to use a waste lithium iron phosphate positive electrode sheet.

[0013] Further, in step 1, the positive electrode sheet is immersed in the DMC solvent for 3-5 hours.

[0014] Further, in step 2, the lithium salt is one or more of lithium chloride, lithium sulfate, lithium nitrate, lithium acetate, and lithium hydroxide, preferably lithium sulfate.

[0015] Further, in step 2, the constant current electrolysis time is 1-24 hours, the reaction temperature is 10-50°C, the current range is 1-100 mA, and the voltage range is 0.1-10 V.

[0016] Further, in step 3, the drying temperature is 50-100°C, and the drying time is 1-24 hours.

[0017] Further, in step 3, the ball milling is carried out at a rotation speed of 600-1500 rpm for 1-10 h.

[0018] Further, in step 4, the calcination is carried out at a temperature rising rate of 1-10 ℃ / min to 200-500 ℃, and then the temperature is kept for 1-12 h, and then the temperature is naturally cooled to room temperature.

[0019] The method of the present application uses lithium in the waste lithium ion battery positive electrode material as a lithium source, and through the electric field driving, the lithium extracted from the waste positive electrode material is embedded into the negative electrode side waste lithium iron phosphate material, so as to realize the lithium supplement repair of the waste lithium iron phosphate material. This method has three advantages: first, the lithium resource in the waste lithium ion battery positive electrode material can be selectively extracted and effectively recycled; second, the waste lithium iron phosphate material can be repaired and regenerated by supplementing lithium, so as to prepare new lithium iron phosphate electrode material; third, useful materials such as iron phosphate, cobalt oxide and manganese oxide can be obtained after lithium extraction. Compared with the conventional waste lithium ion battery electrode material recycling process, the present application has the advantages of simple process, green environmental protection, low cost and the like.

[0020] Compared with the prior art, the beneficial effects of the present application are as follows:

[0021] The present application discloses a method for recycling lithium from waste lithium ion batteries and repairing lithium iron phosphate material, which comprises the following steps: pretreating the waste lithium ion positive electrode material by organic solvent dissolution, and then using electric field driving to extract lithium from the positive electrode side waste positive electrode material of lithium ion battery on the one hand, and to electrochemically supplement lithium to the negative electrode side waste lithium iron phosphate material on the other hand, so as to make up for the lithium loss of the waste lithium iron phosphate material during the use of multiple charging and discharging, and to repair the electrochemical performance of the lithium iron phosphate positive electrode material. The present application can effectively solve the problem of lithium extraction and recycling of various waste lithium ion battery positive electrode materials while repairing and regenerating lithium iron phosphate material, and realize the universal recycling of positive electrode materials in retired lithium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The present application discloses a method for recycling lithium from waste lithium ion batteries and repairing lithium iron phosphate material, which comprises the following steps: pretreating the waste lithium ion positive electrode material by organic solvent dissolution, and then using electric field driving to extract lithium from the positive electrode side waste positive electrode material of lithium ion battery on the one hand, and to electrochemically supplement lithium to the negative electrode side waste lithium iron phosphate material on the other hand, so as to make up for the lithium loss of the waste lithium iron phosphate material during the use of multiple charging and discharging, and to repair the electrochemical performance of the lithium iron phosphate positive electrode material. The present application can effectively solve the problem of lithium extraction and recycling of various waste lithium ion battery positive electrode materials while repairing and regenerating lithium iron phosphate material, and realize the universal recycling of positive electrode materials in retired lithium ion batteries.

[0023] Figure 2 The present application discloses a method for recycling lithium from waste lithium ion batteries and repairing lithium iron phosphate material, which comprises the following steps: pretreating the waste lithium ion positive electrode material by organic solvent dissolution, and then using electric field driving to extract lithium from the positive electrode side waste positive electrode material of lithium ion battery on the one hand, and to electrochemically supplement lithium to the negative electrode side waste lithium iron phosphate material on the other hand, so as to make up for the lithium loss of the waste lithium iron phosphate material during the use of multiple charging and discharging, and to repair the electrochemical performance of the lithium iron phosphate positive electrode material. The present application can effectively solve the problem of lithium extraction and recycling of various waste lithium ion battery positive electrode materials while repairing and regenerating lithium iron phosphate material, and realize the universal recycling of positive electrode materials in retired lithium ion batteries.

[0024] Figure 3 The present application discloses a method for recycling lithium from waste lithium ion batteries and repairing lithium iron phosphate material, which comprises the following steps: pretreating the waste lithium ion positive electrode material by organic solvent dissolution, and then using electric field driving to extract lithium from the positive electrode side waste positive electrode material of lithium ion battery on the one hand, and to electrochemically supplement lithium to the negative electrode side waste lithium iron phosphate material on the other hand, so as to make up for the lithium loss of the waste lithium iron phosphate material during the use of multiple charging and discharging, and to repair the electrochemical performance of the lithium iron phosphate positive electrode material. The present application can effectively solve the problem of lithium extraction and recycling of various waste lithium ion battery positive electrode materials while repairing and regenerating lithium iron phosphate material, and realize the universal recycling of positive electrode materials in retired lithium ion batteries.

[0025] Figure 4The first circle charge-discharge curve of the button cell prepared from the repaired and regenerated lithium iron phosphate positive electrode material and the waste lithium iron phosphate positive electrode material of Example 1 of the present application at a current density of 0.1 C is shown in the following figure.

[0026] Figure 5 The rate performance graph of the button cell prepared from the repaired and regenerated lithium iron phosphate positive electrode material and the waste lithium iron phosphate positive electrode material of Example 1 of the present application is shown in the following figure. DETAILED DESCRIPTION

[0027] The embodiments of the present application are described in detail below, and the embodiments are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0028] Example 1

[0029] As shown in the following figure, the lithium iron phosphate positive electrode material is recovered and regenerated from the waste lithium iron phosphate battery according to the following steps: Figure 1

[0030] The retired lithium iron phosphate battery with lithium iron phosphate as the positive electrode material is discharged and disassembled to obtain the waste lithium iron phosphate positive electrode sheet. The positive electrode sheet is soaked in DMC solvent at room temperature for 3 h to remove the residual electrolyte in the positive electrode sheet. Then the sheet is taken out and washed with deionized water to remove DMC, and a pretreated positive electrode sheet is obtained.

[0031] Two pretreated positive electrode sheets are respectively used as the positive electrode and the negative electrode and placed in a direct current electrolytic cell. An electrochemical method is used to electrolyze in a 1 mol / L lithium sulfate solution for 1 h, with an initial current of 10 mA, a reaction temperature of 20 ℃, and a voltage of 0.1-3 V. Lithium ions in the positive electrode sheet are driven by the electric field to be deintercalated into the solution, and the negative electrode sheet is reduced to supplement lithium to obtain a repaired lithium iron phosphate sheet.

[0032] The repaired lithium iron phosphate sheet and the lithium-depleted lithium iron phosphate sheet are respectively placed in a 100 ℃ oven for drying for 12 h. Since the electrode material and the aluminum foil current collector have been layered at the end of electrolysis, the aluminum foil, lithium iron phosphate, and lithium-supplemented repaired lithium iron phosphate material can be obtained after drying. The lithium-supplemented repaired lithium iron phosphate material is ball milled at a speed of 1200 rpm for 2 h to obtain a lithium iron phosphate powder with uniform particle dispersion.

[0033] The electrochemically lithium-supplemented repaired lithium iron phosphate powder is placed in a nitrogen atmosphere, heated to 300 ℃ at a rate of 5 ℃ / min, and heat treated for 6 h, and then naturally cooled to room temperature to obtain a repaired and regenerated lithium iron phosphate positive electrode material.

[0034] Figure 2 ​The image shows the XRD pattern of the regenerated lithium iron phosphate cathode material obtained by electrochemical lithium replenishment in this embodiment. It can be seen from the figure that its diffraction peaks correspond to the lithium iron phosphate standard card (JPCDS: 83-2092), and the peaks are sharp with no impurity peaks.

[0035] Figure 3 The image shows the XRD pattern of the iron phosphate obtained by electrochemical delithiation in this embodiment. It can be seen from the figure that its diffraction peaks correspond to the standard card of iron phosphate of the isophosphorus manganese iron type (JPCDS: 70-1555), which is consistent with the crystal structure of the delithiation product of lithium iron phosphate.

[0036] The regenerated lithium iron phosphate cathode material obtained in this embodiment and waste lithium iron phosphate cathode material (to obtain the original performance of the waste lithium iron phosphate cathode material, the powder scraped off the pretreated cathode sheet was used as the waste lithium iron phosphate cathode material) were thoroughly mixed with acetylene black and polyvinylidene fluoride (PVDF) at a ratio of 8:1:1 (mass ratio). NMP (1-methyl-2-pyrrolidone) was added to form a paste, which was then uniformly coated onto aluminum foil to a thickness of 75 μm. The coating was dried at 80 °C, rolled, and cut into cathode sheets with a diameter of 12 mm, and then vacuum dried for later use. Using lithium metal sheets as the negative electrode and Cellgard 2400 polypropylene membrane as the separator, CR2032 coin cells were assembled in an argon glove box. The cells were then subjected to constant voltage and constant current charge-discharge tests at 25 °C.

[0037] Figure 4 The first charge-discharge curves of coin cells prepared from regenerated lithium iron phosphate cathode material and waste lithium iron phosphate cathode material at a current density of 0.1 C are shown in the figure. It can be seen from the figure that the first charge-discharge capacity of the regenerated lithium iron phosphate cathode material is 119.3 mAh / g and 147.0 mAh / g, respectively, which is significantly higher than that of the waste cathode powder (75.5 mAh / g and 105.4 mAh / g).

[0038] Figure 5The graph shows the rate performance of coin cells prepared from repaired and regenerated lithium iron phosphate cathode materials and waste lithium iron phosphate cathode materials. As can be seen from the graph, the discharge capacities of the repaired and regenerated lithium iron phosphate cathode material at 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, 5 C, and 10 C are 154.1 mAh / g, 151.0 mAh / g, 145.5 mAh / g, 141.9 mAh / g, 134.7 mAh / g, 125.5 mAh / g, and 115.5 mAh / g, respectively. These are significantly higher than the 107.0 mAh / g, 105.4 mAh / g, 104.04 mAh / g, 100.8 mAh / g, 97.5 mAh / g, 91.1 mAh / g, and 84.5 mAh / g of the waste cathode powder. Electrochemical test results show that electrochemical lithium replenishment can effectively restore the electrochemical performance of waste lithium iron phosphate cathode materials.

[0039] Example 2

[0040] This embodiment recycles and regenerates lithium iron phosphate cathode materials from waste lithium cobalt oxide batteries and lithium iron phosphate batteries according to the following steps:

[0041] Retired lithium iron phosphate batteries with lithium iron phosphate cathodes were discharged and disassembled to obtain waste lithium iron phosphate electrodes. The lithium iron phosphate electrodes were then immersed in DMC solvent at room temperature for 3 hours to dissolve and remove residual electrolyte. The lithium iron phosphate electrodes were then removed and rinsed with deionized water to remove DMC, resulting in pretreated lithium iron phosphate electrodes.

[0042] Retired lithium cobalt oxide batteries with lithium cobalt oxide as the positive electrode material were discharged and disassembled to obtain waste lithium cobalt oxide electrodes. The lithium cobalt oxide electrodes were then immersed in DMC solvent at room temperature for 3 hours to dissolve and remove residual electrolyte. The lithium cobalt oxide electrodes were then removed and rinsed with deionized water to remove DMC, resulting in pretreated lithium cobalt oxide electrodes.

[0043] Pretreated lithium cobalt oxide and lithium iron phosphate electrodes were used as the positive and negative electrodes, respectively, and placed in a DC electrolytic cell. Electrochemical electrolysis was performed in a 1 mol / L lithium sulfate solution for 1 h at a constant current of 10 mA, a reaction temperature of 20 °C, and a voltage of 0.1–3 V. Lithium ions in the positive lithium cobalt oxide electrode were deintercalated into the solution under the drive of the electric field, while the negative lithium iron phosphate electrode underwent reduction and lithium replenishment to obtain a repaired lithium iron phosphate electrode.

[0044] The repaired lithium iron phosphate electrode and the delithiated cobalt oxide electrode were dried in an oven at 100 °C for 12 h. Since the electrode material and the current collector aluminum foil had already separated at the end of electrolysis, aluminum foil, cobalt oxide, and lithium iron phosphate material repaired by lithium replenishment could be obtained after drying. The lithium iron phosphate material repaired by lithium replenishment was ball-milled at 1200 rpm for 2 h to obtain lithium iron phosphate powder with uniform particle dispersion.

[0045] The electrochemically repaired lithium iron phosphate powder was calcined under a nitrogen atmosphere, heated to 300 ℃ at a heating rate of 5 ℃ / min, held at that temperature for 6 h, and finally naturally cooled to room temperature to obtain the repaired and regenerated lithium iron phosphate cathode material.

[0046] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering lithium from waste lithium-ion batteries and simultaneously repairing lithium-iron-phosphate materials, characterized in that, Comprising the following steps: Step 1: Discharge and disassemble the retired lithium ion battery to obtain the waste positive electrode sheet, immerse the positive electrode sheet in the DMC solvent at room temperature, dissolve and remove the residual electrolyte in the positive electrode sheet, then take out the positive electrode sheet and wash it with deionized water to remove the DMC, and obtain the pretreated positive electrode sheet; Step 2: Take the pretreated positive electrode sheet obtained in step 1 as the positive electrode, place it in a direct current electrolysis cell, use the waste lithium iron phosphate positive electrode sheet pretreated by the same method as step 1 as the negative electrode, and use the electrochemical method to electrolyze in a 0.1-2 mol / L lithium salt solution, the constant current electrolysis time is 1-24 h, the reaction temperature is 10-50 ℃, the current range is 1-100 mA, and the voltage range is 0.1-10 V, the lithium ions in the positive electrode sheet are driven by the electric field and are embedded into the solution, and the negative electrode sheet is reduced and supplemented with lithium to obtain a repaired lithium iron phosphate electrode sheet; Step 3: Dry the repaired lithium iron phosphate electrode sheet in step 2 in an oven to obtain an aluminum foil and a lithium-supplemented repaired lithium iron phosphate material, ball mill the lithium-supplemented repaired lithium iron phosphate material to obtain a lithium iron phosphate powder with uniform particle dispersion; Step 4: Place the lithium iron phosphate powder obtained in step 3 in an inert atmosphere and calcine to obtain a repaired regenerated lithium iron phosphate positive electrode material.

2. The method of claim 1, wherein: In step 1, the waste positive electrode sheet is one or more of lithium iron phosphate, lithium cobaltate, lithium manganate, nickel cobalt manganate, and nickel cobalt aluminumate.

3. The method of claim 1, wherein: In step 1, the soaking time of the positive electrode sheet in the DMC solvent is 3-5 h.

4. The method of claim 1, wherein: In step 2, the lithium salt is one or more of lithium chloride, lithium sulfate, lithium nitrate, lithium acetate, and lithium hydroxide.

5. The method of claim 1, wherein: In step 3, the drying temperature is 50-100 ℃, and the drying time is 1-24 h.

6. The method of claim 1, wherein: In step 3, the ball milling is carried out at a speed of 600-1500 rpm for 1-10 h.

7. The method of claim 1, wherein: In step 4, the calcination is carried out at a heating rate of 1-10 ℃ / min to 200-500 ℃, and then naturally cooled to room temperature.

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