Solid-state secondary battery, preparation method thereof, energy storage system and electric device

Abstract

The application relates to the field of batteries, and provides a solid-state secondary battery, a preparation method thereof, an energy storage system and an electric device. The preparation method comprises the following steps: preparing a ceramic aerosol, wherein the ceramic aerosol comprises inorganic ceramic oxide particles and polyimide particles; providing a substrate layer, and spraying the ceramic aerosol to at least one side of the substrate layer; performing heat treatment on the substrate layer, removing the polyimide particles, and converting the remaining inorganic ceramic oxide particles into a plurality of branches, wherein gaps exist between adjacent branches, and the branches are located on at least one side of the substrate layer; coating a coating slurry on one side of the substrate layer, and the coating slurry also flows into the gaps; performing a drying treatment, converting the coating slurry into an active layer, and combining the substrate layer and the branches to form a solid-state electrolyte; preparing a positive electrode sheet and a negative electrode sheet, and the preparation steps of at least one of the positive electrode sheet and the negative electrode sheet comprise the following steps: providing a current collector, and locating the active layer between the current collector and the substrate layer; and packaging to obtain the solid-state secondary battery.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a solid-state secondary battery and a preparation method thereof, an energy storage system, and electrical equipment. Background Art

[0002] Lithium secondary batteries are currently the main chemical power source system for various application scenarios such as power and energy storage. They have obvious advantages in terms of specific energy, service life, cost-effectiveness, etc. However, the contradiction between their specific energy and safety and the constraints of lithium resources have triggered a boom in the research and development of various new secondary batteries, among which solid-state lithium batteries and sodium batteries have become the most powerful competitors to current lithium-ion batteries.

[0003] Solid-state electrolytes can fundamentally improve the safety of secondary batteries and effectively increase their energy density. Electrode materials must meet multi-faceted requirements for chemical, mechanical, thermal, and electrochemical compatibility with the electrolyte. Battery performance can be improved and optimized through modifications to the electrode active material, electrolyte, and interface. However, current solid-state secondary batteries also face some challenges in their application, such as poor solid-solid interface contact between the electrolyte and active material, which affects battery internal resistance and other characteristics. Summary of the Invention

[0004] The embodiments of the present application provide a solid-state secondary battery and a preparation method thereof, an energy storage system, and an electrical device, which are at least beneficial for improving the problem of poor solid-solid interface contact between the electrolyte and the active material in the solid-state secondary battery.

[0005] According to some embodiments of the present application, on one hand, the embodiments of the present application provide a method for preparing a solid-state secondary battery, comprising: forming a solid-state electrolyte, including: preparing a ceramic aerosol, wherein the ceramic aerosol includes inorganic ceramic oxide particles and polyimide particles; providing a substrate layer, and spraying the ceramic aerosol onto at least one side of the substrate layer; heat-treating the substrate layer to remove the polyimide particles, and converting the remaining inorganic ceramic oxide particles into a plurality of branches, wherein adjacent branches have gaps between them, and the branches are located on at least one side of the substrate layer; preparing a coating slurry; The coating slurry is coated on one side of the substrate layer, and the coating slurry also flows into the gap; a drying treatment is performed, and the coating slurry is converted into an active layer, and the substrate layer and the branches together constitute the solid electrolyte; a positive electrode sheet and a negative electrode sheet are prepared, and the preparation steps of at least one of the positive electrode sheet and the negative electrode sheet include: providing a current collector, and the active layer is located between the current collector and the substrate layer; the negative electrode sheet, the solid electrolyte and the positive electrode sheet are stacked and hot-pressed in sequence to obtain a bare battery cell, and the bare battery cell is placed in a battery shell, and then packaged to obtain a solid-state secondary battery.

[0006] In some embodiments, the branches have holes, and the coating slurry also flows into the holes.

[0007] In some embodiments, the method further comprises, before the drying treatment, an ultrasonic treatment for filling the holes with the coating slurry, the ultrasonic treatment being performed for 3-15 minutes at a frequency of 20 kHz-5 MHz.

[0008] In some embodiments, the coating slurry comprises a dispersion solution comprising a wetting aid for flowing the coating slurry into the holes.

[0009] In some embodiments, in the step of preparing the ceramic aerosol, the volume ratio of the inorganic ceramic oxide particles to the polyimide particles is 1:(1-10), and the process parameters of the heat treatment include a reaction temperature of 500-1000°C, a calcination time of 0.8-1.2 hours, and a purging rate of the purging gas of 0.5-3 L / min.

[0010] In some embodiments, the coating slurry comprises an active material, and the surface of the active material is coated with Ga-LLZO, and the process steps of forming the active material include: uniformly stirring Ga-LLZO particles, active particles, and a solution to form a first mixed solution; drying the first mixed solution to form a first precursor; calcining the first precursor to form the active material, and the mass ratio of Ga-LLZO particles to active particles is (0.5-2 wt%):(8-9.5 wt%).

[0011] In some embodiments, the process steps of forming the coating slurry include: uniformly stirring an active material, nano inorganic ceramic oxide particles, a conductive agent, a binder, and a dispersion solution to obtain a second mixed solution; and high-speed dispersing the second mixed solution under negative pressure for 4-6 hours to obtain the coating slurry, and the viscosity of the coating slurry ranges from 5000 mPa·s to 20000 mPa·s, and the ratio of the active material, the nano inorganic ceramic oxide particles, the conductive agent, and the binder is (73-93 wt%):(5-18 wt%):(0.6-4.5 wt%):(1.4-4.5 wt%).

[0012] In some embodiments, the coating slurry includes an active material, which is graphite; after forming the solid electrolyte, the method further includes: uniformly stirring bis(fluorosulfonyl)imide lithium salt, poly(ethylene glycol) methacrylate, polyethylene glycol dimethacrylate, a photoinitiator, graphite and conductive carbon black to obtain a solidified liquid; immersing the solid electrolyte in the solidified liquid, and performing a solidification treatment on the solid electrolyte having the solidified liquid; wherein the mass ratio of bis(fluorosulfonyl)imide lithium salt: poly(ethylene glycol) methacrylate: polyethylene glycol dimethacrylate: photoinitiator: graphite: conductive carbon black is (35wt%~55wt%): (30wt%~50wt%): (1wt%~7.5wt%): (1.5wt%~4.5wt%): (2wt%~7wt%): (1wt%~3wt%).

[0013] In some embodiments, the current collector is a positive electrode current collector, and the process steps for preparing the positive electrode sheet include: providing a positive electrode current collector, the positive electrode current collector is located on the surface of the active layer, hot pressing the solid electrolyte and the positive electrode current collector, and the active layer and the positive electrode current collector constitute the positive electrode sheet.

[0014] According to some embodiments of the present application, another aspect of the embodiments of the present application provides a solid-state secondary battery, comprising: a battery shell having a cavity therein; a bare cell, wherein the bare cell is located in the cavity; the bare cell comprises a stacked positive electrode sheet, a solid electrolyte and a negative electrode sheet, wherein the solid electrolyte comprises: a substrate layer and a plurality of branches, wherein adjacent branches have gaps therebetween, and the branches are located on at least one side of the substrate layer; an active layer, wherein the active layer is located on the surface of the substrate layer and in the gap; the active layer is located between the substrate layer and the positive electrode current collector, and / or the active layer is located between the substrate layer and the negative electrode current collector.

[0015] In some embodiments, the branches have holes, and a portion of the active layer is embedded in the holes.

[0016] In some embodiments, the active layer includes a Ga-LLZO-coated active material.

[0017] According to some embodiments of the present application, another aspect of the embodiments of the present application provides an energy storage system, including: a secondary battery prepared by the method for preparing a solid-state secondary battery as described in any one of the above embodiments or a solid-state secondary battery as described in the above embodiments.

[0018] According to some embodiments of the present application, on the other hand, embodiments of the present application provide an electrical device, including: a solid-state secondary battery prepared by the secondary battery preparation method as described in any of the above embodiments, a solid-state secondary battery as described in the above embodiments, or an energy storage system as described in the above embodiments.

[0019] The technical solution provided by the embodiments of the present application has at least the following advantages:

[0020] The solid-state secondary battery provided in the embodiment of the present application is prepared by preparing a solid electrolyte, and the surface of the solid electrolyte has a plurality of branches, and the plurality of branches are located between the positive electrode current collector and the substrate layer, and / or the plurality of branches are located between the negative electrode current collector and the substrate layer, so that the positive electrode active layer of the positive electrode sheet can be staggered and interlocked with the solid electrolyte, and / or the negative electrode active layer of the negative electrode sheet can be staggered and interlocked with the solid electrolyte, thereby increasing the contact area and reducing the internal resistance of the battery. Secondly, an aerosol process is used to form branches on the surface of the substrate layer, and an active layer is subsequently formed so that the active layer is located in the gaps between the branches. The active layer can not only serve as a positive electrode active layer / negative electrode active layer, but the active layer can also serve as a contact enhancement layer, thereby improving the contact performance, and in the subsequent hot pressing step, a close interface contact is formed between the solid electrolyte layer and the positive electrode sheet and the negative electrode sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] One or more embodiments are exemplified by the figures in the corresponding drawings. These exemplified descriptions do not constitute a limitation on the embodiments. Unless otherwise stated, the figures in the drawings do not constitute a scale limitation. In order to more clearly illustrate the embodiments of the present application or the technical solutions in the traditional technology, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 A flowchart corresponding to a method for preparing a solid-state secondary battery provided in one embodiment of the present application;

[0023] Figure 2 A schematic diagram of a first structure of a solid-state secondary battery provided in one embodiment of the present application;

[0024] Figure 3 A top view of a solid electrolyte in a solid-state secondary battery provided in one embodiment of the present application;

[0025] Figure 4 A second structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application;

[0026] Figure 5A third structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application;

[0027] Figure 6 A fourth structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application;

[0028] Figure 7 A fifth structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application;

[0029] Figure 8 A sixth structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application;

[0030] Figure 9 A seventh structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application;

[0031] Figure 10 This is a schematic diagram of an eighth structure of a solid-state secondary battery provided in one embodiment of the present application;

[0032] Figure 11 This is a ninth structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application;

[0033] Figure 12 This is a tenth structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application;

[0034] Figure 13 This is an eleventh structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application.

[0035] Explanation of reference numerals: 1, positive electrode sheet; 2, negative electrode sheet; 110, branches; 100, substrate layer; 101, active layer; 102, secondary sphere aggregate; 103, Ga-LLZO-coated active material; 104, PEG-based polymer network; 105, graphite / carbon black conductive path;

[0036] 210, array pillars; 200, substrate layer; 201, active layer; 202, secondary sphere aggregates; 203, Ga-LLZO-coated active material; 204, PEG-based polymer network; 205, graphite / carbon black conductive path;

[0037] 300, substrate layer; 301, active layer; 302, secondary sphere aggregates; 303, Ga-LLZO-coated active material; 304, PEG-based polymer network; 305, graphite / carbon black conductive path. DETAILED DESCRIPTION

[0038] As can be seen from the background art, current solid-state secondary batteries have problems such as poor solid-solid interface contact between the electrolyte and the active material, which affects characteristics such as the battery's internal resistance.

[0039] The solid-state secondary battery provided in the embodiments of the present application is prepared by preparing a solid electrolyte, and the surface of the solid electrolyte has multiple branches, and the multiple branches are located between the positive electrode sheet and the substrate layer, and / or the multiple branches are located between the negative electrode sheet and the substrate layer, so that the positive electrode active layer of the positive electrode sheet can be interlaced and interlocked with the solid electrolyte, and the negative electrode active layer of the negative electrode sheet can be interlaced and interlocked with the solid electrolyte, thereby increasing the contact area and reducing the internal resistance of the battery. Secondly, an aerosol process is used to form branches, so that branches are formed on the surface of the substrate layer, and then an active layer is formed, so that the active layer is located in the gaps between the branches. The active layer can not only serve as the positive electrode active layer / negative electrode active layer, but also as a contact enhancement layer, thereby improving contact performance, and in the subsequent rolling step, a close interface contact is formed between the solid electrolyte layer and the positive electrode sheet and the negative electrode sheet.

[0040] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0041] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0042] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0043] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0044] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0045] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0046] In the accompanying drawings corresponding to the embodiments of the present application, the thickness and area of ​​the layers are exaggerated for better understanding and ease of description. When describing a component (such as a layer, film, region, or substrate) as being on another component or on the surface of another component, the component may be "directly" located on the surface of the other component, or a third component may be present between the two components. Conversely, when describing a component as being on the surface of another component or as being formed or provided on the surface of a component, it means that there is no third component between the two components. In addition, when describing a component as being "substantially" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0047] In the description of the embodiments of this application, when a component "includes" another component, unless otherwise specified, other components are not excluded, and other components may be further included. In addition, when a component such as a layer, film, region, or plate is referred to as being "on / located on" another component, it can be "directly on" the other component (i.e., located on the surface of the other component with no other components between them) or another component can be present between them. In addition, when a component such as a layer, film, region, or plate is "directly on" another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it means that no other components are located between them.

[0048] The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims herein, the phrase "the part" is also intended to include plural forms unless the context clearly indicates otherwise. Among others, components include layers, films, regions, or plates, etc.

[0049] The embodiments of the present application will be described in detail with reference to the drawings. However, those skilled in the art can understand that in the embodiments of the present application, many technical details are proposed in order to make the reader better understand the present application. However, the technical solutions claimed by the present application can be realized even without these technical details and based on various changes and modifications of the following embodiments.

[0050] According to some embodiments of the present application, the embodiments of the present application provide a preparation method of a solid-state secondary battery to improve the poor solid-solid interface contact between the electrolyte and the active material, which affects the battery internal resistance and other characteristics.

[0051] Figure 1 A flow chart corresponding to the preparation method of a solid-state secondary battery provided by an embodiment of the present application is shown in the following figure. Figure 2 A first structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application is shown in the following figure. Figure 3 A top view of a solid-state electrolyte in a solid-state secondary battery provided by an embodiment of the present application is shown in the following figure.

[0052] It should be noted that, Figure 2 The direction from the top cover to the shell can be seen as the side of the positive electrode sheet, the negative electrode sheet and the solid-state electrolyte, so that the cooperation relationship among the three can be clearly seen. Figure 2 The active layer is the positive active layer and the negative active layer in the figure, and those skilled in the art can set only one side of the substrate layer to have branches and active layer according to the needs. Figure 3 The active layer in the figure is a perspective view, so that the arrangement relationship between the branches and the substrate layer can be seen.

[0053] Reference Figures 1 to 3The preparation method includes: forming a solid electrolyte, forming a solid electrolyte, including: preparing a ceramic aerosol, the ceramic aerosol including inorganic ceramic oxide particles and polyimide particles; providing a substrate layer 100, and spraying the ceramic aerosol onto at least one side of the substrate layer 100; heat-treating the substrate layer 100 to remove the polyimide particles, and converting the remaining inorganic ceramic oxide particles into a plurality of branches 110, with gaps between adjacent branches 110, and the branches 110 being located on at least one side of the substrate layer 100; preparing a coating slurry; and applying the coating slurry to the substrate layer 100. Coated on one side of the substrate layer 100, and the coating slurry also flows into the gap; dried, the coating slurry is converted into an active layer 101, and the substrate layer 100 and the branches 110 together constitute a solid electrolyte; prepare the positive electrode sheet 1 and the negative electrode sheet 2, and the preparation steps of at least one of the positive electrode sheet 1 and the negative electrode sheet 2 include: providing a current collector, and the active layer 101 is located between the current collector and the substrate layer 100; stacking the negative electrode sheet 2, the solid electrolyte and the positive electrode sheet 1 in sequence, and hot pressing to obtain a bare battery cell, placing the bare battery cell in a battery shell, and then encapsulating it to obtain a solid-state secondary battery.

[0054] The solid-state secondary battery provided in the embodiment of the present application is prepared by preparing a solid electrolyte, and the surface of the solid electrolyte has multiple branches 110, multiple branches 110 are located between the positive electrode current collector and the substrate layer 100, and / or multiple branches 110 are located between the negative electrode current collector and the substrate layer 100, so that the positive electrode active layer of the positive electrode sheet 1 can be interlaced and interlocked with the solid electrolyte, and the negative electrode active layer of the negative electrode sheet 2 can be interlaced and interlocked with the solid electrolyte, thereby increasing the contact area and reducing the internal resistance of the battery. Secondly, an aerosol process is used to form the branches 110, so that the branches 110 are formed on the surface of the substrate layer 100, and then the active layer 101 is formed, so that the active layer 101 is located in the gaps between the branches 110. The active layer 101 can not only serve as the positive electrode active layer / negative electrode active layer, but also serve as a contact enhancement layer, thereby improving the contact performance and forming a close interface contact between the solid electrolyte layer and the positive electrode sheet 1 and the negative electrode sheet 2 in the subsequent rolling step.

[0055] The preparation method provided above will be described in detail below.

[0056] Based on their appearance, the prepared solid-state secondary batteries can be classified as prismatic, circular, or pouch cells. Based on their capacity, they can be categorized as 50Ah, 100Ah, 150Ah, 200Ah, 280Ah, 306Ah, 314Ah, 500+Ah, 800+Ah, and 1000+Ah. Based on the chemical composition and operating principle of the bare secondary battery cells, they can be lithium-ion batteries, lead-acid batteries, sodium-ion batteries, or nickel-metal hydride batteries. The present application uses the preparation method of a lithium-ion battery as an example. Those skilled in the art can replace the lithium ions in the positive electrode sheet, negative electrode sheet, and electrolyte with corresponding metal ions as needed. For example, for sodium-ion batteries, the lithium transition metal oxide in the subsequent positive electrode active material can be replaced with any of the corresponding layered metal oxides (e.g., NaFeO2), polyanionic compounds (NaFePO4), and Prussian blue-based compound systems (e.g., NaMnFe(CN)6-zH2O).

[0057] A solid-state electrolyte (SSE) is a solid ion conductor and electronically insulating material, and a key component of solid-state secondary batteries. Compared to liquid electrolytes, solid-state electrolytes are safe, free of toxic organic solvent leakage issues, non-flammable, non-volatile, mechanically and thermally stable, easy to process, and have low self-discharge, enabling higher power density and cyclability. For example, because solid-state electrolyte membranes suppress lithium dendrites, lithium metal anodes can be used in practical devices without the inherent limitations of liquid electrolytes. Using high-capacity anodes with low reduction potentials can lead to lighter, thinner, and less expensive rechargeable batteries.

[0058] Solid-state electrolytes include all-solid-state electrolytes and quasi-solid-state electrolytes (QSSEs). All-solid-state electrolytes are further divided into inorganic solid electrolytes (ISEs), solid polymer electrolytes (SPEs), and composite polymer electrolytes (CPEs). QSSEs, also known as gel polymer electrolytes (GPEs), are freestanding membranes containing a certain amount of liquid components fixed within a solid matrix. The ion conduction mechanisms of SPEs and GPEs differ significantly: SPEs conduct ions through interactions with substituents on the polymer chains, while GPEs conduct ions primarily in solvents or plasticizers.

[0059] Solid electrolytes are mainly composed of the following components: lithium salt, which is used as an ion source and is selected from lithium fluoride, lithium sulfide or lithium phosphate; a matrix, which is used to provide mechanical support and form ion transmission channels and is a polymer matrix, which is a copolymer composed of one or more of polyoxyethylene, polyvinylidene fluoride, polyacrylonitrile and polyurethane; an inorganic filler, which is used to enhance the mechanical properties of the electrolyte and improve the ionic conductivity and is selected from lithium oxide, lithium titanate, phosphoric acid and other inorganic fillers. A copolymer formed by combining one or more of lithium, aluminum oxide and silicon oxide; the inorganic filler is a nanoscale filler with a particle size of 1nm~100nm; rare earth elements, rare earth elements are used to improve the lithium ion conductivity of the solid electrolyte, and the rare earth elements are copolymers formed by combining one or more of lanthanum, cerium, praseodymium, neodymium, gadolinium, erbium, lutetium and yttrium; ceramic materials, ceramic materials are used to enhance the toughness of the electrolyte, and the ceramic material is one of zirconium oxide, silicon nitride, silicon dioxide, titanium disulfide and lithium sulfide.

[0060] The solid-state electrolyte preparation process includes mixing inorganic ceramic oxide particles with polyimide particles to form mixed particles. The inorganic ceramic oxide particles are a mixture of lithium salts, inorganic fillers, rare earth elements, and ceramic materials. The polyimide particles form the interstitial structure within the subsequently formed branches 110. During high-temperature curing, the polyimide particles undergo imidization, releasing small molecules (such as water) and causing volume shrinkage. During this shrinkage process, the rigidity of the molecular chains hinders uniform densification of the inorganic ceramic oxide particles. Localized stress concentration causes wrinkles or protrusions at the edges of the pores formed by the sublimation of the polyimide particles, resulting in the formation of irregular array columns, i.e., branches 110.

[0061] In some embodiments, the inorganic ceramic oxide particles may include LLTO (lithium lanthanum titanate / lithium lanthanum titanate, Li 0.33 La 0.56 TiO3), LLZTO (lithium zirconium oxide / lithium lanthanum zirconate, Li7La3Zr2O 12 ) or LiTFSI (bis(trifluoromethylsulfonyl)imide, C2F6LiNO4S2), the representative material of NASICON (sodium superion conductor) type solid electrolyte is LATP (lithium aluminum titanium phosphate, Li 1.3 Al 0.3 Ti 1.7 (PO4)3).

[0062] In some embodiments, in the step of preparing the ceramic aerosol, the volume ratio of the inorganic ceramic oxide particles to the polyimide particles is 1:(1-10).

[0063] The mixed particles are prepared into ceramic aerosol, which can reduce the sintering temperature of the subsequent preparation of solid electrolytes, thereby reducing the preparation cost; and the prepared solid electrolyte has uniform composition and smooth interface.

[0064] Specifically, nitrogen (or helium or oxygen) is used as a carrier gas, and the mixed particles are fed into the aerosol chamber through a gas delivery device, so that the mixed particles in the aerosol chamber are evenly dispersed and form ceramic aerosol.

[0065] A ceramic aerosol is sprayed onto substrate layer 100 to form a prepolymer layer. Specifically, an LLZTO solid electrolyte sheet is used as substrate layer 100. The deposition chamber pressure is set at 8-12 Pa, the nozzle is 9-11 mm from the substrate surface, and the spray angle is 85-95°. A carrier gas is used to spray the aerosol onto the substrate layer 100 through the nozzle at a flow rate of 20-22 L / min for a deposition time of 1-2 hours. This results in a solid electrolyte sheet with deposited mixed particles, i.e., a prepolymer layer.

[0066] The mechanism of aerosol prepolymer layer formation is divided into two stages. Initially, an anchoring layer rapidly forms on the substrate surface as the first batch of micro- and nanoparticles collide with the substrate. However, damage to the interface between the deposited film and the substrate increases the roughness of the contact surface. After the initial anchoring layer is formed, the growth of the deposited film slows by reducing the carrier gas flow rate. In the second stage, particles deposited on the anchoring layer gradually smooth and densify the surface. Through countless repeated combinations of the original particles' fragmentation, deformation, and collisions, a dense deposited film (i.e., the prepolymer layer) is formed. This film-forming phenomenon is also known as the room-temperature collision bonding principle.

[0067] It should be noted that the LLZTO solid electrolyte sheet can be understood as a conventional solid electrolyte sheet, and the embodiments of the present application are further optimization of the conventional solid electrolyte sheet.

[0068] The heat treatment step may include placing the substrate layer 100 including the prepolymer layer in a high temperature reactor and calcining it at 900° C. for 1 to 3 hours to remove the polyimide particles and fuse the inorganic ceramic oxide particles to form a substrate layer in the form of branches 110 .

[0069] The mechanism is that inorganic ceramic oxide particles and polyimide (PI) particles differ significantly in density, particle size distribution, and surface energy. Polyimide particles typically thermally decompose and act as a sacrificial template, while inorganic ceramic oxide particles have a higher structural stability. When ceramic aerosol is deposited by high-speed spraying, the particles inertialy impact the substrate layer 100, producing a "splashing effect". Large-sized particles are preferentially deposited, forming local accumulations. Small particles are disturbed by the airflow to fill the gaps, but are hindered by the elasticity of the PI particles, forming a "micro-arch bridge" structure, resulting in the initial concave-convex morphology of the prepolymer layer surface. Furthermore, when the PI particles are heat-treated at 300°C~500°C, they undergo step-by-step decomposition (releasing gases such as carbon dioxide and formaldehyde). The decomposition kinetics compete with the sintering behavior of the ceramic particles. The gases produced by the PI decomposition will escape along the gaps between the ceramic particles, forming "branch-like channels" in the ceramic skeleton. The ceramic particles undergo surface sintering (neck growth) at high temperatures, while the PI decomposition area collapses in volume. The difference in shrinkage between the two (ceramic shrinkage is about 3%~5%, while the PI decomposition area is >20%) causes tensile stress concentration at the interface, forcing the edge of the pore wall to warp upward, forming protrusions, namely branches 110.

[0070] In some embodiments, the process parameters for the heat treatment include: a reaction temperature of 500° C. to 1000° C., a calcination time of 0.8 h to 1.2 h, and a purge gas rate of 0.5 L / min to 3 L / min.

[0071] The active material, conductive agent, adhesive, and dispersion solution are uniformly mixed to obtain a coating slurry. The coating slurry is applied to one side of the substrate layer 100. The coating slurry flows into the gaps between some of the branches 110 and is dried. The coating slurry is converted into the active layer 101. The substrate layer 100 and the branches 110 together constitute a solid electrolyte.

[0072] In some embodiments, if the active layer is located between the positive electrode current collector and the substrate layer, the active material is a positive electrode active material; if the active layer is located between the negative electrode current collector and the substrate layer, the active material is a negative electrode active material. Take the active layer as a positive electrode active material and the positive electrode active material as LFP (lithium iron phosphate) as an example. Figure 2 LFP, carbon black, and PVDF were mixed in a ratio of (92wt%-98wt%): (0.6wt%-4wt%): (1.4wt%-4wt%). NMP was then added to bring the slurry solids content to 50%. Stirring was performed under negative pressure for 3 hours to obtain an LFP slurry. Using the solid electrolyte layer as the substrate layer 100, the LFP slurry was applied using a doctor blade. Ultrasonication was then applied for 5 minutes to promote the slurry's penetration between the branches 110, followed by drying. The doctor blade coating-ultrasonication-drying steps were repeated three times to obtain an irregularly protruding interlocking structure, i.e., a substrate layer 100 with branches 110.

[0073] In some embodiments, the branches 110 have holes, and the coating slurry flows into the holes; and after the drying treatment, part of the active layer 101 is embedded in the holes. In this way, the coating slurry is located between the holes, which can improve the adhesion between the active layer 101 and the solid-state electrolyte, and the active layer 101 located in the holes can also improve the conductivity.

[0074] In some embodiments, the dispersion solution includes a wetting aid for the coating slurry to flow into the holes. In this way, the wetting aid can improve the wettability of the coating slurry to the solid-state electrolyte, thereby increasing the contact area between the coating slurry and the solid-state electrolyte, so as to improve the interface contact performance between the solid-state electrolyte and the active layer 101.

[0075] In some embodiments, before the drying treatment, the method further includes: ultrasonic treatment for filling the holes with the coating slurry; the ultrasonic treatment has an ultrasonic time of 3 min to 15 min; and the ultrasonic wave has a frequency of 20 kHz to 5 MHz. In this way, the contact performance between the active layer 101 and the solid-state electrolyte can be improved.

[0076] Figure 4 A second structural schematic diagram of a solid-state secondary battery is provided for an embodiment of the present application. Figure 4 Only part of the solid-state electrolyte layer is shown, and the arrangement of the positive electrode sheet and the negative electrode sheet can be referred to Figure 2 , and the following partial cross-sectional view can also be referred to Figure 2 .

[0077] In some embodiments, referring to Figure 4 , the process steps for forming the coating slurry include: uniformly stirring the active material, the nano-inorganic ceramic oxide particles, the conductive agent, the binder, and the dispersion solution to obtain a second mixed solution; and high-speed dispersing the second mixed solution under negative pressure for 4 h to 6 h to obtain the coating slurry, the viscosity of the coating slurry being in the range of 5000 mPa·s to 20000 mPa·s; wherein the mass ratio of the active material, the nano-inorganic ceramic oxide particles, the conductive agent, and the binder is (73wt% to 93wt%) : (5wt% to 18wt%) : (0.6wt% to 4.5wt%) : (1.4wt% to 4.5wt%).

[0078] In some embodiments, the average particle size of the second mixed solution formed by the active material, the nano-inorganic ceramic oxide particles, the conductive agent, and the binder in the coating slurry is less than 20 μm.

[0079] Taking LFP as the active material for the positive electrode active layer, as an example, LFP, nano-LLZO (lithium lanthanum zirconium oxide) particles, carbon black, and PVDF were mixed in a ratio of (73wt%-93wt%): (5wt%-18wt%): (0.6wt%-4.5wt%): (1.4wt%-4.5wt%). NMP was then added to a slurry with a solids content of 60%. The mixture was dispersed at high speed under negative pressure for 5 hours to obtain a mixed slurry with a viscosity ranging from 5000mPa·s to 20000mPa·s and a fineness of less than 20μm. The mixed slurry was pumped into a buffer tank and then passed through a feed pipe to a coating die, where it was coated onto the LLZO solid electrolyte sheet at a coating speed of 5m / min. The coated sheet was transported by conveyor belts into a multi-section oven with a temperature setting range of 80°C to 130°C. After the slurry is dried, the LLZO particles in the coating layer are converted into secondary sphere aggregates 102 due to the self-aggregation tendency of the nano-LLZO particles in the slurry.

[0080] The mechanism is as follows: high-speed dispersion is carried out under negative pressure for 5 hours, and the hard agglomerates of LLZO nanoparticles are disassembled by shear force, so that they are temporarily evenly dispersed. At this time, the PVDF molecular chains are fully extended in the NMP solvent, and partially adsorbed on the surface of the particles to form a steric hindrance layer, which delays re-agglomeration. The solid content of the slurry reaches 60% or even higher, indicating that the viscosity of the slurry is relatively high. The high viscosity environment restricts the free movement of the particles, but at the same time it also aggravates the "crowding effect" between the particles, prompting the LLZO particles to pre-aggregate in local areas due to physical extrusion. In the subsequent drying step, LLZO nanoparticles have high surface energy. After the solvent evaporates, the exposed particle surface tends to reduce the total surface area by aggregation, reducing the free energy of the system, thereby forming secondary spherical aggregates 102.

[0081] Figure 5 This is a third structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application.

[0082] refer to Figure 5 The coating slurry includes an active material, and the surface of the active material is coated with Ga-LLZO; the process steps for forming the active material include: stirring Ga-LLZO particles, active particles and a solution to form a first mixed solution; drying the first mixed solution to form a first precursor; calcining the first precursor to form a Ga-LLZO-coated active material; wherein the mass ratio of Ga-LLZO particles to active particles is (0.5wt%~2wt%): (8wt%~9.5wt%).

[0083] It should be noted that if the active material is a positive electrode active material, the active material may be a lithium source material; if the active material is a negative electrode active material, the active material may be graphite.

[0084] Take the active material LFP as an example. Nanometer Ga-LLZO particles and LFP are added to NMP solvent in a ratio of (0.5wt%-2wt%):(8wt%-9.5wt%), mixed uniformly, dried to remove NMP, calcined at 700°C for 30min-60min, and Ga-LLZO coated LFP structure is formed. Ga-LLZO coated LFP structure, carbon black, and PVDF are mixed in a ratio of (92wt%-98wt%):(0.6wt%-4wt%):(1.4wt%-4wt%), and then NMP is added to make the slurry solid content reach 60%. Stirring under negative pressure for 3h-5h, LFP slurry is obtained. LLZO solid electrolyte sheet is used as the base material layer, and LFP slurry is extrusion coated, and after drying, the surface coated form of the intercalation structure is obtained. The surface coated form of the structure is Ga-LLZO coated active material 103.

[0085] Figure 6 A fourth structure schematic diagram of a solid-state secondary battery is provided for an embodiment of the present application.

[0086] In some embodiments, referring to Figure 6 , the coating slurry includes an active material. The active material is graphite; after forming the solid-state electrolyte, further including: stirring the lithium bisfluorosulfonylimide salt, poly(ethylene glycol) methacrylate, polyethylene glycol dimethacrylate, a photoinitiator, graphite, and conductive carbon black uniformly to obtain a curing liquid; immersing the solid-state electrolyte in the curing liquid, and performing curing treatment on the solid-state electrolyte with the curing liquid; wherein the mass ratio of the lithium bisfluorosulfonylimide salt: poly(ethylene glycol) methacrylate: polyethylene glycol dimethacrylate: photoinitiator: graphite: conductive carbon black is (35wt%-55wt%):(30wt%-50wt%):(1wt%-7.5wt%):(1.5wt%-4.5wt%):(2wt%-7wt%):(1wt%-3wt%).

[0087] In pure water, graphite, carbon black, CMC, SBR are mixed in the ratio of (92wt%~96wt%): (1wt%~3wt%): (0.5wt%~2.5wt%): (1.5wt%~3.5wt%) to make the slurry solid content reach 50%. Stir for 3h under negative pressure to obtain graphite slurry. Take LLZO solid electrolyte sheet as the base material layer, extrude the graphite slurry, and dry to obtain a solid electrolyte sheet coated with graphite. Dip the above solid electrolyte sheet into the curing liquid and stand for 30min~60min. In the curing liquid, the mass ratio of lithium bisfluorosulfonylimide: poly(ethylene glycol) methacrylate: polyethylene glycol dimethacrylate: photoinitiator: graphite: conductive carbon black is (35wt%~55wt%): (30wt%~50wt%): (1wt%~7.5wt%): (1.5wt%~4.5wt%): (2wt%~7wt%): (1wt%~3wt%). After standing, take out the solid electrolyte sheet and cure it under UV for 3min~6min to obtain a cross-network form of intercalation structure.

[0088] The mechanism is that the PEG-based polymer network 104 (i.e. the polymer composed of poly(ethylene glycol) methacrylate: polyethylene glycol dimethacrylate) and the graphite / carbon black conductive path 105 are interpenetrated to form a double-continuous phase structure. The polymer network conducts ions and the carbon black network conducts electrons (carbon black self-aggregates, and long-range conductive segments construct a conductive network), improving the ion / electron conduction capacity of the active material layer. After curing, a polymer film will also be formed on the surface of the active material layer, enhancing the strength of the solid electrolyte. The addition of conductive materials can improve the electronic conductivity of the current collector.

[0089] In some embodiments, the active layer can be used as the active layer of the positive electrode sheet. The current collector is a positive electrode current collector, and the process steps for forming the positive electrode sheet include: providing a positive electrode current collector, the positive electrode current collector being located on the surface of the active layer 101, and heat pressing the solid electrolyte and the positive electrode current collector, the active layer 101 and the positive electrode current collector constituting the positive electrode sheet 1.

[0090] In some embodiments, the active layer can be used as part of the active layer of the positive electrode sheet, and the positive electrode sheet also has a positive electrode sub-active layer. The current collector is a positive electrode current collector, and the process steps for forming the positive electrode sheet include: preparing a positive electrode sub-active layer, the positive electrode sub-active layer being located on the surface of the active layer 101; providing a positive electrode current collector, the positive electrode current collector being located on the surface of the positive electrode sub-active layer; heat pressing the solid electrolyte and the positive electrode current collector, the positive electrode sub-active layer, the active layer 101 and the positive electrode current collector constituting the positive electrode sheet 1. The active layer 101 not only serves as a positive electrode active layer, but also as a contact enhancement layer, thereby improving the contact performance and forming a tight interfacial contact between the solid electrolyte layer and the positive electrode sheet during the heat pressing step.

[0091] Similarly, the active layer can serve as the active layer of the negative electrode sheet. The current collector is the negative electrode current collector. The process steps for forming the negative electrode sheet include: providing the negative electrode current collector, which is located on the surface of the active layer 101; performing a hot pressing process on the solid electrolyte and the negative electrode current collector; the active layer 101 and the negative electrode current collector form the negative electrode sheet 2.

[0092] In some embodiments, the active layer can serve as a partial active layer of a negative electrode sheet. The negative electrode sheet also includes a negative sub-active layer, and the current collector is a negative electrode current collector. The process steps for forming the negative electrode sheet include: preparing the negative sub-active layer, which is located on the surface of the active layer 101; providing the negative electrode current collector, which is located on the surface of the negative sub-active layer; and hot pressing the solid electrolyte and the negative electrode current collector. The negative electrode sub-active layer, active layer 101, and negative electrode current collector constitute the negative electrode sheet 2. The active layer 101 not only serves as the negative electrode active layer, but also serves as a contact enhancement layer, thereby improving contact performance and forming a close interface contact between the solid electrolyte layer and the negative electrode sheet during the hot pressing step.

[0093] The preparation method also includes: welding the tabs to the adapter, connecting the other end of the adapter to the terminal post; and engaging the top cover with the battery case. The adapter is located in the cavity, and the terminal post passes through the top cover.

[0094] Among them, the adapter plate includes at least a first adapter plate and a second adapter plate, the pole includes a positive pole pole and a negative pole pole, the first adapter plate is electrically connected to the positive pole tab and the positive pole pole of the positive pole plate respectively, and the second adapter plate is electrically connected to the negative pole tab and the negative pole pole of the negative pole plate respectively.

[0095] The method for preparing a solid-state secondary battery provided in an embodiment of the present application is to prepare a solid electrolyte, and the surface of the solid electrolyte has multiple branches 110, and the multiple branches 110 are located between the positive electrode current collector and the substrate layer 100, and / or the multiple branches 110 are located between the negative electrode current collector and the substrate layer 100, so that the positive electrode active layer of the positive electrode sheet 1 can be interlaced and interlocked with the solid electrolyte, and the negative electrode active layer of the negative electrode sheet 2 can be interlaced and interlocked with the solid electrolyte, thereby increasing the contact area and reducing the internal resistance of the battery. Secondly, an aerosol process is used to form the branches 110, so that the branches 110 are formed on the surface of the substrate layer 100, and then the active layer 101 is formed, so that the active layer 101 is located in the gaps between the branches 110. The active layer 101 can not only serve as the positive electrode active layer / negative electrode active layer, but also serve as a contact enhancement layer, thereby improving the contact performance and forming a close interface contact between the solid electrolyte layer and the positive electrode sheet 1 and the negative electrode sheet 2 in the subsequent rolling step.

[0096] According to some embodiments of the present application, another aspect of the present application provides a solid-state secondary battery, comprising: a battery case having a cavity therein; a bare cell located within the cavity; the bare cell comprising a stacked positive electrode sheet 1, a solid electrolyte, and a negative electrode sheet 2, wherein the solid electrolyte comprises: a substrate layer 100 and a plurality of branches 110, with gaps between adjacent branches 110, the branches 110 being located on at least one side of the substrate layer 100; an active layer 101, the active layer 101 being located on the surface of the substrate layer 100 and within the gaps; the active layer being located between the substrate layer 100 and the positive electrode current collector, and / or between the substrate layer 100 and the negative electrode current collector. The active layer located between the substrate layer 100 and the positive electrode current collector is part of the positive electrode active layer and, together with the positive electrode current collector, constitutes the positive electrode sheet 1; the active layer located between the substrate layer 100 and the negative electrode current collector is part of the negative electrode active layer and, together with the negative electrode current collector, constitutes the negative electrode sheet 2.

[0097] In some embodiments, the branches 110 have holes therein, and a portion of the active layer 101 is embedded in the holes.

[0098] In some embodiments, the active layer 101 includes a Ga-LLZO-coated active material.

[0099] The beneficial effects of the embodiments of the present application will be further illustrated below in combination with examples and comparative examples.

[0100] Example 1:

[0101] LLZTO particles and PI particles were mixed uniformly in a volume ratio of 1:2 to produce mixed particles. Nitrogen was used as a carrier gas and delivered into the aerosol chamber via a gas delivery device to uniformly disperse the mixed particles. An LLZTO solid electrolyte sheet was used as the substrate layer. The deposition chamber pressure was set at 10 Pa, the nozzle was 10 mm from the substrate surface, and the spray angle was 90°. The aerosol was sprayed onto the substrate surface 100° using a carrier gas at a flow rate of 20 L / min for 1 hour. This resulted in a prepolymer layer containing the deposited mixed particles. The prepolymer layer was then placed in a high-temperature reactor and calcined at 900°C for 1 hour to remove the PI particles and fuse the LLZTO particles to form a dendrite-like precursor. LFP, carbon black, and PVDF were mixed in a ratio of 94 wt%:3 wt%:3 wt%, and then NMP was added to achieve a slurry solids content of 50%. The mixture was stirred under negative pressure for 3 hours to produce an LFP slurry. Using the solid electrolyte layer as the substrate, LFP slurry was applied with a doctor blade. Ultrasonication was then applied for 5 minutes to promote the slurry's penetration between the array pillars, followed by drying. The doctor blade-ultrasonication-drying process was repeated three times to obtain a solid electrolyte with dendrites.

[0102] A positive electrode sheet and a negative electrode sheet are provided, and the active layer is the positive electrode active layer of the positive electrode sheet; the negative electrode sheet, the solid electrolyte and the positive electrode sheet are stacked and hot-pressed in sequence to obtain a bare battery cell, the bare battery cell is placed in a battery shell, and then packaged to obtain a solid-state secondary battery.

[0103] Example 2: The difference from Example 1 is that the volume ratio of LLZTO particles to PI particles is 1:1.

[0104] Example 3: The difference from Example 1 is that the volume ratio of LLZTO particles to PI particles is 1:10.

[0105] Example 4: The difference from Example 1 is that the active layer is the positive electrode active layer of the positive electrode sheet and the negative electrode active layer of the negative electrode sheet.

[0106] Example 5: The difference from Example 1 is that the prepolymer layer is placed in a high-temperature reactor and calcined at 500° C. for 1 hour to remove the PI particles and simultaneously fuse the LLZTO particles to form a substrate layer with branches.

[0107] Example 6: The difference from Example 1 is that the prepolymer layer is placed in a high-temperature reactor and calcined at 1000°C for 1 hour to remove the PI particles and simultaneously fuse the LLZTO particles to form a substrate layer with branches.

[0108] Example 7:

[0109] The difference from Example 1 is that the preparation step of the active layer 101 is to mix LFP, nano-LLZO particles, carbon black, and PVDF in the ratio of 80wt%: 14wt%: 3wt%: 3wt%, and then add NMP to make the solid content of the slurry reach 60%, and disperse it at high speed under negative pressure for 5 hours to obtain a mixed slurry with a slurry viscosity range of 10000mPa·s and a fineness of less than 20μm; coating: the mixed slurry is pumped into the buffer tank, enters the coating die through the feed pipe, and is coated on the LLZO solid electrolyte sheet at a coating speed of 5m / min. The coated sheet is transported into a multi-section oven via a conveyor belt, and the oven temperature setting range is 80℃~130℃. After the slurry is dried, the self-aggregation tendency of the nano-LLZO particles in the slurry is as follows Figure 4 structure.

[0110] Example 8: The difference from Example 7 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 76wt%:18wt%:3wt%:3wt%.

[0111] Example 9: The difference from Example 7 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 89wt%:5wt%:3wt%:3wt%.

[0112] Example 10:

[0113] Add nano-Ga-LLZO particles and LFP to NMP solvent in a ratio of 1wt%:9wt%, mix evenly, dry and remove NMP, and calcine at 700℃ for 30min to form a Ga-LLZO-coated LFP structure. The Ga-LLZO-coated LFP structure, carbon black, and PVDF are mixed in a ratio of 94wt%:3wt%:3wt%, and then NMP is added to make the solid content of the slurry reach 60%. Stir for 3h under negative pressure to obtain LFP slurry. Using LLZO solid electrolyte sheet as the substrate layer, extrusion-coated LFP slurry, after drying, a staggered interlocking structure in the form of surface coating is obtained, i.e. Figure 5 structure.

[0114] Example 11: The difference from Example 10 is that the mass ratio of nano-Ga-LLZO particles to LFP is 2wt%:8wt%.

[0115] Example 12: The difference from Example 10 is that the mass ratio of nano-Ga-LLZO particles to LFP is 0.5wt%:9.5wt%.

[0116] Example 13: The difference from Example 10 is that the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 98wt%:0.6wt%:1.4wt%.

[0117] Example 14: The difference from Example 10 is that the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 92wt%:4wt%:4wt%.

[0118] Example 15:

[0119] In pure water, graphite, carbon black, CMC, and SBR are mixed in a ratio of 94wt%: 2wt%: 1.5wt%: 2.5wt% to make the solid content of the slurry reach 50%. Stir under negative pressure for 3 hours to obtain graphite slurry. Using LLZO solid electrolyte sheet as the substrate layer, extrusion-coated graphite slurry is applied, and after drying, a solid electrolyte sheet coated with graphite is obtained. The above solid electrolyte sheet is immersed in the curing liquid and allowed to stand for 30 minutes. In the curing liquid, the mass ratio of LiFSI: PEGMA: PEGDMA: D1173: graphite: SP is 45wt%: 40wt%: 5wt%: 3wt%: 5wt%: 2wt%. After standing, the solid electrolyte sheet is taken out and cured under UV for 3 minutes to obtain an interlaced interlocking structure in the form of a cross network, that is, Figure 6 structure.

[0120] Example 16: Different from example 15, the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 35wt%:50wt%:5wt%:3wt%:5wt%:2wt%.

[0121] Example 17: Different from example 15, the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 55wt%:30wt%:5wt%:3wt%:5wt%:2wt%.

[0122] Comparative example 1: The solid-state electrolyte is a LLZTO solid-state electrolyte sheet.

[0123] Comparative example 2: Different from example 1, the volume ratio of LLZTO particles to PI particles is 1:0.1.

[0124] Comparative example 3: Different from example 1, the volume ratio of LLZTO particles to PI particles is 1:20.

[0125] Comparative example 4: Different from example 1, the temperature of the reaction kettle is 300°C.

[0126] Comparative example 5: Different from example 1, the temperature of the reaction kettle is 1500°C.

[0127] Comparative example 6: Different from example 7, the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 64wt%:30wt%:3wt%:3wt%.

[0128] Comparative example 7: Different from example 7, the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 93wt%:1wt%:3wt%:3wt%.

[0129] Comparative example 8: Different from example 10, the mass ratio of nano-Ga-LLZO particles to LFP is 3wt%:7wt%.

[0130] Comparative example 9: Different from example 10, the mass ratio of nano-Ga-LLZO particles to LFP is 0.2wt%:9.8wt%.

[0131] Comparative example 10: Different from example 10, the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 90wt%:5wt%:5wt%.

[0132] Comparative example 11: Different from example 10, the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 99wt%:0.5wt%:0.5wt%.

[0133] Comparative Example 12: The difference from Example 15 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 25wt%:60wt%:5wt%:3wt%:5wt%:2wt%.

[0134] Comparative Example 13: The difference from Example 15 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 65wt%:20wt%:5wt%:3wt%:5wt%:2wt%.

[0135] The electrochemical performance tests were performed on the solid-state secondary batteries prepared in the above examples and comparative examples, and the test results were summarized and recorded in Table 1.

[0136] Electrochemical performance test: The test temperature is 25±2°C. Charge at a constant current of 0.5C to 3.65V; wait for 10 minutes, then discharge at a constant current of 0.5C to a cut-off voltage of 2.5V. Record the capacity and use it as the initial capacity for the rate test. Then charge at a constant current of 1C to 3.65V; wait for 10 minutes; then discharge at a constant current of 1C to a cut-off voltage of 2.5V. Record the capacity and use it as the 1C rate capacity. The C-rate (abbreviated as C) is a value relative to the rated capacity of the battery. For example, if a battery has a rated capacity of 200Ah, then 1C is equivalent to a charge or discharge rate of 200A. Based on this definition, 0.5C means the battery can be fully charged in 2 hours, while 1C means it can be fully charged in 1 hour.

[0137] Table 1

[0138]

[0139] Referring to the experimental data in Table 1, it can be seen that the solid electrolytes provided in the embodiments of the present application can improve rate capacity compared to conventional solid electrolytes, as shown in the electrochemical performance tests of Examples 1 to 6 and Comparative Examples 1 to 5. The solid electrolytes with a dendrite structure provided in the embodiments of the present application can optimize rate capacity and initial capacity, as shown in the electrochemical performance tests of Examples 7 to 17 and Comparative Examples 6 to 13.

[0140] Correspondingly, another embodiment of the present application provides a method for preparing a solid electrolyte, which is different from the above embodiment in that some process steps are changed, and the structure of the obtained solid electrolyte layer is different. The technical features that are the same as or corresponding to the above embodiment will not be described in detail here.

[0141] refer to Figure 7The preparation method includes: in an argon-protected glove box, a lithium metal compound, a lanthanum metal compound, and a zirconium metal compound are mixed in a molar ratio of (10-11): (2.5-3.5): (1.5-2.5) to obtain a metal precursor, with oxygen and water contents each below 1 ppm. The premixed metal precursor is deposited using a laser to evaporate the premixed metal precursor onto the surface of an LLZO solid electrolyte as the substrate layer 200, with a baffle having an array of holes disposed on the surface. The deposition temperature is set at 700°C to 800°C, and the deposition chamber pressure is 1 kPa to 1.5 kPa. Argon is used as the carrier gas at a flow rate of 3 standard liters / min to 3.5 standard liters / min; oxygen is used as the reactant gas at a flow rate of 2 standard liters / min to 2.5 standard liters / min. The reaction time is 30 to 60 minutes. After the reaction is terminated, the temperature is maintained for 15 to 25 minutes, followed by a cooling rate of 1°C / s to 1.5°C / s to obtain a prepolymer having surface-grown array pillars 210.

[0142] The active material, conductive agent, adhesive and dispersion solution are stirred evenly to obtain a first coating slurry; the first coating slurry is covered on the prepolymer, wherein the first coating slurry will flow into the gaps between some array columns 210, and after drying, a solid electrolyte is formed, and the coating slurry is transformed into an active layer 201.

[0143] In some embodiments, if the active layer is located between the positive electrode current collector and the substrate layer, the active material is a positive electrode active material; if the active layer is located between the negative electrode current collector and the substrate layer, the active material is a negative electrode active material.

[0144] In some embodiments, LFP, carbon black, and PVDF are mixed in a ratio of (92 wt%-96 wt%): (2 wt%-4 wt%): (2 wt%-4 wt%), followed by the addition of NMP to a slurry solids content of 50%. The mixture is stirred under negative pressure for 3 hours to obtain an LFP slurry. Using the solid electrolyte layer as the substrate, the LFP slurry is applied with a doctor blade. Ultrasonication is then applied for 5 minutes to promote wetting of the slurry between the array pillars, followed by drying. The doctor blade-ultrasonication-drying step is repeated three times to obtain an interlocking interlocking structure in the form of an array pillar.

[0145] In some embodiments, the lithium metal compound may be LiC 11 H 19 O2; the lanthanum metal compound may be La(C5H7O2)3·4H2O, and the zirconium metal compound may be Zr(C5H7O2)4.

[0146] The mechanism is as follows: LLZO array columns are grown by laser deposition template; laser (such as carbon dioxide laser, wavelength 8μm~12μm) is focused on the precursor target, and the metal organic compound is vaporized by instantaneous high temperature (>2000℃). The gaseous precursor is transported to the LLZO substrate layer under the drive of carrier gas (Ar). The micropores (diameter ≈50μm, spacing ≈100μm) on the baffle limit the deposition area. After the gaseous precursor passes through the micropores, due to diffusion restriction, a local concentration gradient is formed on the surface of the substrate layer, driving columnar growth. The gaseous precursor reacts with O2 to form Li-La-Zr-O aerosol, which undergoes heterogeneous nucleation on the LLZO surface (activation energy ≈150kJ / mol). The columnar growth preferentially grows along the (110) crystal plane (anisotropic surface energy difference), and finally forms a single crystal LLZO array column. Combined with multi-step ultrasonic assisted coating and PVDF bonding phase regulation, a three-dimensional interlaced structure of LFP and LLZO was successfully constructed. This structure can achieve synergistic optimization of high energy density, low impedance and long cycle life through vertical ion channels, three-dimensional electronic networks and multi-level stress buffering mechanisms.

[0147] Prepare the positive electrode sheet 1 and the negative electrode sheet 2, and the preparation steps of at least one of the positive electrode sheet 1 and the negative electrode sheet 2 include: providing a current collector, with the active layer 101 located between the current collector and the substrate layer 100; stacking the negative electrode sheet, the solid electrolyte and the positive electrode sheet in sequence, and hot pressing to obtain a bare battery cell, placing the bare battery cell in a battery shell, and then encapsulating it to obtain a solid-state secondary battery.

[0148] Figure 8 This is a sixth structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application.

[0149] In some embodiments, reference Figure 8 The process steps for forming the first coating slurry include: uniformly stirring the active material, nano-inorganic ceramic oxide particles, a conductive agent, a binder and a dispersed solution to obtain a second mixed solution; dispersing the second mixed solution at high speed under negative pressure for 4 hours to 6 hours to obtain a coating slurry, the viscosity of the coating slurry ranges from 5000mPa·s to 20000mPa·s, and the particle size is less than 20μm; wherein the mass ratio of the active material, nano-inorganic ceramic oxide particles, the conductive agent and the binder is (73wt%~93wt%): (5wt%~18wt%): (0.6wt%~4.5wt%): (1.4wt%~4.5wt%).

[0150] LFP, nano-LLZO particles, carbon black, and PVDF were mixed in a ratio of (73wt%-93wt%): (5wt%-18wt%): (0.6wt%-4.5wt%): (1.4wt%-4.5wt%). NMP was then added to achieve a slurry solids content of 60%. The mixture was dispersed at high speed under negative pressure for 5 hours to obtain a mixed slurry with a viscosity ranging from 5000mPa·s to 20000mPa·s and a fineness of less than 20μm. The mixed slurry was pumped into a buffer tank and then, through a feed pipe, into a coating die. The die was then coated onto an LLZO solid electrolyte sheet at a coating speed of 5m / min. The coated sheet was transported via a conveyor belt into a multi-section oven set at a temperature range of 80°C to 130°C. After drying, the LLZO particles in the coating layer transformed into secondary spherical aggregates 202 due to the self-aggregation tendency of the nano-LLZO particles in the slurry.

[0151] Figure 9 This is a seventh structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application.

[0152] refer to Figure 9 The active material is a Ga-LLZO-coated active material. The process steps for forming the active material layer include: uniformly stirring Ga-LLZO particles, active particles, and a first dispersed solution to form a first mixed solution; drying the first mixed solution to form a first precursor; and calcining the first precursor to form the Ga-LLZO-coated active material. The mass ratio of the Ga-LLZO particles to the active particles is (0.5wt%-2wt%):(8wt%-9.5wt%). If the active material is a positive electrode active material, the active material can be a lithium source material; if the active material is a negative electrode active material, the active material can be graphite.

[0153] Nano-Ga-LLZO particles and LFP were added to an NMP solvent in a ratio of (0.5wt%-2wt%): (8wt%-9.5wt%), mixed evenly, and dried to remove the NMP. The mixture was then calcined at 700°C for 30-60 minutes to form a Ga-LLZO-coated LFP structure. The Ga-LLZO-coated LFP structure, carbon black, and PVDF were mixed in a ratio of (92wt%-98wt%): (0.6wt%-4wt%): (1.4wt%-4wt%), followed by the addition of NMP to a slurry with a solid content of 60%. The mixture was stirred under negative pressure for 3-5 hours to obtain an LFP slurry. The LFP slurry was extrusion-coated onto an LLZO solid electrolyte sheet as the substrate layer. After drying, a surface-coated interlocking structure was obtained. This surface-coated interlocking structure represents the Ga-LLZO-coated active material 203.

[0154] Figure 10This is a schematic diagram of an eighth structure of a solid-state secondary battery provided in one embodiment of the present application.

[0155] In some embodiments, reference Figure 10 , the active material is graphite; after forming the solid electrolyte, the method further includes: uniformly stirring bisfluorosulfonyl imide lithium salt, poly (ethylene glycol) methacrylate, polyethylene glycol dimethacrylate, a photoinitiator, graphite and conductive carbon black to obtain a solidified liquid; immersing the solid electrolyte in the solidified liquid, and performing a solidification treatment on the solid electrolyte with the solidified liquid; wherein the mass ratio of bisfluorosulfonyl imide lithium salt: poly (ethylene glycol) methacrylate: polyethylene glycol dimethacrylate: photoinitiator: graphite: conductive carbon black is (35wt%~55wt%): (30wt%~50wt%): (1wt%~7.5wt%): (1.5wt%~4.5wt%): (2wt%~7wt%): (1wt%~3wt%).

[0156] Graphite, carbon black, CMC, and SBR were mixed in pure water in a ratio of (92wt%-96wt%): (1wt%-3wt%): (0.5wt%-2.5wt%): (1.5wt%-3.5wt%) to a slurry with a solids content of 50%. Stirring was performed under negative pressure for 3 hours to obtain a graphite slurry. The graphite slurry was extrusion-coated onto an LLZO solid electrolyte sheet as the substrate layer. After drying, a graphite-coated solid electrolyte sheet was obtained. The solid electrolyte sheet was immersed in the curing solution and allowed to stand for 30-60 minutes. In the curing solution, the mass ratios of lithium bis(fluorosulfonyl)imide salt: poly(ethylene glycol) methacrylate: polyethylene glycol dimethacrylate: photoinitiator: graphite: conductive carbon black are (35wt%-55wt%): (30wt%-50wt%): (1wt%-7.5wt%): (1.5wt%-4.5wt%): (2wt%-7wt%): (1wt%-3wt%). After standing, the solid electrolyte sheet is removed and cured under UV light for 3-6 minutes to obtain an interlocking intercalated structure in the form of a cross-network. This cross-network structure refers to a cross-network formed by the PEG-based polymer network 204 (i.e., a polymer composed of poly(ethylene glycol) methacrylate: polyethylene glycol dimethacrylate) and the graphite / carbon black conductive paths 205.

[0157] According to some embodiments of the present application, another aspect of the embodiments of the present application provides a solid-state secondary battery, comprising: a battery shell, the battery shell having a cavity inside; a bare battery cell, the bare battery cell being located in the cavity; the bare battery cell comprising a laminated positive electrode sheet, a solid-state electrolyte, and a negative electrode sheet, wherein the solid-state electrolyte comprises: a substrate layer 200 and an array column 210, the array column 210 being located on the surface of the substrate layer 200, the array column 210 having gaps between the array columns 210, and the surface of the array column 210 having an active layer 201; the active layer 201 being located on the surface of the substrate layer 200 and in the gaps; the active layer 201 being located between the substrate layer 200 and the positive current collector, and / or the active layer being located between the substrate layer 100 and the negative current collector. The active layer between the substrate layer 200 and the positive current collector is part of the positive active layer, and the positive current collector together forms the positive electrode sheet 1. The active layer between the substrate layer 200 and the negative current collector is part of the negative active layer, and the negative current collector together forms the negative electrode sheet 2.

[0158] In some embodiments, the array column 210 has a hole therein, and part of the active layer is embedded in the hole.

[0159] In some embodiments, the material of the active layer is Ga-LLZO coated active material.

[0160] The beneficial effects of the embodiments of the present application will be further illustrated below in combination with examples and comparative examples.

[0161] Example 18: In an argon-protected glove box, LiC 11 H 19 O2, La(C5H7O2)3·4H2O and Zr(C5H7O2)4 were mixed in a molar ratio of 10.5:3:2, and the oxygen content and water content were each below 1 ppm; the surface of the LLZO solid-state electrolyte layer was used as the substrate layer, and a baffle with array holes was arranged on the surface; a laser was used to evaporate the premixed precursor to perform deposition operation. The deposition temperature was set to 700°C, and the deposition chamber pressure was 1 kPa; argon was used as the carrier gas, and the flow rate was 3 standard liters / min; oxygen was used as the reaction gas, and the flow rate was 2 standard liters / min; the reaction time was 30 min. After the reaction stopped, the temperature was kept for 15 min, and then the temperature was lowered at a rate of 1°C / s. A pre-polymer with array column grown on the surface was obtained.

[0162] LFP, carbon black and PVDF were mixed in a ratio of 94wt%:3wt%:3wt%, and then NMP was added to make the solid content of the slurry reach 50%. After stirring for 3 h under negative pressure, LFP slurry was obtained. The solid-state electrolyte layer was used as the substrate layer, and the LFP slurry was coated using a doctor blade, and ultrasonic was applied for 5 min to promote the infiltration of the slurry between the array columns, and then dried. The steps of doctor blade coating-ultrasonic-drying were repeated for 3 times to obtain an interleaved intercalation structure in the form of array columns.

[0163] A positive electrode sheet and a negative electrode sheet are provided, an active layer is part of a positive electrode active layer of the positive electrode sheet, and a negative electrode active layer of the negative electrode sheet is located in a gap between the array columns; the negative electrode sheet, the solid-state electrolyte, and the positive electrode sheet are sequentially stacked and hot-pressed to obtain a bare battery cell, the bare battery cell is placed in a battery shell, and the solid-state secondary battery is obtained by post-packaging.

[0164] Example 19: Different from example 18, LiC 11 H 19 The molar ratio of O2, La(C5H7O2)3·4H2O, and Zr(C5H7O2)4 is 11:2.5:2.

[0165] Example 20: Different from example 18, LiC 11 H 19 The molar ratio of O2, La(C5H7O2)3·4H2O, and Zr(C5H7O2)4 is 10.5:3:2.5.

[0166] Example 21: Different from example 18, the positive electrode active layer of the positive electrode sheet is located in the gap between the array columns, and the negative electrode active layer of the negative electrode sheet is located in the gap between the array columns.

[0167] Example 22: Different from example 18, the preparation step of the active layer 101 is to mix LFP, nano-LLZO particles, carbon black, and PVDF according to 80wt%:14wt%:3wt%:3wt%, then add NMP, so that the solid content of the slurry reaches 60%, and high-speed dispersion under negative pressure for 5h to obtain a mixed slurry, the viscosity range of the slurry is 10000mPa·s, and the fineness is less than 20μm; coating: the mixed slurry is pumped into a buffer tank, enters a coating die through a feeding pipeline, and is coated on the LLZO solid-state electrolyte sheet at a coating speed of 5m / min. The coated sheet is transported by a belt into a multi-section oven, and the oven temperature is set in the range of 80℃~130℃. After the slurry is dried, the self-aggregation tendency of the nano-LLZO particles in the slurry presents a structure as shown in Figure 8 .

[0168] Example 23: Different from example 22, the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 76wt%:18wt%:3wt%:3wt%.

[0169] Example 24: Different from example 22, the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 89wt%:5wt%:3wt%:3wt%.

[0170] Example 25: Add nano-Ga-LLZO particles and LFP to NMP solvent in a ratio of 1wt%:9wt%, mix evenly, dry to remove NMP, and calcine at 700°C for 30 minutes to form a Ga-LLZO-coated LFP structure. The Ga-LLZO-coated LFP structure, carbon black, and PVDF are mixed in a ratio of 94wt%:3wt%:3wt%, and then NMP is added to make the solid content of the slurry reach 60%. Stir for 3 hours under negative pressure to obtain LFP slurry. Using the LLZO solid electrolyte sheet as the substrate layer, extrusion-coated LFP slurry, and after drying, a staggered interlocking structure in the form of surface coating is obtained, that is, Figure 9 structure.

[0171] Example 26: The difference from Example 25 is that the mass ratio of nano-Ga-LLZO particles to LFP is 2wt%:8wt%.

[0172] Example 27: The difference from Example 25 is that the mass ratio of nano-Ga-LLZO particles to LFP is 0.5wt%:9.5wt%.

[0173] Example 28: The difference from Example 25 is that the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 98wt%:0.6wt%:1.4wt%.

[0174] Example 29: The difference from Example 25 is that the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 92wt%:4wt%:4wt%.

[0175] Example 30: In pure water, graphite, carbon black, CMC, and SBR are mixed in a ratio of 94wt%: 2wt%: 1.5wt%: 2.5wt% to make the solid content of the slurry reach 50%. Stir under negative pressure for 3 hours to obtain graphite slurry. Using LLZO solid electrolyte sheet as the substrate layer, extrusion-coated graphite slurry is applied, and after drying, a solid electrolyte sheet coated with graphite is obtained. The above solid electrolyte sheet is immersed in a curing liquid and allowed to stand for 30 minutes. In the curing liquid, the mass ratio of LiFSI: PEGMA: PEGDMA: D1173: graphite: SP is 45wt%: 40wt%: 5wt%: 3wt%: 5wt%: 2wt%. After standing, the solid electrolyte sheet is taken out and cured under UV for 3 minutes to obtain an interlaced interlocking structure in the form of a cross network, that is, Figure 10 structure.

[0176] Example 31: The difference from Example 30 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 35wt%:50wt%:5wt%:3wt%:5wt%:2wt%.

[0177] Example 32: The difference from Example 30 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 55wt%:30wt%:5wt%:3wt%:5wt%:2wt%.

[0178] Comparative Example 14: The difference from Example 18 is that: LiC 11 H 19 The molar ratio of O2, La(C5H7O2)3·4H2O and Zr(C5H7O2)4 is 8:2.5:2.

[0179] Comparative Example 15: The difference from Example 18 is that: LiC 11 H 19 The molar ratio of O2, La(C5H7O2)3·4H2O and Zr(C5H7O2)4 is 15:2.5:2.

[0180] Comparative Example 16: The difference from Example 22 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 70wt%:24wt%:3wt%:3wt%.

[0181] Comparative Example 17: The difference from Example 22 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 90wt%:4wt%:3wt%:3wt%.

[0182] Comparative Example 18: The difference from Example 25 is that the mass ratio of nano-Ga-LLZO particles to LFP is 3wt%:7wt%.

[0183] Comparative Example 19: The difference from Example 25 is that the mass ratio of nano-Ga-LLZO particles to LFP is 0.2wt%:9.8wt%.

[0184] Comparative Example 20: The difference from Example 25 is that the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 90wt%:5wt%:5wt%.

[0185] Comparative Example 21: The difference from Example 25 is that the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 99wt%:0.5wt%:0.5wt%.

[0186] Comparative Example 22: The difference from Example 30 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 25wt%:60wt%:5wt%:3wt%:5wt%:2wt%.

[0187] Comparative Example 23: The difference from Example 30 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 65wt%:20wt%:5wt%:3wt%:5wt%:2wt%.

[0188] The electrochemical performance tests were performed on the solid-state secondary batteries prepared in the above examples and comparative examples, and the test results were summarized and recorded in Table 2.

[0189] Table 2

[0190]

[0191] Referring to the experimental data in Table 2, it can be seen that from the electrochemical performance tests of Examples 18 to 32 and Comparative Examples 14 to 23, the solid electrolyte provided in the embodiments of the present application can optimize the rate capacity and initial capacity.

[0192] Correspondingly, another embodiment of the present application provides a method for preparing a solid electrolyte, which is different from the above embodiment in that array columns and branches are not formed, and the structure of the obtained solid electrolyte layer is different. The technical features that are the same as or corresponding to the above embodiment will not be described in detail here.

[0193] Figure 11 This is a ninth structural schematic diagram of a solid-state secondary battery provided in one embodiment of the present application.

[0194] refer to Figure 11 The preparation method includes: providing a substrate layer 300; the process steps of forming a second coating slurry include: uniformly stirring an active material, nano-inorganic ceramic oxide particles, a conductive agent, an adhesive and a dispersion solution to obtain a second mixed solution; dispersing the second mixed solution at high speed under negative pressure for 4h~6h to obtain a coating slurry, the viscosity of the coating slurry ranges from 5000mPa·s to 20000mPa·s, and the particle size is less than 20μm; wherein the mass ratio of the active material, nano-inorganic ceramic oxide particles, the conductive agent and the adhesive is (73wt%~93wt%): (5wt%~18wt%): (0.6wt%~4.5wt%): (1.4wt%~4.5wt%).

[0195] LFP, nano-LLZO particles, carbon black, PVDF are mixed according to (73wt%-93wt%):(5wt%-18wt%):(0.6wt%-4.5wt%):(1.4wt%-4.5wt%), then NMP is added to make the solid content of the slurry reach 60%, and the slurry is dispersed at high speed under negative pressure for 5h to obtain a mixed slurry, the viscosity of the slurry is in the range of 5000mPa·s-20000mPa·s, and the fineness is less than 20μm. The mixed slurry is pumped into a buffer tank and enters the coating die through the conveying pipeline, and is coated on the LLZO solid electrolyte sheet (i.e. substrate layer 300) at a coating speed of 5m / min. The coated sheet is transported by a belt into a multi-section oven, and the oven temperature is set in the range of 80℃-130℃. After the slurry is dried, due to the self-aggregation tendency of nano-LLZO particles in the slurry, the LLZO particles in the coating layer exhibit the form of secondary spherical aggregates 302. The coating layer forms an active layer 301.

[0196] A positive electrode sheet and a negative electrode sheet are provided, and the active layer is part of the positive electrode active layer of the positive electrode sheet and / or the active layer is part of the negative electrode active layer of the negative electrode sheet; the negative electrode sheet, the solid electrolyte, and the positive electrode sheet are sequentially stacked and hot-pressed to obtain a bare battery cell, and the bare battery cell is placed in a battery shell, and then packaged to obtain a solid-state secondary battery.

[0197] Figure 12 A tenth structural schematic diagram of a solid-state secondary battery is provided for an embodiment of the present application.

[0198] Reference Figure 12 The preparation method comprises: providing a substrate layer 300; the active material is Ga-LLZO coated active material; the process steps for forming the active material layer comprise: uniformly stirring Ga-LLZO particles, active particles, and a first dispersion solution to form a first mixed solution; drying the first mixed solution to form a first precursor; calcining the first precursor to form Ga-LLZO coated active material; wherein the mass ratio of Ga-LLZO particles to active particles is (0.5wt%-2wt%):(8wt%-9.5wt%). If the active material is a positive electrode active material, the active material can be a lithium source material; if the active material is a negative electrode active material, the active material can be graphite.

[0199] The nano Ga-LLZO particles and the LFP are added into the NMP solvent in a ratio of (0.5wt%-2wt%):(8wt%-9.5wt%), uniformly mixed, dried to remove the NMP, calcined at 700°C for 30min-60min, and a Ga-LLZO coated LFP structure is formed. The Ga-LLZO coated LFP structure, carbon black, and PVDF are mixed in a ratio of (92wt%-98wt%):(0.6wt%-4wt%):(1.4wt%-4wt%), and then NMP is added to make the slurry solid content reach 60%. After stirring for 3h-5h under negative pressure, an LFP slurry is obtained. The LLZO solid electrolyte sheet is used as a base material layer, and the LFP slurry is extrusion coated, and after drying, a surface-coated form of the intercalation structure is obtained. The surface-coated form of the structure is Ga-LLZO coated active material 303.

[0200] A positive electrode sheet and a negative electrode sheet are provided, the active layer is part of the positive electrode active layer of the positive electrode sheet and / or the active layer is part of the negative electrode active layer of the negative electrode sheet; the negative electrode sheet, the solid-state electrolyte, and the positive electrode sheet are sequentially stacked and hot-pressed to obtain a bare battery cell, and the bare battery cell is placed in a battery shell, and then packaged to obtain a solid-state secondary battery.

[0201] Figure 13 A eleventh structure schematic diagram of a solid-state secondary battery is provided for an embodiment of the present application.

[0202] Reference Figure 13 The preparation method comprises: providing a base material layer 100; the active material is graphite; after the solid-state electrolyte is formed, the method further comprises: uniformly stirring a lithium bisfluorosulfonylimide salt, poly(ethylene glycol) methacrylate, polyethylene glycol dimethacrylate, a photoinitiator, graphite, and conductive carbon black to obtain a curing liquid; immersing the solid-state electrolyte in the curing liquid and performing curing treatment on the solid-state electrolyte with the curing liquid; wherein the mass ratio of the lithium bisfluorosulfonylimide salt:poly(ethylene glycol) methacrylate:polyethylene glycol dimethacrylate:photoinitiator:graphite:conductive carbon black is (35wt%-55wt%):(30wt%-50wt%):(1wt%-7.5wt%):(1.5wt%-4.5wt%):(2wt%-7wt%):(1wt%-3wt%).

[0203] Graphite, carbon black, CMC, and SBR were mixed in pure water in a ratio of (92wt%-96wt%): (1wt%-3wt%): (0.5wt%-2.5wt%): (1.5wt%-3.5wt%) to a slurry with a solids content of 50%. Stirring was performed under negative pressure for 3 hours to obtain a graphite slurry. The graphite slurry was extrusion-coated onto an LLZO solid electrolyte sheet as the substrate layer 300. After drying, a graphite-coated solid electrolyte sheet was obtained. The solid electrolyte sheet was immersed in the curing solution and allowed to stand for 30-60 minutes. In the curing solution, the mass ratios of lithium bis(fluorosulfonyl)imide salt: poly(ethylene glycol) methacrylate: polyethylene glycol dimethacrylate: photoinitiator: graphite: conductive carbon black are (35wt%-55wt%): (30wt%-50wt%): (1wt%-7.5wt%): (1.5wt%-4.5wt%): (2wt%-7wt%): (1wt%-3wt%). After standing, the solid electrolyte sheet is removed and cured under UV light for 3-6 minutes to form an interlocking intercalated structure in the form of a cross-network. The cross-network refers to the interpenetrating interlaced network of PEG-based polymer networks 304 (i.e., a polymer composed of poly(ethylene glycol) methacrylate: polyethylene glycol dimethacrylate) and graphite / carbon black conductive pathways 305.

[0204] A positive electrode sheet and a negative electrode sheet are provided, and the active layer is the positive electrode active layer of the positive electrode sheet; the negative electrode sheet, the solid electrolyte and the positive electrode sheet are stacked and hot-pressed in sequence to obtain a bare battery cell, the bare battery cell is placed in a battery shell, and then packaged to obtain a solid-state secondary battery.

[0205] Example 33: The preparation steps of the active layer 101 are to mix LFP, nano-LLZO particles, carbon black, and PVDF in the proportion of 80wt%: 14wt%: 3wt%: 3wt%, and then add NMP to make the solid content of the slurry reach 60%, and disperse at high speed under negative pressure for 5 hours to obtain a mixed slurry with a slurry viscosity range of 10000mPa·s and a fineness of less than 20μm; coating: pump the mixed slurry into the buffer tank, enter the coating die through the feed pipe, and coat it on the LLZO solid electrolyte sheet at a coating speed of 5m / min. The coated sheet is transported by conveyor belt into a multi-section oven, and the oven temperature setting range is 80℃~130℃. After the slurry is dried, the self-aggregation tendency of the nano-LLZO particles in the slurry is as follows Figure 10 structure.

[0206] A positive electrode sheet and a negative electrode sheet are provided, wherein the active layer is a part of the positive electrode active layer of the positive electrode sheet and / or the active layer is a part of the negative electrode active layer of the negative electrode sheet; the negative electrode sheet, the solid electrolyte and the positive electrode sheet are stacked and hot-pressed in sequence to obtain a bare battery cell, the bare battery cell is placed in a battery shell, and then packaged to obtain a solid-state secondary battery.

[0207] Example 34: The difference from Example 33 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 76wt%:18wt%:3wt%:3wt%.

[0208] Example 35: The difference from Example 33 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 89wt%:5wt%:3wt%:3wt%.

[0209] Example 36: Add nano-Ga-LLZO particles and LFP to NMP solvent in a ratio of 1wt%:9wt%, mix evenly, dry to remove NMP, and calcine at 700°C for 30 minutes to form a Ga-LLZO-coated LFP structure. The Ga-LLZO-coated LFP structure, carbon black, and PVDF are mixed in a ratio of 94wt%:3wt%:3wt%, and then NMP is added to make the solid content of the slurry reach 60%. Stir for 3 hours under negative pressure to obtain LFP slurry. Using the LLZO solid electrolyte sheet as the substrate layer, extrusion-coated LFP slurry, and drying to obtain a surface-coated interlocking structure, that is, Figure 11 structure.

[0210] A positive electrode sheet and a negative electrode sheet are provided, and the active layer is the positive electrode active layer of the positive electrode sheet; the negative electrode sheet, the solid electrolyte and the positive electrode sheet are stacked and hot-pressed in sequence to obtain a bare battery cell, the bare battery cell is placed in a battery shell, and then packaged to obtain a solid-state secondary battery.

[0211] Example 37: The difference from Example 36 is that the mass ratio of nano-Ga-LLZO particles to LFP is 2wt%:8wt%.

[0212] Example 38: The difference from Example 36 is that the mass ratio of nano-Ga-LLZO particles to LFP is 0.5wt%:9.5wt%.

[0213] Example 39: The difference from Example 36 is that the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 98wt%:0.6wt%:1.4wt%.

[0214] Example 40: The difference from Example 36 is that the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 92wt%:4wt%:4wt%.

[0215] Example 41:

[0216] In pure water, graphite, carbon black, CMC, and SBR are mixed in a ratio of 94wt%: 2wt%: 1.5wt%: 2.5wt% to make the solid content of the slurry reach 50%. Stir under negative pressure for 3 hours to obtain graphite slurry. Using LLZO solid electrolyte sheet as the substrate layer, extrusion-coated graphite slurry is applied, and after drying, a solid electrolyte sheet coated with graphite is obtained. The above solid electrolyte sheet is immersed in the curing liquid and allowed to stand for 30 minutes. In the curing liquid, the mass ratio of LiFSI: PEGMA: PEGDMA: D1173: graphite: SP is 45wt%: 40wt%: 5wt%: 3wt%: 5wt%: 2wt%. After standing, the solid electrolyte sheet is taken out and cured under UV for 3 minutes to obtain an interlaced interlocking structure in the form of a cross network, that is, Figure 9 structure.

[0217] A positive electrode sheet and a negative electrode sheet are provided, and the active layer is the positive electrode active layer of the positive electrode sheet; the negative electrode sheet, the solid electrolyte and the positive electrode sheet are stacked and hot-pressed in sequence to obtain a bare battery cell, the bare battery cell is placed in a battery shell, and then packaged to obtain a solid-state secondary battery.

[0218] Example 42: The difference from Example 41 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 35wt%:50wt%:5wt%:3wt%:5wt%:2wt%.

[0219] Example 43: The difference from Example 41 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 55wt%:30wt%:5wt%:3wt%:5wt%:2wt%.

[0220] Comparative Example 24: The difference from Example 33 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 70wt%:24wt%:3wt%:3wt%.

[0221] Comparative Example 25: The difference from Example 33 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 90wt%:4wt%:3wt%:3wt%.

[0222] Comparative Example 26: The difference from Example 36 is that the mass ratio of nano-Ga-LLZO particles to LFP is 3wt%:7wt%.

[0223] Comparative Example 27: The difference from Example 36 is that the mass ratio of nano-Ga-LLZO particles to LFP is 0.2wt%:9.8wt%.

[0224] Comparative Example 28: The difference from Example 36 is that the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 90wt%:5wt%:5wt%.

[0225] Comparative Example 29: The difference from Example 36 is that the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 99wt%:0.5wt%:0.5wt%.

[0226] Comparative Example 30: The difference from Example 41 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 25wt%:60wt%:5wt%:3wt%:5wt%:2wt%.

[0227] Comparative Example 31: The difference from Example 41 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 65wt%:20wt%:5wt%:3wt%:5wt%:2wt%.

[0228] The electrochemical performance tests were performed on the solid-state secondary batteries prepared in the above examples and comparative examples, and the test results were summarized and recorded in Table 3.

[0229] Table 3

[0230]

[0231] Referring to the experimental data in Table 3, it can be seen that from the electrochemical performance tests of Examples 33 to 43 and Comparative Examples 24 to 31, the solid electrolyte provided in the embodiments of the present application can optimize the rate capacity and initial capacity.

[0232] According to some embodiments of the present application, another aspect of the embodiments of the present application provides an energy storage system, including: a secondary battery prepared by the method for preparing a solid-state secondary battery as in any of the above embodiments or a solid-state secondary battery as in the above embodiments.

[0233] According to some embodiments of the present application, on the other hand, embodiments of the present application provide an electrical device, including: a solid-state secondary battery prepared by the secondary battery preparation method of any of the above embodiments, a solid-state secondary battery as in the above embodiments, or an energy storage system as in the above embodiments.

[0234] Those skilled in the art will appreciate that the above-described embodiments are specific examples for implementing the present application, and that in actual applications, various changes in form and detail may be made thereto without departing from the spirit and scope of the present application. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined in the claims.

Claims

1. A method for preparing a solid-state secondary battery, characterized in that: include: Forming a solid electrolyte, including: preparing a ceramic aerosol, wherein the ceramic aerosol comprises inorganic ceramic oxide particles and polyimide particles; Providing a substrate layer, and spraying the ceramic aerosol onto at least one side of the substrate layer; heat-treating the substrate layer to remove the polyimide particles, and converting the remaining inorganic ceramic oxide particles into a plurality of branches, with gaps between adjacent branches, and the branches being located on at least one side of the substrate layer; preparing a coating slurry; Applying the coating slurry on one side of the substrate layer, and the coating slurry also flows into the gap; Performing a drying process, the coating slurry is converted into an active layer, and the substrate layer and the branches together constitute the solid electrolyte; Prepare a positive electrode sheet and a negative electrode sheet, wherein the steps of preparing at least one of the positive electrode sheet and the negative electrode sheet include: providing a current collector, wherein the active layer is located between the current collector and the substrate layer; The negative electrode sheet, the solid electrolyte and the positive electrode sheet are stacked in sequence and hot-pressed to obtain a bare cell, the bare cell is placed in a battery shell, and then packaged to obtain a solid-state secondary battery.

2. The method for preparing a solid-state secondary battery according to claim 1, wherein: The branches have holes in them, and the coating slurry flows into the holes.

3. The method for preparing a solid-state secondary battery according to claim 2, wherein: Before the drying process, the method further includes: ultrasonic treatment, wherein the ultrasonic treatment is used to fill the pores with the coating slurry; the ultrasonic treatment time is 3 minutes to 15 minutes; and the frequency is 20 kHz to 5 MHz.

4. The method for preparing a solid-state secondary battery according to claim 2, wherein: The coating slurry includes a dispersion solution, and the dispersion solution includes a wetting aid. The wetting aid is used to make the coating slurry flow into the holes.

5. The method for preparing a solid-state secondary battery according to claim 1, wherein: In the step of preparing the ceramic aerosol, the volume ratio of the inorganic ceramic oxide particles to the polyimide particles is 1:(1-10); the process parameters of the heat treatment include: a reaction temperature of 500°C to 1000°C, a calcination time of 0.8h to 1.2h, and a purge gas purge rate of 0.5L / min to 3L / min.

6. The method for preparing a solid-state secondary battery according to claim 1, wherein: The coating slurry includes an active material, and the surface of the active material is coated with Ga-LLZO; The process steps for forming the active material include: Stirring the Ga-LLZO particles, active particles, and solution to form a first mixed solution; drying the first mixed solution to form a first precursor; calcining the first precursor to form the active material; Among them, the mass ratio of Ga-LLZO particles and active particles is (0.5wt%~2wt%): (8wt%~9.5wt%).

7. The method for preparing a solid-state secondary battery according to claim 1, wherein: The process steps for forming the coating slurry include: Stirring the active material, nano inorganic ceramic oxide particles, conductive agent, adhesive and dispersion solution to obtain a second mixed solution; Dispersing the second mixed solution at high speed under negative pressure for 4 hours to 6 hours to obtain the coating slurry, wherein the viscosity of the coating slurry is in the range of 5000 mPa·s to 20000 mPa·s; Among them, the mass ratio of the active material, nano inorganic ceramic oxide particles, conductive agent and adhesive is (73wt%~93wt%): (5wt%~18wt%): (0.6wt%~4.5wt%): (1.4wt%~4.5wt%).

8. The method for preparing a solid-state secondary battery according to claim 1, wherein: The coating slurry includes an active material, wherein the active material is graphite; and after forming the solid electrolyte, the method further includes: Stirring bis(fluorosulfonyl)imide lithium salt, poly(ethylene glycol) methacrylate, polyethylene glycol dimethacrylate, a photoinitiator, graphite, and conductive carbon black to obtain a solidifying solution; Immersing the solid electrolyte in the solidifying liquid to solidify the solid electrolyte; Among them, the mass ratio of lithium bis(fluorosulfonyl)imide salt: poly(ethylene glycol) methacrylate: polyethylene glycol dimethacrylate: photoinitiator: graphite: conductive carbon black is (35wt%~55wt%): (30wt%~50wt%): (1wt%~7.5wt%): (1.5wt%~4.5wt%): (2wt%~7wt%): (1wt%~3wt%).

9. The method for preparing a solid-state secondary battery according to claim 1, wherein: The current collector is a positive electrode current collector, and the process steps for preparing the positive electrode sheet include: providing a positive electrode current collector, the positive electrode current collector is located on the surface of the active layer, hot pressing the solid electrolyte and the positive electrode current collector, and the active layer and the positive electrode current collector constitute the positive electrode sheet.

10. A solid-state secondary battery prepared by the method for preparing a solid-state secondary battery according to any one of claims 1 to 9, characterized in that: include: a battery case, wherein the battery case has a cavity therein; A bare cell, wherein the bare cell is located in the cavity; the bare cell comprises a stacked positive electrode sheet, a solid electrolyte and a negative electrode sheet, wherein the solid electrolyte comprises: a substrate layer and a plurality of branches, with gaps between adjacent branches, and the branches are located on at least one side of the substrate layer; an active layer, wherein the active layer is located on the surface of the substrate layer and in the gaps; the active layer is located between the substrate layer and the positive electrode current collector, and / or, the active layer is located between the substrate layer and the negative electrode current collector.

11. The solid-state secondary battery according to claim 10, characterized in that: The branches have holes, and part of the active layer is embedded in the holes.

12. The solid-state secondary battery according to claim 10, characterized in that: The active layer includes Ga-LLZO coated active materials.

13. An energy storage system, characterized in that: include: A solid-state secondary battery prepared by the method for preparing a solid-state secondary battery according to any one of claims 1 to 9, or a solid-state secondary battery according to claims 10 to 12.

14. An electrical device, characterized in that: include: A solid-state secondary battery prepared by the method for preparing a solid-state secondary battery according to any one of claims 1 to 9, a solid-state secondary battery according to claims 10 to 12, or an energy storage system according to claim 13.

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