A bifunctional interface lithium-rich manganese-based positive electrode material and a preparation method and application thereof

Abstract

This invention proposes a dual-functional interface lithium-rich manganese-based cathode material, its preparation method, and its application, belonging to the technical field of lithium-ion battery cathode materials. The dual-functional interface lithium-rich manganese-based cathode material of this invention comprises lithium-rich manganese-based morphological oxide core particles, an inner negative thermal expansion inorganic layer coating the surface of the lithium-rich manganese-based morphological oxide core particles, and an outer fast lithium-ion conductive layer coating the outer side of the inner negative thermal expansion inorganic layer. This invention achieves both mechanical and chemical / ionic control at the particle scale through the synergistic effect of the inner and outer layers. Compared with solutions using only inert coatings, single lithium-ion conductive coatings, or single negative thermal expansion coatings, this invention can more comprehensively address the thermo-chemical-mechanical coupling failure problem at the cathode / solid electrolyte interface in all-solid-state batteries, achieving lower interface impedance, smaller voltage decay, and higher cycle stability. Furthermore, the preparation process is simple and suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material technology, and particularly relates to a dual-functional interface lithium-rich manganese-based cathode material, its preparation method and application. Background Technology

[0002] Lithium-rich manganese-based cathode materials (Li-rich layered oxide, abbreviated as LLO), usually represented as xLi2MnO3(1-x)LiTMO2 (where TM represents Ni, Co, Mn, etc.), have high specific capacity (theoretical capacity can exceed 250 mAh·g). -1 With its advantages such as high operating voltage, abundant Mn element, and low cost, it is considered an important candidate cathode system for constructing high energy density lithium-ion batteries.

[0003] However, in practical applications, lithium-rich manganese-based cathodes suffer from a series of problems: during high-voltage charge and discharge, lattice oxygen participates in redox reactions, triggering irreversible structural reconstruction and metal cation migration, leading to the formation of local rock salt / spinel phases, which in turn results in voltage plateau decay, a decrease in average discharge voltage, and poorer cycle stability. Simultaneously, lithium-rich manganese-based cathodes exhibit significant volume changes during lithium insertion / extraction, making them prone to stress concentration and microcracks within the particles.

[0004] In all-solid-state lithium batteries, the high elastic modulus, limited plasticity, and relative brittleness of the solid electrolyte exacerbate the thermo-mechanical mismatch between the volume changes and structural remodeling of the lithium-rich manganese-based cathode and the solid electrolyte. On one hand, the expansion and contraction of cathode particles exert significant tensile and shear stresses on the solid electrolyte, leading to interfacial microcracks, pores, and debonding. On the other hand, when the lithium-rich cathode comes into direct contact with sulfide, oxide, halide, or polymer solid electrolytes, interfacial side reactions often occur, forming an intermediate phase with high resistivity. These factors combined result in a gradual decrease in the effective contact area at the cathode / solid electrolyte interface in all-solid-state lithium batteries, a rapid increase in interfacial impedance, and particularly significant voltage and capacity decay under high-voltage, long-cycle operation.

[0005] In existing technologies, to improve the stability of the cathode-electrolyte interface, researchers have attempted to introduce various coating materials onto the surface of high-nickel or lithium-rich cathodes, such as Al2O3, Li3PO4, LiNbO3, NASICON-type materials, and halide solid electrolytes. These coatings can suppress interfacial side reactions, alleviate transition metal dissolution, and reduce interfacial impedance to some extent in liquid electrolyte systems, and can also partially improve interfacial chemical stability in all-solid-state systems. However, current coating designs mainly focus on "chemical / electrochemical stability" and "lithium-ion conduction," with insufficient attention paid to interfacial stress and mechanical failure caused by changes in cathode particle volume.

[0006] On the other hand, inorganic oxides exhibiting negative thermal expansion (NTE) behavior, such as some A2M3O 12 NTE materials, exhibiting volume contraction with increasing temperature within a specific temperature range, hold promise for offsetting cathode volume expansion and regulating stress distribution. Introducing NTE materials into the cathode surface can help establish a favorable compressive stress field at the particle interface, mitigating particle cracking and interface damage. However, NTE materials themselves often have low lithium-ion conductivity and limited chemical compatibility with solid electrolytes. Using only a single NTE coating can easily introduce additional ion transport resistance or even new interfacial instabilities.

[0007] In summary, there is a lack of a multifunctional interface structure in the current technology that can simultaneously achieve "mechanical negative thermal expansion regulation" and "interface chemical / ion compatibility regulation" on the surface of a single positive electrode particle. In particular, in all-solid-state lithium batteries, how to synergistically solve problems such as positive electrode volume change, interface stress concentration and interface side reactions at the particle scale remains to be solved. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a dual-functional interface lithium-rich manganese-based cathode material, its preparation method, and its application. By constructing a negative thermal expansion inorganic inner layer and a lithium-ion conductive outer layer sequentially distributed from the inside out on the surface of lithium-rich manganese-based basal oxide particles, the functional division of mechanical stress regulation and interface chemical / ionic regulation is achieved. This significantly alleviates the stress concentration, interface cracking, and contact failure problems at the lithium-rich cathode / solid electrolyte interface in all-solid-state lithium batteries, and improves the cycle stability and voltage retention capability of all-solid-state lithium batteries.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] This invention provides a dual-functional interface lithium-rich manganese-based cathode material, comprising: lithium-rich manganese-based morphological oxide core particles, an inner negative thermal expansion inorganic layer coated on the surface of the lithium-rich manganese-based morphological oxide core particles, and an outer fast lithium-ion conductive layer coated on the outside of the inner negative thermal expansion inorganic layer.

[0011] The general chemical formula of the lithium-rich manganese-based basal oxide core particles is Li. 1+a Mn x Co y Ni z O2, where 0 < a ≤ 0.4, 0.3 ≤ x ≤ 0.6, 0 < y ≤ 0.25, 0 < z ≤ 0.25;

[0012] The inner negative thermal expansion inorganic layer is an oxide ceramic;

[0013] The outer fast lithium-ion conductive layer is selected from at least one of lithium-containing inorganic ion conductors.

[0014] Furthermore, in the positive electrode material, the inner negative thermal expansion inorganic layer has a mass fraction of 0.1–10 wt%, the outer fast lithium-ion conductive layer has a mass fraction of 0.1–10 wt%, and the remainder is the lithium-rich manganese-based crystalline oxide core particles; the average thickness of the inner negative thermal expansion inorganic layer is 2–100 nm (preferably 5–50 nm), and the average thickness of the outer fast lithium-ion conductive layer is 2–100 nm (preferably 5–30 nm). By controlling the mass fractions of the inner and outer layers, a balance between stress regulation and ion conduction is achieved.

[0015] Furthermore, the chemical formula of the lithium-rich manganese-based layered oxide core particles is Li. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O2.

[0016] Furthermore, the inner negative thermal expansion inorganic layer is selected from A2M3O 12 At least one of the following oxides, wherein element A is one or more of Sc, Y, or rare earth elements, and element M is W or Mo. The inner layer of negative thermal expansion inorganic material is an inorganic oxide with isotropic or near-isotropic negative thermal expansion behavior, and its average linear expansion coefficient in the range of 20–200℃ is -20 × 10⁻⁶. -6 ~0×10 -6 K -1 It is used to provide circumferential compressive constraint on the volume expansion of the lithium-rich manganese-based base oxide.

[0017] Furthermore, the outer fast lithium-ion conductive layer is selected from lithium-doped phosphates, borates, phosphoborate conductive glasses or glass ceramics, NASICON-type or NASICON-like lithium-ion conductors, halide lithium-ion conductors and their composites. These materials have a lithium-ion conductivity of not less than 1×10⁻⁶ at 25°C. -6 S·cm -1 A lithium-containing inorganic lithium-ion conductor is used to construct a chemically stable and ion-continuous solid-solid interface between the inner negative thermal expansion inorganic layer and the solid electrolyte. For example, the outer fast lithium-ion conductive layer is Li2O-B2O3-P2O5-M. a O b Lithium phosphate borate conductive glass or glass ceramic composed of (M is selected from one or more of Al, Si, Zn, and Mg, 1≤a≤3, 1≤b≤3).

[0018] This invention also provides a method for preparing the above-mentioned bifunctional interface lithium-rich manganese-based cathode material, which employs a two-step wet chemical coating process to sequentially construct the inner and outer layers, specifically including the following steps:

[0019] (1) The lithium-rich manganese-based morphological oxide precursor was mixed with a lithium source and calcined to obtain lithium-rich manganese-based morphological oxide core particles.

[0020] (2) The lithium-rich manganese-based morphological oxide core particles obtained in step (1) are dispersed in a sol containing element A and element M. An inner negative thermal expansion inorganic layer is formed in situ on the particle surface through sol-gel coating and heat treatment to obtain the first coating material.

[0021] (3) The first coating material obtained in step (2) is dispersed in a lithium-containing precursor solution, and after drying and glass transition heat treatment, an outer fast lithium-ion conductive layer is formed in situ on the outer side of the inner negative thermal expansion inorganic layer of the first coating material to obtain the bifunctional interface lithium-rich manganese-based cathode material.

[0022] Further, in step (1), the mixed calcination is performed by pre-calcination at 500°C for 5 hours in an air atmosphere, followed by calcination at 3°C·min. -1 Heat to 850℃ and hold for 12 hours.

[0023] Furthermore, in step (2), the heat treatment temperature is 500–800°C, and the time is 1–10 hours. This allows the negative thermal expansion inorganic phase to crystallize in situ on the particle surface.

[0024] Further, in step (2), the sol used in the sol-gel coating process is a water-alcohol mixed solvent system containing element A and element M sources, and further includes at least one of a complexing agent and a gelling agent. The complexing agent is selected from at least one of citric acid and ethylenediaminetetraacetic acid, and the gelling agent is selected from at least one of polyethylene glycol and polyvinyl alcohol. The sol-gel coating process forms a uniformly coated wet gel layer with the help of the complexing agent and the gelling agent.

[0025] Further, in step (2), the lithium-rich manganese-based matrix oxide core particles obtained in step (1) are dispersed in a sol containing element A and element M and stirred or ball-milled for 1 to 10 hours to form a uniform wet gel layer on the particle surface by the A and M element precursors. After drying, heat treatment is performed.

[0026] Further, in step (3), the glass transition heat treatment is carried out at 300–600°C for 0.5–5 hours in an inert or weakly oxidizing atmosphere. This process causes the lithium, boron, phosphorus, and M element precursors to undergo condensation and glass transition reactions on the outer side of the inner negative thermal expansion inorganic layer, forming a continuous or near-continuous ion-conducting outer layer, thereby obtaining bifunctional interface engineering lithium-rich manganese-based cathode particles with a core-shell-shell structure.

[0027] Furthermore, when the outer fast lithium-ion conductive layer is Li2O-B2O3-P2O5-M a O b When constructing a lithium-ion conductive glass or glass-ceramic composed of phosphate borate (M is selected from at least one of Al, Si, Zn, and Mg, 1≤a≤3, 1≤b≤3), in step (3), the lithium-containing precursor solution is obtained by dissolving a lithium salt, a boron source, a phosphorus source, and an M element source in a solvent. The lithium salt is selected from LiNO3, Li2CO3, LiOH, or a combination thereof. The boron source is selected from boric acid, borate esters, or borates. The phosphorus source is selected from phosphoric acid, phosphate esters, or phosphates. The M element source is selected from at least one of nitrates, acetates, or alkoxides containing Al, Si, Zn, and Mg. The molar ratio of lithium, boron, phosphorus, and M element is designed to form an approximate Li2O-B2O3-P2O5-M structure in the glass network. a O b The composition, wherein the molar ratio of Li2O:B2O3:P2O5 is (0.5~2):(0.5~2):(0.5~2), and M a O b The mole fraction relative to the sum of Li2O, B2O3, and P2O5 is 1–30 mol.

[0028] Further, in step (3), the first coating material is dispersed in a lithium-containing precursor solution and stirred for 1 to 10 hours before drying. Through stirring and drying, the precursor is uniformly adsorbed onto the particle surface.

[0029] Furthermore, this invention also provides an application of the aforementioned bifunctional interface lithium-rich manganese-based cathode material in an all-solid-state lithium battery. This invention prepares a cathode composite electrode by mixing the aforementioned bifunctional interface lithium-rich manganese-based cathode material with a sulfide, oxide, halide, or polymer solid electrolyte and a conductive agent. A corresponding type of solid electrolyte sheet or film is used as the electrolyte layer, and metallic lithium, lithium-silicon alloy, or lithium-indium alloy is used as the anode layer to construct an all-solid-state battery. By optimizing the coating thickness and mass fraction, the cathode / electrolyte interface impedance can be significantly reduced in different solid electrolyte systems, improving capacity retention and voltage retention under high voltage and long-cycle conditions.

[0030] Furthermore, the positive electrode active material of the all-solid-state lithium battery is the aforementioned bifunctional interface lithium-rich manganese-based positive electrode material; more specifically, the all-solid-state lithium battery includes a positive electrode layer, a solid electrolyte layer, and a negative electrode layer stacked sequentially: the positive electrode layer includes a positive electrode active material, a solid electrolyte, and a conductive agent, and the positive electrode active material is the aforementioned bifunctional interface engineered lithium-rich manganese-based positive electrode material; the solid electrolyte layer is selected from at least one of sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, polymer solid electrolytes, and their composites; the negative electrode layer is selected from at least one of lithium metal negative electrodes, lithium silicon alloy negative electrodes, and lithium indium alloy negative electrodes.

[0031] Compared with the prior art, the present invention has the following advantages and technical effects:

[0032] (1) The present invention achieves mechanical control of the volume change of the positive electrode of lithium battery through the inner negative thermal expansion inorganic layer. During the preparation and operation of the negative thermal expansion inorganic layer, a favorable stress field is established between it and the lithium-rich positive electrode, which can partially offset the positive thermal expansion of the lithium-rich positive electrode and the chemical expansion caused by lithium intercalation, reduce the equivalent expansion coefficient of the particle surface, thereby reducing particle cracking and the generation and propagation of interface microcracks.

[0033] (2) The present invention achieves interfacial chemical / ionic compatibility with the solid electrolyte through an outer fast lithium-ion conductive layer. The outer layer is selected as a lithium-containing inorganic ion conductor with a similar coefficient of thermal expansion to the solid electrolyte and electrochemical stability within the operating voltage range. It can serve as a chemical buffer layer between the lithium-rich cathode and the solid electrolyte, and also provide a continuous lithium-ion migration channel, effectively suppressing interfacial side reactions and intermediate phase formation, and reducing interfacial ion migration impedance.

[0034] (3) This invention achieves both mechanical and chemical / ionic regulation at the particle scale through the synergistic effect of inner and outer coatings. Compared with solutions that only use inert coatings, single lithium-ion conductive coatings, or single negative thermal expansion coatings, this invention can more comprehensively address the thermo-chemical-mechanical coupling failure problem at the cathode / solid electrolyte interface in all-solid-state batteries, achieving lower interface impedance, smaller voltage decay, and higher cycle stability.

[0035] (4) The preparation process of this invention is simple and suitable for large-scale production. This invention adopts conventional solid-state sintering and sol-gel and glass transition heat treatment steps, without the need for expensive and complex equipment. The process conditions can be adjusted within a wide range, and it is easy to be compatible with existing cathode material preparation production lines, and has good industrialization prospects. Attached Figure Description

[0036] The accompanying drawings, which form part of this invention, 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:

[0037] Figure 1 The images are scanning electron microscope (SEM) images of the cathode material obtained in Example 1 and the uncoated material in Comparative Example 1, where c and d are from Example 1, and a and b are from Comparative Example 1.

[0038] Figure 2 The X-ray diffraction patterns of the cathode material obtained in Example 1 and the uncoated cathode material in Comparative Example 1 are shown below.

[0039] Figure 3 This is a comparison of the first charge-discharge curves of the cathode materials in Example 1 and Comparative Example 1 in an all-solid-state battery;

[0040] Figure 4 This is a comparison chart of the cycle performance of the all-solid-state batteries obtained in Example 1 and Comparative Example 1;

[0041] Figure 5 The curves showing the average discharge voltage of the all-solid-state batteries obtained in Example 1 and Comparative Example 1 as a function of the number of cycles are shown.

[0042] Figure 6 The electrochemical impedance spectra of the interface impedance of the all-solid-state batteries obtained in Example 1 and Comparative Example 1 as a function of cycle number are shown, where a is Comparative Example 1 and b is Example 1. Detailed Implementation

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0045] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0046] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0047] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0048] This invention provides a dual-functional interface lithium-rich manganese-based cathode material, comprising: lithium-rich manganese-based morphological oxide core particles, an inner negative thermal expansion inorganic layer coated on the surface of the lithium-rich manganese-based morphological oxide core particles, and an outer fast lithium-ion conductive layer coated on the outside of the inner negative thermal expansion inorganic layer.

[0049] The general chemical formula of the lithium-rich manganese-based basal oxide core particles is Li. 1+a Mn x Co y Ni z O2, where 0 < a ≤ 0.4, 0.3 ≤ x ≤ 0.6, 0 < y ≤ 0.25, 0 < z ≤ 0.25; more preferably, the chemical formula of the lithium-rich manganese-based layered oxide core particles is Li 1.14 Mn 0.54 Co 0.13 Ni 0.13 O2;

[0050] The inner negative thermal expansion inorganic layer is an oxide ceramic; more preferably, the inner negative thermal expansion inorganic layer is selected from A2M3O. 12 At least one of the following types of oxides, wherein element A is one or more of Sc, Y or rare earth elements, and element M is W or Mo;

[0051] The outer fast lithium-ion conductive layer is selected from at least one of lithium-containing inorganic ionic conductors; more preferably, the outer fast lithium-ion conductive layer is selected from lithium-doped phosphates, borates, phosphoborate conductive glasses or glass ceramics, NASICON-type or NASICON-like lithium-ion conductors, halide lithium-ion conductors and their composites.

[0052] In the preferred embodiment of the bifunctional interface lithium-rich manganese-based cathode material of the present invention, the mass fraction of the inner negative thermal expansion inorganic layer is 0.1–10 wt%, the mass fraction of the outer fast lithium-ion conductive layer is 0.1–10 wt%, and the remainder is lithium-rich manganese-based crystalline oxide core particles; the average thickness of the inner negative thermal expansion inorganic layer is 2–100 nm (preferably 5–50 nm), and the average thickness of the outer fast lithium-ion conductive layer is 2–100 nm (preferably 5–30 nm). By controlling the mass fraction of the inner and outer layers, a balance between stress regulation and ion conduction is achieved.

[0053] In a preferred embodiment of the present invention, the material used for the inner negative thermal expansion inorganic layer is an inorganic oxide with isotropic or near-isotropic negative thermal expansion behavior, and its average linear expansion coefficient in the range of 20 to 200°C is -20 × 10⁻⁶. -6 ~0×10 -6 K -1 It is used to provide circumferential compressive constraint for the volume expansion of lithium-rich manganese-based base oxides.

[0054] In a preferred embodiment of the present invention, the outer fast lithium-ion conductive layer material has a lithium-ion conductivity of not less than 1×10⁻⁶ at 25°C. -6 S·cm -1 A lithium-containing inorganic lithium-ion conductor is used to construct a chemically stable and ion-continuous solid-solid interface between the inner negative thermal expansion inorganic layer and the solid electrolyte.

[0055] This invention also provides a method for preparing the above-mentioned bifunctional interface lithium-rich manganese-based cathode material, which employs a two-step wet chemical coating process to sequentially construct the inner and outer layers, specifically including the following steps:

[0056] (1) The lithium-rich manganese-based morphological oxide precursor was mixed with a lithium source and calcined to obtain lithium-rich manganese-based morphological oxide core particles.

[0057] (2) The lithium-rich manganese-based morphological oxide core particles obtained in step (1) are dispersed in a sol containing element A and element M. An inner negative thermal expansion inorganic layer is formed in situ on the particle surface through sol-gel coating and heat treatment to obtain the first coating material.

[0058] (3) The first coating material obtained in step (2) is dispersed in a lithium precursor solution, and after drying and glass transition heat treatment, an outer fast lithium-ion conductive layer is formed in situ outside the inner negative thermal expansion inorganic layer of the first coating material to obtain a bifunctional interface lithium-rich manganese-based cathode material.

[0059] In step (1) of the preferred embodiment of the present invention, the mixed calcination is performed by pre-calcination at 500°C for 5 hours in an air atmosphere, followed by calcination at 3°C·min. -1 Heat to 850℃ and hold for 12 hours.

[0060] In step (2) of the preferred embodiment of the present invention, the heat treatment temperature is 500-800°C and the time is 1-10 hours. This allows the negative thermal expansion inorganic phase to crystallize in situ on the particle surface.

[0061] In step (2) of the preferred embodiment of the present invention, the sol used in the sol-gel coating process is a water-alcohol mixed solvent system containing element A and element M sources, and further includes at least one of a complexing agent and a gelling agent. The complexing agent is selected from at least one of citric acid and ethylenediaminetetraacetic acid, and the gelling agent is selected from at least one of polyethylene glycol and polyvinyl alcohol. The sol-gel coating process forms a uniformly coated wet gel layer with the help of the complexing agent and the gelling agent.

[0062] In step (2) of the preferred embodiment of the present invention, the lithium-rich manganese-based morphological oxide core particles obtained in step (1) are dispersed in a sol containing element A and element M and stirred or ball-milled for 1 to 10 hours to form a uniform wet gel layer on the particle surface by the A and M element precursors. After drying, heat treatment is performed.

[0063] In step (3) of the preferred embodiment of the present invention, the glass transition heat treatment is carried out at 300-600°C for 0.5-5 hours in an inert or weakly oxidizing atmosphere. This process causes the lithium, boron, phosphorus and M element precursors to undergo condensation and glass transition reactions on the outside of the inner negative thermal expansion inorganic layer, forming a continuous or near-continuous ion-conducting outer layer, thereby obtaining bifunctional interface engineered lithium-rich manganese-based cathode particles with a core-shell-shell structure.

[0064] In a preferred embodiment of the present invention, when the outer fast lithium-ion conductive layer is Li2O-B2O3-P2O5-M a O b When constructing a lithium-ion conductive glass or glass-ceramic composed of phosphate borate (M is selected from one or more of Al, Si, Zn, and Mg, 1≤a≤3, 1≤b≤3), in step (3), the lithium-containing precursor solution is obtained by dissolving lithium salt, boron source, phosphorus source, and M element source in a solvent. The lithium salt is selected from LiNO3, Li2CO3, LiOH, or a combination thereof; the boron source is selected from boric acid, borate ester, or borate; the phosphorus source is selected from phosphoric acid, phosphate ester, or phosphate; and the M element source is selected from at least one of nitrate, acetate, or alkoxide containing Al, Si, Zn, and Mg. The molar ratio of lithium, boron, phosphorus, and M element is designed to form an approximate Li2O-B2O3-P2O5-M in the glass network. a O b The composition, wherein the molar ratio of Li2O:B2O3:P2O5 is (0.5~2):(0.5~2):(0.5~2), and M a O bThe mole fraction relative to the sum of Li2O, B2O3, and P2O5 is 1–30 mol.

[0065] In step (3) of the preferred embodiment of the present invention, the first coating material is dispersed in a lithium-containing precursor solution and stirred for 1 to 10 hours before drying. Through stirring and drying, the precursor is uniformly adsorbed onto the particle surface.

[0066] The technical solution of this invention is not limited to a two-layer structure coating lithium-rich manganese-based basal oxide core particles, but may also include a composite shell with a gradient transition layer, which can be further optimized by introducing a compositional gradient. For example, during the preparation of the inner layer, a small amount of precursor of the outer layer components (Li, B, P) is introduced in advance. After heat treatment, a gradient structure with continuously changing composition from the inner layer to the outer layer is formed (the inner layer region is enriched with A and M elements, and the outer layer region is enriched with Li, B, P, and Al elements). The gradient structure can more smoothly transition the difference in thermal expansion coefficients between the inner layer (NTE material) and the core cathode material, as well as between the inner and outer layers, reducing interfacial stress concentration and theoretically achieving better mechanical stability than a simple two-layer structure. Furthermore, this invention can control the thickness and content of the coating layer by adjusting process parameters (concentration, time), and can flexibly adjust the coating parameters according to different performance requirements (such as focusing more on energy density or cycle life).

[0067] This invention also provides an application of the above-mentioned dual-functional interface lithium-rich manganese-based cathode material in an all-solid-state lithium battery.

[0068] More specifically, the dual-functional interface lithium-rich manganese-based cathode material provided in this embodiment of the invention includes: lithium-rich manganese-based layered oxide core particles (Li... 1.14 Mn 0.54 Co 0.13 Ni 0.13 O2), an inner negative thermal expansion inorganic layer (La-W type NTE inner layer, Nd-Mo type NTE inner layer or YW type NTE inner layer) coated on the surface of lithium-rich manganese-based basal oxide core particles, and an outer fast lithium-ion conductive layer (Li2O-B2O3-P2O5-Al2O3, Li2O-B2O3-P2O5-ZnO, Li2O-B2O3-P2O5-MgO) coated on the outside of the inner negative thermal expansion inorganic layer.

[0069] All raw materials used in the embodiments of this invention were purchased commercially.

[0070] In this embodiment of the invention, room temperature refers to "25±3℃".

[0071] The technical solution of the present invention will be further illustrated by the following embodiments.

[0072] Example 1

[0073] A dual-functional interface lithium-rich manganese-based cathode material includes: lithium-rich manganese-based layered oxide core particles (Li... 1.14 Mn 0.54 Co 0.13 Ni 0.13 The preparation method of the above-mentioned bifunctional interface lithium-rich manganese-based cathode material consists of an inner negative thermal expansion inorganic layer (La-W type NTE inner layer) coated on the surface of lithium-rich manganese-based basal oxide core particles (O2), and an outer fast lithium-ion conductive layer (Li2O-B2O3-P2O5-Al2O3) coated on the outside of the inner negative thermal expansion inorganic layer. The method employs a two-step wet chemical coating process to sequentially construct the inner and outer layers, specifically including the following steps:

[0074] (1) Preparation of lithium-rich manganese-based basal oxide core particles

[0075] Weigh out 30g of Ni according to the molar ratio of Li:Ni:Co:Mn = 1.14:0.13:0.13:0.54. 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 precursor and 13.5 g Li2CO3 were added to 100 mL of anhydrous ethanol and ball-milled in a ball mill jar at 500 r / min for 5 h to obtain a uniformly mixed precursor powder. The precursor powder was placed in a muffle furnace and pre-calcined at 500 °C for 5 h in air atmosphere, and then milled at 3 °C·min. -1 Heating to 850℃ and holding for 12 hours, then furnace cooling to room temperature, yields lithium-rich manganese-based matrix oxide Li. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O2 core particles;

[0076] (2) Preparation of La-W type NTE inner layer

[0077] Preparation of a sol containing La and W: Weigh 0.204 g (0.46 mmol) La(NO3)3·6H2O and 0.175 g (0.069 mmol) ammonium tungstate (NH4)6H2W. 12 O 40 The La:W molar ratio was 1:1.5, which was dissolved in 50 mL of a water / ethanol (volume ratio 1:1, the same below) mixed solvent. 0.452 g of citric acid was added as a complexing agent, and 1 g of polyethylene glycol (average molecular weight 400, mass fraction of 2% in the sol system) was added as a gelling agent. The mixture was stirred to obtain a transparent sol. 10 g of the Li obtained in step (1) was then added... 1.14 Mn 0.54 Co 0.13 Ni 0.13O2 core particles were added to the above sol and magnetically stirred for 4 hours at room temperature, followed by ball milling for 2 hours to ensure the sol uniformly coats the particle surface. The mixture was then dried at 80°C to obtain a powder coated with a wet gel layer. This powder was then air-dried at 3°C / min. -1 Heat to 650℃ and hold for 3 hours to allow La2W3O to oxidize. 12 The negative thermal expansion phase crystallizes in situ on the particle surface, forming a phase with a mass fraction of 2 wt% and an average linear expansion coefficient (measured by a high-temperature X-ray diffractometer in conjunction with a thermal expansion meter, the same below) of -4.3 × 10⁻⁶. -6 K -1 The first coating material is obtained by forming an inner negative thermal expansion inorganic layer with a thickness of 15nm.

[0078] (3) Preparation of the outer layer of Li2O-B2O3-P2O5-Al2O3

[0079] Prepare a precursor solution containing lithium, boron, phosphorus, and Al: Dissolve 0.086 g (1.25 mmol) LiNO3, 0.078 g (1.26 mmol) H3BO3, 0.145 g H3PO4 (85 wt%), and 0.211 g (0.56 mmol) Al(NO3)3·9H2O in 5 mL of a water / ethanol mixture (volume ratio 1:1, i.e., 12.5 mL each) at a predetermined molar ratio to make the equivalent glass composition close to Li2O-B2O3-P2O5-Al2O3, wherein the equivalent molar ratio of Li2O:B2O3:P2O5 is 1:1:1, and the molar fraction of Al2O3 relative to the sum of Li2O, B2O3, and P2O5 is controlled at 9 mol. After stirring to obtain a clear solution, 5g of the first coating material obtained in step (2) was added to the solution, and the mixture was magnetically stirred for 4 hours to allow the precursor to be fully adsorbed on the particle surface. The precursor powder was then dried at 80°C. The powder was placed in an Ar atmosphere and dried at 2°C·min. -1 The temperature was raised to 450℃ and held for 2 hours, causing the Li-BP-Al precursor to undergo condensation and glass transition on the outer side of the negative thermal expansion inner layer, forming a Li2O-B2O3-P2O5-Al2O3 system lithium phosphate borate conductive outer layer. Its lithium-ion conductivity at 25℃ (measured by AC impedance spectroscopy, the same below) was 3.5 × 10⁻⁶. -6 S·cm -1 With an outer layer mass fraction of 3wt% and an average thickness of 10nm, a bifunctional interface lithium-rich manganese-based cathode material, denoted as E1, was obtained.

[0080] Example 2

[0081] A dual-functional interface lithium-rich manganese-based cathode material includes: lithium-rich manganese-based layered oxide core particles (Li... 1.14 Mn0.54 Co 0.13 Ni 0.13 The preparation method of the above-mentioned bifunctional interface lithium-rich manganese-based cathode material consists of an inner negative thermal expansion inorganic layer (Nd-Mo type NTE inner layer) coated on the surface of lithium-rich manganese-based basal oxide core particles (O2), and an outer fast lithium-ion conductive layer (Li2O-B2O3-P2O5-Al2O3) coated on the outside of the inner negative thermal expansion inorganic layer. The method employs a two-step wet chemical coating process to sequentially construct the inner and outer layers, specifically including the following steps:

[0082] (1) Preparation of lithium-rich manganese-based basal oxide core particles

[0083] The preparation method is the same as in Example 1;

[0084] (2) Preparation of Nd-Mo type NTE inner layer

[0085] Preparation of a sol containing Nd and Mo: Weigh 0.206 g (0.46 mmol) of Nd(NO3)3·6H2O and 0.096 g (0.078 mmol) of ammonium molybdate(NH4)6Mo7O. 24 ·4H2O was dissolved in 50mL of a water / ethanol (volume ratio 1:1) mixed solvent at a Nd:Mo molar ratio of 1:1.5. 0.452 g of citric acid was added as a complexing agent, and 1 g of polyethylene glycol with an average molecular weight of 400 was added as a gelling agent. The mixture was stirred to obtain a transparent sol. 10g of the Li obtained in step (1) was then added... 1.14 Mn 0.54 Co 0.13 Ni 0.13 O2 core particles were added to the above sol and magnetically stirred for 4 hours at room temperature, followed by planetary ball milling for 1 hour to ensure the sol uniformly coats the particle surface. The mixture was then dried at 80°C to obtain a powder coated with a wet gel layer. This powder was then air-dried at 3°C / min. -1 Heat to 700℃ and hold for 3 hours to allow Nd2Mo3O to oxidize. 12 The negative thermal expansion phase crystallizes in situ on the particle surface, forming a phase with a mass fraction of 2 wt% and an average linear expansion coefficient of -4.9 × 10⁻⁶. -6 K -1 The first coating material is obtained by forming an inner negative thermal expansion inorganic layer with a thickness of 15nm.

[0086] (3) Preparation of the outer layer of Li2O-B2O3-P2O5-Al2O3

[0087] The preparation method is the same as in Example 1, except that the amount of Al(NO3)3·9H2O is adjusted to 0.141 g (0.375 mmol), and the molar fraction of Al2O3 relative to the sum of Li2O, B2O3, and P2O5 is controlled at 12 mol%. The outer lithium-ion conductivity is 1.5 × 10⁻⁶. -6 S·cm -1 With a mass fraction of 3 wt% and an average thickness of 10 nm, the resulting bifunctional interface lithium-rich manganese-based cathode material is denoted as E2.

[0088] Example 3

[0089] A dual-functional interface lithium-rich manganese-based cathode material includes: lithium-rich manganese-based layered oxide core particles (Li... 1.14 Mn 0.54 Co 0.13 Ni 0.13 The preparation method of the above-mentioned bifunctional interface lithium-rich manganese-based cathode material consists of an inner negative thermal expansion inorganic layer (YW-type NTE inner layer) coated on the surface of the lithium-rich manganese-based basal oxide core particles (O2), and an outer fast lithium-ion conductive layer (Li2O-B2O3-P2O5-Al2O3) coated on the outside of the inner negative thermal expansion inorganic layer. The method employs a two-step wet chemical coating process to sequentially construct the inner and outer layers, specifically including the following steps:

[0090] (1) Preparation of lithium-rich manganese-based basal oxide core particles

[0091] The preparation method is the same as in Example 1;

[0092] (2) Preparation of YW type NTE inner layer

[0093] Preparation of a sol containing Y and W elements: Weigh 0.175 g (0.46 mmol) Y(NO3)3·6H2O and 0.088 g (0.035 mmol) ammonium tungstate (NH4). 10 W 12 O 41 ·4H2O was dissolved in 50 mL of a water / ethanol (volume ratio 1:1.5) mixed solvent at a Y:W molar ratio of 1:1.5. 0.452 g of citric acid was added as a complexing agent, and 1 g of polyethylene glycol (average molecular weight 400) was added as a gelling agent. The mixture was stirred to obtain a transparent sol. 10 g of the Li obtained in step (1) was then added... 1.14 Mn 0.54 Co 0.13 Ni 0.13 O2 core particles were added to the above sol and magnetically stirred for 4 hours at room temperature, followed by planetary ball milling for 1 hour to ensure the sol uniformly coats the particle surface. The mixture was then dried at 80°C to obtain a powder coated with a wet gel layer. This powder was then air-dried at 3°C / min. -1Heat to 600℃ and hold for 5 hours to allow Y2W3O to develop. 12 The negative thermal expansion phase crystallizes in situ on the particle surface, forming a phase with a mass fraction of 1 wt% and an average linear expansion coefficient of -3.3 × 10⁻⁶. -6 K -1 A 10nm thick inner negative thermal expansion inorganic layer is used to obtain the first coating material.

[0094] (3) Preparation of the outer layer of Li2O-B2O3-P2O5-Al2O3

[0095] The preparation method is the same as in Example 1, except that the amount of Al(NO3)3·9H2O is adjusted to 0.211 g (0.56 mmol), and the molar fraction of Al2O3 relative to the sum of Li2O, B2O3, and P2O5 is controlled at 15 mol%. The lithium-ion conductivity of the outer layer is 4.5 × 10⁻⁶. -6 S·cm -1 The bifunctional interface lithium-rich manganese-based cathode material with a mass fraction of 4 wt% and an average thickness of 13 nm is denoted as E3.

[0096] Example 4

[0097] A dual-functional interface lithium-rich manganese-based cathode material includes: lithium-rich manganese-based layered oxide core particles (Li... 1.14 Mn 0.54 Co 0.13 Ni 0.13 The preparation method of the above-mentioned bifunctional interface lithium-rich manganese-based cathode material consists of an inner negative thermal expansion inorganic layer (La-W type NTE inner layer) coated on the surface of lithium-rich manganese-based basal oxide core particles (O2), and an outer fast lithium-ion conductive layer (Li2O-B2O3-P2O5-ZnO) coated on the outside of the inner negative thermal expansion inorganic layer. The method employs a two-step wet chemical coating process to sequentially construct the inner and outer layers, specifically including the following steps:

[0098] (1) Preparation of lithium-rich manganese-based basal oxide core particles

[0099] The preparation method is the same as in Example 1;

[0100] (2) Preparation of La-W type NTE inner layer

[0101] The preparation method is the same as step (2) in Example 1. That is: weigh 0.204 g (0.46 mmol) La(NO3)3·6H2O and 0.175 g (0.069 mmol) (NH4)6H2W of ammonium tungstate. 12 O 40The La:W molar ratio was 1:1.5, which was dissolved in 50 mL of a water / ethanol (volume ratio 1:1, the same below) mixed solvent. 0.452 g of citric acid was added as a complexing agent, and 1 g of polyethylene glycol (average molecular weight 400, mass fraction of 2% in the sol system) was added as a gelling agent. The mixture was stirred to obtain a transparent sol. 10 g of the Li obtained in step (1) was then added... 1.14 Mn 0.54 Co 0.13 Ni 0.13 O2 core particles were added to the above sol and magnetically stirred for 4 hours at room temperature, followed by ball milling for 2 hours to ensure the sol uniformly coats the particle surface. The mixture was then dried at 80°C to obtain a powder coated with a wet gel layer. This powder was then air-dried at 3°C / min. -1 Heat to 650℃ and hold for 3 hours to allow La2W3O to oxidize. 12 The negative thermal expansion phase crystallizes in situ on the particle surface, forming a phase with a mass fraction of 2 wt% and an average linear expansion coefficient of -4.3 × 10⁻⁶. -6 K -1 The first coating material is obtained by forming an inner negative thermal expansion inorganic layer with a thickness of 15nm.

[0102] (3) Preparation of the outer layer of Li2O-B2O3-P2O5-ZnO

[0103] Prepare a precursor solution containing lithium, boron, phosphorus, and zinc: Accurately weigh 0.0778 g (1.129 mmol) of LiNO3, 0.0697 g (1.128 mmol) of H3BO3, 0.1300 g of 85 wt% H3PO4 aqueous solution (corresponding to 0.1105 g of pure H3PO4, 1.128 mmol), and 0.0503 g (0.169 mmol) of Zn(NO3)2·6H2O. Dissolve the ZnO in 25 mL of a water / ethanol (volume ratio 1:1) mixed solvent according to the equivalent oxide molar ratio of Li2O:B2O3:P2O5:ZnO = 1:1:1:0.3 (i.e., the molar fraction of ZnO relative to the sum of Li2O, B2O3, and P2O5 is 9.1%). After obtaining a clear solution by stirring, 5g of the first coating material obtained in step (2) was added to the solution, and the mixture was magnetically stirred for 4 hours to allow the precursor to be fully adsorbed. The mixture was then dried at 80°C. The precursor powder was placed in an Ar atmosphere and dried at 2°C·min. -1 The temperature was raised to 450℃ and held for 2 hours to induce condensation and glass transition of the precursor, forming a Li₂O-B₂O₃-P₂O₅-ZnO lithium phosphate borate conductive outer layer with a lithium-ion conductivity of 5.2 × 10⁻⁶. -6 S·cm -1 The mass fraction was 3 wt%, and the average thickness was 12 nm. The resulting bifunctional interface lithium-rich manganese-based cathode material is denoted as E4.

[0104] Example 5

[0105] A dual-functional interface lithium-rich manganese-based cathode material includes: lithium-rich manganese-based layered oxide core particles (Li... 1.14 Mn 0.54 Co 0.13 Ni 0.13 The preparation method of the above-mentioned bifunctional interface lithium-rich manganese-based cathode material consists of an inner negative thermal expansion inorganic layer (La-W type NTE inner layer) coated on the surface of lithium-rich manganese-based basal oxide core particles (O2), and an outer fast lithium-ion conductive layer (Li2O-B2O3-P2O5-MgO) coated on the outside of the inner negative thermal expansion inorganic layer. The method employs a two-step wet chemical coating process to sequentially construct the inner and outer layers, specifically including the following steps:

[0106] (1) Preparation of lithium-rich manganese-based basal oxide core particles

[0107] The preparation method is the same as in Example 1;

[0108] (2) Preparation of La-W type NTE inner layer

[0109] The preparation method is the same as step (2) in Example 1, and the first coating material is obtained.

[0110] (3) Preparation of the outer layer of Li2O-B2O3-P2O5-MgO

[0111] Prepare a precursor solution containing lithium, boron, phosphorus, and magnesium: Accurately weigh 0.0816 g (1.184 mmol) of LiNO3, 0.0732 g (1.184 mmol) of H3BO3, 0.1365 g of 85 wt% H3PO4 aqueous solution (corresponding to 0.1160 g of pure H3PO4, 1.184 mmol), and 0.0455 g (0.178 mmol) of Mg(NO3)2·6H2O. Dissolve the MgO in 25 mL of a water / ethanol (volume ratio 1:1) mixed solvent according to the equivalent oxide molar ratio of Li2O:B2O3:P2O5:MgO = 1:1:1:0.3 (i.e., the molar fraction of MgO relative to the sum of Li2O, B2O3, and P2O5 is 9.1%). After obtaining a clear solution by stirring, 5g of the first coating material obtained in step (2) was added to the solution, and the mixture was magnetically stirred for 4 hours to allow the precursor to be fully adsorbed. The mixture was then dried at 80°C. The precursor powder was placed in an Ar atmosphere and dried at 2°C·min. -1 The temperature was raised to 450℃ and held for 2 hours to induce condensation and glass transition of the precursor, forming a Li₂O-B₂O₃-P₂O₅-MgO phosphate lithium-ion conductive outer layer with a lithium-ion conductivity of 4.9 × 10⁻⁶. -6 S·cm -1The mass fraction was 3 wt%, and the average thickness was approximately 12 nm. The resulting bifunctional interface lithium-rich manganese-based cathode material is designated as E5.

[0112] Example 6

[0113] Based on Example 1, a bifunctional interface layer with a compositional gradient is formed through a stepwise construction process. First, a small amount of glass network forgings are pre-introduced into the NTE precursor sol, followed by pre-firing to form an enriched region within the NTE phase. Then, a second coating rich in glass network forgings is performed to form an outer enriched region, thus creating a gradient structure with continuously changing composition from the inside out. The specific steps are as follows:

[0114] (1) Preparation of lithium-rich manganese-based basal oxide core particles

[0115] The preparation method is the same as in Example 1.

[0116] (2) Preparation of the inner layer of the gradient structure (NTE phase enrichment region)

[0117] Preparation of precursor sols containing La, W, and small amounts of Li, B, and P: Weigh 0.204 g of La(NO3)3·6H2O and (NH4)6H2W. 12 O 40 0.175 g of LiNO3, 0.022 g of H3BO3, and 0.036 g of 85 wt% H3PO4 aqueous solution were dissolved together in 50 mL of a water / ethanol (volume ratio 1:1) mixed solvent. 0.452 g of citric acid and 1 g of polyethylene glycol (average molecular weight 400) were added, and the mixture was stirred until completely dissolved to obtain a transparent sol. 10 g of the core particles obtained in step (1) were added to the sol and magnetically stirred at room temperature for 4 h to ensure uniform coating. The sol was then dried at 80 °C to obtain a powder coated with the composite precursor. The powder was then exposed to air at 3 °C·min. -1 The temperature was raised to 550℃ and held for 3 hours for pre-firing. During this process, La2W3O 12 The negative thermal expansion phase preferentially crystallizes and enriches in the region near the core particles, forming an inner layer enriched with the NTE phase, with a mass fraction of 1.5 wt% and an average thickness of 15 nm. Measurements using a high-temperature X-ray diffractometer combined with a thermal expansion meter showed that the average linear expansion coefficient of this layer was -4.3 × 10⁻⁶ °C in the range of 30–600 °C. -6 K -1 .

[0118] (3) Construction of the outer layer of the gradient structure (glass phase enrichment region)

[0119] Prepare a precursor solution rich in Li, B, P, and Al elements: Weigh 0.086 g of LiNO3, 0.078 g of H3BO3, 0.145 g of 85wt% H3PO4 aqueous solution, and 0.211 g of Al(NO3)3·9H2O, and dissolve them in 25 mL of a water / ethanol (volume ratio 1:1) mixed solvent. Add 5 g of the pre-calcined powder obtained in step (2) to this solution, magnetically stir and impregnate for 4 h, and dry at 80 °C. Then place the dried powder in an Ar atmosphere tube furnace and heat at 2 °C·min. -1 The temperature was raised to 450℃ and held for 2 h to induce condensation and vitrification reactions in the surface Li-BP-Al precursor, forming a glassy phase enriched on the outer surface with a mass fraction of 1.5 wt% and an average thickness of approximately 20 nm. Electron impedance spectroscopy analysis showed that the lithium-ion conductivity of this outer glass material at 25℃ was 4.5 × 10⁻⁶ S·cm. -1 Finally, a compositional gradient interface layer with a total mass fraction of 3 wt% and a total thickness of 35 nm was constructed using the above two-step method. The resulting material is denoted as E6.

[0120] Example 7

[0121] Based on Example 1, a cathode material with an ultrathin dual-functional interface layer was prepared by precisely controlling the coating amount, with the aim of applying it to a high areal capacity electrode.

[0122] (1) Preparation of lithium-rich manganese-based basal oxide core particles

[0123] The preparation method is the same as in Example 1.

[0124] (2) Fabrication of ultrathin La-W type NTE inner layer

[0125] Preparation of low-concentration sol: Weigh 0.051 g of La(NO3)3·6H2O (1 / 4 of the amount used in Example 1) and (NH4)6H2W 12 O40 0.044 g was dissolved in 50 mL of a water / ethanol (volume ratio 1:1) mixture. Citric acid 0.113 g and polyethylene glycol (average molecular weight 400) 0.25 g were added, and the mixture was stirred to obtain a transparent sol. 10 g of core particles were added to the sol and magnetically stirred for 1 h at room temperature (to shorten the impregnation time and control the adsorption amount), followed by drying at 80 °C. The dried powder was then air-dried at 3 °C / min. -1 Heating to 650℃ and holding for 3 hours resulted in the crystallization of an ultrathin La2W3O layer. 12 Inner layer. This inner layer has a precisely controlled mass fraction of 0.5 wt% and an average thickness of 8 nm. Its average coefficient of linear expansion is measured to be -3.8 × 10⁻⁶. -6 K -1 .

[0126] (3) Preparation of ultrathin Li2O-B2O3-P2O5-Al2O3 outer layer

[0127] Preparation of a low-concentration precursor solution: Weigh 0.043 g of LiNO3, 0.039 g of H3BO3, 0.073 g of 85 wt% H3PO4 aqueous solution, and 0.106 g of Al(NO3)3·9H2O (all half the amounts used in Example 1), and dissolve them in 25 mL of a water / ethanol (volume ratio 1:1) mixed solvent. Add 5 g of the powder with the inner layer obtained in step (2) to the solution, stir magnetically and impregnate for 2 h, and dry at 80 °C. Place the dried powder in an Ar atmosphere and heat at 2 °C·min. -1 The temperature was raised to 450℃ and held for 2 hours to form an ultrathin glass outer layer. The mass fraction of this outer layer was precisely controlled at 1.5 wt%, with an average thickness of 7.5 nm. Its lithium-ion conductivity was 3.7 × 10⁻⁶. -6 S·cm -1 The final cathode material with an ultrathin double shell (total thickness ~15.5 nm) was obtained, denoted as E7.

[0128] Comparative Example 1

[0129] The uncoated cathode material, i.e., the lithium-rich manganese-based layered oxide Li prepared according to step (1) of Example 1. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O2 core particles are used directly as the positive electrode material.

[0130] Comparative Example 2

[0131] Same as Example 1, except that it only has a negative thermal expansion inner layer and no Li2O-B2O3-P2O5-Al2O3 outer layer. The preparation method is the same as steps (1) and (2), that is, in this comparative example, the first coating material obtained in Example 1 is used as the positive electrode material.

[0132] Comparative Example 3

[0133] Same as Example 1, except that it only has an outer layer of Li2O-B2O3-P2O5-Al2O3 and no inner layer with negative thermal expansion. The preparation method is as follows:

[0134] (1) Same as Example 1;

[0135] (2) Preparation of precursor solution containing lithium, boron, phosphorus and Al: Take 0.086 g (1.25 mmol) LiNO3, 0.078 g (1.26 mmol) H3BO3, 0.145 g H3PO4 and 0.211 g (0.56 mmol) Al(NO3)3·9H2O in a predetermined molar ratio and dissolve them in 25 mL of water / ethanol mixed solvent to make the equivalent glass composition close to Li2O-B2O3-P2O5-Al2O3, wherein the equivalent molar ratio of Li2O:B2O3:P2O5 is 1:1:1, and the molar fraction of Al2O3 relative to the sum of Li2O, B2O3 and P2O5 is controlled at 18 mol%. After stirring to obtain a clear solution, add 5 g of lithium-rich manganese base oxide Li obtained in step (1) 1.14 Mn 0.54 Co 0.13 Ni 0.13 O2 core particles were added to the solution, and the mixture was magnetically stirred for 4 hours to allow the precursor to be fully adsorbed onto the particle surface. The mixture was then dried at 80°C to obtain the precursor powder. This powder was then placed in an Ar atmosphere and dried at 2°C / min. -1 The temperature was raised to 450℃ and held for 2 hours to form a Li2O-B2O3-P2O5-Al2O3 system lithium phosphate borate conductive outer layer with a mass fraction of 3wt% and an average thickness of 10nm, thus obtaining the cathode material.

[0136] Application Example 1

[0137] In an inert atmosphere glove box, the samples obtained in Examples 1-7 or the positive electrode materials obtained in Comparative Examples 1-3, the sulfide solid electrolyte Li6PS5Cl, and the conductive agent Super P were mixed and ground in a mass ratio of 60:35:5, and then cold-pressed into positive electrode sheets. Using the Li6PS5Cl sheet as the solid electrolyte layer and the lithium metal sheet as the negative electrode, they were stacked into a Li|Li6PS5Cl|E1 structure and cold-pressed under 300 MPa pressure. The battery was tested for its first charge-discharge curve at 25°C, a voltage range of 2.0–4.5V, and 0.1C, and then subjected to long-cycle testing and electrochemical impedance spectroscopy at 25–60°C and 1C.

[0138] The specific capacity, initial coulombic efficiency, and 1C long-cycle stability test results of the examples and comparative examples at 0.1 C are shown in Table 1.

[0139] Table 1. Test results of the first charge-discharge specific capacity and initial coulombic efficiency of each embodiment and comparative example at 0.1 C.

[0140] 0.1C First Charge Capacity (mAh / g) 0.1 C first-cycle discharge specific capacity (mAh / g) 0.1 C First-lap Coulomb efficiency (%) 100-cycle capacity retention (%) Example 1 312.4 269.6 86.3 94.3 Example 2 311.9 265.6 85.2 92.2 Example 3 319.6 261.2 81.7 91.2 Example 4 316.3 263.1 83.2 93.4 Example 5 313.7 265.5 84.6 95.2 Example 6 317.2 266.4 84.0 90.3 Example 7 320.2 268.2 83.8 93.9 Comparative Example 1 318.3 260.4 81.8 80.1 Comparative Example 2 316.1 261.1 82.6 83.3 Comparative Example 3 317.3 262.3 82.6 85.8

[0141] The results are shown in Table 1. The bifunctional interface lithium-rich manganese-based cathode materials (Examples 1-7) of this invention were subjected to first-cycle charge-discharge tests at 0.1 C. The results showed that the first-cycle charge specific capacity of the examples was 311.9–320.2 mAh / g, the first-cycle discharge specific capacity was 261.2–269.6 mAh / g, and the first-cycle coulombic efficiency was 81.7%–86.3%. Example 1 showed the best performance, with a first-cycle discharge specific capacity of 269.6 mAh / g and a first-cycle coulombic efficiency of 86.3%. In contrast, the first-cycle charge specific capacity of Comparative Examples 1–3 was 316.1–318.3 mAh / g, the first-cycle discharge specific capacity was 260.4–262.3 mAh / g, and the first-cycle coulombic efficiency was 81.8%–82.6%. Furthermore, the bifunctional interface lithium-rich manganese-based cathode material (Examples 1-7) of this invention was subjected to long-term cycle stability tests under 1C conditions. The results showed that the capacity retention rate after 100 cycles was higher than that of the unmodified comparative samples 1-3. This further demonstrates that this bifunctional interface design has significant advantages in the interfacial stability between the solid electrolyte and the lithium-rich cathode, and can effectively alleviate interfacial side reactions and stress-strain accumulation caused by solid-solid contact. It can be seen that while maintaining a high charge specific capacity, the material of this invention has a higher overall first-cycle discharge specific capacity (up to approximately 7.3 mAh / g), and the first-cycle coulombic efficiency is significantly improved in most examples (up to approximately 3.7 percentage points). This indicates that through the synergistic coating of "inner negative thermal expansion inorganic layer + outer lithium-ion conductive layer", mechanical matching and ionic / chemical regulation can be taken into account at the particle scale, reducing irreversible losses in the first cycle, thereby providing a performance basis for reducing interfacial impedance, suppressing voltage decay, and improving cycle stability.

[0142] Figure 1 The images are scanning electron microscope (SEM) images of the cathode material obtained in Example 1 and the uncoated material in Comparative Example 1, where c and d are from Example 1, and a and b are from Comparative Example 1. Figure 2 The X-ray diffraction patterns are those of the cathode material obtained in Example 1 and the uncoated cathode material in Comparative Example 1. Figure 1 The SEM images of Comparative Example 1 show that the surface of the lithium-rich manganese-based particles is relatively smooth and lacks a continuous and dense shell structure; while the SEM images of Example 1 show that the particle surface is uniformly covered with a shell layer, and the morphology shows obvious coating characteristics, indicating that the negative thermal expansion inner layer and the subsequently formed glass outer layer have been constructed in situ on the surface of the lithium-rich particles through sol-gel and heat treatment. Figure 2The XRD patterns show that, in both Comparative Example 1 and Example 1, the main diffraction peaks correspond to the lithium-rich manganese-based matrix structure. Furthermore, no obvious additional crystalline phase peaks appeared in Example 1, indicating that the NTE inner layer and the Li₂O-B₂O₃-P₂O₅-Al₂O₃ outer layer exist in low content and / or amorphous form, without disrupting the main crystalline structure of the cathode. This result demonstrates that the interface engineering of this invention can maintain the integrity of the lithium-rich manganese-based matrix phase while obtaining the composite coating layer, laying the foundation for subsequently achieving high capacity and high voltage advantages.

[0143] Figure 3 This is a comparison of the first charge-discharge curves of the cathode materials obtained in Example 1 and Comparative Example 1 in an all-solid-state battery; Figure 4 This is a comparison chart of the cycle performance of the all-solid-state batteries obtained in Example 1 and Comparative Example 1; Figure 5 The graphs show the average discharge voltage of the all-solid-state batteries obtained in Example 1 and Comparative Example 1 as a function of cycle number. Figure 3 As can be seen from the comparison of the first charge-discharge curves of Example 1 and Comparative Example 1, the polarization of the all-solid-state battery of the present invention is significantly reduced in the high-voltage region, the voltage hysteresis is reduced, and the charge-discharge platform is smoother, which verifies that the double-coating structure can effectively reduce interface impedance and improve the dynamic process. Figure 4 The cycling performance curves shown indicate that, under the same voltage range and rate conditions, the capacity of Comparative Example 1 decays rapidly with cycling, while the capacity retention rate of Example 1 is significantly higher and the decay slope is gentler. Figure 5 The variation of average discharge voltage with the number of cycles further indicates that the average discharge voltage of Comparative Example 1 decreases rapidly with cycling, showing significant voltage decay, while the average discharge voltage decay rate of Example 1 is significantly slowed down. This shows that the interface engineering of the present invention not only improves capacity retention but also effectively suppresses the voltage decay problem of lithium-rich cathode in all-solid-state systems.

[0144] Figure 6 The electrochemical impedance spectroscopy (EIS) spectra of the interface impedance of the all-solid-state batteries obtained in Example 1 and Comparative Example 1 as a function of cycling cycles are shown, where a represents Comparative Example 1 and b represents Example 1. It can be seen that Comparative Example 1 has a higher initial interface impedance, which increases rapidly with cycling. The high-frequency semicircles in the Nyquist plot gradually enlarge, indicating continuous degradation of the cathode / solid electrolyte interface, a decrease in contact area, and an intensification of interfacial side reactions. In contrast, the initial interface impedance of the battery in Example 1 is significantly lower, and the increase with cycling is smaller, indicating that the negative thermal expansion inner layer and the Li2O-B2O3-P2O5-Al2O3 outer layer can maintain a more stable interfacial contact and chemical environment during cycling, effectively suppressing the rapid growth of interfacial cracks, pores, and the passivation layer. This is consistent with... Figures 3-5 The smaller polarization, slower capacity decay, and improved voltage retention reflected in the data are highly consistent.

[0145] Application Example 2

[0146] In an inert atmosphere glove box, sample E1 from Example 1, sulfide solid electrolyte Li3InCl6, and conductive agent SuperP were mixed and ground at a mass ratio of 50:45:5, and then cold-pressed into a positive electrode sheet. Using Li3InCl6 sheets as the solid electrolyte layer and Li-In alloy sheets as the negative electrode, they were stacked to form a Li-In|Li3InCl6|E1 structure and cold-pressed under 300 MPa pressure. The battery was tested for its first charge-discharge curve at 25°C, a voltage range of 2.0–4.5V, and 0.1C, and its long-term cycle stability was tested at 25–60°C and 0.2C.

[0147] Application Example 3

[0148] In an inert atmosphere glove box, sample E1 from Example 1 and cubic phase Li7La3Zr2O were placed... 12 LLZO and conductive agent SuperP were mixed and ground in a mass ratio of 55:40:5, and then cold-pressed into a positive electrode sheet. LLZO sheets were used as the solid electrolyte layer, and lithium-silicon alloy was used as the negative electrode, stacked into a Li-Si|LLZO|E1 structure, and cold-pressed under 300 MPa pressure. The battery's first-cycle charge-discharge curves were tested at 25℃, a voltage range of 2.0–4.5V, and 0.1C, and long-cycle stability tests were conducted at 25–60℃ and 0.2C.

[0149] Application Example 4

[0150] In an inert atmosphere glove box, the positive electrode material E1 from Example 1, PEO-LiTFSI-SiO2, and conductive agent SuperP were mixed and ground at a mass ratio of 60:35:5, and then cold-pressed into a positive electrode sheet. Using a PEO-LiTFSI-SiO2 film as the solid electrolyte layer and lithium metal as the negative electrode, the layers were stacked to form a Li or Li-In|PEO-LiTFSI-SiO2|E1 structure, and cold-pressed under 300 MPa pressure. The battery was tested for its first charge-discharge curve at 25°C, a voltage range of 2.0–4.5V, and 0.1C, and its long-term cycle stability was tested at 25–60°C and 0.2C.

[0151] Table 2 shows the test results of the specific capacity and initial coulombic efficiency of the lithium-ion batteries obtained from Examples 2-4 at 0.1 C during the first charge-discharge cycle.

[0152] Table 2 Performance test results of application examples 2-4

[0153] 0.1C First Charge Capacity (mAh / g) 0.1 C first-cycle discharge specific capacity (mAh / g) 0.1 C First-lap Coulomb efficiency (%) 100-cycle capacity retention (%) Application Example 2 314.5 268.4 85.3 91.4 Application Example 3 321.2 271.2 84.4 94.1 Application Example 4 312.4 266.7 85.4 93.4

[0154] As can be seen from the data in Table 2, the cathode material prepared in Example 1 of this invention can be applied to battery systems under different solid electrolytes, and all of them have higher discharge specific capacity and long cycle stability, indicating that the dual-function interface design can effectively improve the stability of the solid-solid contact interface in solid batteries.

[0155] Application Example 5

[0156] The E6 material prepared in Example 6 was mixed with a sulfide-germanium ore-type solid electrolyte Li6PS5Cl and conductive carbon black at a mass ratio of 55:40:5 to prepare a positive electrode composite sheet. A Li-In alloy|Li6PS5Cl|E6 all-solid-state battery was assembled and tested. Electrochemical impedance spectroscopy (EIS) showed that the total interfacial impedance (Rint) of the battery before cycling was 128 Ω·cm. 2 After 200 cycles at 0.2C and 25°C, the Rint increased to 285 Ω·cm. 2 The average capacity decay rate per revolution was 0.062%, and the voltage decay rate was 0.18 mV / revolution. For comparison, the initial Rint of sample E1 from Example 1, tested under the same conditions, was 185 Ω·cm. 2 After 200 cycles, it increases to 420 Ω·cm 2 The average capacity decay rate per revolution was 0.085%, and the voltage decay rate was 0.25 mV / revolution. Test data indicate that the E6 material with a composition gradient interface layer can more effectively alleviate the internal stress of the shell caused by volume changes during charging and discharging, thus exhibiting a lower interface impedance growth rate and superior voltage stability.

[0157] Application Example 6

[0158] Using E7 prepared in Example 7 as the positive electrode active material, it was mixed with Li6PS5Cl solid electrolyte and conductive agent Super P at a mass ratio of 70:25:5. By increasing the tableting pressure and the active material loading, an isometric capacity of 4.2 mAh·cm⁻¹ was obtained. -2 High-capacity cathode sheet. Assembled Li-In|Li6PS5Cl|E7 all-solid-state battery for testing.

[0159] Long-cycle testing was conducted at 0.1C (based on high areal capacity) and 25℃. The battery's first-cycle discharge specific capacity was 162 mAh·g. -1 (Based on E7 mass), the corresponding area capacity is 4.07 mAh·cm³. -2 After 100 cycles, the capacity retention rate was 89.5%, and the areal capacity remained at 3.64 mAh·cm³. -2 Electrochemical impedance spectroscopy (EIS) tests showed that the interfacial impedance before cycling was 205 Ω·cm. 2After 100 cycles, it increases to 380 Ω·cm 2 As a reference, uncoated material (Comparative Example 1) was used with a similar areal capacity (4.0 mAh·cm⁻¹). -2 The battery assembled under these conditions exhibited a rapid capacity decay after the first discharge cycle, with the capacity retention dropping to 72.1% after 50 cycles, and the interface impedance rapidly increasing to 600 Ω·cm. 2 The results show that even under the severe interface challenges brought about by high areal capacity, the ultrathin bifunctional interface layer of E7 can still effectively maintain interface contact, suppress side reactions and impedance growth, and significantly improve interface cycling stability while ensuring high energy density.

[0160] In summary, this invention constructs an "inner layer of negative thermal expansion inorganic layer + outer layer of Li2O-B2O3-P2O5-M" on the surface of a lithium-rich manganese-based basal oxide. a O b The dual-functional interface structure of the "phosphoborate fast lithium-ion conductive layer" achieves synergy between mechanical stress regulation and interface chemical / ionic regulation, exhibiting excellent interface stability and electrochemical performance for different types of solid electrolytes, thus verifying the effectiveness and innovation of the technical solution of this invention.

[0161] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A bifunctional interface lithium-rich manganese-based cathode material, characterized in that, include: The lithium-rich manganese-based morphological oxide core particles, an inner negative thermal expansion inorganic layer covering the surface of the lithium-rich manganese-based morphological oxide core particles, and an outer fast lithium-ion conductive layer covering the outer side of the inner negative thermal expansion inorganic layer. The chemical general formula of the lithium-rich manganese-based layered oxide core particle is Li 1+a Mn x Co y Ni z O2, wherein 0 O2, wherein 0 O2, wherein 0 O2, wherein 0 The inner negative thermal expansion inorganic layer is selected from A2M3O 12 The inner layer is an inorganic oxide of at least one type, wherein element A is one or more of Sc and Y, element M is W or Mo, and the inner layer is an inorganic oxide with isotropic negative thermal expansion behavior, having an average linear expansion coefficient of -20 × 10⁻⁶ in the range of 20–200 °C. -6 ~0×10 -6 K -1 A negative thermal expansion inner layer was constructed in situ on the surface of lithium-manganese-rich base-like oxide core particles by sol-gel and heat treatment. The outer fast lithium-ion conductive layer is selected from lithium-ion conductors, and the outer fast lithium-ion conductive layer has a lithium-ion conductivity of not less than 1×10⁻⁶ at 25°C. -6 S·cm -1 The lithium-containing inorganic lithium-ion conductor is formed, and a continuous ion-conducting outer layer is formed on the outside of the inner negative thermal expansion inorganic layer.

2. The bifunctional interface lithium-rich manganese-based cathode material according to claim 1, characterized in that, In the bifunctional interface lithium-rich manganese-based cathode material, the inner negative thermal expansion inorganic layer has a mass fraction of 0.1–10 wt%, the outer fast lithium-ion conductive layer has a mass fraction of 0.1–10 wt%, and the remainder is the lithium-rich manganese-based morphological oxide core particles.

3. The bifunctional interface lithium-rich manganese-based cathode material according to claim 2, characterized in that, The average thickness of the inner negative thermal expansion inorganic layer is 2–100 nm, and the average thickness of the outer fast lithium-ion conductive layer is 2–100 nm.

4. A method for preparing the bifunctional interface lithium-rich manganese-based cathode material according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) The lithium-rich manganese-based morphological oxide precursor was mixed with a lithium source and calcined to obtain lithium-rich manganese-based morphological oxide core particles. (2) The lithium-rich manganese-based morphological oxide core particles obtained in step (1) are dispersed in a sol containing element A and element M. An inner negative thermal expansion inorganic layer is formed in situ on the particle surface through sol-gel coating and heat treatment to obtain the first coating material. (3) The first coating material obtained in step (2) is dispersed in a lithium-containing precursor solution, and after drying and glass transition heat treatment, an outer fast lithium-ion conductive layer is formed in situ on the outer side of the inner negative thermal expansion inorganic layer of the first coating material to obtain the bifunctional interface lithium-rich manganese-based cathode material.

5. The method for preparing the bifunctional interface lithium-rich manganese-based cathode material according to claim 4, characterized in that, In step (1), the mixed calcination is performed by pre-calcining at 500°C for 5 hours in an air atmosphere, followed by calcination at 3°C·min. -1 Heat to 850℃ and hold for 12 hours.

6. The method for preparing the bifunctional interface lithium-rich manganese-based cathode material according to claim 4, characterized in that, In step (2), the heat treatment temperature is 500-800℃ and the time is 1-10 hours.

7. The method for preparing the bifunctional interface lithium-rich manganese-based cathode material according to claim 4, characterized in that, In step (3), the glass transition heat treatment is performed by holding the glass at 300-600°C for 0.5-5 hours in an inert atmosphere.

8. The application of a bifunctional interface lithium-rich manganese-based cathode material as described in any one of claims 1 to 3 in the preparation of all-solid-state lithium batteries.

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