Modified ternary positive electrode material, preparation method and application thereof

Abstract

The application provides a modified ternary positive electrode material and a preparation method and application thereof. The modified ternary positive electrode material comprises: a ternary positive electrode material base; a polyethylene glycol coating layer, which is coated on the surface of the ternary positive electrode material base; and a polypyrrole coating layer, which is coated on the surface of the polyethylene glycol coating layer. In the scheme, the composite coating system of the polypyrrole coating layer and the polyethylene glycol coating layer not only solves the problem of insufficient ion or electron conductivity of a single coating material, but also realizes multiple effects of electronic conduction, ion transmission and interface stability through the synergistic effect of the components, thereby solving the technical problems of the high-nickel ternary positive electrode material in the prior art, such as severe interface side reaction, low ion and electron conductivity and insufficient cycle stability in a full solid-state battery.

Description

Technical Field

[0001] This invention relates to the technical field of all-solid-state batteries, and more specifically, to a modified ternary cathode material, its preparation method, and its application. Background Technology

[0002] Currently, high-nickel ternary cathode materials (such as NCM811, or NCM811 for short) are considered ideal cathode materials for solid-state lithium-ion batteries due to their high specific capacity and low cost. However, in solid-state electrolyte systems, especially when used in combination with sulfide electrolytes, their interface stability becomes a core bottleneck restricting the improvement of battery performance. On the one hand, NCM811 is prone to surface lattice oxygen release and transition metal ion (such as Ni) release under high voltage and high temperature conditions. 4+ These high-valence metal ions dissolve and react with the S² in the reducing sulfide electrolyte. - Violent redox reactions occur, generating high-impedance interfacial byproducts, leading to irreversible loss of active materials and a sharp increase in interfacial charge transport impedance. On the other hand, a space charge layer forms between the positive electrode and the electrolyte, increasing interfacial impedance and hindering ion and electron transport, ultimately resulting in short cycle life and rapid capacity decay.

[0003] In existing technologies, to alleviate the aforementioned interface problems, inorganic coatings such as metal oxides, fluorides, or phosphates are commonly used for surface coating to physically isolate the positive electrode from the electrolyte and suppress side reactions. However, these single inorganic coatings generally suffer from inherent defects such as low intrinsic ionic / electronic conductivity, high mechanical brittleness, and poor interfacial wettability: although metal oxides possess a certain degree of chemical stability, their electronic conductivity is extremely poor, severely limiting the charge transport efficiency within the positive electrode; while fluorides and phosphates, although able to improve interfacial thermal stability, are unable to adapt to the significant volume expansion / contraction of NCM811 during charging and discharging, and are prone to cracking due to stress concentration, thus losing their protective function.

[0004] There is currently no effective solution to the technical problems of severe interfacial side reactions, low ionic and electronic conductivity, and insufficient cycle stability of high-nickel ternary cathode materials in all-solid-state batteries. Summary of the Invention

[0005] The main objective of this invention is to provide a modified ternary cathode material, its preparation method, and its application, in order to solve the technical problems of severe interfacial side reactions, low ionic and electronic conductivity, and insufficient cycle stability of high-nickel ternary cathode materials in all-solid-state batteries.

[0006] To achieve the above objectives, according to one aspect of the present invention, a modified ternary cathode material is provided, comprising: a ternary cathode material substrate; a polyethylene glycol coating layer, wherein the polyethylene glycol coating layer is coated on the surface of the ternary cathode material substrate; and a polypyrrole coating layer, wherein the polypyrrole coating layer is coated on the surface of the polyethylene glycol coating layer.

[0007] Furthermore, the mass ratio of the polyethylene glycol coating layer to the ternary cathode material substrate is 0.7% to 2.5%.

[0008] Furthermore, the mass ratio of the polypyrrole coating layer to the polyethylene glycol coating layer in the ternary cathode material substrate is 1.5% to 5%.

[0009] According to another aspect of the present invention, a method for preparing a modified ternary cathode material is provided. The method includes the following steps: Step S1, mixing a ternary cathode precursor and lithium carbonate to obtain a first mixture, and calcining the first mixture to obtain a ternary cathode material substrate; Step S2, mixing the ternary cathode material substrate with a dispersion of polyethylene glycol to obtain a second mixture, and sequentially separating, washing and drying the second mixture to perform a first coating to obtain a modified ternary cathode material A; Step S3, mixing the modified ternary cathode material A, liquid pyrrole monomer, sodium p-toluenesulfonate, ferric chloride hexahydrate and an organic solvent to obtain a third mixture, and sequentially separating, washing and drying the third mixture to perform a second coating to obtain the modified ternary cathode material.

[0010] Further, in step S1, the calcination treatment includes a first-stage calcination treatment and a second-stage calcination treatment performed sequentially. The first temperature of the first-stage calcination treatment is 450~550℃ and the calcination time is 4~6h. The second temperature of the second-stage calcination treatment is 700~800℃ and the calcination time is 14~16h.

[0011] Furthermore, in the second stage of calcination, the calcination temperature is increased from the first temperature to the second temperature at a rate of 1~3℃ / min.

[0012] Further, in step S2, the ternary cathode material substrate is mixed with the polyethylene glycol dispersion to obtain a second mixture, including: dispersing polyethylene glycol in N-methylpyrrolidone solvent to obtain a polyethylene glycol dispersion; adding the ternary cathode material to the polyethylene glycol dispersion and stirring at a temperature of 45~55℃ for 50~70 min to obtain the second mixture.

[0013] Further, in step S3, the modified ternary cathode material A, liquid pyrrole monomer, sodium p-toluenesulfonate, ferric chloride hexahydrate, and organic solvent are mixed to obtain a third mixture, including: dispersing the liquid pyrrole monomer and sodium p-toluenesulfonate in an organic solvent to obtain a first solution; adding the modified ternary cathode material A to the first solution and stirring to obtain a second solution; dispersing ferric chloride hexahydrate in an organic solvent to obtain a third solution; and adding the third solution dropwise to the second solution under ice bath conditions while continuously stirring to carry out polymerization to obtain the third mixture.

[0014] According to another aspect of the present invention, a positive electrode sheet is provided, wherein the active material of the positive electrode sheet includes the above-described modified ternary positive electrode material, and / or the active material of the positive electrode sheet is prepared by the above-described preparation method.

[0015] According to another aspect of the present invention, an all-solid-state battery is provided, the all-solid-state battery comprising the above-described positive electrode.

[0016] Using the technical solution of the present invention, a polyethylene glycol coating layer is coated on the surface of a ternary cathode material substrate, and a polypyrrole coating layer is coated on the surface of the polyethylene glycol coating layer, that is, a composite coating layer of polypyrrole and polyethylene glycol is constructed on the surface of the ternary cathode material substrate. Polyethylene glycol (PEG) possesses flexible molecular chains and hydrophilic hydroxyl end groups, which can reduce the viscosity of electrode slurry systems and improve dispersion uniformity, thus contributing to improved coating process smoothness and film quality. Furthermore, PEG can enhance interfacial adhesion with copper foil current collectors or electrolytes through hydrogen bonds or polar interactions, reducing electrode peeling due to volume expansion during charge-discharge cycles. While PEG, as an inner coating layer, improves processing performance and interfacial compatibility, its molecular chains, as insulators, lack the ability for free electron migration. Even when coated with active particles in thin film form, it cannot achieve interparticle electron conduction. Polypyrrole (PP), as an outer coating layer, offers excellent electronic conductivity and electrochemical activity due to its unique macromolecular structure and freely migrating electrons, effectively enhancing the conductivity of the cathode material. Simultaneously, the electrochemical activity of PPP can effectively suppress the dissolution of transition metal ions and interfacial redox side reactions, forming a dynamically stable passivation film. In the above scheme, the composite coating system of polypyrrole coating layer and polyethylene glycol coating layer not only solves the problem of insufficient ionic or electronic conductivity of single coating material, but also achieves multiple effects of electronic conduction, ion transport and interface stability through the synergistic effect of each component. It solves the technical problems of severe interfacial side reactions, low ionic and electronic conductivity and insufficient cycle stability of high nickel ternary cathode materials in all-solid-state batteries. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0018] Figure 1 A schematic diagram of the modified ternary cathode material in this invention is shown. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0022] Exemplary embodiments according to this application will now be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. It should be understood that these embodiments are provided so that the disclosure of this application is thorough and complete, and that the concept of these exemplary embodiments is fully conveyed to those skilled in the art. In the drawings, for clarity, the thickness of layers and regions may be exaggerated, and the same reference numerals are used to denote the same devices, and therefore their description will be omitted.

[0023] As analyzed in the background section, existing high-nickel ternary cathode materials in all-solid-state batteries suffer from severe interfacial side reactions, low ionic and electronic conductivity, and insufficient cycle stability. To address these issues, this application provides a modified ternary cathode material, its preparation method, and its application.

[0024] In a typical embodiment of this application, combined with Figure 1 As shown, a modified ternary cathode material is provided, which includes: a ternary cathode material substrate, a polyethylene glycol coating layer and a polypyrrole coating layer, wherein the polyethylene glycol coating layer is coated on the surface of the ternary cathode material substrate and the polypyrrole coating layer is coated on the surface of the polyethylene glycol coating layer.

[0025] In the embodiments of this application, a polyethylene glycol coating layer is coated on the surface of a ternary cathode material substrate, and a polypyrrole coating layer is coated on the surface of the polyethylene glycol coating layer, that is, a composite coating layer of polypyrrole and polyethylene glycol is constructed on the surface of the ternary cathode material substrate. Polyethylene glycol (PEG) possesses flexible molecular chains and hydrophilic hydroxyl end groups, which can reduce the viscosity of electrode slurry systems and improve dispersion uniformity, thus contributing to improved coating process smoothness and film quality. Furthermore, PEG can enhance interfacial adhesion with copper foil current collectors or electrolytes through hydrogen bonds or polar interactions, reducing electrode peeling due to volume expansion during charge-discharge cycles. While PEG, as an inner coating layer, improves processing performance and interfacial compatibility, its molecular chains, as insulators, lack the ability for free electron migration. Even when coated with active particles in thin film form, it cannot achieve interparticle electron conduction. Polypyrrole (PP), as an outer coating layer, offers excellent electronic conductivity and electrochemical activity due to its unique macromolecular structure and freely migrating electrons, effectively enhancing the conductivity of the cathode material. Simultaneously, the electrochemical activity of PPP can effectively suppress the dissolution of transition metal ions and interfacial redox side reactions, forming a dynamically stable passivation film. In the above scheme, the composite coating system of polypyrrole coating layer and polyethylene glycol coating layer not only solves the problem of insufficient ionic or electronic conductivity of single coating material, but also achieves multiple effects of electronic conduction, ion transport and interface stability through the synergistic effect of each component. It solves the technical problems of severe interfacial side reactions, low ionic and electronic conductivity and insufficient cycle stability of high nickel ternary cathode materials in all-solid-state batteries.

[0026] In one embodiment of this application, the mass ratio of the polyethylene glycol coating layer to the ternary cathode material substrate is 0.7% to 2.5%.

[0027] In the embodiments of this application, the mass ratio of the polyethylene glycol (PEG) coating layer to the ternary cathode material substrate is controlled within the aforementioned range to ensure that the PEG coating layer, while providing interfacial protection, does not block the lithium-ion transport channels due to excessive coating. In other words, controlling the mass ratio of the PEG coating layer to the ternary cathode material substrate within the aforementioned range not only effectively suppresses interfacial side reactions, significantly reduces transition metal dissolution, and greatly improves cycle performance, but also achieves optimal synergy between ion conductivity, mechanical buffering, and process adaptability.

[0028] In one embodiment of this application, the mass ratio of the polypyrrole coating layer to the polyethylene glycol coating layer of the ternary cathode material substrate is 1.5% to 5%.

[0029] In the embodiments of this application, the mass ratio of the polypyrrole coating layer to the polyethylene glycol coating layer of the ternary cathode material substrate is controlled within the above-mentioned range. The polypyrrole forms a continuous conductive network between the material particles, which significantly reduces the internal resistance of the electrode and improves the electron transport efficiency during the lithium-ion insertion / extraction process.

[0030] In another typical embodiment of this application, a method for preparing a modified ternary cathode material is provided, the method comprising the following steps:

[0031] Step S1: Mix the ternary cathode precursor and lithium carbonate to obtain a first mixture, and calcine the first mixture to obtain a ternary cathode material substrate.

[0032] Step S2: The ternary cathode material substrate is mixed with a dispersion of polyethylene glycol to obtain a second mixture. The second mixture is then separated, washed, and dried sequentially for the first coating to obtain modified ternary cathode material A.

[0033] Step S3: The modified ternary cathode material A, liquid pyrrole monomer, sodium p-toluenesulfonate, ferric chloride hexahydrate and organic solvent are mixed to obtain a third mixture. The third mixture is then separated, washed and dried sequentially for a second coating to obtain the modified ternary cathode material.

[0034] In the embodiments of this application, in step S1, the solid-state calcination of the ternary cathode precursor and lithium carbonate yields a ternary cathode material substrate with a complete structure, high crystallinity, and uniform composition, ensuring that the ternary cathode material substrate possesses excellent crystal structure and lithium-ion diffusion channels; in step S2, a polyethylene glycol dispersion is used to coat the ternary cathode material substrate with a first layer to construct a dense, flexible, and highly adhesive interface buffer layer; in step S3, liquid pyrrole monomer is used to perform in-situ chemical oxidation polymerization on the surface of the polyethylene glycol coating layer under the conditions of ferric chloride hexahydrate as an oxidant and sodium p-toluenesulfonate as a dopant to generate polypyrrole. The conductive network consists of three main components: First, the polyethylene glycol (PEG) coating acts as an intermediate medium, enabling pyrrole monomers to be uniformly adsorbed on the material surface, thus avoiding non-uniform deposition caused by the free diffusion of monomers in the electrolyte. Second, the hydrophilic environment of the PEG coating facilitates the synergistic effect between ferric ions and pyrrole monomers, promoting the deposition of pyrrole monomers in a continuous thin film form rather than particulate agglomeration, thereby forming a dense, continuous, and low-impedance electronic conduction path. Third, sodium p-toluenesulfonate, as a bulk anionic dopant, can improve the conductivity stability and environmental tolerance of polypyrrole, prevent excessive oxidative degradation under high voltage, and enhance the conductivity persistence during electrochemical cycling.

[0035] Specifically, the preparation method of the ternary cathode precursor in step S1 includes the following steps:

[0036] Step S11: Add nickel sulfate, cobalt sulfate, manganese sulfate, sodium hydroxide and ammonium hydroxide into a container, heat and stir to obtain a fourth mixture.

[0037] Step S12: The fourth mixture is filtered, washed and dried sequentially to obtain a ternary cathode precursor.

[0038] In one embodiment of this application, step S1 includes a first-stage calcination treatment and a second-stage calcination treatment performed sequentially. The first temperature of the first-stage calcination treatment is 450~550℃ and the calcination time is 4~6h. The second temperature of the second-stage calcination treatment is 700~800℃ and the calcination time is 14~16h.

[0039] In the embodiments of this application, the solid-state calcination of the ternary cathode precursor and lithium carbonate adopts a two-stage stepped heating process. The first-stage calcination temperature is controlled within the range of 450~550℃ and the calcination time is controlled within the range of 4~6h, so that the dehydration and partial lithiation reactions occur slowly and uniformly, forming a preliminary spinel-type or rock salt-type mesophase, laying a homogeneous foundation for the construction of a complete layered structure in the subsequent high-temperature stage. The second-stage calcination temperature is controlled within the range of 700~800℃ and the calcination time is controlled within the range of 14~16h, giving lithium ions sufficient time to complete lattice migration while avoiding side reactions, thereby achieving a layered structure with high crystallinity, low cation mixing, and high order.

[0040] Furthermore, in the second stage of calcination, the calcination temperature is increased from the first temperature to the second temperature at a rate of 1~3℃ / min.

[0041] In the embodiments of this application, during the high-temperature calcination stage, the temperature rise rate is controlled within the range of 1~3℃ / min, so that the heat can penetrate evenly into the interior of the particles, allowing the solid-phase reaction between lithium ions and transition metal oxides to proceed at a controllable rate. The outer layer gradually forms a dense layered structure, while the core simultaneously completes the removal of residual hydroxyl groups and lattice recombination, avoiding the incoordination phenomenon of fast outside and slow inside, thereby avoiding local enrichment of lithium salt, uneven composition, abnormal grain growth or even particle bursting, and at the same time avoiding particle pulverization, abnormal increase in porosity or structural collapse.

[0042] In one embodiment of this application, in step S2, the ternary cathode material substrate is mixed with a dispersion of polyethylene glycol to obtain a second mixture, including: dispersing polyethylene glycol in N-methylpyrrolidone solvent to obtain a polyethylene glycol dispersion; adding the ternary cathode material to the polyethylene glycol dispersion and stirring at a temperature of 45~55°C for 50~70 min to obtain the second mixture.

[0043] In the embodiments of this application, N-methylpyrrolidone solvent, as a highly polar aprotic solvent, allows the polyethylene glycol molecular chains to fully extend and uniformly disperse in the solution, preventing them from forming aggregates in water due to hydrogen bonding self-association. This allows the polyethylene glycol to spread uniformly on the surface of the ternary cathode material particles in the form of monomolecules or oligomers, ultimately forming a dense, continuous, and defect-free coating layer. When the stirring temperature is in the range of 45~55℃ and the stirring time is in the range of 50~70min, the viscosity of the N-methylpyrrolidone solvent is moderate, the thermal motion of the polyethylene glycol molecular chains is enhanced, and the diffusion rate is significantly improved, enabling it to penetrate more efficiently into the micropores and surface defect areas between the primary particles of the ternary cathode material, and the resulting polyethylene glycol coating layer has a uniform thickness.

[0044] In one embodiment of this application, step S3 involves mixing modified ternary cathode material A, liquid pyrrole monomer, sodium p-toluenesulfonate, ferric chloride hexahydrate, and an organic solvent to obtain a third mixture. This includes: dispersing the liquid pyrrole monomer and sodium p-toluenesulfonate in an organic solvent to obtain a first solution; adding modified ternary cathode material A to the first solution and stirring to obtain a second solution; dispersing ferric chloride hexahydrate in an organic solvent to obtain a third solution; and adding the third solution dropwise to the second solution under ice bath conditions while continuously stirring to polymerize, thereby obtaining the third mixture.

[0045] In the embodiments of this application, pyrrole monomers and sodium p-toluenesulfonate are pre-mixed to form a first solution, achieving molecular-level uniform dispersion of the dopant and pyrrole monomers in the solvent. Sodium p-toluenesulfonate, as a bulk anionic dopant, has sulfonate groups in its structure that can stabilize the positive charge on the polypyrrole chains, improving conductivity and environmental stability. Modified ternary cathode material A is added to the first solution and stirred, so that the material particles are uniformly wetted and adsorbed into the pyrrole-dopant composite system before the polymerization reaction starts. The polyethylene glycol coating layer itself has hydrophilicity and high surface energy, which can serve as a molecular adsorption platform, allowing pyrrole molecules to preferentially accumulate on the material surface rather than freely polymerizing in the solvent bulk, thereby achieving highly selective and highly adhesive in-situ coating and greatly reducing the generation of ineffective polymer byproducts. Ferric chloride hexahydrate, as a strong oxidant, is added dropwise to the second solution under ice bath conditions, causing the pyrrole monomers to undergo slow and orderly oxidative polymerization layer by layer on the material surface, effectively suppressing side reactions and chain termination, and finally forming a uniform, dense, non-porous, and continuously conductive polypyrrole nanofilm.

[0046] In another typical embodiment of this application, a positive electrode sheet is provided, wherein the active material of the positive electrode sheet includes the modified ternary positive electrode material in the above embodiments, and / or the active material of the positive electrode sheet is prepared by the preparation method in the above embodiments.

[0047] In another typical embodiment of this application, an all-solid-state battery is provided, which includes the positive electrode sheet in the above embodiments.

[0048] The beneficial effects of this application will be explained below with reference to specific embodiments and comparative examples.

[0049] Example 1

[0050] A method for preparing a modified ternary cathode material, specifically including the following steps:

[0051] Step 1: Add 2 mol / L of metal salt (NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) and 2 mol / L of NaOH to separate containers. Maintain the reaction temperature at 55℃ and the pH value at 11, and stir continuously for 12 hours to obtain spherical ternary cathode precursor powder ([NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) 0.8 Co 0.1 Mn 0.1 The ternary cathode precursor powder was filtered, washed, and dried under vacuum at 80°C for 24 hours to obtain the dehydrated ternary cathode precursor.

[0052] Step 2: The dehydrated ternary cathode precursor and lithium carbonate are mixed in a mortar (the molar ratio of Li to (Mn+Co+Ni) is 1.05:1). The mixed powder is first calcined at 500℃ for 5 hours, and then heated to 750℃ in air at a heating rate of 2℃ / min, and calcined at 750℃ for 15 hours to obtain the ternary cathode material substrate (NCM811 material).

[0053] Step 3: Disperse 1.5g of polyethylene glycol in a single N-methylpyrrolidone solvent, then add 98.5g of ternary cathode material substrate powder to the polyethylene glycol dispersion and stir at 50℃ for 1h. After stirring, filter and wash it several times, then place it in a vacuum oven for drying at 120℃ for 12h. The resulting product is denoted as modified ternary cathode material A.

[0054] Step 4: Disperse 3g of liquid pyrrole monomer and sodium p-toluenesulfonate as a dopant in ethanol and stir continuously for 2 hours. Then, add the modified ternary cathode material A powder to the above solution and continue stirring for 2 hours. Dissolve FeCl3·6H2O as an oxidant in another beaker, wherein the molar ratio of dopant, liquid pyrrole monomer and oxidant is 1:3:9. Then, under ice bath conditions, add the FeCl3·6H2O solution dropwise to the previous solution and stir continuously for 6 hours to complete the polymerization. Then filter the solution, wash it 4 times with ethanol, and dry it in a vacuum environment at 60°C for 24 hours to obtain the modified ternary cathode material.

[0055] Example 2

[0056] A method for preparing a modified ternary cathode material, specifically including the following steps:

[0057] Step 1: Add 2 mol / L of metal salt (NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) and 2 mol / L of NaOH to separate containers. Maintain the reaction temperature at 55℃ and the pH value at 11, and stir continuously for 12 hours to obtain spherical ternary cathode precursor powder ([NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) 0.8 Co 0.1 Mn 0.1 The ternary cathode precursor powder was filtered, washed, and dried under vacuum at 80°C for 24 hours to obtain the dehydrated ternary cathode precursor.

[0058] Step 2: The dehydrated ternary cathode precursor and lithium carbonate are mixed in a mortar (the molar ratio of Li to (Mn+Co+Ni) is 1.05:1). The mixed powder is first calcined at 500℃ for 5 hours, and then heated to 750℃ in air at a heating rate of 2℃ / min, and calcined at 750℃ for 15 hours to obtain the ternary cathode material substrate (NCM811 material).

[0059] Step 3: Disperse 0.75g of polyethylene glycol in a single N-methylpyrrolidone solvent, then add 99.25g of ternary cathode material substrate powder to the polyethylene glycol dispersion and stir at 50℃ for 1h. After stirring, filter and wash it several times, then place it in a vacuum oven for drying at 120℃ for 12h. The resulting product is denoted as modified ternary cathode material A.

[0060] Step 4: Disperse 3g of liquid pyrrole monomer and sodium p-toluenesulfonate as a dopant in ethanol and stir continuously for 2 hours. Then, add the modified ternary cathode material A powder to the above solution and continue stirring for 2 hours. Dissolve FeCl3·6H2O as an oxidant in another beaker, wherein the molar ratio of dopant, liquid pyrrole monomer and oxidant is 1:3:9. Then, under ice bath conditions, add the FeCl3·6H2O solution dropwise to the previous solution and stir continuously for 6 hours to complete the polymerization. Then filter the solution, wash it 4 times with ethanol, and dry it in a vacuum environment at 60°C for 24 hours to obtain the modified ternary cathode material.

[0061] Example 3

[0062] A method for preparing a modified ternary cathode material, specifically including the following steps:

[0063] Step 1: Add 2 mol / L of metal salt (NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) and 2 mol / L of NaOH to separate containers. Maintain the reaction temperature at 55℃ and the pH value at 11, and stir continuously for 12 hours to obtain spherical ternary cathode precursor powder ([NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) 0.8 Co 0.1 Mn 0.1 The ternary cathode precursor powder was filtered, washed, and dried under vacuum at 80°C for 24 hours to obtain the dehydrated ternary cathode precursor.

[0064] Step 2: The dehydrated ternary cathode precursor and lithium carbonate are mixed in a mortar (the molar ratio of Li to (Mn+Co+Ni) is 1.05:1). The mixed powder is first calcined at 500℃ for 5 hours, and then heated to 750℃ in air at a heating rate of 2℃ / min, and calcined at 750℃ for 15 hours to obtain the ternary cathode material substrate (NCM811 material).

[0065] Step 3: Disperse 2.25g of polyethylene glycol in a single N-methylpyrrolidone solvent, then add 97.75g of ternary cathode material substrate powder to the polyethylene glycol dispersion and stir at 50℃ for 1h. After stirring, filter and wash it several times, then place it in a vacuum oven for drying at 120℃ for 12h. The resulting product is denoted as modified ternary cathode material A.

[0066] Step 4: Disperse 3g of liquid pyrrole monomer and sodium p-toluenesulfonate as a dopant in ethanol and stir continuously for 2 hours. Then, add the modified ternary cathode material A powder to the above solution and continue stirring for 2 hours. Dissolve FeCl3·6H2O as an oxidant in another beaker, wherein the molar ratio of dopant, liquid pyrrole monomer and oxidant is 1:3:9. Then, under ice bath conditions, add the FeCl3·6H2O solution dropwise to the previous solution and stir continuously for 6 hours to complete the polymerization. Then filter the solution, wash it 4 times with ethanol, and dry it in a vacuum environment at 60°C for 24 hours to obtain the modified ternary cathode material.

[0067] Example 4

[0068] A method for preparing a modified ternary cathode material, specifically including the following steps:

[0069] Step 1: Add 2 mol / L of metal salt (NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) and 2 mol / L of NaOH to separate containers. Maintain the reaction temperature at 55℃ and the pH value at 11, and stir continuously for 12 hours to obtain spherical ternary cathode precursor powder ([NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) 0.8 Co 0.1 Mn 0.1 The ternary cathode precursor powder was filtered, washed, and dried under vacuum at 80°C for 24 hours to obtain the dehydrated ternary cathode precursor.

[0070] Step 2: The dehydrated ternary cathode precursor and lithium carbonate are mixed in a mortar (the molar ratio of Li to (Mn+Co+Ni) is 1.05:1). The mixed powder is first calcined at 500℃ for 5 hours, and then heated to 750℃ in air at a heating rate of 2℃ / min, and calcined at 750℃ for 15 hours to obtain the ternary cathode material substrate (NCM811 material).

[0071] Step 3: Disperse 1.5g of polyethylene glycol in a single N-methylpyrrolidone solvent, then add 98.5g of ternary cathode material substrate powder to the polyethylene glycol dispersion and stir at 50℃ for 1h. After stirring, filter and wash it several times, then place it in a vacuum oven for drying at 120℃ for 12h. The resulting product is denoted as modified ternary cathode material A.

[0072] Step 4: Disperse 1.5g of liquid pyrrole monomer and sodium p-toluenesulfonate as a dopant in ethanol and stir continuously for 2 hours. Then, add the modified ternary cathode material A powder to the above solution and continue stirring for 2 hours. Dissolve FeCl3·6H2O as an oxidant in another beaker, wherein the molar ratio of dopant, liquid pyrrole monomer and oxidant is 1:3:9. Then, under ice bath conditions, add the FeCl3·6H2O solution dropwise to the previous solution and stir continuously for 6 hours to complete the polymerization. Then filter the solution, wash it 4 times with ethanol, and dry it in a vacuum environment at 60°C for 24 hours to obtain the modified ternary cathode material.

[0073] Example 5

[0074] A method for preparing a modified ternary cathode material, specifically including the following steps:

[0075] Step 1: Add 2 mol / L of metal salt (NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) and 2 mol / L of NaOH to separate containers. Maintain the reaction temperature at 55℃ and the pH value at 11, and stir continuously for 12 hours to obtain spherical ternary cathode precursor powder ([NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) 0.8 Co 0.1 Mn 0.1 The ternary cathode precursor powder was filtered, washed, and dried under vacuum at 80°C for 24 hours to obtain the dehydrated ternary cathode precursor.

[0076] Step 2: The dehydrated ternary cathode precursor and lithium carbonate are mixed in a mortar (the molar ratio of Li to (Mn+Co+Ni) is 1.05:1). The mixed powder is first calcined at 500℃ for 5 hours, and then heated to 750℃ in air at a heating rate of 2℃ / min, and calcined at 750℃ for 15 hours to obtain the ternary cathode material substrate (NCM811 material).

[0077] Step 3: Disperse 1.5g of polyethylene glycol in a single N-methylpyrrolidone solvent, then add 98.5g of ternary cathode material substrate powder to the polyethylene glycol dispersion and stir at 50℃ for 1h. After stirring, filter and wash it several times, then place it in a vacuum oven for drying at 120℃ for 12h. The resulting product is denoted as modified ternary cathode material A.

[0078] Step 4: Disperse 4.5g of liquid pyrrole monomer and sodium p-toluenesulfonate as a dopant in ethanol and stir continuously for 2 hours. Then, add the modified ternary cathode material A powder to the above solution and continue stirring for 2 hours. Dissolve FeCl3·6H2O as an oxidant in another beaker, wherein the molar ratio of dopant, liquid pyrrole monomer and oxidant is 1:3:9. Then, under ice bath conditions, add the FeCl3·6H2O solution dropwise to the previous solution and stir continuously for 6 hours to complete the polymerization. Then filter the solution, wash it 4 times with ethanol, and dry it in a vacuum environment at 60°C for 24 hours to obtain the modified ternary cathode material.

[0079] Comparative Example 1

[0080] A method for preparing a ternary cathode material specifically includes the following steps:

[0081] Step 1: Add 2 mol / L of metal salt (NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) and 2 mol / L of NaOH to separate containers. Maintain the reaction temperature at 55℃ and the pH value at 11, and stir continuously for 12 hours to obtain spherical ternary cathode precursor powder ([NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) 0.8 Co 0.1 Mn 0.1 The ternary cathode precursor powder was filtered, washed, and dried under vacuum at 80°C for 24 hours to obtain the dehydrated ternary cathode precursor.

[0082] Step 2: The dehydrated ternary cathode precursor and lithium carbonate are mixed in a mortar (the molar ratio of Li to (Mn+Co+Ni) is 1.05:1). The mixed powder is first calcined at 500℃ for 5 hours, and then heated to 750℃ in air at a heating rate of 2℃ / min, and calcined at 750℃ for 15 hours to obtain the ternary cathode material (NCM811 material).

[0083] Comparative Example 2

[0084] A method for preparing a modified ternary cathode material, specifically including the following steps:

[0085] Step 1: Add 2 mol / L of metal salt (NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) and 2 mol / L of NaOH to separate containers. Maintain the reaction temperature at 55℃ and the pH value at 11, and stir continuously for 12 hours to obtain spherical ternary cathode precursor powder ([NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) 0.8 Co 0.1 Mn 0.1 The ternary cathode precursor powder was filtered, washed, and dried under vacuum at 80°C for 24 hours to obtain the dehydrated ternary cathode precursor.

[0086] Step 2: The dehydrated ternary cathode precursor and lithium carbonate are mixed in a mortar (the molar ratio of Li to (Mn+Co+Ni) is 1.05:1). The mixed powder is first calcined at 500℃ for 5 hours, and then heated to 750℃ in air at a heating rate of 2℃ / min, and calcined at 750℃ for 15 hours to obtain the ternary cathode material substrate (NCM811 material).

[0087] Step 3: Disperse 1.5g of polyethylene glycol in a single N-methylpyrrolidone solvent, then add 97.5g of ternary cathode material substrate powder to the polyethylene glycol dispersion and stir at 50℃ for 1h. After stirring, filter and wash it several times, then place it in a vacuum oven for drying at 120℃ for 12h. The resulting product is denoted as modified ternary cathode material.

[0088] Comparative Example 3

[0089] A method for preparing a modified ternary cathode material, specifically including the following steps:

[0090] Step 1: Add 2 mol / L of metal salt (NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) and 2 mol / L of NaOH to separate containers. Maintain the reaction temperature at 55℃ and the pH value at 11, and stir continuously for 12 hours to obtain spherical ternary cathode precursor powder ([NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O in a molar ratio of 8:1:1) 0.8 Co 0.1 Mn 0.1 The ternary cathode precursor powder was filtered, washed, and dried under vacuum at 80°C for 24 hours to obtain the dehydrated ternary cathode precursor.

[0091] Step 2: The dehydrated ternary cathode precursor and lithium carbonate are mixed in a mortar (the molar ratio of Li to (Mn+Co+Ni) is 1.05:1). The mixed powder is first calcined at 500℃ for 5 hours, and then heated to 750℃ in air at a heating rate of 2℃ / min, and calcined at 750℃ for 15 hours to obtain the ternary cathode material substrate (NCM811 material).

[0092] Step 3: Disperse 3g of liquid pyrrole monomer and sodium p-toluenesulfonate as a dopant in ethanol and stir continuously for 2 hours. Then, add 97g of ternary cathode material substrate powder to the above solution and continue stirring for 2 hours. Dissolve FeCl3·6H2O as an oxidant in another beaker, wherein the molar ratio of dopant, liquid pyrrole monomer and oxidant is 1:3:9. Then, under ice bath conditions, add FeCl3·6H2O solution dropwise to the previous solution and stir continuously for 6 hours to complete the polymerization. Then filter the solution, wash it 4 times with ethanol, and dry it in a vacuum environment at 60°C for 24 hours to obtain the modified ternary cathode material.

[0093] The positive electrode materials obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were respectively mixed with sulfide solid electrolyte, conductive agent, binder and organic solvent to obtain a uniform slurry. The slurry was coated on the current collector and dried to obtain a composite positive electrode sheet. The sulfide solid electrolyte was placed in a mold battery and pressed at 125 MPa. The composite positive electrode sheet was then placed on one side of the electrolyte and pressed at 320 MPa. Lithium-indium alloy was then placed on the other side of the electrolyte and placed in a stainless steel fixture. The battery was pressed at 125 MPa and the bolts were tightened to obtain an all-solid-state mold battery.

[0094] Charge and discharge tests were conducted at different rates of 0.1C, 0.3C, 0.5C, 1C, 2C, and 0.1C within a voltage range of 1.9V to 3.7V at 30℃. Long-cycle charge and discharge tests were also conducted at 1C. The specific test results are shown in Table 1.

[0095] Table 1

[0096]

[0097] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0098] A polyethylene glycol (PEG) coating layer is applied to the surface of a ternary cathode material substrate, and a polypyrrole (PPG) coating layer is applied to the surface of the PEG coating layer, thus constructing a composite coating layer of PPG and PEG on the surface of the ternary cathode material substrate. This composite coating system not only solves the problem of insufficient ionic or electronic conductivity of single coating materials, but also achieves multiple effects such as electronic conduction, ion transport, and interface stability through the synergistic effect of each component. This addresses the technical problems of severe interfacial side reactions, low ionic and electronic conductivity, and insufficient cycle stability of high-nickel ternary cathode materials in all-solid-state batteries in existing technologies.

[0099] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0100] In addition to the above, it should be noted that the terms "one embodiment," "another embodiment," and "embodiment" used in this specification refer to specific features, structures, or characteristics described in connection with that embodiment, which are included in at least one embodiment described in the general description of this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in connection with any embodiment, the intention is to suggest that implementing such a feature, structure, or characteristic in conjunction with other embodiments also falls within the scope of this invention.

[0101] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A modified ternary cathode material, characterized in that, The modified ternary cathode material includes: Ternary cathode material substrate; A polyethylene glycol coating layer, wherein the polyethylene glycol coating layer is coated on the surface of the ternary cathode material substrate; A polypyrrole coating layer, wherein the polypyrrole coating layer covers the surface of the polyethylene glycol coating layer.

2. The modified ternary cathode material according to claim 1, characterized in that, The mass ratio of the polyethylene glycol coating layer to the ternary cathode material substrate is 0.7% to 2.5%.

3. The modified ternary cathode material according to claim 1, characterized in that, The mass ratio of the polypyrrole coating layer to the polyethylene glycol coating layer covering the ternary cathode material substrate is 1.5% to 5%.

4. A method for preparing a modified ternary cathode material according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: Step S1: Mix the ternary cathode precursor and lithium carbonate to obtain a first mixture, and calcine the first mixture to obtain a ternary cathode material substrate. Step S2: The ternary cathode material substrate is mixed with a dispersion of polyethylene glycol to obtain a second mixture. The second mixture is then separated, washed, and dried sequentially for a first coating to obtain modified ternary cathode material A. Step S3: The modified ternary cathode material A, liquid pyrrole monomer, sodium p-toluenesulfonate, ferric chloride hexahydrate and organic solvent are mixed to obtain a third mixture. The third mixture is then separated, washed and dried sequentially for a second coating to obtain the modified ternary cathode material.

5. The preparation method according to claim 4, characterized in that, In step S1, the calcination treatment includes a first-stage calcination treatment and a second-stage calcination treatment performed sequentially. The first temperature of the first-stage calcination treatment is 450~550℃ and the calcination time is 4~6h. The second temperature of the second-stage calcination treatment is 700~800℃ and the calcination time is 14~16h.

6. The preparation method according to claim 5, characterized in that, In the second stage of calcination, the calcination temperature is increased from the first temperature to the second temperature at a rate of 1~3℃ / min.

7. The preparation method according to claim 4, characterized in that, In step S2, the ternary cathode material substrate is mixed with a dispersion of polyethylene glycol to obtain a second mixture, comprising: The polyethylene glycol was dispersed in N-methylpyrrolidone solvent to obtain a dispersion of the polyethylene glycol; The ternary cathode material is added to the polyethylene glycol dispersion and stirred at a temperature of 45-55°C for 50-70 minutes to obtain the second mixture.

8. The preparation method according to claim 4, characterized in that, In step S3, the modified ternary cathode material A, liquid pyrrole monomer, sodium p-toluenesulfonate, ferric chloride hexahydrate, and an organic solvent are mixed to obtain a third mixture, comprising: The liquid pyrrole monomer and the sodium p-toluenesulfonate are dispersed in the organic solvent to obtain a first solution; The modified ternary cathode material A is added to the first solution and stirred to obtain a second solution; The ferric chloride hexahydrate is dispersed in the organic solvent to obtain a third solution; Under ice bath conditions, the third solution is added dropwise to the second solution while continuously stirring to carry out polymerization, thereby obtaining the third mixture.

9. A positive electrode sheet, characterized in that, The active material of the positive electrode sheet includes the modified ternary positive electrode material according to any one of claims 1-3, and / or the active material of the positive electrode sheet is prepared by the preparation method according to any one of claims 4-8.

10. An all-solid-state battery, characterized in that, The all-solid-state battery includes the positive electrode sheet as described in claim 9.

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