A composite positive electrode material for solid-state batteries and a preparation method and application thereof

Abstract

The application relates to the technical field of batteries, in particular to a composite positive electrode material for solid-state batteries and a preparation method and application thereof. The composite positive electrode material comprises a positive electrode base material and a coating layer arranged on the surface of the positive electrode base material, and the coating layer comprises a halide electrolyte and a modifier group -N(CH3)3R, wherein R is -C n H 2n+1 , and n>=9. The composite positive electrode material has excellent smoothness and suitable bulk density, can reduce the porosity of the positive electrode, reduce the space charge layer and interface reaction between the positive electrode material and the sulfide electrolyte, and improve the energy density, rate performance and cycle stability of the sulfide solid-state lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a composite cathode material that can be used in solid-state batteries, its preparation method, and its application. Background Technology

[0002] Solid-state lithium-ion batteries overcome the problems of leakage and combustion of liquid electrolytes in traditional lithium-ion batteries, offering higher safety. Sulfide electrolytes are a type of solid-state electrolyte with sulfur as the main component and PS4 or MS4 (where M represents metals such as Sn or Ge) as the basic structural unit. Due to their high lithium-ion conductivity (3mS / cm~25mS / cm), low interfacial resistance, and excellent mechanical ductility, sulfide electrolytes are currently the mainstream electrolyte material used in solid-state lithium-ion batteries. Lithium-ion batteries with sulfide electrolytes as the main electrolyte material are called sulfide solid-state lithium-ion batteries, which are the mainstream type of solid-state lithium-ion battery.

[0003] The cathode material determines the capacity, rate capability, and cycle stability of solid-state lithium-ion batteries. In sulfide solid-state lithium-ion batteries, a sulfide electrolyte is indispensable for lithium-ion conduction, which leads to the following problems: 1) Due to the Fermi level mismatch between the sulfide and the uncoated cathode material, a space charge layer is generated, increasing polarization and reducing battery capacity and rate performance; 2) The sulfide electrolyte has a narrow electrochemical window, which is problematic when operating at high voltages (>4.2V vs Li) with the uncoated cathode material. + / Li), the sulfide electrolyte at the interface continues to decompose, which destroys the cycle stability; 3) due to the lack of sliding between the sulfide electrolyte and the cathode material particles, the rigid cathode material is prone to cracking during the rolling process, and the active material that is difficult to slide makes the thickness uniformity of the cathode roll poor; more importantly, the lack of sliding leads to high porosity of the rolled cathode, poor particle contact, and low cathode compaction density, which increases the cathode impedance and reduces the energy density of the sulfide solid lithium-ion battery.

[0004] To overcome the space charge layer, interfacial reactions, and contact problems between the cathode material and the sulfide electrolyte, the widely adopted method is to construct a stable coating layer on the surface of the cathode material to isolate it from direct contact with the sulfide electrolyte and reduce interfacial reactions. However, existing coating layers have low room temperature ionic conductivity, which is detrimental to rate performance. Furthermore, to control the coating thickness and ensure coating uniformity, equipment and processes such as magnetron sputtering and atomic layer deposition (ALD) need to be introduced, making mass production difficult.

[0005] Furthermore, the most fundamental application barrier for existing electrolyte coatings is the issue of moisture stability at high dew points. Conventional electrolyte coatings are easily damaged during the coating process and subsequent storage and transportation, leading to a significant decrease in the ionic conductivity of the coating and the loss of high-voltage cathode stability, ultimately causing the cathode material to deactivate due to coating decomposition. If the dew point control temperature is lowered from -30℃ to -45℃, the dehumidifier energy consumption will increase by more than 50%; in addition to energy consumption, if the packaging is damaged during storage and transportation, not only will the entire batch of material be scrapped, but there is also a risk of HCl leakage. As the production of cathode materials, which are bulk chemicals, is often a continuous production process with tons of samples, controlling the dew point below -45℃ in the halide coating section and subsequent processing and transportation sections is impractical.

[0006] Therefore, improving the moisture stability of cathode materials under high dew point conditions, reducing the porosity of cathode materials during cathode rolling, and reducing the space charge layer and interfacial reactions between cathode materials and sulfide electrolytes are crucial for improving the rate performance, cycle stability, and energy density of sulfide solid-state lithium-ion batteries.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] One objective of this invention is to provide a composite cathode material to address the technical problems of poor moisture stability and high porosity of existing cathode materials under high dew point environments. The composite cathode material of this invention, by coating a halide electrolyte with the modifying group -N(CH3)3R, can improve its moisture stability in air, enhance its surface smoothness and bulk density, reduce cathode porosity, and decrease the space charge layer and interfacial reactions between the cathode material and the sulfide electrolyte.

[0009] Another objective of this invention is to provide a method for preparing composite cathode materials that is simple, easy to implement, and environmentally friendly, thereby enabling the composite cathode materials to have a better coating effect and obtain composite cathode materials with better electrochemical performance.

[0010] Another object of the present invention is to provide a positive electrode.

[0011] Another object of the present invention is to provide a battery.

[0012] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0013] A composite cathode material includes a cathode substrate material and a coating layer disposed on the surface of the cathode substrate material. The coating layer comprises a halide electrolyte and a modifying group -N(CH3)3R, wherein R is -C. n H 2n+1 , n≥9.

[0014] In some implementations, n satisfies: 9 ≤ n ≤ 30.

[0015] In some implementations, R is a straight chain or contains at least one branch, and the branch is located at position ω-2 to ω-6 in R.

[0016] In some embodiments, R is a straight chain or contains at least one branch, and the branch is located at position ω-2 to ω-6 of R, wherein the branch is derived from at least one of methyl, ethyl, propyl and isopropyl.

[0017] In some embodiments, the chemical formula of the halide electrolyte includes Li z Q q M d Where 2≤z≤3, 0.5≤q≤1, 3≤d≤6, Q includes at least one of In, Y, Zr, Sc and Er, and M is selected from halogens.

[0018] In some embodiments, the mass content of the modifying group -N(CH3)3R in the composite cathode material is 0.01% to 0.5%.

[0019] In some embodiments, the mass ratio of the halide electrolyte to the modified group -N(CH3)3R is (10-600):1.

[0020] In some embodiments, the cathode substrate material includes LiNi. 1-x1-y1 Co x1 Mn y1 O2, LiCoO2, LiNi 0.5 Mn 1.5 O4 and x2Li2MnO3·(1-x2)LiNi a Co b Mn c At least one of O2, wherein 0.02≤x1≤0.15, 0.01≤y1≤0.1, 0.05≤x2≤0.95, 0≤b≤0.5, and a+b+c=1.

[0021] In some embodiments, a base layer is further disposed on the surface of the positive electrode substrate material, the coating layer is located on the surface of the base layer, and the base layer contains a lithium compound.

[0022] In some embodiments, a base layer is further disposed on the surface of the positive electrode substrate material, and the coating layer is located on the surface of the base layer. The base layer includes LiNbO3, LiAlO2, Li2SiO3, Li2ZrO3, Li3PO4, Li3BO3, and Li 1.3 Al 0.3Ti 1.7 At least one of (PO4)3.

[0023] In some embodiments, the mass gain of the composite cathode material stored at a -30°C dew point for 6 hours is less than 0.17%.

[0024] In some embodiments, the loose packing density of the composite cathode material is 0.54–0.75 g / cc.

[0025] In some embodiments, the battery corresponding to the composite cathode material has an initial charge-discharge efficiency greater than 82% under conditions of 0.1C and 1.9V to 3.7V.

[0026] In some embodiments, the battery corresponding to the composite cathode material retains more than 88% of its capacity after 50 cycles at 0.33C.

[0027] The preparation method of the composite cathode material as described above includes the following steps:

[0028] Get [N + (CH3)3R]Z - A coating system formed by halide precursor materials and solvents.

[0029] The coating system is mixed with the positive electrode matrix material to obtain a hybrid system.

[0030] The mixture is subjected to heat treatment.

[0031] In some implementations, the [N] + (CH3)3R]Z - In this context, R is -C n H 2n+1 n≥9, Z includes BF4 - FSI - TFSI - and PF6 - At least one of them.

[0032] In some embodiments, the halide precursor material includes lithium halide and Q halide, wherein Q includes at least one of In, Y, Zr, Sc and Er.

[0033] In some embodiments, the solvent is selected from polar solvents, including at least one of water, ethylenediamine, acetonitrile, methanol, ethanol, acetone, tetrahydrofuran, and isopropanol.

[0034] In some embodiments, the preparation method of the coating system specifically includes: [N + (CH3)3R]Z - The dispersion and the halide precursor material solution are mixed.

[0035] In some implementations, the [N] + (CH3)3R]Z - The mass percentage of the positive electrode substrate material is 0.01% to 0.5%.

[0036] In some embodiments, the halide electrolyte formed by the halide precursor material accounts for 0.1% to 2% of the mass percentage of the positive electrode matrix material.

[0037] In some embodiments, the solid mass content in the mixture is ≥50%.

[0038] In some embodiments, the positive electrode substrate material is coated with a base material before being mixed with the coating system to form a base layer on the surface of the positive electrode substrate material.

[0039] In some embodiments, the heat treatment temperature is 150–500°C, and the heat treatment time is 4–10 hours.

[0040] In some embodiments, the atmosphere for the heat treatment is selected from at least one of air, oxygen, and nitrogen, preferably air with carbon dioxide removed.

[0041] In some embodiments, the heat-treated material undergoes post-processing, including cooling, sieving, and demagnetization. In some embodiments, the material is removed after cooling to a temperature ≤95°C; in some embodiments, the dew point of the post-processing environment is ≤-20°C.

[0042] In some embodiments, the ambient dew point during the preparation of the coating system and the mixture system is ≤-10℃.

[0043] A positive electrode sheet includes a positive current collector and a positive electrode layer located on at least one side surface thereon, wherein the positive electrode layer contains the composite positive electrode material or a composite positive electrode material prepared by the method for preparing the composite positive electrode material.

[0044] In some embodiments, the composite cathode material has a mass content of ≥70% in the cathode layer.

[0045] In some embodiments, the positive electrode layer further comprises a sulfide solid electrolyte, a conductive agent, and a binder; the sulfide solid electrolyte in the positive electrode layer has a mass content of 20% to 25%.

[0046] In some embodiments, the particle size D50 of the sulfide electrolyte is 0.5 to 8 μm.

[0047] In some embodiments, the porosity of the positive electrode sheet after rolling is ≤25%.

[0048] A battery comprising the aforementioned positive electrode.

[0049] In some embodiments, the battery further includes a negative electrode and a sulfide electrolyte membrane.

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0051] (1) In the composite cathode material of the present invention, the large organic cation of the modifying group -N(CH3)3R can encapsulate the halide electrolyte through steric hindrance, reducing the polar solvent and metal ions (such as Y) 3+ In 3+ The -N(CH3)3R modified coating layer has excellent hydrophobicity and smoothness. -N(CH3)3R combines with the halide ions of halides through strong electrostatic interaction to form a uniform and dense modification layer on the halide electrolyte. Under the protection of hydrophobic long-chain alkyl groups, the composite cathode material can exist stably in an environment with high moisture content, breaking through the barrier that traditional halide electrolyte coated cathodes need to be prepared and applied in a harsh dry environment. The non-polar properties of long-chain alkyl R can significantly reduce the surface energy of cathode materials, reduce the adhesion between cathode materials and between cathode materials and sulfide electrolytes, making the contact surfaces easier to slide. This can increase the loose packing density of cathode materials, reduce the porosity of the electrode sheets, and improve the energy density of sulfide solid-state lithium-ion batteries. The -N(CH3)3R modified halide electrolyte coating layer has high ionic conductivity, low Young's modulus and oxidation resistance, which can effectively solve the problems of space charge layer, interface reaction and contact between cathode materials and sulfide electrolytes, and improve the capacity, rate performance and cycle stability of sulfide solid-state lithium-ion batteries.

[0052] (2) The preparation method of the composite cathode material of the present invention is simple and easy to implement, by using long-chain alkyl quaternary ammonium salt [N + (CH3)3R]Z - , Halogen precursor materials and solvents are mixed, [N + (CH3)3R]Z - The positive charge N in + (CH3)3R combines with halide ions of halides through strong electrostatic interaction. After heat treatment, N + (CH3)3R is uniformly and densely modified on the surface of the halide electrolyte, N + (CH3)3R and halide electrolyte form a coating layer on the surface of the cathode substrate material. This coating layer has high ionic conductivity, low Young's modulus and oxidation resistance, which can effectively improve the electrochemical performance of the cathode substrate material.

[0053] (3) The positive electrode sheet of the present invention has suitable porosity, high energy density, and excellent structural stability. The battery obtained by the positive electrode sheet (especially the sulfide solid lithium-ion battery) has high capacity, high rate performance and high cycle stability. Attached Figure Description

[0054] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram of the composite cathode material in Embodiment 1 of the present invention;

[0056] Figure 2 This is a scanning electron microscope image of the composite cathode material in Example 1 of the present invention;

[0057] Figure 3 This is the energy dispersive spectroscopy (EDS) analysis diagram of the composite cathode material in Example 1 of the present invention;

[0058] Figure 4 The charge-discharge curve of the battery obtained from the composite cathode material in Example 1 of the present invention is shown.

[0059] Figure 5 This is a cycle retention rate diagram of the composite cathode material in Example 1 of the present invention.

[0060] Figure label:

[0061] 1-Positive electrode substrate material, 2-Coating layer, 201-Halide electrolyte, 202-Modifying group. Detailed Implementation

[0062] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0063] According to one aspect of the present invention, the present invention relates to a composite cathode material, comprising a cathode substrate material and a coating layer disposed on the surface of the cathode substrate material, the coating layer comprising a halide electrolyte and a modifying group -N(CH3)3R, wherein R is -C n H 2n+1n≥9, for example, 9, 10, 11, 12, 13, 14, 15, 16, 17, 20, 22, 25, 30, 32, etc.

[0064] In the composite cathode material of this invention, the large organic cation of the modifying group -N(CH3)3R can encapsulate the halide electrolyte through steric hindrance, reducing the interaction between polar solvents and metal ions (such as Y). 3+ In 3+ The -N(CH3)3R-modified coating layer exhibits hydrophobicity and smoothness unprecedented for halide electrolytes. -N(CH3)3R binds to halide ions through strong electrostatic interactions, forming a uniform and dense modification layer on the halide electrolyte. Protected by the hydrophobic long-chain alkyl group, the composite cathode material can remain stable in environments with high moisture content, overcoming the barrier that traditional halide electrolyte-coated cathodes require preparation and application under harsh dry conditions. The non-polar properties of long-chain alkyl Rs can significantly reduce the surface energy of cathode materials, reduce the adhesion between cathode materials and between cathode materials and sulfide electrolytes, making the contact surfaces easier to slide, thereby increasing the loose packing density of cathode materials, reducing the porosity of the electrode sheets, and improving the energy density of sulfide solid-state lithium-ion batteries. The -N(CH3)3R modified halide electrolyte coating layer has high ionic conductivity, low Young's modulus and oxidation resistance, which can effectively solve the problems of space charge layer, interface reaction and contact between cathode materials and sulfide electrolytes, and improve the capacity, rate performance and cycle stability of sulfide solid-state lithium-ion batteries.

[0065] In some embodiments, n satisfies: 9≤n≤30. The number of carbon atoms n in the long-chain alkyl group R of the present invention is preferably 9 to 16, which is beneficial to balancing hydrophobicity and steric hindrance. If the value of n is too small, the hydrophobicity is insufficient; if the value of n is too large, it is not conducive to lithium ion diffusion.

[0066] In some embodiments, R is a straight chain or contains at least one branch, i.e., it can be a straight-chain alkyl group or a branched alkyl group, and the branch is located at the ω-2 to ω-6 positions of R (the branch is attached to the second to sixth carbon from the end of the main chain). Adjusting the molecular arrangement density enhances the compactness of the coating layer. In some embodiments, the branch is derived from at least one of methyl, ethyl, propyl, and isopropyl groups; the branch can increase intermolecular steric hindrance and inhibit electrolyte permeation.

[0067] In some embodiments, the chemical formula of the halide electrolyte includes Li z Q q M dWherein, 2≤z≤3 (z, for example, 2, 2.5, 3, etc.), 0.5≤q≤1 (q, for example, 0.5, 0.6, 0.7, 0.8, or 1), 3≤d≤6 (3, 4, 5, or 6), Q includes at least one of In, Y, Zr, Sc, and Er, and M is selected from halogens. In some embodiments, the halide electrolyte includes Li3InCl6, Li3YCl6, Li3YBr6, Li2ZrCl6, Li3ScCl6, Li3ErCl3, Li3YCl3Br3, Li 2.5 Zr 0.5 In 0.5 Cl6 and Li2Sc 1 / 3 In 1 / At least one of 3Cl4. The halide electrolyte of the present invention provides a three-dimensional lithium-ion transport channel and has a stable crystal structure.

[0068] In some embodiments, the mass content of the modifying group -N(CH3)3R in the composite cathode material is 0.01% to 0.5%, for example, 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or any value within a range of both. By employing an appropriate proportion of the modifying group -N(CH3)3R, this invention is more conducive to ensuring the interfacial and electrical properties of the coating layer, thereby better improving the electrochemical performance of the cathode substrate material.

[0069] In some embodiments, the mass ratio of the halide electrolyte to the modifying group -N(CH3)3R is (10-600):1, such as 10:1, 100:1, 200:1, 300:1, 400:1, 500:1 or 600:1. This invention optimizes the mass ratio of the halide electrolyte to the modifying group -N(CH3)3R so that the two work synergistically to improve the interfacial stability of the coating layer.

[0070] In some embodiments, the cathode substrate material of the present invention includes LiNi. 1-x1-y1 Co x1 Mn y1 O2, LiCoO2, LiNi 0.5 Mn 1.5 O4 and x2Li2MnO3·(1-x2)LiNi a Co b Mn cAt least one of O2, wherein 0.02≤x1≤0.15 (x1 is, for example, 0.02, 0.05, 0.1, 0.15, etc.), 0.01≤y1≤0.1 (y1 is, for example, 0.01, 0.02, 0.05, 0.08, 0.1, etc.), 0.05≤x2≤0.95 (x2 is, for example, 0.05, 0.1, 0.2, 0.5, 0.7, 0.8, 0.95, etc.), 0≤b≤0.5 (b is, for example, 0.1, 0.2, 0.3, 0.5, etc.), a+b+c=1. The positive electrode substrate material of the present invention can be one or more of the above. LiNi 1-x1- y1 Co x1 Mn y1 O2 can suppress the reaction between residual alkali on the surface and the electrolyte by coating, thus alleviating gas production. x2Li2MnO3·(1-x2)LiNi a Co b Mn c O2 can mitigate structural collapse caused by oxygen evolution during the first charge and discharge cycle by being coated with a coating layer.

[0071] In some embodiments, a base layer is further disposed on the surface of the positive electrode substrate material, and the coating layer is located on the surface of the base layer. The base layer contains a lithium compound. This invention, by providing a base layer between the positive electrode substrate material and the coating layer, facilitates enhanced bonding between the coating layer and the substrate material. Furthermore, the base layer can provide additional lithium-ion transport paths and reduce interfacial impedance. In some embodiments, the base layer includes LiNbO3, LiAlO2, Li2SiO3, Li2ZrO3, Li3PO4, Li3BO3, and Li 1.3 Al 0.3 Ti 1.7 One or more combinations of (PO4)3, such as the combination of LiAlO2 and Li2SiO3, the combination of Li2SiO3, Li2ZrO3 and Li3PO4, etc., are preferred by the present invention, which is more conducive to improving the electrochemical performance of the cathode material.

[0072] In some embodiments, the coefficient of friction of the composite cathode material is 0.05 to 0.5, preferably 0.1 to 0.3. The coefficient of friction involved in this invention is the microscopic coefficient of friction of the cathode material, which can be measured by atomic force microscopy (AFM): in transverse force microscopy (LFM) mode, a probe is traversed across the material surface with a constant load (1 to 100 nN), and the local frictional force is calculated from the probe deflection signal, which is then converted to obtain the coefficient of friction. The composite cathode material of this invention has a low coefficient of friction, which can improve material fluidity, facilitate the uniform coating of the electrode slurry prepared from it, and reduce particle agglomeration.

[0073] In some embodiments, the composite cathode material is a monocrystalline cathode material and / or a polycrystalline cathode material. Monocrystalline materials can reduce grain boundary cracks and suppress particle breakage during cycling. Polycrystalline materials compensate for the high reactivity at grain boundaries through a coating layer. In some embodiments, the particle size D50 of the composite cathode material is 1.8–9 μm, for example, 1.8 μm, 2 μm, 3 μm, 4 μm, 5 μm, 7 μm, 9 μm, or any value in between. The composite cathode material of the present invention has a suitable D50 particle size, which is beneficial for improving the ion diffusion rate and enhancing electrochemical performance.

[0074] In some embodiments, the mass gain of the composite cathode material stored at a -30°C dew point for 6 hours is less than 0.17%, for example, 0.05%, 0.1%, 0.12%, 0.15%, 0.7%, etc. The coating layer of the present invention can impart excellent hydrophobicity to the composite cathode material, improving its stability in environments with high moisture content.

[0075] In some embodiments, the loose packing density of the composite cathode material is 0.54–0.75 g / cc, for example, 0.54 g / cc, 0.6 g / cc, 0.65 g / cc, 0.7 g / cc, 0.75 g / cc, etc. The composite cathode material of the present invention has a suitable loose packing density, thereby ensuring suitable electrode porosity and balancing lithium-ion transport and active material loading.

[0076] In some embodiments, the battery corresponding to the composite cathode material exhibits an initial charge-discharge efficiency greater than 82% under 0.1C and 1.9V–3.7V conditions, such as 83%, 84%, 85%, 86%, 88%, and 90%. The coating layer of this invention can reduce irreversible phase transitions, improve the utilization rate of active materials, and enable the battery to have high charge-discharge efficiency.

[0077] In some embodiments, the battery corresponding to the composite cathode material exhibits a capacity retention rate greater than 88% after 50 cycles at 0.33C, such as 88%, 90%, 92%, 93%, 94%, 95%, or any value within a range of both. The coating layer of this invention can suppress transition metal dissolution and CEI thickening, which is beneficial for maintaining the integrity of the electrode structure, slowing down capacity decay, and resulting in a battery with high capacity retention rate corresponding to the composite cathode material.

[0078] According to another invention of the present invention, the present invention also relates to a method for preparing the composite cathode material as described above, comprising the following steps:

[0079] Get [N + (CH3)3R]Z - A coating system formed by halide precursor materials and solvents.

[0080] The coating system is mixed with the cathode substrate material to obtain a hybrid system.

[0081] The mixed system is subjected to heat treatment.

[0082] The preparation method of the composite cathode material of the present invention is simple and easy to implement, and involves using a long-chain alkyl quaternary ammonium salt [N + (CH3)3R]Z - , Halogen precursor materials and solvents are mixed, [N + (CH3)3R]Z - The positive charge N in + (CH3)3R combines with halide ions of halides through strong electrostatic interaction. After heat treatment, N + (CH3)3R is uniformly and densely modified on the surface of the halide electrolyte, N + (CH3)3R and halide electrolyte form a coating layer on the surface of the cathode substrate material. This coating layer has high ionic conductivity, low Young's modulus and oxidation resistance, which can effectively improve the electrochemical performance of the cathode substrate material.

[0083] In some embodiments, the preparation method of the coating system specifically includes: [N + (CH3)3R]Z - The dispersion and the halide precursor material solution are mixed. Specifically, the halide precursor and solvent are mixed to obtain the halide precursor material solution; [N + (CH3)3R]Z - When mixed with a solvent, [N] is obtained. + (CH3)3R]Z - Dispersion; [N] + (CH3)3R]Z - The dispersion and the halide precursor material solution are stirred and mixed to obtain the coating system.

[0084] In some embodiments, the solvent is selected from polar solvents, including at least one of water, ethylenediamine, acetonitrile, methanol, ethanol, acetone, tetrahydrofuran, and isopropanol. The use of polar solvents in this invention facilitates better dissolution of halide precursor materials and [N] + (CH3)3R]Z - Better dispersion. [N] + (CH3)3R]Z - The polar solvents in the dispersion and the halide precursor material solution can be the same or different.

[0085] In this invention, long-chain alkyl quaternary ammonium salts [N + (CH3)3R]Z -Possessing hydrophobic long-chain alkyl ends and hydrophilic quaternary ammonium salt ends, it functions as a surfactant, reducing the surface tension of the solvent. When an aqueous solution of the long-chain alkyl quaternary ammonium salt is stirred, a typical surfactant characteristic—foaming—occurs. The inventors unexpectedly discovered that when an aqueous dispersion of the long-chain alkyl quaternary ammonium salt is added to an aqueous solution of a halide precursor and stirred, the foaming phenomenon disappears, forming a clear and transparent solution. The reasons for this may include: the long-chain alkyl quaternary ammonium salt [N...] + (CH3)3R]Z - Because it contains easily dissociable anions Z - [N] + [CH3)3R] cation and Z - After dissociation, it will spontaneously form a strong electrostatic bond with the halide anions in the halide precursor aqueous solution, and be dragged into the solution by the easily free halide anions, thus forming a clear and transparent solution.

[0086] In some implementations, the [N] + (CH3)3R]Z - In this context, R is -C n H 2n+1 n≥9, preferably, n satisfies: 9≤n≤30, R is a straight chain or contains at least one branch, i.e., it can be a straight-chain alkyl group or a branched alkyl group, and the branch is located at the ω-2 to ω-6 positions of R (the branch is attached to the second to sixth carbon from the end of the main chain). Z includes BF4. - FSI - (bis(fluorosulfonylimide) anion), TFSI - (bis(trifluoromethanesulfonyl)imide anion) and PF6 - At least one of them. Due to TFSI - and FSI - The negative charge is more dispersed, and the resulting long-chain alkyl quaternary ammonium salt is easily dissociated, preferably Z. - Taken from TFSI - and FSI - At least one of them.

[0087] In some implementations, [N] + (CH3)3R]Z - The preparation method is based on the synthesis reaction of quaternary ammonium salt and obtained by anion exchange, including: (1) generating [N] by nucleophilic substitution reaction of alkyl bromide (RBr) with trimethylamine (N(CH3)3). + (CH3)3R]Br - (2) Through LiZ(Z includes BF4) - FSI - TFSI - or PF6 -Anion exchange is performed on an aqueous solution of [N], and LiBr precipitates due to its low solubility, forming [N]. + (CH3)3R]Z - .

[0088] In some implementations, [N] + (CH3)3R]Z - The preparation method specifically includes:

[0089] (a) Alkyl bromide (RBr) was dissolved in anhydrous acetonitrile, and trimethylamine solution was slowly added dropwise while maintaining a molar ratio of 1:1.1. The mixture was heated to 75–85 °C and refluxed, with stirring for 20–25 h. After cooling, the acetonitrile was removed by vacuum distillation to obtain a viscous solid phase. The remaining reactants were removed by washing with cold diethyl ether to obtain [N...] + (CH3)3R]Br - .

[0090] (b) [N + (CH3)3R]Br - Dissolve in 90–110 mL of deionized water. Add LiZ(Z including BF4) - FSI - TFSI - or PF6 - Dissolve in 90-100 mL of deionized water and slowly add dropwise to the above [N] + (CH3)3R]Br - The solution was cooled in an ice bath to control the exothermic reaction. After stirring for 10–15 h, the precipitate was removed by filtration. Dichloromethane was added to the filtrate to extract the product, and the solvent was removed by rotary evaporation to obtain [N]. + (CH3)3R]TFSI - .

[0091] In some embodiments, bis(trifluoromethanesulfonyl)imine undecyltrimethylammonium ([N + (CH3)3C 11 H 23 TFSI - The preparation method of ) specifically includes:

[0092] (1) Undecyl bromide was dissolved in anhydrous acetonitrile, and trimethylamine solution was slowly added dropwise while maintaining a molar ratio of 1:1.1. The mixture was heated to 80°C and refluxed, and stirred for 24 h. After cooling, the acetonitrile was removed by vacuum distillation to obtain a viscous solid phase. The remaining reactants were removed by washing with cold diethyl ether to obtain [N + (CH3)3C 11 H 23 ]Br - .

[0093] (2) [N + (CH3)3C11 H 23 ]Br - Dissolve in 100 mL of deionized water. Separately, dissolve LiTFSI in 100 mL of deionized water and slowly add it dropwise to the quaternary ammonium salt solution, cooling in an ice bath to control exothermic reactions. Stir for 12 h, filter to remove the precipitate; add dichloromethane to the filtrate to extract the product, and remove the solvent by rotary evaporation to obtain [N...]. + (CH3)3C11H 23 TFSI - .

[0094] In some embodiments, the [N] involved in the various embodiments of the present invention + (CH3)3R]Br - Please refer to the above [N] + (CH3)3C 11 H 23 TFSI - The preparation can be carried out by adjusting the type of alkyl bromide (RBr).

[0095] In some embodiments, the halide precursor material includes lithium halide and Q halide, where Q includes at least one of In, Y, Zr, Sc, and Er. The lithium halide includes at least one of LiCl and LiBr. The Q halide includes at least one of InCl3, YCl3, ZrCl4, ScCl3, and ErCl3. The lithium halide and Q halide are based on the chemical formula of the halide electrolyte described above. z Q q M d Use an appropriate molar ratio for mixing.

[0096] In some embodiments, the positive electrode substrate material is coated with a base material before being mixed with the coating system to form a base layer on the surface of the positive electrode substrate material. The base material includes oxides and hydroxides of Nb, Al, Si, and Zr (e.g., Nb₂O₅, Al₂O₃, Al(OH)₃, SiO₂, ZrO₂, Zr(OH)₄), and at least one of ammonium hydrogen phosphate, H₃BO₃, and alumina-titanium oxide-ammonium hydrogen phosphate. The present invention uses the above-mentioned base material for coating, which can form a suitable base layer on the surface of the positive electrode substrate material, enhance the bonding force between the coating layer and the substrate material, and simultaneously provide additional lithium-ion transport paths and reduce interfacial impedance.

[0097] In some implementations, the [N] + (CH3)3R]Z -The mass percentage of the positive electrode substrate material is 0.01% to 0.5%, for example, 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc. This invention achieves this by using a suitable proportion of [N] + (CH3)3R]Z - This ensures the interfacial and electrical properties of the coating layer, which in turn helps to improve the electrochemical performance of the cathode substrate material.

[0098] In some embodiments, the halide electrolyte formed from the halide precursor material accounts for 0.1% to 2% of the mass percentage of the cathode matrix material, for example, 0.1%, 0.5%, 0.8%, 1%, 1.5%, or 2%. This invention improves the coating effect and the electrochemical performance of the coating layer by using a suitable proportion of halide electrolyte to better graft a suitable proportion of modifying groups.

[0099] In some embodiments, the solid mass content in the mixed system is ≥50%, such as 50%, 60%, 70%, 80%, 85%, etc., preferably ≥80%. The appropriate solid mass content in the mixed system of the present invention is beneficial to ensuring the mixing effect, beneficial to coating, and forming a coating layer with better performance.

[0100] In some embodiments, the heat treatment temperature is 150–500°C, for example 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 500°C, etc., and the heat treatment time is 4–10 hours, for example 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 10 hours, etc. In some embodiments, the atmosphere for the heat treatment is selected from at least one of air, oxygen, and nitrogen, preferably air with carbon dioxide removed. In some embodiments, the heating rate is 1–8°C / min, for example 1°C / min, 5°C / min, 8°C / min, etc. After heat treatment, the solvent is removed, and a dense halide electrolyte coating layer is uniformly formed on the surface of the positive electrode material. Due to the interaction of halide ions with [N... + The strong binding effect of [(CH3)3R] modifies the surface of the halide electrolyte with a uniformly distributed layer of -N(CH3)3R; the present invention uses appropriate heat treatment conditions, which are more conducive to the coating effect, so that the modified long-chain alkyl functional group R endows the coating layer with better hydrophobic and smooth properties.

[0101] In some embodiments, the heat-treated material undergoes post-processing, including cooling, sieving, and demagnetization, followed by packaging after demagnetization. Preferably, the material is removed after cooling to a temperature ≤95℃ (e.g., 30℃, 50℃, 60℃, 85℃, etc.); preferably, the dew point of the post-processing environment is ≤-20℃, and more preferably ≤-30℃. Dew point refers to the temperature at which air is cooled to saturation (relative humidity reaches 100%) under constant pressure. When water vapor in the air reaches this temperature, it condenses into liquid water (dew) or solid water (frost), the specific form depending on whether the dew point is higher or lower than the freezing point; the lower the dew point, the lower the moisture content in the air.

[0102] In some embodiments, the ambient dew point during the preparation of the coating system and the mixture system is ≤-10℃, preferably ≤-20℃. Controlling the ambient dew point plays a crucial role in product quality and process stability during material preparation.

[0103] According to another aspect of the present invention, the present invention also relates to a positive electrode sheet comprising a positive current collector and a positive electrode layer located on at least one side surface thereon, the positive electrode layer comprising the composite positive electrode material described above or a composite positive electrode material prepared by the method for preparing the composite positive electrode material described above.

[0104] The positive electrode of the present invention has suitable porosity, high energy density, and excellent structural stability.

[0105] In some embodiments, the composite cathode material has a mass content of ≥70% in the cathode layer, such as 70%, 75%, 80%, 85%, etc. A suitable mass content of the composite cathode material in the cathode layer is more conducive to ensuring the structural stability and electrochemical performance of the cathode layer.

[0106] In some embodiments, the positive electrode layer further comprises a sulfide solid electrolyte, a conductive agent, and a binder. The sulfide solid electrolyte has a mass content of 20% to 25% in the positive electrode layer, for example, 20%, 22%, 25%, etc. The components work in harmony to improve the electrochemical performance of the positive electrode layer.

[0107] In some embodiments, the sulfide electrolyte includes Li7P3S. 11 Li3PS4, Li6PS5Cl, Li 10 GeP2S 12 Li6PS5Br, Li 5.5 PS 4.5 Cl 1.5 and Li 5.3 PS 4.3 Cl 0.8 Br 0.7 One or more of them, such as Li7P3S11 And Li3PS4, such as Li6PS5Br, Li 5.5 PS 4.5 Cl 1.5 and Li 5.3 PS 4.3 Cl 0.8 Br 0.7 In some embodiments, the particle size D50 of the sulfide electrolyte is 0.5–8 μm, for example, 0.5 μm, 1 μm, 2 μm, 5 μm, or 8 μm. The use of the aforementioned suitable particle size of the sulfide electrolyte in this invention is beneficial for reducing interfacial impedance and improving transport efficiency.

[0108] In some embodiments, the conductive agent is selected from one or more of vapor-grown carbon fibers (VGCF), Super-P, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, Ketjen black, and acetylene black, such as a combination of multi-walled carbon nanotubes and graphene, or a combination of graphene and Ketjen black. The use of the above-mentioned conductive agents in this invention is more conducive to improving the conductivity of the positive electrode layer.

[0109] In some embodiments, the adhesive is selected from one or more of polyvinyl alcohol, hydrogenated nitrile rubber, styrene-butadiene rubber, polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF), such as a combination of polyvinyl alcohol and hydrogenated nitrile rubber. The use of the above-mentioned adhesive in this invention ensures the adhesion between the positive electrode layer and the positive electrode current collector.

[0110] In some embodiments, the positive current collector is either aluminum foil or carbon-coated aluminum foil.

[0111] In some embodiments, due to the excellent surface smoothness of the composite cathode material, the friction between composite cathode materials and between the composite cathode material and the sulfide electrolyte is small, and the porosity of the cathode sheet after rolling is ≤25%, such as 18%, 20%, 22%, etc., preferably ≤20%.

[0112] In some embodiments, the preparation of the positive electrode sheet includes: fully mixing the positive electrode material, conductive carbon, sulfide electrolyte and binder in a certain proportion, and then combining it with the positive electrode current collector by a wet or dry method.

[0113] According to another aspect of the invention, the invention also relates to a battery comprising the aforementioned positive electrode.

[0114] The composite cathode material of this invention produces batteries with excellent capacity, cycle performance, and rate performance.

[0115] In some embodiments, the battery further includes a negative electrode and a sulfide electrolyte membrane. In some embodiments, the negative electrode is selected from at least one of lithium metal alloy, lithium indium alloy, lithium metal, graphite, and Si-C composite negative electrode. In some embodiments, the sulfide electrolyte of the sulfide electrolyte membrane is Li7P3S. 11 Li3PS4, Li6PS5Cl, Li 10 GeP2S 12 Li 10 SnP2S 12 Li6PS5Br, Li 5.5 PS 4.5 Cl 1.5 Li 5.3 PS 4.3 Cl 0.8 Br 0.7 One or more.

[0116] The composite cathode material of the present invention is particularly suitable for sulfide solid lithium-ion batteries, which can improve their energy density. The long-chain alkyl-modified halide electrolyte coating layer has high ionic conductivity, low Young's modulus and oxidation resistance, which can effectively solve the problems of space charge layer, interface reaction and contact between composite cathode material and sulfide electrolyte, and can improve the capacity, rate performance and cycle stability of sulfide solid lithium-ion batteries.

[0117] The following explanation, combined with specific embodiments and comparative examples, further illustrates the point.

[0118] Example 1

[0119] A method for preparing a composite cathode material includes the following steps:

[0120] (1) In an environment with a dew point of -20℃, weigh InCl3 and LiCl in a molar ratio of 1:3, dissolve them in deionized water to obtain an aqueous solution of LiCl·InCl3. Weigh an appropriate amount of bis(trifluoromethanesulfonyl)imine undecyltrimethylammonium, i.e. [N + (CH3)3C 11 H 23 TFSI - Add to deionized water and stir to obtain [N] + (CH3)3C 11 H 23 TFSI - Aqueous dispersion of LiCl·InCl3. An aqueous solution of LiCl·InCl3 and [N... + (CH3)3C 11 H 23 TFSI - The aqueous dispersion was mixed and stirred to obtain the coating system.

[0121] (2) Weigh out an appropriate amount of LiNi 0.90 Co 0.05 Mn 0.05 O2 material was added to the coating system and stirred at 500 rpm for 5 minutes to obtain a solid-liquid mixture with a solid content of 90%. LiNi 0.90 Co 0.05 Mn 0.05 O2:Li3InCl3:[N + (CH3)3C 11 H 23 TFSI - The mass ratio is 100:1:0.05.

[0122] (3) The solid-liquid mixture was heated to 200°C at a heating rate of 3°C / min in an air atmosphere free of carbon dioxide, and annealed after holding at the temperature for 8 hours to obtain the composite cathode material.

[0123] A schematic diagram of the composite cathode material is shown below. Figure 1 As shown, it includes a positive electrode substrate material 1 and a coating layer 2 disposed on the surface of the positive electrode substrate material 1. The coating layer 2 includes a halide electrolyte 201 and a modification group 202.

[0124] Example 2

[0125] A method for preparing a composite cathode material includes the following steps:

[0126] (1) In an environment with a dew point of -20℃, weigh YCl3 and LiCl in a molar ratio of 1:3, dissolve them in deionized water to obtain an aqueous solution of LiCl·YCl3. Weigh an appropriate amount of bis(trifluoromethanesulfonyl)imine undecyltrimethylammonium, i.e. [N + (CH3)3C 11 H 23 TFSI - Add to deionized water and stir to obtain [N] + (CH3)3C 11 H 23 TFSI - Aqueous dispersion of LiCl·YCl3. An aqueous solution of LiCl·YCl3 and [N... + (CH3)3C 11 H 23 TFSI - The aqueous dispersion was mixed and stirred to obtain the coating system.

[0127] (2) Weigh out an appropriate amount of LiNi 0.90 Co 0.05 Mn 0.05O2 material was added to the coating system and stirred at 500 rpm for 5 minutes to obtain a solid-liquid mixture with a solid content of 90%. LiNi 0.90 Co 0.05 Mn 0.05 O2:Li3YCl3:[N + (CH3)3C 11 H 23 TFSI - The mass ratio is 100:1:0.05.

[0128] (3) The solid-liquid mixture was heated to 250°C at a heating rate of 3°C / min in an air atmosphere free of carbon dioxide, and annealed after holding at the temperature for 6 hours to obtain the composite cathode material.

[0129] Example 3

[0130] A method for preparing a composite cathode material includes the following steps:

[0131] (1) In an environment with a dew point of -20℃, weigh InCl3 and LiCl in a molar ratio of 1:3, dissolve them in deionized water to obtain an aqueous solution of LiCl·InCl3. Weigh an appropriate amount of bis(trifluoromethanesulfonyl)imide cetyltrimethylammonium, i.e. [N + (CH3)3C 16 H 33 TFSI - Add to deionized water and stir to obtain [N] + (CH3)3C 16 H 33 TFSI - Aqueous dispersion; aqueous solution of LiCl·InCl3 and [N + (CH3)3C 16 H 33 TFSI - The aqueous dispersion was mixed and stirred to obtain the coating system.

[0132] (2) Weigh out an appropriate amount of LiNi 0.8 Co 0.10 Mn 0.1 O2 material was added to the coating system and stirred at 600 rpm for 10 min to obtain a solid-liquid mixture with a solid content of 95%. LiNi 0.8 Co 0.10 Mn 0.1 O2:Li3InCl3:[N + (CH3)3C 16 H 33 TFSI - The mass ratio is 100:1.5:0.04.

[0133] (3) The solid-liquid mixture was heated to 200°C at a heating rate of 3°C / min in an oxygen atmosphere, and annealed after holding at the temperature for 8 hours to obtain the composite cathode material.

[0134] Example 4

[0135] A method for preparing a composite cathode material includes the following steps:

[0136] (1) In an environment with a dew point of -20℃, weigh InCl3 and LiCl in a molar ratio of 1:3, dissolve them in deionized water to obtain an aqueous solution of LiCl·InCl3. Weigh an appropriate amount of bis(trifluoromethanesulfonyl)imine undecyltrimethylammonium, i.e. [N + (CH3)3C 11 H 23 TFSI - Add to deionized water and stir to obtain [N] + (CH3)3C 11 H 23 TFSI - Aqueous dispersion of LiCl·InCl3. An aqueous solution of LiCl·InCl3 and [N... + (CH3)3C 11 H 23 TFSI - The aqueous dispersion was mixed and stirred to obtain the coating system.

[0137] (2) Weigh out an appropriate amount of LiNi 0.90 Co 0.05 Mn 0.05 O2 material was mixed with 2000 ppm ZrO2 and calcined at 600℃ for 6 h in an oxygen atmosphere to obtain Li2ZrO3-coated LiNi. 0.90 Co 0.05 Mn 0.05 O2 materials.

[0138] (3) LiNi coated with Li2ZrO3 0.90 Co 0.05 Mn 0.05 O2 material was added to the coating system and stirred at 500 rpm for 5 min to obtain a solid-liquid mixture with a solid content of 90%. Li2ZrO3 coated LiNi 0.90 Co 0.05 Mn 0.05 O2:Li3InCl3:[N + (CH3)3C 11 H 23 TFSI - The mass ratio is 100:0.5:0.02.

[0139] (4) The solid-liquid mixture was heated to 250°C at a heating rate of 3°C / min in an air atmosphere free of carbon dioxide, and annealed after holding at the temperature for 6 hours to obtain the composite cathode material.

[0140] Example 5

[0141] A method for preparing a composite cathode material includes the following steps:

[0142] (1) In an environment with a dew point of -20℃, InCl3, ScCl3 and LiCl were weighed in a molar ratio of 1:1:6 and dissolved in ethanol to obtain an aqueous solution of InCl3·ScCl3·LiCl; an appropriate amount of bis(trifluoromethanesulfonyl)imine undecyltrimethylammonium, i.e. [N + (CH3)3C 11 H 23 TFSI - Add to ethanol and stir to obtain [N] + (CH3)3C 11 H 23 TFSI - An ethanol dispersion; an ethanol solution of InCl3·ScCl3·LiCl and [N + (CH3)3C 11 H 23 TFSI - The coating system was obtained by mixing and stirring the ethanol dispersion.

[0143] (2) Weigh out an appropriate amount of 0.3Li2MnO3·0.7LiNi 0.5 Co 0.04 Mn 0.46 O2 material was added to the coating system and stirred at 500 rpm for 5 min to obtain a solid-liquid mixture with a solid content of 95%. 0.3Li2MnO3·0.7LiNi 0.5 Co 0.04 Mn 0.46 O2:Li2Sc 1 / 3 In 1 / 3 Cl4:[N + (CH3)3C 11 H 23 TFSI - The mass ratio is 100:2:0.08.

[0144] (3) The solid-liquid mixture was heated to 200°C at a heating rate of 3°C / min in an oxygen atmosphere, and annealed after holding at the temperature for 8 hours to obtain the composite cathode material.

[0145] Example 6

[0146] A method for preparing a composite cathode material differs from that in Example 1 in that:

[0147] Long-chain alkyl quaternary ammonium salts [N + (CH3)3R]Z - The mixture uses bis(trifluoromethanesulfonyl)imide undecyltrimethylammonium and bis(trifluoromethanesulfonyl)imide hexadecyltrimethylammonium in a mass ratio of 3:1.

[0148] Example 7

[0149] A method for preparing a composite cathode material includes the following steps:

[0150] (1) In an environment with a dew point of -20℃, weigh InCl3 and LiCl in a molar ratio of 1:3, dissolve them in deionized water to obtain an aqueous solution of LiCl·InCl3. Weigh an appropriate amount of bis(trifluoromethanesulfonyl)imine triacontyltrimethylammonium, i.e. [N + (CH3)3C 30 H 61 TFSI - Add to deionized water and stir to obtain [N] + (CH3)3C 30 H 61 TFSI - Aqueous dispersion of LiCl·InCl3. An aqueous solution of LiCl·InCl3 and [N... + (CH3)3C 30 H 61 TFSI - The aqueous dispersion was mixed and stirred to obtain the coating system.

[0151] (2) Weigh out an appropriate amount of LiNi 0.90 Co 0.05 Mn 0.05 O2 material was added to the coating system and stirred at 500 rpm for 5 minutes to obtain a solid-liquid mixture with a solid content of 90%. LiNi 0.90 Co 0.05 Mn 0.05 O2:Li3InCl3:[N + (CH3)3C 30 H 61 TFSI - The mass ratio is 100:1:0.05.

[0152] (3) The solid-liquid mixture was heated to 200°C at a heating rate of 3°C / min in an air atmosphere free of carbon dioxide, and annealed after holding at the temperature for 8 hours to obtain the composite cathode material.

[0153] Comparative Example 1

[0154] A method for preparing a composite cathode material includes the following steps:

[0155] (1) In an environment with a dew point of -20℃, weigh InCl3 and LiCl in a molar ratio of 1:3, dissolve them in deionized water to obtain an aqueous solution of LiCl·InCl3.

[0156] (2) Weigh out an appropriate amount of LiNi 0.90 Co 0.05 Mn 0.05 O2 material was added to the above-mentioned LiCl·InCl3 aqueous solution and stirred at 500 rpm for 5 min to obtain a solid-liquid mixture with a solid content of 90%; LiNi 0.90 Co 0.05 Mn 0.05 The mass ratio of O2 to Li3InCl3 is 100:1.

[0157] (3) The solid-liquid mixture was heated to 200°C at a heating rate of 3°C / min in an air atmosphere free of carbon dioxide, and annealed after holding at the temperature for 8 hours to obtain the composite cathode material.

[0158] Comparative Example 2

[0159] A method for preparing a composite cathode material includes the following steps:

[0160] (1) In an environment with a dew point of -20℃, weigh InCl3 and LiCl in a molar ratio of 1:3, dissolve them in deionized water to obtain an aqueous solution of LiCl·InCl3; weigh an appropriate amount of pentyltrimethylammonium bromide, i.e., [N + (CH3)3C5H 11 ]Br - Add to deionized water and stir to obtain [N] + (CH3)3C5H 11 ]Br - Aqueous dispersion; aqueous solution of LiCl·InCl3 and [N + (CH3)3C5H 11 ]Br - The aqueous dispersion was mixed and stirred to obtain the coating system.

[0161] (2) Weigh out an appropriate amount of LiNi 0.90 Co 0.05 Mn 0.05 O2 material was added to the coating system and stirred at 500 rpm for 5 minutes to obtain a solid-liquid mixture with a solid content of 90%. LiNi 0.90 Co 0.05 Mn 0.05 O2:Li3InCl3:[N + (CH3)3C5H11 ]Br - The mass ratio is 100:1:0.05.

[0162] (3) The solid-liquid mixture was heated to 200°C at a heating rate of 3°C / min in an air atmosphere free of carbon dioxide, and annealed after holding at the temperature for 8 hours to obtain the composite cathode material.

[0163] Experimental Example 1

[0164] I. Performance Testing of Composite Cathode Materials

[0165] 1. Spectral Analysis

[0166] Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were performed on the composite cathode material of Example 1. The results are as follows: Figure 2 and Figure 3 As shown. SEM characterization revealed uniformly distributed long-chain alkyl-modified Li3InCl6 on the surface of the composite cathode material. EDS characterization showed that the In, Cl, and alkyl C elements of the halide were uniformly distributed.

[0167] 2. Test of the storage mass change rate of composite cathode materials

[0168] The composite cathode materials of each embodiment and comparative example were placed in a -30°C dew point environment and stored openly for 6 hours, and the mass change rate was tested. Among them, the composite cathode material of Comparative Example 1 was divided into two groups: one group was subjected to the above-mentioned storage mass change rate test; the other group was not placed in a -30°C dew point environment and no storage mass change rate test was performed.

[0169] 3. Loose packing density test

[0170] The Scott volumetric method was used for measurement: the powder flowed freely into the feeding box through the sieve, passed alternately through 4 glass plates with an inclination angle of 25°, and fell freely from a certain height through the funnel to fill the measuring cup. The result was calculated from the net weight of the powder and the volume of the measuring cup.

[0171] The performance test results of the composite cathode material are shown in Table 1.

[0172] Table 1 Performance test results of composite cathode materials

[0173]

[0174] As shown in Table 1, the mass growth rate of the composite cathode material in each embodiment of the present invention after being stored openly in a dew point environment at -30°C for 6 hours is less than 0.17%, indicating that the hydrophobic coating of the long-chain alkyl-modified halide can reduce the reaction with moisture under high dew point conditions; the composite cathode material has a suitable loose packing density (0.54~0.73 g / cc), which is beneficial for the cathode sheet to have a suitable porosity.

[0175] In Comparative Example 1, the composite cathode material of Group 1 showed a mass growth rate as high as 3.61% after being stored openly in a -30℃ dew point environment for 6 hours. This is because the Li3InCl3 coating layer absorbs moisture from the air, causing Li3InCl3 to decompose into InCl3·mH2O and LiCl·nH2O. The loose packing density of the composite cathode material of Group 1 in Comparative Example 1 was also relatively low.

[0176] The composite cathode material in Comparative Example 2 showed a mass growth rate of up to 2.91% after being stored in an open environment at -30°C dew point for 6 hours, indicating that short-chain alkyl groups cannot effectively make the coating layer hydrophobic, and the loose packing density of the composite cathode material is low.

[0177] II. Battery Performance Testing

[0178] Batteries were prepared using the composite cathode materials of each embodiment and comparative example, specifically including:

[0179] Composite cathode material, Li6PS5Cl, VGCF, and PTFE were weighed in a mass ratio of 75:23.8:1:0.2, and the four substances were thoroughly mixed. The mixture was then applied to a carbon-coated aluminum foil current collector using a dry roll forming process to prepare a cathode sheet with an areal density of 20 mg / cm³. 2 A sulfide solid-state lithium-ion battery was assembled by pressing the positive electrode sheet, Li6PS5Cl, and lithium-indium alloy sheet at 200MPa for 10 minutes.

[0180] The prepared battery was subjected to charge-discharge tests at 25°C and a current density of 0.1C, with a charge-discharge range of 1.9V to 3.7V. The charge-discharge curve of the sulfide solid-state lithium-ion battery obtained from the composite cathode material in Example 1 in the first cycle is shown below. Figure 4 As shown in the figure, the cycle capacity retention rate is as follows: Figure 5 As shown in Table 2, the charge-discharge efficiency of batteries obtained from the composite cathode materials in other embodiments and comparative examples, and the capacity retention rate after 50 cycles at 0.33C, are shown in Table 2.

[0181] Table 2 Battery Performance

[0182]

[0183]

[0184] As shown in Table 2, the composite cathode materials in the various embodiments of the present invention produce cathode sheets with relatively low porosity, not exceeding 22%, resulting in batteries with high energy density, high discharge efficiency, and high capacity retention. The energy density of a battery depends on its electrode characteristics. On the cathode side, high bulk density cathode materials correspond to low porosity cathodes, reflecting a lower electrode sheet thickness for the same cathode material loading. On the other hand, high specific capacity cathode materials reflect a higher capacity for the same cathode material loading. Therefore, the solution provided by the present invention can effectively improve the specific capacity and bulk density of cathode materials, thereby increasing the energy density of solid-state lithium-ion batteries.

[0185] The composite cathode materials in Comparative Examples 1 and 2 resulted in cathode sheets with relatively high porosity. However, the composite cathode materials in Comparative Examples 1 and 2 showed significantly reduced energy density, charge / discharge efficiency, and capacity retention in their resulting batteries.

[0186] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite cathode material, characterized in that, The cathode includes a positive electrode substrate material and a coating layer disposed on the surface of the positive electrode substrate material. The coating layer contains a halide electrolyte and a modifying group -N(CH3)3R, wherein R is -C. n H 2n+1 n≥9; the modified group -N(CH3)3R combines with the halide ions of the halide through strong electrostatic interaction to form a uniform and dense modified layer on the halide electrolyte.

2. The composite cathode material according to claim 1, characterized in that, It includes at least one of the following features (1) to (6): (1) The n satisfies: 9 ≤ n ≤ 30; (2) The R is a straight chain or contains at least one branch, and the branch is located at position ω-2 to ω-6 in the R; (3) R is a straight chain or contains at least one branch, and the branch is located at the ω-2 to ω-6 position of R, and the branch is taken from at least one of methyl, ethyl, propyl and isopropyl; (4) The chemical formula of the halide electrolyte includes Li z Q q M d Wherein, 2≤z≤3, 0.5≤q≤1, 3≤d≤6, Q includes at least one of In, Y, Zr, Sc and Er, and M is selected from halogens; (5) The mass content of the modifying group -N(CH3)3R in the composite cathode material is 0.01%~0.5%; (6) The mass ratio of the halide electrolyte to the modified group -N(CH3)3R is (10~600):

1.

3. The composite cathode material according to claim 1, characterized in that, It includes at least one of the following features (1) to (3): (1) The cathode substrate material includes LiNi 1-x1-y1 Co x1 Mn y1 O2, LiCoO2, LiNi 0.5 Mn 1.5 O4 and x2Li2MnO3·(1 x2)LiNi a Co b Mn c At least one of O2, wherein 0.02≤x1≤0.15, 0.01≤y1≤0.1, 0.05≤x2≤0.95, 0≤b≤0.5, and a+b+c=1; (2) A base layer is further provided on the surface of the positive electrode substrate material, the coating layer is located on the surface of the base layer, and the base layer contains a lithium compound; (3) A substrate layer is further disposed on the surface of the positive electrode substrate material, and the coating layer is located on the surface of the substrate layer. The substrate layer includes LiNbO3, LiAlO2, Li2SiO3, Li2ZrO3, Li3PO4, Li3BO3 and Li 1.3 Al 0.3 Ti 1.7 At least one of (PO4)3.

4. The composite cathode material according to any one of claims 1 to 3, characterized in that, It includes at least one of the following features (1) to (4): (1) The mass growth rate of the composite cathode material stored in a -30℃ dew point environment for 6 hours is less than 0.17%; (2) The loose packing density of the composite cathode material is 0.54~0.75 g / cc; (3) The battery corresponding to the composite cathode material has an initial charge-discharge efficiency of greater than 82% under 0.1C and 1.9V~3.7V conditions; (4) The capacity retention rate of the battery corresponding to the composite cathode material is greater than 88% after 50 cycles at 0.33C.

5. The method for preparing the composite cathode material according to any one of claims 1 to 4, characterized in that, Includes the following steps: Get [N + (CH3)3R]Z - A coating system formed by halide precursor materials and solvents; The coating system is mixed with the positive electrode matrix material to obtain a hybrid system; The mixture is subjected to heat treatment.

6. The method for preparing the composite cathode material according to claim 5, characterized in that, It includes at least one of the following features (1) to (6): (1) The [N] + (CH3)3R]Z - In this context, R is -C n H 2n+1 n≥9, Z includes BF4 - FSI - TFSI - and PF6 - At least one of them; (2) The halide precursor material includes lithium halide and Q halide, wherein Q includes at least one of In, Y, Zr, Sc and Er; (3) The solvent is selected from polar solvents, including at least one of water, ethylenediamine, acetonitrile, methanol, ethanol, acetone, tetrahydrofuran and isopropanol; (4) The preparation method of the coating system specifically includes: [N + (CH3)3R]Z - The dispersion and the halide precursor material solution are mixed; (5) The [N] + (CH3)3R]Z - The mass percentage of the positive electrode matrix material is 0.01% to 0.5%; (6) The halide electrolyte formed by the halide precursor material accounts for 0.1% to 2% of the mass of the positive electrode matrix material.

7. The method for preparing the composite cathode material according to claim 5, characterized in that, It includes at least one of the following features (1) to (6): (1) The solid mass content in the mixture is ≥50%; (2) The positive electrode substrate material is coated with a base material before being mixed with the coating system to form a base layer on the surface of the positive electrode substrate material; (3) The temperature of the heat treatment is 150~500℃, and the time of the heat treatment is 4~10h; (4) The atmosphere for the heat treatment is selected from at least one of air, oxygen and nitrogen; (5) Post-processing the heat-treated material, the post-processing including cooling, sieving and demagnetization; (6) The dew point of the coating system and the mixture system during the preparation process is ≤-10℃.

8. The method for preparing the composite cathode material according to claim 7, characterized in that, In feature (4), the atmosphere of the heat treatment is air with carbon dioxide removed.

9. The method for preparing the composite cathode material according to claim 7, characterized in that, In feature (5), the product is taken out after being cooled to a temperature ≤95°C.

10. The method for preparing the composite cathode material according to claim 7, characterized in that, In feature (5), the environmental dew point of the post-processing is ≤-20℃.

11. A positive electrode plate, characterized in that, The device comprises a positive current collector and a positive electrode layer located on at least one side of the positive electrode layer, wherein the positive electrode layer comprises a composite positive electrode material prepared by any one of claims 1 to 4 or a composite positive electrode material prepared by any one of claims 5 to 10.

12. The positive electrode sheet according to claim 11, characterized in that, It includes at least one of the following features (1) to (3): (1) The mass content of the composite cathode material in the cathode layer is ≥70%; (2) The positive electrode layer also contains a sulfide solid electrolyte, a conductive agent and a binder; the mass content of the sulfide solid electrolyte in the positive electrode layer is 20%~25%; (3) The porosity of the positive electrode sheet after rolling is ≤25%.

13. A battery, characterized in that, It includes the positive electrode sheet as described in claim 11 or 12.

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