A core-shell material, its preparation method, a negative electrode material, and a battery.

Abstract

This invention relates to the field of battery technology, and particularly to a core-shell material, a preparation method, a negative electrode material, and a battery. The method provided by this invention includes processing metal salts of aluminum, iron, cobalt, nickel, zinc, and lanthanum into high-entropy metal oxides; using silicon particles as the core layer, vaporizing the high-entropy metal oxides and depositing them on the surface of the core layer to form a coating layer to obtain Si@HEO particles; depositing a zinc layer on the Si@HEO particles to form a growth layer on the surface of the coating layer, then dispersing it in a Si@HEO solvent and adding an aqueous solution of zinc nitrate and 2-methylimidazole to react, causing the growth layer on the surface of the coating layer to grow a shell layer to obtain Si@HEO@ZIF particles; mixing the acidic solution with the Si@HEO@ZIF particles to form secondary channels, and then separating to obtain the core-shell material. The core-shell material provided by this invention solves the problems of low stress dispersion efficiency, low ion transport, and poor volume expansion rate of existing core-shell materials.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a core-shell material, a preparation method, a negative electrode material, and a battery. Background Technology

[0002] Single or few metal oxides, such as Al2O3 or TiO2, have limited mechanical properties and low compressive stress dispersion efficiency, failing to effectively alleviate the volume expansion problem of silicon anodes. High-entropy oxides, as a novel material composed of multiple metal elements, have attracted widespread attention in catalysts, energy storage materials, and other fields due to their excellent structural stability and multifunctionality. However, existing high-entropy oxides exhibit weak interfacial bonding with other functional layers, such as organic or carbon materials, lacking effective anchoring points, leading to easy delamination of the composite structure of high-entropy oxides with other functional layers. Summary of the Invention

[0003] To address the problems of low stress dispersion efficiency, low ion transport, and poor volume expansion rate in existing core-shell materials, this invention provides a core-shell material, a preparation method, a negative electrode material, and a battery.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a core-shell material, the method comprising: providing metal salt raw materials of aluminum, iron, cobalt, nickel, zinc and lanthanum; pretreating the metal salt raw materials into high-entropy metal oxides; providing silicon particles as a core layer; vaporizing the high-entropy metal oxides in a micro-oxygen environment and depositing them on the surface of the core layer to form a coating layer on the surface of the core layer to obtain Si@HEO particles; depositing zinc in at least a portion of the outer surface of the coating layer to form a growth layer on the outer surface of the coating layer; providing an aqueous solution of zinc nitrate, an aqueous solution of 2-methylimidazole and a Si@HEO solvent; dispersing the Si@HEO particles forming the growth layer in the Si@HEO solvent; adding the aqueous solution of zinc nitrate and the aqueous solution of 2-methylimidazole to grow a shell layer on the growth layer to obtain Si@HEO@ZIF particles; providing an acidic solution; mixing the acidic solution and the Si@HEO@ZIF particles, wherein the acidic solution etches the outer surface of the shell layer of the Si@HEO@ZIF particles to form secondary channels; and performing separation processing to obtain the core-shell material.

[0005] Preferably, the pretreatment of metal salt raw materials into high-entropy metal oxides includes: providing deionized water and an alcohol solution, mixing the deionized water and alcohol solvent to form a metal salt solvent; providing metal salt raw materials of aluminum, iron, cobalt, nickel, zinc, and lanthanum; dissolving the metal salt precursors of iron, cobalt, nickel, zinc, and lanthanum in the metal salt solvent to form a gel; adding aluminum metal salt raw materials when the gel begins to form to obtain a gel product; and subjecting the gel product to drying and calcination to obtain a high-entropy oxide.

[0006] Preferably, the process of drying and calcining the gel product to obtain the high-entropy oxide includes the following steps: the gel product is heated from room temperature to 80-120°C at a heating rate of 1-5°C / min, held at that temperature for 6-12 hours, and then cooled to room temperature to complete the drying process; after drying, the gel product is heated from room temperature to 500-700°C at a heating rate of 2-5°C / min, held at that temperature for 2-4 hours, and then cooled to room temperature to complete the calcination process.

[0007] Preferably, the molar ratio of aluminum, iron, cobalt, nickel, zinc and lanthanum in the high-entropy oxide is aluminum:iron:cobalt:nickel:zinc:lanthanum = (0.08~0.16):(0.20~0.30):(0.15~0.25):(0.20~0.28):(0.08~0.15):(0.05~0.12); the particle size of the high-entropy metal oxide is 20~50nm, and the particle size distribution of the high-entropy metal oxide is less than 0.3.

[0008] Preferably, growing a shell layer on the growth layer includes: dispersing Si@HEO particles of the deposited zinc layer in a Si@HEO solvent to obtain a first mixed solution, wherein the volume ratio of Si@HEO particles to Si@HEO solvent in the mixed solution is 1:(10-20), and the Si@HEO solvent is a mixture of alcohol and ionic liquid, wherein the volume percentage of the ionic liquid is 5-30%; adding zinc nitrate aqueous solution and 2-methylimidazole aqueous solution to the first mixed solution, heating from room temperature to 30°C and then applying a 100°C solution. The solution is stirred at ~300 rpm for 6~12 hours to obtain a second mixed solution. The zinc ions in the 2-methylimidazole and zinc nitrate aqueous solution, as well as the zinc layer of the growth layer, react to grow a shell. The molar ratio of zinc to 2-methylimidazole in the second mixed solution is (0.01~0.5):(0.1~1.0). The second mixed solution is centrifuged at 8000~12000 rpm for 5~15 minutes to obtain the solid particles separated from the second mixed solution. The solid particles separated from the second mixed solution are then dried at 60~80℃ for 6~12 hours to obtain Si@HEO@ZIF particles.

[0009] Preferably, the process of etching the outer surface of the shell of Si@HEO@ZIF particles with an acidic solution to form secondary channels includes: providing an acidic solution, mixing the acidic solution and Si@HEO@ZIF particles to form a third mixed solution and allowing it to stand for 10-40 seconds to allow the acidic solution to etch secondary channels on the shell, centrifuging the third mixed solution at a speed of 8000-12000 rpm to obtain solid particles separated from the third mixed solution, washing the solid particles separated from the third mixed solution and drying them at 60-80°C for 2-4 hours to obtain the core-shell material, wherein the volume ratio of the acidic solution to the Si@HEO@ZIF particles is (10-20):1.

[0010] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: a core-shell material, prepared by the above-mentioned method for preparing core-shell materials, the core-shell material comprising a core layer, a coating layer and a shell layer formed sequentially from the inside out, and a growth layer disposed between the coating layer and the shell layer for connecting the coating layer and the shell layer, the core layer and the coating layer being connected by ionic bonds; wherein, the core layer in the core-shell material is silicon, the coating layer is a high-entropy oxide, the shell layer is ZIF-8, and secondary channels are distributed on the shell layer.

[0011] Preferably, the diameter of the core layer is 80-200 nm, the thickness of the coating layer is 1-2 nm, the thickness of the growth layer is 2-3 nm, the thickness of the shell layer is 15-20 nm, the depth of the secondary channel is 5-10 nm, and the diameter of the secondary channel is 3-15 nm.

[0012] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: a negative electrode material, comprising a current collector stacked in layers and the above-mentioned core-shell material.

[0013] To solve the above-mentioned technical problems, the present invention provides another technical solution as follows: a battery, the battery comprising a positive electrode material, an electrolyte and the above-mentioned negative electrode material.

[0014] Compared with the prior art, the core-shell material, preparation method, negative electrode material, and battery provided by the present invention have the following beneficial effects:

[0015] 1. An embodiment of the present invention provides a method for preparing a core-shell material, the method comprising: providing metal salt raw materials of aluminum, iron, cobalt, nickel, zinc and lanthanum, pretreating the metal salt raw materials into high-entropy metal oxides; providing silicon particles as a core layer, vaporizing the high-entropy metal oxides in a micro-oxygen environment and depositing them on the surface of the core layer to form a coating layer on the surface of the core layer to obtain Si@HEO particles; depositing zinc in at least a portion of the outer surface of the coating layer to form a growth layer on the outer surface of the coating layer; providing an aqueous solution of zinc nitrate, an aqueous solution of 2-methylimidazole and a Si@HEO solvent, dispersing the Si@HEO particles forming the growth layer in the Si@HEO solvent, adding the aqueous solution of zinc nitrate and the aqueous solution of 2-methylimidazole, growing a shell layer on the growth layer to obtain Si@HEO@ZIF particles; providing an acidic solution, mixing the acidic solution and the Si@HEO@ZIF particles, wherein the acidic solution etches the outer surface of the shell layer of the Si@HEO@ZIF particles to form secondary channels, and performing separation processing to obtain the core-shell material. The core-shell material preparation method provided in this embodiment produces a core-shell material with strong bonding between layers and a functional gradient distribution. The core layer of the core-shell material, prepared layer by layer, provides high capacity; the high-entropy oxide, as a coating layer, provides rigid support and can bear the principal stress dispersion; and ZIF-8, as the shell layer, provides flexible adjustment capability, eliminates residual deformation, and promotes lithium-ion transport. The synergistic effect of the multi-layer structure within the core-shell structure solves the problems of low stress dispersion efficiency, low ion transport, and poor volume expansion rate in existing core-shell materials. The core-shell material prepared based on the above-mentioned core-shell material preparation method of this invention can possess high stress dispersion efficiency, high ion transport, and good volume expansion rate, and the high-entropy oxide inside the core-shell material has stable connectivity with other functional layers.

[0016] 2. The pretreatment of metal salt raw materials into high-entropy metal oxides as defined in this invention includes: providing deionized water and an alcohol solution; mixing the deionized water and alcohol solvent to form a metal salt solvent; providing metal salt raw materials of aluminum, iron, cobalt, nickel, zinc, and lanthanum; dissolving the metal salt precursors of iron, cobalt, nickel, zinc, and lanthanum in the metal salt solvent to form a gel; adding the aluminum metal salt raw material when the gel begins to form to obtain a gel product; and subjecting the gel product to drying and calcination to obtain high-entropy oxides. This embodiment achieves high fusion and uniform dispersion of multiple elements by controlling the order of metal salt addition and strict heat treatment parameters.

[0017] 3. The method for obtaining high-entropy oxides by drying and calcining the gel product as defined in this invention specifically includes the following steps: The gel product is heated from room temperature to 80-120°C at a heating rate of 1-5°C / min, held at that temperature for 6-12 hours, and then cooled to room temperature to complete the drying process; after drying, the product is heated from room temperature to 500-700°C at a heating rate of 2-5°C / min, held at that temperature for 2-4 hours, and then cooled to room temperature to complete the calcination process. In this embodiment, through the synergistic effect of multiple metal ions and the control of temperature during drying and calcination, high-entropy oxides with mechanical buffering capacity can be prepared.

[0018] 4. The molar ratio of aluminum, iron, cobalt, nickel, zinc, and lanthanum in the high-entropy oxide defined in this invention is aluminum:iron:cobalt:nickel:zinc:lanthanum = (0.08~0.16):(0.20~0.30):(0.15~0.25):(0.20~0.28):(0.08~0.15):(0.05~0.12); the particle size of the high-entropy metal oxide is 20~50 nm, and the particle size distribution of the high-entropy metal oxide is less than 0.3. This embodiment, by limiting the molar ratio of each metal element and controlling the powder particle size and its distribution, ensures that a continuous, dense, and uniformly thick coating layer can be formed in subsequent processes.

[0019] 5. The method of growing a shell layer on a growth layer as defined in this invention includes: dispersing Si@HEO particles of a deposited zinc layer in a Si@HEO solvent to obtain a first mixed solution, wherein the volume ratio of Si@HEO particles to Si@HEO solvent in the mixed solution is 1:(10-20), and the Si@HEO solvent is a mixture of alcohol and ionic liquid, wherein the volume percentage of the ionic liquid is 5-30%; adding an aqueous solution of zinc nitrate and an aqueous solution of 2-methylimidazole to the first mixed solution, heating from room temperature to 30°C and then applying a 100°C solution. The solution is stirred at approximately 300 rpm for 6–12 hours to obtain a second mixed solution. Zinc ions from the 2-methylimidazole and zinc nitrate aqueous solution, along with the zinc layer of the growth layer, react to grow a shell. The molar ratio of zinc to 2-methylimidazole in the second mixed solution is (0.01–0.5):(0.1–1.0). The second mixed solution is centrifuged at 8000–12000 rpm for 5–15 minutes to obtain solid particles separated from the second mixed solution. These solid particles are then dried at 60–80 °C for 6–12 hours to obtain Si@HEO@ZIF particles. Zinc ions in the zinc nitrate aqueous solution and the organic ligand 2-methylimidazole in the 2-methylimidazole aqueous solution exhibit excellent reactivity affinity with the zinc layer, enabling the epitaxial growth of ZIF-8. Compared to physical adsorption or random nucleation without specific anchoring points, this method achieves a strong chemical bond between a high-entropy oxide as the coating layer and ZIF-8 as the shell, significantly enhancing the interlayer interface stability.

[0020] 6. The method for etching the outer surface of the shell of Si@HEO@ZIF particles using an acidic solution to form secondary channels, as defined in this invention, comprises: providing an acidic solution; mixing the acidic solution and Si@HEO@ZIF particles to form a third mixed solution and allowing it to stand for 10-40 seconds to allow the acidic solution to etch secondary channels on the shell; centrifuging the third mixed solution at 8000-12000 rpm to obtain solid particles separated from the third mixed solution; washing the solid particles separated from the third mixed solution and drying them at 60-80°C for 2-4 hours to obtain the core-shell material, wherein the volume ratio of the acidic solution to the Si@HEO@ZIF particles is (10-20):1. In this embodiment, the secondary channels are pore structures formed by etching the shell using an acidic solution etching process, forming a multi-level pore system with the inherent micropores of the shell itself. The multi-level pore structure provides additional buffer space for the volume expansion of the core layer while maintaining the overall mechanical strength of the shell.

[0021] 7. This embodiment of the invention also provides a core-shell material, prepared by the above-described method for preparing core-shell materials. The core-shell material includes a core layer, a coating layer, and a shell layer formed sequentially from the inside out, and a growth layer disposed between the coating layer and the shell layer to connect them. The core layer and the coating layer are connected by ionic bonds. The core layer in the core-shell material is silicon, the coating layer is a high-entropy oxide, and the shell layer is ZIF-8, with secondary channels distributed on the shell layer. The core-shell material provided in this embodiment achieves synergistic stress dispersion and ion conduction through the high-entropy oxide, providing a dynamic buffer space for the pore system on the shell layer. It organically combines the high-capacity characteristics of the core layer with structural stability, and through precise matching of the functions of each layer, significantly improves the cycle life and rate performance of lithium batteries.

[0022] 8. This invention also provides a negative electrode material, comprising a current collector stacked in layers and the aforementioned core-shell material. The current collector, as a carrier of electron conduction, directly affects the overall conductivity and cycle stability of the electrode due to the quality of its interfacial contact with the core-shell material; while the nanostructure characteristics of the core-shell material endow the electrode with high capacity and excellent volume expansion control, solving the problem of poor stability faced by traditional silicon-based negative electrodes at the electrode level.

[0023] 9. This invention also provides a battery, comprising a positive electrode material, an electrolyte, and the aforementioned negative electrode material. The secondary pore structure of the core-shell material provides a permeation channel for the electrolyte, allowing lithium ions to rapidly diffuse to the core surface; simultaneously, the chemical stability of the shell reduces the probability of electrolyte decomposition, while the high-entropy characteristics of the coating layer suppress electrolyte reduction reactions by regulating the interfacial electric field distribution. This battery combines the nanoscale characteristics of the core-shell material with the functional requirements of a macroscopic battery system, solving the technical problems of short cycle life and poor rate performance in traditional silicon-based batteries through electrochemical matching and interfacial regulation among components. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic flowchart of a method for preparing a core-shell material according to the first embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of the structure of silicon particles in the first embodiment of the present invention.

[0027] Figure 3 This is a schematic diagram of the structure of Si@HEO particles in the first embodiment of the present invention.

[0028] Figure 4 This is a schematic diagram of the structure of Si@HEO@ZIF particles in the first embodiment of the present invention.

[0029] Figure 5 This is a schematic diagram of the core-shell material in the first embodiment of the present invention.

[0030] Figure 6 This is a schematic diagram of the core-shell material in the second embodiment of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] In the embodiments provided by this invention, it should be understood that "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean determining B solely based on A; B can also be determined based on A and / or other information.

[0033] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of the invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Those skilled in the art should also recognize that the embodiments described in the specification are optional embodiments, and the actions and modules involved are not necessarily essential to the invention.

[0034] In various embodiments of the present invention, it should be understood that the sequence number of each process does not necessarily imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process defined by the present invention.

[0035] The flowcharts and block diagrams in the accompanying drawings illustrate methods and possible architectures, functions, and operations according to various embodiments of this application. In this regard, each block in the flowchart or block diagram may represent part of a step. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, or they may sometimes be executed in reverse order, depending on the functions involved.

[0036] Single or few metal oxides, such as alumina or titanium oxide, are insufficient to effectively mitigate the significant volume changes in silicon during lithium insertion / extraction when used as a coating layer for silicon anodes due to their limited mechanical properties and compressive stress dispersion capabilities. This leads to electrode material pulverization, rapid capacity decay, and shortened cycle life. High-entropy oxides, as novel materials composed of multiple metal elements, possess entropy stabilization effects and structural tunability, showing potential advantages in energy storage. However, in existing technologies, composite structures of high-entropy oxides with other functional layers, such as high-entropy oxides with organic or carbon materials, often suffer from interlayer delamination problems due to weak interfacial bonding and a lack of effective chemical anchoring points. Therefore, there is an urgent need for a method to prepare core-shell materials that can achieve stable bonding between high-entropy oxides and functional layers, and possess efficient stress dispersion and ion transport capabilities.

[0037] Please see Figure 1 To address the aforementioned technical problems, the first embodiment of the present invention provides a method for preparing a core-shell material, the method comprising:

[0038] S1. Provide metal salt raw materials of aluminum, iron, cobalt, nickel, zinc and lanthanum, and pre-treat the metal salt raw materials into high-entropy metal oxides;

[0039] S2. Provide silicon particles as the core layer, and deposit high-entropy metal oxides on the surface of the core layer after vaporization in a micro-oxygen environment to form a coating layer on the surface of the core layer to obtain Si@HEO particles.

[0040] S3. Deposit zinc in at least a portion of the outer surface of the coating layer to form a growth layer on the outer surface of the coating layer;

[0041] S4. Provide an aqueous solution of zinc nitrate, an aqueous solution of 2-methylimidazole, and a Si@HEO solvent. Disperse the Si@HEO particles forming the growth layer in the Si@HEO solvent, then add the aqueous solution of zinc nitrate and the aqueous solution of 2-methylimidazole to grow a shell layer on the growth layer. The shell layer material is ZIF-8 to obtain Si@HEO@ZIF particles; and

[0042] S5. Provide an acidic solution and mix it with Si@HEO@ZIF particles. The acidic solution etches the outer surface of the shell of the Si@HEO@ZIF particles to form secondary channels. The core-shell material is then obtained through separation.

[0043] Understandably, this embodiment constructs a core-shell structure with strong interfacial bonding and synergistic buffering function by using silicon as the core layer, high-entropy oxide as the coating layer, and ZIF-8 as the shell layer, thereby solving the problems of low stress dispersion efficiency, low ion transport, and poor volume expansion rate of existing core-shell materials.

[0044] Specifically, in step S1 of this embodiment, the composition of the high-entropy oxide is first designed using metal salts of six metallic elements. The selected six metallic elements—aluminum, iron, cobalt, nickel, zinc, and lanthanum—are not arbitrary combinations, but rather play a synergistic role in the final oxide through their ionic properties. Aluminum ions primarily contribute to enhancing the structural elasticity and mechanical strength of the coating layer; iron, cobalt, and nickel ions jointly construct multiple redox active centers, improving the electrochemical activity of the material; the key role of zinc ions is to provide an indispensable chemical anchoring point for the growth of the metal-organic framework, i.e., ZIF-8, as the shell layer in subsequent steps; the introduction of lanthanum ions helps increase the oxygen vacancy concentration in the oxide, thereby enhancing the lithium-ion conductivity. This introduction of multiple metals results in a high-entropy oxide with superior structural stability compared to oxides with single or few components.

[0045] Furthermore, please combine Figure 1 and Figure 2In step S2, high-entropy oxide is deposited onto the surface of the silicon particles. Specifically, chemical vapor deposition (CVD) can be used to construct a high-entropy oxide coating layer on the silicon particle surface. The deposition occurs in a "micro-oxygen environment." This environment ensures that metal elements can be deposited in the form of oxides. Simultaneously, due to the limited oxygen content and rapid deposition rate, the long-range ordered arrangement of atoms in the deposited material is effectively suppressed, thus promoting the formation of an amorphous structure. However, the trace amount of oxygen also provides a weak thermodynamic driving force for local areas, allowing regions containing iron, cobalt, and nickel to crystallize locally, ultimately embedding a nano-spinel structure within the amorphous structure, forming an amorphous / spinel dual-phase composite structure. This composite structure combines the good toughness and uniformity of the amorphous phase with the high strength and stability of the nanocrystalline phase. As the first barrier directly coating the core layer surface, the coating layer can efficiently disperse and absorb the radial compressive stress generated during lithium insertion / extraction in silicon through its own microstructural deformation and phase boundary sliding, effectively preventing early cracking of the coating layer due to stress concentration, and providing mechanical buffering capacity for the entire core-shell structure.

[0046] Furthermore, please combine... Figure 3 and Figure 4 After forming a stable high-entropy oxide layer, a zinc layer is deposited on the surface of the coating layer in step S3. Specifically, an extremely thin zinc layer can be introduced onto the outer surface of the coating layer through electrochemical deposition. The zinc layer serves as an anchor point for chemical growth; therefore, the area containing the zinc layer is also called the growth layer. The growth layer can completely cover the coating layer or only partially cover a portion of the coating layer's surface. If the growth layer does not completely cover the coating layer, uncovered areas will remain on the coating layer's surface. It should be noted that the shell layer, as the outermost layer, must completely cover the surface to effectively prevent the electrolyte from directly contacting the internal materials and forming a stable solid electrolyte intermediate phase. Its overall mechanical properties require a continuous network to bear and transfer stress. Its regular channels need to form a continuous lithium-ion transport network. If the shell layer does not cover the internal growth layer and coating layer, weaknesses will remain in the uncovered areas. During cycling, silicon expansion preferentially penetrates these weak points, leading to coating layer rupture, electrolyte intrusion, and repeated growth of the solid electrolyte interphase, ultimately resulting in rapid capacity decay. The growth layer can be designed as an "incomplete" coating. The purpose of the electrochemically deposited Zn layer is not to form a dense metal isolation layer, but rather for "interface activation." The morphology is "island-like" rather than "film-like," with the growth layer consisting of discontinuous nano-islands or nanoclusters that do not need to completely cover the coating layer. Between adjacent growth layers, a large amount of the coating layer surface is exposed. The exposed coating layer regions themselves are ion conductors, providing additional and more direct transport paths for lithium ions, avoiding the risk of lithium ions being completely blocked by a dense layer of metallic zinc.

[0047] Specifically, zinc in the growth layer, acting as a precursor of the same metal element, exhibits excellent affinity for zinc ions in the zinc nitrate aqueous solution and the organic ligand 2-methylimidazole in the 2-methylimidazole aqueous solution. Under the induction of zinc, zinc ions and 2-methylimidazole gradually form ZIF-8 crystals. These ZIF-8 crystals undergo epitaxial growth within the growth layer, gradually forming a shell. Here, "ZIF" refers to a zeolitic imidazolate framework (ZIF), and "-8" indicates the designation of a member of the ZIF group. Zeolitic imidazolate frameworks are three-dimensional network crystal materials with regular nanopores, formed by the self-assembly of metal ions and organic molecules through coordination bonds. In this embodiment, ZIF-8 is a metal-organic framework material with zinc ions as the metal center, 2-methylimidazole as the organic linker, and possessing a zeolite-like topology, regular micropores, and high stability. In this embodiment, the connection method of using a zinc layer as a growth layer to connect the coating layer and the shell layer achieves a strong chemical bond between the high-entropy oxide as the coating layer and ZIF-8 as the shell layer, compared with physical adsorption or random nucleation without specific anchoring points. This greatly enhances the stability of the interlayer interface and avoids the risk of interlayer delamination when the core and shell materials are applied to the battery field under the mechanical stress of battery cycling.

[0048] Furthermore, please combine Figure 4 and Figure 5 The shell is primarily made of ZIF-8 material. ZIF-8 itself possesses regular micropores (not shown in the attached diagram). These micropores not only provide pathways for the rapid transport of lithium ions, but their pore structure can also accommodate part of the volume expansion of the core layer. Finally, the shell is etched using an acidic solution to create larger secondary channels on its surface. These secondary channels act as pre-reserved expansion buffers, further absorbing and releasing the volume change stress of the core layer during cycling. The secondary channels, together with the micropores of the shell and the mechanical buffering effect of the coating layer, form a multi-level, synergistic anti-expansion effect, resulting in superior anti-expansion performance in the final core-shell material.

[0049] Understandably, the core-shell material preparation method provided in this embodiment produces a core-shell material with strong bonding between layers and a functional gradient distribution. Through layer-by-layer preparation, the core-shell material utilizes silicon as the core layer to provide high capacity, high-entropy oxide as the coating layer to provide rigid support and bear principal stress dispersion, and ZIF-8 as the shell layer to provide flexible adjustment capabilities, eliminate residual deformation, and promote ion transport. The synergistic effect of the multi-layer structure jointly solves the problems of low stress dispersion efficiency, low ion transport, and poor volume expansion rate in existing core-shell materials.

[0050] Furthermore, please combine Figure 2 and Figure 3 In step S1 above, pretreating the metal salt raw material into a high-entropy metal oxide includes:

[0051] The solution provides deionized water and an alcohol solution, and the deionized water and the alcohol solvent are mixed to form a metal salt solvent, wherein the alcohol solvent can be methanol or ethanol, and the deionized water and the alcohol solvent are mixed in a volume ratio of 2:1 to form the metal salt solvent.

[0052] It provides metal salts of aluminum, iron, cobalt, nickel, zinc, and lanthanum.

[0053] Metal salt precursors of iron, cobalt, nickel, zinc and lanthanum are dissolved in metal salt solvents to form gels;

[0054] Aluminum metal salt raw materials are added when the gel begins to form to obtain a gel product;

[0055] The gel product was dried and calcined to obtain high-entropy oxides.

[0056] Understandably, traditional co-precipitation or simple mixing methods struggle to achieve uniform elemental distribution and the construction of specific functional surfaces. This embodiment employs a sol-gel process to precisely control the participation order and spatial distribution of multiple metal elements during gel network formation, thereby preparing high-entropy oxide powder. Specifically, five metal salt precursors—iron, cobalt, nickel, zinc, and lanthanum—are first dissolved together. During the dissolution process, hydrolysis and condensation reactions primarily occur: the hydrolysis reaction mainly involves the metal cations in the added metal salt precursors reacting with the solvent, combining with water molecules and hydroxyl groups to form hydroxylated products or metal hydroxides, resulting in the metal ions being surrounded by hydroxyl groups; the condensation reaction mainly involves the products obtained from the hydrolysis reaction connecting with other unhydrolyzed metal ions through "oxygen bridges" or "hydroxyl bridges," releasing water molecules or protons. The continuous occurrence of numerous hydrolysis and condensation reactions causes the small molecular units in the solution to gradually connect into chains and rings, eventually expanding into a three-dimensional network structure spanning the entire solution volume. This network encapsulates the solvent, losing its fluidity and thus forming a gel.

[0057] Specifically, during the dissolution process, five metal ions gradually form a gel. In the early stages of gel formation, iron, cobalt, nickel, zinc, and lanthanum ions interact to construct an initial gel network framework. An aluminum metal salt precursor solution is added only during the formation of this network framework. Aluminum ions, with their high charge density and specific coordination ability, further coordinate and cross-link with hydroxyl groups, water molecules, and other metal ions in the initially formed pentagonal gel network, altering the local structure of the original gel network and enhancing its overall stability. The zinc element in the final gel product, due to its migration tendency during heat treatment, tends to accumulate on the surface of the high-entropy oxide, resulting in a "zinc-rich surface" state. This zinc-rich surface structure eliminates the need for additional complex surface treatment of the high-entropy oxide, allowing for direct electrochemical deposition of the zinc layer. In addition, the zinc atoms on the surface of the high-entropy oxide have excellent affinity with the zinc atoms electrochemically deposited from the solution, ensuring that the zinc can adhere firmly during deposition, thus creating excellent anchoring points for the epitaxial growth of the confined region of the shell.

[0058] It should be noted that if all metal precursors are added simultaneously, it is difficult to spontaneously form a surface state that is conducive to subsequent interface functionalization. It should be understood that this embodiment achieves a high degree of fusion and uniform dispersion of multiple elements by controlling the order of metal salt addition and strict heat treatment parameters.

[0059] Specifically, obtaining high-entropy oxides by drying and calcining the gel product includes the following steps:

[0060] The gel product is heated from room temperature to 80-120°C at a heating rate of 1-5°C / min, held at that temperature for 6-12 hours, and then cooled to room temperature to complete the drying process.

[0061] After drying, the temperature is increased from room temperature to 500-700℃ at a rate of 2-5℃ / min, held for 2-4 hours, and then cooled to room temperature to complete the calcination process.

[0062] Specifically, during the drying process of the gel product, a slow heating rate of 1-5°C / min is used to gradually raise the temperature to a lower range of 80-120°C. The gel product contains a large amount of solvent water and organic components. If the temperature rises too quickly, the solvent will vaporize violently, generating enormous vapor pressure inside the gel product. This can damage the internal network structure, leading to macroscopic cracks or even material fragmentation. A slow heating rate allows the solvent molecules to evaporate steadily and gradually, releasing internal stress slowly and thus maximizing the integrity and continuity of the internal network structure of the gel product. The subsequent prolonged low-temperature holding ensures the complete removal of residual solvent, facilitating subsequent high-temperature calcination. Skipping the drying step and directly subjecting the material to rapid high-temperature treatment can easily result in a porous, fragile, or even fractured structure, failing to meet the requirements of density and continuity as a coating layer.

[0063] During the calcination stage, the temperature is raised from room temperature to 500-700℃ at a controlled heating rate of 2-5℃ / min. The purpose of calcination is to transform the amorphous gel product into a stable high-entropy oxide. During calcination, the metal ions in the gel product need to migrate, rearrange, and form stable high-entropy oxides. If the temperature rises too quickly, the solvent in the gel product will decompose rapidly, generating a large amount of gas, which will also cause structural damage. Excessive heating will also cause the local reactions to become too violent before the metal ions gain sufficient energy for long-range diffusion and orderly arrangement, which is not conducive to the uniform mixing of multiple metal ions, thus generating a simple binary or ternary oxide mixture instead of a high-entropy oxide.

[0064] It should be understood that in this embodiment, through the synergistic effect of multiple metal ions and the control of temperature during drying and calcination, a two-phase composite structure with an amorphous structure embedded with a nano-spinel structure is ultimately formed. The amorphous phase has good toughness and isotropy, and can uniformly disperse stress; while the dispersed nano-spinel phase provides high strength and hardness, enhancing the rigid support capacity of the coating layer. When the coating layer covers the surface of the core layer, it can more effectively buffer the stress generated by the huge volume expansion and contraction of silicon particles, thereby significantly improving the cycle stability of the anode material.

[0065] Specifically, high-entropy oxides are (Al 0.12 Fe 0.25 Co 0.2 Ni 0.23 Zn 0.1 La0. 08 O xWhere x represents the amount of oxygen, and the value of x is uncertain because a large number of oxygen vacancies are generated during the preparation process. In some other specific embodiments, the molar ratio of aluminum, iron, cobalt, nickel, zinc and lanthanum in the high-entropy oxide is aluminum:iron:cobalt:nickel:zinc:lanthanum = (0.08~0.16):(0.20~0.30):(0.15~0.25):(0.20~0.28):(0.08~0.15):(0.05~0.12); the particle size of the high-entropy metal oxide is 20~50nm, and the particle size distribution of the high-entropy metal oxide is less than 0.3.

[0066] Understandably, this embodiment ensures that a continuous, dense and uniform coating layer can be formed in subsequent processes by limiting the molar ratio of each metal element and controlling the particle size and distribution of the powder.

[0067] Preferably, the high-entropy oxide is (Al) 0.12 Fe 0.25 Co 0.2 Ni 0.23 Zn 0.1 La0. 08 O x Aluminum primarily functions to provide structural elasticity and enhance mechanical strength. It ensures sufficient cross-linking points within the oxide network to buffer stress; too low a proportion results in insufficient buffering, while too high a proportion may make the material overly rigid and brittle. Iron, cobalt, and nickel together constitute the redox active centers of the material. Their different ionic valence states and electrochemical windows provide multiple and continuous charge transfer pathways, improving the material's electrochemical performance and reversible capacity. Zinc is sufficient to form an effective zinc atom enrichment region on the material surface, providing ample chemical anchoring points for subsequent electrochemical deposition of the zinc layer and guiding ZIF-8 epitaxial growth to form a shell. It also avoids the potential for phase separation or adverse effects on overall structural stability that might occur with excessively high proportions. Lanthanum, with its large ionic radius and unique electronic structure, significantly increases the oxygen vacancy concentration in the material. These oxygen vacancies act as rapid channels for lithium ion migration, greatly enhancing the material's ionic conductivity.

[0068] Furthermore, the particle size of the high-entropy metal oxides is controlled within the range of 20 to 50 nanometers, with a particle size distribution of less than 0.3. Here, 0.3 refers to the polydispersity index, a parameter that measures the width of the particle size distribution in a particle system, reflecting the uniformity of particle size. The nanoscale particle size of the high-entropy metal oxides ensures that individual particles have high specific surface energy and good surface curvature, allowing them to spread and adhere tightly to the core layer surface during chemical vapor deposition. When the particle size distribution of the high-entropy metal oxides is less than 0.3, the powder particles are relatively uniform in size, avoiding problems such as uneven coating thickness, weak points, or defects caused by the coexistence of large and small particles during the coating process. This results in a continuous and dense high-entropy oxide coating layer. The coating layer effectively provides mechanical buffering without introducing excessive additional volume or impedance.

[0069] Furthermore, please combine Figure 3 and Figure 4 The process of vaporizing high-entropy metal oxides and depositing them on the surface of the core layer to form a coating layer to obtain Si@HEO particles includes:

[0070] High-entropy metal oxides are vaporized into a gas source using chemical vapor deposition in a micro-oxygen environment, which can refer to an air environment, i.e., an oxygen content of less than 21%.

[0071] Gas source is deposited on the surface of the core layer to form a coating layer, which covers the entire surface of the core layer to obtain Si@HEO particles.

[0072] Understandably, introducing trace amounts of oxygen during the deposition of the coating layer ensures that the metal elements are deposited in oxide form. The controlled oxygen content and rapid deposition rate also suppress the long-range ordered arrangement of the deposits, resulting in an amorphous structure. Simultaneously, localized areas preferentially crystallize due to oxygen partial pressure differences, forming nano-spinel structures, thus constructing an amorphous / spinel dual-phase composite structure. This significantly improves the compressive stress dispersion efficiency of the coating layer, effectively mitigating the volume expansion stress of the core layer during charging and discharging compared to single metal oxides. Secondly, the non-directional nature of chemical vapor deposition ensures uniform deposition of high-entropy metal oxides on the core layer surface. The resulting coating layer possesses coating properties, avoiding the "pinholes" or "exposed areas" that easily occur in traditional coating processes. If the subsequently prepared electrode material is used in a battery, it can effectively prevent the electrolyte from directly eroding the core layer, while also suppressing the pulverization failure of silicon particles during cycling.

[0073] Furthermore, please combine Figure 4 and Figure 5 The growth of a shell on the growth layer includes:

[0074] The Si@HEO particles with the deposited zinc layer were dispersed in a Si@HEO solvent to obtain a first mixed solution. The volume ratio of Si@HEO particles to Si@HEO solvent in the mixed solution was 1:(10-20). The Si@HEO solvent was a mixture of alcohol and ionic liquid, wherein the volume percentage of the ionic liquid was 5-30%.

[0075] Add zinc nitrate aqueous solution and 2-methylimidazole aqueous solution to the first mixed solution, heat from room temperature to 30°C and stir at 100~300 rpm for 6~12 hours to obtain the second mixed solution. The zinc ions in the 2-methylimidazole and zinc nitrate aqueous solution, as well as the zinc layer of the growth layer, react to grow a shell. The molar ratio of zinc to 2-methylimidazole in the second mixed solution is (0.01~0.5):(0.1~1.0).

[0076] The second mixed solution is centrifuged at 8000~12000 rpm for 5~15 minutes to obtain the solid particles separated from the second mixed solution. The solid particles separated from the second mixed solution are then dried at 60~80℃ for 6~12 hours to obtain Si@HEO@ZIF particles.

[0077] Understandably, zinc ions in zinc nitrate aqueous solution and the organic ligand 2-methylimidazole in 2-methylimidazole aqueous solution have excellent reaction affinity with the zinc layer, which serves as the growth layer, enabling the epitaxial growth of ZIF-8. ZIF-8 is a metal-organic framework material with a regular microporous structure and high specific surface area. The shell layer is formed by confining the growth of ZIF-8 on the growth layer. A volume ratio of alcohol to ionic liquid of 1:(10-20), with the ionic liquid comprising 5-30%, is key to achieving uniform growth of ZIF-8. The alcohol solvent, as the main dispersion medium, reduces the supersaturation of the precursor, preventing the random generation of ZIF-8 nuclei in the solution. The ionic liquid can be a [BMIM][BF4] ionic solution. The introduction of the ionic solution adsorbs the zinc layer on the surface of Si@HEO particles through electrostatic interaction, providing a directional template for the epitaxial growth of ZIF-8. This confinement of ZIF-8 growth within the growth layer effectively solves the problems of shell agglomeration and uneven thickness that easily occur in traditional liquid phase deposition, ensuring a tight bond between the shell and the core layer. Furthermore, by controlling the volume percentage of the ionic liquid within the range of 5-30%, the crystallization kinetics of ZIF-8 can be precisely controlled. When the ionic liquid percentage is low, such as 5-15% by volume, the system viscosity is low, which is conducive to promoting the radial growth of ZIF-8 crystals and forming a thicker shell. When the volume percentage of the ionic liquid is increased to 15-30%, the increased viscosity inhibits excessive crystal growth and instead optimizes the orderliness of the microporous structure. By adjusting the solvent ratio, the shell can provide sufficient mechanical support while retaining nanopores for ion transport, achieving synergistic optimization of mechanical and electrochemical properties.

[0078] It should be understood that the growth of ZIF-8 on silicon-based composite surfaces in existing technologies often suffers from interface delamination problems, i.e., the shell and core layers peel off during charge-discharge cycles due to expansion differences. This embodiment utilizes the synergistic effect of alcohols and ionic liquids to construct a shell layer on the surface of Si@HEO particles: the shell layer can effectively transfer stress and absorb expansion energy through contraction via pores. This significantly improves the structural integrity of the core-shell material and solves the problem of easy delamination between traditional ZIF-8 layers and other structural layers. Furthermore, the ionic liquid component in the mixed solvent can form weak coordination with the metal ions in the ZIF-8 framework, preferentially removing them in subsequent acid etching steps to form secondary channels of 5-10 nm. These channels act as additional "expansion storage space," further mitigating the impact of core layer volume changes on the overall structure. Compared to shell layers prepared with pure alcohol solvents, the mixed solvent system in this embodiment increases the shell's volume expansion capacity by an order of magnitude, providing a structural improvement for battery cycle stability.

[0079] Furthermore, please combine Figure 4 and Figure 5 Etching to form secondary channels includes:

[0080] An acidic solution is provided, and the acidic solution and Si@HEO@ZIF particles are mixed to form a third mixed solution. The mixture is allowed to stand for 10-40 seconds to allow the acidic solution to etch secondary channels on the shell. The third mixed solution is centrifuged at 8000-12000 rpm to obtain solid particles separated from the third mixed solution. The solid particles separated from the third mixed solution are washed and dried at 60-80℃ for 2-4 hours to obtain the core-shell material. The volume ratio of the acidic solution to the Si@HEO@ZIF particles is (10-20):1.

[0081] Understandably, the secondary channels in this embodiment are porous structures formed by etching the shell layer using an acidic solution etching process, forming a hierarchical pore system with the micropores of ZIF-8 itself. The acidic solution selectively dissolves the metal coordination nodes in the ZIF-8 framework, creating 5-10 nm through-holes inside the shell layer. The hierarchical pore structure provides additional buffer space for the volume expansion of the core layer while maintaining the overall mechanical strength of the shell layer.

[0082] Specifically, controlling the volume ratio of acidic solution to particles ensures the uniformity of the etching reaction: excessive acidic solution leads to over-dissolution of the shell, while insufficient ratio fails to form enough channels. By limiting the volume ratio of acidic solution to Si@HEO@ZIF particles, each particle surface is exposed to an appropriate amount of acidic medium, thereby forming uniformly distributed secondary channels on the shell and avoiding structural collapse caused by localized over-etching. Furthermore, the coordination bond breaking reaction between the acidic solution and ZIF-8 requires a certain amount of time to penetrate into the shell. Too short a settling time will result in insufficient channel depth, failing to effectively store volume expansion; too long a settling time will cause excessive damage to the shell structure. In this embodiment, by controlling the settling time, the etching reaction occurs only in specific areas of the shell, forming secondary channels. The outer layer of the shell has a high channel density and large size, while the inner layer retains a dense structure, providing sufficient expansion space while maintaining the shell's barrier capability against the electrolyte. Furthermore, centrifugation rapidly separates solid particles from residual acidic solution using centrifugal force at a specific speed, terminating the etching reaction and preventing over-etching. Additionally, the mechanical stress generated by centrifugation promotes the drainage of residual acid from the pores, reducing the burden of subsequent washing. Compared to traditional filtration methods, centrifugation more effectively preserves the nanoscale pore structure, preventing pore blockage due to filter membrane adsorption. Furthermore, slow drying at a suitable temperature allows for uniform evaporation of moisture within the particles, preventing pore collapse or surface cracking caused by rapid drying. Simultaneously, the micro-positive pressure environment maintained during drying helps maintain the open structure of the secondary pores, ensuring that the secondary pores can continuously provide buffer space for volume expansion during subsequent battery cycles. Understandably, this embodiment constructs secondary pores through acidic solution etching, controls etching uniformity by limiting the volume ratio of acidic solution to Si@HEO@ZIF particles, adjusts pore size by settling time, and maintains pore stability through centrifugation and drying processes.

[0083] Please see Figure 6 The second embodiment of the present invention also provides a core-shell material, which is prepared by a core-shell material preparation method. The core-shell material includes a core layer, a coating layer and a shell layer formed sequentially from the inside to the outside, and a growth layer disposed between the coating layer and the shell layer for connecting the coating layer and the shell layer. The core layer and the coating layer are connected by ionic bonds. In this core-shell material, the core layer is silicon and the coating layer is a high-entropy oxide (Al₂O₃). 12 Fe 0.25 Co 0.2 Ni0. 23 Zn 0.1 La0. 08 Ox, with a ZIF-8 shell and secondary channels distributed on the shell.

[0084] Understandably, the core-shell material in this embodiment achieves optimized mechanical and electrochemical performance through the combined action of the core layer, coating layer, zinc layer, and shell layer. The core layer uses silicon material with high theoretical capacity to provide energy density for the lithium battery; the coating layer uses a multi-element high-entropy oxide, tightly bonded to the core layer via ionic bonds; the zinc layer acts as an interface bridge to promote the epitaxial growth of the shell layer; the shell layer and its secondary channels construct a flexible buffer system, with each layer complementing each other to form a synergistic effect. Specifically, the core layer and coating layer are connected by ionic bonds, which have strong bond energy and can effectively suppress interface delamination of the core layer during volume expansion. Compared to the van der Waals force bonding of traditional physical coatings, ionic bonding allows the coating layer to more tightly adhere to the core layer surface, maintaining structural integrity during charge-discharge cycles and preventing electrolyte erosion and loss of active materials due to interface cracking. This chemical bonding method significantly improves the cycle durability of the core-shell material. Furthermore, the multi-element metal composition design of the high-entropy oxide coating layer can synergistically enhance performance. Aluminum ions enhance the structural elastic modulus, alleviating stress caused by core expansion; iron, cobalt, and nickel ions construct multiple redox active sites, promoting rapid lithium-ion transport; zinc ions provide chemical anchoring for subsequent zinc layer deposition; and lanthanum ions optimize ion diffusion channels by adjusting oxygen vacancy concentration. This multi-element synergistic effect endows the coating layer with both excellent mechanical support and ion conductivity, solving the problems of limited mechanical properties, low compressive stress dispersion efficiency, and ineffective mitigation of volume expansion in silicon anodes caused by traditional single-metal oxides. The microporous structure of the shell itself provides a rapid channel for lithium-ion transport, while secondary channels act as buffer spaces for volume expansion. When the core layer undergoes volume changes, the secondary channels absorb expansion stress through contraction, while the shell's flexibility further buffers stress impact through minute deformations of the crystal structure. This hierarchical channel design allows the shell to provide effective buffering without significantly increasing ion transport resistance. The core-shell material provided in this embodiment achieves stress dispersion and ion conduction synergistically through high-entropy oxides, providing a dynamic buffer space for the porous system on the shell layer, organically combining the high capacity characteristics of the core layer with structural stability, and significantly improving the cycle life and rate performance of lithium batteries through precise matching of functions at each level.

[0085] Specifically, the core layer diameter ranges from 80 to 200 nm. By controlling the core layer size within this specific range, the absolute volume expansion per cycle can be reduced while ensuring high specific capacity. A smaller core layer diameter reduces the absolute value of expansion stress, making it easier for the coating and shell layers to absorb expansion energy through elastic deformation, thus preventing structural fracture. Simultaneously, controlling the uniformity of the core layer diameter ensures consistent material performance at the electrode level, reducing localized stress concentration and capacity decay caused by differences in particle size. The core layer diameter can also range from 80 to 200 nm, 90 to 150 nm, or 80 to 180 nm.

[0086] Specifically, the coating layer thickness is 1-2 nm. The coating layer thickness must balance mechanical strength and volumetric efficiency: too thick a layer will reduce the overall volumetric energy density of the material, while too thin a layer will not provide effective mechanical support. This embodiment precisely controls the coating layer thickness to form a continuous and dense protective film that prevents electrolyte erosion, while also dispersing expansion stress throughout the coating layer through the synergistic effect of the amorphous / spinel dual-phase composite structure, avoiding cracking caused by localized stress concentration. This ultra-thin design also reduces the length of the ion transport path, increasing the diffusion rate of lithium ions in the coating layer. The coating layer thickness can also be 1.5-2 nm, 1-1.2 nm, or 1.3-2 nm.

[0087] Specifically, the thickness of the growth layer is 2-3 nm. As a transition layer between the coating layer and the shell layer, the zinc layer needs to have sufficient thickness to ensure the uniform formation of ZIF-8 nuclei and the epitaxial growth of the shell layer, while avoiding interfacial stress caused by excessive thickness. A zinc layer thickness within a specific range can provide uniform nucleation sites for the epitaxial growth of ZIF-8, ensuring a tight bond between the shell and core layers and reducing interfacial impedance. The thickness of the growth layer can also be 2-3 nm, 2-3 nm, or 2-3 nm.

[0088] Specifically, the shell thickness is 15-20 nm. The shell needs sufficient thickness to provide mechanical strength and expansion buffer space, while avoiding excessive thickness that would increase ion transport resistance. By controlling the shell thickness within a specific range, a continuous ion transport channel can be constructed within the shell, ensuring that lithium ions can rapidly diffuse to the core layer. Simultaneously, the shell at this thickness has a suitable elastic modulus, allowing it to absorb some expansion energy through its own deformation, reducing stress transmission to the coating layer. The shell thickness can also be 15-20 nm, 15-20 nm, or 15-20 nm.

[0089] Specifically, the depth of the secondary channels is 5-10 nm, and the diameter is 3-15 nm. The channel depth needs to match the shell thickness to ensure sufficient expansion space without compromising the overall structural integrity of the shell. The channel diameter needs to meet the requirements of lithium-ion transport kinetics to avoid increased ion diffusion resistance due to excessively small pore size. Precise control of the channel size allows the shell to absorb volume expansion through channel contraction during cycling while maintaining an efficient ion transport path, solving the problem of traditional rigid shells' inability to simultaneously achieve "buffering-conduction." The depth of the secondary channels can also be 5-10 nm, 5-10 nm, or 5-10 nm, and the diameter can also be 3-10 nm, 5-8 nm, or 6-15 nm.

[0090] To verify the effectiveness of the core-shell material provided in this embodiment, the following experiment will now be conducted:

[0091] Experimental group:

[0092] Step 1: Using chemical vapor deposition with silane as the gas source, monodisperse silicon particles with a diameter of about 200 nm were grown on a quartz substrate at 500 °C in an Ar / H2 (volume ratio of 9:1) atmosphere. After ultrasonic exfoliation, the particles were washed three times with anhydrous ethanol and vacuum dried at 60 °C for 12 hours to obtain silicon particles.

[0093] Step 2: Weigh out aluminum nitrate, ferric nitrate, cobalt nitrate, nickel nitrate, zinc nitrate, and lanthanum nitrate as solutes in a molar ratio of Al:Fe:Co:Ni:Zn:La = 0.12:0.25:0.2:0.23:0.1:0.08. Mix deionized water and ethanol at a volume ratio of 2:1 to form an ethylene glycol solvent. Add citric acid to the ethylene glycol solvent to form an ethylene glycol-citric acid solvent. Dissolve the solutes in the ethylene glycol-citric acid solvent to form a mixed solution. The solute and ethylene glycol-citric acid solvent were in a molar ratio of 1:1. After the mixed solution was magnetically stirred for 2 hours, it was evaporated into a gel in an 80°C water bath. The gel was then ground into powder and used as a gas source. In an environment with an Ar / H2 volume ratio of 4:1 at 400°C, silicon particles were placed under a gas flow and a trace amount of O2 (O2 / Ar volume ratio of 1:100) was introduced to deposit a 2nm thick layer of high-entropy oxide to form a coating layer, thus obtaining Si@HEO particles.

[0094] Step 3: Prepare a 0.1 mol ZnSO4 electrolyte, using the Si@HEO particle dispersion as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode; deposit at -0.8V (vs Ag / AgCl) for 30 seconds to form a 2-3 nm thick island-shaped zinc layer, wash with deionized water and dry with nitrogen to obtain Si@HEO particles with the deposited island-shaped zinc layer.

[0095] Step 4: Ethanol and ionic liquid [BMIM][BF4] are mixed in a volume ratio of 5:1 to form a mixed solvent, and magnetically stirred for 30 minutes; the Si@HEO particles with zinc deposited layer are dispersed in the mixed solvent of Step 4, 0.08 mol zinc nitrate and 0.32 mol 2-methylimidazole are added, and the mixture is stirred at 100 rpm for 6 hours at 30°C; after centrifugation at 8000 rpm for 5 minutes, the particles are washed 3 times with anhydrous ethanol and vacuum dried at 60°C for 6 hours to obtain Si@HEO@ZIF-8 particles.

[0096] Step 5: Disperse Si@HEO@ZIF-8 particles in 0.1 mol HCl solution, stir in an ice-water bath for 30 seconds, centrifuge at 10,000 rpm for 3 minutes, wash with ice water until neutral, and vacuum dry at 60℃ for 12 hours to obtain the final core-shell material.

[0097] Comparative Group 1: Using chemical vapor deposition with silane as the gas source, monodisperse silicon particles with a diameter of about 200 nm were grown on a quartz substrate at 500 °C in an Ar / H2 atmosphere (volume ratio of 9:1). After ultrasonic exfoliation, the particles were washed three times with anhydrous ethanol and vacuum dried at 60 °C for 12 hours to obtain silicon particles.

[0098] A 15nm carbon layer is formed on the surface of silicon particles using chemical vapor deposition to obtain carbon-coated materials.

[0099] Control group 2: The preparation steps are the same as those of the experimental group, except that the ZIF shell is not prepared.

[0100] Control group 3: The preparation steps are the same as those of the experimental group, except that no coating layer is prepared.

[0101] Control group 4: The preparation steps are the same as those of the experimental group, except that Al2O3 is used as the coating layer.

[0102] Performance testing methods

[0103] Compressive stress dispersion efficiency: The elastic modulus and hardness of the core-shell material of the experimental group and the carbon-coated material of the control group were tested using a nanoindenter with a loading force of 500 μN; the compressive stress distribution was calculated based on finite element simulation to compare the stress dispersion efficiency of the core-shell material of the experimental group and the carbon-coated material of the control group.

[0104] Volume expansion rate: The core-shell material of the experimental group and the carbon-coated material of the control group were used to make CR2032 button batteries. The lithium sheet was used as the counter electrode, and 1 mol LiPF8 / EC:DMC (volume ratio of 1:1) was used as the electrolyte. After 50 cycles at 0.1C, the particle size change was observed by electron microscopy and the volume expansion rate was calculated.

[0105] Li⁺ diffusion coefficient: The core-shell material of the experimental group and the carbon-coated material of the control group were tested by EIS using an electrochemical workstation. The chemical diffusion coefficient of lithium ions was calculated based on the Warburg impedance fitting in the low-frequency region. Warburg impedance is an impedance form that describes diffusion control in electrochemistry. Warburg impedance can describe the resistive component of electron transfer in electrolyte solution under diffusion control.

[0106] Cycling performance: Half-cells were made from the core-shell materials of the experimental group and the carbon-coated materials of the control group. The first charge-discharge curves were tested at 0.1C rate, and the first coulombic efficiency was calculated. The capacity retention rate was recorded after 200 cycles at 0.5C rate.

[0107] Experimental results:

[0108] Table 1, Performance Indicator Table

[0109]

[0110] As shown in Table 1, the core-shell material in the experimental group solved the problems of weak volume expansion resistance, poor cycle stability, and low ion transport efficiency of silicon-based anode materials. This core-shell structure achieves an integrated improvement in both mechanical and electrochemical performance while maintaining the high capacity characteristics of silicon.

[0111] The third embodiment of the present invention also provides a negative electrode material, comprising a current collector stacked in layers and the aforementioned core-shell material. In this embodiment, the current collector acts as a carrier for electron conduction, and the quality of its interfacial contact with the core-shell material directly affects the overall conductivity and cycle stability of the electrode; while the nanostructure characteristics of the core-shell material endow the electrode with high capacity and excellent volume expansion control capability, solving the problem of poor electrode layer stability in traditional negative electrodes.

[0112] The fourth embodiment of the present invention also provides a battery, which includes a positive electrode material, an electrolyte, and the aforementioned negative electrode material. Understandably, the battery in this embodiment achieves an integrated improvement in electrochemical performance and structural stability through the synergistic design of the positive electrode material, electrolyte, and core-shell structured negative electrode material. The secondary pore structure of the core-shell material provides a permeation channel for the electrolyte, allowing lithium ions to rapidly diffuse to the core surface; simultaneously, the chemical stability of the shell reduces the probability of electrolyte decomposition, while the high-entropy characteristics of the coating layer suppress electrolyte reduction reactions by adjusting the interfacial electric field distribution. The battery combines the characteristics of the core-shell material with the functional requirements of the macroscopic battery system, solving the technical problems of short cycle life and poor rate performance of traditional silicon-based batteries through electrochemical matching and interfacial regulation among the components.

[0113] The foregoing has provided a detailed description of a core-shell material, preparation method, negative electrode material, and battery disclosed in the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention. Any modifications, equivalent substitutions, and improvements made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of preparing a core-shell material, characterized by: The preparation method of the core-shell material comprises the following steps: providing metal salt raw materials of aluminum, iron, cobalt, nickel, zinc and lanthanum, and pretreating the metal salt raw materials into high-entropy metal oxides; providing silicon particles as a core layer, and depositing the high-entropy metal oxides on the surface of the core layer after being gasified under a micro-oxygen environment to form a coating layer on the surface of the core layer to obtain Si@HEO particles; depositing zinc on at least part of the outer surface of the Si@HEO particles to form a growth layer; providing an aqueous zinc nitrate solution, an aqueous 2-methylimidazole solution and a Si@HEO solvent, dispersing the Si@HEO particles with the growth layer in the Si@HEO solvent, adding the aqueous zinc nitrate solution and the aqueous 2-methylimidazole solution, and growing a shell layer on the growth layer to obtain Si@HEO@ZIF particles; providing an acidic solution, mixing the acidic solution with the Si@HEO@ZIF particles, etching the outer surface of the shell layer of the Si@HEO@ZIF particles to form secondary pores, and performing separation treatment to obtain the core-shell material.

2. The method of claim 1, wherein: The pretreatment of the metal salt raw materials into high-entropy metal oxides comprises the following steps: providing deionized water and an alcohol solution, mixing the deionized water and the alcohol solution to form a metal salt solvent; providing metal salt raw materials of aluminum, iron, cobalt, nickel, zinc and lanthanum; dissolving the metal salt precursors of iron, cobalt, nickel, zinc and lanthanum in the metal salt solvent to form a gel; adding the metal salt raw material of aluminum when the gel starts to form to obtain a gel product; drying and calcining the gel product to obtain high-entropy oxides.

3. The method of claim 2, wherein: The drying and calcining of the gel product to obtain high-entropy oxides specifically comprises the following steps: heating the gel product from room temperature to 80-120℃ at a heating rate of 1-5℃ / min, keeping the temperature for 6-12 hours, and then cooling to room temperature to complete the drying treatment; after the drying treatment, heating from room temperature to 500-700℃ at a heating rate of 2-5℃ / min, keeping the temperature for 2-4 hours, and then cooling to room temperature to complete the calcination treatment.

4. The method of claim 2, wherein: The molar ratio of aluminum, iron, cobalt, nickel, zinc and lanthanum in the high-entropy oxides is aluminum:iron: cobalt:nickel:zinc:lanthanum=(0.08-0.16):(0.20-0.30):(0.15-0.25):(0.20-0.28):(0.08-0.15):(0.05-0.12); the particle size of the high-entropy metal oxides is 20-50nm, and the particle size distribution of the high-entropy metal oxides is less than 0.

3.

5. The method of claim 1, wherein: The growing of the shell layer on the growth layer comprises the following steps: dispersing the Si@HEO particles with the zinc layer in a Si@HEO solvent to obtain a first mixed solution, the volume ratio of the Si@HEO particles to the Si@HEO solvent in the mixed solution is 1:(10-20), and the Si@HEO solvent is a mixture of an alcohol and an ionic liquid, wherein the volume fraction of the ionic liquid is 5-30%; The first mixed solution is added with an aqueous zinc nitrate solution and an aqueous 2-methylimidazole solution, heated from room temperature to 30°C and stirred at a speed of 100-300 rpm for 6-12 hours to obtain a second mixed solution, the shell layer is grown by the reaction of 2-methylimidazole and zinc ions in the aqueous zinc nitrate solution and the zinc layer of the growth layer, and the molar ratio of zinc to 2-methylimidazole in the second mixed solution is (0.01-0.5):(0.1-1.0); The second mixed solution is centrifuged at a speed of 8000-12000 rpm for 5-15 minutes to obtain solid particles separated from the second mixed solution, and the solid particles separated from the second mixed solution are dried at a temperature of 60-80°C for 6-12 hours to obtain Si@HEO@ZIF particles.

6. The method of claim 1, wherein: The acid solution etches the outer surface of the shell layer of the Si@HEO@ZIF particles to form secondary pores, which includes: An acid solution is provided, the acid solution and the Si@HEO@ZIF particles are mixed to form a third mixed solution and are left to stand for 10-40 seconds to etch the shell layer with the acid solution to form secondary pores, the third mixed solution is centrifuged at a speed of 8000-12000 rpm to obtain solid particles separated from the third mixed solution, and the solid particles separated from the third mixed solution are washed and dried at 60-80°C for 2-4 hours to obtain a core-shell material, wherein the volume ratio of the acid solution to the Si@HEO@ZIF particles is (10-20):

1.

7. A core-shell material prepared by the method of any one of claims 1 to 6. The core-shell material includes a core layer, a cladding layer and a shell layer formed in sequence from inside to outside, and a growth layer arranged between the cladding layer and the shell layer for connecting the cladding layer and the shell layer, and the core layer and the cladding layer are connected by ionic bonds; wherein the core layer in the core-shell material is silicon, the cladding layer is a high-entropy oxide, and the shell layer is ZIF-8, and the shell layer is distributed with secondary pores.

8. The core-shell material of claim 7, wherein: The diameter of the core layer is in the range of 80-200 nm, the thickness of the cladding layer is 1-2 nm, the thickness of the growth layer is 2-3 nm, the thickness of the shell layer is 15-20 nm, the depth of the secondary pores is 5-10 nm, and the diameter of the secondary pores is 3-15 nm.

9. A negative electrode material, characterized by: The battery includes a positive electrode material, an electrolyte and a negative electrode material as claimed in claim 9.

10. A battery, characterized by: The battery includes a positive electrode material, an electrolyte and a negative electrode material as claimed in claim 9.

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