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

Abstract

The invention relates to the field of batteries, and provides a solid-state secondary battery and a preparation method thereof, an energy storage system and electric equipment, and the preparation method comprises the following steps: preparing ceramic aerosol which comprises inorganic ceramic oxide particles and polyimide particles; providing a base material layer, and spraying the ceramic aerosol to at least one side of the base material layer; the base material layer is subjected to heat treatment, the polyimide particles are removed, the remaining inorganic ceramic oxide particles are converted into a plurality of branches, gaps are formed between the adjacent branches, and the branches are located on at least one side of the base material layer; coating one side of the base material layer with coating slurry, wherein the coating slurry also flows into the gap; drying treatment is carried out, the coating slurry is converted into an active layer, and the base material layer and the branches jointly form a solid electrolyte; at least one of the preparation steps of the positive plate and the negative plate comprises the following steps: providing a current collector, and positioning the active layer between the current collector and the base material layer; and packaging to obtain the solid-state secondary battery.

Description

Technical Field

[0001] This application relates to the field of batteries, and particularly to a solid-state secondary battery, a preparation method thereof, an energy storage system, and an electrical device. Background Art

[0002] Lithium secondary batteries are the main chemical power source systems in various application scenarios such as power and energy storage at present, and have obvious advantages in terms of specific energy, service life, cost performance, etc. However, the contradiction between specific energy and safety and the constraint of lithium resources have triggered a research and development boom for various new secondary batteries. Among them, solid-state lithium batteries and sodium batteries have become the most powerful competitors of current lithium-ion batteries.

[0003] Solid electrolytes can fundamentally improve the safety of secondary batteries and can effectively improve the energy density of batteries. Electrode materials need to meet the requirements of multi-faceted matching in chemistry, mechanics, heat, and electrochemical processes with electrolyte materials. Through the modification of electrode active substances, electrolytes, and interfaces, the performance of batteries can be improved and optimized. However, there are still some problems in the application of current solid-state secondary batteries. For example, the solid-solid interface contact between the electrolyte and the active material is poor, which affects characteristics such as the internal resistance of the battery. Summary of the Invention

[0004] Embodiments of this application provide a solid-state secondary battery, a preparation method thereof, an energy storage system, and an electrical device, which are at least beneficial to 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 this application, on the one hand, a preparation method of a solid-state secondary battery provided by the embodiments of this application includes: forming a solid electrolyte, including: preparing a ceramic aerosol, where 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; performing heat treatment on the substrate layer to remove the polyimide particles, and the remaining inorganic ceramic oxide particles are transformed into multiple branches, with gaps between adjacent branches, and the branches are located on at least one side of the substrate layer; preparing a coating slurry; coating the coating slurry on one side of the substrate layer, and the coating slurry also flows into the gaps; performing a drying treatment, and the coating slurry is transformed into an active layer, and the substrate layer and the branches together constitute the solid 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 include: providing a current collector, and the active layer is located between the current collector and the substrate layer; stacking the negative electrode sheet, the solid electrolyte, and the positive electrode sheet in sequence and performing hot pressing to obtain a bare battery core, putting the bare battery core into a battery case, and then encapsulating to obtain a solid-state secondary battery.

[0006] In some embodiments, the branch has holes therein, and the coating slurry also flows into the holes.

[0007] In some embodiments, before the drying treatment, it further includes: ultrasonic treatment, which is used to make the coating slurry fill the holes; the time of the ultrasonic treatment is 3 min to 15 min; the frequency is 20 kHz to 5 MHz.

[0008] In some embodiments, the coating slurry includes a dispersion solution, and the dispersion solution includes a wetting aid, which is used to make the coating slurry flow 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); the process parameters of the heat treatment include: the reaction temperature is 500 °C to 1000 °C, the calcination time is 0.8 h to 1.2 h, and the purge rate of the purge gas is 0.5 L / min to 3 L / min.

[0010] In some embodiments, the coating slurry includes an active material, and the surface of the active material is coated with Ga-LLZO; 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; wherein, the mass ratio of the Ga-LLZO particles to the active particles is (0.5 wt% - 2 wt%):(8 wt% - 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; highly dispersing the second mixed solution under negative pressure for 4 h to 6 h to obtain the coating slurry, and the viscosity range of the coating slurry is 5000 mPa·s to 20000 mPa·s; wherein, the ratio of the active material, nano-inorganic ceramic oxide particles, conductive agent, and binder is (73 wt% - 93 wt%):(5 wt% - 18 wt%):(0.6 wt% - 4.5 wt%):(1.4 wt% - 4.5 wt%).

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

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

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

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

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

[0017] According to some embodiments of the present application, on the other hand, the present application provides an energy storage system, including: a secondary battery prepared by the method for preparing a solid-state secondary battery according to any one of the above embodiments or the solid-state secondary battery according to the above embodiments.

[0018] According to some embodiments of the present application, on the other hand, an electrical device is provided, including: a solid-state secondary battery prepared by the method for preparing a secondary battery as described in any one 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 solutions provided by the embodiments of the present application have at least the following advantages: For the solid-state secondary battery provided by the embodiments of the present application, 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 interleaved and intercalated with the solid electrolyte, and / or the negative electrode active layer of the negative electrode sheet can be interleaved and intercalated with the solid electrolyte, thereby increasing the contact area and reducing the internal resistance of the battery. Secondly, the aerosol process is used to form branches on the surface of the substrate layer, and then the active layer is formed, and the active layer is located in the gaps between the branches. The active layer can not only be used as the positive electrode active layer / negative electrode active layer, but also can be used 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 and the negative electrode sheet in the subsequent hot pressing step. Description of the Drawings

[0020] One or more embodiments are exemplarily illustrated by the figures in the corresponding drawings. These exemplary illustrations do not limit the embodiments unless otherwise stated. The figures in the drawings do not constitute a proportional limitation; in order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is a flowchart corresponding to a method for preparing a solid-state secondary battery provided by an embodiment of the present application; Figure 2 It is a first structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application; Figure 3 It is a top view of a solid electrolyte in a solid-state secondary battery provided by an embodiment of the present application; Figure 4 It is a second structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application; Figure 5 It is a third structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application; Figure 6The fourth structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application; Figure 7 The fifth structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application; Figure 8 The sixth structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application; Figure 9 The seventh structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application; Figure 10 The eighth structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application; Figure 11 The ninth structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application; Figure 12 The tenth structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application; Figure 13 The eleventh structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application.

[0022] Explanation of reference numerals: 1, positive electrode sheet; 2, negative electrode sheet; 110, branches; 100, substrate layer; 101, active layer; 102, secondary spherical aggregates; 103, Ga-LLZO-coated active material; 104, PEG-based polymer network; 105, graphite / carbon black conductive path; 210, array column; 200, substrate layer; 201, active layer; 202, secondary spherical aggregates; 203, Ga-LLZO-coated active material; 204, PEG-based polymer network; 205, graphite / carbon black conductive path; 300, substrate layer; 301, active layer; 302, secondary spherical aggregates; 303, Ga-LLZO-coated active material; 304, PEG-based polymer network; 305, graphite / carbon black conductive path. Detailed implementation manners

[0023] As can be seen from the background art, in current solid-state secondary batteries, there are problems such as poor solid-solid interface contact between the electrolyte and the active material, which affects battery internal resistance and other characteristics.

[0024] The solid secondary battery provided by the embodiments of the present application prepares a solid electrolyte, and the surface of the solid electrolyte has a plurality of branches. The plurality of branches are located between the positive electrode sheet and the substrate layer, and / or the plurality of 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 staggered and interpenetrated with the solid electrolyte, and the negative electrode active layer of the negative electrode sheet can be staggered and interpenetrated with the solid electrolyte, thereby increasing the contact area and reducing the internal resistance of the battery. Secondly, the aerosol process is used to form branches on the surface of the substrate layer, and then the active layer is formed, and the active layer is located in the gap between the branches. The active layer can not only be used as the positive electrode active layer / negative electrode active layer, but also as a contact enhancement layer, thereby improving the contact performance and forming a tight interface contact between the solid electrolyte layer and the positive electrode sheet and the negative electrode sheet in the subsequent rolling step.

[0025] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is more than two, unless otherwise clearly and specifically defined.

[0026] Referring to "embodiment" herein means that a specific feature, structure or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0027] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: there is A, there is both A and B, and there is B. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0028] In the description of the embodiments of the present application, the term "a plurality of" refers to more than two (including two). Similarly, "a plurality of groups" refers to more than two groups (including two groups), and "a plurality of sheets" refers to more than two sheets (including two sheets).

[0029] In the description of the embodiments of the present application, the orientation or positional relationship indicated by technical terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the embodiments of the present application.

[0030] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "coupling", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0031] In the drawings corresponding to the embodiments of the present application, for better understanding and convenience of description, the thickness and area of the layer are enlarged. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component can be "directly" on the surface of the other component, or there can be a third component between the two components. On the contrary, when describing a component on the surface of another component or when another component is 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 "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 on a partial edge of the entire surface.

[0032] In the description of the embodiments of the present application, when a certain component "includes" another component, unless otherwise specified, other components are not excluded, and other components may further be included. In addition, when a component such as a layer, film, region, or plate is referred to as "on / at" another component, it can be "directly on" the other component (that is, on the surface of the other component and there is no other component between them), or there can be another component between them. In addition, when a layer, film, region, plate, etc. component is "directly located on" another component, or when a layer, film, region, plate, etc. component is located on the surface of another component, it means that there is no other component between them.

[0033] The terms used in the description of the various embodiments herein are for the purpose of describing particular embodiments only and are not intended to be limiting. As used in the description of the various embodiments and the appended claims, "the part" is also intended to include the plural form unless the context clearly indicates otherwise. Among them, the component includes components such as layers, films, regions, or plates.

[0034] The embodiments of the present application will be described in detail below with reference to the accompanying drawings. However, those of ordinary skill in the art can understand that in the embodiments of the present application, many technical details are provided to help readers better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0035] According to some embodiments of the present application, on the one hand, a method for preparing a solid-state secondary battery is provided to improve the problems that the solid-solid interface contact between the electrolyte and the active material is poor, affecting the characteristics such as the internal resistance of the battery.

[0036] Figure 1 It is a flowchart corresponding to a method for preparing a solid-state secondary battery provided in an embodiment of the present application; Figure 2 It is a first structural schematic diagram of a solid-state secondary battery provided in an embodiment of the present application; Figure 3 It is a top view of a solid-state electrolyte in a solid-state secondary battery provided in an embodiment of the present application.

[0037] It should be noted that Figure 2 It is the direction from the top cover looking at the housing, that is, the side surfaces of the positive electrode sheet, the negative electrode sheet, and the solid-state electrolyte can be seen, so that the cooperation relationship among the three can be clearly seen. Figure 2 shows the case where the active layer is the positive electrode active layer and the negative electrode active layer. Those skilled in the art can set only one side of the substrate layer with branches and the active layer according to requirements. Figure 3 The active layer in is a perspective view to see the arrangement relationship between the branches and the substrate layer.

[0038] Reference Figures 1 - 3, the 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; performing heat treatment on the substrate layer 100 to remove the polyimide particles, and the remaining inorganic ceramic oxide particles are transformed into a plurality of branches 110, there are gaps between adjacent branches 110, and the branches 110 are located on at least one side of the substrate layer 100; preparing a coating slurry; coating the coating slurry on one side of the substrate layer 100, and the coating slurry also flows into the gaps; performing a drying process, and the coating slurry is transformed into an active layer 101, and the substrate layer 100 and the branches 110 together constitute a solid electrolyte; preparing a positive electrode sheet 1 and a negative electrode sheet 2, 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 performing hot pressing to obtain a bare battery cell, putting the bare battery cell into a battery case, and then encapsulating to obtain a solid secondary battery.

[0039] The solid secondary battery provided by the embodiment of the present application, by preparing a solid electrolyte, and the surface of the solid electrolyte has a plurality of branches 110, the plurality of branches 110 are located between the positive current collector and the substrate layer 100, and / or the plurality of branches 110 are located between the negative current collector and the substrate layer 100, so that the positive active layer of the positive electrode sheet 1 can be staggered and interpenetrated with the solid electrolyte, and the negative active layer of the negative electrode sheet 2 can be staggered and interpenetrated with the solid electrolyte, thereby increasing the contact area and reducing the internal resistance of the battery. Secondly, the branches 110 are formed by an aerosol process, so that the surface of the substrate layer 100 forms the branches 110, and then the active layer 101 is formed, and the active layer 101 is located in the gaps between the branches 110. The active layer 101 can not only be used as the positive active layer / negative active layer, but also can be used as a contact enhancement layer, thereby improving the contact performance and forming a tight interface contact between the solid electrolyte layer and the positive electrode sheet 1 and the negative electrode sheet 2 in the subsequent rolling step.

[0040] The above-provided preparation method will be described in detail below.

[0041] Classified by shape, the prepared solid-state secondary batteries can be divided into square cells, round cells or soft-pack cells. Classified by capacity, the secondary batteries can be divided into models such as 50Ah, 100Ah, 150Ah, 200Ah, 280Ah, 306Ah, 314Ah, 500+Ah, 800+Ah and 1000+Ah. Classified by the chemical composition and working principle of the bare cells of the secondary batteries, the secondary batteries can be lithium-ion batteries, lead-acid batteries, sodium-ion batteries or nickel-metal hydride batteries. In the embodiments of the present application, the preparation method of lithium-ion batteries is taken 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 according to actual needs. For example, for sodium-ion batteries, the lithium transition metal oxide of the positive active material in the following is replaced with any one of the corresponding layered metal oxides (such as NaFeO2), polyanionic compounds (NaFePO4) and Prussian blue compound systems (such as NaMnFe(CN)6-zH2O).

[0042] Solid-state electrolyte (abbreviated as SSE) is a solid ionic conductor and electronic insulating material, and is also an important characteristic component of solid-state secondary batteries. Compared with liquid electrolytes, solid-state electrolytes are safe, have no problem of leakage of toxic organic solvents, are not flammable, do not volatilize, have mechanical and thermal stability, are easy to process, have low self-discharge, and can achieve higher power density and cycle performance. For example, due to the characteristic of the solid-state electrolyte membrane to inhibit lithium dendrites, lithium metal anodes can be used in actual devices without being restricted by the inherent limitations of liquid electrolytes. By using high-capacity anodes and low reduction potentials, lighter, thinner and cheaper rechargeable batteries can be achieved.

[0043] Solid-state electrolytes include all-solid-state electrolytes and quasi-solid-state electrolytes (QSSE). All-solid-state electrolytes are further divided into inorganic solid electrolytes (ISE), solid polymer electrolytes (SPE) and composite polymer electrolytes (CPE). QSSE is also called gel polymer electrolyte (GPE), which is an independent membrane containing a certain amount of liquid components fixed in a solid matrix. The ion conduction mechanisms of SPE and GPE are quite different: SPE conducts ions by interacting with the substituents of the polymer chain, while GPE mainly conducts ions in solvents or plasticizers.

[0044] The solid electrolyte mainly consists of the following components: a lithium salt, which serves as an ion source and is one of lithium fluoride, lithium sulfide, or lithium phosphate; a matrix, which provides mechanical support and forms an ion transport channel, and the matrix is a polymer matrix, and the polymer matrix is a copolymer composed of one or a combination of polyethylene oxide, 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 the inorganic filler is a copolymer composed of one or a combination of lithium oxide, lithium titanate, lithium phosphate, aluminum oxide, and silicon oxide, and the inorganic filler is a nanoscale filler with a particle size of 1 nm to 100 nm; rare earth elements, which are used to increase the lithium ion conductivity of the solid electrolyte, and the rare earth elements are a copolymer composed of one or a combination of lanthanum, cerium, praseodymium, neodymium, gadolinium, erbium, lutetium, and yttrium; a ceramic material, which is used to enhance the toughness of the electrolyte, and the ceramic material is one of zirconia, silicon nitride, silicon dioxide, titanium disulfide, and lithium sulfide.

[0045] The preparation steps of the solid electrolyte include: mixing inorganic ceramic oxide particles with polyimide particles to obtain mixed particles. The inorganic ceramic oxide particles are a mixture composed of a lithium salt, an inorganic filler, rare earth elements, and a ceramic material. The polyimide particles are the interstitial structure in the subsequent formed branches 110. The polyimide particles undergo an imidization reaction during high-temperature curing, releasing small molecules (such as water), resulting in volume shrinkage. During the shrinkage process, the rigidity of the molecular chains hinders the uniform densification of the inorganic ceramic oxide particles, and local stress concentration promotes the formation of wrinkles or protrusions at the edges of the holes formed due to the sublimation of the polyimide particles, thereby forming an irregular array of columns, that is, the branches 110.

[0046] In some embodiments, the inorganic ceramic oxide particles may include LLTO (lithium lanthanum titanate, Li 0.33 La 0.56 TiO3), LLZTO (lithium lanthanum zirconate, Li7La3Zr2O 12 ), or LiTFSI (lithium bis(trifluoromethanesulfonyl)imide, C2F6LiNO4S2). The representative material of the NASICON (sodium superionic conductor) type solid electrolyte is LATP (lithium aluminum titanium phosphate, Li 1.3 Al 0.3 Ti 1.7 (PO4)3).

[0047] 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).

[0048] Prepare the mixed particles into ceramic aerosol, so that the sintering temperature of the subsequent preparation of solid electrolyte can be reduced to reduce the preparation cost; and the components in the prepared solid electrolyte are uniform and the interface is smooth.

[0049] Specifically: Use nitrogen (which can also be helium or oxygen, etc.) as the carrier gas, and input the mixed particles into the aerosol chamber through a gas delivery device to make the mixed particles in the aerosol chamber evenly dispersed and form ceramic aerosol.

[0050] Spray the ceramic aerosol on the substrate layer 100 to form a prepolymer layer. Specifically: Use the LLZTO solid electrolyte sheet as the substrate layer 100, set the deposition chamber pressure at 8 Pa to 12 Pa, the nozzle distance from the surface of the substrate layer at 9 mm to 11 mm, and the spraying angle at 85° to 95°; Use the carrier gas to spray the aerosol through the nozzle on the surface of the substrate layer 100, with the carrier gas flow rate of 20 L / min to 22 L / min and the deposition time of 1 h to 2 h. Obtain the solid electrolyte sheet with deposited mixed particles, that is, the prepolymer layer.

[0051] The mechanism of forming the prepolymer layer through aerosol is as follows: Divide the whole process into two stages: In the initial stage of deposition, with the collision of the first batch of original micro-nano particles and the substrate, a layer of anchoring layer is quickly formed on the substrate surface. However, the damage at the interface between the deposited film and the substrate will increase the roughness of the contact surface. After forming the initial anchoring layer, by reducing the carrier gas flow rate, the growth of the deposited film becomes slow. Then, in the second stage, the particles deposited on the anchoring layer gradually smooth and densify the surface. Through countless repetitions of continuous fragmentation, deformation, collision, etc. of the original particles, a dense deposited film (i.e., the prepolymer layer) is formed. This film-forming phenomenon is also called the room-temperature collision combination principle.

[0052] 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 optimizations of the conventional solid electrolyte sheet.

[0053] The heat treatment step can include: Place the substrate layer 100 containing the prepolymer layer in a high-temperature reaction kettle and calcine it at 900 °C for 1 h to 3 h to remove the polyimide particles, and at the same time fuse the inorganic ceramic oxide particles to form a substrate layer in the form of branches 110.

[0054] The mechanism is as follows: There are significant differences in density, particle size distribution, and surface energy between inorganic ceramic oxide particles and polyimide (PI) particles. Polyimide particles usually have thermal decomposition characteristics and serve as sacrificial templates, while inorganic ceramic oxide particles have high structural stability. When ceramic aerosol is deposited by high-speed spraying, the particles generate a "sputtering effect" due to inertial impact on the substrate layer 100. Large-sized particles are preferentially deposited to form local accumulations; small particles are filled into the gaps by air flow disturbance but are elastically hindered by PI particles, forming a "micro-region arch bridge" structure, resulting in an initial concave-convex morphology on the surface of the prepolymer layer. Further, when the PI particles are heat-treated at 300°C to 500°C, they undergo stepwise decomposition (releasing gases such as carbon dioxide and formaldehyde). The decomposition kinetics competes with the sintering behavior of ceramic particles. The gases generated by the decomposition of PI will escape along the gaps between ceramic particles, forming "branched pores" in the ceramic framework. The ceramic particles undergo surface sintering (neck growth) at high temperatures, while the volume of the PI decomposition region collapses. The difference in shrinkage rates between the two (the shrinkage rate of ceramics is about 3% - 5%, and the PI decomposition region > 20%) causes tensile stress concentration at the interface, forcing the edges of the pore walls to warp upward to form protrusions, namely the branches 110.

[0055] In some embodiments, the process parameters for heat treatment include: the reaction temperature is 500°C to 1000°C, the calcination time is 0.8 h to 1.2 h, and the purge rate of the purge gas is 0.5 L / min to 3 L / min.

[0056] The active material, conductive agent, binder, and dispersion solution are stirred evenly to obtain a coating slurry; the coating slurry is covered on one side of the substrate layer 100. Among them, the coating slurry will flow into the gaps between some of the branches 110, and after drying treatment, the coating slurry is converted into the active layer 101. The substrate layer 100 and the branches 110 together constitute a solid electrolyte.

[0057] 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. Taking the active layer as the positive electrode active material and the positive electrode active material as LFP (lithium iron phosphate) as an example. Referring to Figure 2 , LFP, carbon black, and PVDF are mixed in the ratio of (92 wt% - 98 wt%): (0.6 wt% - 4 wt%): (1.4 wt% - 4 wt%). Subsequently, NMP is added to make the solid content of the slurry reach 50%. Stir for 3 h under negative pressure to obtain the LFP slurry. Using the solid electrolyte layer as the substrate layer 100, the LFP slurry is coated with a doctor blade, and ultrasonic treatment for 5 min is used to promote the infiltration of the slurry between the branches 110, and then dried. Repeat the doctor blade coating - ultrasonic treatment - drying steps 3 times to obtain an interpenetrating structure in an irregular protrusion form, that is, the substrate layer 100 with branches 110.

[0058] In some embodiments, the branch 110 has holes inside, and the coating slurry flows into the holes; after drying treatment, a 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 electrolyte, and the active layer 101 is located in the holes, which can also improve the conductivity.

[0059] In some embodiments, the dispersion solution includes a wetting aid, and the wetting aid is used to make the coating slurry flow into the holes. In this way, the wetting aid can improve the wettability of the coating slurry to the solid electrolyte, thereby increasing the contact area between the coating slurry and the solid electrolyte, and thus improving the interfacial contact performance between the solid electrolyte and the active layer 101.

[0060] In some embodiments, before the drying treatment, it further includes: ultrasonic treatment, which is used to make the coating slurry fill the holes; the ultrasonic time of the ultrasonic treatment is 3 min to 15 min; the frequency of the ultrasonic wave is 20 kHz to 5 MHz. In this way, the contact performance between the active layer 101 and the solid electrolyte can be improved.

[0061] Figure 4 This is a second structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application. Figure 4 Only part of the solid electrolyte layer is shown, and the arrangement with the positive electrode sheet and the negative electrode sheet can be referred to Figure 2 For the following partial sectional views, reference can also be made Figure 2 .

[0062] In some embodiments, with reference to Figure 4 The process steps for forming the coating slurry include: uniformly stirring the active material, nano-inorganic ceramic oxide particles, conductive agent, binder, and dispersion solution to obtain a second mixed solution; dispersing the second mixed solution at high speed under negative pressure for 4 h to 6 h to obtain the coating slurry, and the viscosity range of the coating slurry is 5000 mPa·s to 20000 mPa·s; wherein, the mass ratio of the active material, nano-inorganic ceramic oxide particles, conductive agent, and binder is (73 wt% to 93 wt%): (5 wt% to 18 wt%): (0.6 wt% to 4.5 wt%): (1.4 wt% to 4.5 wt%).

[0063] Among them, the average particle size of the second mixed solution composed of the active material, nano-inorganic ceramic oxide particles, conductive agent, and binder in the coating slurry is less than 20 μm.

[0064] Taking the active layer as the cathode active material, the cathode active material is LFP as an example. LFP, nano-LLZO (lithium lanthanum zirconium oxide) particles, carbon black, and PVDF are mixed in the ratio of (73wt% - 93wt%):(5wt% - 18wt%):(0.6wt% - 4.5wt%):(1.4wt% - 4.5wt%). Subsequently, NMP is added to make the solid content of the slurry reach 60%, and it is dispersed at high speed under negative pressure for 5h to obtain a mixed slurry. The viscosity range of the slurry is 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 a feeding pipeline, and is coated on the LLZO solid electrolyte sheet at a coating speed of 5m / min. The coated sheet enters a multi-section oven through belt transportation, and the oven temperature is set in the range of 80°C - 130°C. 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 are transformed into secondary spherical aggregates 102.

[0065] The mechanism is as follows: Under negative pressure, high-speed dispersion is carried out for 5h. The hard agglomerates of LLZO nanoparticles are disassembled by shear force to make them temporarily uniformly dispersed. At this time, the PVDF molecular chains are fully extended in the NMP solvent, and part of them are adsorbed on the particle surface to form a steric hindrance layer, delaying re-aggregation. 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 particles, but at the same time also intensifies the "crowding effect" between particles, prompting the LLZO particles to pre-aggregate due to physical extrusion in local areas. In the subsequent drying step, the LLZO nanoparticles have a high surface energy. After the solvent volatilizes, the exposed particle surfaces tend to reduce the total surface area by aggregation to lower the free energy of the system, thus forming secondary spherical aggregates 102.

[0066] Figure 5 This is the third structural schematic diagram of a solid secondary battery provided by an embodiment of the present application.

[0067] Reference 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: 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 an active material coated with Ga-LLZO; wherein, the mass ratio of Ga-LLZO particles to active particles is (0.5wt% - 2wt%):(8wt% - 9.5wt%).

[0068] It should be noted that if the active material is a cathode active material, the active material can be a lithium source material; if the active material is an anode active material, the active material can be graphite.

[0069] Taking the active material as LFP as an example. Nano Ga-LLZO particles and LFP are added to the NMP solvent in a ratio of (0.5 wt% - 2 wt%) : (8 wt% - 9.5 wt%), mixed evenly, dried to remove NMP, and then calcined at 700 °C for 30 min - 60 min to form an LFP structure coated with Ga-LLZO. The Ga-LLZO-coated LFP structure, carbon black, and PVDF are mixed in a ratio of (92 wt% - 98 wt%) : (0.6 wt% - 4 wt%) : (1.4 wt% - 4 wt%), and then NMP is added to make the solid content of the slurry reach 60%. Stir for 3 h - 5 h under negative pressure to obtain the LFP slurry. Using the LLZO solid electrolyte sheet as the base layer, extrude and coat the LFP slurry, and after drying, obtain an interpenetrating structure in the form of surface coating. The structure in the form of surface coating is the active material 103 coated with Ga-LLZO.

[0070] Figure 6 This is the fourth structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application.

[0071] In some embodiments, referring to Figure 6 , the coating slurry includes an active material. The active material is graphite; after forming the solid electrolyte, it further includes: uniformly stirring lithium bis(fluorosulfonyl)imide salt, poly(ethylene glycol) methacrylate, polyethylene glycol dimethacrylate, photoinitiator, graphite, and conductive carbon black to obtain a curing solution; immersing the solid electrolyte in the curing solution and performing a curing treatment on the solid electrolyte with the curing solution; wherein, the mass ratio of lithium bis(fluorosulfonyl)imide salt : poly(ethylene glycol) methacrylate : polyethylene glycol dimethacrylate : photoinitiator : graphite : conductive carbon black is (35 wt% - 55 wt%) : (30 wt% - 50 wt%) : (1 wt% - 7.5 wt%) : (1.5 wt% - 4.5 wt%) : (2 wt% - 7 wt%) : (1 wt% - 3 wt%).

[0072] In pure water, graphite, carbon black, CMC, and SBR are mixed in the ratio of (92 wt% - 96 wt%):(1 wt% - 3 wt%):(0.5 wt% - 2.5 wt%):(1.5 wt% - 3.5 wt%) to make the solid content of the slurry reach 50%. Stir for 3 h under negative pressure to obtain the graphite slurry. Using the LLZO solid electrolyte sheet as the base layer, extrude and coat the graphite slurry, and after drying, obtain the solid electrolyte sheet coated with graphite. Immerse the above solid electrolyte sheet in the curing solution and let it stand for 30 min - 60 min. In the curing solution, the mass ratio of lithium bis(fluorosulfonyl)imide salt: poly(ethylene glycol) methacrylate: polyethylene glycol dimethacrylate: photoinitiator: graphite: conductive carbon black is (35 wt% - 55 wt%):(30 wt% - 50 wt%):(1 wt% - 7.5 wt%):(1.5 wt% - 4.5 wt%):(2 wt% - 7 wt%):(1 wt% - 3 wt%). After standing, take out the solid electrolyte sheet and cure it under UV for 3 min - 6 min to obtain an interpenetrating structure in the form of a cross-linked network.

[0073] The mechanism therein is as follows: The PEG-based polymer network 104 (i.e., the polymer composed of poly(ethylene glycol) methacrylate and polyethylene glycol dimethacrylate) interpenetrates with the graphite / carbon black conductive path 105 to form a bicontinuous phase structure. The polymer network conducts conductive ions, and the carbon black network conducts electrons (carbon black self-aggregates, and long-range conductive chain segments build a conductive network), improving the ion / electron conduction ability 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 the conductive material can improve the electron conductivity of the current collector.

[0074] In some embodiments, the active layer can be the active layer of the positive electrode sheet. Then the current collector is the positive electrode current collector, and the process steps for forming the positive electrode sheet include: providing the positive electrode current collector, the positive electrode current collector is located on the surface of the active layer 101, and performing hot pressing treatment on the solid electrolyte and the positive electrode current collector, and the active layer 101 and the positive electrode current collector constitute the positive electrode sheet 1.

[0075] In some embodiments, the active layer can be a partial active layer of the positive electrode sheet. The positive electrode sheet also has a positive electrode sub-active layer. The current collector is the positive electrode current collector, and the process steps for forming the positive electrode sheet include: preparing the positive electrode sub-active layer, the positive electrode sub-active layer is located on the surface of the active layer 101; providing the positive electrode current collector, the positive electrode current collector is located on the surface of the positive electrode sub-active layer, and performing hot pressing treatment on the solid electrolyte and the positive electrode current collector, and the positive electrode sub-active layer, the active layer 101 and the positive electrode current collector constitute the positive electrode sheet 1. The active layer 101 not only serves as the positive electrode active layer, but also can serve 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 hot pressing step.

[0076] Similarly, the active layer can serve as the active layer of the negative electrode sheet. Then the current collector is the negative electrode current collector, and the process steps for forming the negative electrode sheet include: providing the negative electrode current collector, the negative electrode current collector being located on the surface of the active layer 101, and performing hot pressing on the solid electrolyte and the negative electrode current collector. The active layer 101 and the negative electrode current collector constitute the negative electrode sheet 2.

[0077] In some embodiments, the active layer can serve as a partial active layer of the negative electrode sheet. The negative electrode sheet further has a negative electrode sub-active layer. The current collector is the negative electrode current collector, and the process steps for forming the negative electrode sheet include: preparing the negative electrode sub-active layer, the negative electrode sub-active layer being located on the surface of the active layer 101; providing the negative electrode current collector, the negative electrode current collector being located on the surface of the negative electrode sub-active layer, and performing hot pressing on the solid electrolyte and the negative electrode current collector. The negative electrode sub-active layer, the active layer 101, and the 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 can serve as a contact enhancement layer, thereby improving the contact performance and forming a tight interface contact between the solid electrolyte layer and the negative electrode sheet during the hot pressing step.

[0078] The preparation method further includes: welding the tab, welding the tab to the adapter piece, and connecting the other end of the adapter piece to the terminal post; engaging the top cover with the battery case. Wherein, the adapter piece is located in the chamber, and the terminal post passes through the top cover.

[0079] Wherein, the adapter piece at least includes a first adapter piece and a second adapter piece. The terminal post includes a positive terminal post and a negative connection post. The first adapter piece is electrically connected to the positive tab of the positive electrode sheet and the positive terminal post respectively, and the second adapter piece is electrically connected to the negative tab of the negative electrode sheet and the negative connection post respectively.

[0080] The preparation method of the solid-state secondary battery provided by the embodiments of the present application, by preparing the solid electrolyte, and having a plurality of branches 110 on the surface of the solid electrolyte, the plurality of branches 110 being located between the positive electrode current collector and the substrate layer 100, and / or the plurality of branches 110 being located between the negative electrode current collector and the substrate layer 100, enables the positive electrode active layer of the positive electrode sheet 1 to be interleaved and interpenetrated with the solid electrolyte, and the negative electrode active layer of the negative electrode sheet 2 to be interleaved and interpenetrated with the solid electrolyte, thereby increasing the contact area and reducing the internal resistance of the battery. Secondly, the 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, and 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 can serve as a contact enhancement layer, thereby improving the contact performance and forming a tight interface contact between the solid electrolyte layer and the positive electrode sheet 1 and the negative electrode sheet 2 during the subsequent rolling step.

[0081] According to some embodiments of the present application, on the other hand, an embodiment of the present application provides a solid-state secondary battery, including: a battery case with a cavity inside; a bare battery cell located in the cavity; the bare battery cell includes a stacked positive electrode sheet 1, a solid electrolyte, and a negative electrode sheet 2, wherein the solid electrolyte includes: a base material layer 100 and a plurality of branches 110, with a gap between adjacent branches 110, and the branches 110 are located on at least one side of the base material layer 100; an active layer 101 located on the surface of the base material layer 100 and in the gap; the active layer is located between the base material layer 100 and the positive current collector, and / or the active layer is located between the base material layer 100 and the negative current collector. Among them, the active layer located between the base material layer 100 and the positive current collector is a part of the positive active layer, and together with the positive current collector, it constitutes the positive electrode sheet 1; the active layer located between the base material layer 100 and the negative current collector is a part of the negative active layer, and together with the negative current collector, it constitutes the negative electrode sheet 2.

[0082] In some embodiments, the branches 110 have holes, and part of the active layer 101 is embedded in the holes.

[0083] In some embodiments, the active layer 101 includes an active material coated with Ga-LLZO.

[0084] Hereinafter, the beneficial effects of the embodiments of the present application will be further described in combination with examples and comparative examples.

[0085] Example 1: Mix LLZTO particles and PI particles evenly according to a volume ratio of 1:2 to obtain mixed particles. Use nitrogen as the carrier gas and input it into the aerosol chamber through a gas delivery device to make the mixed particles in the aerosol chamber evenly dispersed. Use an LLZTO solid electrolyte sheet as the base material layer, set the deposition chamber pressure to 10 Pa, the nozzle distance from the surface of the base material layer to be 10 mm, and the spraying angle to be 90°; use the carrier gas to spray the aerosol through the nozzle onto the surface of the base material layer 100, with the carrier gas flow rate of 20 L / min and the deposition time of 1 h. Obtain a prepolymer layer with deposited mixed particles. Place the prepolymer layer in a high-temperature reaction kettle and calcine it at 900 °C for 1 h to remove the PI particles and at the same time fuse the LLZTO particles to form a precursor with branches; mix LFP, carbon black, and PVDF in a ratio of 94 wt%: 3 wt%: 3 wt%, and then add NMP to make the solid content of the slurry reach 50%. Stir under negative pressure for 3 h to obtain an LFP slurry. Using the solid electrolyte layer as the base material layer, coat the LFP slurry with a scraper, and ultrasonicate for 5 min to promote the infiltration of the slurry between the array columns, and then dry. Repeat the scraping - ultrasonication - drying steps 3 times to obtain a solid electrolyte with branches.

[0086] 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, and the bare battery cell is placed in a battery case and then encapsulated to obtain a solid secondary battery.

[0087] Example 2: The difference from Example 1 is that the volume ratio of LLZTO particles to PI particles is 1:1.

[0088] Example 3: The difference from Example 1 is that the volume ratio of LLZTO particles to PI particles is 1:10.

[0089] 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.

[0090] Example 5: The difference from Example 1 is that the prepolymer layer is placed in a high-temperature reaction kettle and calcined at 500 °C for 1 h to remove PI particles, and at the same time, LLZTO particles are fused to form a substrate layer with branches.

[0091] Example 6: The difference from Example 1 is that the prepolymer layer is placed in a high-temperature reaction kettle and calcined at 1000 °C for 1 h to remove PI particles, and at the same time, LLZTO particles are fused to form a substrate layer with branches.

[0092] Example 7: The difference from Example 1 is that the preparation steps of the active layer 101 are as follows: LFP, nano-LLZO particles, carbon black, and PVDF are mixed in a ratio of 80 wt%: 14 wt%: 3 wt%: 3 wt%, and then NMP is added to make the solid content of the slurry reach 60%. It is dispersed at high speed under negative pressure for 5 h to obtain a mixed slurry. The viscosity range of the slurry is 10000 mPa·s, and the fineness is less than 20 μm; Coating: The mixed slurry is pumped into a buffer tank, enters the coating die head through a feeding pipeline, and is coated on the LLZO solid electrolyte sheet. The coating speed is 5 m / min. The coated sheet is transported by the running belt into a multi-section oven, and the oven temperature is set in the range of 80 °C to 130 °C. After the slurry is dried, the self-aggregation tendency of nano-LLZO particles in the slurry is as Figure 4 of the structure.

[0093] Example 8: The difference from Example 7 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 76 wt%: 18 wt%: 3 wt%: 3 wt%.

[0094] Example 9: The difference from Example 7 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 89 wt%: 5 wt%: 3 wt%: 3 wt%.

[0095] Example 10: The nano Ga-LLZO particles and LFP were added to the NMP solvent in a ratio of 1 wt%:9 wt%, mixed evenly, dried to remove NMP, and then calcined at 700 °C for 30 min to form an LFP structure coated with Ga-LLZO. The LFP structure coated with Ga-LLZO, carbon black, and PVDF were mixed in a ratio of 94 wt%:3 wt%:3 wt%, and then NMP was added to make the solid content of the slurry reach 60%. Stir for 3 h under negative pressure to obtain the LFP slurry. Using the LLZO solid electrolyte sheet as the substrate layer, the LFP slurry was extrusion-coated, and after drying, an interpenetrating structure in the form of surface coating was obtained, that is Figure 5 structure.

[0096] Example 11: The difference from Example 10 is that the mass ratio of nano Ga-LLZO particles to LFP is 2 wt%:8 wt%.

[0097] Example 12: The difference from Example 10 is that the mass ratio of nano Ga-LLZO particles to LFP is 0.5 wt%:9.5 wt%.

[0098] Example 13: The difference from Example 10 is that the mass ratio of the LFP structure coated with Ga-LLZO, carbon black, and PVDF is 98 wt%:0.6 wt%:1.4 wt%.

[0099] Example 14: The difference from Example 10 is that the mass ratio of the LFP structure coated with Ga-LLZO, carbon black, and PVDF is 92 wt%:4 wt%:4 wt%.

[0100] Example 15: In pure water, graphite, carbon black, CMC, and SBR were mixed in a ratio of 94 wt%:2 wt%:1.5 wt%:2.5 wt% to make the solid content of the slurry reach 50%. Stir for 3 h under negative pressure to obtain the graphite slurry. Using the LLZO solid electrolyte sheet as the substrate layer, the graphite slurry was extrusion-coated, and after drying, a solid electrolyte sheet coated with graphite was obtained. The above solid electrolyte sheet was immersed in the curing solution and left standing for 30 min. In the curing solution, the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 45 wt%:40 wt%:5 wt%:3 wt%:5 wt%:2 wt%. After standing, the solid electrolyte sheet was taken out and cured under UV for 3 min to obtain an interpenetrating structure in the form of a cross network, that is Figure 6 structure.

[0101] Example 16: The difference from Example 15 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 35 wt%:50 wt%:5 wt%:3 wt%:5 wt%:2 wt%.

[0102] Example 17: The difference from Example 15 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 55 wt%:30 wt%:5 wt%:3 wt%:5 wt%:2 wt%.

[0103] Comparative Example 1: The solid electrolyte is an LLZTO solid electrolyte sheet.

[0104] Comparative Example 2: The difference from Example 1 is that the volume ratio of LLZTO particles to PI particles is 1:0.1.

[0105] Comparative Example 3: The difference from Example 1 is that the volume ratio of LLZTO particles to PI particles is 1:20.

[0106] Comparative Example 4: The difference from Example 1 is that the temperature of the reaction kettle is 300 °C.

[0107] Comparative Example 5: The difference from Example 1 is that the temperature of the reaction kettle is 1500 °C.

[0108] Comparative Example 6: The difference from Example 7 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 64 wt%:30 wt%:3 wt%:3 wt%.

[0109] Comparative Example 7: The difference from Example 7 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 93 wt%:1 wt%:3 wt%:3 wt%.

[0110] Comparative Example 8: The difference from Example 10 is that the mass ratio of nano-Ga-LLZO particles to LFP is 3 wt%:7 wt%.

[0111] Comparative Example 9: The difference from Example 10 is that the mass ratio of nano-Ga-LLZO particles to LFP is 0.2 wt%:9.8 wt%.

[0112] Comparative Example 10: The difference from Example 10 is that the mass ratio of the Ga-LLZO-coated LFP structure, carbon black, and PVDF is 90 wt%:5 wt%:5 wt%.

[0113] Comparative Example 11: The difference from Example 10 is that the mass ratio of the Ga-LLZO-coated LFP structure, carbon black, and PVDF is 99 wt%:0.5 wt%:0.5 wt%.

[0114] Comparative Example 12: The difference from Example 15 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 25 wt%:60 wt%:5 wt%:3 wt%:5 wt%:2 wt%.

[0115] Comparative Example 13: The difference from Example 15 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 65 wt%:20 wt%:5 wt%:3 wt%:5 wt%:2 wt%.

[0116] The solid secondary batteries prepared in the above examples and comparative examples were successively subjected to electrochemical performance tests, and the test results were summarized and recorded in Table 1.

[0117] Electrochemical performance test: The test temperature was 25 ± 2 °C. It was charged at a constant current of 0.5C to 3.65V; left standing for 10 min, and then discharged at a constant current of 0.5C until the cut-off voltage was 2.5V. The capacity was recorded and used as the initial capacity in the rate test; then charged at a constant current of 1C to 3.65V; left standing for 10 min; then discharged at a constant current of 1C until the cut-off voltage was 2.5V, and the capacity was recorded and used as the rate capacity at 1C. Among them, the C-rate (abbreviated as C) is a value relative to the rated capacity of the battery. For example, if the rated capacity of a battery is 200 Ah, then 1C is equivalent to a charging or discharging rate of 200 A. According to this definition, 0.5C means that the battery can be fully charged within 2 h, and 1C means that the battery can be fully charged within 1 h.

[0118] Table 1

[0119] Referring to the experimental data in Table 1, it can be seen that from the electrochemical performance tests of Examples 1 to 6 and Comparative Examples 1 to 5, the solid electrolytes provided in the examples of the present application can improve the rate capacity compared with ordinary solid electrolytes. From the electrochemical performance tests of Examples 7 to 17 and Comparative Examples 6 to 13, the solid electrolytes with branch structures provided in the examples of the present application can optimize the rate capacity and the initial capacity.

[0120] Correspondingly, another embodiment of the present application provides a method for preparing a solid electrolyte. The difference from the above embodiments is that some process steps are changed, and the structure of the obtained solid electrolyte layer is different. The same or corresponding technical features as those in the above embodiments will not be described in detail here.

[0121] Reference Figure 7, the preparation method includes: in a glove box protected by argon, mixing a lithium metal compound, a lanthanum metal compound, and a zirconium metal compound in a molar ratio of (10 - 11):(2.5 - 3.5):(1.5 - 2.5) to obtain a metal precursor, with the oxygen content and water content both below 1 ppm; using the surface of the LLZO solid electrolyte as the substrate layer 200, setting a baffle with an array of holes on the surface, and using a laser to evaporate the pre-mixed metal precursor for deposition. The deposition temperature is set at 700 °C - 800 °C, and the deposition chamber pressure is 1 kPa - 1.5 kPa; using argon as the carrier gas with a flow rate of 3 standard liters / min - 3.5 standard liters / min; using oxygen as the reaction gas with a flow rate of 2 standard liters / min - 2.5 standard liters / min; and the reaction time is 30 min - 60 min. After the reaction stops, keep the temperature for 15 min - 25 min, and then cool down at a rate of 1 °C / s - 1.5 °C / s to obtain a pre-polymer with array columns 210 grown on the surface.

[0122] Stir the active material, conductive agent, binder, and dispersion solution evenly to obtain the first coating slurry; cover the first coating slurry on the pre-polymer. Among them, the first coating slurry will flow into the gaps between some of the array columns 210, and after drying, a solid electrolyte is formed, and the coating slurry is transformed into the active layer 201.

[0123] 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.

[0124] In some embodiments, mix LFP, carbon black, and PVDF in a ratio of (92 wt% - 96 wt%):(2 wt% - 4 wt%):(2 wt% - 4 wt%), and then add NMP to make the solid content of the slurry reach 50%. Stir under negative pressure for 3 h to obtain the LFP slurry. Using the solid electrolyte layer as the substrate layer, coat the LFP slurry with a scraper, and ultrasonicate for 5 min to promote the infiltration of the slurry between the array columns, and then dry. Repeat the steps of scraping - ultrasonication - drying 3 times to obtain an interpenetrating structure in the form of array columns.

[0125] In some embodiments, the lithium metal compound can be LiC 11 H 19 O2; the lanthanum metal compound can be La(C5H7O2)3·4H2O, and the zirconium metal compound can be Zr(C5H7O2)4.

[0126] The mechanism is as follows: LLZO array columns are grown through laser deposition templating; a laser (such as a carbon dioxide laser with a wavelength of 8 μm to 12 μm) is focused on the precursor target, and the instantaneous high temperature (>2000 °C) vaporizes the metal organic compound. The gaseous precursor is transported to the LLZO substrate layer driven by a carrier gas (Ar). The micropores (diameter ≈ 50 μm, spacing ≈ 100 μm) on the baffle limit the deposition area. Due to limited diffusion after the gaseous precursor passes through the micropores, a local concentration gradient is formed on the surface of the substrate layer, driving columnar growth. The gaseous precursor reacts with O2 to form a Li-La-Zr-O aerosol, and heterogeneous nucleation occurs on the surface of LLZO (activation energy ≈ 150 kJ / mol). Columnar growth preferentially occurs along the (110) crystal plane (due to the difference in anisotropic surface energy), and finally single-crystal LLZO array columns are formed. Combining multi-step ultrasonic-assisted coating and PVDF binder phase regulation, a three-dimensional interpenetrating structure of LFP and LLZO is successfully constructed. This structure can achieve the coordinated optimization of high energy density, low impedance, and long cycle life through vertical ion channels, a three-dimensional electron network, and a multi-level stress buffer mechanism.

[0127] Prepare the positive electrode sheet 1 and the negative electrode sheet 2. 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, the solid electrolyte, and the positive electrode sheet in sequence and thermocompressing to obtain a bare battery cell, putting the bare battery cell into a battery case, and then encapsulating to obtain a solid secondary battery.

[0128] Figure 8 This is the sixth structural schematic diagram of a solid secondary battery provided by an embodiment of the present application.

[0129] In some embodiments, referring to Figure 8 , the process steps for forming the first coating slurry include: uniformly stirring the active material, nano-inorganic ceramic oxide particles, conductive agent, binder, and dispersion solution to obtain a second mixed solution; dispersing the second mixed solution at high speed under negative pressure for 4 h to 6 h to obtain a coating slurry, the viscosity range of the coating slurry is 5000 mPa·s to 20000 mPa·s, and the particle size is less than 20 μm; wherein, the mass ratio of the active material, nano-inorganic ceramic oxide particles, conductive agent, and binder is (73 wt% to 93 wt%):(5 wt% to 18 wt%):(0.6 wt% to 4.5 wt%):(1.4 wt% to 4.5 wt%).

[0130] Mix LFP, nano-LLZO particles, carbon black, and PVDF in the ratio of (73 wt% - 93 wt%):(5 wt% - 18 wt%):(0.6 wt% - 4.5 wt%):(1.4 wt% - 4.5 wt%). Then add NMP to make the solid content of the slurry reach 60%. Disperse it at high speed under negative pressure for 5 h to obtain a mixed slurry. The viscosity range of the slurry is 5000 mPa·s - 20000 mPa·s, and the fineness is less than 20 μm. Pump the mixed slurry into a buffer tank, and then enter the coating die through a feeding pipeline to coat on the LLZO solid electrolyte sheet at a coating speed of 5 m / min. The coated sheet enters a multi-section oven through tape transportation. The temperature setting range of the oven is 80°C - 130°C. After the slurry is dried, due to the self-aggregation tendency of nano-LLZO particles in the slurry, secondary spherical aggregates 202 are transformed from the LLZO particles in the coating layer.

[0131] Figure 9 This is the seventh structural schematic diagram of a solid-state secondary battery provided by an embodiment of the present application.

[0132] Reference Figure 9 , the active material is an active material coated with Ga-LLZO; the process steps for forming the active material layer include: stirring Ga-LLZO particles, active particles, and a first dispersion solution evenly to form a first mixed solution; drying the first mixed solution to form a first precursor; calcining the first precursor to form an active material coated with Ga-LLZO; wherein, the mass ratio of Ga-LLZO particles to active particles is (0.5 wt% - 2 wt%):(8 wt% - 9.5 wt%). 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.

[0133] Add nano-Ga-LLZO particles and LFP in the ratio of (0.5 wt% - 2 wt%):(8 wt% - 9.5 wt%) to the NMP solvent, mix evenly, dry to remove NMP, and then calcine at 700°C for 30 min - 60 min to form a Ga-LLZO-coated LFP structure. Mix the Ga-LLZO-coated LFP structure, carbon black, and PVDF in the ratio of (92 wt% - 98 wt%):(0.6 wt% - 4 wt%):(1.4 wt% - 4 wt%). Then add NMP to make the solid content of the slurry reach 60%. Stir under negative pressure for 3 h - 5 h to obtain an LFP slurry. Using the LLZO solid electrolyte sheet as the base layer, extrude and coat the LFP slurry, and after drying, obtain an interpenetrating structure in the form of surface coating. The interpenetrating structure in the form of surface coating is the active material 203 coated with Ga-LLZO.

[0134] Figure 10The eighth structural schematic diagram of a solid secondary battery provided by an embodiment of the present application.

[0135] In some embodiments, referring to Figure 10 , the active material is graphite; after forming the solid electrolyte, it further includes: uniformly stirring lithium bis(fluorosulfonyl)imide salt, poly(ethylene glycol) methacrylate, polyethylene glycol dimethacrylate, photoinitiator, graphite, and conductive carbon black to obtain a curing solution; immersing the solid electrolyte in the curing solution and performing a curing treatment on the solid electrolyte with the curing solution; wherein, the mass ratio of lithium bis(fluorosulfonyl)imide salt: poly(ethylene glycol) methacrylate: polyethylene glycol dimethacrylate: photoinitiator: graphite: conductive carbon black is (35 wt% - 55 wt%): (30 wt% - 50 wt%): (1 wt% - 7.5 wt%): (1.5 wt% - 4.5 wt%): (2 wt% - 7 wt%): (1 wt% - 3 wt%).

[0136] In pure water, graphite, carbon black, CMC, and SBR are mixed in a ratio of (92 wt% - 96 wt%): (1 wt% - 3 wt%): (0.5 wt% - 2.5 wt%): (1.5 wt% - 3.5 wt%) to make the solid content of the slurry reach 50%. Stir for 3 h under negative pressure to obtain a graphite slurry. Using the LLZO solid electrolyte sheet as the base layer, extrude and coat the graphite slurry, and obtain a solid electrolyte sheet coated with graphite after drying. Immerse the above solid electrolyte sheet in the curing solution and let it stand for 30 min - 60 min. In the curing solution, the mass ratio of lithium bis(fluorosulfonyl)imide salt: poly(ethylene glycol) methacrylate: polyethylene glycol dimethacrylate: photoinitiator: graphite: conductive carbon black is (35 wt% - 55 wt%): (30 wt% - 50 wt%): (1 wt% - 7.5 wt%): (1.5 wt% - 4.5 wt%): (2 wt% - 7 wt%): (1 wt% - 3 wt%). Take out the solid electrolyte sheet after standing and cure it under UV for 3 min - 6 min to obtain an interpenetrating structure in the form of a cross network. The cross network form refers to the cross network formed by the PEG-based polymer network 204 (i.e., the polymer composed of poly(ethylene glycol) methacrylate and polyethylene glycol dimethacrylate) and the graphite / carbon black conductive path 205.

[0137] According to some embodiments of the present application, on the other hand, an embodiment of the present application provides a solid-state secondary battery, including: a battery case with a cavity therein; a bare battery cell located within the cavity; the bare battery cell includes a stacked positive electrode sheet, a solid electrolyte, and a negative electrode sheet, wherein the solid electrolyte includes: a substrate layer 200 and array columns 210, the array columns 210 are located on the surface of the substrate layer 200, there are gaps between the array columns 210, and the surface of the array columns 210 has an active layer 201; the active layer 201 is located on the surface of the substrate layer 200 and within the gaps; the active layer 201 is located between the substrate layer 200 and the positive electrode current collector, and / or, the active layer is located between the substrate layer 100 and the negative electrode current collector. Among them, the active layer located between the substrate layer 200 and the positive electrode current collector is a part of the positive electrode active layer, and together with the positive electrode current collector, it constitutes the positive electrode sheet 1; the active layer located between the substrate layer 200 and the negative electrode current collector is a part of the negative electrode active layer, and together with the negative electrode current collector, it constitutes the negative electrode sheet 2.

[0138] In some embodiments, the array columns 210 have holes therein, and part of the active layer is embedded in the holes.

[0139] In some embodiments, the material of the active layer is an active material coated with Ga-LLZO.

[0140] The beneficial effects of the embodiments of the present application will be further described below in conjunction with examples and comparative examples.

[0141] Example 18: In a glove box under argon protection, 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 both below 1 ppm; with the surface of the LLZO solid electrolyte as the substrate layer, a baffle with array holes was set on the surface, and a laser was used to evaporate the pre-mixed precursor for deposition operation. The deposition temperature was set at 700 °C, the deposition chamber pressure was 1 kPa; argon was used as the carrier gas with a flow rate of 3 standard liters / min; oxygen was used as the reaction gas with a flow rate of 2 standard liters / min; the reaction time was 30 min. After the reaction stopped, it was kept warm for 15 min, and then cooled at a rate of 1 °C / s. A pre-polymer with array columns growing on the surface was obtained.

[0142] LFP, carbon black, and PVDF were mixed in a ratio of 94 wt%:3 wt%:3 wt%, and then NMP was added to make the solid content of the slurry reach 50%. Stir under negative pressure for 3 h to obtain the LFP slurry. Using the solid electrolyte layer as the substrate layer, the LFP slurry was coated with a scraper, and ultrasonic treatment was performed for 5 min to promote the infiltration of the slurry between the array columns, and then dried. The steps of scraping - ultrasonic treatment - drying were repeated 3 times to obtain an interpenetrating structure in the form of array columns.

[0143] A positive electrode sheet and a negative electrode sheet are provided. The active layer is a part of the positive electrode active layer of the positive electrode sheet, and the negative electrode active layer of the negative electrode sheet is located in the gap between the array columns. 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 case and then encapsulated to obtain a solid secondary battery.

[0144] Example 19: The difference from Example 18 is that: the molar ratio of LiC 11 H 19 O2, La(C5H7O2)3·4H2O, and Zr(C5H7O2)4 is 11:2.5:2.

[0145] Example 20: The difference from Example 18 is that: the molar ratio of LiC 11 H 19 O2, La(C5H7O2)3·4H2O, and Zr(C5H7O2)4 is 10.5:3:2.5.

[0146] Example 21: The difference from Example 18 is that: 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.

[0147] Example 22: The difference from Example 18 is that: the preparation steps of the active layer 101 are to mix LFP, nano-LLZO particles, carbon black, and PVDF in a ratio of 80wt%:14wt%:3wt%:3wt%, then add NMP to make the solid content of the slurry reach 60%, disperse at high speed 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: Pump the mixed slurry into a buffer tank, enter the coating die head through a feeding pipeline, and coat it on the LLZO solid electrolyte sheet, with a coating speed of 5m / min. The coated sheet is transported by the running belt into a multi-section oven, and the oven temperature is set in the range of 80°C to 130°C. After the slurry is dried, the self-aggregation tendency of the nano-LLZO particles in the slurry presents as Figure 8 such a structure.

[0148] Example 23: The difference from Example 22 is that: the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 76wt%:18wt%:3wt%:3wt%.

[0149] Example 24: The difference from Example 22 is that: the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 89wt%:5wt%:3wt%:3wt%.

[0150] Example 25: Nano Ga-LLZO particles and LFP were added to NMP solvent at a ratio of 1 wt%: 9 wt%, mixed evenly, dried to remove NMP, and then calcined at 700 °C for 30 min to form an LFP structure coated with Ga-LLZO. The Ga-LLZO-coated LFP structure, carbon black, and PVDF were mixed at a ratio of 94 wt%: 3 wt%: 3 wt%, and then NMP was added to make the solid content of the slurry reach 60%. Stir for 3 h under negative pressure to obtain the LFP slurry. Using the LLZO solid electrolyte sheet as the base layer, the LFP slurry was extrusion-coated and dried to obtain an interpenetrating structure in the form of surface coating, that is Figure 9 structure.

[0151] Example 26: The difference from Example 25 is that the mass ratio of nano Ga-LLZO particles to LFP is 2 wt%: 8 wt%.

[0152] Example 27: The difference from Example 25 is that the mass ratio of nano Ga-LLZO particles to LFP is 0.5 wt%: 9.5 wt%.

[0153] Example 28: The difference from Example 25 is that the mass ratio of the Ga-LLZO-coated LFP structure, carbon black, and PVDF is 98 wt%: 0.6 wt%: 1.4 wt%.

[0154] Example 29: The difference from Example 25 is that the mass ratio of the Ga-LLZO-coated LFP structure, carbon black, and PVDF is 92 wt%: 4 wt%: 4 wt%.

[0155] Example 30: In pure water, graphite, carbon black, CMC, and SBR were mixed at a ratio of 94 wt%: 2 wt%: 1.5 wt%: 2.5 wt% to make the solid content of the slurry reach 50%. Stir for 3 h under negative pressure to obtain the graphite slurry. Using the LLZO solid electrolyte sheet as the base layer, the graphite slurry was extrusion-coated and dried to obtain a solid electrolyte sheet coated with graphite. The above solid electrolyte sheet was immersed in the curing solution and left standing for 30 min. In the curing solution, the mass ratio of LiFSI: PEGMA: PEGDMA: D1173: graphite: SP is 45 wt%: 40 wt%: 5 wt%: 3 wt%: 5 wt%: 2 wt%. After standing, the solid electrolyte sheet was taken out and cured under UV for 3 min to obtain an interpenetrating structure in the form of a cross network, that is Figure 10 structure.

[0156] Example 31: The difference from Example 30 is that the mass ratio of LiFSI: PEGMA: PEGDMA: D1173: graphite: SP is 35 wt%: 50 wt%: 5 wt%: 3 wt%: 5 wt%: 2 wt%.

[0157] Example 32: The difference from Example 30 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 55 wt%:30 wt%:5 wt%:3 wt%:5 wt%:2 wt%.

[0158] Comparative Example 14: The difference from Example 18 is that the molar ratio of LiC 11 H 19 O2, La(C5H7O2)3·4H2O, and Zr(C5H7O2)4 is 8:2.5:2.

[0159] Comparative Example 15: The difference from Example 18 is that the molar ratio of LiC 11 H 19 O2, La(C5H7O2)3·4H2O, and Zr(C5H7O2)4 is 15:2.5:2.

[0160] Comparative Example 16: The difference from Example 22 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 70 wt%:24 wt%:3 wt%:3 wt%.

[0161] Comparative Example 17: The difference from Example 22 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 90 wt%:4 wt%:3 wt%:3 wt%.

[0162] Comparative Example 18: The difference from Example 25 is that the mass ratio of nano-Ga-LLZO particles to LFP is 3 wt%:7 wt%.

[0163] Comparative Example 19: The difference from Example 25 is that the mass ratio of nano-Ga-LLZO particles to LFP is 0.2 wt%:9.8 wt%.

[0164] Comparative Example 20: The difference from Example 25 is that the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 90 wt%:5 wt%:5 wt%.

[0165] Comparative Example 21: The difference from Example 25 is that the mass ratio of Ga-LLZO-coated LFP structure, carbon black, and PVDF is 99 wt%:0.5 wt%:0.5 wt%.

[0166] Comparative Example 22: The difference from Example 30 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 25 wt%:60 wt%:5 wt%:3 wt%:5 wt%:2 wt%.

[0167] Comparative Example 23: The difference from Example 30 is that the mass ratio of LiFSI:PEGMA:PEGDMA:D1173:graphite:SP is 65 wt%:20 wt%:5 wt%:3 wt%:5 wt%:2 wt%.

[0168] The solid secondary batteries prepared in the above examples and comparative examples were successively subjected to electrochemical performance tests, and the test results were summarized and recorded in Table 2.

[0169] Table 2

[0170] 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 electrolytes provided in the examples of the present application can optimize the rate capacity and the initial capacity.

[0171] Correspondingly, another embodiment of the present application provides a method for preparing a solid electrolyte. The difference from the above embodiments is that no array columns and branches are formed, and the structure of the obtained solid electrolyte layer is different. The same or corresponding technical features as those in the above embodiments will not be described in detail here.

[0172] Figure 11 It is a schematic diagram of the ninth structure of a solid secondary battery provided in an embodiment of the present application.

[0173] Reference Figure 11 , the preparation method includes: providing a substrate layer 300; the process steps for forming the second 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; subjecting the second mixed solution to high-speed dispersion under negative pressure for 4 h to 6 h to obtain a coating slurry, the viscosity range of the coating slurry is 5000 mPa·s to 20000 mPa·s, and the particle size is less than 20 μm; wherein, the mass ratio of the active material, nano-inorganic ceramic oxide particles, the conductive agent, and the binder is (73 wt% to 93 wt%):(5 wt% to 18 wt%):(0.6 wt% to 4.5 wt%):(1.4 wt% to 4.5 wt%).

[0174] Mix LFP, nano-LLZO particles, carbon black, and PVDF in the ratio of (73 wt% - 93 wt%):(5 wt% - 18 wt%):(0.6 wt% - 4.5 wt%):(1.4 wt% - 4.5 wt%). Then add NMP to make the solid content of the slurry reach 60%. Disperse it at high speed under negative pressure for 5 h to obtain a mixed slurry. The viscosity range of the slurry is 5000 mPa·s - 20000 mPa·s, and the fineness is less than 20 μm. Pump the mixed slurry into a buffer tank, and enter the coating die through a feeding pipeline, and coat it on the LLZO solid electrolyte sheet (i.e., the substrate layer 300). The coating speed is 5 m / min. The coated sheet enters a multi-section oven through tape transportation. The temperature setting range of the oven is 80°C - 130°C. 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 present in the form of secondary spherical aggregates 302. The coating layer forms the active layer 301.

[0175] Provide a positive electrode sheet and a negative electrode sheet. 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; stack the negative electrode sheet, the solid electrolyte, and the positive electrode sheet in sequence and hot press to obtain a bare battery cell, and place the bare battery cell into a battery case and then encapsulate it to obtain a solid secondary battery.

[0176] Figure 12 This is the tenth structural schematic diagram of a solid secondary battery provided by an embodiment of the present application.

[0177] Reference Figure 12 The preparation method includes: providing a substrate layer 300; the active material is an active material coated with Ga-LLZO; the process steps for forming the active material layer include: stirring Ga-LLZO particles, active particles, and a first dispersion solution evenly to form a first mixed solution; drying the first mixed solution to form a first precursor; calcining the first precursor to form an active material coated with Ga-LLZO; wherein, the mass ratio of Ga-LLZO particles to active particles is (0.5 wt% - 2 wt%):(8 wt% - 9.5 wt%). 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.

[0178] The nano Ga-LLZO particles and LFP are added to the NMP solvent in a ratio of (0.5 wt% - 2 wt%) : (8 wt% - 9.5 wt%), mixed evenly, dried to remove NMP, and then calcined at 700 °C for 30 min - 60 min to form an LFP structure coated with Ga-LLZO. The LFP structure coated with Ga-LLZO, carbon black, and PVDF are mixed in a ratio of (92 wt% - 98 wt%) : (0.6 wt% - 4 wt%) : (1.4 wt% - 4 wt%), and then NMP is added to make the solid content of the slurry reach 60%. Stir for 3 h - 5 h under negative pressure to obtain the LFP slurry. Using the LLZO solid electrolyte sheet as the substrate layer, the LFP slurry is extrusion-coated, and after drying, an interpenetrating structure in the form of surface coating is obtained. The structure in the form of surface coating is the active material 303 coated with Ga-LLZO.

[0179] 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 stacked in sequence and hot-pressed to obtain a bare battery cell, and the bare battery cell is placed in a battery case and then encapsulated to obtain a solid secondary battery.

[0180] Figure 13 This is the eleventh structural schematic diagram of a solid secondary battery provided by an embodiment of the present application.

[0181] Reference Figure 13 , the preparation method includes: providing a substrate layer 100; the active material is graphite; after forming the solid electrolyte, it further includes: uniformly stirring lithium bis(fluorosulfonyl)imide salt, poly(ethylene glycol) methacrylate, polyethylene glycol dimethacrylate, photoinitiator, graphite, and conductive carbon black to obtain a curing solution; immersing the solid electrolyte in the curing solution and performing a curing treatment on the solid electrolyte with the curing solution; wherein, the mass ratio of lithium bis(fluorosulfonyl)imide salt : poly(ethylene glycol) methacrylate : polyethylene glycol dimethacrylate : photoinitiator : graphite : conductive carbon black is (35 wt% - 55 wt%) : (30 wt% - 50 wt%) : (1 wt% - 7.5 wt%) : (1.5 wt% - 4.5 wt%) : (2 wt% - 7 wt%) : (1 wt% - 3 wt%).

[0182] In pure water, graphite, carbon black, CMC, and SBR are mixed in the ratio of (92 wt% - 96 wt%):(1 wt% - 3 wt%):(0.5 wt% - 2.5 wt%):(1.5 wt% - 3.5 wt%) to make the solid content of the slurry reach 50%. Stir for 3 h under negative pressure to obtain the graphite slurry. Using the LLZO solid electrolyte sheet as the substrate layer 300, extrude and coat the graphite slurry, and after drying, obtain the solid electrolyte sheet coated with graphite. Immerse the above solid electrolyte sheet in the curing solution and let it stand for 30 min - 60 min. In the curing solution, the mass ratio of lithium bis(fluorosulfonyl)imide salt: poly(ethylene glycol) methacrylate: poly(ethylene glycol) dimethacrylate: photoinitiator: graphite: conductive carbon black is (35 wt% - 55 wt%):(30 wt% - 50 wt%):(1 wt% - 7.5 wt%):(1.5 wt% - 4.5 wt%):(2 wt% - 7 wt%):(1 wt% - 3 wt%). Take out the solid electrolyte sheet after standing and cure it under UV for 3 min - 6 min to obtain an interpenetrating structure in the form of a cross network. The cross network refers to the PEG-based polymer network 304 (i.e., the polymer composed of poly(ethylene glycol) methacrylate and poly(ethylene glycol) dimethacrylate) and the graphite / carbon black conductive path 305 interpenetrating each other to form a cross network.

[0183] Provide a positive electrode sheet and a negative electrode sheet, and the active layer is the positive electrode active layer of the positive electrode sheet; stack the negative electrode sheet, the solid electrolyte, and the positive electrode sheet in sequence and hot press them to obtain a bare battery cell, put the bare battery cell into a battery case, and then encapsulate it to obtain a solid secondary battery.

[0184] Example 33: The preparation steps of the active layer 101 are as follows: Mix LFP, nano-LLZO particles, carbon black, and PVDF in a ratio of 80 wt%:14 wt%:3 wt%:3 wt%, then add NMP to make the solid content of the slurry reach 60%, and disperse it at high speed under negative pressure for 5 h to obtain a mixed slurry. The viscosity range of the slurry is 10000 mPa·s, and the fineness is less than 20 μm; Coating: Pump the mixed slurry into the buffer tank, enter the coating die through the feeding pipeline, and coat it on the LLZO solid electrolyte sheet, with a coating speed of 5 m / min. The coated sheet is transported by the running belt into a multi-section oven, and the oven temperature is set in the range of 80°C - 130°C. After the slurry is dried, the self-aggregation tendency of the nano-LLZO particles in the slurry presents as Figure 10 such a structure.

[0185] Provide a positive electrode sheet and a negative electrode sheet, 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; stack the negative electrode sheet, the solid electrolyte, and the positive electrode sheet in sequence and hot press them to obtain a bare battery cell, put the bare battery cell into a battery case, and then encapsulate it to obtain a solid secondary battery.

[0186] Example 34: The difference from Example 33 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 76 wt%: 18 wt%: 3 wt%: 3 wt%.

[0187] Example 35: The difference from Example 33 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 89 wt%: 5 wt%: 3 wt%: 3 wt%.

[0188] Example 36: The nano-Ga-LLZO particles and LFP were added to the NMP solvent in a ratio of 1 wt%: 9 wt%, mixed evenly, dried to remove NMP, and then calcined at 700 °C for 30 min to form a Ga-LLZO-coated LFP structure. The Ga-LLZO-coated LFP structure, carbon black, and PVDF were mixed in a ratio of 94 wt%: 3 wt%: 3 wt%, and then NMP was added to make the solid content of the slurry reach 60%. Stir for 3 h under negative pressure to obtain the LFP slurry. Using the LLZO solid electrolyte sheet as the base layer, the LFP slurry was extrusion-coated, and after drying, a surface-coated interpenetrating structure was obtained, that is Figure 11 Structure.

[0189] A positive electrode sheet and a negative electrode sheet were provided, and the active layer was the positive electrode active layer of the positive electrode sheet; the negative electrode sheet, the solid electrolyte, and the positive electrode sheet were stacked and hot-pressed in sequence to obtain a bare battery cell, and the bare battery cell was placed in a battery case and then encapsulated to obtain a solid secondary battery.

[0190] Example 37: The difference from Example 36 is that the mass ratio of nano-Ga-LLZO particles to LFP is 2 wt%: 8 wt%.

[0191] Example 38: The difference from Example 36 is that the mass ratio of nano-Ga-LLZO particles to LFP is 0.5 wt%: 9.5 wt%.

[0192] Example 39: The difference from Example 36 is that the mass ratio of the Ga-LLZO-coated LFP structure, carbon black, and PVDF is 98 wt%: 0.6 wt%: 1.4 wt%.

[0193] Example 40: The difference from Example 36 is that the mass ratio of the Ga-LLZO-coated LFP structure, carbon black, and PVDF is 92 wt%: 4 wt%: 4 wt%.

[0194] Example 41: In pure water, graphite, carbon black, CMC, and SBR were mixed in a ratio of 94 wt%: 2 wt%: 1.5 wt%: 2.5 wt% to achieve a solid content of 50% in the slurry. Stir for 3 h under negative pressure to obtain a graphite slurry. Using an LLZO solid electrolyte sheet as the base layer, the graphite slurry was extruded and coated, and after drying, a solid electrolyte sheet coated with graphite was obtained. The above solid electrolyte sheet was immersed in the curing solution and allowed to stand for 30 min. In the curing solution, the mass ratio of LiFSI: PEGMA: PEGDMA: D1173: graphite: SP was 45 wt%: 40 wt%: 5 wt%: 3 wt%: 5 wt%: 2 wt%. After standing, the solid electrolyte sheet was taken out and cured under UV for 3 min to obtain an interpenetrating structure in the form of a cross-linked network, that is Figure 9 structure.

[0195] A positive electrode sheet and a negative electrode sheet were provided, and the active layer was the positive electrode active layer of the positive electrode sheet; the negative electrode sheet, the solid electrolyte, and the positive electrode sheet were stacked in sequence and hot-pressed to obtain a bare battery cell, and the bare battery cell was placed in a battery case and then encapsulated to obtain a solid secondary battery.

[0196] Example 42: The difference from Example 41 is that the mass ratio of LiFSI: PEGMA: PEGDMA: D1173: graphite: SP is 35 wt%: 50 wt%: 5 wt%: 3 wt%: 5 wt%: 2 wt%.

[0197] Example 43: The difference from Example 41 is that the mass ratio of LiFSI: PEGMA: PEGDMA: D1173: graphite: SP is 55 wt%: 30 wt%: 5 wt%: 3 wt%: 5 wt%: 2 wt%.

[0198] Comparative Example 24: The difference from Example 33 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 70 wt%: 24 wt%: 3 wt%: 3 wt%.

[0199] Comparative Example 25: The difference from Example 33 is that the mass ratio of LFP, nano-LLZO particles, carbon black, and PVDF is 90 wt%: 4 wt%: 3 wt%: 3 wt%.

[0200] Comparative Example 26: The difference from Example 36 is that the mass ratio of nano-Ga-LLZO particles to LFP is 3 wt%: 7 wt%.

[0201] Comparative Example 27: The difference from Example 36 is that the mass ratio of nano-Ga-LLZO particles to LFP is 0.2 wt%: 9.8 wt%.

[0202] Comparative Example 28: The difference from Example 36 is that the mass ratio of the Ga-LLZO-coated LFP structure, carbon black, and PVDF is 90 wt%: 5 wt%: 5 wt%.

[0203] Comparative Example 29: The difference from Example 36 is that the mass ratio of the Ga-LLZO-coated LFP structure, carbon black, and PVDF is 99 wt%: 0.5 wt%: 0.5 wt%.

[0204] Comparative Example 30: The difference from Example 41 is that the mass ratio of LiFSI: PEGMA: PEGDMA: D1173: graphite: SP is 25 wt%: 60 wt%: 5 wt%: 3 wt%: 5 wt%: 2 wt%.

[0205] Comparative Example 31: The difference from Example 41 is that the mass ratio of LiFSI: PEGMA: PEGDMA: D1173: graphite: SP is 65 wt%: 20 wt%: 5 wt%: 3 wt%: 5 wt%: 2 wt%.

[0206] The solid-state secondary batteries prepared in the above examples and comparative examples were successively subjected to electrochemical performance tests, and the test results were summarized and recorded in Table 3.

[0207] Table 3

[0208] 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-state electrolytes provided by the examples of the present application can optimize the rate capacity and the initial capacity.

[0209] According to some embodiments of the present application, on the other hand, the present application provides an energy storage system, including: a secondary battery prepared by the method for preparing a solid-state secondary battery according to any one of the above examples, or the solid-state secondary battery according to the above examples.

[0210] According to some embodiments of the present application, on yet another aspect, the present application provides an electrical device, including: a solid-state secondary battery prepared by the method for preparing a secondary battery according to any one of the above examples, the solid-state secondary battery according to the above examples, or the energy storage system according to the above examples.

[0211] Those of ordinary skill in the art can understand that the above embodiments are specific embodiments for implementing the present application, and in actual applications, various changes can be made in form and details without departing from the spirit and scope of the present application. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application should be subject to the scope defined by the claims.

Claims

1. A method for preparing a solid-state secondary battery, characterized in that, Comprising: Forming a solid electrolyte, comprising: Preparing a ceramic aerosol, the ceramic aerosol comprising 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; Performing a heat treatment on the substrate layer to remove the polyimide particles, and the remaining inorganic ceramic oxide particles are transformed into a plurality of branches with gaps between adjacent branches, and the branches are located on at least one side of the substrate layer; Preparing a coating slurry; Coating the coating slurry on one side of the substrate layer, and the coating slurry also flows into the gaps; Performing a drying treatment, and the coating slurry is transformed into an active layer, and the substrate layer and the branches together constitute the solid 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 include: providing a current collector, and the active layer is located between the current collector and the substrate layer; Stacking the negative electrode sheet, the solid electrolyte, and the positive electrode sheet in sequence and performing hot pressing to obtain a bare battery cell, placing the bare battery cell into a battery case, and then encapsulating to obtain a solid secondary battery.

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

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

4. The manufacturing method of the solid secondary battery according to claim 2, characterized in that, The coating slurry includes a dispersion solution, and the dispersion solution includes a wetting aid, and the wetting aid is used to make the coating slurry flow into the holes.

5. The manufacturing method of the solid secondary battery according to claim 1, characterized in that, 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: the reaction temperature is 500 °C to 1000 °C, the calcination time is 0.8 h to 1.2 h, and the purge rate of the purge gas is 0.5 L / min to 3 L / min.

6. The method for preparing a solid-state secondary battery according to claim 1, characterized in that, The coating slurry includes an active material, and the surface of the active material is coated with Ga-LLZO; The process steps of forming the active material include: Stirring Ga-LLZO particles, active particles, and a solution evenly 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; Wherein, the mass ratio of the Ga-LLZO particles to the active particles is (0.5 wt% - 2 wt%):(8 wt% - 9.5 wt%).

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

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

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

10. A solid-state secondary battery, characterized in that, Including: A battery case having a cavity therein; A bare battery cell located in the cavity; the bare battery cell includes a stacked positive electrode sheet, a solid electrolyte, and a negative electrode sheet. Among them, the solid electrolyte includes: a substrate layer and a plurality of branches, with a gap between adjacent branches, and the branches are located on at least one side of the substrate layer; an active layer located on the surface of the substrate layer and within the gap; the active layer is located between the substrate layer and the positive current collector, and / or the active layer is located between the substrate layer and the negative current collector.

11. The 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 secondary battery according to claim 10, wherein The active layer includes an active material coated with Ga-LLZO.

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

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

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