A composite lithium-rich manganese-based positive electrode material, a preparation method and application thereof

Abstract

The present application relates to the technical field of lithium ion batteries, and particularly relates to a composite lithium-rich manganese-based positive electrode material, a preparation method and application thereof.The composite lithium-rich manganese-based positive electrode material has a three-layer structure, and from inside to outside, the three-layer structure is a lithium-rich manganese-based oxide positive electrode material matrix, a first coating layer and a second coating layer; the first coating layer is a mixture of a halide solid-state electrolyte and a lithium-containing oxide; and the second coating layer is an oxide solid-state electrolyte.The composite lithium-rich manganese-based positive electrode material can improve the electrical conductivity of the contact interface with the positive electrode material, reduce the resistance, inhibit the hygroscopic degradation of the halide, reduce the difficulty of packaging, and improve the cycle performance after the halide solid-state electrolyte absorbs moisture.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a composite lithium-rich manganese-based cathode material, its preparation method, and its application. Background Technology

[0002] Current liquid lithium-ion batteries are limited by the flammability of organic electrolytes and energy density bottlenecks, making it difficult to meet the requirements for high energy density. Solid-state batteries, which use solid electrodes and solid electrolytes to replace traditional liquid electrolytes, have high energy density (300–450 Wh / kg) and high safety, and are considered the core direction of next-generation power batteries, with applications in electric vehicles, energy storage systems, and other fields.

[0003] In solid-state batteries, the cathode material contributes significantly to capacity. Lithium-rich manganese-based cathode materials possess unique non-bonded oxygen states in their band structure. During charge and discharge, both anions and cations participate in charge compensation, undergoing a dual-band redox reaction and achieving multi-electron transfer. This novel reaction mechanism endows lithium-rich manganese-based cathode materials with a specific capacity as high as 300 mAh / g, and is considered the next-generation cathode material with the greatest scientific research value and application prospects.

[0004] However, lithium-rich manganese-based cathode materials have the following differences:

[0005] ① Compared with ternary cathode materials and lithium cobalt oxide, lithium-rich manganese-based cathode materials have lower ionic conductivity. If they are directly mixed and pressed with solid electrolyte during battery preparation, the contact interface impedance between lithium-rich manganese-based cathode materials and solid electrolyte will be high, resulting in poor electron transport and affecting rate performance.

[0006] ②Oxide solid electrolytes have good stability, but poor ionic conductivity; while single halide electrolytes and sulfide electrolytes have high ionic conductivity, but they are unstable in humid air, are prone to deliquescence, which reduces ionic conductivity, and are difficult to form films after deliquescence.

[0007] ③ Some electrolytes, such as halide electrolytes, are structurally unstable under high voltage, which affects their cycling performance under high voltage.

[0008] Therefore, it is particularly important to develop a composite lithium-rich manganese-based cathode material that can effectively reduce the interfacial impedance between the solid electrolyte and the lithium-rich manganese-based cathode material at high voltage and has a stable structure for use in solid-state batteries. Summary of the Invention

[0009] The purpose of this invention is to provide a composite lithium-rich manganese-based cathode material, its preparation method, and its application, in order to solve the problems of high interfacial impedance and low structural stability of some solid electrolytes when contacting solid electrolytes with lithium-rich manganese-based cathode materials under high voltage.

[0010] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0011] This invention provides a composite lithium-rich manganese-based cathode material, which has a three-layer structure, consisting of a lithium-rich manganese-based oxide cathode material matrix, a first coating layer, and a second coating layer from the inside out.

[0012] The first coating layer is a mixture of a halide solid electrolyte and a lithium oxide-containing electrolyte; the second coating layer is an oxide solid electrolyte.

[0013] Optionally, the halide solid electrolyte includes Li3YCl6, Li3InCl6, Li6PS5Cl, and Li 0.388 Ta 0.238 La 0.475 Cl3, LiAlOCl, Li 3-x Sc 1-x Zr x Cl6 and Li3ZrCl4O 1.5 One or more of them;

[0014] The lithium-containing oxide includes one or more of LiAlO2, LiNbO3 and Li2ZrO3;

[0015] The oxide solid electrolyte includes one or more of the following: garnet-type oxide solid electrolyte, NASICON-type oxide solid electrolyte, NASICON-type oxide solid electrolyte, perovskite-type oxide solid electrolyte, LiPON-type oxide solid electrolyte, and anti-perovskite-type oxide solid electrolyte.

[0016] Optionally, the lithium-rich manganese-based oxide cathode material matrix is ​​a single crystal; and / or the lithium-rich manganese-based oxide cathode material matrix contains halogens.

[0017] Optionally, the lithium-rich manganese-based oxide cathode material matrix is ​​Li. x Mn y Me 1-y O a Q b Me is selected from at least one of Ni, Co, Nb, Mo, Ti, Zr, Mg, W and Al, Q is selected from at least one of F, Cl and Br, and 1.05≤x≤1.4, 0.5≤y≤1, 1.6≤a+2b≤2.5, and 0<b≤0.4.

[0018] Optionally, the mass ratio of the halide solid electrolyte to the lithium oxide in the first coating layer is 1:1 to 4;

[0019] The mass of the first coating layer is 0.1 wt% to 5 wt% of the mass of the lithium-rich manganese-based oxide cathode material matrix;

[0020] The mass of the second coating layer is 0.1 wt% to 5 wt% of the mass of the lithium-rich manganese-based oxide cathode material matrix.

[0021] Optionally, the average particle size D50 of the lithium-rich manganese-based oxide cathode material matrix is ​​1.0 μm to 4.0 μm;

[0022] The average particle size D50 of the first coating layer is 10 nm to 50 nm;

[0023] The average particle size D50 of the second coating layer is 60 nm to 100 nm;

[0024] The average particle size D50 of the composite lithium-rich manganese-based cathode material is 1.1 μm to 4.3 μm, and the particle size distribution of the composite lithium-rich manganese-based cathode material spans from 1 to 4.

[0025] This invention also provides a method for preparing the above-mentioned composite lithium-rich manganese-based cathode material, comprising the following steps:

[0026] 1) A slurry is prepared by mixing a halide solid electrolyte and a lithium oxide-containing compound, and then adding a solvent;

[0027] 2) Mix the lithium-rich manganese-based oxide cathode material matrix and slurry, perform wet coating, dry, and perform third sintering to obtain a composite lithium-rich manganese-based cathode material intermediate;

[0028] 3) In an anhydrous environment, the composite lithium-rich manganese-based cathode material intermediate is mixed with the oxide solid electrolyte and subjected to multi-stage mixing, dilution and coating to obtain the composite lithium-rich manganese-based cathode material.

[0029] The solvent in step 1) includes one or more of the following: anhydrous ethanol, anhydrous propanol, anhydrous isobutanol, n-butyl ether, cyclopentyl methyl ether, anisole, isopropyl ether, trichloroethylene, carbon tetrachloride, toluene, chlorobenzene, cyclohexane, methylcyclohexane, and tetrahydrofuran.

[0030] In step 2), the heating rate during the third sintering is 5℃ / min to 15℃ / min, and the temperature is raised to 200℃ to 250℃, and held for 2h to 4h.

[0031] Optionally, the preparation method of the lithium-rich manganese-based oxide cathode material matrix includes the following steps:

[0032] 1) A metal salt solution containing manganese ions and halide ions, a precipitant, and a complexing agent are passed into the bottom liquid to carry out a coprecipitation reaction to obtain a precursor; during the coprecipitation reaction, the mother liquor is discharged, and the discharge rate of the mother liquor is consistent with the total inflow rate.

[0033] 2) The precursor is subjected to a first sintering to obtain manganese oxide;

[0034] 3) After cooling the manganese oxide, mix it with the lithium source and perform a second sintering to obtain a lithium-rich manganese-based oxide cathode material matrix.

[0035] The present invention also provides a lithium-ion battery comprising the above-mentioned composite lithium-rich manganese-based cathode material.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This invention provides a three-layer composite lithium-rich manganese-based cathode material, comprising, from the inside out, a lithium-rich manganese-based oxide cathode material matrix, a halide solid electrolyte and a mixture of lithium oxides, and an oxide solid electrolyte. When the halide solid electrolyte and lithium oxides are mixed and coated on the surface of the cathode material, the high ionic conductivity of the halide and the structural stability of the lithium oxides under high voltage improve the conductivity and reduce the resistance at the interface with the cathode material. The oxide solid electrolyte, coated on the surface of the oxide and halide solid electrolyte materials, has strong chemical stability and is not easily reacted with air or lithium metal. It can effectively isolate moisture in the air from hydrolysis side reactions with the halide solid electrolyte, reducing the difficulty of packaging. In addition, it has excellent thermal stability, a wide electrochemical window, and is suitable for high-voltage cathode materials.

[0038] This invention also provides a method for preparing composite lithium-rich manganese-based cathode materials. Halide solid electrolytes are sensitive to moisture in the air, and the mixture of halide solid electrolytes and lithium oxides has a relatively small particle size, easily forming loose aggregates. Ordinary dry mixing methods are difficult to achieve uniform coating. This invention uses a non-aqueous solvent to wet-coat the mixture of halide solid electrolytes and lithium oxides, followed by drying and sintering. This allows for control of the coating uniformity of the first coating layer and increases the number and density of contact points between the substances in the first coating layer and the cathode material surface. Oxide solid electrolytes are stable but have a relatively large particle size. Uniform coating can be achieved through dry multi-stage mixing and dilution coating in a non-aqueous environment, shortening the process steps and saving costs. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of the composite lithium-rich manganese-based cathode material of the present invention;

[0040] Figure 2 This is a flowchart of the preparation method of the composite lithium-rich manganese-based cathode material of the present invention. Detailed Implementation

[0041] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0042] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0043] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0044] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0045] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0046] All raw materials used in this invention can be obtained commercially or prepared using existing technologies.

[0047] This invention provides a composite lithium-rich manganese-based cathode material, which has a three-layer structure, consisting of a lithium-rich manganese-based oxide cathode material matrix, a first coating layer, and a second coating layer from the inside out.

[0048] The first coating layer is a mixture of a halide solid electrolyte and a lithium oxide-containing electrolyte; the second coating layer is an oxide solid electrolyte.

[0049] The theoretical specific capacity of the lithium-rich manganese-based battery of this invention is higher than that of ternary batteries, and it can significantly improve the capacity performance of solid-state batteries at high voltages. By using a mixed coating of halide electrolyte and lithium oxide in the first coating layer, the lithium-ion transport path can be optimized, the interfacial impedance between the lithium-rich manganese-based cathode material and the composite electrolyte can be improved, and interfacial side reactions caused by the halide electrolyte (such as hygroscopic deliquescence, irreversible oxidation of some oxygen anions, and dissolution of transition metals) can be significantly suppressed; thus improving rate performance and cycle performance. The second coating layer, an oxide solid electrolyte, is chemically stable and coats the surface of the oxide and halide solid electrolyte materials. It is not easily reacted with air or lithium metal, further effectively isolating moisture in the air from hydrolysis side reactions with the halide solid electrolyte, reducing packaging difficulty; and improving rate performance and cycle performance.

[0050] In this invention, the halide solid electrolyte includes Li3YCl6, Li3InCl6, Li6PS5Cl, and Li 0.388 Ta 0.238 La 0.475 Cl3, LiAlOCl, Li 3-x Sc 1-x Zr x Cl6 and Li3ZrCl4O 1.5 One or more of the following; preferably Li3YCl6, Li3InCl6, Li6PS5Cl, Li 0.388 Ta 0.238 La 0.475 Cl3, LiAlOCl and Li 3-x Sc 1-x Zr x One or more of Cl6, more preferably Li3YCl6, Li3InCl6 and Li 3-x Sc 1-x Zr x One or more of Cl6; in the embodiments of the present invention, Li is preferred. 2.8 Sc 0.8 Zr 0.2 Cl6 and Li3InCl6;

[0051] The lithium oxide includes one or more of LiAlO2, LiNbO3 and Li2ZrO3; in the embodiments of the present invention, LiNbO3 and LiAlO2 are preferred.

[0052] In solid-state batteries, coating secondary particles of the cathode with lithium oxides (such as LiAlO2, LiNbO3, and Li2ZrO3) can significantly suppress interfacial side reactions and optimize lithium-ion transport pathways: LiAlO2 accelerates lithium-ion migration through oxygen vacancy regulation, LiNbO3's high oxidation stability (>4.5V) prevents direct contact between the electrolyte and the cathode, reducing lattice oxygen loss, while Li2ZrO3's high mechanical strength (>150GPa) alleviates volume expansion and inhibits crack propagation, thus increasing cycle life to over 1000 cycles. Furthermore, these oxide coatings can also isolate air and moisture, maintaining ionic conductivity stability (decreased by <10%). Halide electrolytes can achieve ionic conductivity of up to 1 at room temperature. -8 The electrolyte has a flow rate close to that of liquid electrolytes (mS / cm) and a wide electrochemical window (>4.5V), making it suitable for high-voltage cathode materials such as lithium-rich manganese-based materials. However, its hygroscopicity is a major drawback. When exposed to environments with humidity >30%, it is prone to hydrolysis (e.g., Li3YCl6 → LiOH + LiCl, Li3InCl6 initially forms crystalline hydrates upon exposure to air, then some decomposes further to produce InCl3 and LiCl, with InCl3 continuing to hydrolyze and eventually forming In2O3 impurities). This results in a sharp drop in ionic conductivity (retention rate of only 0.8% after humidity exposure) and structural damage, requiring synthesis and encapsulation in a dry environment throughout the process. When halide solid electrolytes are mixed with lithium oxides and coated onto the surface of secondary particles of the cathode material, the high ionic conductivity of the halides and the structural stability of the lithium oxides under high voltage enhance the conductivity at the interface with the cathode material, thereby reducing resistance.

[0053] In this invention, the oxide solid electrolyte includes one or more of the following: garnet-type oxide solid electrolyte, NASICON-type oxide solid electrolyte, NASICON-type oxide solid electrolyte, perovskite-type oxide solid electrolyte, LiPON-type oxide solid electrolyte, and anti-perovskite-type oxide solid electrolyte.

[0054] For example, it can be one or more of the following: garnet-type LLZO, garnet-type LLZTO, NASICON-type LATP, NASICON-type LAGP, perovskite-type LLTO, LiPON-type LiPON, and anti-perovskite-type Li3OCl.

[0055] In embodiments of the present invention, the oxide solid electrolyte is preferably Li7La3Zr2O. 12 Or Na3ZrSnSi2PO4.

[0056] In this invention, the oxide solid electrolyte is coated on the surface of the oxide and halide solid electrolyte materials. It has strong chemical stability and is not easy to react with air or lithium metal. It can further effectively isolate the moisture in the air from the hydrolysis side reaction of the halide solid electrolyte, which can reduce the packaging difficulty. In addition, it has excellent thermal stability (withstands high temperature of 1000℃) and a wide electrochemical window (>4.5V), making it suitable for high voltage cathode materials.

[0057] In this invention, the lithium-rich manganese-based oxide cathode material matrix is ​​a single crystal; and / or the lithium-rich manganese-based oxide cathode material matrix contains halogens.

[0058] Preferably, the lithium-rich manganese-based oxide cathode material matrix is ​​Li. x Mn y Me 1-y O a Q b Me is selected from at least one of Ni, Co, Nb, Mo, Ti, Zr, Mg, W and Al, Q is selected from at least one of F, Cl and Br, and 1.05≤x≤1.4, 0.5≤y≤1, 1.6≤a+2b≤2.5, 0<b≤0.4;

[0059] More preferably, x can be any value between 1.05≤x≤1.1, 1.1≤x≤1.2, 1.2≤x≤1.3, 1.3≤x≤1.4, or 1.05≤x≤1.4; y can be any value between 0.5≤y≤0.6, 0.6≤y≤0.7, 0.7≤y≤0.8, 0.8≤y≤0.9, 0.9≤y≤1, or 0.5≤y≤1; and a+b can be any value between 1.6≤a+b≤1.7, 1.7≤a+b≤1.8, and 1.9≤1.9. 1.8, 1.8≤a+b≤1.9, 1.9≤a+b≤2.0, 2.0≤a+b≤2.1, 2.1≤a+b≤2.2, 2.2≤a+b≤2.3, 2.3≤a+b≤2.4, 2.4≤a+b≤2.5, or 1.6≤a+b≤2.5; b can be any value between 0<b≤0.1, 0.1<b≤0.2, 0.2<b≤0.3, 0.3<b≤0.4, or 0<b≤0.4.

[0060] In this invention, the lithium-rich manganese-based oxide cathode material matrix is ​​single-crystal; the theoretical specific capacity of the lithium-rich manganese-based cathode material is high, far exceeding that of traditional ternary materials; and the high manganese content can significantly reduce dependence on cobalt and nickel; the structure is stable at high temperatures, and the cycle life at conventional voltage (4.6V) is good; compared with polycrystalline materials, the single-crystal lithium-rich manganese-based cathode material, with its complete structure that eliminates grain boundary defects, uniform lithium-ion diffusion channels, and high tap density characteristics, achieves synergistic optimization of specific capacity and cycle stability by fully activating redox reactions, increasing volumetric energy density, and suppressing lattice distortion and side reactions during cycling. Doping with halogens can improve the above conditions, enhance the rate capability and cycle stability of the lithium-rich manganese-based material, and increase its adaptability to all-solid-state systems.

[0061] In this invention, the mass ratio of the halide solid electrolyte to the lithium oxide in the first coating layer is 1:1 to 4, for example, it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4, etc.

[0062] A high proportion of halide solid electrolyte (e.g., >50%) will lead to insufficient battery capacity (due to the low capacity of halide itself), while a low proportion (e.g., <20%) will make it difficult to form a continuous lithium conduction channel, resulting in increased solid solution difficulty and decreased cycle stability.

[0063] The mass of the first coating layer is 0.1wt% to 5wt% of the mass of the lithium-rich manganese-based oxide cathode material matrix, for example, it can be 0.1wt%, 0.3wt%, 0.5wt%, 0.7wt%, 1wt%, 2wt%, 3wt%, 4wt%, or 5wt%, etc.

[0064] The mass of the second coating layer is 0.1wt% to 5wt% of the mass of the lithium-rich manganese-based oxide cathode material matrix, for example, it can be 0.1wt%, 0.3wt%, 0.5wt%, 0.7wt%, 1wt%, 2wt%, 3wt%, 4wt%, or 5wt%.

[0065] In this invention, the content of the first coating layer and the second coating layer should meet the coating requirements while minimizing capacity loss.

[0066] In this invention, the average particle size D50 of the lithium-rich manganese-based oxide cathode material matrix is ​​1.0 μm to 4.0 μm, for example, it can be 1.5 μm, 1.64 μm, 2 μm, 2.5 μm, 3 μm or 4 μm, etc.

[0067] The average particle size D50 of the first coating layer is 10nm to 50nm, for example, it can be 10nm, 15nm, 20nm, 26nm, 30nm, 35nm, 40nm, 45nm or 50nm, etc.

[0068] The average particle size D50 of the second coating layer is 60nm to 100nm, for example, it can be 60nm, 65nm, 69nm, 75nm, 80nm, 85nm, 90nm, 95nm or 100nm, etc.

[0069] In this invention, the first coating layer has smaller particle size and a larger specific surface area, which optimizes the contact points and density with the cathode material interface, alleviates anisotropic strain, shortens the lithium-ion diffusion path, improves interfacial resistance, and enhances the bonding strength with the substrate. The second coating layer has slightly larger particle size, forming a continuous protective layer to isolate moisture and oxygen corrosion, improves interfacial stability, and balances mechanical strength and ion / electron transport requirements. Both work synergistically to achieve stress relief, improved interfacial stability, and enhanced electrochemical performance. If the second coating layer has a small particle size, its mechanical strength is low, reducing structural stability; if the first coating layer has an excessively large particle size, a larger coating amount is required, or it may be impossible to coat most of the secondary cathode material particle surface / first coating layer surface.

[0070] The average particle size D50 of the composite lithium-rich manganese-based cathode material is 1.1 μm to 4.3 μm, for example, it can be 1.1 μm, 1.2 μm, 1.3 μm, 1.5 μm, 1.7 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.2 μm or 4.3 μm, etc.;

[0071] The small particle size of single-crystal lithium-rich manganese-based cathode materials results in a short lithium-ion diffusion channel, which is beneficial for lithium-ion insertion and extraction, thereby improving capacity performance. If the particle size of the single crystal is too small, overheating may lead to lattice defects and affect cycle life. If the particle size of the single crystal is too large, the lithium-ion diffusion path is too long, which affects capacity performance.

[0072] In this invention, the particle size distribution span of the composite lithium-rich manganese-based cathode material, Span = (D90-D10) / D50, is 1 to 4, for example, it can be 1, 1.2, 1.5, 1.9, 2, 2.2, 2.8, 3, 3.5 or 4.

[0073] This invention also provides a method for preparing the above-mentioned composite lithium-rich manganese-based cathode material, comprising the following steps:

[0074] 1) A slurry is prepared by mixing and crushing a halide solid electrolyte and a lithium oxide-containing compound, and then adding a solvent;

[0075] 2) Mix the lithium-rich manganese-based oxide cathode material matrix and slurry, perform wet coating, dry, and perform third sintering to obtain a composite lithium-rich manganese-based cathode material intermediate;

[0076] 3) In an anhydrous environment, the composite lithium-rich manganese-based cathode material intermediate is mixed with the crushed oxide solid electrolyte and subjected to multi-stage mixing, dilution and coating to obtain the composite lithium-rich manganese-based cathode material.

[0077] Step 1) involves mixing and crushing the halide solid electrolyte and lithium oxide, sieving them, and then adding a solvent to mix and obtain a slurry.

[0078] The crushing in step 1) is ball milling. The ball milling method for the mixture of halide electrolyte and lithium oxide is as follows: After mixing the halide electrolyte and the lithium oxide, place them in a zirconia crucible. Mix large zirconia balls (8mm in diameter), medium balls (5mm in diameter), and small balls (1mm in diameter) at a mass ratio of 1:(1-3):(1-3), for example, 1:1:1, 1:1:2, or 1:1:3, etc., to form mixed zirconia balls at a ball-to-material mass ratio of approximately 1:(0.5-1.5), for example, 1:0.5, 1:1, or 1:1.5, etc. Weigh the mixed zirconia balls and add them to a ball mill jar for ball milling. Set the ball milling speed to 300 r / min to 500 r / min, for example, 300 r / min. 350 r / min, 400 r / min, 450 r / min or 500 r / min; forward rotation for 15 to 30 min, for example, 15 min, 18 min, 20 min, 25 min, 28 min or 30 min; intervals of 30 min to 40 min, for example, 30 min, 32 min, 34 min, 36 min, 38 min or 40 min; reverse rotation for 15 min to 30 min, for example, 15 min, 18 min, 20 min, 25 min, 28 min or 30 min; ball milling for 20 h to 30 h, for example, 20 h, 22 h, 24 h, 26 h or 30 h, and then sieve the mixture after removal.

[0079] In this invention, the solvent includes one or more of anhydrous ethanol, anhydrous propanol, anhydrous isobutanol, n-butyl ether, cyclopentyl methyl ether, anisole, isopropyl ether, trichloroethylene, carbon tetrachloride, toluene, chlorobenzene, cyclohexane, methylcyclohexane, and tetrahydrofuran, preferably one or more of anhydrous ethanol, anhydrous propanol, and anhydrous isobutanol.

[0080] Step 2) involves adding the lithium-rich manganese-based cathode material matrix into the slurry, ultrasonically mixing it, wet coating it, spray drying it using a nano spray dryer, and then performing a third sintering process to obtain a composite lithium-rich manganese-based oxide cathode material intermediate.

[0081] In this invention, the ultrasonic treatment time is 0.5 to 2 hours, preferably 1 to 1.5 hours; the sieving is to remove most of the secondary particles >4μm and <0.8μm.

[0082] In this invention, the heating rate of the third sintering is 5 to 15°C / min, for example, 5°C / min, 8°C / min, 10°C / min, 12°C / min or 15°C / min; the temperature is 200 to 250°C, for example, 200°C, 210°C, 220°C, 230°C, 240°C or 250°C; and the holding time is 2 to 4 hours, for example, 2 hours, 3 hours or 4 hours.

[0083] Step 3) involves mixing the composite lithium-rich manganese-based cathode material intermediate with the crushed oxide solid electrolyte in an anhydrous environment, and then performing multi-stage mixing, dilution, and coating to obtain the composite lithium-rich manganese-based cathode material.

[0084] Step 3) involves ball milling. The parameters for ball milling the oxide solid electrolyte are as follows: Place the oxide solid electrolyte in a zirconia crucible. Mix large zirconia balls (8mm in diameter) and small zirconia balls (5mm in diameter) at a mass ratio of 1:(1-3), for example, 1:1, 1:2, or 1:3. Prepare mixed zirconia balls at a ball-to-material mass ratio of approximately 1:(0.5-1.5), for example, 1:0.5, 1:1, or 1:1.5. Weigh the mixed zirconia balls and place them into a ball mill jar for ball milling. Set the ball milling speed to 200 r / min to 400 r / min, for example, 200 r / min, 250 r / min, 300 r / min, 350 r / min, etc. 0 r / min or 400 r / min; forward rotation for 15 min to 30 min, for example, 15 min, 18 min, 20 min, 25 min, 28 min or 30 min; interval for 30 min to 40 min, for example, 30 min, 32 min, 34 min, 36 min, 38 min or 40 min; reverse rotation for 15 min to 30 min, for example, 15 min, 18 min, 20 min, 25 min, 28 min or 30 min; ball milling for 20 h to 30 h, for example, 20 h, 22 h, 24 h, 26 h or 30 h, and then sieve the mixture after removal.

[0085] In this invention, the method for preparing the lithium-rich manganese-based oxide cathode material matrix includes the following steps:

[0086] 1) A metal salt solution containing manganese ions and halide ions, a precipitant, and a complexing agent are passed into the bottom liquid to carry out a coprecipitation reaction to obtain a precursor; during the coprecipitation reaction, the mother liquor is discharged, and the discharge rate of the mother liquor is consistent with the total inflow rate.

[0087] 2) The precursor is subjected to a first sintering to obtain manganese oxide;

[0088] 3) After cooling the manganese oxide, mix it with the lithium source and perform a second sintering to obtain a lithium-rich manganese-based oxide cathode material matrix.

[0089] The halide ions in the metal salt solution containing manganese ions and halide ions are one or more of chloride ions, fluoride ions and bromide ions, preferably chloride ions and fluoride ions; the total metal content in the metal salt solution containing manganese ions and halide ions is 1 mol / L to 4 mol / L, for example, it can be 1 mol / L, 2 mol / L, 3 mol / L or 4 mol / L, etc.

[0090] The precipitant comprises sodium hydroxide, and the mass fraction of the precipitant is 9wt% to 30wt%, for example, 9.6wt%, 15wt%, 20wt%, 25wt%, or 30wt%. The complexing agent comprises one or more of ammonia, ammonium sulfate, and ammonium chloride, preferably ammonia, and the mass fraction of the complexing agent is 8wt% to 30wt%, for example, 8wt%, 15wt%, 20wt%, 25wt%, or 30wt%. The base solution comprises water, the precipitant, and the complexing agent, for example, one or more of the following: pH value of the base solution is 10.4 to 12.8, for example, 10.5, 10.8, 11, 11.5, 12, 12.5, or 12.8. The ammonia concentration in the base solution is 3g / L to 8g / L, for example, 3g / L, 4g / L, 5g / L, 6g / L, 7g / L, or 8g / L.

[0091] The temperature of the coprecipitation reaction is 60℃ to 80℃, for example, 60℃, 65℃, 70℃, 75℃, or 80℃; the flow rate of the metal salt solution is 0.5% / h to 2.0% / h of the reaction vessel volume, for example, 0.5% / h, 1% / h, 1.5% / h, or 2% / h; the pH value during the coprecipitation reaction is 9.4 to 11.6, for example, 9.4, 10, 10.5, 11, 11.5, or 11.6; the ammonia concentration during the coprecipitation reaction is 4.2 g / L to 8.6 g / L, for example, 4.2 g / L, 4.5 g / L, 5 g / L, 5.5 g / L, 6 g / L, 7 g / L, 8 g / L, or 8.6 g / L.

[0092] The coprecipitation reaction is carried out under stirring conditions, with a stirring speed of 450-800 rpm, preferably 500-750 rpm, and more preferably 600-700 rpm; after the coprecipitation reaction is completed, the reaction further includes solid-liquid separation, followed by washing and drying of the solid.

[0093] The molar ratio of the manganese oxide to the lithium source is 1.2 to 1.4:1, for example, it can be 1.2:1, 1.3:1 or 1.4:1, etc.

[0094] The atmospheres for the first sintering and the second sintering are each independently either air or oxygen atmospheres;

[0095] The first sintering includes a first sintering heating stage and a first sintering holding stage. The first sintering heating stage heats the temperature to 500-700℃, for example, 500℃, 550℃, 600℃, 650℃, or 700℃. The heating rate of the first sintering heating stage is 2-4℃ / min, for example, 2℃ / min, 3℃ / min, or 4℃ / min. The holding time of the first sintering holding stage is 6-10h, for example, 6h, 7h, 8h, 9h, or 10h.

[0096] The second sintering process includes first controlling the heating rate to be 10–30 °C / min, for example, 10 °C / min, 15 °C / min, 20 °C / min, 25 °C / min, or 30 °C / min; heating to 200–300 °C, for example, 200 °C, 250 °C, or 300 °C; then adjusting the heating rate to 8–15 °C / min, for example, 8 °C / min, 10 °C / min, 12 °C / min, 14 °C / min, or 15 °C / min; heating to 600–700 °C, for example, The temperature can be set to 600℃, 650℃, or 700℃, etc.; the holding time can be 2 to 4 hours, for example, 2 hours, 3 hours, or 4 hours; finally, the heating rate can be adjusted to 1 to 51℃ / min, for example, 1℃ / min, 10℃ / min, 20℃ / min, 30℃ / min, 40℃ / min, or 51℃ / min, etc.; the temperature can be raised to 900 to 1200℃, for example, 900℃, 950℃, 1000℃, 1100℃, or 1200℃, etc.; the holding time can be 6 to 10 hours, for example, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, etc.

[0097] The present invention also provides a lithium-ion battery comprising the above-mentioned composite lithium-rich manganese-based cathode material.

[0098] Example 1

[0099] 1. Preparation of lithium-rich manganese-based cathode material precursors

[0100] ① Solution preparation: Weigh out nickel sulfate, manganese sulfate, manganese chloride, titanium sulfate, and sodium fluoride according to the molar ratio of nickel sulfate:manganese sulfate:manganese chloride:titanium sulfate:sodium fluoride of 0.245:0.7495:0.0005:0.005:0.003, and add pure water to prepare a manganese-containing metal salt suspension with a total Ni+Mn+Ti content of 2mol / L; prepare an 8wt% ammonia solution and a 9.6wt% sodium hydroxide solution.

[0101] ② Reaction: Water, sodium hydroxide solution, and ammonia solution are added to the reactor to prepare a base solution. The pH of the base solution is controlled at 11.2-11.6, and the ammonia concentration in the base solution is 5.4-6.0 g / L. The temperature is raised to 65℃, and nitrogen gas is introduced simultaneously while stirring at 400 rpm. The feed flow rate of the manganese-containing metal salt solution is controlled at 2.0-2.4% of the reactor volume / h. The pH of the co-precipitation reaction is controlled at 10.3-10.5 using sodium hydroxide solution, and the ammonia concentration is controlled at 6.0-6.4 g / L using ammonia solution. During the co-precipitation reaction, the mother liquor is discharged through a concentration device, and the discharge rate of the mother liquor is consistent with the total feed rate. The reaction is stopped when the target particle size of D50 is obtained as 3.5±0.5 μm.

[0102] ③ After the synthesis stage is completed, the material is washed with 0.1 mol / L sodium hydroxide solution and deionized water, filtered, and the washed product is obtained;

[0103] ④ Place the washed product in a regular drying oven and dry it at 105℃ for 5 hours to obtain the dried product; after sieving, spherical or near-spherical nickel-manganese hydroxide precursors are obtained.

[0104] 2. Preparation of lithium-rich manganese-based cathode materials

[0105] ① Weigh the nickel-manganese hydroxide precursor prepared above and transfer it into a box furnace for the first sintering treatment. The atmosphere is air, the heating rate is 3℃ / min, the temperature is raised to 600℃, and the temperature is held for 8h to obtain doped manganese oxide.

[0106] ② Weigh the doped manganese oxide and lithium carbonate, and crush and mix them according to the molar ratio Li:TM=1.35:1. After the mixture is uniform, carry out the second sintering. First, control the heating rate to 20℃ / min and heat to 300℃. Then adjust the heating rate to 10℃ / min and heat to 650℃. Hold for 3h. Finally, adjust the heating rate to 3℃ / min and heat to 1000℃. Hold for 8h. The sintering atmosphere is air. After sintering, cool. After sintering, lithium-rich manganese-based oxide cathode material is obtained.

[0107] The secondary particle size (D50) of the obtained cathode material product was 1.64 μm. The content of metal elements, fluorine, and chlorine was determined by ICP-MS, and its molecular formula was calculated to be Li. 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 .

[0108] 3. Preparation of intermediates for composite lithium-rich manganese-based cathode materials

[0109] ① In a dry environment, weigh Li according to the mass ratio of 1:0.125wt%:0.075wt%:0.4wt%:0.1wt%:0.7wt%. 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 Li 2.8 Sc 0.8 Zr 0.2 Cl6, Li3InCl6, LiNbO3, LiAlO2, Na3ZrSnSi2PO4, for later use;

[0110] ②Li 2.8 Sc 0.8 Zr 0.2 After mixing Cl6, Li3InCl6, LiNbO3, and LiAlO2, the mixture was placed in a zirconia crucible. Large zirconia balls (8 mm in diameter), medium zirconia balls (5 mm in diameter), and small zirconia balls (1 mm in diameter) were prepared in a mass ratio of 1:2:2 to form mixed zirconia balls. The mixed zirconia balls were weighed at a ball milling jar at a ball material mass ratio of approximately 1:1 and ball milled. The ball milling speed was set to 400 r / min, with 20 min of forward rotation, 30 min interval, and 20 min of reverse rotation. After ball milling for 24 h, the mixture was removed and sieved to obtain the mixture. The particle size D50 of the mixture was measured to be 26 nm.

[0111] ③ Under dry air protection, weigh the Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 The mixture was added to anhydrous ethanol-cyclohexane solvent (V 无水乙醇 :V 环己烷 =15:85), the solid content of the resulting suspension was controlled at 25%, sealed, and ultrasonically sonicated for 1 hour; then spray-dried using a nano-spray dryer, and transferred to a box furnace for third sintering at a heating rate of 10℃ / min, heated to 230℃, held for 3 hours, and sieved through a 5000-mesh sieve. The secondary particles obtained from sieving were crushed by a Raymond mill for 10 minutes and then added to the undersize material for mixing; thus, a composite lithium-rich manganese-based cathode material intermediate was obtained.

[0112] 4. Preparation of composite lithium-rich manganese-based cathode materials

[0113] ① Place Na3ZrSnSi2PO4 in a zirconia crucible. Mix zirconia balls (large spheres, 8 mm in diameter and small spheres, 5 mm in diameter) at a mass ratio of 1:2 to form mixed zirconia balls. Weigh the mixed zirconia balls at a ball milling jar at a ball material mass ratio of approximately 1:1 and put them into the ball milling jar for ball milling. Set the ball milling speed to 300 r / min, rotate forward for 20 min, pause for 30 min, and then rotate in reverse for 20 min. After ball milling for 24 h, take it out and sieve it to obtain the ball-milled Na3ZrSnSi2PO4. The particle size D50 was measured to be 69 nm.

[0114] ② The composite lithium-rich manganese-based cathode material intermediate and ball-milled Na3ZrSnSi2PO4 are subjected to multi-stage mixing, dilution, and coating: In the first stage of mixing, dilution, and coating, the mass of Na3ZrSnSi2PO4 is 25% of the mass of the composite lithium-rich manganese-based cathode material intermediate in a mixer, and after mixing for 10 minutes, the first-stage mixed, diluted, and coated material is obtained; in the second stage of mixing, dilution, and coating, the composite lithium-rich manganese-based cathode material intermediate is added to the first-stage mixed, diluted, and coated material (so that Na3ZrSnSi2PO4 becomes Na3ZrSnSi2PO4). After i2PO4 accounts for 5% of the total mass of the composite lithium-rich manganese-based cathode material intermediate, it is mixed in a mixer for 20 minutes to obtain the second-stage mixed dilution coating material. During the third mixed dilution coating, the composite lithium-rich manganese-based cathode material intermediate is added to the second-stage mixed dilution coating material (so that the mass of Na3ZrSnSi2PO4 accounts for 1% of the total mass of the composite lithium-rich manganese-based cathode material intermediate), and then mixed in a mixer for 30 minutes to obtain the composite lithium-rich manganese-based cathode material.

[0115] The composite lithium-rich manganese-based cathode material was tested using ICP-MS to determine the metal element content and the fluorine and chlorine content, and its molecular formula was calculated as follows:

[0116] Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 @0.125wt%Li 2.8 Sc 0.8 Zr 0.2 Cl6·0.075wt%Li3InCl6·0.4wt%LiNbO3·0.1wt%LiAlO2@1.0wt%Na3ZrSnSi2PO4.

[0117] Example 2 (First coating layer has a large D50, second coating layer has a small D50)

[0118] The lithium-rich manganese-based cathode material prepared in Example 1 was used to prepare intermediates for composite lithium-rich manganese-based cathode materials and subsequent composite lithium-rich manganese-based cathode materials.

[0119] The only difference from Example 1 is:

[0120] 3. Preparation of intermediates for composite lithium-rich manganese-based cathode materials

[0121] ②Li 2.8 Sc 0.8 Zr 0.2 After mixing Cl6, Li3InCl6, LiNbO3, and LiAlO2, the mixture was placed in a zirconia crucible. Large zirconia balls (8 mm in diameter), medium zirconia balls (5 mm in diameter), and small zirconia balls (1 mm in diameter) were prepared at a mass ratio of 1:2 to form mixed zirconia balls. The mixed zirconia balls were weighed at a ball milling jar at a ball material mass ratio of approximately 1:1 and ball milled. The ball milling speed was set to 250 r / min, with a forward rotation time of 20 min, a 30 min interval, and a reverse rotation time of 20 min. After ball milling for 24 h, the mixture was removed and sieved to obtain the mixture. The particle size D50 of the mixture was measured to be 147 nm.

[0122] 4. Preparation of composite lithium-rich manganese-based cathode materials

[0123] ① Place Na3ZrSnSi2PO4 in a zirconia crucible. Mix zirconia balls (large spheres, 8 mm in diameter and small spheres, 1 mm in diameter) at a mass ratio of 1:2:3 to form a mixed zirconia ball. Weigh the mixed zirconia balls at a ball-material mass ratio of approximately 1:1 and put them into a ball mill jar for ball milling. Set the ball milling speed to 600 r / min, rotate clockwise for 20 min, pause for 30 min, and then rotate counterclockwise for 20 min. After ball milling for 24 h, remove the ball milled Na3ZrSnSi2PO4 and sieve it to obtain the ball-milled Na3ZrSnSi2PO4. The particle size D50 was measured to be 34 nm.

[0124] Other preparation conditions are the same as in Example 1.

[0125] The composite lithium-rich manganese-based cathode material was tested using ICP-MS to determine the metal element content and the fluorine and chlorine content, and its molecular formula was calculated as follows:

[0126] Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 @0.125wt%Li 2.8 Sc 0.8 Zr 0.2 Cl6·0.075wt%Li3InCl6·0.4wt%LiNbO3·0.1wt%LiAlO2@1.0wt%Na3ZrSnSi2PO4.

[0127] Example 3 (The mass ratio of halide solid electrolyte to lithium oxide in the first coating layer is 2.5:1)

[0128] The lithium-rich manganese-based cathode material prepared in Example 1 was used to prepare intermediates for composite lithium-rich manganese-based cathode materials and subsequent composite lithium-rich manganese-based cathode materials.

[0129] The difference from Example 1 is as follows:

[0130] 3. When preparing intermediates for composite lithium-rich manganese-based cathode materials, Li 2.8 Sc 0.8 Zr 0.2 The mass ratios of Cl6, L3InCl6, LiNbO3, and LiAlO2 were adjusted to 0.32wt%, 0.18wt%, 0.16wt%, and 0.04wt%, respectively.

[0131] Other preparation conditions are the same as in Example 1.

[0132] The obtained composite lithium-rich manganese-based cathode material was tested by ICP-MS to determine the metal element content and the contents of fluorine and chlorine, and its molecular formula was calculated to be Li. 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.42 8F 0.003 Cl 0.001 @0.32wt%Li 2.8 Sc 0.8 Zr 0.2 Cl6·0.18wt% Li3InCl6·0.16wt% LiN bO3·0.04wt% LiAlO2@1.0wt%Na3ZrSnSi2PO4;

[0133] Example 4 (First coating layer content is 7%)

[0134] The lithium-rich manganese-based cathode material prepared in Example 1 was used to prepare intermediates for composite lithium-rich manganese-based cathode materials and subsequent composite lithium-rich manganese-based cathode materials.

[0135] The difference from Example 1 is as follows:

[0136] 3. When preparing intermediates for composite lithium-rich manganese-based cathode materials, Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 Li 2.8 Sc 0.8 Zr0.2 The mass ratio of Cl6, L3InCl6, LiNbO3, and LiAlO2 is adjusted to 1:1.25wt%:0.75wt%:4wt%:1wt%.

[0137] Other preparation conditions are the same as in Example 1.

[0138] The composite lithium-rich manganese-based cathode material was tested using ICP-MS to determine the metal element content and the fluorine and chlorine content, and its molecular formula was calculated as follows:

[0139] Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 @1.25wt%Li 2.8 Sc 0.8 Zr 0.2 Cl6·0.75wt%Li3InCl6·4wt%LiNbO3·1wt%LiAlO2@1.0wt%Na3ZrSnSi2PO4.

[0140] Example 5 (Second coating content is 8%)

[0141] The lithium-rich manganese-based cathode material prepared in Example 1 was used to prepare intermediates for composite lithium-rich manganese-based cathode materials and subsequent composite lithium-rich manganese-based cathode materials.

[0142] The difference from Example 1 is as follows:

[0143] 4. When preparing composite lithium-rich manganese-based cathode materials,

[0144] ② The composite lithium-rich manganese-based cathode material intermediate and the ball-milled Na3ZrSnSi2PO4 were subjected to multi-stage mixing, dilution and coating: In the first stage of mixing, dilution and coating, the mass of Na3ZrSnSi2PO4 was 40% of the mass of the composite lithium-rich manganese-based cathode material intermediate in a mixer, and the mixture was mixed for 5 minutes to obtain the first stage of mixed dilution and coating material; In the second stage of mixing, dilution and coating, the composite lithium-rich manganese-based cathode material intermediate was added to the first stage of mixed dilution and coating material (so that the mass of Na3ZrSnSi2PO4 accounted for 8% of the total mass of the composite lithium-rich manganese-based cathode material intermediate), and the mixture was mixed in a mixer for 8 minutes to obtain the composite lithium-rich manganese-based cathode material.

[0145] Other preparation conditions are the same as in Example 1.

[0146] The composite lithium-rich manganese-based cathode material was tested using ICP-MS to determine the metal element content and the fluorine and chlorine content, and its molecular formula was calculated as follows:

[0147] Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 @0.125wt%Li 2.8 Sc 0.8 Zr 0.2 Cl6·0.075wt%Li3InCl6·0.4wt%LiNbO3·0.1wt%LiAlO2@8wt%Na3ZrSnSi2PO4.

[0148] Example 6 (Lithium-rich manganese-based cathode material is polycrystalline, D50 is 11.3 μm)

[0149] The difference from Example 1 is as follows:

[0150] 1. When preparing lithium-rich manganese-based cathode material precursors,

[0151] ② Reaction: Water, sodium hydroxide solution, and ammonia solution are added to the reactor to prepare a base solution. The pH of the base solution is controlled at 11.2-11.6, and the ammonia concentration in the base solution is 5.4-6.0 g / L. The temperature is raised to 65℃, and nitrogen gas is introduced simultaneously while stirring at 400 rpm. The feed flow rate of the manganese-containing metal salt solution is gradually increased from 2.0% / h of the reactor volume to 6.3% / h. The pH of the co-precipitation reaction is controlled at 10.3-10.5 using sodium hydroxide solution, and the ammonia concentration is controlled at 6.0-6.4 g / L using ammonia solution. During the co-precipitation reaction, the mother liquor is discharged through a concentration device, and the discharge rate of the mother liquor is consistent with the total feed rate. The reaction is stopped when the target particle size of D50 is obtained as 11.0±0.5 μm.

[0152] 2. Preparation of lithium-rich manganese-based cathode materials

[0153] The lithium-rich manganese-based cathode material precursor product prepared above was weighed and transferred into a box furnace for the first sintering treatment. The atmosphere was air, the heating rate was 20℃ / min, the temperature was raised to 650℃, and the temperature was held for 10h to obtain doped nickel manganese oxide.

[0154] Doped nickel manganese oxide and lithium carbonate were weighed and mixed at a molar ratio of Li:TM = 1.35:1. After the mixture was homogeneous, a second sintering was performed. The heating rate was first controlled at 20℃ / min, and the temperature was raised to 300℃. Then the heating rate was adjusted to 10℃ / min, and the temperature was raised to 650℃. The temperature was held for 4 hours. Finally, the heating rate was adjusted to 3℃ / min, and the temperature was raised to 900℃. The temperature was held for 8 hours. The sintering atmosphere was air. After sintering, the material was cooled to obtain lithium-rich manganese-based oxide cathode material.

[0155] Other preparation conditions are the same as in Example 1.

[0156] The composite lithium-rich manganese-based cathode material was tested using ICP-MS to determine the metal element content and the fluorine and chlorine content, and its molecular formula was calculated as follows:

[0157] Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 @0.125wt%Li 2.8 Sc 0.8 Zr 0.2 Cl6·0.075wt%Li3InCl6·0.4wt%LiNbO3·0.1wt%LiAlO2@1.0wt%Na3ZrSnSi2PO4.

[0158] Example 7 (Undoped lithium-rich manganese-based cathode material)

[0159] The difference from Example 1 is as follows:

[0160] 1. Preparation of lithium-rich manganese-based cathode material precursors

[0161] ① Solution preparation: Weigh nickel sulfate and manganese sulfate according to the molar ratio of Ni to Mn of 0.25:0.75, add pure water to prepare a manganese-containing metal salt solution with a total Ni+Mn content of 2 mol / L;

[0162] Other preparation conditions are the same as in Example 1.

[0163] The molecular formula of the product is:

[0164] Li 1.35 Ni 0.25 Mn 0.75 O 2.425 @0.125wt%Li 2.8 Sc 0.8 Zr 0.2 Cl6·0.075wt% L3InCl6·0.4wt% LiNbO3·0.1wt% LiAlO2@1.0wt% Na3ZrSnSi2PO4.

[0165] Example 8

[0166] 1. When preparing lithium-rich manganese-based cathode material precursors

[0167] ① Solution preparation: Weigh out nickel sulfate, manganese sulfate, and manganese chloride according to the molar ratio of nickel sulfate:manganese sulfate:manganese chloride of 0.25:0.7485:0.0015, add pure water to prepare a manganese-containing metal salt suspension with a total Ni+Mn content of 2 mol / L; prepare an 8 wt% ammonia solution and a 9.6 wt% sodium hydroxide solution.

[0168] 2. Preparation of lithium-rich manganese-based cathode materials

[0169] ① Weigh the nickel-manganese hydroxide precursor prepared above and transfer it into a box furnace for the first sintering treatment. The atmosphere is oxygen, the heating rate is 2℃ / min, the temperature is raised to 550℃, and the temperature is held for 7h to obtain doped manganese oxide.

[0170] ② When weighing the doped manganese oxide and lithium carbonate for the second sintering, first control the heating rate to 30℃ / min, raise the temperature to 260℃, then adjust the heating rate to 15℃ / min, raise the temperature to 700℃, hold for 2h, and finally adjust the heating rate to 5℃ / min, raise the temperature to 1100℃, hold for 6h. The sintering atmosphere is oxygen. After sintering, cool. After sintering, lithium-rich manganese-based oxide cathode material is obtained.

[0171] The secondary particle size (D50) of the obtained cathode material product was 2.06 μm. The content of metal elements, fluorine, and chlorine was determined by ICP-MS, and its molecular formula was calculated to be Li. 1.35 Ni 0.25 Mn 0.75 O 2.1735 Cl 0.003 .

[0172] 3. Preparation of intermediates for composite lithium-rich manganese-based cathode materials

[0173] ① Weigh out Li according to the mass ratio of 1:0.1wt%:0.1wt%:0.2wt%:1.0wt%. 0.388 Ta 0.238 La 0.475 Cl3, LiAlOCl, LiZrO3, Li7La3Zr2O 12 ,spare;

[0174] ② The mass ratio of large zirconia balls (8mm in diameter), medium zirconia balls (5mm in diameter), and small zirconia balls (1mm in diameter) is 1:2:3, and the ball-to-material mass ratio is approximately 1:1.5. The ball mill speed is set to 320 r / min, with forward rotation for 25 min, interval for 20 min, and reverse rotation for 25 min. After ball milling for 20 h, the mixture is removed and sieved to obtain the mixture. The particle size D50 of the mixture is measured to be 34 nm.

[0175] ③ The solvent is anhydrous isobutanol-methylcyclohexane solvent (V 无水异丁醇 :V 甲基环己烷=2:8), the solid content of the resulting suspension was controlled at 20%, and ultrasonication was performed for 1.5 hours; after spray drying, the heating rate of the third sintering was 10℃ / min, the temperature was raised to 220℃, and the temperature was held for 2 hours. The secondary particles obtained by sieving were crushed by Raymond mill for 12 minutes and then added to the undersize material for mixing.

[0176] 4. Preparation of composite lithium-rich manganese-based cathode materials

[0177] ① Place Na3ZrSnSi2PO4 in a zirconia crucible. Mix zirconia balls (large 8mm in diameter and small 5mm in diameter) at a mass ratio of 1:2 to form a mixed zirconia ball. Weigh the mixed zirconia balls at a ball-material mass ratio of approximately 1:1 and put them into a ball mill jar for ball milling. Set the ball milling speed to 300 r / min, rotate forward for 20 min, pause for 30 min, and then rotate in reverse for 20 min. After ball milling for 24 h, remove the ball milled Na3ZrSnSi2PO4 and sieve it to obtain the ball-milled Na3ZrSnSi2PO4. The particle size D50 was measured to be 69 nm.

[0178] ② The composite lithium-rich manganese-based cathode material intermediate and the ball-milled Li7La3Zr2O 12 Multi-stage dilution coating was performed: During the first stage of dilution coating, Li7La3Zr2O 12 The mass of the mixture is 20% of the mass of the composite lithium-rich manganese-based cathode material intermediate, and the mixture is mixed for 8 minutes; during the second mixing, dilution, and coating, the mixture is mixed for 25 minutes.

[0179] The composite lithium-rich manganese-based cathode material was tested using ICP-MS to determine the metal element content and the fluorine and chlorine content, and its molecular formula was calculated as follows:

[0180] Li 1.35 Ni 0.25 Mn 0.75 O 2.1735 Cl 0.003 @0.1wt%Li 0.388 Ta 0.238 La 0.475 Cl3·0.1wt% LiAlOCl·0.1wt% LiZrO3@1.0wt% Li7La3Zr2O 12 .

[0181] Comparative Example 1 (uncovered)

[0182] The difference from Example 1 is as follows:

[0183] The lithium-rich manganese-based cathode material prepared in Example 1 is uncoated, without a first or second coating layer. The molecular formula of the product is: Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005O 2.428 F 0.003 Cl 0.001 .

[0184] Other preparation conditions are the same as in Example 1.

[0185] Comparative Example 2 (without a second coating layer)

[0186] The difference from Example 1 is as follows:

[0187] The lithium-rich manganese-based cathode material prepared in Example 1 was used to prepare only a composite lithium-rich manganese-based cathode material intermediate without a second coating layer. Other preparation conditions were the same as in Example 1.

[0188] The molecular formula of the product is:

[0189] Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 @0.125wt%Li 2.8 Sc 0.8 Zr 0.2 Cl6 · 0.075wt% L3InCl6 · 0.4wt% LiNbO3 · 0.1wt% LiAlO2.

[0190] Comparative Example 3 (without the first coating layer)

[0191] The difference from Example 1 is as follows:

[0192] The lithium-rich manganese-based cathode material prepared in Example 1 was directly coated with a second coating layer, without a first coating layer, and other preparation conditions were the same as in Example 1.

[0193] The product's molecular formula is Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 @1.0wt% Na3ZrSnSi2PO4.

[0194] Comparative Example 4 (The first coating layer contains only halide solid electrolyte)

[0195] The difference from Example 1 is as follows:

[0196] When preparing the lithium-rich manganese-based cathode material obtained in Example 1 into a composite lithium-rich manganese-based cathode material intermediate, only Li was added during ball milling. 2.8 Sc 0.8 Zr 0.2Cl6 and L3InCl6, without LiNbO3 and LiAlO2, are coated with a second layer, and other preparation conditions are the same as in Example 1.

[0197] The molecular formula of the product is:

[0198] Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 @0.125wt%Li 2.8 Sc 0.8 Zr 0.2 Cl6·0.075wt% L3InCl6@1.0wt% Na3ZrSnSi2PO4.

[0199] Comparative Example 5 (the first coating layer contains only lithium oxide)

[0200] The difference from Example 1 is as follows:

[0201] When preparing the intermediate for the composite lithium-rich manganese-based cathode material obtained in Example 1, only LiNbO3 and LiAlO2 are added during ball milling, and Li is not included. 2.8 Sc 0.8 Zr 0.2 Cl6 and L3InCl6 are then coated with a second layer, and other preparation conditions are the same as in Example 1.

[0202] The molecular formula of the product is:

[0203] Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 @0.4wt%LiNbO3·0.1wt%LiAlO2@1.0wt%Na3ZrSnSi2PO4.

[0204] Comparative Example 6 (coating layer contains only halide solid electrolyte)

[0205] The difference from Example 1 is as follows:

[0206] When preparing the lithium-rich manganese-based cathode material obtained in Example 1 into a composite lithium-rich manganese-based cathode material intermediate, only Li was added during ball milling. 2.8 Sc 0.8 Zr 0.2Cl6 and L3InCl6, without LiNbO3 and LiAlO2, are coated with a second layer, and other preparation conditions are the same as in Example 1.

[0207] The molecular formula of the product is:

[0208] Li 1.35 Ni 0.245 Mn 0.750 Ti 0.005 O 2.428 F 0.003 Cl 0.001 @0.125wt%Li 2.8 Sc 0.8 Zr 0.2 Cl6·0.075wt%L3InCl6.

[0209] The product test data for each embodiment and comparative example are shown in Table 1 below:

[0210] Table 1 Product Test Data

[0211]

[0212]

[0213] The products obtained from each implementation and comparative example were subjected to hygroscopicity tests:

[0214] The sample was placed in a constant temperature and humidity chamber at 25°C and 60% relative humidity for 24 hours. The sample mass M0 before exposure was measured using a precision balance. t Then, calculate the initial mass m0 of the coating layer based on the ratio of the coating layer to the substrate, and the mass m of the coating layer after exposure. t ), calculate the moisture absorption rate of the coating layer:

[0215]

[0216] The DC internal resistance of the products obtained from each embodiment and comparative example was tested:

[0217] Table 2 shows the DC internal resistance test results of the products obtained from each embodiment and comparative example.

[0218] step Process Name Time (s) Current (A) Voltage (V) mark 1 Discharge to 50% SOC 2 hibernation 5 <![CDATA[V t0 ]]> 3 Pulse discharge 10 2C(I) 2 <![CDATA[V t1 ]]>

[0219] Formula: DCIR = (V t1 -V t0 ) / I

[0220] The positive electrode materials obtained from the various embodiments and comparative examples were mixed with conductive carbon black and binder PVDF (polyvinylidene fluoride) in a ratio of 8:1:1 to form a slurry, which was then coated on aluminum foil to form a positive electrode sheet. The negative electrode sheet was made of lithium metal. In a vacuum glove box, the battery casing, positive electrode sheet, negative electrode sheet, spring sheet, gasket, and solid electrolyte membrane were assembled into a coin cell. The positive electrode sheet was in contact with the solid electrolyte containing Li3ScCl6, and the negative electrode sheet was in contact with the solid electrolyte containing Li6PS5Cl.

[0221] The Blue Electricity testing system was used to perform 1C testing at a voltage of 3.0-4.6V (the specific capacitance used for current calculation was 200mAh g). -1 The capacity retention rate was calculated after 300 charge-discharge cycles as follows: Capacity retention rate = (300th discharge capacity / 1st discharge capacity) * 100%. The capacity retention rates after 300 cycles are shown in Table 3.

[0222] The electrochemical test results of each embodiment and comparative example are shown in Table 3:

[0223] Table 3. Hygroscopicity and Electrochemical Test Data

[0224]

[0225] As can be seen from Tables 1 and 3, compared with Comparative Examples 1-6, the composite lithium-rich manganese-based oxide cathode materials prepared in Examples 1-8, through the special structure and composition combination of the matrix lithium-rich manganese-based cathode material - the first coating layer of halide solid electrolyte and oxide mixture - the second coating layer of oxide solid electrolyte, can significantly improve the ionic conductivity (corresponding to rate performance), while also suppressing side reactions such as hydrolysis, reducing the difficulty of encapsulation, and improving the cycle performance after moisture absorption by the added halide solid electrolyte.

[0226] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a composite lithium-rich manganese-based cathode material, characterized in that, Includes the following steps: 1) A slurry is prepared by mixing a halide solid electrolyte and a lithium oxide-containing compound, and then adding a solvent; 2) Mix the lithium-rich manganese-based oxide cathode material matrix and slurry, perform wet coating, dry, and perform third sintering to obtain a composite lithium-rich manganese-based cathode material intermediate; 3) In an anhydrous environment, the composite lithium-rich manganese-based cathode material intermediate is mixed with an oxide solid electrolyte and subjected to multi-stage mixing, dilution and coating to obtain the composite lithium-rich manganese-based cathode material. The composite lithium-rich manganese-based cathode material has a three-layer structure, consisting of a lithium-rich manganese-based oxide cathode material matrix, a first coating layer, and a second coating layer from the inside out. The first coating layer is a mixture of a halide solid electrolyte and a lithium oxide-containing electrolyte; the second coating layer is an oxide solid electrolyte.

2. The method for preparing the composite lithium-rich manganese-based cathode material according to claim 1, characterized in that, The halide solid electrolyte includes Li3YCl6, Li3InCl6, Li6PS5Cl, and Li 0.388 Ta 0.238 La 0.475 Cl3, LiAlOCl, Li 3-x Sc 1- x Zr x Cl6 and Li3ZrCl4O 1.5 One or more of them; The lithium-containing oxide includes one or more of LiAlO2, LiNbO3 and Li2ZrO3; The oxide solid electrolyte includes one or more of the following: garnet-type oxide solid electrolyte, NASICON-type oxide solid electrolyte, perovskite-type oxide solid electrolyte, LiPON-type oxide solid electrolyte, and anti-perovskite-type oxide solid electrolyte.

3. The method for preparing the composite lithium-rich manganese-based cathode material according to claim 1, characterized in that, The lithium-rich manganese-based oxide cathode material matrix is ​​a single crystal; and / or the lithium-rich manganese-based oxide cathode material matrix contains halogens.

4. The method for preparing the composite lithium-rich manganese-based cathode material according to claim 1, characterized in that, The lithium-rich manganese-based oxide cathode material matrix is ​​Li. x Mn y Me 1-y O a Q b Me is selected from at least one of Ni, Co, Nb, Mo, Ti, Zr, Mg, W and Al, Q is selected from at least one of F, Cl and Br, and 1.05≤x≤1.4, 0.5≤y≤1, 1.6≤a+2b≤2.5, and 0≤b≤0.

4.

5. The method for preparing the composite lithium-rich manganese-based cathode material according to claim 1, characterized in that, The mass ratio of the halide solid electrolyte to the lithium oxide in the first coating layer is 1:1 to 4; The mass of the first coating layer is 0.1 wt% to 5 wt% of the mass of the lithium-rich manganese-based oxide cathode material matrix; The mass of the second coating layer is 0.1wt% to 5wt% of the mass of the lithium-rich manganese-based oxide cathode material matrix.

6. The method for preparing the composite lithium-rich manganese-based cathode material according to claim 1, characterized in that, The average particle size D50 of the lithium-rich manganese-based oxide cathode material matrix is ​​1.0 μm to 4.0 μm; The average particle size D50 of the first coating layer is 10 nm to 50 nm; The average particle size D50 of the second coating layer is 60 nm to 100 nm; The average particle size D50 of the composite lithium-rich manganese-based cathode material is 1.1 μm to 4.3 μm, and the particle size distribution of the composite lithium-rich manganese-based cathode material spans from 1 to 4.

7. The method for preparing the composite lithium-rich manganese-based cathode material according to claim 1, characterized in that, The solvent in step 1) includes one or more of the following: anhydrous ethanol, anhydrous propanol, anhydrous isobutanol, n-butyl ether, cyclopentyl methyl ether, anisole, isopropyl ether, trichloroethylene, carbon tetrachloride, toluene, chlorobenzene, cyclohexane, methylcyclohexane, and tetrahydrofuran. In step 2), the heating rate during the third sintering is 5℃ / min to 15℃ / min, and the temperature is raised to 200℃ to 250℃, and held for 2h to 4h.

8. The method for preparing the composite lithium-rich manganese-based cathode material according to claim 1, characterized in that, A method for preparing a lithium-rich manganese-based oxide cathode material matrix includes the following steps: 1) A metal salt solution containing manganese ions and halide ions, a precipitant, and a complexing agent are passed into the bottom liquid to carry out a coprecipitation reaction to obtain a precursor; during the coprecipitation reaction, the mother liquor is discharged, and the discharge rate of the mother liquor is consistent with the total inflow rate. 2) The precursor is subjected to a first sintering to obtain manganese oxide; 3) After cooling the manganese oxide, mix it with the lithium source and perform a second sintering to obtain a lithium-rich manganese-based oxide cathode material matrix.

9. A lithium-ion battery, characterized in that, The lithium-ion battery includes a composite lithium-rich manganese-based cathode material prepared by the method described in any one of claims 1 to 8.

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