Regeneration method of waste lithium battery positive electrode material

Abstract

The invention provides a regeneration method of a waste lithium battery positive electrode material, and belongs to the technical field of battery recovery. The regeneration method of the waste lithium battery positive electrode material comprises the following steps: pretreating the disassembled waste lithium cobalt oxide battery positive electrode material to obtain a sheet material, mixing the sheet material with a lithium compound, calcining in an oxygen atmosphere, filtering, putting into an oxalic acid solution for reaction, and reacting with an oxidant under an alkaline condition to obtain the waste lithium battery positive electrode material. The spinel phase converted from the layered structure is subjected to in-situ oxidation to form a hydroxyl cobalt oxide intermediate; and finally, the hydroxyl cobalt oxide intermediate and a lithium supplement agent are mixed and calcined to complete regeneration of the waste lithium battery positive electrode material. According to the regeneration method of the waste lithium battery positive electrode material, the operation condition is mild, the CoOOH layered structure constructed preferentially through pre-oxidation can be more beneficial to the lithium supplementing process of the lithium ion battery, the lithium supplementing efficiency can be remarkably improved, and the lithium supplementing condition is reduced. The regeneration method disclosed by the invention is short in operation period, less in generated harmful waste gas and waste liquid and suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of battery recycling, and in particular relates to a method for regenerating positive electrode materials of waste lithium batteries. Background Art

[0002] Lithium-ion batteries (LIBs) are widely used because of their high energy density and long service life. In recent years, clean energy has become a research boom, the new energy vehicle market has shown explosive growth, and the demand for LIBs has increased exponentially. Lithium-ion batteries are mainly composed of five parts: positive electrode, negative electrode, diaphragm, electrolyte and shell. The positive electrode is generally composed of aluminum foil and materials such as lithium cobalt oxide, lithium manganese oxide, nickel cobalt manganese lithium, etc. If the used batteries are discarded directly, the heavy metals and electrolytes contained in them will cause great harm to the environment. If they can be recycled and reused, it will greatly alleviate the current resource shortage and environmental problems. In the current LIBs recycling process, it is often necessary to reduce the used LIBs positive electrode materials in order to leach out the different metal ions in the positive electrode materials and then recycle them separately.

[0003] However, the current recycling and application processes of waste lithium battery positive electrodes still have the following shortcomings: (1) General pyrometallurgical recycling technology requires high temperature, often requires the addition of additional reducing agents, and is prone to produce harmful gases; (2) Wet recycling technology requires a large amount of acid / alkaline solution, which will cause secondary pollution problems; (3) Biological recovery methods require constant attention to the living conditions of microorganisms, have high requirements for the external environment, and are not suitable for large-scale applications.

[0004] At the same time, since the ordinary recycling process is based on the destruction and reconstruction of the structure of waste positive electrode materials, more energy is often required to rebuild the structure during the regeneration process; and the direct regeneration process produces a spinel structure due to surface phase change, which causes the supplemented lithium ions to accumulate on the surface of the material and cannot enter the crystal lattice, resulting in poor lithium replenishment effect. Summary of the invention

[0005] The present invention is made to solve the above-mentioned problem, and its purpose is to provide a method for regenerating positive electrode materials of waste lithium batteries.

[0006] The invention provides a method for regenerating positive electrode materials of waste lithium batteries, which has the following characteristics and comprises the following steps: S10, pre-treating the positive electrode materials of waste cobalt oxide lithium batteries obtained by disassembly to obtain sheet materials; S20, mixing the sheet materials with lithium compounds and calcining them at 200°C to 300°C in an O2(g) atmosphere to obtain a solid mixture, wherein the lithium compounds are a mixture of lithium hydroxide and lithium nitrate in a mass ratio of 2:3, and the mass ratio of the sheet materials to the lithium compounds is (0.1 to 2):8; S30, washing and filtering the solid mixture to obtain a foil-shaped positive electrode to be treated; S40, putting the positive electrode to be treated into oxalic acid (aq) for reaction to obtain a first reaction solution; S5 0, adjusting the pH of the first reaction solution to be alkaline to obtain a second reaction solution; S60, heating the second reaction solution to 70°C to 90°C, and gradually adding sodium persulfate (s) or H2O2 (aq) during the heating process to react for a period of time to obtain a precipitate, wherein the molar ratio of sodium persulfate or H2O2 to the positive electrode to be treated is (10-20):1; S70, drying the precipitate and mixing it with a lithium replenisher in a mass ratio of 1:(0.5-2), and then calcining it at 800°C to 900°C to obtain regenerated lithium cobalt oxide, thereby completing the regeneration of the waste lithium battery positive electrode material, wherein the lithium replenisher includes any one or more of lithium carbonate, lithium sulfate or lithium hydroxide.

[0007] The method for regenerating the positive electrode material of waste lithium battery provided by the present invention may also have the following characteristics: wherein step S10 includes the following sub-steps: S11, soaking the disassembled positive electrode material of waste lithium cobalt oxide battery in ethanol for 20 minutes to 30 minutes to remove the electrolyte residual on the surface thereof; S12, naturally drying the positive electrode material of waste lithium cobalt oxide battery soaked in step S11; S13, cutting the positive electrode material of waste lithium cobalt oxide battery dried in step S12 into sheets of 2 cm×1 cm to obtain sheet material.

[0008] The method for regenerating waste lithium battery positive electrode materials provided by the present invention may also have the following characteristics: wherein, in step S20, the mass ratio of the sheet material to the lithium compound is 1:8, the heating rate of calcination is 5°C / min, and the calcination time is 10min to 30min.

[0009] The method for regenerating the positive electrode material of waste lithium batteries provided by the present invention may also have the following characteristics: wherein, in step S30, the washing method is ultrasonication in deionized water for 2 minutes to 5 minutes, and the filtering method is vacuum filtration.

[0010] The method for regenerating the positive electrode material of waste lithium batteries provided by the present invention may also have the following characteristics: wherein, in step S40, the concentration of oxalic acid in oxalic acid (aq) is 0.05 mol / L to 0.2 mol / L.

[0011] The method for regenerating the positive electrode material of waste lithium batteries provided by the present invention may also have the following feature: wherein, in step S50, the alkaline solution used for adjusting the pH is NaOH (aq) or LiOH (aq).

[0012] The method for regenerating the positive electrode material of waste lithium batteries provided by the present invention may also have the following characteristics: wherein, in step S50, the concentration of the alkali solution is 0.3 mol / L to 0.5 mol / L.

[0013] The method for regenerating the positive electrode material of waste lithium batteries provided by the present invention may also have the following characteristics: wherein, in step S60, the molar ratio of sodium persulfate to the positive electrode to be treated is 15:1, the concentration of H2O2 in H2O2 (aq) is 2 mol / L to 3 mol / L, and the reaction time is 30 min to 60 min.

[0014] min.

[0015] The method for regenerating the positive electrode material of waste lithium batteries provided by the present invention may also have the following characteristics: wherein, in step S70, the calcination time is 5 hours to 8 hours.

[0016] The method for regenerating the positive electrode material of waste lithium batteries provided by the present invention may also have the following characteristics: wherein, in step S70, the precipitation drying temperature is 90° C. to 180° C., and the drying time is 6 h to 12 h.

[0017] Functions and Effects of the Invention

[0018] The method for regenerating the positive electrode material of waste lithium batteries involved in the present invention has the following beneficial effects:

[0019] (1) The present invention adopts a direct regeneration method of pre-oxidation followed by calcination, which abandons the traditional complex process of first leaching the waste positive electrode material to separate the different metal components and then recovering them separately to obtain the precursors, and does not generate secondary pollution such as waste liquid and waste gas. Therefore, the preparation method is simple in process, mild in conditions, convenient in equipment, short in preparation cycle, and suitable for industrial production.

[0020] (2) The present invention adopts a direct regeneration method of calcination to supplement lithium, which avoids the problem of leaching and separation required in the traditional regeneration process, thereby destroying the valuable layered structure of the positive electrode material. Less energy is consumed in the process flow, which is conducive to reducing the use of chemical agents and lowering the process conditions of the regeneration process.

[0021] (3) The method for regenerating waste lithium battery positive electrode materials of the present invention is based on the in-situ construction of a cobalt hydroxide oxide intermediate having the same layered structure as the lithium cobalt oxide positive electrode material (in step S60, the spinel phase transformed from the layered structure in the waste positive electrode material is in-situ oxidized to a cobalt hydroxide oxide intermediate). It not only targets the spinel structure produced by the phase change during the use of the battery, avoiding the damage to the layered structure, but also repairs the spinel structure produced by the phase change collapse, achieving a conversion efficiency of more than 95% from the spinel structure to the layered structure, significantly improving the lithium replenishment efficiency in the subsequent process, and significantly improving the electrochemical performance of the regenerated electrode material.

[0022] (4) The method for regenerating the positive electrode material of waste lithium batteries of the present invention does not require strong acid leaching, thereby greatly reducing harmful waste liquid in the regeneration process, and the electrochemical performance is greatly improved compared with ordinary regenerated electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flowchart of a method for regenerating positive electrode materials of waste lithium batteries according to an embodiment of the present invention;

[0024] Figure 2 is the X-ray diffraction pattern of sample 1 (regenerated lithium cobalt oxide) of an embodiment of the present invention;

[0025] Figure 3 is a SEM image of sample 1 (regenerated lithium cobalt oxide) of an embodiment of the present invention;

[0026] Figure 4 This is a TEM image of Sample 3 (regenerated lithium cobalt oxide) according to an example of the present invention. DETAILED DESCRIPTION

[0027] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following embodiments and the accompanying drawings specifically illustrate a method for regenerating a waste lithium battery positive electrode material of the present invention.

[0028] <Example>

[0029] Figure 1 It is a flowchart of a method for regenerating positive electrode materials of waste lithium batteries according to an embodiment of the present invention.

[0030] like Figure 1 As shown, this embodiment provides a method for regenerating anode materials of waste lithium batteries, comprising the following steps:

[0031] S10, preprocessing, includes the following sub-steps S11 to S13:

[0032] S11, soaking the disassembled waste lithium cobalt oxide battery positive electrode material in ethanol for 20 minutes to remove the electrolyte remaining on the surface thereof.

[0033] S12, naturally drying the waste lithium cobalt oxide battery positive electrode material after being soaked in step S11.

[0034] S13, cutting the waste lithium cobalt oxide battery positive electrode material dried in step S12 into sheets of 2 cm×1 cm to obtain sheet materials.

[0035] S20, mixing the flaky material and the lithium compound in a mass ratio of 1:8, heating the mixture to 200° C. to 300° C. at a rate of 5° C. / min in an O2(g) atmosphere in a muffle furnace, and calcining the mixture for 30 min to obtain a solid mixture.

[0036] In this step, the lithium compound is a mixture of lithium hydroxide and lithium nitrate in a mass ratio of 2:3.

[0037] S30, placing the solid mixture obtained in step S20 into deionized water for 2 minutes of ultrasonic treatment, and then filtering to obtain a foil-shaped positive electrode to be treated.

[0038] S40, putting the positive electrode to be treated obtained in step S30 into 0.05 mol / L oxalic acid (aq), stirring at a rotation speed of 400 rpm, and reacting to obtain a first reaction solution.

[0039] S50, using 0.3 mol / L alkaline solution to adjust the pH of the first reaction solution to alkaline, to obtain a second reaction solution.

[0040] S60, heating the second reaction liquid to 70° C., gradually adding an oxidant during the heating process, and stirring the reaction at a rotation speed of 400 rpm for 30 minutes to obtain a precipitate.

[0041] S70, drying the precipitate at 90° C. for 12 hours, mixing it with a lithium supplement agent, and calcining it at 900° C. for 8 hours to obtain regenerated lithium cobalt oxide, thereby completing the regeneration of the waste lithium battery positive electrode material.

[0042] The lithium supplement is any one or more of lithium carbonate, lithium sulfate or lithium hydroxide. Specifically, the lithium supplement in this embodiment is lithium carbonate, and the mass ratio of lithium carbonate to the dried precipitate is 1:1.

[0043] Specifically, in this embodiment, a method for regenerating waste lithium battery positive electrode materials is used to regenerate waste lithium cobalt oxide battery positive electrode materials, and a total of 5 samples are prepared, which are respectively recorded as sample 1, sample 2, sample 3, sample 4 and sample 5.

[0044] In this embodiment, samples 1 to 5 are used as positive electrode active materials and lithium sheets are used as negative electrodes to assemble CR2025 button batteries, thereby obtaining battery 1, battery 2, battery 3, battery 4 and battery 5.

[0045] Among them, the positive electrodes of batteries 1 to 5 were prepared by the following steps: acetylene carbon black, binder and positive electrode active material (regenerated lithium cobalt oxide material, i.e., a single type of sample 1 to sample 5) were prepared into a slurry in a mass ratio of 1:1:8 using N-methyl-pyrrolidone (NMP), coated on the carbon-coated aluminum foil of the current collector and dried, and the dried electrode sheets were cut into discs with a diameter of 14 mm, which were the positive electrodes of batteries 1 to 5.

[0046] Batteries 1 to 5 use a PE single-layer film as a separator.

[0047] Batteries 1 to 5 used a mixed solution of 1 mol / L LiPF6 in ethylene carbonate (EC) / dimethyl carbonate (DMC) as the electrolyte.

[0048] Subsequently, a battery testing system (Wuhan Blue Electric Electronics Co., Ltd.) was used to perform charge and discharge tests on the assembled button batteries (Battery 1 to Battery 5) with a voltage range of 3V to 4.6V. The specific capacity of Battery 1 to Battery 5 was tested at a rate of 0.2C.

[0049] In this embodiment, specific parameters in the preparation process of samples 1 to 5 and the battery performances of batteries 1 to 5 prepared using samples 1 to 5 are shown in Table 1 below.

[0050] Table 1 (Specific parameters in the preparation process of samples 1 to 5, battery performance of batteries 1 to 5)

[0051]

[0052] Figure 2 This is an X-ray diffraction pattern of Sample 1 (regenerated lithium cobalt oxide) according to an example of the present invention.

[0053] As shown in Table 1 above and Figure 2 As shown, the sample 1 (regenerated lithium cobalt oxide battery positive electrode material) obtained above was measured by an X-ray diffractometer (model D / Max-2550PC produced by RIGAKU, Japan). It can be seen that the (108) / (110) diffraction characteristic peak is split significantly, which can be attributed to the typical layered hexagonal α-NaFeO2 structure. This shows that the material of sample 1 has a good layered structure and the crystallinity of the material has also been restored, which shows that the lithium cobalt oxide structure and performance of the prepared sample 1 have been restored.

[0054] Figure 3 This is a SEM image of Sample 1 (regenerated lithium cobalt oxide) according to an example of the present invention.

[0055] As shown in Table 1 above and Figure 3As shown, the regenerated lithium cobalt oxide of sample 1 effectively repairs the lattice structure of the waste lithium cobalt oxide material, the regenerated material can obtain a smooth and flat surface, and can restore the specific capacity of the waste lithium cobalt oxide material to 144.2 mAh / g.

[0056] Figure 4 This is a TEM image of Sample 3 (regenerated lithium cobalt oxide) according to an example of the present invention.

[0057] As shown in Table 1 above and Figure 4 As shown, the phase change layer on the particle surface of sample 3 is completely converted into lithium cobalt oxide component.

[0058] As shown in Table 1 above, the specific parameters in the preparation process of samples 1 to 5 and the battery performance data of batteries 1 to 5 show:

[0059] (1) The change of calcination temperature in step S20 will affect the decomposition process of the binder in the electrode during the calcination process. When the temperature is too high, the binder decomposes to produce HF and reacts with the positive electrode material to form LiF, resulting in an increase in the impedance of the material. Therefore, the calcination temperature is negatively correlated with the specific capacity of the battery prepared from the recycled material.

[0060] (2) LiOH(aq) can provide more Li compared to NaOH(aq) while building an alkaline environment. + , while Li in solution + During the heating process, it can be partially embedded in the material, providing the material with more specific capacity.

[0061] (3) Increasing the concentration of NaOH(aq) has no significant effect on the battery specific capacity; however, increasing the concentration of LiOH(aq) within a certain range can have a positive effect on the battery specific capacity.

[0062] (4) The oxidant is either Na2S2O8 or H2O2, which oxidizes the surface of the material into cobalt oxyhydroxide material.

[0063] (5) When the oxidant is in excess, the spinel phase can be completely oxidized to cobalt oxyhydroxide.

[0064] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for regenerating anode materials of waste lithium batteries, characterized in that: The following steps are involved: S10, pre-treating the disassembled waste lithium cobalt oxide battery positive electrode material to obtain a sheet material; S20, mixing the sheet material with a lithium compound and calcining the mixture at 200° C. to 300° C. in an O2(g) atmosphere to obtain a solid mixture, wherein the lithium compound is a mixture of lithium hydroxide and lithium nitrate in a mass ratio of 2:3, and the mass ratio of the sheet material to the lithium compound is (0.1 to 2):8; S30, washing and filtering the solid mixture to obtain a foil-shaped positive electrode to be treated; S40, putting the positive electrode to be treated into oxalic acid (aq) to react and obtain a first reaction solution; S50, adjusting the pH of the first reaction solution to be alkaline to obtain a second reaction solution; S60, heating the second reaction solution to 70° C. to 90° C., and gradually adding sodium persulfate (s) or H2O2 (aq) during the heating process to react for a period of time to obtain a precipitate, wherein the molar ratio of sodium persulfate or H2O2 to the positive electrode to be treated is (10-20):1; S70, drying the precipitate and mixing it with a lithium replenisher in a mass ratio of 1:(0.5-2), and calcining at 800° C.-900° C. to obtain regenerated lithium cobalt oxide, thereby completing the regeneration of the waste lithium battery positive electrode material, wherein the lithium replenisher includes any one or more of lithium carbonate, lithium sulfate or lithium hydroxide.

2. The method for regenerating the positive electrode material of waste lithium batteries according to claim 1, characterized in that: in, Step S10 includes the following sub-steps: S11, soaking the disassembled waste lithium cobalt oxide battery positive electrode material in ethanol for 20 minutes to 30 minutes to remove the electrolyte remaining on the surface; S12, naturally drying the waste lithium cobalt oxide battery positive electrode material after soaking in step S11; S13, cutting the waste lithium cobalt oxide battery positive electrode material dried in step S12 into sheets of 2 cm×1 cm to obtain the sheet material.

3. The method for regenerating the positive electrode material of waste lithium batteries according to claim 1, characterized in that: in, In step S20, the mass ratio of the sheet material to the lithium compound is 1:

8. The heating rate of calcination is 5°C / min, and the calcination time is 10min to 30min.

4. The method for regenerating the positive electrode material of waste lithium batteries according to claim 1, characterized in that: in, In step S30, the washing method is ultrasonication in deionized water for 2 minutes to 5 minutes, and the filtering method is vacuum filtration.

5. The method for regenerating the positive electrode material of waste lithium batteries according to claim 1, characterized in that: in, In step S40, the oxalic acid concentration in oxalic acid (aq) is 0.05 mol / L to 0.2 mol / L.

6. The method for regenerating the positive electrode material of waste lithium batteries according to claim 1, characterized in that: in, In step S50, the alkaline solution used to adjust the pH is NaOH (aq) or LiOH (aq).

7. The method for regenerating the positive electrode material of waste lithium batteries according to claim 6, characterized in that: in, In step S50, the concentration of the alkali solution is 0.3 mol / L to 0.5 mol / L.

8. The method for regenerating the positive electrode material of waste lithium batteries according to claim 1, characterized in that: in, In step S60, the molar ratio of sodium persulfate to the positive electrode to be treated is 15:

1. The concentration of H2O2 in H2O2(aq) is 2mol / L~3mol / L. Reaction time: 30min~60min.

9. The method for regenerating the positive electrode material of waste lithium batteries according to claim 1, characterized in that: in, In step S70, the calcination time is 5 h to 8 h.

10. The method for regenerating the positive electrode material of waste lithium batteries according to claim 1, characterized in that: in, In step S70, the precipitation drying temperature is 90°C to 180°C, and the drying time is 6h to 12h.

Images