Method for repairing positive electrode active material

Abstract

The invention provides a method for repairing a positive electrode active material, which comprises the following steps: (i) providing a positive electrode active material to be repaired, the positive electrode active material to be repaired being obtained by separating a current collector in a positive electrode plate from the positive electrode active material; and (ii) heating a lithium supplementing material to obtain an atmosphere containing a gaseous lithium source, and sintering the positive electrode active material to be repaired in the atmosphere containing the gaseous lithium source to obtain the repaired positive electrode active material.

Description

Technical Field

[0001] The present application relates to the field of energy storage, and particularly provides a method for repairing cathode active materials. Background Art

[0002] Lithium-ion batteries have the advantages of small volume, high energy density, high safety, etc., and are more and more widely used in the fields of energy storage devices, electric vehicles, etc. The heavy metals contained in retired batteries are potential environmental pollution risks. In addition, the rapid development of the lithium-ion battery industry has led to a sharp increase in the demand for cobalt and lithium. Therefore, the research on the recycling and utilization of waste lithium-ion batteries is a very necessary and urgent task.

[0003] At present, the recycling technologies of waste lithium-ion batteries include pyrometallurgy, hydrometallurgy and direct repair method. Among them, pyrometallurgy recovers battery materials by calcination; hydrometallurgy uses acid leaching and extraction to extract valuable metals; the direct repair method restores the performance of electrode materials by directional defect repair of electrode materials. In contrast, the direct repair method has the advantages of low pollution, low energy consumption and low cost, and can achieve the repair output of electrode-electrode, which has attracted more attention from researchers. Among them, the solid-state sintering method follows the sintering process in the synthesis of cathode materials, mainly measures the ratio of lithium and transition metal elements in the cathode powder by ICP, and then quantitatively adds lithium salts for roasting. However, this type of method has high requirements for the accuracy of ICP measurement, and the ICP process is long, which affects the production rhythm. In addition, there are problems such as uneven lithium distribution in the products recovered by this type of method.

[0004] Therefore, there is a need to improve and optimize the repair method of cathode active materials in industry. Summary of the Invention

[0005] In order to solve the above problems, the object of the present invention is to provide a method for repairing cathode active materials, especially cathode active materials of lithium-ion batteries, the method comprising the following steps:

[0006] (i) providing the cathode active material to be repaired, the cathode active material to be repaired being obtained by separating the current collector from the cathode active material in the cathode electrode;

[0007] (ii) heating the lithium supplement material to obtain an atmosphere containing a gaseous lithium source, and sintering the cathode active material to be repaired in the atmosphere containing the gaseous lithium source to obtain the repaired cathode active material.

[0008] By means of the method according to the present invention, the cathode active material to be repaired is subjected to uniform lithium supplementation distribution in an atmosphere containing a gaseous lithium source, thereby obtaining excellent electrochemical performance of the repaired cathode active material, especially comparable to that of a new cathode active material. At the same time, due to the convenience and continuity of this "one-step" lithium supplementation process, the recycling efficiency of waste lithium-ion batteries is greatly improved.

[0009] According to an embodiment of the present invention, the lithium supplementation material exists in the form of powder or granules, especially in the form of powder.

[0010] According to an embodiment of the present invention, in step (ii), the lithium supplementation material is heated to 800 to 1000 °C to obtain the gaseous lithium source.

[0011] According to an embodiment of the present invention, in step (ii), the heating time is 4 to 7 hours;

[0012] According to an embodiment of the present invention, in step (ii), the sintering is carried out at a temperature of 600 to 900 °C;

[0013] According to an embodiment of the present invention, in step (ii), the sintering time is 6 to 12 hours.

[0014] According to an embodiment of the present invention, in step (ii), the heating and the sintering are carried out in different zones.

[0015] According to an embodiment of the present invention, in step (ii), the heating and the sintering are carried out at different temperatures.

[0016] According to an embodiment of the present invention, in step (ii), the lithium supplementation material is heated at the heating temperature and the cathode active material to be repaired is sintered at the sintering temperature, and wherein the heating temperature is at least 100 °C higher than the sintering temperature. Thus, a pressure difference is generated between the heating zone and the sintering zone, so that lithium ions volatilize during the high-temperature roasting process and enter the sintering zone due to the pressure difference and are embedded in the lithium-deficient layer structure of the cathode active material to repair the lattice structure.

[0017] According to an embodiment of the present invention, in step (ii), the heating of the lithium supplementation material is carried out in an atmosphere of oxygen, nitrogen or air.

[0018] According to an embodiment of the present invention, the mass ratio of the lithium supplementation material to the cathode active material to be repaired is 1:1 to 5:1.

[0019] According to an embodiment of the present invention, in step (i), after separating the positive electrode active material, the positive electrode active material is screened, and the material below 300 mesh is collected as the positive electrode active material to be repaired.

[0020] According to an embodiment of the present invention, before step (i), the method further includes the following step: heating the positive electrode plate at a temperature of 300 °C to 500 °C for at least 10 min to decompose the binder in the positive electrode plate.

[0021] According to an embodiment of the present invention, the positive electrode plate is from a used lithium battery, such as an old battery, a waste battery, a retired battery, or a lithium battery suffering from wear.

[0022] According to an embodiment of the present invention, the method further includes: (iii) performing ultrasonic vibration screening on the repaired positive electrode active material.

[0023] According to an embodiment of the present invention, the lithium supplement material includes at least one of lithium hydroxide monohydrate and lithium carbonate.

[0024] According to an embodiment of the present invention, the lithium supplement material is lithium hydroxide monohydrate, preferably lithium hydroxide monohydrate powder.

[0025] According to an embodiment of the present invention, after lithium hydroxide monohydrate is vaporized, it is embedded in the lithium-deficient positive electrode active material to be repaired as a lithium source, so that the lattice structure in the positive electrode active material to be repaired is repaired, realizing quantitative lithium supplementation and ensuring the stoichiometric ratio of the recycled product.

[0026] According to an embodiment of the present invention, by means of the method according to the present invention, the self-adaptability of the gas-phase volatilization of lithium hydroxide monohydrate is utilized, avoiding the complex steps of measuring the lithium metal content by ICP in the traditional repair process, realizing lithium supplementation and crystal reshaping at one time, simplifying the recycling process of retired lithium batteries, and the lithium distribution in the repaired positive electrode active material is uniform, thereby obtaining positive electrode active materials with excellent performance and high consistency.

[0027] According to an embodiment of the present invention, in step (ii), the lithium supplement material is heated in the heating area and the positive electrode active material to be repaired is sintered in the sintering area. The heating area and the sintering area are in different areas, and wherein the atmosphere containing the gaseous lithium source flows from the heating area to the sintering area.

[0028] According to an embodiment of the present invention, in step (ii), the heating of the lithium supplement material is carried out under a pressure of 0.1 MPa to 1 MPa.

[0029] According to an embodiment of the present invention, the positive electrode active material includes at least one of lithium transition metal oxides and lithium-containing phosphates with an olivine structure.

[0030] According to an embodiment of the present invention, the lithium transition metal oxide includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium manganese cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds;

[0031] The lithium-containing phosphate with an olivine structure includes at least one of lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their modified compounds. Brief Description of the Drawings

[0033] To make the above objects, features, and advantages of the present invention more easily understood, the following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. Many specific details are set forth in the following description to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0034] Figure 1 Schematically shows the lithium supplement device in the method according to the present invention;

[0035] Figure 2 Schematically shows the electrochemical performance of the repaired positive electrode active material obtained according to Example 1;

[0036] Figure 3 Schematically shows the electrochemical performance of the repaired positive electrode active material obtained according to Example 1;

[0037] Figure 4 Schematically shows the electrochemical performance of the repaired positive electrode active material obtained according to Comparative Example 2;

[0038] Figure 5 Schematically shows the electrochemical performance of the repaired positive electrode active material obtained according to Comparative Example 2;

[0039] Figure 6 Schematically shows the electrochemical performance of a commercially available new positive electrode active material;

[0040] Figure 7 Schematically shows the electrochemical performance of a commercially available new positive electrode active material. Detailed Description of the Embodiments

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of this application. The embodiments described herein are illustrative in nature and are provided to provide a basic understanding of this application. The embodiments of this application should not be construed as a limitation of this application. All other embodiments obtained by those skilled in the art based on the technical solutions provided in this application and the given embodiments fall within the scope of protection of this application.

[0042] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured using various common measurement methods in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0043] The list of items connected by the terms "at least one of", "at least one in", "at least one kind in" or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A or B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, or C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can include a single component or multiple components. Item B can include a single component or multiple components. Item C can include a single component or multiple components.

[0044] I. Positive electrode sheet

[0045] The materials, compositions, and manufacturing methods of the positive electrode that can be used in the embodiments of this application include the technologies disclosed in any prior art.

[0046] According to some embodiments of this application, the positive electrode includes a current collector and a positive electrode active material layer located on the current collector. According to some embodiments of this application, the positive electrode active material includes at least one of lithium transition metal oxides and lithium-containing phosphates with an olivine structure. The lithium transition metal oxides include at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium manganese cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds; the lithium-containing phosphates with an olivine structure include at least one of lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their modified compounds.

[0047] According to a preferred embodiment of the present application, the positive electrode active material includes, but is not limited to: lithium cobalt oxide (LiCoO 2 ), lithium nickel cobalt manganese (NCM) ternary material, lithium nickel cobalt aluminum (NCA) ternary material, lithium iron phosphate (LiFePO 4 ), lithium manganese iron phosphate (LiMn x Fe 1-x PO 4 ), or lithium manganese oxide (LiMn 2 O 4 ).

[0048] According to a preferred embodiment of the present application, the positive electrode active material is Li[Ni 1-x-y Co x M y O 2 (M = Mn, Al, etc., such as lithium nickel cobalt manganese oxide Li[Ni 1-x-y Co x Mn y O 2 , 1 - x - y ≥ 0.5; lithium nickel cobalt aluminate Li[Ni 1-x-y Co x Al y O 2 , 1 - x - y ≥ 0.5).

[0049] According to some embodiments of the present application, the positive electrode active material layer further includes a binder, and optionally includes a conductive material. The binder improves the binding between the positive electrode active material particles and also improves the binding between the positive electrode active material and the current collector. In some embodiments, the binder includes: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1 - difluoroethylene, polyethylene, polypropylene, styrene - butadiene rubber, acrylated styrene - butadiene rubber, epoxy resin, or nylon, etc.

[0050] According to some embodiments of the present application, the conductive material includes, but is not limited to: carbon - based materials, metal - based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon - based materials are selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal - based materials are selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0051] II. Electrochemical Device

[0052] The lithium batteries according to the present invention include lithium metal batteries, lithium ion batteries, lithium polymer batteries or lithium ion polymer batteries. In some embodiments, the lithium batteries of the present application include a positive electrode, a negative electrode, a separator and an electrolyte.

[0053] The lithium batteries according to the present invention can be applied in electronic devices, including but not limited to, laptop computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, portable cleaners, portable CD players, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries and lithium ion capacitors, etc.

[0054] III. Button half-cell

[0055] The button half-cell mentioned in the present invention is assembled through the following steps:

[0056] Using a lithium metal sheet as the counter electrode; using 1M LiPF6 / EC:DEC:DMC (1:1:1) as the electrolyte; using a polypropylene microporous membrane of Celgard 2400 model as the separator; dispersing the repaired positive electrode active material, PDVF, and conductive carbon super P in NMP according to a mass ratio of 80:10:10, stirring evenly, coating on an Al foil with a thickness of 6 μm, and placing it in a vacuum drying oven at 110 °C for vacuum drying for 2 h to make a working electrode.

[0057] All batteries are assembled in a glove box filled with Ar gas.

[0058] IV. Performance testing

[0059] Electrochemical testing

[0060] Use the battery testing equipment Land CT2001 A to conduct electrochemical performance testing, with a voltage window of 0.005V - 5.0V and an electrode sheet loading of 10 ± 0.05 g / cm 2 。The testing methods include: using the testing equipment to conduct constant current charge and discharge testing and rate performance testing on the battery at 3.0 - 4.2V (VS Li + / Li), with a 1C rate for the first cycle and a C / 5 rate for cycling.

[0061] ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer) element testing

[0062] Place a certain amount of the sample to be tested in a digestion container, add an acid digestion solution (such as hydrochloric acid, nitric acid or sulfuric acid), seal it, and then heat and digest it in a microwave digester or an oven. After digestion, transfer the digestion solution to a volumetric flask and perform the volume-fixing and shaking steps. Use an ICP-OES device to test the trace element content of the digestion solution. For liquid-phase samples such as leachate, after dilution, use an ICP-OES device to test the trace element content of the digestion solution.

[0063] Example 1

[0064] (1) Discharge and disassemble the used lithium cobalt oxide battery (theoretical specific capacity 145 mAh / g, actual specific capacity < 120 mAh / g), and separate the positive electrode plate. The positive electrode active material is lithium cobalt oxide LiCoO 2 ;

[0065] (2) Put about 500 g of the positive electrode plate obtained in step (1) into a rotary furnace, heat it at 400 °C for half an hour, and the atmosphere is air;

[0066] (3) Use ultrasonic vibration screening to separate the positive electrode active material from the aluminum foil current collector, remove the oversize material and aluminum foil. The number of meshes of the sieve is 50 and 200, and collect the powder below 200 meshes for lithium supplementation and repair;

[0067] (4) Put the powder obtained in step (3) into Figure 1 the sintering area of the volatile lithium supplementation device shown in. There is 150 g of lithium hydroxide monohydrate powder in the heating area. It is a sectional heating tube furnace, the heating area is 900 °C and the sintering area is 800 °C, sinter for 6 hours, and the atmosphere is air.

[0068] (5) Grind and ultrasonically vibrate and screen the powder in the sintering area obtained in step (4), and take the black powder below 200 meshes as the repaired positive electrode active material.

[0069] Comparative Example 1

[0070] (1) Discharge and disassemble the same used 3C lithium battery as in Example 1 (theoretical specific capacity 145 mAh / g, actual specific capacity < 120 mAh / g), and separate the positive electrode plate. The positive electrode active material is lithium cobalt oxide LiCoO 2 ;

[0071] (2) Put about 500 g of the positive electrode plate obtained in step (1) into a rotary furnace, heat it at 400 °C for half an hour, and the atmosphere is air;

[0072] (3) Separate the positive electrode active material from the aluminum foil current collector by ultrasonic vibration screening, remove the oversize materials and aluminum foil. The mesh numbers of the sieve are 50 mesh and 200 mesh, and collect the powder below 200 mesh for lithium supplementation and repair;

[0073] (4) Put the powder obtained in step (3) into the sintering area of the volatile lithium supplementation device shown in Figure 1 . The heating area of the partitioned heating tube furnace is empty. The heating area is 900 °C and the sintering area is 800 °C. Sinter for 6 hours, and the atmosphere is air.

[0074] (5) Grind and perform ultrasonic vibration screening on the powder in the sintering area obtained after sintering in step (4), and take the black powder below 200 mesh as the repaired positive electrode active material.

[0075] Comparative Example 2

[0076] (1) Discharge and disassemble the same used 3C lithium battery as in Example 1 (theoretical specific capacity 145 mAh / g, actual specific capacity <120 mAh / g), and separate the positive electrode plate. The positive electrode active material is lithium cobaltate LiCoO 2 ;

[0077] (2) Put about 500 g of the positive electrode plate obtained in step (1) into a rotary furnace and heat it at 400 °C for half an hour. The atmosphere environment is air;

[0078] (3) Separate the positive electrode active material from the aluminum foil current collector by ultrasonic vibration screening, remove the oversize materials and aluminum foil. The mesh numbers of the sieve are 50 mesh and 200 mesh, and collect the powder below 200 mesh for lithium supplementation and repair;

[0079] (4) After measuring the lithium supplementation amount by ICP, mix the powder obtained in step (3) with 75.4 g of lithium carbonate, and then put the mixture into a muffle furnace and sinter it at 800 °C for 12 hours in an air atmosphere to obtain the repaired positive electrode active material.

[0080] Perform ICP-OES elemental tests on the positive electrode active materials before and after repair in Example 1 and the positive electrode active materials after repair in Comparative Example 1 and Comparative Example 2. The relative contents of each element in the test samples are shown in Table 1.

[0081] Prepare coin half-cells using the repaired positive electrode active materials obtained in Example 1 and Comparative Examples 1-2, and test the electrochemical performance of the coin half-cells. The test results are shown in Figures 2 to 5 .

[0082] As can be seen from Table 1, excellent lithium supplementation effects are achieved according to the method of the present invention.

[0083] Table 1

[0084] Li Co Li / Co Spent lithium cobaltate 0.826 1.013 0.815 Lithium cobaltate after repair in Example 1 0.997 1.004 0.993 Lithium cobaltate after repair in Comparative Example 1 0.82 1.007 0.814 Lithium cobaltate after repair in Comparative Example 2 0.995 1.005 0.99

[0085] Furthermore, the test results show that the repaired positive electrode active material has a high initial Coulombic efficiency and cycle capacity retention rate. Figure 2 and Figure 3 show the first charge-discharge test curve (0.2C) and cycle performance (1C) of the repaired positive electrode active material in Example 1 of the present invention, Figure 4 and Figure 5 show the charge-discharge test curve (0.2C) and cycle performance (1C) of the positive electrode active material repaired by the method described in Comparative Example 2, Figure 6 and Figure 7 show the charge-discharge test curve (0.2C) and cycle performance (1C) of the commercial new lithium cobaltate positive electrode active material. Among them, the lithium cobaltate material repaired by the temperature difference-driven lithium supplementation in the method of the present invention has electrochemical properties similar to those of commercial materials, such as discharge specific capacity and cycle stability.

[0086] The first discharge capacity of the repaired positive electrode active material in Example 1 reached 147 mAh / g, while the positive electrode active material obtained by the solid-state sintering method in Comparative Example 2 only had a first discharge capacity of 142.7 mAh / g. In the rate test at 1C, the repaired positive electrode active material in Example 1 had a first discharge capacity of 139.2 mAh / g, while the positive electrode active material obtained by the solid-state sintering method in Comparative Example 2 only had a first discharge capacity of 136 mAh / g. Therefore, the repair method disclosed in this invention patent has better discharge capacity and rate performance, and can effectively simplify the repair process and reduce costs.

[0087] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those of ordinary skill in the art will recognize that some modifications and changes can be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims, and these modifications and changes also fall within the scope of protection of the present invention.

Claims

1. A method for repairing a cathode active material, characterized in that, the method comprises the following steps: (i) providing a cathode active material to be repaired, which is obtained by separating the current collector from the cathode active material in a cathode plate; (ii) heating a lithium supplement material to obtain an atmosphere containing a gaseous lithium source, and sintering the cathode active material to be repaired in the atmosphere containing the gaseous lithium source to obtain a repaired cathode active material.

2. The method according to claim 1, characterized in that, in the step (ii), at least one of the following conditions is satisfied: (a) heating the lithium supplement material to 800 to 1000 °C to obtain the gaseous lithium source; (b) the heating time is 4 to 7 hours; (c) the sintering is carried out at a temperature of 600 to 900 °C; (d) the sintering time is 6 to 12 hours.

3. The method according to claim 1, characterized in that, in the step (ii), the lithium supplement material is heated at a heating temperature and the cathode active material to be repaired is sintered at a sintering temperature, and wherein the heating temperature is at least 100 °C higher than the sintering temperature.

4. The method according to claim 1, characterized in that, in the step (ii), the heating of the lithium supplement material is carried out in an oxygen, nitrogen or air atmosphere.

5. The method according to claim 1, characterized in that, the mass ratio of the lithium supplement material to the cathode active material to be repaired is 1:1 to 5:

1.

6. The method according to claim 1, characterized in that, the lithium supplement material comprises at least one of lithium hydroxide monohydrate and lithium carbonate.

7. The method according to claim 1, characterized in that, in the step (ii), the lithium supplement material is heated in a heating zone and the cathode active material to be repaired is sintered in a sintering zone, the heating zone and the sintering zone are in different zones, and wherein the atmosphere containing the gaseous lithium source flows from the heating zone to the sintering zone.

8. The method according to claim 1, characterized in that, in the step (ii), the heating of the lithium supplement material is carried out under a pressure of 0.1 MPa to 1 MPa.

9. The method according to claim 1, characterized in that, the cathode active material comprises at least one of lithium transition metal oxides and lithium-containing phosphates with an olivine structure.

10. The method according to claim 1, characterized in that, the lithium transition metal oxides comprise at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium manganese cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their modified compounds; the lithium-containing phosphates with an olivine structure comprise at least one of lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon and their modified compounds.

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