Carbon-coated high-speed ion conductor modified cathode material and method for manufacturing the same

Abstract

This invention provides a carbon-coated high-speed ion conductor modified cathode material and a method for producing the same. [Solution] The chemical formula of the positive electrode material is Li a Ni x Co y Mn z O2·cA·dB, where 1.00≦a≦1.20, 0.00

Description

[Technical Field]

[0001] This invention relates to a carbon-coated high-speed ion conductor modified cathode material and a method for producing the same, and belongs to the field of lithium-ion battery technology. [Background technology]

[0002] Lithium-ion batteries have become an indispensable element in the 21st-century energy economy, but the most important issue for lithium-ion batteries in large-scale battery applications such as automobiles and energy storage remains safety. Volatile, flammable, and explosive organic electrolytes are the main cause of safety problems in lithium-ion batteries. Therefore, developing all-solid-state lithium-ion batteries by using solid electrolytes, which are high-speed ion conductors, instead of liquid electrolytes is an effective way to solve the battery safety problem.

[0003] Currently, solid-state batteries are not yet commercially available, so a new application of fast ion conductors has been proposed: coating the surface of the cathode material. This suppresses side reactions between the cathode material and the electrolyte, improving the safety of the battery system. This approach is currently the most researched direction, and in conventional processes, the fast ion conductor is coated and then stabilized on the surface of the cathode material by a sintering process. However, this presents a new problem. Although fast ion conductors are excellent ion-conducting materials, their low electronic conductivity means they can be considered electronic insulators, which presents challenges to simple fast ion conductor coating. [Overview of the project]

[0004] In response to the shortcomings of existing technologies, the present invention proposes a carbon-coated high-speed ion conductor modified cathode material and a method for producing the same. This method modifies the cathode material using a carbon-coated modified high-speed ion conductor, and simultaneously covers the surface of the carbon-coated high-speed ion conductor using the glassy state properties of boric acid. This effectively prevents the diffusion of carbon in the carbon-coated high-speed ion conductor, thereby achieving simultaneous improvement of the ionic conductivity and electronic conductivity of the cathode material.

[0005] The technical solution of the present invention is a carbon-coated high-speed ion conductor modified cathode material, and its general chemical formula is Li a Ni x Co y Mn z O2·cA·dB, where 1.00 ≦ a ≦ 1.20, 0.00 < c ≦ 0.01, 0.00 < d ≦ 0.02, 0.00 ≦ x < 1.00, 0.00 ≦ y < 0.2, 0.00 ≦ z < 0.4, and x + y + z = 1. A is the first coating material, B is the second coating material. The first coating material A is a carbon-coated high-speed ion conductor, and the second coating material B is a carbon diffusion prevention compound.

[0006] Preferably, the carbon diffusion prevention compound is in a glassy state, a molten state or a liquid state at 250 to 450 °C and in a solid state at normal temperature.

[0007] Preferably, the carbon diffusion prevention compound is boric acid.

[0008] Preferably, the high-speed ion conductor is LATP or LLZO.

[0009] Preferably, based on mass, the total free lithium content of the cathode material is less than 1500 ppm.

[0010] Preferably, its specific surface area is 0.5 to 1.2 m 2 / g.

[0011] Preferably, the average particle size of the cathode material is 2 to 5 μm.

[0012] The second object of the present invention is to provide a lithium ion battery cathode material, and the cathode active material includes the above-mentioned carbon-coated high-speed ion conductor modified cathode material.

[0013] The third object of the present invention is to provide a lithium ion battery including the above-mentioned lithium ion battery cathode material.

[0014] A fourth object of the present invention is to provide an electric device including the above-described lithium ion battery used for supplying electric power.

[0015] A fifth object of the present invention is to provide a method for manufacturing a carbon-coated high-speed ion conductor modified positive electrode material, the manufacturing method comprising

[0016] Step 1: Mixing a ternary positive electrode material, a carbon-coated high-speed ion conductor, and a carbon diffusion prevention compound at a mass ratio of 1.0:(0.001 to 0.02):(0.006 to 0.01), and then ball-milling;

[0017] Step 2: Placing the ball-milled material in a muffler furnace, heating it to 250 to 450°C at a heating rate of 5°C / min in an air atmosphere, and then sintering for 6 hours to obtain a carbon-coated high-speed ion conductor modified positive electrode material; [[ID=and]] including the steps.

[0018] Preferably, the carbon diffusion prevention compound is boric acid.

[0019] By adopting the above technical solutions, the advantages of the present invention are as follows.

[0020] [[ID=include]]1. By adopting a carbon-coated high-speed ion conductor modified positive electrode material, the present invention simultaneously improves the ion conductivity and electron conductivity of the positive electrode material, and improves the battery performance.

[0021] 2. By simultaneously using boric acid for coating, the present invention solves the problem of carbon diffusion in the coating process.

[0022] 3. The lithium ion battery positive electrode material according to the present invention improves the safety performance of the battery by double coating modification.

Brief Description of the Drawings

[0023] [Figure 1] It is a SEM image of a carbon-coated high-speed ion conductor modified positive electrode material in the present invention. [Figure 2] It should be noted that there is an error in the original text where "and" is used inappropriately in line . It should be "Step 2" instead. This has been corrected in the translation for better understanding.It is a DSC curve diagram of Example 2 and Comparative Example 1.

Mode for Carrying Out the Invention

[0024] In order to better understand the technical solutions of the embodiments of the present application, some preferred embodiments of the present application will be given and further described below.

[0025] In this specification, amounts, ratios, and other numerical values may be presented in a range format. Such a range format is used for convenience and brevity and should be interpreted flexibly so as to include not only the numerical values explicitly specified as the limitations of the range, but also all individual numerical values or sub-ranges included within the range as if each numerical value and sub-range were explicitly specified.

[0026] The general chemical formula of the carbon-coated high-speed ion conductor-modified cathode material proposed in the present application is Li a Ni x Co y Mn z O2·cA·dB, where 1.00 ≦ a ≦ 1.20, 0.00 < c ≦ 0.01, 0.00 < d ≦ 0.02, 0.00 ≦ x < 1.00, 0.00 ≦ y < 0.2, 0.00 ≦ z < 0.4, x + y + z = 1, A is the first coating material, B is the second coating material, the first coating material A is a carbon-coated high-speed ion conductor, and the second coating material B is a carbon diffusion prevention compound.

[0027] Preferably, the carbon diffusion prevention compound is in a glassy state, a molten state or a liquid state at 250 to 450 °C and is in a solid state at room temperature.

[0028] Preferably, the carbon diffusion prevention compound is boric acid.

[0029] Preferably, the high-speed ion conductor is LATP or LLZO.

[0030] Preferably, on a mass basis, the cathode material contains < 1500 ppm of total free lithium.

[0031] Preferably, its specific surface area is 0.5 to 1.2 m². 2 It is / g.

[0032] Preferably, the average particle size of the positive electrode material is 2 to 5 μm.

[0033] A second object of the present invention is to provide a lithium-ion battery cathode material, wherein the cathode active material includes the carbon-coated high-speed ion conductor modified cathode material described above.

[0034] A third object of the present invention is to provide a lithium-ion battery containing the lithium-ion battery cathode material described above.

[0035] A fourth object of the present invention is to provide an electrical device that includes the above-described lithium-ion battery used for supplying power.

[0036] The lithium-ion battery of the present invention comprises electrodes, a non-aqueous electrolyte, a separator, and a container. Specifically, the electrodes include a positive electrode and a negative electrode. The positive electrode is manufactured from a positive electrode current collector, a positive electrode active material coated on the positive electrode current collector, and materials such as a conventional binder and conventional conductive additives, where the positive electrode active material is the lithium-ion positive electrode material of the present invention. The negative electrode is manufactured from a current collector, a conventional negative electrode active material coated on the current collector, and materials such as a conventional binder and conventional conductive additives. The separator is a PP / PE film commonly used in this industry and is used to separate the positive and negative electrodes from each other. The container houses the positive electrode, negative electrode, separator, and electrolyte.

[0037] A fifth object of the present invention is to provide a method for producing a carbon-coated high-speed ion conductor modified cathode material, and the method for producing this material is...

[0038] Step 1: Mix the ternary cathode material, carbon-coated fast ion conductor, and carbon diffusion-preventing compound in a mass ratio of 1.0:(0.001~0.02):(0.006~0.01), then ball mill the mixture.

[0039] Step 2: Place the ball-milled material into a muffle furnace and heat it to 250-450°C in an air atmosphere at a heating rate of 5°C / min, then sinter it for 6 hours to obtain a carbon-coated high-speed ion conductor modified cathode material. This includes the following step.

[0040] Preferably, the carbon diffusion inhibitory compound is boric acid.

[0041] The carbon-coated high-speed ion conductor modified cathode material, its manufacturing method, and applications of the present invention will be described below through specific examples. Any reagents or equipment not described herein are generally verifiable by those skilled in the art.

[0042] Table 1 shows the reagents used in each of the following examples.

[0043] [Table 1]

[0044] The apparatus and analytical methods used in the following examples are as follows:

[0045] The specific surface area is analyzed and measured using a fully automated specific surface area and pore distribution analyzer (TriStar II 3020, manufactured by Micromeritics, Inc., USA).

[0046] The test method for free lithium in the cathode material is as follows:

[0047] Accurately weigh an appropriate amount of sample (m grams, approximately 30 g) to an accuracy of 0.01 g. Place the sample in a 250 mL Erlenmeyer flask, add a magnetic stirrer bar, and add 100 mL of deionized water. Place the Erlenmeyer flask on a magnetic stirrer, turn on the stirrer, and stir for 30 minutes. Filter the mixed solution through filter paper and a funnel. Take 50 mL of filtrate with a 50 mL pipette, place it in a 100 mL beaker, and add a magnetic stirrer bar. Place the beaker on a magnetic stirrer and add 2 drops of phenolphthalein indicator. Titrate with 0.05 mol / L hydrochloric acid standard titration solution until the solution changes color from red to colorless. Record the volume V1 (endpoint 1) of the 0.05 mol / L hydrochloric acid standard titration solution. Adding 2 drops of methyl red indicator will change the color from colorless to yellow. Titrate the solution with 0.05 mol / L hydrochloric acid standard titration solution until the color changes from yellow to orange. Place the beaker in a heating furnace and heat until the solution boils (the color of the solution changes from orange to yellow). Remove the 100 mL beaker and allow it to cool to room temperature. Place the beaker back in a magnetic stirrer and titrate with 0.05 mol / L hydrochloric acid standard titration solution until the color changes from yellow to pale red, and record the volume V2 (endpoint 2) of the 0.05 mol / L hydrochloric acid standard titration solution.

[0048] Lithium hydroxide: LiOH (wt%) = [V2 - 2 × (V2 - V1)] × 0.05 × 23.946 × 2 × 100 / (m × 1000)

[0049] Lithium carbonate: Li2CO3 (wt%) = (V2 - V1) × 0.05 × 73.886 × 2 × 100 / (m × 1000)

[0050] Free lithium: Li + (wt%)=V2×0.05×6.94×2×100 / (m×1000)

[0051] m: sample mass in grams, V1: first titration endpoint, V2: second titration endpoint.

[0052] Measurement of average particle size: Measurement was performed using an MS3000 laser particle size analyzer, and the method was as follows.

[0053] Take an appropriate amount of sample into a 100ml beaker. First, rinse the inner wall of the beaker with a washing bottle, then rinse any sample adhering to the bottom of the beaker with the same washing bottle. Adjust the amount of pure water added to the beaker to 20-30ml, and set the sonication time to 5min (stir for 10s before, during, and after sonication, with a stirring speed of approximately 2r / s). Add 100±10ml of pure water to the MS3000 laser particle size analyzer sampler, adjust the rotation speed to 3000r / min, and click "Start". The instrument will automatically perform optical axis alignment and background measurement. Wait for instructions before operating. Transfer the sample after sonication to the stirring tank, and further rinse the beaker with a washing bottle to ensure all the sample has been transferred. Once the sample is completely added, the software will automatically start the measurement. After the measurement is complete, the data will be automatically saved.

[0054] DSC test method: The test is performed using STA449F3, with a heating rate of 10°C / min, a final temperature of 400°C, and under a nitrogen atmosphere.

[0055] Resistivity test: Using a Suzhou Crystal ST-2255, the resistivity was tested at a pressure of 50 MPa with a sample volume of 5 g.

[0056] In the following embodiments, the method for manufacturing a complete battery (cell model 454261) using the positive electrode material manufactured according to the present invention is as follows.

[0057] Manufacturing of the positive electrode: The positive electrode material of the present invention, conductive carbon black (SP), and polyvinylidene fluoride (PVDF) as a binder are added to N-methylpyrrolidone (NMP) in a weight ratio of 94:3:3 (the weight ratio of positive electrode material to NMP is 2.1:1), thoroughly mixed to form a uniform slurry, applied to an aluminum foil current collector, dried, and pressed onto an electrode sheet.

[0058] Negative electrode manufacturing: Negative electrode artificial graphite, conductive carbon black (SP), carboxymethylcellulose (CMC), and adhesive (SBR) are added to sufficient pure water in a weight ratio of 95:1:1:3, mixed to form a uniform slurry, applied to a copper foil current collector, dried, and pressed onto an electrode sheet.

[0059] The separator is a PP / PE / PP three-layer composite film material.

[0060] Tabs are spot-welded to the pressed positive and negative electrode sheets, a separator is inserted, the sheets are wound on a winding machine, loaded into a soft pack jig, the top and sides are sealed, and then baked in an oven. Subsequently, 9g of electrolyte is injected in an environment with a relative humidity of less than 1.5%, followed by a 48-hour chemical conversion (Zhejiang Hangke LIP-3AHB06 high constant temperature chemical conversion system), after which the sheets are vacuumed and sealed.

[0061] For drying samples and high-temperature testing of batteries, a KPBAK-03E-02 high-efficiency vacuum drying box manufactured by Dongguan Kerui Electromechanical Co., Ltd. is used.

[0062] The charge-discharge tests of the lithium-ion secondary batteries manufactured according to this invention will be conducted using the Wuhan Blue-Electric battery testing apparatus (Wuhan Blue-Electric CT2001C test apparatus) in accordance with the GB / T18287-2000 test method. Different battery systems significantly affect the cycle retention rate of the materials. The battery system used in this experiment is the most common evaluation system, namely, a 1 mol / L lithium hexafluoride phosphate solution as the electrolyte, with the solvent being a mixed solvent of dimethyl carbonate (DMC):ethylene carbonate (EC):diethyl carbonate (DEC) in a mass ratio of 1:1:1, and the negative electrode material being a mixture of artificial graphite, conductive carbon black, carboxymethylcellulose, and adhesive in a weight ratio of 95:1:1:3, with the cell model being 454261. This allows for the rapid exposure of actual defects in the positive electrode material and the determination of its performance.

[0063] Example 1 LiRing 0.5 Co 0.2 Mn 0.3O2 was selected as the base material, and corresponding amounts of carbon-coated LLZO and boric acid were weighed and added to the base material so that the mass ratio of base material:carbon-coated LLZO:boric acid was 1.0:0.01:0.008. The mixture was then milled in a ball mill at a rotation speed of 40 Hz for 10 minutes. The uniformly mixed material was placed in a muffle furnace and heated to 450°C at a heating rate of 5°C / min under an air atmosphere, then sintered for 6 hours, cooled to room temperature, and sieved through a 300-mesh metal sieve to obtain cathode material 1.

[0064] Particle size, specific surface area, free lithium, and battery tests were performed on this positive electrode material 1, and the data are shown in Table 2.

[0065] Example 2 LiRing 0.6 Co 0.1 Mn 0.3 O2 was selected as the base material, and corresponding amounts of carbon-coated LATP and boric acid were weighed and added to the base material so that the mass ratio of base material:carbon-coated LATP:boric acid was 1.0:0.02:0.01. The mixture was then milled in a ball mill at a rotation speed of 40 Hz for 10 minutes. The uniformly mixed material was placed in a muffle furnace and heated to 410°C in an air atmosphere at a heating rate of 5°C / min, then sintered for 6 hours, cooled to room temperature, and sieved through a 300-mesh metal sieve to obtain cathode material 2.

[0066] Particle size, specific surface area, free lithium, and battery tests were performed on this positive electrode material 2, and the data are shown in Table 2.

[0067] Example 3 LiRing 0.7 Co 0.1 Mn 0.2 O2 was selected as the base material, and corresponding amounts of carbon-coated LATP and boric acid were weighed and added to the base material so that the mass ratio of base material:carbon-coated LLZO:boric acid was 1.0:0.005:0.007. The mixture was then milled in a ball mill at a rotation speed of 40 Hz for 10 minutes. The uniformly mixed material was placed in a muffle furnace and heated to 370°C in an air atmosphere at a heating rate of 5°C / min, then sintered for 6 hours, cooled to room temperature, and sieved through a 300-mesh metal sieve to obtain cathode material 3.

[0068] Particle size, specific surface area, free lithium, and battery tests were conducted on this positive electrode material 3, and the data are shown in Table 2.

[0069] Example 4 LiRing 0.83 Co 0.07 Mn 0.1 O2 was selected as the base material, and corresponding amounts of carbon-coated LATP and boric acid were weighed and added to the base material so that the mass ratio of base material:carbon-coated LATP:boric acid was 1.0:0.001:0.008. The mixture was then milled in a ball mill at a rotation speed of 40 Hz for 10 minutes. The uniformly mixed material was placed in a muffle furnace and heated to 320°C in an air atmosphere at a heating rate of 5°C / min, then sintered for 6 hours, cooled to room temperature, and sieved through a 300-mesh metal sieve to obtain cathode material 4.

[0070] Particle size, specific surface area, free lithium, and battery tests were performed on this positive electrode material 4, and the data are shown in Table 2.

[0071] Example 5 LiRing 0.92 Co 0.05 Mn 0.03 O2 was selected as the base material, and corresponding amounts of carbon-coated LATP and boric acid were weighed and added to the base material so that the mass ratio of base material:carbon-coated LATP:boric acid was 1.0:0.008:0.006. The mixture was then milled in a ball mill at a rotation speed of 40 Hz for 10 minutes. The uniformly mixed material was placed in a muffle furnace and heated to 250°C in an air atmosphere at a heating rate of 5°C / min, then sintered for 6 hours, cooled to room temperature, and sieved through a 300-mesh metal sieve to obtain cathode material 5.

[0072] For this positive electrode material 5, particle size, specific surface area, free lithium, and battery tests were conducted, and the data are shown in Table 2.

[0073] Comparative Example 1 LiRing 0.6 Co 0.1 Mn 0.3O2 was selected as the base material, and the corresponding amount of LATP was weighed and added to the base material so that the mass ratio of base material to LATP was 1.0:0.02. Ball milling was performed at a rotation speed of 40 Hz for 10 minutes. The uniformly mixed material was placed in a muffle furnace and heated to 400°C in an air atmosphere at a heating rate of 5°C / min, then sintered for 6 hours, cooled to room temperature, and sieved through a 300-mesh metal sieve to obtain the control cathode material D1.

[0074] Particle size, specific surface area, free lithium, and battery tests were performed on this control cathode material D1, and the data are shown in Table 2.

[0075] [Table 2]

[0076] Table 2 shows that the cathode materials produced in the embodiments of the present invention have a total free lithium content of less than 1500 ppm and a specific surface area of ​​0.6 to 1.0 m². 2 The values ​​are between / g and the particle size is between 3.0 and 5.0 μm.

[0077] Currently, safety issues with lithium batteries are frequent, mainly caused by side reactions in the electrolyte. Since solid-state batteries are difficult to commercialize in the short term, it is necessary to improve the interface of the cathode material. This includes coatings such as metal oxides and anionic salts, but these coatings reduce the ionic conductivity of the cathode material to some extent. To avoid reducing ionic conductivity while coating, researchers are focusing on using only fast ion conductors as coating agents, but coating with fast ion conductors reduces the electronic conductivity of the cathode material. To solve the above problems, this invention modifies the cathode material using a carbon-coated modified fast ion conductor, achieving simultaneous improvement of the ionic conductivity and electronic conductivity of the cathode material, and at the same time, by covering the surface of the carbon-coated fast ion conductor using the glassy state properties of boric acid, the diffusion of carbon in the carbon-coated fast ion conductor is effectively prevented.

[0078] As can be seen from Table 2, in the examples, when the Ni mole fraction was 0.6, using a carbon-coated fast ion conductor resulted in a rise of approximately 10°C in the DSC peak of the cathode material, a dramatic decrease in powder resistivity, and a significant improvement in electronic conductivity and safety compared to simply using a fast ion conductor.

[0079] Based on the above, the positive electrode material of the present invention achieves simultaneous improvement of the ionic conductivity and electronic conductivity of the positive electrode material, thereby improving the safety of the battery.

Claims

1. The general chemical formula is Li a Ni x Co y Mn z O 2 A carbon-coated fast ion conductor modified cathode material characterized by the following: cA・dB, where 1.00≦a≦1.20, 0.00<c≦0.01, 0.00<d≦0.02, 0.00≦x<1.00, 0.00≦y<0.2, 0.00≦z<0.4, x+y+z=1, A is a first coating material, B is a second coating material, the first coating material A is a carbon-coated fast ion conductor, and the second coating material B is a carbon diffusion-preventing compound.

2. The carbon-coated high-speed ion conductor modified cathode material according to claim 1, characterized in that the carbon diffusion-preventing compound is in a glassy, ​​molten, or liquid state at 250 to 450°C and in a solid state at room temperature.

3. The carbon-coated high-speed ion conductor modified cathode material according to claim 2, characterized in that the carbon diffusion-preventing compound is boric acid.

4. The carbon-coated high-speed ion conductor modified cathode material according to claim 1, characterized in that the high-speed ion conductor is LATP or LLZO.

5. The carbon-coated high-speed ion conductor modified cathode material according to any one of claims 1 to 4, characterized in that the total free lithium content of the cathode material is less than 1500 ppm by mass.

6. Its specific surface area is 0.5 to 1.2 m². 2 The carbon-coated high-speed ion conductor modified cathode material according to claim 5, characterized in that it is / g.

7. The carbon-coated high-speed ion conductor modified cathode material according to claim 6, characterized in that its average particle size is 2 to 5 μm.

8. A lithium-ion battery cathode material characterized by comprising the carbon-coated high-speed ion conductor modified cathode material described in any one of claims 1 to 7.

9. A lithium-ion battery characterized by comprising the lithium-ion battery cathode material described in claim 8.

10. An electrical device characterized by comprising a lithium-ion battery according to claim 9, used for supplying power.

11. Step 1: Mix the ternary cathode material, carbon-coated high-speed ion conductor, and carbon diffusion-preventing compound in a mass ratio of 1.0:(0.001-0.02):(0.006-0.01), then ball mill the mixture. Step 2: Place the ball-milled material into a muffle furnace and heat it to 250-450°C in an air atmosphere at a heating rate of 5°C / min, then sinter it for 6 hours to obtain a carbon-coated high-speed ion conductor modified cathode material. A method for producing a carbon-coated high-speed ion conductor modified cathode material, characterized by including the following step.

12. The carbon-coated high-speed ion conductor modified cathode material according to claim 11, characterized in that the carbon diffusion-preventing compound is boric acid.

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