Solid electrolyte film forming process and solid-state battery

Abstract

The invention belongs to the technical field of solid-state batteries, and particularly relates to a solid-state electrolyte film forming process and a solid-state battery. The solid electrolyte film forming process comprises the following steps: preparing precursor slurry of a solid electrolyte; and obtaining an electrode plate, depositing the precursor slurry on the surface of the electrode plate, carrying out heating treatment under the protection of an inert atmosphere to enable a precursor to react to generate the solid electrolyte, and forming a solid electrolyte membrane on the surface of the electrode plate in situ. According to the film forming process, the solid electrolyte film is directly generated on the surface of the electrode plate in situ, so that the contact tightness and the interface impedance between the solid electrolyte film and the electrode plate are low, the transmission resistance of lithium ions at the interface is smaller, the conductivity is high, and the electrochemical properties such as the rate capability of the solid-state battery can be improved, the energy loss can be reduced, and the cycle life can be prolonged. And moreover, the preparation of the solid electrolyte membrane with relatively thin thickness is facilitated, and the lightweight design of the battery is conveniently realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid-state batteries, and particularly relates to a solid-state electrolyte film forming process and a solid-state battery. BACKGROUND

[0002] The organic electrolyte in the liquid ion battery has poor thermal stability and is flammable, and when the battery is misused to generate heat, there are safety hazards such as liquid leakage, fire and explosion. Compared with the traditional liquid ion battery, the solid-state battery uses a non-flammable solid-state electrolyte with good thermal stability to replace the organic electrolyte, and can have higher energy density, longer cycle life and better safety.

[0003] At present, the solid-state battery generally uses a solid-state electrolyte as a separator, or coats the solid-state electrolyte on a polymer separator as a coating. The pure solid-state electrolyte has high brittleness and poor processability, and is difficult to be made into a dense film layer structure. Moreover, the solid-state electrolyte and the electrode sheet belong to solid-solid contact, which causes the solid-state electrolyte and the electrode sheet to be not close enough, and there is a large interface impedance between the electrolyte and the electrode sheet, which greatly affects the electrical performance of the battery. Although the addition of a binder or a plasticizer can help the solid-state electrolyte form a thin film, it will cause the ionic conductivity to decrease. SUMMARY

[0004] The application aims to provide a solid-state electrolyte film forming process and a solid-state battery, and aims to solve the problem that the existing solid-state electrolyte layer and the electrode are not close enough.

[0005] To achieve the above application purposes, the technical solutions adopted by the application are as follows:

[0006] In a first aspect, the application provides a solid-state electrolyte film forming process, comprising the following steps:

[0007] Preparation of a precursor slurry of a solid-state electrolyte;

[0008] Obtaining an electrode sheet, depositing the precursor slurry on the surface of the electrode sheet, and then generating the solid-state electrolyte by heating treatment under the protection of an inert atmosphere to form a solid-state electrolyte film in situ on the surface of the electrode sheet.

[0009] In some possible implementation manners, the precursor slurry includes at least one of a precursor material of an inorganic solid-state electrolyte and a precursor material of a polymer solid-state electrolyte.

[0010] In some possible implementation manners, the solvent in the precursor slurry includes at least one of acetonitrile, N,N-dimethylformamide, toluene, tetrahydrofuran, N-methyl pyrrolidone, heptane and deionized water.

[0011] In some possible implementations, the precursor material of the inorganic solid-state electrolyte includes a halide precursor or a sulfide precursor.

[0012] In some possible implementations, the precursor material of the polymer solid-state electrolyte includes a polymer monomer, an initiator and a lithium salt.

[0013] In some possible implementations, the halide precursor includes LiX and MX, wherein X is at least one halogen selected from F, Cl and Br, and M is at least one selected from In, Y, Zr, Sc, Er, Al and Fe.

[0014] In some possible implementations, the sulfide precursor includes lithium sulfide and phosphorus sulfide.

[0015] In some possible implementations, the mass ratio of the LiX and the MX is (2-4):1.

[0016] In some possible implementations, the mass ratio of the lithium sulfide and the phosphorus sulfide is (3-13):(1-4).

[0017] In some possible implementations, the polymer monomer includes at least one of an acrylate monomer, an ethylene oxide-containing monomer, a vinylidene fluoride monomer, an ether group-containing monomer and a carbonate group-containing monomer.

[0018] In some possible implementations, the initiator includes at least one of a photoinitiator and a thermal initiator.

[0019] In some possible implementations, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis-trifluoromethanesulfonimide, lithium bis-fluorosulfonimide and lithium bis-oxalato-borate.

[0020] In some possible implementations, the mass ratio of the polymer monomer and the initiator is 100:(0.2-2).

[0021] In some possible implementations, the mass ratio of the polymer monomer and the lithium salt is 1:(0.25-1).

[0022] In some possible implementations, the precursor slurry is mixed at a temperature of 50-80°C.

[0023] In some possible implementations, the temperature of the heating treatment is 200-220°C, and the time length is 2-10 min.

[0024] In some possible implementations, after the precursor is reacted to generate the solid-state electrolyte, a rolling treatment is further performed at a pressure of 20-60 MPa.

[0025] In some possible implementations, the solid-state electrolyte film has a thickness of 10-130 μm.

[0026] In a second aspect, the present application provides a solid-state battery, which has a solid-state electrolyte film prepared according to the solid-state electrolyte film forming process described above on the surface of an electrode sheet.

[0027] The solid-state electrolyte film forming process provided by the first aspect of the present application can directly generate the solid-state electrolyte in situ on the surface of the electrode sheet by heating the precursor slurry of the solid-state electrolyte after depositing the precursor slurry on the surface of the electrode sheet. In one aspect, the direct in-situ generation of the electrolyte from the precursor can form a solid-state electrolyte film layer with good adhesion on the surface of the electrode sheet. This can improve the contact tightness between the solid-state electrolyte film and the electrode sheet, reduce the interface impedance between the solid-state electrolyte film layer and the electrode sheet, and improve the electrochemical performance such as the electrical conductivity. In another aspect, the solid-state electrolyte film generated directly in situ from the precursor does not need to add additional film-forming aids such as binders and plasticizers, thereby avoiding the influence of these film-forming aids on the ionic conductivity, so as to ensure that the electrical conductivity of the solid-state electrolyte film layer is close to or equal to the bulk conductivity. Moreover, the electrode sheet provides the solid-state electrolyte film with processability, and does not need to add additional film-forming aid materials to reduce the electrical conductivity, so as to facilitate the preparation of a solid-state electrolyte film with a relatively small thickness, and facilitate the lightweight design of the battery.

[0028] In the solid-state battery provided by the second aspect of the present application, the solid-state electrolyte film directly generated in situ on the surface of the electrode sheet has good contact tightness with the electrode sheet, low interface impedance, small transmission resistance of lithium ions at the interface, and high electrical conductivity, which can improve the rate performance of the solid-state battery, reduce energy loss, prolong the cycle life, and improve other electrochemical performance. Moreover, the solid-state electrolyte film with a relatively small thickness is conducive to the lightweight design of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0030] Figure 1 is a flowchart of the solid-state electrolyte film forming process provided by the embodiments of the present application Figure One ;

[0031] Figure 2 is a flowchart of the solid-state electrolyte film forming process provided by the embodiments of the present application Figure Two . DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application and not intended to limit the present application.

[0033] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0034] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one of the following" or similar expressions means any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b or c", or "at least one of a, b and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b and c can be single or multiple.

[0035] It should be understood that in various embodiments of the present application, the size of the sequence number of the above processes does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence. The execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0036] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0037] The weight of the related components mentioned in the embodiments of the present application can not only refer to the specific content of each component, but also represent the weight ratio relationship between each component. Therefore, as long as the content of the related components in the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the embodiments of the present application. Specifically, the mass mentioned in the embodiments of the present application can be μg, mg, g, kg and other mass units commonly known in the chemical field.

[0038] The terms "first", "second", "third", etc., are used only for the purpose of description, to distinguish between objects, such as substances, from each other, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. For example, without departing from the scope of the embodiments of the present application, the first XX can also be referred to as the second XX, and similarly, the second XX can also be referred to as the first XX. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features.

[0039] The first aspect of the embodiments of the present application provides a solid-state electrolyte film forming process, as shown in the accompanying drawings, comprising the following steps: Figure 1 The first aspect of the embodiments of the present application provides a solid-state electrolyte film forming process, as shown in the accompanying drawings, comprising the following steps:

[0040] S10. Preparing a precursor slurry of a solid-state electrolyte;

[0041] S20. Obtaining an electrode sheet, depositing the precursor slurry on the surface of the electrode sheet, and then generating the solid-state electrolyte by heating treatment under the protection of an inert atmosphere to make the precursor react, thereby forming a solid-state electrolyte film in situ on the surface of the electrode sheet.

[0042] The solid-state electrolyte film forming process provided by the first aspect of the embodiments of the present application can directly generate the solid-state electrolyte in situ on the surface of the electrode sheet by depositing the precursor slurry of the solid-state electrolyte on the surface of the electrode sheet and then making the precursor react by heating treatment under the protection of an inert atmosphere, i.e., forming a solid-state electrolyte film in situ on the surface (exemplarily, including the upper and lower surfaces) of the electrode sheet. On the one hand, the precursor directly generates the electrolyte in situ, which can form a solid-state electrolyte film layer with good adhesion on the surface of the electrode sheet. This improves the contact tightness between the solid-state electrolyte film and the electrode sheet, reduces the interface impedance between the solid-state electrolyte film layer and the electrode sheet, and improves the electrochemical performance such as the electrical conductivity. On the other hand, the solid-state electrolyte film generated in situ by the precursor does not need to add additional film forming aids such as binders and plasticizers, thereby avoiding the influence of these film forming aids on the ionic conductivity, so as to ensure that the electrical conductivity of the solid-state electrolyte film layer is close to or equal to the bulk conductivity. Moreover, the electrode sheet provides the solid-state electrolyte film with processability, and does not need to add additional film forming aid materials to reduce the electrical conductivity, so as to be conducive to the preparation of a solid-state electrolyte film with a relatively thin thickness, and conducive to the lightweight design of the battery.

[0043] In the above step S10:

[0044] In some possible implementations, the precursor slurry includes at least one of a precursor material of an inorganic solid-state electrolyte or a precursor material of a polymer solid-state electrolyte. In this case, the precursor material of the inorganic solid-state electrolyte can be converted into the inorganic solid-state electrolyte material by heat treatment, and a pure inorganic solid-state electrolyte film layer can be formed on the surface of the electrode sheet. The precursor material of the polymer solid-state electrolyte includes a polymer monomer, a lithium salt, and an initiator, and the polymer monomer can be polymerized to form a polymer solid-state electrolyte film layer under the condition of heat. The precursor slurry can also include both the precursor material of the solid-state electrolyte and the precursor material of the polymer solid-state electrolyte, and different types of precursors can be converted into different types of solid-state electrolytes by heat treatment, so as to form a composite film layer of the inorganic solid-state electrolyte and the polymer solid-state electrolyte on the surface of the electrode.

[0045] In some possible implementations, the solvent in the precursor slurry includes at least one of acetonitrile, N,N-dimethylformamide, toluene, tetrahydrofuran, N-methyl pyrrolidone, heptane, and deionized water. These solvents have good solubility and dispersion performance for the precursor material of the inorganic solid-state electrolyte and the precursor material of the polymer solid-state electrolyte, and are beneficial to the full contact of all the precursor materials and the uniform reaction of the precursor materials on the electrode sheet to generate the solid-state electrolyte film.

[0046] In some embodiments, the precursor material of the inorganic solid-state electrolyte does not include an oxide. In some possible implementations, the precursor material of the inorganic solid-state electrolyte includes a halide precursor or a sulfide precursor. In this case, a halide solid-state electrolyte can be generated in situ on the surface of the electrode sheet by the halide precursor, and the halide solid-state electrolyte has halogen (such as Cl, Br, or I) as the main anion component, high ionic conductivity, and a wide electrochemical window. The halide solid-state electrolyte has good compatibility with high-voltage positive electrode materials (such as NMC811) and good stability to air and humidity. In addition, a sulfide solid-state electrolyte can be generated in situ on the surface of the electrode sheet by the sulfide precursor. The sulfide solid-state electrolyte has sulfur as the main anion component, high ionic conductivity, and good mechanical properties. The sulfide solid-state electrolyte has high ionic conductivity, close to or even exceeding the level of liquid electrolyte. The sulfide solid-state electrolyte is deformable and easy to form close contact with the electrode material, thereby reducing the interface impedance. The sulfide solid-state electrolyte has good low-temperature performance and is suitable for working in a low-temperature environment.

[0047] In some possible implementations, the halide precursors include LiX and MX, where X is selected from at least one halogen of F, Cl, Br, and M is selected from at least one of In, Y, Zr, Sc, Er, Al, Fe. In this case, the halide solid-state electrolytes that can be made by the halide precursors include Li3InCl6, Li3YCl6, Li2ZrCl6, Li3ErCl6, Li3ScCl6, Li3InBr6, and some double-metal halides containing In and Y, etc. These halide precursor materials have advantages in ionic conductivity, chemical stability, and cost, and are suitable for different application scenarios.

[0048] In some embodiments, Li3YCl6 is a novel chloride solid-state electrolyte with a room-temperature ionic conductivity of up to 0.51 mS / cm and good compatibility with high-voltage cathode materials such as NMC811. Its crystal structure is trigonal, with high chemical and electrochemical stability. The preparation method includes: mixing LiCl and YCl3 in a certain proportion and then heating to react by solid-phase sintering. Li2ZrCl6 is a low-cost, high-performance chloride solid-state electrolyte with a room-temperature ionic conductivity of 0.81 mS / cm. Its advantages include good humidity stability (can exist stably at 5% humidity) and low raw material cost, making it suitable for large-scale production. The preparation method includes: mixing LiCl and ZrCl4 and then heating to synthesize by solid-phase reaction. Li3ErCl6 is a rare-earth-based chloride solid-state electrolyte with a room-temperature ionic conductivity of 0.31 mS / cm. Its crystal structure is similar to that of Li3YCl6, with high ion migration ability. The preparation method includes: mixing LiCl and ErCl3 and then heating to react by solid-phase sintering. Li3ScCl6 is a chloride solid-state electrolyte with high ionic conductivity, with a room-temperature ionic conductivity of up to 1.2 mS / cm. Its crystal structure is cubic, with good deformability and interface compatibility. The preparation method includes: mixing LiCl and ScCl3 and then heating to synthesize by solid-phase reaction. Li3InBr6 is a bromide analogue of Li3InCl6 with higher ionic conductivity (up to 2.04 mS / cm at room temperature), but its cost is higher and it is sensitive to humidity. The preparation method includes: reacting LiBr and InBr3 in water by liquid-phase method. Li3AlCl6 is a low-cost, high-stability chloride solid-state electrolyte with a room-temperature ionic conductivity of 0.5 mS / cm. It has good stability to air and humidity, making it suitable for large-scale applications. The preparation method includes: mixing LiCl and AlCl3 and then heating to synthesize by solid-phase reaction. Li3FeCl6 is a transition metal-based chloride solid-state electrolyte with a room-temperature ionic conductivity of 0.4 mS / cm. Its advantages include low raw material cost and good compatibility with high-voltage cathode materials. The preparation method includes: mixing LiCl and FeCl3 and then heating to synthesize by solid-phase reaction.

[0049] In some possible implementations, the mass ratio of the LiX and the MX is (2-4):1; specifically, it can be 2:1, 3:1, 4:1, etc., typical but non-limiting any point value or interval value between any two point values. In some specific embodiments, the mass ratio of LiX and the MX is 3:1. Wherein X is at least one halogen selected from F, Cl, Br, and M is at least one selected from In, Y, Zr, Sc, Er, Al, and Fe.

[0050] In some possible implementations, the sulfide precursor includes lithium sulfide and phosphorus sulfide. In this case, lithium sulfide (Li2S) and phosphorus sulfide (P2S5) are important precursors for preparing sulfide solid electrolytes, and various high-performance sulfide solid electrolytes can be generated through their reaction. The sulfide solid electrolyte is generated through a solid-phase reaction or a mechanochemical method, and the reaction general formula is: xLi2S + yP2S5→ Li 2x P 2y S x+5 y; during the reaction, Li2S provides lithium ions, P2S5 provides sulfur ions and phosphorus ions, and a sulfide crystal structure with lithium ion conduction capability is formed. The sulfide solid electrolyte includes Li3PS4, Li4P2S6, Li7P3S 11 、Li 3.25 P 0.25 S4, and other sulfide solid electrolytes. These materials have high ionic conductivity and good mechanical properties, but are sensitive to air and humidity.

[0051] In some possible implementations, the mass ratio of the lithium sulfide and the phosphorus sulfide is (3-13):(1-4). For example, it can be 3:1, 7:3, 4:1, 3.25:0.25, and the like, or an interval value between any two point values. When the molar ratio of Li2S:P2S5 is 3:1, Li3PS4 is prepared, which has a tetragonal crystal structure and a relatively high ionic conductivity (about 0.1 mS / cm-0.2 mS / cm at room temperature). It has good chemical stability and is suitable as a basic electrolyte material. When the molar ratio of Li2S:P2S5 is 7:3, Li7P3S 11 is prepared, which has a glass-ceramic structure and an ultra-high ionic conductivity (about 17 mS / cm at room temperature). It is one of the sulfide electrolytes with the best performance at present, but is sensitive to air and humidity. When the molar ratio of Li2S:P2S5 is 4:1, Li4P2S6 is prepared, which has a layered structure and a relatively low ionic conductivity (about 0.01 mS / cm at room temperature). It is suitable as a matrix material of a composite electrolyte. When the molar ratio of Li2S:P2S5 is 3.25:0.25, Li 3.25 P 0.25 S4 is prepared, which has a sulfide argyrodite structure and an ionic conductivity of about 2.5 mS / cm. It has good chemical stability and mechanical properties. The preparation method includes mixing lithium sulfide (Li2S) and phosphorus sulfide (P2S5) in a certain proportion and heating to generate the corresponding sulfide solid electrolyte.

[0052] In some possible implementations, the precursor material of the polymer solid-state electrolyte includes a polymer monomer, an initiator, and a lithium salt. In this case, the polymer electrolyte is prepared by spraying the polymer monomer, the initiator, and the lithium salt together on an electrode sheet after the polymer monomer, the initiator, and the lithium salt are made into a precursor slurry, and then initiating the formation of a polymer solid-state electrolyte film by the initiator. The polymer solid-state electrolyte is a kind of solid-state electrolyte material with a polymer as a matrix, has good flexibility, easy processing, excellent interface contact, and is widely used in the field of all-solid-state batteries. At present, the polymer solid-state electrolyte includes a polyethylene oxide (PEO) based electrolyte, has a relatively high lithium ion transference number (~0.2-0.3). A polyacrylonitrile (PAN) based electrolyte has relatively high mechanical strength and thermal stability, but has low ionic conductivity. A polyvinylidene fluoride (PVDF) based electrolyte has excellent chemical stability and mechanical properties. A polymethyl methacrylate (PMMA) based electrolyte has good transparency and processing performance. A polyionic liquid (PIL) based electrolyte combines the advantages of ionic liquids and polymers, has relatively high ionic conductivity and a wide electrochemical window. In addition, the ionic conductivity of the polymer solid-state electrolyte can be improved by adding a lithium salt (such as LiTFSI, etc.).

[0053] In some possible implementations, the polymer monomer includes at least one of an acrylate monomer, an ethylene oxide-containing monomer, a vinylidene fluoride monomer, an ether group-containing monomer, and a carbonate group-containing monomer. The acrylate monomer includes butyl acrylate, methyl methacrylate, pentaerythritol tetraacrylate, ethoxylated trimethylolpropane triacrylate, etc. The characteristic is that a three-dimensional network can be formed by cross-linking to improve the mechanical strength, and the dispersion of the lithium salt is compatible. The ether group-containing monomer includes ethylene glycol diacrylate, an ethylene oxide derivative, etc. The characteristic is that the ether group (-O-) provides a lithium ion transmission channel to enhance the ionic conductivity. The carbonate group-containing monomer includes fluorinated alkoxylated trimethylolpropane triacrylate, etc. It can also be a cyano-containing monomer, an amide-containing monomer, a halogen-containing monomer, etc. By introducing these monomers, the electrochemical window of the polymer solid-state electrolyte is widened, and the decomposition under high pressure conditions is inhibited.

[0054] In some possible implementations, the initiator includes at least one of a photoinitiator and a thermal initiator; and the polymer monomer is polymerized by the initiator to form a polymer solid-state electrolyte. In some embodiments, the thermal initiator includes dibenzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), diisopropyl peroxydicarbonate, etc. The photoinitiator includes a hydroxy ketone, a benzoyl formate, 2,4,6(trimethylbenzoyl) diphenyl phosphine oxide, etc.

[0055] In some possible implementations, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis-trifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium bis(oxalato)borate. These lithium salts can effectively improve the ionic conductivity of the polymer solid electrolyte. Among them, lithium hexafluorophosphate (LiPF6) is widely used but has poor thermal stability. Lithium bis-trifluoromethanesulfonimide (LiTFSI) has a high dissociation degree, and the ionic conductivity can reach 1*10 -3 S / cm. Lithium bisfluorosulfonimide (LiFSI) has excellent high-temperature stability and is suitable for high-voltage systems. Lithium bis(oxalato)borate (LiBOB) can inhibit lithium dendrite growth and improve interface stability. Multiple lithium salts can be added to the polymer solid electrolyte at the same time, for example, LiTFSI and LiPF6 are used together to balance the conductivity and cost.

[0056] In some possible implementations, the mass ratio of the polymer monomer and the initiator is 100:(0.2-2). For example, the mass ratio of the polymer monomer and the initiator can be 100:0.2, 100:0.5, 100:1, 100:1.5, 100:2, or any point value or interval value between any two point values of the typical but non-limiting values. In some possible implementations, the mass ratio of the polymer monomer and the lithium salt is 1:(0.25-1). For example, the mass ratio of the polymer monomer and the lithium salt can be 1:0.25, 1:0.5, 1:0.75, 1:0.8, 1:1, or any point value or interval value between any two point values of the typical but non-limiting values. In this ratio, the monomer can be better initiated to polymerize to form a polymer solid electrolyte film layer, the reaction efficiency is high, and the by-products are few.

[0057] In the step S20 described above:

[0058] In some embodiments, the method of depositing the precursor slurry on the surface of the electrode sheet includes spraying, doctor blading, brushing, or the like.

[0059] In some possible implementations, the precursor slurry is mixed and treated at a temperature of 50-80°C. In this condition, the components in the precursor slurry can be fully dissolved, dispersed, and uniformly mixed, and the stability of the slurry is good. For example, the mixing temperature of the precursor slurry can be 50°C, 60°C, 70°C, 80°C, or any point value or interval value between any two point values of the typical but non-limiting values.

[0060] In some possible implementation manners, the temperature condition of the heating treatment is 200-220 DEG C, and the time length is 2-10 min. In this case, the precursor can be fully promoted to react in situ on the surface of the electrode sheet to generate the solid-state electrolyte film. For example, the heating temperature can be 200 DEG C, 205 DEG C, 210 DEG C, 215 DEG C, 220 DEG C, or any interval value between any two point values, and the time length can be 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or any interval value between any two point values.

[0061] In some embodiments, the atmosphere condition of the heating treatment can be an inert atmosphere such as nitrogen, argon, helium, or a vacuum condition, or a vacuum inert atmosphere condition.

[0062] In some possible implementation manners, after the precursor reacts to generate the solid-state electrolyte, a rolling treatment is further performed at a pressure of 20-60 MPa. The rolling treatment can densify the solid-state electrolyte film and better ensure the interface contact between the solid-state electrolyte and the electrode sheet. For example, the pressure of the rolling treatment can be 20 MPa, 30 MPa, 40 MPa, 50 MPa, 60 MPa, or any interval value between any two point values.

[0063] In some possible implementation manners, the thickness of the solid-state electrolyte film is 10-130 μm. The thickness of the solid-state electrolyte film is currently 60-100 μm, which is relatively thick and can reduce the energy density of the battery and make the interface hard and brittle. The solid-state electrolyte film generated by the precursor in the embodiments of the present application does not need to add additional film-forming aids such as binders and plasticizers, which can avoid the influence of the film-forming aids on the ionic conductivity and facilitate the preparation of a solid-state electrolyte film with a relatively small thickness, thereby facilitating the lightweight design of the battery. The thickness of the solid-state electrolyte film is 10-130 μm, which can not only meet the safety requirement (to prevent the short circuit of the positive and negative electrodes) but also ensure good ionic conductivity. For example, the thickness of the solid-state electrolyte film can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 125 μm, 130 μm, or any interval value between any two point values.

[0064] In some embodiments, as shown in FIG. 2, the solid-state electrolyte film 20 is formed on the surface of the electrode sheet 10. Figure 2As shown, halide or sulfide solid-state electrolyte precursors are sprayed on the upper and lower surfaces of the electrode (dry electrode) respectively, and a thin layer of the precursors is formed on the surface of the electrode. Then, the electrode is heated in an oven or other device to evaporate the solvent, and finally a thin layer of halide or sulfide solid-state electrolyte is formed on the surface of the electrode. Subsequently, the solid-state electrolyte layer and the electrode sheet are tightly combined together using a large pressure to form a dense solid-state electrolyte-electrode interface. On the one hand, the poor processability of the solid-state electrolyte makes it difficult to form a thin layer, and on the other hand, the interface between the electrode and the electrolyte can be densified to improve the efficiency of battery assembly. The thickness of the solid-state electrolyte coating is 10-30 μm, and the thickness of the electrode sheet is 100 μm-1500 μm.

[0065] In some embodiments, in a dry atmosphere, Li2S+P2S5 is first mixed in acetonitrile or other solvent (mixing temperature is 50-80°C), and then the precursor slurry is sprayed onto the surface of the electrode sheet through a nozzle and heated in an oven at 200-220°C for 2-10 minutes (depending on the concentration and thickness of the film). After the solvent is completely evaporated, a solid-state electrolyte film layer is generated in situ on the surface of the electrode sheet. Then, the electrode sheet together with the solid-state electrolyte thin layer is rolled by a roller press to form a tight interface contact.

[0066] In a second aspect, the embodiments of the present application provide a solid-state battery, which has a solid-state electrolyte film prepared according to the above solid-state electrolyte film forming process on the surface of the electrode sheet.

[0067] In the solid-state battery of the embodiments of the present application, the solid-state electrolyte film is directly produced in situ on the surface of the electrode sheet, the contact between the solid-state electrolyte film and the electrode sheet is tight, the interface impedance is low, the transmission resistance of lithium ions at the interface is smaller, the electrical conductivity is high, and the rate performance of the solid-state battery can be improved, the energy loss can be reduced, and the cycle life can be prolonged. In addition, it is beneficial to prepare a solid-state electrolyte film with a relatively small thickness, and it is convenient to realize lightweight design of the battery.

[0068] To enable the above-described implementation details and operations of the present application to be clearly understood by those skilled in the art, and to further demonstrate the significant performance of the solid-state electrolyte film forming process and the solid-state battery of the embodiments of the present application, the above technical solutions are illustrated by multiple embodiments as follows.

[0069] Embodiment 1

[0070] A Li3PS4 solid-state electrolyte film forming process, comprising the steps of:

[0071] 70 g of Li2S and 30 g of P2S5 were mixed and stirred in 500 ml of acetonitrile at 60 ° C for 30 minutes to form a precursor slurry, which was then sprayed onto the surface of a high-nickel positive electrode sheet prepared by a dry process (containing carbon tubes, polyvinylidene fluoride PVDF and bistrifluoromethanesulfonyl imide lithium LiTFSI). It was heated at 180 ° C under vacuum nitrogen inert gas protection for 3 hours, and then heated to 220 ° C for 60 minutes to react. Li3PS4 solid electrolyte was generated in situ on the surface of the electrode sheet. Then, the electrode and the Li3PS4 solid electrolyte formed on both sides were rolled at a pressure of 40 MPa to obtain a Li3PS4 solid electrolyte film with a thickness of about 30 μm on the surface of the electrode sheet.

[0072] Example 2

[0073] A Li3InCl6 solid-state electrolysis film forming process comprises the following steps:

[0074] 60 grams of LiCl and 20 grams of InCl3 were mixed and stirred in 500 milliliters of acetonitrile at 60°C for 30 minutes to form a precursor slurry, which was then sprayed onto the surface of a high-nickel material positive electrode sheet prepared by a dry method (containing carbon tubes, polyvinylidene fluoride PVDF and bis(trifluoromethanesulfonyl)imide lithium LiTFSI). The mixture was heated at 180°C under vacuum nitrogen inert gas protection for 3 hours, and then heated to 220°C for 60 minutes to generate Li3InCl6 solid electrolyte in situ on the surface of the electrode sheet. Subsequently, the electrode and the Li3InCl6 solid electrolyte formed on both sides were rolled at a pressure of 40 MPa to obtain a Li3InCl6 solid electrolyte film with a thickness of about 30 μm on the surface of the electrode sheet.

[0075] Example 3

[0076] A polymeric solid electrolyte film forming process comprises the following steps:

[0077] Polyethylene glycol dimethacrylate (PEGDMA) (molecular weight 800) and LiNO₃ were dissolved in dipropylene glycol dimethyl ether, maintaining a Li:ethoxy unit (EO) ratio of 0.1. 4% methyl benzoylformate (MBF) was used as a photoinitiator. The mixed solution was sprayed onto a dried high-nickel cathode sheet (containing carbon nanotubes, polyvinylidene fluoride (PVDF), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The solution was then irradiated with ultraviolet light (VMR UVAC, 115V-60Hz, 254 / 365nm) for 20 minutes, resulting in a polymeric solid electrolyte film approximately 95μm thick on the electrode surface.

[0078] Example 4

[0079] A composite solid electrolyte film forming process comprises the following steps:

[0080] First, the halide precursor is sprayed onto the electrode sheet and then heated to form a film according to the method of Example 2. Then, the sulfide precursor is continuously sprayed and heated to form a film according to the method of Example 1. Then, the electrode and the halide and sulfide solid electrolytes formed on both sides are rolled at a pressure of 40 MPa, and a composite solid electrolyte film having a thickness of about 60 μm is obtained on the surface of the electrode sheet.

[0081] Example 5

[0082] A composite solid electrolyte film forming process, comprising the steps of:

[0083] First, the halide precursor is sprayed onto the electrode sheet and then heated to form a film according to the method of Example 2. Then, the sulfide precursor is continuously sprayed and heated to form a film according to the method of Example 1. Then, the electrode and the halide and sulfide solid electrolytes formed on both sides are rolled at a pressure of 40 MPa, and a composite solid electrolyte film having a thickness of about 60 μm is obtained on the surface of the electrode sheet.

[0084] Comparative Example 1

[0085] A solid electrolyte film forming process, comprising the steps of:

[0086] The raw materials Li2S and P2S5 are used to synthesize Li3PS4 solid electrolyte in advance. Then, the synthesized sulfide Li3PS4 electrolyte is mixed with acetonitrile at 60°C for 30 minutes to form a slurry, which is then directly sprayed onto the electrode sheet and heated to form a film in vacuum. Then, the electrode and the sulfide solid electrolyte formed on both sides are rolled at a pressure of 40 MPa, and a sulfide solid electrolyte film having a thickness of about 30 μm is obtained on the surface of the electrode sheet.

[0087] Comparative Example 2

[0088] A solid electrolyte film forming process, comprising the steps of:

[0089] The raw materials LiCl and InCl3 are used to synthesize Li3InCl6 solid electrolyte in advance. Then, the synthesized halide Li3InCl6 electrolyte is mixed with acetonitrile at 60°C for 30 minutes to form a slurry, which is then directly sprayed onto the electrode sheet and heated to form a film in vacuum. Then, the electrode and the halide solid electrolyte formed on both sides are rolled at a pressure of 40 MPa, and a halide solid electrolyte film having a thickness of about 30 μm is obtained on the surface of the electrode sheet.

[0090] Comparative Example 3

[0091] A solid electrolyte film forming process, comprising the steps of:

[0092] The polymer electrolyte synthesized in advance was mixed and stirred in dipropylene glycol dimethyl ether for 30 minutes to form a slurry, and then irradiated with ultraviolet (UV) light (VMR UVAC 115V-60Hz 254 / 365nm) for 20 minutes, to obtain a polymer solid-state electrolyte film with a thickness of about 95 μm on the surface of the electrode sheet.

[0093] To verify the progressiveness of the embodiments of the present application, the above embodiments and comparative examples were subjected to the following performance tests, respectively.

[0094] 1. Electronic conductivity test: Electronic conductivity is defined as the migration rate of electrons in the electrolyte, with the unit of Scm -1 . Ideally, a solid-state electrolyte has electronic insulating properties, so its electronic conductivity should be as low as possible. To measure the electronic conductivity of the electrolyte, a double-blocking electrode direct current polarization method was used for testing. The electrode sheet coated with the solid-state electrolyte was die-cut into a 10 mm disc and placed into a 10 mm diameter solid-state battery mold to assemble a stainless steel / solid-state electrolyte / stainless steel battery. In the actual test, a constant voltage of 0.5 V was applied to the symmetric battery, and the current change over time was observed. When the test time was 3600 s, the current was stable, and the current value at this time was recorded as the steady-state current value. The electronic conductivity was calculated according to the formula: σ e = (L*I) / (ΔV*S), where σ e is the electronic conductivity of the electrolyte (S cm -1 ), L is the thickness of the solid-state electrolyte sheet (cm), ΔV is the applied bias voltage (V), I is the steady-state current (A), and S is the effective area of the electrolyte and electrode contact (cm 2 ). The IviumStat.h ultra-high resolution electrochemical workstation was used for testing.

[0095] 2. Ion conductivity test: The ion conductivity of the solid-state electrolyte was measured. In this subject, the alternating current impedance method was used for measurement. The alternating current impedance method (EIS) refers to the process of testing EIS by inputting a specific frequency to a steady-state system. The electrode sheet coated with the solid-state electrolyte was die-cut into a 10 mm disc and placed into a 10 mm diameter solid-state battery mold to assemble a stainless steel / solid-state electrolyte / stainless steel battery. The IviumStat.h ultra-high resolution electrochemical workstation was used for alternating current impedance spectrum (EIS) testing, with the test frequency range set to 0.01-10 6 Hz. The ion conductivity was obtained from the formula σ = L / (R*S), where σ is the ion conductivity (S cm -1 ), L is the thickness of the electrolyte sheet (cm), R is the bulk resistance measured by the alternating current impedance method (Ω), and S is the effective contact area of the test electrode (cm 2 ).

[0096] The test results are shown in Table 1 below:

[0097] Table 1

[0098]

[0099]

[0100] From the above test results, it can be seen that the solid-state electrolyte film prepared in situ on the surface of the electrode sheet according to the embodiments of the present application exhibits lower electronic conductivity and higher ionic conductivity. Among them, the composite solid-state electrolyte film of the Li3PS4 solid-state electrolyte film of Example 1 and the Li3InCl6 solid-state electrolyte film of Example 2 is Example 4, and the composite solid-state electrolyte film of the Li3PS4 solid-state electrolyte film of Example 1 and the polymeric solid-state electrolyte film of Example 3 is Example 5. It can be seen that the ionic and electronic conductivities of the composite solid-state electrolyte film are intermediate values of the two solid-state electrolyte films being compounded.

[0101] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A solid electrolyte film forming process, characterized in that: The following steps are involved: preparing a precursor slurry for a solid electrolyte; An electrode sheet is obtained, the precursor slurry is deposited on the surface of the electrode sheet, and then the precursor is reacted to generate the solid electrolyte by heating under the protection of an inert atmosphere, thereby forming an in-situ solid electrolyte membrane on the surface of the electrode sheet.

2. The solid electrolyte film forming process according to claim 1, wherein: The precursor slurry includes at least one of an inorganic solid electrolyte precursor material and a polymer solid electrolyte precursor material; And / or, the solvent in the precursor slurry includes at least one of acetonitrile, N,N-dimethylformamide, toluene, tetrahydrofuran, N-methylpyrrolidone, heptane, and deionized water.

3. The solid electrolyte film forming process according to claim 2, wherein: The precursor material of the inorganic solid electrolyte includes a halide precursor or a sulfide precursor; And / or, the precursor material of the polymer solid electrolyte includes a polymer monomer, an initiator and a lithium salt.

4. The solid electrolyte film forming process according to claim 3, wherein: The halide precursor includes LiX and MX, wherein X is selected from at least one halogen selected from F, Cl, and Br, and M is selected from at least one halogen selected from In, Y, Zr, Sc, Er, Al, and Fe; And / or, the sulfide precursor includes lithium sulfide and phosphorus sulfide.

5. The solid electrolyte film forming process according to claim 4, characterized in that: The mass ratio of the LiX to the MX is (2-4):1; And / or, the mass ratio of lithium sulfide to phosphorus sulfide is (3-13):(1-4).

6. The solid electrolyte film forming process according to any one of claims 3 to 5, characterized in that: The polymer monomer includes at least one of an acrylic acid ester monomer, an ethylene oxide-containing monomer, a vinylidene fluoride monomer, an ether-containing monomer, and a carbonate-containing monomer; And / or, the initiator includes at least one of a photoinitiator and a thermal initiator; And / or, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium bis(oxalatoborate); and / or, the mass ratio of the polymer monomer to the initiator is 100:(0.2-2); And / or, the mass ratio of the polymer monomer to the lithium salt is 1:(0.25-1).

7. The solid electrolyte film forming process according to claim 6, characterized in that: The precursor slurry is mixed at a temperature of 50° C. to 80° C. And / or, the temperature condition of the heating treatment is 200° C. to 220° C., and the duration is 2 min to 10 min.

8. The solid electrolyte film forming process according to claim 7, wherein: After the precursor reacts to generate the solid electrolyte, a roller pressing process is performed using a pressure of 20 MPa to 60 MPa.

9. The solid electrolyte film forming process according to claim 8, wherein: The thickness of the solid electrolyte membrane is 10 μm to 130 μm.

10. A solid-state battery, characterized in that: The surface of the electrode sheet of the solid-state battery has a solid electrolyte membrane prepared according to the solid electrolyte membrane forming process according to any one of claims 1 to 9.

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