A high-voltage resistant polymer solid electrolyte and its preparation method and solid-state battery

Abstract

This application provides a high-voltage resistant polymer solid electrolyte, its preparation method, and a solid-state battery. The electrolyte membrane includes a polymer solid electrolyte, a lithium salt, and additives. The additives include phosphorus-containing additives and boron-containing additives. The boron-containing additives include boron anions. The mass ratio of the phosphorus-containing additive to the polymer solid electrolyte is 5:100-20:100, and the mass ratio of the boron-containing additive to the polymer solid electrolyte is 5:100-16:100. According to the embodiments of this application, the room temperature ionic conductivity of the electrolyte membrane can be improved, and the interfacial stability between the electrolyte membrane and the electrode can be improved, resulting in good rate performance and cycle performance of the solid-state battery cell.

Description

Technical Field

[0001] This application relates to a high-voltage resistant polymer solid electrolyte, its preparation method, and a solid-state battery. Background Technology

[0002] Traditional lithium-ion batteries generally use liquid electrolytes, although they have high room temperature ionic conductivity (approximately 10). 2 While liquid electrolytes have a capacity of S / cm, their main component is a flammable organic solvent, posing safety hazards such as leakage, volatilization, and thermal runaway. Especially under conditions of overcharging, short circuits, or mechanical abuse, liquid electrolytes are highly susceptible to fire and even explosion, severely limiting the further application of lithium-ion batteries in fields requiring high energy density and high safety (such as electric vehicles and energy storage systems). Therefore, developing next-generation high-safety solid-state electrolytes has become a consensus in academia and industry.

[0003] Solid electrolytes mainly include two categories: inorganic and polymer solid electrolytes. However, polymer solid electrolytes generally have low room temperature ionic conductivity and suffer from significant interface problems. Summary of the Invention

[0004] This application provides a high-voltage resistant polymer solid electrolyte, its preparation method, and a solid-state battery. It can improve the room temperature ionic conductivity of the electrolyte membrane, improve the interfacial stability between the electrolyte membrane and the electrode, and enable the solid-state battery cell to have good rate performance and cycle performance.

[0005] In one aspect, embodiments of this application provide a solid-state battery cell, comprising a positive electrode, an electrolyte membrane, and a negative electrode. The electrolyte membrane is located between the positive and negative electrode. The electrolyte membrane comprises a polymer solid electrolyte, a lithium salt, and additives. The additives include phosphorus-containing additives and boron-containing additives. The boron-containing additives include boron anions. The mass ratio of the phosphorus-containing additives to the polymer solid electrolyte is 5:100-20:100, and the mass ratio of the boron-containing additives to the polymer solid electrolyte is 2:100. 20:100.

[0006] In some embodiments, the mass ratio of the phosphorus-containing additive to the polymer solid electrolyte is 5:100-12.5:100.

[0007] In some embodiments, the mass ratio of the boron-containing additive to the polymer solid electrolyte is 5:100-16:100.

[0008] In some embodiments, the mass ratio of the phosphorus-containing additive to the boron-containing additive is 1:1 to 1:2.

[0009] In some embodiments, the phosphorus-containing additive includes one or more of lithium difluorodioxarate phosphate, lithium difluorophosphate, lithium trioxarate phosphate, lithium tetrafluorooxarate phosphate, lithium hexafluorophosphate, and lithium difluorooxarate phosphate.

[0010] In some embodiments, the boron-containing additive includes one or more of lithium difluorooxalate borate, lithium dioxalate borate, lithium tetrafluoroborate, lithium oxalate borate, and lithium trifluoroethyl borate.

[0011] In some embodiments, the crystallinity of the polymer solid electrolyte is 15%-50%.

[0012] In some embodiments, the lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(difluorosulfonyl)imide, lithium perchlorate, and lithium hexafluorophosphate.

[0013] In some embodiments, the polymer solid electrolyte includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polymethyl methacrylate, polyethylene, polypropylene glycol, polyethylene glycol methyl ether acrylate, and poly(1,3-dioxolane).

[0014] In some embodiments, the electrolyte membrane further includes a gel polymer containing an organic solvent, the organic solvent including organophosphorus solvents and non-organophosphorus solvents, the organophosphorus solvent including one or more of triethyl phosphate, trimethyl phosphate and tributyl phosphate, and the non-organophosphorus solvent including one or more of N,N-dimethylformamide, N-methylpyrrolidone, acetonitrile, acetone, dimethyl carbonate, ethylene carbonate, diethyl carbonate and tetrahydrofuran.

[0015] In some embodiments, the negative electrode includes a negative current collector and a lithium-based metal layer located on at least one surface of the negative current collector, wherein the lithium-based metal layer includes one or more of metallic lithium and lithium alloys.

[0016] In some embodiments, the thickness of the lithium-based metal layer is 1 μm - 50 μm.

[0017] Secondly, embodiments of this application provide an electrolyte membrane comprising a polymer solid electrolyte, a lithium salt, and additives. The additives include phosphorus-containing additives and boron-containing additives. The boron-containing additives include boron anions. The mass ratio of the phosphorus-containing additives to the polymer solid electrolyte is 5:100-20:100, and the mass ratio of the boron-containing additives to the polymer solid electrolyte is 2:100. 16:100.

[0018] Thirdly, embodiments of this application provide a method for preparing the electrolyte membrane described in the second aspect, wherein polymer monomers, lithium salts, boron-containing additives, phosphorus-containing additives and initiators are dissolved in an organic solvent and uniformly mixed to obtain a precursor solution; the precursor solution is injected into the inner cavity of the battery cell or coated on the surface of the electrode assembly, and an in-situ polymerization reaction is initiated by heating or ultraviolet light irradiation to form an electrolyte membrane. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The diagram shows a schematic of a battery cell provided in some embodiments of this application.

[0021] Figure 2 A schematic diagram of an electrical device provided in some embodiments of this application is shown.

[0022] Figure 3 The Raman spectra of the electrolyte membranes in Example 1 and Comparative Example 1 of this application are shown.

[0023] Figure 4 The XPS spectrum of the SEI film of the battery cell in Embodiment 1 of this application is shown.

[0024] Figure 5 SEM images of the electrolyte membranes of Example 1 and Comparative Example 1 of this application are shown. Detailed Implementation

[0025] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0026] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0027] The following detailed description, with appropriate reference to the accompanying drawings, discloses a high-voltage resistant polymer solid electrolyte, its preparation method, and embodiments of a solid-state battery. However, unnecessary details may be omitted. For example, detailed descriptions of well-known facts and repetitive descriptions of identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0028] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0029] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0030] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0031] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0032] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0033] Unless otherwise specified, this application uses conventional testing methods or testing methods recommended by the instrument.

[0034] Polymer electrolytes still face several key challenges in practical applications: On the one hand, the semi-crystalline nature of some polymers leads to easy phase separation between the polymer and lithium salt, forming discontinuous ion transport channels, resulting in generally low room temperature ionic conductivity (typically ≤10). 4 S / cm); On the other hand, highly polar organic solvents (such as N,N-dimethylformamide, DMF) are often used in the preparation process to dissolve the polymer and lithium salt. These solvents are difficult to completely remove, and the residual solvent reacts with Li + Forming strongly interacting [Li(DMF)] x ] + Solvation structure. During battery cycling, especially at high voltage or high current density, this structure undergoes desolvation at the electrode / electrolyte interface, leading to the accumulation of free solvent molecules at the interface. These molecules then undergo violent side reactions with the negative electrode, forming an unstable solid electrolyte interphase (SEI) film. This results in a series of problems, including interfacial side reactions, decreased coulombic efficiency, and reduced cycle life.

[0035] Therefore, this application constructs an electrolyte membrane with high ionic conductivity, excellent interfacial stability, good mechanical properties and high voltage resistance through the synergistic effect of phosphorus-containing additives and boron-containing additives.

[0036] This application provides an electrolyte membrane comprising a polymer solid electrolyte, a lithium salt, and additives. The additives include phosphorus-containing additives and boron-containing additives. The boron-containing additives include boron anions. The mass ratio of the phosphorus-containing additives to the polymer solid electrolyte is 5:100-20:100, and the mass ratio of the boron-containing additives to the polymer solid electrolyte is 2:100. 20:100.

[0037] The high binding energy between boron-containing anions and lithium ions gives them a high affinity for lithium ions, enabling them to participate in lithium oxide formation. + During the solvation process, the reaction between DMF solvent and Li is effectively weakened. + The strong interaction between [Li(DMF)] will transform the traditional solvent-dominated [Li(DMF)]... x ] + The structure transforms into an anion-dominated "anion-derived solvation structure." This structural transformation allows boron-containing anions in the solvation sheath to decompose preferentially at the electrode interface over solvent molecules during battery charging and discharging. On the negative electrode side, the decomposition products of boron-containing anions can construct an inner SEI rich in inorganic components and an outer SEI rich in flexible organic components. This bilayer SEI structure possesses both high mechanical strength and flexibility, effectively suppressing lithium dendrite growth and adapting to electrode volume changes, thus greatly improving interface stability. On the positive electrode side, the decomposition of boron-containing anions can also form a stable CEI film, protecting the structure of the positive electrode active material and inhibiting transition metal dissolution, thereby broadening the electrochemical window of the electrolyte membrane and enabling it to match high-voltage positive electrode active materials.

[0038] The mass ratio of boron-containing additives to polymer solid electrolytes is 2:100. 20:100 can be, for example, 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, 11:100, 12:100, 13:100, 14:100, 15:100, 16:100, 17:100, 18:100, 19:100, 20:100, or any range of the above values. If there is too little boron-containing additive (e.g., the mass ratio of boron-containing additive to polymer solid electrolyte is less than 2:100), the solvation modification effect will be insufficient, making it difficult to effectively construct the above-mentioned bilayer SEI film; if there is too much boron-containing additive (e.g., the mass ratio is greater than 20:100), it is easy to concentrate in the polymer matrix, causing it to undergo a rapid reduction reaction at the electrode interface, resulting in local instantaneous growth of the SEI film, which cannot form a continuous and flat film, thus being detrimental to interface stability.

[0039] In this application, the mass ratio of boron-containing additives to polymer solid electrolytes is controlled within the range of 2:100 to 20:100. When the mass ratio is greater than or equal to 2:100, solvation modification can be effectively achieved, forming a bilayer SEI film rich in inorganic components as the inner layer and flexible organic components as the outer layer, thus improving the mechanical strength and flexibility of the SEI film. When the mass ratio is less than or equal to 20:100, the boron-containing additives can be ensured to be uniformly distributed in the polymer matrix, forming a continuous and flat SEI film. Therefore, the interfacial stability, mechanical properties, and high-pressure resistance of the electrolyte membrane can be significantly improved.

[0040] Optionally, the mass ratio of boron-containing additives to polymer solid electrolytes is 5:100-16:100.

[0041] The mass ratio of phosphorus-containing additives to polymer solid electrolytes is 5:100-20:100, for example, 5:100, 10:100, 20:100, or any combination of these values. The phosphorus-containing additives preferentially decompose on the surface of the positive electrode active material, forming a Li-rich layer. PO A dense CEI film, such as Li3P, protects the structure of the positive electrode active material and inhibits transition metal dissolution. However, excessive phosphorus additives can lead to high viscosity of the electrolyte film, thereby reducing its strength and increasing the risk of lithium dendrites puncturing it. In the embodiments of this application, the mass ratio of phosphorus additives to polymer solid electrolyte is greater than or equal to 5:100, which can form a dense CEI film. In the embodiments of this application, the mass ratio of phosphorus additives to polymer solid electrolyte is less than or equal to 20:100, which can make the electrolyte film have high strength. In addition, in the early stage of thermal runaway, the decomposition products of phosphorus additives can capture hydrogen free radicals and interrupt the chain combustion reaction. This can improve the interfacial stability, mechanical stability, and thermal stability of the electrolyte film.

[0042] Optionally, the mass ratio of phosphorus-containing additives to polymer solid electrolytes is 5:100-12.5:100.

[0043] Boron-containing additives with the above-mentioned appropriate mass ratio can increase the number of free Li in the system by promoting the dissociation of lithium salts. Concentration. This allows for the formation of a denser CEI film even with a smaller mass percentage of phosphorus-containing additives. The smaller mass percentage of phosphorus-containing additives also improves the mechanical strength of the electrolyte membrane, thereby further enhancing its interfacial stability, mechanical stability, and thermal stability.

[0044] In some embodiments, the mass ratio of the phosphorus-containing additive to the boron-containing additive is 1:1 to 1:2. For example, it can be 1:1, 1:1.5, 1:2, or any range of the above values. Having the above mass ratio of phosphorus-containing and boron-containing additives can result in the electrolyte membrane exhibiting better interfacial stability, mechanical stability, and thermal stability.

[0045] In some embodiments, the phosphorus-containing additive includes one or more of lithium difluorobis(oxalate) phosphate, lithium difluorophosphate, lithium tri(oxalate) phosphate, lithium tetrafluoro(oxalate) phosphate, lithium hexafluorophosphate, and lithium difluoro(oxalate) phosphate.

[0046] In some embodiments, the boron-containing additive includes one or more of lithium difluorooxalate borate, lithium dioxalate borate, lithium tetrafluoroborate, lithium oxalate borate, and lithium trifluoroethylborate.

[0047] The semi-crystalline nature of polymers makes it easy for phase separation to occur between the polymer and the lithium salt, forming discontinuous ion transport channels, resulting in generally low ionic conductivity at room temperature.

[0048] In some embodiments, the lithium salt exhibits a high degree of charge delocalization. The lithium salt in the embodiments of this application has a high degree of charge delocalization, which can promote lithium salt dissociation and increase the free Li in the electrolyte membrane. + The quantity increases, thereby improving the ionic conductivity of the electrolyte membrane.

[0049] In some embodiments, the lithium salt comprises anion, and the anion has a relatively large volume. The larger the anion, the greater the steric hindrance, and the more difficult it is to react with Li. Close proximity inhibits ion pair aggregation and increases the concentration of free Li in the electrolyte membrane. The amount of lithium salt increases the ionic conductivity of the electrolyte membrane. Optionally, the lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(difluorosulfonyl)imide, lithium perchlorate, and lithium hexafluorophosphate. In some embodiments, the lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(difluorosulfonyl)imide, lithium perchlorate, and lithium hexafluorophosphate.

[0050] In some embodiments, the crystallinity of the polymer solid electrolyte is 15%-50%, for example, it can be 15%, 20%, 30%, 40%, or any combination of the above values. The crystallinity of the polymer solid electrolyte affects the dispersion uniformity of the additives, thereby affecting the effectiveness of the additives. If the crystallinity of the polymer solid electrolyte is too high, the additives will be squeezed into the amorphous regions, resulting in excessively high local additive concentrations, triggering side reactions, while the crystalline regions become "additive deserts," and the interface protection fails. In the embodiments of this application, the crystallinity of the polymer solid electrolyte is greater than or equal to 15%, which can give the electrolyte membrane a certain strength and reduce the risk of lithium dendrite puncture; in the embodiments of this application, the crystallinity of the polymer solid electrolyte is less than or equal to 50%, which can make the additives dispersed uniformly and better improve the interface stability, mechanical stability, high voltage resistance, and thermal stability of the electrolyte membrane.

[0051] In some embodiments, the polymer solid electrolyte includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polymethyl methacrylate, polyethylene, polypropylene glycol, polyethylene glycol methyl ether acrylate, and poly(1,3-dioxolane).

[0052] In some embodiments, the electrolyte membrane further includes a gel polymer, the gel polymer containing an organic solvent, the organic solvent including organophosphorus solvents and non-organophosphorus solvents, the organophosphorus solvent including one or more of triethyl phosphate (TEP), trimethyl phosphate (TMP) and tripropyl phosphate (TBP), and the non-organophosphorus solvent including N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), acetonitrile (ACN), acetone (AC), dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC) and tetrahydrofuran (THF).

[0053] The gel polymer in this embodiment has a chemically and / or physically cross-linked network structure, which encapsulates a large amount of solvent, thus exhibiting a soft and elastic state. This can improve the interface performance between the electrolyte membrane and the electrode.

[0054] In some embodiments, the electrolyte membrane includes a self-supporting electrolyte membrane and / or a gel electrolyte membrane.

[0055] Self-supporting electrolyte membranes can be obtained through the following preparation methods: A-S1. The polymer monomer, lithium salt, boron-containing additive, phosphorus-containing additive and initiator are dissolved in an organic solvent and mixed evenly to obtain a precursor solution; A-S2. The precursor solution is injected into the battery or coated on the electrode surface, and an in-situ polymerization reaction is initiated by heating or ultraviolet light irradiation to form a self-supporting electrolyte membrane.

[0056] Self-supporting electrolyte membranes can also be obtained through the following preparation methods: B-S1. The polymer solid electrolyte, lithium salt, boron-containing additive and phosphorus-containing additive are dissolved in an organic solvent and mixed evenly to obtain an electrolyte slurry; B-S2. The obtained electrolyte slurry is uniformly coated onto a glass plate and dried in a vacuum oven to obtain a self-supporting electrolyte membrane of uniform thickness.

[0057] In step B-S1, the mass ratio of lithium salt to polymer solid electrolyte is 80:100-110:100, the mass percentage of polymer solid electrolyte to organic solvent is 10:100-30:100, the mass percentage of boron-containing additive to polymer is 2:100-20:100, and the mass ratio of phosphorus-containing additive to polymer is 5:100-20:100.

[0058] In step B-S1, the uniform mixing method is one or more of magnetic stirring and ball milling; the uniform mixing time is 12-24 hours.

[0059] In step B-S2, the drying temperature in the vacuum oven is 60-90℃, and the drying time is 24-48h. The vacuum oven is opened for ventilation on the 3rd and 6th hours of drying. The thickness of the finally obtained self-supporting electrolyte membrane is 50-100μm.

[0060] Gel electrolyte membranes can be obtained by dissolving polymer electrolytes, gel polymers, lithium salts and additives in an organic solvent, mixing them uniformly, allowing the gel electrolyte to absorb the liquid and swell, and then forming a gel electrolyte layer.

[0061] The solid-state battery cells mentioned in the embodiments of this application can independently perform charging and discharging functions. Solid-state battery cells can be cylindrical, cuboid, or other shapes, etc., and the embodiments of this application are not limited in this respect. Figure 1 This is an example of a rectangular solid-state battery cell 5.

[0062] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple solid-state battery cells, which are connected in series, parallel, or mixed connections via busbars.

[0063] In some embodiments, a battery cell assembly is typically formed by arranging multiple solid-state battery cells.

[0064] As an example, a battery cell assembly can be a battery module, which consists of multiple solid-state battery cells arranged and fixed together to form an independent module. As another example, a battery module can be formed by bundling multiple solid-state battery cells together with cable ties.

[0065] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0066] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0067] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple solid-state battery cells to the housing.

[0068] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0069] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0070] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0071] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use solid-state battery cells and battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. Solid-state battery cells and battery devices are used to store or provide electrical energy.

[0072] Figure 2 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0073] The solid-state battery cells in this application may include hard-shell solid-state battery cells, soft-pack solid-state battery cells, etc.

[0074] [Positive electrode plate] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer located on at least one side of the positive current collector, the positive active material layer including a positive active material.

[0075] In some embodiments, the positive current collector may be a metal foil or a composite current collector. The metal foil may be a pure metal, an alloy, or a surface-treated metal, such as, but not limited to, stainless steel foil, carbon-coated aluminum foil, or aluminum foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene.

[0076] In some embodiments, the positive electrode active material may include one or more of lithium transition metal oxides and their modified forms, lithium phosphates and their modified forms, lithium titanate, lithium niobate, sulfur, selenium, and tellurium.

[0077] Optionally, examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and lithium-rich manganese-based materials.

[0078] Optionally, examples of lithium phosphates may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0079] In some embodiments, to further improve the energy density of a solid-state battery cell, the positive electrode active material includes materials with the general formula Li. a Ni b Co c M d O e A f One or more of lithium transition metal oxides and their modified materials. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A may include one or more of N, F, S, and Cl. Optionally, 0.6≤b<1, 0.8≤b<1.

[0080] As an example, positive electrode active materials may include, but are not limited to, LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.83 Co 0.12 Mn 0.05 O2 (abbreviated as NCM83), LiNi 0.9 Co 0.05 Mn 0.05 O2 (Ni90), LiNi 0.92 Co 0.04 Mn 0.04 O2 (Ni92), LiNi 0.93 Co 0.035 Mn 0.035 O2 (Ni93), LiNi 0.96 Co 0.02 Mn 0.02 O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 O2, and one or more of their respective modified materials.

[0081] The modified materials for the above-mentioned positive electrode active materials can be doped and / or surface coated.

[0082] In some embodiments, the positive electrode active material layer also includes a solid electrolyte.

[0083] In some embodiments, the solid electrolyte may include one or more of the following: sulfide solid electrolyte, halide solid electrolyte, oxide solid electrolyte, and polymer solid electrolyte.

[0084] Optionally, the sulfide solid electrolyte may include Li 6+m+l P 1-m M m S 5-n+l N n Y1-l The material, with the molecular formula Li 10±δ Ge 1-g G g P 2-q Q q S 12-w W w Materials, Li 4-v Ge 1-v P v One or more of the following materials: S4, Li2S-P2S5, Li2S-SiS2, Li2S-MeS-P2S5, and LiGeGaS; 0 ≤ m < 1, 0 ≤ n < 1, -1 < l < 1; M includes one or more elements of Ge, Si, Sn, Al, Zr, and Sb; N includes one or more elements of O, Se, and Te; Y includes one or more elements of Cl, Br, and I; 0 ≤ δ < 1, 0 ≤ g ≤ 1, 0 ≤ q ≤ 2, 0 ≤ w < 1; G includes one or two elements of Si and Sn; Q includes Sb; W includes one or more elements of O, Se, Te, Cl, Br, and I; 0 < v < 1; Me includes one or more elements of Si, Ge, Sn, and Al.

[0085] As an example, sulfide electrolytes may include Li6PS5Cl, Li6PS5Br, Li6PS5I, and Li6PS5Cl. 0.5 Br 0.5 Li 5.5 PS 4.5 Cl 1.5 Li 5.5 PS 4.5 Br 1.5 Li 10 GeP2S 12 Li3PS4, Li7P3S 11 Li 3.25 Ge 0.25 P 0.75 S4, Li6GaGe2S 10 One or more of the following. Optionally, the sulfide electrolyte may include Li6PS5Cl, Li6PS5Br, Li6PS5I, Li6PS5Cl 0.5 Br 0.5 Li 5.5 PS 4.5 Cl 1.5 Li 5.5 PS 4.5 Br 1.5 Li 10 GeP2S 12 One or more of them.

[0086] Optionally, the halide solid electrolyte may be one or more of Li3YCl6, Li3YBr6, Li3ErCl6, Li3InCl6, and Li3InBr6, including but not limited to.

[0087] Optionally, the oxide solid electrolyte may include one or more of the following: NASICON type solid electrolyte, LISICON type solid electrolyte, perovskite type solid electrolyte, and garnet type solid electrolyte.

[0088] As an example, oxide solid electrolytes may include, but are not limited to, Li5La3Ti2O 12 Li7La3Zr2O 12 Li4Ti5O 12 Li 14 Zn(GeO4)4, LiTi2(PO4)3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+y Al y Ge 2-y One or more of (PO4)3, 0 < x < 2, 0 < y < 2.

[0089] Optionally, the polymer solid electrolyte can be formed by complexing a polymer matrix material with a lithium salt. Optionally, the polymer matrix material can be one or more of, but not limited to, polyethylene oxide (PEO) and its derivatives, polypropylene oxide (PPO) and its derivatives, polycarbonate (PPC), polyacrylonitrile (PAN), polysiloxane (PDMS), polyvinylidene fluoride (PVDF), and polymethyl methacrylate (PMMA). Optionally, the lithium salt can be one or more of, but not limited to, LiClO4, LiAsF4, LiPF6, LiBF4, LiTFSI, and LiFSI.

[0090] Optionally, the polymer solid electrolyte may also include an inert filler, which can reduce the crystallinity of the polymer and improve its mechanical properties. Optionally, the inert filler may include, but is not limited to, one or more of TiO2, Al2O3, ZrO2, and SiO2.

[0091] In some embodiments, the positive electrode active material layer further includes a positive electrode conductive agent.

[0092] Optionally, the positive electrode conductive agent may be one or more of the following, including but not limited to superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes (CNTs), graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0093] In some embodiments, the positive electrode active material layer further includes a positive electrode binder.

[0094] Optionally, the positive electrode binder may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, methyl vinyl silicone rubber, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), thermoplastic styrene-butadiene rubber (SBS), isoprene rubber, butadiene rubber (BR), ethyl cellulose, fluororubber, and acrylate rubber.

[0095] [Negative electrode plate] In some embodiments, the negative electrode may include one or more of lithium, lithium alloy, natural graphite, artificial graphite, mesophase micro carbon spheres, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and metal oxides.

[0096] In some embodiments, the negative electrode can be a metal sheet, such as a lithium sheet or a lithium alloy sheet.

[0097] Optionally, other elements in the lithium alloy sheet may include, but are not limited to, one or more of In, Mg, Al, Zn, Sn, Ag, Au, Ga, Pt, and Fe.

[0098] Alternatively, the lithium alloy sheet may include, but is not limited to, In-Li alloy sheet, Li-Mg alloy sheet, Li-Al alloy sheet, Li-Zn alloy sheet, Li-Fe alloy sheet, etc.

[0099] In some embodiments, the negative electrode may include a negative electrode current collector and a lithium-based metal layer located on at least one surface of the negative electrode current collector. The lithium-based metal layer may be metallic lithium or a lithium alloy. The negative electrode current collector has two surfaces opposite each other in its thickness direction, and the lithium-based metal layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0100] Optionally, other elements in the lithium alloy may include, but are not limited to, one or more of In, Mg, Al, Zn, Sn, Ag, Au, Ga, Pt, and Fe.

[0101] Alternatively, the lithium alloy may include, but is not limited to, In-Li alloy, Li-Mg alloy, Li-Al alloy, Li-Zn alloy, Li-Fe alloy, etc.

[0102] In some embodiments, the negative electrode may include a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material. The negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0103] Optionally, the negative electrode active material may include, but is not limited to, one or more of the following: natural graphite, artificial graphite, mesophase micro carbon spheres, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and metal oxides.

[0104] Optionally, the silicon-based material may include, but is not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Optionally, the tin-based material may include, but is not limited to, one or more of elemental tin, tin oxide, and tin alloys. Optionally, the metal oxide may include, but is not limited to, one or more of TiO2, MoO2, In2O3, Al2O3, Cu2O, VO2, Ga2O3, Sb2O5, and Bi2O5.

[0105] In some embodiments, the negative electrode active material layer further includes a negative electrode binder.

[0106] Optionally, the negative electrode binder may include, but is not limited to, one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS), methyl vinyl silicone rubber, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), thermoplastic styrene-butadiene rubber (SBS), isoprene rubber, cis-butadiene rubber (BR), ethyl cellulose, fluororubber, and acrylate rubber.

[0107] In some embodiments, the negative electrode active material layer may or may not include a negative electrode conductive agent.

[0108] Optionally, the negative electrode conductive agent may be one or more of the following, including but not limited to superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes (CNTs), graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0109] In some embodiments, the negative electrode may or may not include a solid electrolyte.

[0110] In some embodiments, the negative electrode active material layer includes a solid electrolyte, which includes one or more of sulfide solid electrolytes, halide solid electrolytes, and oxide solid electrolytes. The types of sulfide solid electrolytes, halide solid electrolytes, and oxide solid electrolytes can be found above and will not be repeated here.

[0111] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. The metal foil may be a pure metal, an alloy, or a surface-treated metal, such as, but not limited to, stainless steel foil, copper foil, and nickel foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. As an example, the metal layer may include, but is not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0112] The negative electrode can be prepared by either a dry process or a wet process.

[0113] Electrolyte membranes can be prepared using either dry or wet processes.

[0114] In some embodiments, the solid-state battery cell may further include an outer packaging for accommodating the negative electrode, electrolyte membrane, and positive electrode assembly. The outer packaging may be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging may also be a flexible package, such as a pouch. The material of the flexible package may be plastic, such as aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS) or one or more of these materials.

[0115] [Preparation methods for solid-state battery cells] The preparation methods of solid-state battery cells are well known. For example, the assembly methods of solid-state battery cells include, but are not limited to, hard-case batteries and soft-pack batteries.

[0116] Example The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0117] Example 1 Preparation of electrolyte membranes In an argon-filled glove box, 2g of the polymer solid electrolyte polyvinylidene fluoride (PVDF), 0.2g of the boron-containing additive lithium difluorooxalate borate (LiDFOB), and 0.1g of the phosphorus-containing additive lithium difluorooxalate phosphate (LiDFBOP) were weighed and dissolved in 13mL of anhydrous DMF solvent. At the same time, 1.8g of LiTFSI was added. The mixture was magnetically stirred at 60℃ for 12 hours to form a uniform and transparent electrolyte slurry. The electrolyte slurry was slowly cast onto a clean glass plate and then evenly coated with a scraper. The coated glass plate was then transferred to a vacuum drying oven at 60℃ and dried for 24 hours to remove the solvent, resulting in an electrolyte membrane with a thickness of approximately 50μm.

[0118] Preparation of symmetric cells The electrolyte membrane described above is placed between the positive and negative electrodes to assemble a Li||Li symmetric cell.

[0119] Preparation of solid-state battery cells Preparation of positive electrode sheet Lithium iron phosphate, the positive electrode active material, and vapor-grown carbon fiber (VGCF), the positive electrode conductive agent, are mixed evenly at a solid mass ratio of 97:3. Then, 1% of the mass of polytetrafluoroethylene (PTFE), a binder, is added. The mixture is heated on a heating table at 80°C and rolled back and forth to form a dry positive electrode active material layer. Finally, it is combined with aluminum foil hot rollers for the positive electrode current collector to obtain the positive electrode sheet.

[0120] Preparation of negative electrode sheet Lithium metal sheet is used as the negative electrode.

[0121] Preparation of soft-pack solid-state battery cells The negative electrode, the electrolyte membrane, and the positive electrode are stacked sequentially from bottom to top to obtain the electrode assembly. After being subjected to 600MPa isostatic pressing, the electrode assembly is encapsulated in an aluminum-plastic bag to obtain a soft-pack solid-state battery cell.

[0122] Comparative Example 1 The experimental steps are basically the same as in Example 1, except that the preparation of the electrolyte membrane is different, in which the additives are omitted.

[0123] Preparation of electrolyte membranes In an argon-filled glove box, 2g of the polymer solid electrolyte polyvinylidene fluoride (PVDF) was weighed and dissolved in 13mL of anhydrous DMF solvent. At the same time, 1.8g of LiTFSI was added. The mixture was magnetically stirred at 60℃ for 12 hours to form a uniform and transparent electrolyte slurry. The electrolyte slurry was slowly cast onto a clean glass plate and then evenly coated with a scraper. The coated glass plate was then transferred to a vacuum drying oven at 60℃ and dried for 24 hours to remove the solvent, resulting in an electrolyte membrane with a thickness of approximately 50μm.

[0124] Comparative Example 2 The experimental steps are basically the same as in Example 1, except that the preparation of the electrolyte membrane is different, in which boron-containing additives are omitted.

[0125] Preparation of electrolyte membranes In an argon-filled glove box, 2g of the polymer solid electrolyte polyvinylidene fluoride (PVDF) and 0.1g of the phosphorus-containing additive lithium difluorobis(oxalato) phosphate (LiDFBOP) were weighed and dissolved in 13mL of anhydrous DMF solvent. At the same time, 1.8g of LiTFSI was added. The mixture was magnetically stirred at 60℃ for 12 hours to form a uniform and transparent electrolyte slurry. The electrolyte slurry was slowly cast onto a clean glass plate and then evenly coated with a scraper. The coated glass plate was then transferred to a vacuum drying oven at 60℃ and dried for 24 hours to remove the solvent, resulting in an electrolyte membrane with a thickness of approximately 50μm.

[0126] Comparative Example 3 The experimental steps are basically the same as in Example 1, except that the preparation of the electrolyte membrane is different, in which the phosphorus-containing additive is omitted.

[0127] Preparation of electrolyte membranes In an argon-filled glove box, 2g of the polymer solid electrolyte polyvinylidene fluoride (PVDF) and 0.2g of the boron-containing additive lithium difluorooxalate borate (LiDFOB) were weighed and dissolved in 13mL of anhydrous DMF solvent. At the same time, 1.8g of LiTFSI was added. The mixture was magnetically stirred at 60℃ for 12 hours to form a uniform and transparent electrolyte slurry. The electrolyte slurry was slowly cast onto a clean glass plate and then evenly coated with a scraper. The coated glass plate was then transferred to a vacuum drying oven at 60℃ and dried for 24 hours to remove the solvent, resulting in an electrolyte membrane with a thickness of approximately 50μm.

[0128] Comparative Example 4 The experimental steps were basically the same as in Example 1, except that the preparation of the electrolyte membrane was different. The mass ratio of the phosphorus-containing additive to the polymer solid electrolyte in the preparation of the electrolyte membrane was too large.

[0129] Preparation of electrolyte membranes In an argon-filled glove box, 2g of the polymer solid electrolyte polyvinylidene fluoride (PVDF), 0.2g of the boron-containing additive lithium difluorooxalate borate (LiDFOB), and 0.5g of the phosphorus-containing additive lithium difluorooxalate phosphate (LiDFBOP) were weighed and dissolved in 13mL of anhydrous DMF solvent. At the same time, 1.8g of LiTFSI was added. The mixture was magnetically stirred at 60℃ for 12 hours to form a uniform and transparent electrolyte slurry. The electrolyte slurry was slowly cast onto a clean glass plate and then evenly coated with a scraper. The coated glass plate was then transferred to a vacuum drying oven at 60℃ and dried for 24 hours to remove the solvent, resulting in an electrolyte membrane with a thickness of approximately 50μm.

[0130] Comparative Example 5 The experimental steps were basically the same as in Example 1, except that the preparation of the electrolyte membrane was different. The mass ratio of the phosphorus-containing additive to the polymer solid electrolyte in the preparation of the electrolyte membrane was too small.

[0131] Preparation of electrolyte membranes In an argon-filled glove box, 2g of the polymer solid electrolyte polyvinylidene fluoride (PVDF), 0.2g of the boron-containing additive lithium difluorooxalate borate (LiDFOB), and 0.05g of the phosphorus-containing additive lithium difluorooxalate phosphate (LiDFBOP) were weighed and dissolved in 13mL of anhydrous DMF solvent. At the same time, 1.8g of LiTFSI was added. The mixture was magnetically stirred at 60℃ for 12 hours to form a uniform and transparent electrolyte slurry. The electrolyte slurry was slowly cast onto a clean glass plate and then evenly coated with a scraper. The coated glass plate was then transferred to a vacuum drying oven at 60℃ and dried for 24 hours to remove the solvent, resulting in an electrolyte membrane with a thickness of approximately 50μm.

[0132] Comparative Example 6 The experimental steps were basically the same as in Example 1, except that the preparation of the electrolyte membrane was different. The mass ratio of the boron-containing additive to the polymer solid electrolyte in the preparation of the electrolyte membrane was too large.

[0133] Preparation of electrolyte membranes In an argon-filled glove box, 2g of the polymer solid electrolyte polyvinylidene fluoride (PVDF), 0.5g of the boron-containing additive lithium difluorooxalate borate (LiDFOB), and 0.1g of the phosphorus-containing additive lithium difluorooxalate phosphate (LiDFBOP) were weighed and dissolved in 13mL of anhydrous DMF solvent. At the same time, 1.8g of LiTFSI was added. The mixture was magnetically stirred at 60℃ for 12 hours to form a uniform and transparent electrolyte slurry. The electrolyte slurry was slowly cast onto a clean glass plate and then evenly coated with a scraper. The coated glass plate was then transferred to a vacuum drying oven at 60℃ and dried for 24 hours to remove the solvent, resulting in an electrolyte membrane with a thickness of approximately 50μm.

[0134] Comparative Example 7 The experimental steps were basically the same as in Example 1, except that the preparation of the electrolyte membrane was different. The mass ratio of the boron-containing additive to the polymer solid electrolyte in the preparation of the electrolyte membrane was too small.

[0135] Preparation of electrolyte membranes In an argon-filled glove box, 2g of the polymer solid electrolyte polyvinylidene fluoride (PVDF), 0.02g of the boron-containing additive lithium difluorooxalate borate (LiDFOB), and 0.1g of the phosphorus-containing additive lithium difluorooxalate phosphate (LiDFBOP) were weighed and dissolved in 13mL of anhydrous DMF solvent. At the same time, 1.8g of LiTFSI was added. The mixture was magnetically stirred at 60℃ for 12 hours to form a uniform and transparent electrolyte slurry. The electrolyte slurry was slowly cast onto a clean glass plate and then evenly coated with a scraper. The coated glass plate was then transferred to a vacuum drying oven at 60℃ and dried for 24 hours to remove the solvent, resulting in an electrolyte membrane with a thickness of approximately 50μm.

[0136] Comparative Example 8 The experimental steps are basically the same as in Example 1, the only difference being the preparation of the electrolyte membrane.

[0137] Preparation of electrolyte membranes In an argon-filled glove box, 2g of the polymer solid electrolyte polyvinylidene fluoride (PVDF), 0.2g of the boron-containing additive lithium tetrafluoroborate (LiBF4), and 0.1g of the phosphorus-containing additive lithium difluorobis(oxalato)phosphate (LiDFBOP) were weighed and dissolved in 13mL of anhydrous DMF solvent. At the same time, 1.8g of LiTFSI was added. The mixture was magnetically stirred at 60℃ for 12 hours to form a uniform and transparent electrolyte slurry. The electrolyte slurry was slowly cast onto a clean glass plate and then evenly coated with a scraper. The coated glass plate was then transferred to a vacuum drying oven at 60℃ and dried for 24 hours to remove the solvent, resulting in an electrolyte membrane with a thickness of approximately 50μm.

[0138] Performance testing 1. Solvation structure analysis Raman spectroscopy was used to test the electrolyte membranes of the examples and comparative examples. Figure 3 As shown, in the Raman spectrum of Comparative Example 1 (PFHP), the value located at 739 cm⁻¹ 1 The peak at that location corresponds to free Li + / SSIP structure. Example 1 (PFHP) In the Raman spectrum of OB), the intensity of this peak decreases significantly, while at 744 cm⁻¹... 1 (CIP) and 750 cm 1 A stronger peak appears at (AGG). This indicates that the introduction of LiDFOB transforms the solvation structure of lithium ions from being dominated by free ion / solvent-separated ion pairs to an anion-derived solvation structure dominated by contact ion pairs and ion aggregates, effectively weakening [Li(DMF)]. x ] + structure.

[0139] 2. Ionic conductivity The ionic conductivity of the electrolyte membrane was tested using the AC impedance method at 25℃.

[0140] 3. Cyclic stability The symmetrical cell was subjected to a current density of 0.5 mA·cm⁻¹ 2 A constant current charge-discharge test was performed to obtain the polarization voltage after n hours of cycling.

[0141] At 25℃, a solid-state battery cell is first charged to 4.25V (vs. Li+ / Li) at a current density of 0.5C, allowed to stand for 10 minutes, and then discharged to 2.5V (vs. Li+ / Li) at a current density of 0.5C. The discharge specific capacity at this point is recorded as C1. The solid-state battery cell is then cycled 200 times at a current density of 0.5C; the discharge specific capacity at this point is recorded as C2. The capacity retention rate of the solid-state battery cell after 200 cycles at a current density of 0.5C is calculated as C2 / C1 × 100%.

[0142] 4. High-voltage performance test The high-pressure resistance of the electrolyte membrane was determined by using potentiostatic intermittent titration (PITT).

[0143] 5. Interfacial chemical analysis The cycled Example 1 battery was disassembled, and XPS was used to perform in-depth analysis of the SEI film formed on the negative electrode surface. The results are as follows: Figure 4 As shown, the outer layer of the SEI mainly consists of flexible organoboron compounds, while the inner layer is rich in inorganic components such as BF3 and B2O3. This gradient-distributed bilayer structure, with the outer layer providing flexibility to adapt to volume changes and the inner layer providing high mechanical strength to suppress lithium dendrites, is the fundamental reason for achieving excellent interfacial stability.

[0144] 6. Morphological characteristics As can be seen from the SEM images (Figure 5), the electrolyte membrane prepared in Example 1 has a smoother, denser surface and lower porosity; while the electrolyte membrane in Comparative Example 1 has a rougher surface and more pores. The surface morphology of the lithium metal after cycling also confirms this, indicating that the prepared PVDF-based polymer solid electrolyte effectively inhibits the growth of lithium dendrites and forms a uniform and dense lithium deposition layer.

[0145] Table 1 As can be seen from the table above, the electrolyte membrane in the embodiments of this application has a specific ratio of phosphorus-containing additives and boron-containing additives, which can make the electrolyte membrane have good room temperature ionic conductivity and high voltage resistance, and make the solid-state battery cell have good cycle performance.

[0146] Examples 1-1 to Examples 1-7 The experimental steps are basically the same as in Example 1, except that the preparation of the electrolyte membrane is different, and the mass ratio of boron-containing or phosphorus-containing additives to polymer solid electrolyte is different.

[0147] Table 2 As can be seen from the table above, the different mass ratios of boron-containing or phosphorus-containing additives in the embodiments of this application can make the electrolyte membrane have better room temperature ionic conductivity and high voltage resistance, and make the solid-state battery cell have better cycle performance.

[0148] Examples 2-1 to 2-3 The experimental steps are basically the same as in Example 1, the only difference being the preparation of the electrolyte membrane and the type of boron-containing additive.

[0149] Table 3 As can be seen from the table above, the different types of boron-containing additives in the embodiments of this application can result in different binding energies between anions and lithium ions in the boron-containing additives, which can make the electrolyte membrane have better room temperature ionic conductivity and high voltage resistance, and make the solid-state battery cell have better cycle performance.

[0150] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A solid-state battery cell, comprising a positive electrode, an electrolyte membrane, and a negative electrode, wherein the electrolyte membrane is located between the positive electrode and the negative electrode, characterized in that, The electrolyte membrane comprises a polymer solid electrolyte, a lithium salt, and additives. The additives include phosphorus-containing additives and boron-containing additives. The boron-containing additives include boron anions. The mass ratio of the phosphorus-containing additives to the polymer solid electrolyte is 5:100-20:100, and the mass ratio of the boron-containing additives to the polymer solid electrolyte is 2:

100. 20:

100.

2. The solid-state battery cell according to claim 1, characterized in that, The mass ratio of the phosphorus-containing additive to the polymer solid electrolyte is 5:100-12.5:100; and / or, The mass ratio of the boron-containing additive to the polymer solid electrolyte is 5:100-16:

100.

3. The solid-state battery cell according to claim 1 or 2, characterized in that, The mass ratio of the phosphorus-containing additive to the boron-containing additive is 1:1 to 1:

2.

4. The solid-state battery cell according to claim 1 or 2, characterized in that, The phosphorus-containing additive includes one or more of lithium difluorobis(oxalato)phosphate, lithium difluorophosphate, lithium tri(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, lithium hexafluorophosphate, and lithium difluoro(oxalato)phosphate; and / or, The boron-containing additives include one or more of lithium difluorooxalate borate, lithium dioxalate borate, lithium tetrafluoroborate, lithium oxalate borate, and lithium trifluoroethyl borate.

5. The solid-state battery cell according to claim 1 or 2, characterized in that, The crystallinity of the polymer solid electrolyte is 15%-50%.

6. The solid-state battery cell according to claim 1 or 2, characterized in that, The lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(difluorosulfonyl)imide, lithium perchlorate, and lithium hexafluorophosphate; and / or, The polymer solid electrolyte includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polymethyl methacrylate, polyethylene, polypropylene glycol, polyethylene glycol methyl ether acrylate, and poly(1,3-dioxolane).

7. The solid-state battery cell according to claim 1 or 2, characterized in that, The electrolyte membrane further includes a gel polymer, which contains an organic solvent. The organic solvent includes organophosphorus solvents and non-organophosphorus solvents. The organophosphorus solvent includes one or more of triethyl phosphate, trimethyl phosphate, and tributyl phosphate. The non-organophosphorus solvent includes one or more of N,N-dimethylformamide, N-methylpyrrolidone, acetonitrile, acetone, dimethyl carbonate, ethylene carbonate, diethyl carbonate, and tetrahydrofuran.

8. The solid-state battery cell according to claim 1 or 2, characterized in that, The negative electrode includes a negative current collector and a lithium-based metal layer located on at least one surface of the negative current collector. The lithium-based metal layer includes one or more of metallic lithium and lithium alloys. Optionally, the thickness of the lithium-based metal layer is 1 μm to 50 μm.

9. An electrolyte membrane, characterized in that, The product comprises a polymer solid electrolyte, a lithium salt, and additives, wherein the additives include phosphorus-containing additives and boron-containing additives, the boron-containing additives including boron anions, the mass ratio of the phosphorus-containing additives to the polymer solid electrolyte is 5:100-20:100, and the mass ratio of the boron-containing additives to the polymer solid electrolyte is 2:

100. 16:

100.

10. A method for preparing the electrolyte membrane according to claim 9, characterized in that, The polymer monomer, lithium salt, boron-containing additive, phosphorus-containing additive and initiator are dissolved in an organic solvent and mixed evenly to obtain a precursor solution. The precursor solution is injected into the cavity of the battery cell or coated on the surface of the electrode assembly, and an in-situ polymerization reaction is initiated by heating or ultraviolet light irradiation to form an electrolyte membrane.

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