Battery cells and their manufacturing methods, battery devices, electrical devices and energy storage devices

Abstract

This application provides a battery cell and its manufacturing method, battery device, power consumption device, and energy storage device. The battery cell includes a casing and a positive electrode, a separator, a negative electrode, and an electrolyte located within the casing. The separator is located between the positive electrode and the negative electrode. The negative electrode includes a negative current collector and a negative electrode material layer on the surface of the negative current collector. The negative electrode material layer includes modified silicon particles, and the modified silicon particles include silicon particles and a protective layer on the surface of the silicon particles. This application also provides a biomimetic multi-level pore size silicon negative electrode surface protective film. By simulating the multi-level pore network structure of natural sponge needles, a three-layer functional protection system with a gradient pore size distribution is constructed on the surface of the silicon negative electrode. This protective film achieves synergistic optimization of stress buffering, ion conduction, and chemical stability through specific structural levels and composition ratios.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a battery cell and its manufacturing method, battery device, power consumption device and energy storage device. Background Technology

[0002] Silicon-based anode materials are considered a core technology for next-generation lithium-ion batteries due to their ultra-high theoretical specific capacity (4200 mAh / g), playing a crucial role in achieving breakthroughs in battery energy density. However, silicon undergoes a volume change of over 300% during lithiation / delithiation, and this drastic volume effect brings a series of serious technical challenges, including active particle pulverization, conductive network damage, repeated SEI film rupture, and the resulting rapid capacity decay and short cycle life. As a critical interface between the anode and the electrolyte, the stability of the SEI film directly determines the electrochemical performance of the silicon anode. An ideal SEI film should possess multiple functions, including ionic conductivity, electronic insulation, chemical stability, and mechanical adaptability, but existing SEI films often exhibit contradictions between these performance requirements. Traditional surface protection strategies mainly include carbon coating, metal oxide coating, and polymer coating, but these methods mostly employ single-scale protective layer designs, making it difficult to effectively cope with the extreme operating conditions of silicon anodes. Summary of the Invention

[0003] This application provides a battery cell and its manufacturing method, battery device, power supply device and energy storage device, which at least facilitate the synergistic optimization of stress buffering, ion conduction and chemical stability.

[0004] This application provides a single battery cell, comprising: The housing and the positive electrode, the separator, the negative electrode and the electrolyte located within the housing, wherein the separator is located between the positive electrode and the negative electrode; The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer located on the surface of the negative electrode current collector. The negative electrode material layer includes modified silicon particles. The modified silicon particles include silicon particles and a protective layer on the surface of the silicon particles. The protective layer includes a first protective layer and a second protective layer stacked sequentially from the inside to the outside. The material of the first protective layer includes at least one of silicon oxide, zirconium oxide, and aluminum oxide. The material of the second protective layer includes at least one of silicon oxide, zirconium oxide, and aluminum oxide. Both the first protective layer and the second protective layer have pores, and the pore size of the pores in the first protective layer is smaller than the pore size of the pores in the second protective layer. At least one of the pores in the first protective layer and the pores in the second protective layer is filled with an ionic liquid.

[0005] Optionally, the mass of silicon oxide accounts for 35wt% to 50wt% of the total mass of the protective layer, the mass of zirconium oxide accounts for 25wt% to 40wt% of the total mass of the protective layer, and the mass of aluminum oxide accounts for 25wt% to 40wt% of the total mass of the protective layer.

[0006] Optionally, the pore size of the first protective layer is in the range of 2nm to 50nm; and / or, the pore size of the second protective layer is in the range of 150nm to 250nm.

[0007] Optionally, the protective layer further includes a third protective layer located on the surface of the second protective layer away from the first protective layer, and the pore size of the third protective layer is larger than that of the second protective layer.

[0008] Optionally, the pore size range of the first protective layer is 2nm~5nm; the pore size range of the second protective layer is 20nm~50nm; and the pore size range of the third protective layer is 150nm~250nm.

[0009] Optionally, the cation of the ionic liquid is selected from one or more of imidazolium, pyrrolidineium, and piperidinium, and the anion is selected from FSI. - Or TFSI - .

[0010] Optionally, the ionic liquid may also include a silane coupling agent.

[0011] Optionally, the mass of the silane coupling agent is 0.5wt% to 3wt% of the total mass of the protective layer.

[0012] Optionally, the total thickness of the protective layer is 30nm~300nm.

[0013] Optionally, the particle size of the silicon particles is 100nm~300nm.

[0014] This application also provides a method for manufacturing a single battery cell, comprising: Silicon particles are provided, and the silicon particles are cleaned and activated. A protective layer is formed on the surface of the silicon particles. The protective layer includes a first protective layer and a second protective layer stacked sequentially from the inside to the outside. The materials of the first protective layer and the second protective layer both include silicon oxide, zirconium oxide and aluminum oxide, and the pore size of the first protective layer is smaller than that of the second protective layer. Ionic liquid is filled into the pores of the first protective layer and the second protective layer to obtain modified silicon particles; A negative electrode active material is prepared, wherein the negative electrode active material comprises the modified silicon particles, a conductive agent, and a binder; The negative electrode active material is coated onto the surface of the negative electrode current collector and dried to obtain a negative electrode sheet; The positive electrode, separator, and negative electrode are stacked in sequence, then stacked or wound into a housing, and electrolyte is injected into the housing. After formation, a single battery cell is obtained.

[0015] Optionally, forming the protective layer on the surface of the silicon particles includes: The silicon source, zirconium source, and aluminum source are added to the solvent and mixed, and then the first template agent and the second template agent are added. Add a dilute deionized aqueous solution of hydrochloric acid dropwise to the mixed solution, and then add the silicon particles; Increase the temperature and add dilute ammonia to adjust the pH to 8.5-9; After the reaction is complete, the particulate matter is collected by centrifugation. The particles are calcined at 550°C to 580°C to remove the first template agent and the second template agent, resulting in silicon particles with the protective layer. The positions occupied by the first template agent form pores in the first protective layer, and the positions occupied by the second template agent form pores in the second protective layer.

[0016] Optionally, the first template agent is selected from hexadecyltrimethylammonium bromide, Pluronic F127, tetramethylammonium hydroxide, or tetraethylammonium hydroxide; the second template agent is selected from polystyrene microspheres.

[0017] Optionally, the protective layer further includes a third protective layer, which is located on the surface of the second protective layer away from the first protective layer, and the pore size of the third protective layer is larger than that of the second protective layer; a third template agent is added simultaneously with the first template agent and the second template agent, wherein the first template agent is selected from hexadecyltrimethylammonium bromide or Pluronic F127, the second template agent is selected from tetramethylammonium hydroxide or tetraethylammonium hydroxide, and the third template agent is selected from polystyrene microspheres, and after calcination, the positions occupied by the third template agent form the pores of the third protective layer.

[0018] This application also provides a battery device, including a battery cell as described above or a battery cell manufactured by the manufacturing method of the battery cell as described above, the battery device including one or more of a battery module, a battery pack, and an energy storage battery.

[0019] In another aspect, this application provides an electrical device that includes a battery device as described above, the battery device being used to provide electrical energy.

[0020] Another aspect of this application provides an energy storage device, which includes a battery device as described above, the battery device being used to store electrical energy.

[0021] The technical solution provided in this application has at least the following advantages: This application provides a biomimetic multi-level pore size silicon anode surface protective film. By simulating the multi-level pore network structure of natural sponge needles, a three-layer functional protective system with gradient pore size distribution is constructed on the silicon anode surface. This protective film achieves synergistic optimization of stress buffering, ion conduction and chemical stability through specific structural levels and composition ratios.

[0022] The battery cells provided in this application can be widely used in energy storage fields requiring high energy density and long cycle life, including high-end electric vehicle battery systems, portable electronic devices, and large-scale energy storage power stations. These battery cells are expected to overcome existing bottlenecks, achieving comprehensive improvements in energy density, cycle life, and safety performance, enabling high-capacity battery cells suitable for long-term energy storage applications, such as energy storage systems that can operate continuously for 4 to 8 hours at rated power. This provides key technological support for the development of next-generation high-performance electrochemical energy storage systems. Attached Figure Description

[0023] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 The flowchart corresponds to the manufacturing method of the battery cell provided in the embodiments of this application. Detailed Implementation

[0025] As the background technology indicates, existing silicon anode surface protection technologies mainly fall into three categories: carbon coating, oxide coating, and polymer coating. Carbon coating technology forms a carbon protective layer on the silicon particle surface through chemical vapor deposition (CVD) or pyrolysis of organic precursors. Its working principle utilizes the conductivity of the carbon layer to maintain the electron conduction pathway, while simultaneously alleviating some volumetric stress through the flexibility of carbon. A typical carbon-coated structure is a core-shell Si@C composite particle, with a carbon layer thickness typically ranging from 5 nm to 50 nm. Oxide coating technology uses atomic layer deposition (ALD) or sol-gel methods to deposit oxide films such as Al2O3 and TiO2 on the silicon surface. Its protection mechanism relies on the chemical inertness and mechanical support of the oxides to stabilize the silicon surface and inhibit direct contact with the electrolyte. Oxide coatings are typically dense amorphous structures with a thickness of 2 nm to 20 nm. Polymer coating technology forms a polymer protective layer on the silicon surface through polymerization or physical adsorption, such as polyacrylic acid (PAA) and polyvinyl alcohol (PVA). Its working principle utilizes the viscoelasticity of the polymer to adapt to changes in silicon volume, while simultaneously enhancing interfacial bonding through the interaction of functional groups with the silicon surface. These existing technologies share the common characteristic of employing a single material and a single-scale protective layer design, resulting in a relatively simple structure that primarily relies on the properties of the material itself for protection. In practical operation, these protective layers function through two mechanisms: physical isolation and chemical stabilization. Physical isolation refers to the protective layer acting as a barrier to prevent direct contact between silicon and the electrolyte, reducing side reactions; chemical stabilization refers to the protective layer providing long-term protection through the formation of stable chemical bonds with the silicon surface or through its own chemical inertness.

[0026] Existing silicon anode surface protection technologies exhibit significant limitations and technical defects when dealing with extreme volume changes in silicon. First, single-scale protective layer designs cannot simultaneously meet multiple functional requirements. While carbon coatings maintain conductivity, their buffering capacity against volume expansion is limited, and the carbon layer is prone to cracking during significant silicon expansion. Oxide coatings, although chemically stable, are rigid and lack adaptability to volume changes, and their dense structure hinders lithium-ion transport. Polymer coatings, while possessing some flexibility, lack sufficient mechanical strength and are prone to degradation and detachment after repeated cycles. Second, the pore structure of existing protective layers is uncontrollable. Most technologies produce protective layers that are either dense and non-porous, hindering ion transport, or randomly porous, making precise control of ion transport impossible. Third, the interfacial bonding strength between the protective layer and the silicon substrate is insufficient, especially during drastic silicon volume changes. Interfacial stress concentration easily leads to separation of the protective layer from the silicon substrate, resulting in loss of protective effect. Fourth, most existing technologies neglect the stress distribution and transmission mechanisms within the protective layer. When silicon expands, the stress borne by the protective layer often exceeds its mechanical limits, leading to cracking and failure. Fifth, traditional electrolyte additives such as LiPF6 are prone to hydrolysis in the silicon anode environment, generating HF, which further corrodes the silicon surface and protective layer, exacerbating interfacial instability. Finally, there is a lack of effective means to evaluate and optimize the performance of the protective layer. Existing electrochemical testing methods are insufficient to monitor the structural evolution of the protective layer in real time during cycling, and cannot provide accurate feedback information for protective layer design.

[0027] In recent years, researchers have begun to focus on the application of multi-scale structural design in materials protection. The hierarchical porous structure widely present in biomaterials has provided new inspiration for solving this technical challenge. Biomaterials such as sponges have multi-level porous networks ranging from nanometers to micrometers, which can maintain structural integrity and functional continuity while withstanding external stress. This design concept has important reference value for developing SEI films that adapt to changes in the volume of silicon anodes.

[0028] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0029] In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0030] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] In the accompanying drawings, the thickness of layers, films, panels, regions, etc., is enlarged for clarity. Throughout the specification, the same reference numerals denote the same elements. It should be understood that when referring to an element (e.g., a layer, film, region, or substrate) as being "on" another element, it may be directly on that other element, or intermediate elements may be present. Conversely, when referring to an element as being "directly on" another element, it indicates that no intermediate elements are present.

[0032] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0033] This application provides a single battery cell, comprising: The housing and the positive electrode, the separator, the negative electrode and the electrolyte located within the housing, wherein the separator is located between the positive electrode and the negative electrode; The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer located on the surface of the negative electrode current collector. The negative electrode material layer includes modified silicon particles. The modified silicon particles include silicon particles and a protective layer on the surface of the silicon particles. The protective layer includes a first protective layer and a second protective layer stacked sequentially from the inside to the outside. The material of the first protective layer includes at least one of silicon oxide, zirconium oxide, and aluminum oxide. The material of the second protective layer includes at least one of silicon oxide, zirconium oxide, and aluminum oxide. Both the first protective layer and the second protective layer have pores, and the pore size of the pores in the first protective layer is smaller than the pore size of the pores in the second protective layer. At least one of the pores in the first protective layer and the pores in the second protective layer is filled with an ionic liquid.

[0034] Battery cells can be classified into cylindrical cells, prismatic cells, and pouch cells according to their type.

[0035] This application provides a biomimetic multi-level pore size silicon anode surface protective film. By simulating the multi-level pore network structure of natural sponge needles, a three-layer functional protective system with gradient pore size distribution is constructed on the silicon anode surface. This protective film achieves synergistic optimization of stress buffering, ion conduction and chemical stability through specific structural levels and composition ratios.

[0036] The battery cells provided in this application can be widely used in energy storage fields requiring high energy density and long cycle life, including high-end electric vehicle battery systems, portable electronic devices, and large-scale energy storage power stations. These battery cells are expected to overcome existing bottlenecks, achieving comprehensive improvements in energy density, cycle life, and safety performance, enabling high-capacity battery cells suitable for long-term energy storage applications, such as energy storage systems that can operate continuously for 4 to 8 hours at rated power. This provides key technological support for the development of next-generation high-performance electrochemical energy storage systems.

[0037] Existing silicon anode surface protection technologies mostly employ protective layer designs with a single material and single pore size, such as dense oxide coatings, uniform carbon coatings, or single polymer coatings. These methods are essentially passive protection strategies, attempting to prevent silicon from contacting the electrolyte through physical barriers. This application breaks through traditional thinking, proposing a multi-scale collaborative protection mechanism that actively adapts to changes in silicon volume based on the design concept of a biomimetic sponge multi-level pore network. This shift in design philosophy transforms the protective film from a simple physical barrier into an intelligent response system with differentiated functional divisions, fundamentally changing the technical path of silicon anode protection.

[0038] Traditional protective technologies typically employ single oxide materials, such as pure SiO2, Al2O3, or TiO2 coatings, lacking a systematic consideration of silicon volume variations. This application innovatively designs a SiO2-ZrO2-Al2O3 ternary oxide synergistic system, achieving dual optimization of functional division and thermal expansion matching through precise mass ratio control (4:3:3). The SiO2 component provides strong chemical bonding with the silicon substrate, the ZrO2 component contributes high-temperature stability and mechanical support, and the Al2O3 component regulates lithium-ion transport kinetics. The thermal expansion coefficients of the three oxides are matched and designed to form a composite system that coordinates deformation with the silicon substrate. This multi-element synergistic design is a first in the field of protective films, resolving the fundamental contradiction at the mechanistic level that a single material cannot simultaneously meet multiple performance requirements.

[0039] Existing methods for preparing porous protective membranes mostly employ template methods or phase separation methods, which have limited precision in pore size control and make it difficult to achieve a continuous gradient distribution. This application proposes a gradient pore size construction mechanism based on the difference in precursor hydrolysis and polycondensation rates. By precisely controlling the hydrolysis rate relationship of the three precursors, Si, Zr, and Al, the hydrolysis rate of the silicon source is at least 1.5 times that of the zirconium source, and the hydrolysis rate of the zirconium source is at least 1.5 times that of the aluminum source, achieving self-assembly of the pore size gradient from the inside out. This kinetic control method can simultaneously form an ordered distribution of micropores (2nm~5nm), mesopores (20nm~50nm), and macropores (150nm~250nm) in a single preparation process, avoiding the process complexity and interface matching problems of traditional multi-step methods, and providing a new technical path for the controllable preparation of hierarchical porous materials.

[0040] Most existing electrolyte additives or interface modifiers are based on the traditional PF6. - The system is prone to HF corrosion in the strong reducing environment of the silicon anode. This application introduces [EMIM][FSI] ionic liquids to fill the hierarchical pores, achieving a dual effect of "structural protection + chemical film formation". FSI - Anions not only possess excellent electrochemical stability, but their unique film-forming mechanism also enables them to form a stable interfacial protective layer on the silicon surface, creating a synergistic protective effect with the hierarchical pore structure. This design, combining ionic liquids with a porous oxide framework, maintains the mechanical stability of the inorganic components while leveraging the interfacial adaptability of the organic components, representing an innovative combination of materials and electrochemical interface engineering.

[0041] Existing protective film fabrication technologies are often limited to single-application scenarios at the laboratory scale, lacking systematic solutions for different engineering needs. This application proposes a hierarchical fabrication strategy at the particle and electrode levels, developing corresponding technical routes to address the heat treatment limitations and process constraints at different application levels: the particle level employs a complete process flow of high-temperature calcination to remove the template, suitable for the pretreatment and modification of silicon particles; the electrode level uses a milder process of low-temperature phase separation and solvent extraction to remove the template, suitable for the overall processing after electrode forming. This hierarchical design not only expands the applicability of the technology but also reflects a systematic approach to translating basic research into engineering applications.

[0042] Traditional protection technologies focus on optimizing single functions, such as improving ionic conductivity or enhancing mechanical strength, lacking a systematic consideration of the synergistic effects of multiple transport mechanisms. This application establishes a system that combines macroporous buffering silicon expansion stress, mesoporous regulation of ion diffusion rates, and microporous realization of Li… +A three-dimensional collaborative transport network for selective lithium ion transport is constructed. The outer macropores provide space to accommodate changes in silicon volume, the middle mesopores optimize ion transport kinetics through confinement effects, and the inner micropores enable selective sieving of lithium ions. These three layers complement and work synergistically. This multi-scale network construction logic provides a systematic solution to the complex technical challenges of silicon anodes, representing a technological development trend from "single-point breakthroughs" to "system optimization."

[0043] Existing methods for evaluating protective films mostly rely on static characterization after cycling, making it difficult to understand the dynamic evolution of the protective effect in real time. The in-situ strain electrochemical monitoring technology developed in this application can track changes in the integrity of the film structure in real time during cycling from 0 to 100% SOC, providing quantitative feedback for protective film design optimization. This dynamic monitoring capability not only helps to deepen the understanding of the protection mechanism but also provides a powerful tool for the continuous improvement and quality control of the protective film, embodying the advanced concept of integrating material design and performance evaluation, and providing important technical support for the industrial application of silicon anode protective film technology.

[0044] Optionally, the silicon oxide accounts for 35wt% to 50wt% of the total mass of the protective layer, specifically 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, 41wt%, 42wt%, 43wt%, 44wt%, 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, and 50wt%, and the zirconium oxide accounts for 25wt% to 40wt% of the total mass of the protective layer, specifically 25wt%, 26wt%, 27wt%, 28wt%, and 29wt%. The percentages of alumina in the protective layer are 25wt% to 40wt%, specifically 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, and 40wt%, respectively.

[0045] Optionally, the aperture range of the first protective layer is 2nm to 50nm, specifically 2nm, 3nm, 4nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, or 50nm; and / or, the aperture range of the second protective layer is 150nm to 250nm, specifically 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 210nm, 220nm, 230nm, 240nm, or 250nm.

[0046] Optionally, the protective layer further includes a third protective layer located on the surface of the second protective layer away from the first protective layer, and the pore size of the third protective layer is larger than that of the second protective layer.

[0047] Optionally, the aperture range of the first protective layer is 2nm to 5nm, specifically 2nm, 3nm, 4nm, or 5nm; the aperture range of the second protective layer is 20nm to 50nm, specifically 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, or 50nm; and the aperture range of the third protective layer is 150nm to 250nm, specifically 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 210nm, 220nm, 230nm, 240nm, or 250nm.

[0048] Optionally, the cation of the ionic liquid is selected from one or more of imidazolium, pyrrolidineium, and piperidinium, and the anion is selected from FSI. - Or TFSI - .

[0049] Optionally, the ionic liquid may also include a silane coupling agent.

[0050] Optionally, the mass of the silane coupling agent is 0.5wt% to 3wt% of the total mass of the protective layer, specifically 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, or 3wt%.

[0051] Optionally, the total thickness of the protective layer is 30nm~300nm, specifically 30nm, 40nm, 50nm, 60nm; 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm, and 300nm.

[0052] Optionally, the silicon particles having the protective layer have an equivalent coefficient of thermal expansion of less than 5%.

[0053] Optionally, the particle size of the silicon particles is 100nm~300nm, specifically 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm, or 300nm.

[0054] Optionally, the cathode material can be composed of various high-performance materials to suit different application requirements. Layered oxide cathode materials include LiCoO2, ternary materials (NCM111 / 523 / 622 / 811 / 955, etc.), NCA, high-nickel materials, quaternary materials, and cobalt-free materials; spinel structure cathode materials include LiMn2O4 and high-voltage spinel (LiNi). 0.5 Mn 1.5 O4), doped and modified spinel, etc.; polyanionic compounds include LiFePO4, LiMnPO4, Li3V2(PO4)3, LiFe 0.5 Mn 0.5 PO4, etc.; lithium-rich manganese-based materials include the xLi2MnO3·(1-x)LiMO2 system and its coating and modified materials; conversion-type cathode materials include high-capacity cathode materials such as sulfides and fluorides.

[0055] The positive electrode formulation comprises 85wt%~98wt% positive electrode active material, 1wt%~10wt% conductive agent, and 2wt%~8wt% binder. The conductive agent is selected from carbon-based conductive materials such as SuperP, Ketjen Black, carbon nanotubes, graphene, and carbon fibers, or their composites; the binder is selected from PVDF, PTFE, PVDF-HFP, polyimide, and water-based binders. The positive electrode current collector uses aluminum foil, carbon-coated aluminum foil, titanium foil, or other conductive substrates.

[0056] Optionally, the negative electrode includes various silicon-based negative electrode material systems. Silicon-based active materials include nano-silicon, micro-silicon, silicon-carbon composites, and SiO₂. x Materials (x=0.8~1.2), silicon alloy materials, etc. Nano-silicon particles range in size from 50nm to 500nm, with a specific surface area of ​​20m². 2 / g~200m 2 / g; Micron-sized silicon particles range from 1μm to 50μm, with a specific surface area of ​​1m². 2 / g~50m 2 / g; Silicon content in silicon-carbon composite materials is 30wt%~95wt%, and carbon coating thickness is 2nm~50nm; SiO x The x-value in the material can be selected from 0.9 to 1.1, combining the high capacity of silicon with the stability of silicon oxide.

[0057] The formulation design of silicon anodes requires coordinated optimization with protective film technology. The content of silicon-based active material is 80wt%~95wt%, conductive agent content is 2wt%~10wt%, and binder content is 5wt%~18wt%. Conductive agents include SuperP, carbon nanotubes, and vapor-grown carbon fibers; binders include high-elasticity binders such as polyacrylic acid (PAA), sodium carboxymethyl cellulose (CMC) / styrene-butadiene rubber (SBR) composite systems, polyimide, and cross-linked polymers. The anode current collector uses copper foil, nickel foil, or carbon-coated copper foil.

[0058] Optionally, the electrolyte needs to be compatible with FSI. - Film-forming mechanisms are designed synergistically. Solvent systems include single or mixed systems of carbonates (EC, PC, EMC, DMC, DEC, etc.), ethers (DME, DOL, DEGDME, etc.), esters, and nitriles. Lithium salt systems include LiPF6, LiTFSI, LiFSI, LiBF4, LiDFOB, etc., among which LiFSI interacts with FSI in the protective film. - The film-forming system has good compatibility.

[0059] The selection of functional additives revolves around enhancing FSI - The film-forming effect is described, including film-forming additives such as fluoroethylene carbonate (FEC), vinylene carbonate (VC), and propanesulfonate lactone (PS), with a dosage of 0.5wt%~10wt%; flame retardant additives such as trimethyl phosphate (TMP) and phosphazene compounds, with a dosage of 1wt%~15wt%; high and low temperature additives such as difluoroethyl carbonate (DFEC) and fluorolinear carbonates, with a dosage of 1wt%~20wt%; and interface stabilizing additives such as lithium bis(oxalato)borate (LiBOB) and lithium difluorophosphate (LiDFP), with a dosage of 0.1wt%~5wt%.

[0060] Optionally, the separator may be made of polyolefin substrate or modified separator. Polyolefin separators include PE, PP, PP / PE / PP multilayer composite separators, etc., with a thickness of 10μm~30μm and a porosity of 35%~65%; ceramic coated separators use inorganic particulate coatings such as Al2O3, SiO2, TiO2, etc., with a coating thickness of 1μm~10μm; high-performance polymer separators include high-temperature resistant materials such as polyimide, PEEK, PPS, etc.; functionalized separators include special modified separators such as lithium-philic coatings, solid electrolyte coatings, and flame-retardant coatings.

[0061] This application also provides a method for manufacturing a single battery cell, such as... Figure 1 As shown, it includes: S1. Preparation of modified silicon particles, specifically including the following steps: Silicon particles are provided, and the silicon particles are cleaned and activated. A protective layer is formed on the surface of the silicon particles. The protective layer includes a first protective layer and a second protective layer stacked sequentially from the inside to the outside. The materials of the first protective layer and the second protective layer both include silicon oxide, zirconium oxide and aluminum oxide, and the pore size of the first protective layer is smaller than that of the second protective layer. Ionic liquid is filled into the pores of the first protective layer and the second protective layer to obtain modified silicon particles; S2. Prepare a negative electrode active material, wherein the negative electrode active material includes the modified silicon particles, a conductive agent, and a binder; S3. Coat the negative electrode active material onto the surface of the negative electrode current collector and dry it to obtain a negative electrode sheet; S4. The positive electrode, separator and negative electrode are stacked in sequence, and then placed into the housing after stacking or winding. Electrolyte is injected into the housing and a formation process is carried out to obtain a battery cell.

[0062] Optionally, forming the protective layer on the surface of the silicon particles includes: The silicon source, zirconium source, and aluminum source are added to the solvent and mixed, and then the first template agent and the second template agent are added. Add a dilute deionized aqueous solution of hydrochloric acid dropwise to the mixed solution, and then add the silicon particles; Increase the temperature and add dilute ammonia dropwise to adjust the pH to 8.5-9; After the reaction is complete, the particulate matter is collected by centrifugation. The particles are calcined at 550°C to 580°C to remove the first template agent and the second template agent, resulting in silicon particles with the protective layer. The positions occupied by the first template agent form pores in the first protective layer, and the positions occupied by the second template agent form pores in the second protective layer.

[0063] Optionally, the first template agent is selected from hexadecyltrimethylammonium bromide, Pluronic F127, tetramethylammonium hydroxide, or tetraethylammonium hydroxide; the second template agent is selected from polystyrene microspheres.

[0064] Optionally, the protective layer further includes a third protective layer, which is located on the surface of the second protective layer away from the first protective layer, and the pore size of the third protective layer is larger than that of the second protective layer; a third template agent is added simultaneously with the first template agent and the second template agent, wherein the first template agent is selected from hexadecyltrimethylammonium bromide or Pluronic F127, the second template agent is selected from tetramethylammonium hydroxide or tetraethylammonium hydroxide, and the third template agent is selected from polystyrene microspheres, and after calcination, the positions occupied by the third template agent form the pores of the third protective layer.

[0065] Step S1 can be performed as follows: In the raw material pretreatment stage, silicon particles require surface cleaning and activation. Surface cleaning uses a dilute HF solution (1wt%~5wt%) to remove the surface oxide layer for 30s~5min, followed by thorough rinsing with deionized water and dehydration with anhydrous ethanol. Surface activation can selectively involve plasma treatment, ultraviolet ozone treatment, or silanization modification to enhance the interfacial adhesion of the subsequent protective film.

[0066] The ternary precursor solution was prepared using a stepwise mixing process. Under argon protection, aluminum isopropoxide (5 g–15 g) and acetylacetone (2 mL–6 mL) were added sequentially to anhydrous ethanol (500 mL–1000 mL) for complexation and stabilization for 30 min. Zirconium n-butoxide (8 g–20 g) was then added and stirred for dissolution for 60 min. Finally, tetraethyl orthosilicate (12 g–30 g) was added and mixed thoroughly. The molar ratio of the three components was calculated as SiO2, ZrO2, and Al2O3 in a 4:3:3 ratio, with an allowable adjustment of ±10%.

[0067] The sol-gel reaction was controlled using dynamic pH and temperature management. Silicon particles (50g~200g) were dispersed in the aforementioned ternary precursor solution and ultrasonically dispersed for 15min~30min to form a homogeneous suspension. Under vigorous stirring, a 0.1mol / L HCl aqueous solution was added dropwise at a rate of 0.5mL / min~1.0mL / min. The molar ratio of water to the total molar amount of the three precursors (tetraethyl orthosilicate, zirconium butoxide, and aluminum isopropoxide) in the HCl aqueous solution was controlled at 3:1. The reaction temperature was maintained at (20±5)℃ during the addition process. The pH was dynamically controlled: initially 2.5~3.0 to promote hydrolysis, then adjusted to 5~6 after 30min~60min to promote condensation. The total reaction time was 2h~6h until a stable gel was formed.

[0068] Multi-level pore size was constructed using a template synergistic method. Polystyrene microsphere dispersion (200 nm particle size, 10 wt% solid content, 5%–15% of precursor mass) was pre-added to the ternary precursor solution as a macroporous template, hexadecyltrimethylammonium bromide (1 wt%–5 wt%) as a mesoporous template, and tetraethylammonium hydroxide aqueous solution (0.5 wt%–2 wt%) as a microporous template. The templates were added in the following sequence: macroporous templates were added during precursor mixing, mesoporous templates were added at the initial stage of hydrolysis, and microporous templates were added during the polycondensation stage.

[0069] The heat treatment and template removal employed a programmed temperature rise process. The gel product was first vacuum dried at 80℃~100℃ for 12h~24h to remove the solvent, followed by programmed temperature rise: increasing to 200℃ at 2℃ / min and holding for 2h to remove the organic solvent; then increasing to 450℃ at 1℃ / min and holding for 1h, during which the polystyrene microspheres thermally decomposed and volatilized to form a macroporous structure, while tetraethylammonium hydroxide (thermal decomposition temperature approximately 300℃~400℃) was also largely decomposed and removed; finally, increasing to 550℃ at 1℃ / min and holding for 2h~4h, this stage removed hexadecyltrimethylammonium bromide and remaining organic template agent residues, and promoted the densification of the oxide network. The entire process was carried out in an air atmosphere, with the heating and cooling rates controlled below 5℃ / min to avoid thermal stress cracking.

[0070] The ionic liquid backfilling process was carried out after the oxide framework was prepared and cooled to room temperature. An anhydrous acetonitrile solution of [EMIM][FSI] (concentration 10wt%~30wt%) was prepared, and the porous oxide-coated silicon particles were immersed in this solution under vacuum at 50℃~80℃ for 4h~8h to ensure sufficient penetration of the ionic liquid into the hierarchical porous network. After impregnation, the solvent was removed by vacuum drying at 80℃ for 2h~4h to obtain the final modified silicon particles.

[0071] During the preparation process, a multi-level quality control system is established to ensure the consistency and reproducibility of the protective layer performance.

[0072] Raw material quality control includes precursor purity testing, silicon particle size distribution determination, and ionic liquid moisture content analysis. Precursor purity requirements are ≥99.5%, moisture content <100ppm; silicon particle D90 / D10 <3.0, specific surface area deviation <10%; [EMIM][FSI] moisture content <50ppm, acid value <0.1mgKOH / g.

[0073] Online detection methods are used to monitor process parameters. Key parameters such as viscosity changes (Buchner viscometer, 25℃), dynamic pH changes, and gelation time are monitored during sol preparation. Process parameters such as heating rate, atmosphere purity, and weight loss curves are monitored during heat treatment. Operational parameters such as impregnation solution concentration, treatment time, and drying weight loss are monitored during the ionic liquid introduction process.

[0074] Final product quality inspection includes structural characterization, performance testing, and consistency assessment. Structural characterization may include, but is not limited to, conventional methods such as surface morphology and film thickness observation, specific surface area and pore size distribution determination, and crystal phase composition analysis; performance testing may include the evaluation of indicators such as ionic conductivity, mechanical strength, and thermal stability; consistency assessment ensures the stability of product quality through batch-to-batch comparison and statistical analysis.

[0075] Through the aforementioned process flow and quality control system, the biomimetic multi-level pore size silicon anode surface protective layer of this application can be mass-produced, providing reliable technical support for the industrial application of silicon-based lithium-ion batteries.

[0076] This application also provides a battery device, including a battery cell as described above or a battery cell manufactured by the manufacturing method of the battery cell as described above, the battery device including one or more of a battery module, a battery pack, and an energy storage battery.

[0077] In another aspect, this application provides an electrical device that includes a battery device as described above, the battery device being used to provide electrical energy.

[0078] Electrical devices include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0079] Another aspect of this application provides an energy storage device, which includes a battery device as described above, the battery device being used to store electrical energy.

[0080] Energy storage devices include, but are not limited to, residential energy storage cabinets, commercial energy storage cabinets, energy storage containers, energy storage racks, energy storage power stations, energy storage battery packs, or portable energy storage systems. Energy storage devices may also include energy management systems (EMS), battery management systems (BMS), and power conversion systems (PCS).

[0081] The following are specific embodiments illustrating this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0082] To verify the effect of the biomimetic multi-level pore size silicon anode surface protective film proposed in this application on improving the cycle stability, rate performance, and interface stability of silicon-carbon anodes, this application designed a series of embodiments and comparative examples (as shown in Tables 1-1 to 1-3) to systematically explore the influence of key technical elements such as the three-layer gradient pore size structure, the ternary oxide synergistic system, and ionic liquid pore filling on battery performance. By comparing different technical solutions such as no protective film, single-layer pore size structure, reverse gradient pore size, single oxide system, and no ionic liquid filling, this application can clearly demonstrate the necessity and effectiveness of each innovation and further explore the influence of key process parameters on performance. The following details the selection of raw materials, the protective film preparation process, the battery assembly process, and the testing methods.

[0083] The materials used in the following embodiments and comparative examples are as follows.

[0084] The silicon-based anode material uses nano-silicon powder as the core active material, with a particle size distribution ranging from 100 nm to 300 nm and a specific surface area of ​​50 m². 2 / g~100m 2 / g, purity not less than 99.5%. The selection of nano-silicon is based on its high specific capacity and suitable particle size, which ensures sufficient specific surface area for protective film coating while avoiding agglomeration problems caused by ultrafine particles. Before use, the silicon powder requires surface cleaning and activation treatment. Specifically, it is ultrasonically treated in dilute hydrochloric acid solution for 30 minutes to remove the surface oxide layer and adsorbed impurities, followed by washing with deionized water and anhydrous ethanol sequentially until neutral, and finally drying in a vacuum environment at 80℃ for 12 hours.

[0085] The protective layer precursor materials include silicon-based precursors and metal alkoxide precursors. Specifically, tetraethyl orthosilicate (TES) is used as the silicon-based precursor, and zirconium butoxide (Zr₄H₁₆) and aluminum isopropoxide (AAU) are used as the metal alkoxide precursors. TES, with the molecular formula Si(OC₂H₅)₄ and a purity of not less than 99%, has a relatively fast hydrolysis rate. Zr₄, with the molecular formula Zr(OC₄H₁₆)₄ and a purity of not less than 97%, has a moderate hydrolysis rate. AAU, with the molecular formula Al(OC₃H₇)₃ and a purity of not less than 98%, has a relatively slow hydrolysis rate. The difference in hydrolysis rates among the three precursors is key to achieving gradient pore size self-assembly. The hydrolysis / condensation kinetics of the three precursors differ, and this difference can be controlled by adjusting the solution pH, temperature, water-to-alcohol ratio, and catalyst concentration to achieve layered growth and component gradient construction in the film thickness direction, in conjunction with the spatial distribution of the template agent.

[0086] Multi-level pore size construction employs a template-assisted method. The macroporous template agent is polystyrene microspheres with an average particle size of 200 nm and a particle size distribution coefficient of less than 0.05, used to construct the outer macroporous structure. The mesoporous template agent is hexadecyltrimethylammonium bromide with a critical micelle concentration of approximately 1 mmol / L, capable of self-assembling into columnar or layered mesoporous structures in a sol-gel system. The microporous template agent is tetraethylammonium hydroxide with a cationic size of approximately 0.8 nm, capable of forming nanoscale cavities in the oxide network, leaving microporous channels after heat treatment removal. In this application, for ease of description, the range of 2 nm to 5 nm is defined as small-sized mesopores (referred to as micropores), the range of 20 nm to 50 nm as medium-sized mesopores (referred to as mesopores), and larger than 50 nm as macropores. All template agents must be pre-dissolved at a specified temperature and ultrasonically dispersed before use to ensure uniform dispersion.

[0087] The ionic liquid selected is 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, with the molecular formula [EMIM][FSI]. Its room-temperature ionic conductivity is approximately 8 mS / cm to 12 mS / cm, and its electrochemical stability window is greater than 5.0 V. This ionic liquid was chosen based on its unique FSI. - The anionic structure promotes the formation of a dense and stable lithium fluoride-rich interfacial film, significantly reducing interfacial side reactions and impedance growth. The purity of the ionic liquid is not less than 99.9%, and the water content is strictly controlled below 50 ppm. It must be stored in a sealed glove box before use. In addition to [EMIM] and [FSI], other FSI-containing liquids may also be used in this application. - or TFSI - Anionic liquids, such as 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide and N-methyl-N-propylpyrrolidine bis(fluorosulfonyl)imide, can be used alone or in combination with [EMIM][FSI], but the FSI should be maintained. -The proportion of anions in the total anions is not less than 50% to maintain excellent film-forming properties.

[0088] The solvents and catalysts used in the preparation include anhydrous ethanol as the main solvent, with a purity of not less than 99.7% and a water content of less than 0.3%; deionized water as the water source required for the hydrolysis reaction, with a conductivity of less than 1 μS / cm; dilute hydrochloric acid solution (0.1 mol / L) as an acid catalyst to regulate the hydrolysis rate of the precursor; and ammonia solution (0.1 mol / L) as a base catalyst to promote the polycondensation reaction. The selection of solvents and catalysts and the control of their concentrations directly affect the kinetics of the sol-gel reaction, and thus determine the formation of the final pore structure.

[0089] The supporting materials required for battery fabrication include the following categories. The positive electrode active material uses NCM622 ternary material with the chemical formula LiNi. 0.6 Co 0.2 Mn 0.2 O2, with a particle size D50 of 8μm~12μm and a tap density of 2.2g / cm³. 3 ~2.4g / cm 3 The conductive agent used is Super P conductive carbon black, with a specific surface area of ​​approximately 60 m². 2 / g. Regarding the binder, polyacrylic acid is used as the binder for the negative electrode, with a molecular weight of approximately 250,000 g / mol. It can form hydrogen bonds with the hydroxyl groups on the silicon surface, providing good bonding strength and flexibility. Polyvinylidene fluoride is used as the binder for the positive electrode, with a molecular weight of approximately 600,000 g / mol. The current collector materials are 10 μm thick copper foil for the negative electrode and 15 μm thick aluminum foil for the positive electrode, with special surface treatment to enhance adhesion to the active material layer. The separator is a 20 μm thick polyolefin-based ceramic-coated separator, with a ceramic coating thickness of approximately 3 μm, providing additional thermal stability and mechanical strength. The electrolyte system uses 1 mol / L lithium bis(fluorosulfonyl)imide dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 3:4:3, with 2 wt% fluoroethylene carbonate added as a film-forming additive. All battery materials are commercially available from reputable suppliers, and humidity-sensitive materials are handled in glove boxes with dew points below -40°C.

[0090] The modified silicon particles were prepared using a rate-difference synergistic template method, and the specific process flow is as follows. First, a precursor mixture solution was prepared by accurately weighing tetraethyl orthosilicate, zirconium butoxide, and aluminum isopropoxide according to the target oxide ratio. Taking Example 1 as an example, the mass ratio of SiO2, ZrO2, and Al2O3 was 4:3:3, which translates to a precursor molar ratio of approximately 1.5:1.2:0.9. The weighed precursor was dissolved in anhydrous ethanol, with the total solution volume controlled at 200 mL. The mixture was magnetically stirred for 30 min at room temperature to ensure thorough mixing. Then, a pre-prepared template agent solution was added. This solution contained polystyrene microspheres, hexadecyltrimethylammonium bromide, and tetraethylammonium hydroxide. The amount of each template agent added was precisely calculated based on the target pore size and pore volume. After adding the template agent, stirring was continued for 10 min. Then, a deionized aqueous solution containing dilute hydrochloric acid was slowly added dropwise to initiate the hydrolysis reaction. The dropping rate was controlled at 0.5 mL / min, and the molar ratio of water to the total silicon-oxygen bonds in the precursor was approximately 2.5:1.

[0091] Simultaneously with the hydrolysis reaction, surface-cleaned nano-silicon powder was added to the above mixed solution. The amount of silicon powder added ensured that the final protective film accounted for 10%–15% of the total mass of the coated silicon particles. The entire system was continuously stirred in a 40°C water bath. During the reaction, the pH value was gradually adjusted to an alkaline range of 8.5–9.0 by adding dilute ammonia solution dropwise to promote the condensation reaction. Due to the significant differences in the hydrolysis rates of the three precursors, the oxide network formed on the surface of the silicon particles exhibited a layer-by-layer growth characteristic from the inside out. Combined with the spatial distribution of template agents of different sizes, a gradient pore structure was ultimately formed. Specifically, the template agent determined the pore size of each layer, while the difference in the hydrolysis rate of the precursors determined the enrichment order and layered distribution of different oxide components in the film thickness direction. The synergistic effect of both achieved the simultaneous construction of increasing pore size and component gradient from the inside out. The reaction time was controlled at 6 hours, during which the temperature and pH value needed to be kept stable.

[0092] After the reaction, the coated product was collected by centrifugation and washed three times with anhydrous ethanol to remove residual template agent and unreacted precursors, centrifuged after each wash. The washed wet gel-coated particles were pre-dried at 80°C for 2 hours and then transferred to a programmed temperature furnace for heat treatment. The heat treatment employed a segmented programmed temperature strategy: first, the temperature was increased to 200°C at a rate of 5°C / min and held for 2 hours, primarily to remove residual solvent and adsorbed moisture; then, the temperature was increased to 450°C at a rate of 2°C / min and held for 1 hour, during which the polystyrene microspheres and organic template agent began to decompose and volatilize; finally, the temperature was increased to 550°C at a rate of 1°C / min and held for 2-4 hours to promote oxide network solidification and remove template agent / organic residues. The heat treatment could be carried out in an inert atmosphere (nitrogen or argon) to reduce the risk of nano-silicon oxidation; when further reduction of organic residues was required, a short-term post-treatment in a low-temperature oxygen-containing atmosphere or solvent extraction / plasma treatment could be used as supplementary removal steps without significantly oxidizing the silicon matrix.

[0093] Ionic liquid backfilling is the final crucial step in protective film preparation. Heat-treated coated silicon particles are mixed with [EMIM][FSI] ionic liquids in a glove box according to a designed ratio. A vacuum impregnation method is used to ensure the ionic liquid fully fills the pore network of the protective film. Specifically, the mixture is placed in a vacuum drying oven and maintained at 60°C and a vacuum of less than 100 Pa for 6 hours. During this process, the vacuum environment promotes the expulsion of residual gas from the pores, and the ionic liquid gradually permeates into each level of pore driven by capillary action and concentration gradient. Due to the connectivity of the three-layer pore structure, the ionic liquid can gradually permeate from the outer macropores to the inner micropores, ultimately achieving uniform filling of the entire pore network. After impregnation, the particles are allowed to stand at room temperature under normal pressure for 12 hours to allow the ionic liquid distribution to reach equilibrium, resulting in a biomimetic multi-level pore protective film coated silicon particles filled with ionic liquid. These composite particles can be directly used for anode material preparation.

[0094] For the preparation of monolayer pore structures in the comparative examples, the process flow is basically the same as described above, with the main difference being the use of only a single type of template agent. Comparative Example 2 uses only polystyrene microspheres as a template agent to prepare a monolayer macroporous structure, Comparative Example 3 uses only hexadecyltrimethylammonium bromide to prepare a monolayer mesoporous structure, and Comparative Example 4 uses only tetraethylammonium hydroxide to prepare a monolayer microporous structure. Comparative Example 5 prepares a reverse gradient pore structure by changing the order of precursor addition and adjusting the reaction temperature and pH value change curves, so that the formed protective film exhibits a reverse gradient with decreasing pore size from the inside to the outside. Comparative Example 6 uses pure tetraethyl orthosilicate as the sole precursor to prepare a pure SiO2 protective film, maintaining a three-layer gradient pore structure but eliminating the synergistic effect of ternary oxides. The preparation of Comparative Example 7 is exactly the same as Example 1, except that [EMIM][FSI] is not added in the final ionic liquid backfilling step, leaving the pores in an empty state. Comparative Example 1 uses bare silicon particles without any protective film coating, directly used for anode preparation as a performance benchmark.

[0095] The battery in this application adopts a 3Ah~5Ah stacked soft-pack structure, and the positive electrode is LiNi. 0.6 Co 0.2 Mn 0.2 The O2 ternary material serves as the negative electrode, which is a silicon-carbon composite negative electrode. The positive electrode slurry formulation, by mass percentage, consists of 94% NCM622 active material, 3% Super P conductive carbon black, and 3% polyvinylidene fluoride binder. During slurry preparation, NCM622 powder, Super P, and PVDF are precisely weighed according to the above proportions and added to N-methylpyrrolidone solvent. The mixture is stirred at 1500 rpm for 2 hours using a planetary mixer, followed by vacuum degassing to remove air bubbles. The prepared positive electrode slurry is then uniformly coated onto a 15μm thick aluminum foil current collector using either roller coating or blade coating. The coated electrode is then pre-dried at 80℃ and deep-dried at 120℃. After drying, the electrode is compacted on a roller press, with the compaction density controlled at 3.2 g / cm³. 3 ~3.4g / cm 3 The surface density of a single-sided coating is 18 mg / cm³. 2 ~22mg / cm 2 The compacted positive electrode sheet is cut to the required size and dried in a vacuum environment at 120°C for 12 hours to remove residual moisture and solvent, and then transferred to a glove box for later use.

[0096] The negative electrode slurry formulation, by mass percentage, consists of 90% silicon-carbon composite active material (50% silicon particles with a protective film and 50% graphite), 2% Super P conductive carbon black, and 8% polyacrylic acid binder. During slurry preparation, the silicon-carbon composite powder and Super P are premixed in deionized water and stirred at low speed for 30 minutes using a planetary mixer to ensure thorough dispersion. Then, an aqueous solution of polyacrylic acid is added and stirring continues for 1 hour. Finally, a uniform slurry is obtained by vacuum degassing. The negative electrode slurry is coated onto a 10μm thick copper foil current collector using a scraping method. The coated electrode is then slowly dried at 60℃ to prevent cracking due to rapid water loss. After drying, it is compacted on a roller press, with the compaction density controlled at 1.4 g / cm³. 3 ~1.6g / cm 3 The surface density of a single-sided coating is 6 mg / cm³. 2 ~8mg / cm 2 The compacted negative electrode sheet is cut to the same size as the positive electrode sheet, dried in a vacuum environment at 110℃ for 8 hours, and then transferred to a glove box for later use.

[0097] Battery assembly is carried out in a glove box with a dew point below -40°C. Cut positive electrode sheets, negative electrode sheets, and ceramic-coated separators are stacked in the order of negative electrode-separator-positive electrode to form a single cell unit. Depending on the battery capacity design, multiple cell units are stacked, typically 10 to 15 units, to achieve a total capacity of 3Ah to 5Ah. After stacking, the entire stack is placed in a pre-prepared aluminum-plastic film soft-pack casing, and preliminarily sealed on three sides using a heat-sealing machine, leaving one side as the electrolyte injection port. Before electrolyte injection, the sealed stack is vacuum-baked at 80°C for 2 hours to ensure internal dryness. During electrolyte injection, electrolyte is precisely measured and slowly injected into the soft-pack through the injection port. The injection volume is calculated based on the total pore volume of the stack and wetting requirements, typically 3g to 4g of electrolyte per ampere-hour. After injection, the injection port is vacuum-sealed using a vacuum sealing machine to ensure no air residue remains inside the soft-pack.

[0098] The packaged battery cells need to undergo a formation process for activation. Formation is performed on a dedicated battery testing system. First, the cells are charged at 25°C at a 0.2C rate to the upper limit voltage of 4.2V. Then, constant voltage charging is applied until the current decays to 0.05C. Subsequently, the cells are discharged at a 0.2C rate to the lower limit voltage of 2.5V, completing the first charge-discharge cycle, and the coulombic efficiency of the first cycle is recorded. The main purpose of the first cycle is to form a stable solid electrolyte interface film, during which some lithium ions are consumed in an irreversible reaction. After formation, the cells are left to stand for 24 hours, and the voltage retention is checked to eliminate cells with abnormal self-discharge. Qualified cells that pass the screening are then used for subsequent performance testing. The entire battery manufacturing process strictly follows standardized operating procedures to ensure batch-to-batch consistency and data repeatability.

[0099] To systematically evaluate the overall performance of the silicon-carbon anode materials prepared in the various embodiments and comparative examples of this application, the following standardized tests were performed on all samples (as shown in Tables 2-1 and 2-2).

[0100] The first-week coulombic efficiency test was completed during the formation stage. At 25°C, the battery was charged at a constant current rate of 0.2C to the upper limit voltage of 4.2V, and then switched to constant voltage charging until the current decayed to 0.05C. Subsequently, it was discharged at a constant current rate of 0.2C to the lower limit voltage of 2.5V. The initial charge capacity and discharge capacity were recorded. The first-week coulombic efficiency is defined as the percentage of the initial discharge capacity to the initial charge capacity. This parameter reflects the degree of irreversible lithium loss in the first cycle and is an important indicator for evaluating the stability of the anode interface.

[0101] The room temperature cycling stability test was conducted at 25℃. The electrode was charged at a constant current rate of 0.5C to 4.2V, then charged at a constant voltage rate to 0.05C cutoff, and then discharged at a constant current rate of 0.5C to 2.5V. The cycle was repeated for 500 cycles or until the capacity decayed to 80% of the initial capacity. The discharge capacity and capacity retention rate were recorded at the 100th, 200th, and 500th cycles. The average coulombic efficiency throughout the cycle was also recorded. This test is the core indicator for evaluating the long-term cycling stability of the negative electrode.

[0102] High-temperature cycling stability testing was conducted at 45°C, with the same charge-discharge regime as normal temperature cycling. The discharge capacity and capacity retention rate were recorded at the 100th and 200th cycles. Cycling testing under high-temperature conditions can accelerate interfacial side reactions and structural degradation, and is an effective means of evaluating the high-temperature stability of protective films.

[0103] Rate performance testing was conducted at 25°C. The charging rate was fixed at 0.5C constant current and constant voltage charging, and the discharging rates were set sequentially to 0.2C, 0.5C, 1C, 2C, and 3C. Each rate was cycled 3 times, and the discharge capacity of the 3rd cycle was taken as the representative value at that rate. The capacity retention rate at each rate was calculated based on the discharge capacity at 0.2C rate. In particular, the capacity ratio of 3C rate to 0.2C rate was calculated as a key evaluation indicator. Rate performance reflects the ion transport capability and polarization degree of the negative electrode under rapid charge and discharge conditions.

[0104] Electrochemical impedance spectroscopy (EIS) was performed on a pouch cell at 50% state of charge using a two-electrode system at a test temperature of 25°C. The frequency range was 100 kHz to 0.01 Hz, and the AC voltage amplitude was 5 mV. Tests were conducted after the first cycle and after 200 cycles. Ohmic impedance Rs, solid electrolyte interfacial membrane impedance Rsei, and charge transfer impedance Rct were obtained through equivalent circuit fitting. All impedance values ​​are in milliohms (mΩ). The total impedance was calculated as the sum of the three values. The difference ΔRct between Rct after 200 cycles and that after the first cycle was calculated as a quantitative indicator of interfacial impedance growth. Impedance testing can quantitatively analyze the interfacial evolution process and charge transfer kinetics.

[0105] The volume expansion rate test is conducted by monitoring the change in electrode thickness. The initial thickness of the negative electrode sheet is measured before battery assembly. During the cycling process, the battery is disassembled and the thickness of the negative electrode sheet is measured after the 100th and 200th cycles, respectively. The expansion rate is defined as the percentage of the thickness increment to the initial thickness. Five different locations are selected for each measurement and the average value is taken to eliminate the influence of local non-uniformity. This test directly reflects the buffering effect of the protective film on the volume expansion of silicon.

[0106] For the key samples involved in structural characterization (9 samples in total: Example 1, Comparative Examples 2-7, Example 3, and Example 10), BET pore size distribution analysis was performed to verify the pore structure characteristics of the protective membrane. Before testing, the samples were degassed under vacuum at 120°C for 12 hours to remove adsorbed moisture and gas. Then, nitrogen adsorption-desorption isotherms were tested at liquid nitrogen temperature (77K), with a relative pressure range of 0.01–0.99. The mesopore size distribution was calculated using the BJH method, and the micropore size distribution was calculated using the DFT method. For macropores, it is recommended to supplement with mercury intrusion testing or obtain the characteristic pore size and pore area fraction of macropores through SEM image analysis. The peak pore size, pore volume, and percentage of total pore volume for micropores (2nm–5nm), mesopores (20nm–50nm), and macropores (>50nm) were recorded. The BET specific surface area and total pore volume were calculated. These parameters can quantitatively characterize the pore structure of the protective membrane and verify the rationality of the design.

[0107] ICP elemental analysis is used to verify the actual composition ratio of ternary oxides in the protective film. It is important to note that the ICP test targets the protective film material itself (the film material obtained through peeling or the precursor dry gel), not the entire coated silicon powder, because silicon nuclei in the powder would result in a Si content far exceeding the design value of the protective film. After acid dissolution, the elemental contents of Si, Zr, and Al are determined using inductively coupled plasma atomic emission spectrometry (ICP-AES) or mass spectrometry. The mass percentages of SiO2, ZrO2, and Al2O3 and their ratios are obtained through stoichiometric conversion. For samples where the film cannot be completely peeled off, the relative ratio of Zr and Al can be used as the primary verification basis, while the SiO2 ratio is calibrated based on the results of the initial sample or peelable samples.

[0108] The thickness of the protective film was obtained by observing the cross-sectional morphology of the coated silicon particles using a scanning electron microscope. At least 20 particles were randomly selected from each sample for measurement. The average thickness, standard deviation, and coefficient of variation were calculated, and the distribution range of the thickness was recorded. These statistical data can reflect the uniformity of the protective film thickness and the stability of the preparation process.

[0109] Interfacial shear strength testing was conducted using a dedicated shear force tester or tensile testing machine with specialized fixtures to measure the adhesion force between the protective film and silicon particles. Five parallel samples were tested for each sample, and the mean and standard deviation were calculated. This parameter is a direct indicator for evaluating the mechanical stability of the protective film and its adhesion performance to the silicon substrate. This test was performed only on four representative samples: Example 1, Comparative Example 1, Comparative Example 6, and Example 6.

[0110] The following analysis and discussion of the mechanisms of action and performance trends of each technical element are based on predicted / target value data. In practical applications, actual measured data should prevail (as shown in Tables 3-1, 3-2, 4-1~4-5, and 5-1~5-3). Specifically, it is divided into the following sections: 1) The decisive role of the three-layer gradient aperture structure The performance data clearly demonstrates the decisive influence of the three-layer gradient aperture structure on performance. Example 1, representing the complete technical solution, achieves a first-cycle coulombic efficiency of 87.5%, a capacity retention rate of 91.1% after 200 cycles at 25°C, a capacity retention rate of 86.3% after 500 cycles, a capacity ratio of 71.6% between 3C and 0.2C rates, an estimated charge transfer impedance increase of approximately 7.9 mΩ after 200 cycles, and an estimated volume expansion rate of approximately 26.5% after 200 cycles. This data showcases a good balance among multiple performance indicators.

[0111] The decisive role of the three-layer gradient pore structure in performance is fully demonstrated through a systematic comparison with the single-layer pore structure. Comparative Example 2, employing a single-layer macroporous structure, exhibited a capacity retention of approximately 76.6% after 200 cycles, a decrease of approximately 14.5 percentage points compared to Example 1, and a 3C rate capacity ratio of approximately 56.5%, a decrease of approximately 15.1 percentage points compared to Example 1. The main reason for this performance difference lies in the fact that while the single-layer macroporous structure can provide a certain buffer space for volume expansion, it lacks selective control over lithium-ion transport. The excessively large pore size leads to an excessively long diffusion path for lithium ions within the pores and a lack of effective interfacial reaction active sites. Furthermore, it cannot effectively prevent direct contact between the electrolyte and the silicon surface, potentially exacerbating interfacial side reactions and leading to the continuous growth of the solid electrolyte interfacial film. After 200 cycles, the Rct of Comparative Example 2 increased by approximately 28.3 mΩ, about 3.6 times that of Example 1, indicating that its interfacial impedance accumulation rate may be much faster than that of the three-layer gradient structure.

[0112] Comparative Example 3 employs a single-layer mesoporous structure, exhibiting a capacity retention of approximately 80.9% after 200 cycles and a 3C rate capacity ratio of approximately 63.2%. While this represents an improvement over Comparative Example 2, it remains significantly inferior to Example 1. The moderate size of the single-layer mesopores helps balance lithium-ion transport and interfacial reactions to some extent, thus improving rate performance and interfacial impedance growth compared to single-layer macropores. However, the mesopore size is still insufficient to effectively buffer the volume expansion of silicon. After 200 cycles, Comparative Example 3 showed a volume expansion rate of approximately 40.2%, about 13.7 percentage points higher than the 26.5% of Example 1. This indicates that the lack of stress buffering effect from the outer macropores may lead to the protective film bearing greater mechanical stress.

[0113] Comparative Example 4, employing a single-layer micropore structure, exhibited unique performance characteristics. Its first-cycle coulombic efficiency reached approximately 88.0%, slightly higher than Example 1. This is likely due to the high specific surface area and abundant interfacial active sites of the micropores, which facilitate the formation of a uniform solid electrolyte interfacial film. However, the 3C rate capability ratio of Comparative Example 4 was approximately 52.5%, a decrease of about 19.1 percentage points compared to Example 1, making it the worst rate performer among all samples. This result clearly reveals the main limitation of the single-layer micropore structure. While micropores can provide excellent lithium-ion selectivity and rapid interfacial charge transfer, their excessively small pore size can lead to severe transport impedance, especially at high current densities where lithium-ion diffusion in narrow channels becomes the main limiting factor for performance. The first-cycle Rct of Comparative Example 4 reached approximately 129.8 mΩ, about 2.9 times that of Example 1, and is expected to increase to 205.5 mΩ after 200 cycles. Furthermore, the single-layer micropore structure completely fails to buffer the volume expansion of silicon; the volume expansion rate of Comparative Example 4 after 200 cycles is approximately 40.3%, comparable to Comparative Example 3.

[0114] A systematic analysis of the three monolayer pore sizes reveals that while protective films with a single pore size may excel in one aspect, they inevitably have shortcomings in others, making it difficult to achieve synergistic optimization of stress buffering, ion transport regulation, and interface stability. The three-layer gradient pore size design employed in Example 1 integrates the advantages of different pore sizes: the outer macropores provide ample buffer space for volume expansion, the middle mesopores achieve kinetic balance in lithium-ion diffusion, and the inner micropores ensure highly selective interfacial transport and the formation of a uniform solid electrolyte interface film. The synergistic effect of the three pore sizes is key to achieving excellent overall performance.

[0115] 2) Importance of aperture gradient direction The importance of the pore size gradient direction is clearly demonstrated in Comparative Example 5. Comparative Example 5 employs a reverse gradient pore size design, i.e., a small outer pore, a mesopore middle layer, and a large inner pore. Although it also has a three-layer pore structure, its performance is significantly inferior to that of Example 1 with the forward gradient. The capacity retention rate of Comparative Example 5 after 200 cycles is approximately 78.3%, about 12.8 percentage points lower than Example 1, and its 3C rate capacity ratio is approximately 56.7%, about 14.9 percentage points lower than Example 1. This significant performance difference stems from the mismatch between the pore size gradient direction and functional requirements. In the reverse gradient structure, while the small outer pores can provide high selective transport, their narrow channels can severely hinder the rapid transport of lithium ions from the electrolyte to the silicon surface, especially at high rates, becoming a bottleneck. Simultaneously, although the large inner pores provide some buffer space, the lack of mechanical constraint from the outer layer means that the protective film may bulge or even crack during silicon expansion, resulting in a loss of structural integrity. After 200 cycles, the Rct of Comparative Example 5 increased by approximately 30.7 mΩ, significantly higher than that of Example 1. This comparison fully demonstrates the scientific validity and necessity of the "increased aperture from the inside out" design of this application, which ensures that each layer is in the most suitable position to perform its function, achieving the best match between structure and function.

[0116] 3) The necessity of ternary oxide synergistic systems The necessity of the ternary oxide synergistic system is strongly demonstrated by Comparative Example 6. Comparative Example 6 uses pure SiO2 as the protective film material, maintaining the three-layer gradient pore structure but eliminating the synergistic effect of ZrO2 and Al2O3. The data shows that the capacity retention rate of Comparative Example 6 after 200 cycles is expected to be approximately 70.6%, a decrease of about 20.5 percentage points compared to Example 1, and the capacity retention rate after 500 cycles is expected to decrease to 58.4%, exhibiting a severe long-term cycling degradation trend. This degradation may be due to the mismatch in thermal expansion coefficients between pure SiO2 and the silicon substrate; the thermal expansion coefficient of SiO2 is approximately 0.5 × 10⁻⁶. -6 / ℃, while the coefficient of thermal expansion of nano-silicon is approximately 2.6×10. -6The temperature difference between the two is more than five times. During cycling, the repeated expansion and contraction of silicon may generate significant stress concentration in the SiO2 protective film, leading to cracks or even delamination at the interface between the protective film and the silicon substrate. Data on interfacial shear strength supports this analysis; the average shear strength of Comparative Example 6 is approximately 5.8 MPa, which is not only lower than the technical requirement of 8 MPa but also far lower than the 12.8 MPa of Example 1, indicating that the adhesion between the pure SiO2 protective film and the silicon substrate may be severely insufficient.

[0117] Furthermore, Comparative Example 6 performed particularly poorly in high-temperature cycling, with an estimated capacity retention of approximately 55.2% after 200 cycles at 45°C, about 27.1 percentage points lower than the 82.3% of Example 1. This phenomenon suggests that the interfacial stability problem of pure SiO2 protective films may be more prominent at high temperatures, possibly due to the accelerated interfacial side reactions and structural degradation processes caused by high temperatures. In contrast, the SiO2-ZrO2-Al2O3 ternary synergistic system used in Example 1 can achieve optimized matching of thermal expansion coefficients through reasonable component ratios. The addition of ZrO2 is expected to provide excellent mechanical strength and toughness, while the addition of Al2O3 can enhance the chemical bonding with the silicon surface and regulate lithium-ion transport. The synergistic effect of the three oxides is expected not only to improve thermal matching but also to enhance the mechanical stability and interfacial bonding strength of the protective film, enabling the protective film to withstand repeated expansion and contraction of silicon while maintaining structural integrity. Example 6 further verified the optimization space of the component ratio. When the SiO2 content is increased to 50%, the interfacial shear strength can be further improved to 14.2 MPa. However, excessive SiO2 content may lead to a relative decrease in mechanical support capacity. Therefore, the 4:3:3 ratio used in Example 1 represents the best balance point of comprehensive performance.

[0118] 4) Key contributions of ionic liquid filling The contribution of ionic liquid filling to the protective film performance is clearly demonstrated in Comparative Example 7. The only difference between Comparative Example 7 and Example 1 is that the protective film pores are not filled with [EMIM][FSI] ionic liquid, while its three-layer gradient pore structure and ternary oxide composition are the same as those of Example 1. In terms of room temperature performance, the capacity retention rate of Comparative Example 7 after 200 cycles is approximately 80.7%, which is about 10.4 percentage points lower than the 91.1% of Example 1. This indicates that even with excellent pore structure and oxide composition, the lack of ionic liquid filling is expected to lead to a significant performance degradation. However, the effect of the ionic liquid is more pronounced under high-temperature conditions. The capacity retention rate of Comparative Example 7 after 200 cycles at 45°C is expected to be approximately 57.4%, which is about 24.9 percentage points lower than the 82.3% of Example 1. This significant difference reveals the potentially crucial role of ionic liquids in high-temperature interfacial stability.

[0119] In-depth analysis reveals that ionic liquids likely play a multifaceted role in protective films. Firstly, ionic liquids filling pores significantly improve the flexibility and mechanical compliance of the protective film, allowing it to better adapt to volume changes in silicon without cracking. Secondly, ionic liquids, particularly FSI in [EMIM][FSI], [followed by specific chemical structures]. - Anions can promote the formation of a stable, lithium fluoride-rich solid electrolyte interfacial film on the silicon surface and the inner surface of the protective film. This interfacial film may have higher chemical stability and lower interfacial impedance compared to the interfacial film formed by conventional carbonate electrolytes, especially at high temperatures, where it can effectively suppress persistent interfacial side reactions. Impedance data support this mechanism; the expected increase in Rct after 200 cycles in Comparative Example 7 is 28.7 mΩ, significantly higher than the 7.9 mΩ in Example 1, indicating that the lack of ionic liquid filling may lead to a rapid increase in interfacial impedance and a decrease in interfacial stability. Third, the presence of ionic liquid can improve the ion transport environment in the pores of the protective film and may lower the activation energy of ion transport. Although the rate performance of Comparative Example 7 (60.5%) is not as good as that of Example 1 (71.6%), it is still significantly better than that of the monolayer pore structure, indicating that the pore size gradient still plays a role. However, the lack of ionic liquid may limit its full potential.

[0120] 5) Feasibility of two-layer gradient aperture structure The feasibility of the two-layer gradient pore structure was verified through Example 2. Example 2 employs a two-layer structure: an outer layer with macropores (200±20) nm and an inner layer with continuously distributed meso-micropores (3 nm~50 nm). Other technical elements are the same as in Example 1. Example 2 exhibits a capacity retention rate of approximately 90.3% after 200 cycles, approximately 84.2% after 500 cycles, and a 3C rate-capacity ratio of approximately 70.7%. These performance indicators are slightly lower than those of Example 1, but the difference is small, only 1 to 2 percentage points. This result indicates that the two-layer gradient pore structure can achieve basic synergy between stress buffering and ion transport. Although it is not as precise as the three-layer structure in terms of functional layering, it can already meet most application requirements. From the perspective of patent protection scope, the inclusion of the two-layer structure expands the technical solution coverage of this application, providing selection space for application scenarios with different performance requirements. It is worth noting that the total thickness of the protective film in Example 2 is about 80 nm, which is thinner than the 100 nm in Example 1. This means that a higher proportion of active material can be provided at the same coverage rate, which may have certain advantages in applications with strict requirements for energy density.

[0121] Optimization space for process parameters The process parameter optimization experiments demonstrated the robustness and industrialization potential of the technology presented in this application. Example 3 investigated the effect of ionic liquid content. When the ionic liquid content reached the upper limit of 40% (corresponding to an oxide content of 60%), the capacity retention rate after 200 cycles was approximately 89.8%, very close to the 91.1% of Example 1. However, the high-temperature cycling performance decreased slightly, with the capacity retention rate after 200 cycles at 45°C expected to be approximately 81.0%, about 1.3 percentage points lower than the 82.3% of Example 1. This indicates that while an excessively high ionic liquid content may further improve flexibility, it may lead to a relative deficiency in the mechanical strength of the protective film, resulting in a slight decrease in structural stability at high temperatures. Example 4 investigated the lower limit of ionic liquid content. When the ionic liquid content was 15% (corresponding to an oxide content of 85%), the capacity retention rate after 200 cycles was approximately 89.6%, and the high-temperature cycling performance also decreased slightly accordingly, with the capacity retention rate after 200 cycles at 45°C expected to be approximately 80.6%. These data show that good performance can be obtained with ionic liquid content in a wide range of 15% to 40%, but there is an optimal range, and the 25% used in Example 1 is close to this optimal point.

[0122] Examples 5 and 6 explored the optimization potential of the ternary oxide ratio. In Example 5, the SiO2 content was reduced to the lower limit of 35% (corresponding to 32.5% each of ZrO2 and Al2O3). While the interfacial bonding performance decreased slightly, the cycling performance remained at a high level, with an expected capacity retention of approximately 90.0% after 200 cycles. In Example 6, the SiO2 content was increased to the upper limit of 50% (corresponding to 25% each of ZrO2 and Al2O3). The interfacial shear strength increased to 14.2 MPa, demonstrating the significant contribution of SiO2 to interfacial bonding. However, the cycling performance was comparable to Example 1, indicating that excessively high SiO2 content may not further improve cycling stability. In Example 7, the ZrO2 content was increased to 40%, focusing on enhancing the mechanical support function. Its high-temperature cycling performance was expected to be excellent, with an expected capacity retention of approximately 81.8% after 200 cycles at 45°C, slightly higher than Example 1, demonstrating the potential special role of ZrO2 in high-temperature stability. These parameter optimization experiments not only verified the functional division of each component, but also demonstrated the flexibility of this application in terms of formulation adjustment, providing a basis for customized development for different application needs.

[0123] Examples 8 and 9 investigated the effect of outer layer macropore size on performance. In Example 8, the macropore size was set at the lower limit (150±15) nm, resulting in a slight decrease in capacity retention after 200 cycles to approximately 90.2%, and a slight increase in volume expansion rate. This indicates that while smaller macropore sizes can still provide buffering, the buffering capacity is relatively insufficient. In Example 9, the macropore size was increased to the upper limit (250±20) nm, achieving performance comparable to Example 1, but with a corresponding increase in protective film thickness. In practical applications, a balance needs to be struck between buffering effect and energy density. Example 10 verified the effect of hydrolysis rate difference. When the rate difference decreased to the lower limit (Si, Zr, Al = 1.5:1.0:0.75), although a gradient pore structure could still be formed, the clarity of pore layering might decrease. This was observed in the BET test, where the broadening and overlap of pore peaks in each layer were increased. Correspondingly, the capacity retention after 200 cycles decreased to approximately 89.8%, demonstrating the importance of an appropriate hydrolysis rate difference for forming a clear gradient pore structure.

[0124] 6) Validation of structural characterization data The structural characterization data provides direct structural evidence for the aforementioned performance differences. BET test results show that Example 1 likely exhibits a clear three-peak pore size distribution: a peak size of approximately 3.5 nm for small pores, approximately 35 nm for mesopores, and approximately 200 nm for macropores. The estimated pore volume percentages for these three types of pores are approximately 14.3%, 33.4%, and 52.3%, respectively, with a total estimated pore volume of approximately 0.335 cm³. 3 / g, the BET specific surface area is estimated to be approximately 185.3m². 2 / g. This clearly layered and rationally proportioned pore structure is the structural basis for achieving superior performance. In contrast, Comparative Example 2 only has a single peak in the macropore region, and its specific surface area may drop to approximately 45.2 m². 2 / g; Comparative Example 3 is expected to have a peak only in the mesoporous region, with a specific surface area of ​​approximately 165.8 m². 2 / g; Comparative Example 4 is expected to have a peak only in the pore region, with a specific surface area potentially as high as approximately 425.7 m². 2 / g, but the total pore volume is estimated to be only about 0.192cm³. 3 / g. Comparative Example 5 also exhibits a trimodal distribution, but the peak order is reversed compared to Example 1, and the transition regions between peaks may be more blurred, reflecting the inadequacy of the reverse gradient structure in terms of pore size stratification. The pore size distribution of Comparative Example 6 is similar to that of Example 1, demonstrating that a single precursor can still form gradient pores through template synergy, but its performance difference stems from oxide composition rather than pore size structure.

[0125] ICP elemental analysis results verified the actual proportions of the ternary oxides in the protective film. Test results for Example 1 showed a Si content of approximately 18.5%, a Zr content of approximately 22.4%, and an Al content of approximately 15.8%. Converted to oxide mass percentages, this equates to approximately 39.6% SiO2, 30.2% ZrO2, and 29.9% Al2O3. The actual proportions were expected to be approximately 4:3:3, highly consistent with the designed proportions. The proportions of other samples containing ternary oxides were also within the theoretical range, with a deviation expected to be less than ±0.5%, demonstrating the repeatability and controllability of the preparation process. Test results for Comparative Example 6 showed a Si content of approximately 46.7%, and zero Zr and Al contents. Converted, this equates to approximately 100% SiO2, confirming its pure silicon oxide composition. SEM statistical results of the protective film thickness showed that the average thickness of Example 1 was expected to be approximately 98 nm, with a standard deviation of approximately 12 nm and a coefficient of variation of approximately 12.2%. The thickness distribution was expected to be within the range of 78 nm to 118 nm. This uniformity in thickness indicates a stable and reliable preparation process. The thickness of the single-layer pore size comparative examples 2 to 4 is expected to be approximately 58 nm, the thickness of the two-layer structure example 2 is expected to be approximately 80 nm, and the thickness of the three-layer structure sample is expected to be in the range of 95 nm to 102 nm. These data are consistent with the theoretical design.

[0126] 7) Summary of Technological Advantages Based on all predicted / target value data and structural characterization results, the biomimetic multi-level pore size silicon anode surface protective film technology proposed in this application exhibits significant technical advantages and innovative value. The three-layer gradient pore structure, through the volume expansion buffering of the outer macropores, the ion diffusion regulation of the middle mesopores, and the high selective transport of the inner micropores, achieves synergistic optimization of stress management, transport kinetics, and interface stability. This multi-scale pore network design, biomimetic to sponge spicules, embodies the concept of drawing inspiration from natural structures and applying it to engineering practice. The ternary oxide synergistic system, through the interfacial bonding of SiO2, the mechanical support of ZrO2, and the transport regulation of Al2O3, is expected to solve the inherent defects of single oxide materials in terms of thermal matching, mechanical strength, and interface stability, enabling the protective film to maintain structural integrity during long-term cycling. The ionic liquid pore filling, especially the introduction of [EMIM][FSI], not only enhances the flexibility and mechanical compliance of the protective film, but more importantly, through FSI... - The unique film-forming mechanism of anions is expected to significantly improve interfacial chemical stability, especially under high-temperature conditions.

[0127] From an industrial application perspective, the technology presented in this application possesses excellent operability and economic viability. Although the rate difference synergistic template method involves multiple precursors and template agents, the preparation process is simple, requiring no complex multi-step coating or high-temperature, high-pressure treatment, making it suitable for large-scale production. The process parameter window is wide, with key parameters such as filler content, oxide ratio, and ionic liquid content achieving good performance within a broad range, reducing the difficulty of quality control in industrial production. All raw materials used are commercially available products, ensuring cost control and environmental friendliness. More importantly, the protective film preparation and silicon particle coating are integrated, allowing the resulting coated silicon particles to be directly used in anode preparation, exhibiting good compatibility with existing battery manufacturing processes and requiring no major modifications to the production line. These characteristics make the technology presented in this application not only academically innovative but also possess a realistic foundation for practical application, providing a feasible technical route to solve the cycle stability problem of silicon anodes and potentially promoting the practical application of high-energy-density lithium-ion batteries.

[0128] Table 1-1

[0129] Table 1-2

[0130] Table 1-3

[0131] Table 2-1

[0132] Table 2-2

[0133] Table 3-1

[0134] Table 3-2

[0135] Table 4-1

[0136] Table 4-2

[0137] Table 4-3

[0138] Table 4-4

[0139] Table 4-5

[0140] Table 5-1

[0141] Table 5-2

[0142] Table 5-3

[0143] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A battery cell, characterized in that, include: The housing and the positive electrode, the separator, the negative electrode and the electrolyte located within the housing, wherein the separator is located between the positive electrode and the negative electrode; The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer located on the surface of the negative electrode current collector. The negative electrode material layer includes modified silicon particles. The modified silicon particles include silicon particles and a protective layer on the surface of the silicon particles. The protective layer includes a first protective layer and a second protective layer stacked sequentially from the inside to the outside. The material of the first protective layer includes at least one of silicon oxide, zirconium oxide, and aluminum oxide. The material of the second protective layer includes at least one of silicon oxide, zirconium oxide, and aluminum oxide. Both the first protective layer and the second protective layer have pores, and the pore size of the pores in the first protective layer is smaller than the pore size of the pores in the second protective layer. At least one of the pores in the first protective layer and the pores in the second protective layer is filled with an ionic liquid.

2. The battery cell according to claim 1, characterized in that, The silicon oxide accounts for 35wt% to 50wt% of the total mass of the protective layer, the zirconium oxide accounts for 25wt% to 40wt% of the total mass of the protective layer, and the aluminum oxide accounts for 25wt% to 40wt% of the total mass of the protective layer.

3. The battery cell according to claim 1, characterized in that, The pore size of the first protective layer is in the range of 2nm to 50nm; and / or the pore size of the second protective layer is in the range of 150nm to 250nm.

4. The battery cell according to claim 1, characterized in that, The protective layer further includes a third protective layer, which is located on the surface of the second protective layer away from the first protective layer, and the pore size of the third protective layer is larger than that of the second protective layer.

5. The battery cell according to claim 4, characterized in that, The pore size range of the first protective layer is 2nm to 5nm; the pore size range of the second protective layer is 20nm to 50nm; and the pore size range of the third protective layer is 150nm to 250nm.

6. The battery cell according to claim 1, characterized in that, The cation of the ionic liquid is selected from one or more of imidazolium, pyrrolidineium, and piperidinium, and the anion is selected from FSI. - Or TFSI - .

7. The battery cell according to claim 1, characterized in that, The ionic liquid also includes a silane coupling agent.

8. The battery cell according to claim 7, characterized in that, The mass of the silane coupling agent is 0.5wt% to 3wt% of the total mass of the protective layer.

9. The battery cell according to claim 1, characterized in that, The total thickness of the protective layer is 30nm~300nm.

10. The battery cell according to claim 1, characterized in that, The silicon particles have a particle size of 100nm to 300nm.

11. A method for manufacturing a single battery cell, characterized in that, include: Silicon particles are provided, and the silicon particles are cleaned and activated. A protective layer is formed on the surface of the silicon particles. The protective layer includes a first protective layer and a second protective layer stacked sequentially from the inside to the outside. The materials of the first protective layer and the second protective layer both include silicon oxide, zirconium oxide and aluminum oxide, and the pore size of the first protective layer is smaller than that of the second protective layer. Ionic liquid is filled into the pores of the first protective layer and the second protective layer to obtain modified silicon particles; A negative electrode active material is prepared, wherein the negative electrode active material comprises the modified silicon particles, a conductive agent, and a binder; The negative electrode active material is coated onto the surface of the negative electrode current collector and dried to obtain a negative electrode sheet; The positive electrode, separator, and negative electrode are stacked in sequence, then stacked or wound into a housing, and electrolyte is injected into the housing. After formation, a single battery cell is obtained.

12. The method for manufacturing a single battery cell according to claim 11, characterized in that, Forming the protective layer on the surface of the silicon particles includes: The silicon source, zirconium source, and aluminum source are added to the solvent and mixed, and then the first template agent and the second template agent are added. Add a dilute deionized aqueous solution of hydrochloric acid dropwise to the mixed solution, and then add the silicon particles; Increase the temperature and add dilute ammonia to adjust the pH to 8.5-9; After the reaction is complete, the particulate matter is collected by centrifugation. The particles are calcined at 550°C to 580°C to remove the first template agent and the second template agent, resulting in silicon particles with the protective layer. The positions occupied by the first template agent form pores in the first protective layer, and the positions occupied by the second template agent form pores in the second protective layer.

13. The method for manufacturing a single battery cell according to claim 12, characterized in that, The first template agent is selected from hexadecyltrimethylammonium bromide, Pluronic F127, tetramethylammonium hydroxide, or tetraethylammonium hydroxide; the second template agent is selected from polystyrene microspheres.

14. The method for manufacturing a single battery cell according to claim 12, characterized in that, The protective layer further includes a third protective layer, which is located on the surface of the second protective layer away from the first protective layer, and the pore size of the third protective layer is larger than that of the second protective layer; a third template agent is added at the same time as the first template agent and the second template agent, wherein the first template agent is selected from hexadecyltrimethylammonium bromide or Pluronic F127, the second template agent is selected from tetramethylammonium hydroxide or tetraethylammonium hydroxide, and the third template agent is selected from polystyrene microspheres, and the positions occupied by the third template agent after calcination form the pores of the third protective layer.

15. A battery device, characterized in that, The battery device includes a battery cell manufactured by the manufacturing method of the battery cell as described in any one of claims 1 to 10 or the battery cell as described in any one of claims 11 to 14, and the battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

16. An electrical appliance, characterized in that, The electrical device includes the battery device as described in claim 15, the battery device being used to provide electrical energy.

17. An energy storage device, characterized in that, The energy storage device includes the battery device as described in claim 15, the battery device being used to store electrical energy.

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