Sulfur-containing lithium salt solid-state electrolyte, solid-state battery and preparation method therefor, battery device and electric device

Abstract

A sulfur-containing lithium salt solid-state electrolyte, a solid-state battery and a preparation method therefor, a battery device and an electrical device. The solid-state battery comprises a sulfur-containing lithium salt solid-state electrolyte, and the sulfur-containing lithium salt solid-state electrolyte comprises an additive. The additive comprises a cellulose derivative and an organic functional material, wherein the cellulose derivative comprises one or more of an alkyl cellulose, a hydroxyalkyl cellulose, and an alkyl hydroxyalkyl cellulose; and an end group of the organic functional material comprises an oxygen-containing group, and the relative molecular weight of the organic functional material is 50-500. The above technical solution can improve the cycle performance of the solid-state battery.

Description

Sulfur-containing lithium salt solid electrolytes, solid-state batteries and their preparation methods, battery devices and electrical devices

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202510363996.0, filed on March 26, 2025, entitled “Sulfur-containing lithium salt solid electrolyte, solid battery and preparation method thereof, battery device and power-consuming device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to a sulfur-containing lithium salt solid electrolyte, a solid battery and its preparation method, a battery device and an electrical device. Background Technology

[0004] Solid-state batteries have high energy density and high reliability, and are therefore widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools.

[0005] However, the cycle performance and other aspects of solid-state batteries still need further improvement. Summary of the Invention

[0006] This application provides a sulfur-containing lithium salt solid electrolyte, a solid battery and its preparation method, a battery device and an electrical device. The embodiments of this application can improve the cycle performance of solid batteries.

[0007] In a first aspect, this application proposes a solid-state battery, which includes a sulfur-containing lithium salt solid electrolyte, the sulfur-containing lithium salt solid electrolyte including additives, the additives including cellulose derivatives and organic functional materials, the cellulose derivatives including one or more of alkyl cellulose, hydroxyalkyl cellulose and alkylhydroxyalkyl cellulose, the end groups of the organic functional materials including oxygen-containing groups, and the relative molecular weight of the organic functional materials being 50 to 500.

[0008] The organic functional materials in this application have relatively small molecular weights, resulting in smaller molecular volumes. Through the interaction between the oxygen-containing groups of the organic functional materials and the hydroxyl groups of the cellulose derivatives, the interaction between the molecular chains of the cellulose derivatives is weakened. This reduces the rigidity between the molecular chains of the cellulose derivatives and decreases their brittleness, thereby improving flexibility and enhancing the flexibility of the sulfur-containing lithium salt solid electrolyte. This allows the sulfur-containing lithium salt solid electrolyte to change with the volume of the electrode during cyclic charging and discharging, making it less prone to problems such as detachment and cracking, and thus improving the cycle performance of the solid-state battery.

[0009] In some embodiments, the ratio of the mass content of cellulose derivatives to the mass content of organic functional materials is 1.5:8.5 to 8.5:1.5, or can be 5:5 to 8:2, based on the mass content of the sulfur-containing lithium salt solid electrolyte.

[0010] When the ratio of the mass content of cellulose derivatives to the mass content of organic functional materials is within the above range, the sulfur-containing lithium salt solid electrolyte has superior mechanical properties, such as fracture strength and flexibility, such as elongation at break. During the cyclic charging and discharging process of solid-state batteries, the sulfur-containing lithium salt solid electrolyte is not prone to structural damage.

[0011] In some embodiments, the additive content in the sulfur-containing lithium salt solid electrolyte is 1% to 5% by mass. When the additive content is within this range, the sulfur-containing lithium salt solid electrolyte exhibits superior mechanical properties, such as fracture strength and flexibility, and is less prone to structural damage during solid-state battery charge-discharge cycles. Furthermore, the additive content is not excessively high, ensuring that the ionic conductivity of the sulfur-containing lithium salt solid electrolyte remains high, resulting in excellent electrochemical performance.

[0012] In some embodiments, the relative molecular weight of the organic functional material is between 50 and 300. The relatively small molecular weight of the organic functional material results in a small molecular volume, and the organic functional material itself does not significantly increase rigidity. Through the interaction between the organic functional material and the cellulose derivative, the interaction between the cellulose derivative itself is weakened, thereby reducing the rigidity of the cellulose derivative, improving its flexibility, and thus improving the cycle performance of the solid-state battery.

[0013] In some embodiments, the organic functional material includes a compound represented by Formula I.

[0014] In formula I,

[0015] M1 and M2 are terminal groups, and at least one of M1 and M2 includes an oxygen-containing group, which includes a hydroxyl or a carboxyl group.

[0016] R includes R 11 and R 12 Each independently comprises C1 to C4 alkylene groups, R 13 This includes single bonds, ether bonds, or disulfide bonds, with # indicating the connection site between R and the adjacent group.

[0017] The aforementioned materials can interact with cellulose derivatives, reducing the self-interaction of cellulose derivatives and improving the flexibility of cellulose derivatives. This, in turn, enhances the flexibility of sulfur-containing lithium salt solid electrolytes, thereby improving the cycle performance of solid-state batteries.

[0018] In some embodiments, the organic functional material includes one or more compounds from Formula I-1 to Formula I-4.

[0019] The aforementioned materials can interact with cellulose derivatives, reducing the self-interaction of cellulose derivatives and improving the flexibility of cellulose derivatives. This, in turn, enhances the flexibility of sulfur-containing lithium salt solid electrolytes, thereby improving the cycle performance of solid-state batteries.

[0020] In some embodiments, the cellulose derivative satisfies: V is 90 cP to 110 cP; V represents the viscosity of the mixture, which includes the cellulose derivative and a mixed solvent, wherein the cellulose derivative has a mass content of 5% in the mixture, and the mixed solvent includes toluene and isopropanol in a mass ratio of 8:2.

[0021] When cellulose derivatives satisfy the above relationship, they can effectively bind the effective components in sulfur-containing lithium salt solid electrolytes, enabling the sulfur-containing lithium salt solid electrolytes to form a continuous film layer, which is beneficial to improving the electrochemical performance of solid electrolytes.

[0022] In some embodiments, the weight-average molecular weight of the cellulose derivative is 1 × 10⁻⁶. 5 g / mol to 5×10 5 When the weight-average molecular weight of cellulose derivatives is within the above range, it can effectively improve the adhesion of cellulose derivatives, enabling the sulfur-containing lithium salt solid electrolyte to form a continuous film layer, which is beneficial to improving the electrochemical performance of the solid electrolyte.

[0023] In some embodiments, alkyl cellulose includes one or more of ethyl cellulose, propyl cellulose, and butyl cellulose. The aforementioned material can interact with cellulose derivatives, reducing the self-interactions of the cellulose derivatives and improving their flexibility, thereby enhancing the flexibility of the sulfur-containing lithium salt solid electrolyte and thus improving the cycle performance of the solid-state battery.

[0024] In some embodiments, hydroxyalkyl cellulose includes one or more of hydroxypropyl cellulose and hydroxybutyl cellulose. The aforementioned material can interact with cellulose derivatives, reducing the self-interactions of the cellulose derivatives and improving their flexibility, thereby enhancing the flexibility of the sulfur-containing lithium salt solid electrolyte and thus improving the cycle performance of the solid-state battery.

[0025] In some embodiments, alkyl hydroxyalkyl cellulose includes one or more of ethyl hydroxyethyl cellulose, methyl hydroxyethyl cellulose, and methyl hydroxypropyl cellulose. The above-mentioned material can interact with cellulose derivatives, reducing the self-interactions of the cellulose derivatives and improving the flexibility of the cellulose derivatives, thereby enhancing the flexibility of the sulfur-containing lithium salt solid electrolyte and thus improving the cycle performance of the solid-state battery.

[0026] In some embodiments, the additives satisfy: E is 6% to 50%; E represents the elongation at break of the organic film layer, the mixture is dried to prepare an organic film layer with a thickness of 0.1 mm, wherein the mixture includes cellulose derivatives and mixed solvents, the cellulose derivatives have a mass content of 5% in the mixture, and the mixed solvents include toluene and isopropanol in a mass ratio of 8:2.

[0027] The organic film layer prepared by the additive in this embodiment has a high elongation at break, which makes the sulfur-containing lithium salt solid electrolyte have excellent flexibility and is not easy to break when the additive is located in the sulfur-containing lithium salt solid electrolyte. During the cycle charge and discharge of the solid battery, the sulfur-containing lithium salt solid electrolyte can undergo adaptive deformation when subjected to the squeezing action of adjacent electrodes, which can reduce the risk of cracking and breakage of the sulfur-containing lithium salt solid electrolyte.

[0028] In some embodiments, the additive satisfies the following condition: B is 0.3 MPa to 32 MPa;

[0029] B represents the tensile strength of the organic film layer. The organic film layer is prepared by drying the mixture. The thickness of the organic film layer is 0.1 mm. The mixture includes cellulose derivatives and mixed solvents. The mass content of the cellulose derivatives in the mixture is 5%. The mixed solvents include toluene and isopropanol in a mass ratio of 8:2.

[0030] When the fracture strength of the organic film layer is within the above range, the sulfur-containing lithium salt solid electrolyte has high mechanical strength. During the cycle charge and discharge of the solid battery, the sulfur-containing lithium salt solid electrolyte is not prone to cracks or breakage even under the pressure of adjacent electrodes.

[0031] In some embodiments, the ionic conductivity of the sulfur-containing lithium salt solid electrolyte is between 1.8 mS / cm and 2.7 mS / cm. When the ionic conductivity of the sulfur-containing lithium salt solid electrolyte is within the above range, the ionic conductivity is relatively high, which is beneficial for the diffusion of lithium ions in the sulfur-containing lithium salt solid electrolyte, reduces the interfacial impedance between the sulfur-containing lithium salt solid electrolyte and the negative electrode, and improves the cycle performance of the solid-state battery.

[0032] In some embodiments, the sulfur-containing lithium salt solid electrolyte includes Li2S-P2S5, Li2S-GeS2, Li2S-SiS2, Li6PS5X, and Li7P3S. 11 The lithium salt contains one or more of the following: Li3PS4, Li4SnS4, wherein X includes at least one of Cl, Br, and I. Cellulose derivatives and sulfur-containing lithium salts have a certain bonding effect. Cellulose derivatives facilitate the uniform dispersion of sulfur-containing lithium salts, resulting in a uniform distribution of sulfur-containing lithium salts in the solid electrolyte. This promotes the uniform diffusion of lithium ions in the solid electrolyte, thereby improving the electrochemical performance of the solid electrolyte.

[0033] In some embodiments, the solid-state battery includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes cellulose derivatives and organic functional materials. The cellulose derivatives include one or more of alkyl cellulose, hydroxyalkyl cellulose, and alkylhydroxyalkyl cellulose. The end groups of the organic functional materials include oxygen-containing groups, and the relative molecular weight of the organic functional materials is 50 to 500.

[0034] The above-mentioned additives have excellent flexibility, which can improve the flexibility of the positive electrode film, making the positive electrode film less prone to cracking and peeling, and improving the cycle performance of solid-state batteries.

[0035] In some embodiments, the solid-state battery also includes a negative electrode, which includes a negative current collector.

[0036] Secondly, this application proposes a method for preparing a solid-state battery. The method includes adding cellulose derivatives, organic functional materials, and sulfur-containing lithium salts to an organic solvent to form an electrolyte slurry. The cellulose derivatives include one or more of alkyl cellulose, hydroxyalkyl cellulose, and alkylhydroxyalkyl cellulose. The end groups of the organic functional materials include oxygen-containing groups, and the relative molecular weight of the organic functional materials is 50 to 500. The electrolyte slurry is then processed into a sulfur-containing lithium salt solid electrolyte using a film-forming process. A positive electrode, a sulfur-containing lithium salt solid electrolyte, and a negative electrode are assembled into an electrode assembly. The electrode assembly is then assembled into a casing to prepare a solid-state battery.

[0037] Thirdly, this application proposes a sulfur-containing lithium salt solid electrolyte, which includes additives, including cellulose derivatives and organic functional materials. The cellulose derivatives include one or more of alkyl cellulose, hydroxyalkyl cellulose and alkylhydroxyalkyl cellulose. The end groups of the organic functional materials include oxygen-containing groups, and the relative molecular weight of the organic functional materials is 50 to 500.

[0038] Fourthly, embodiments of this application also propose a battery device, which includes a solid-state battery according to any embodiment of the first aspect of this application, a solid-state battery prepared by any method according to any embodiment of the second aspect of this application, or a sulfur-containing lithium salt solid electrolyte as described in any embodiment of the third aspect of this application.

[0039] Fifthly, embodiments of this application also propose an electrical device, including a battery device as described in any embodiment of the fourth aspect of this application. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0041] Figure 1 is a structural schematic diagram of a vehicle provided in some embodiments of this application.

[0042] Figure 2 is an exploded schematic diagram of a battery pack provided in some embodiments of this application.

[0043] Figure 3 is a schematic diagram of the battery module shown in Figure 2.

[0044] Figure 4 is a schematic diagram of the structure of a solid-state battery provided in some embodiments of this application.

[0045] Figure 5 is a schematic diagram of the structure of the electrode assembly of a solid-state battery provided in some embodiments of this application.

[0046] The accompanying drawings may not be drawn to scale.

[0047] The reference numerals in the attached drawings are explained as follows: 1. Vehicle; 2. Battery pack; 3. Controller; 4. Motor; 5. Housing; 5a. First housing section; 5b. Second housing section; 5c. Retaining space; 6. Battery module; 7. Solid-state battery; 10. Electrode assembly; 11. Positive electrode; 12. Negative electrode; 13. Sulfide solid electrolyte; 20. Casing. Detailed Implementation

[0048] The embodiments of this application are hereby disclosed in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0049] 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.

[0050] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0051] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0052] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means 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.

[0053] Solid-state batteries include solid-state electrolytes, which are electrolyte materials or substances that exist in a solid form throughout the storage and fabrication of solid-state batteries and their components, as well as during operation. This includes, but is not limited to, solid-state electrolytes existing in a solid form at room temperature.

[0054] For example, solid electrolytes include one or more of sulfur-containing lithium salt solid electrolytes, oxide solid electrolytes, halide solid electrolytes, and polymer solid electrolytes. Sulfur-containing lithium salt solid electrolytes are widely used due to their superior ionic conductivity and low density.

[0055] However, in related technologies, sulfur-containing lithium salt solid electrolytes may experience problems such as detachment, cracking, or even breakage during cyclic charging and discharging, resulting in poor cycle performance of solid-state batteries. The reason for this may be that the binder of the sulfur-containing lithium salt solid electrolyte is too rigid and lacks flexibility, making the overall rigidity of the solid electrolyte too high. During cyclic charging and discharging, when the internal volume of the solid-state battery expands, it may cause compressive stress on the sulfur-containing lithium salt solid electrolyte, leading to detachment, cracking, and other issues.

[0056] This application proposes a solid-state battery in which additives are incorporated into a sulfur-containing lithium salt solid electrolyte. The additives include cellulose derivatives and organic functional materials. The cellulose derivatives act as binders and dispersers, resulting in a more uniform distribution of the effective components in the sulfur-containing lithium salt solid electrolyte and superior electrochemical performance. The additives also include organic functional materials. The relatively small molecular weight of the organic functional materials results in a smaller molecular volume. Through the interaction between the oxygen-containing groups of the organic functional materials and the cellulose derivatives, the rigidity between the molecular chains of the cellulose derivatives can be reduced, improving flexibility and enhancing the flexibility of the sulfur-containing lithium salt solid electrolyte. This makes the sulfur-containing lithium salt solid electrolyte less prone to problems such as shedding and cracking during cyclic charging and discharging, thereby improving the cycle performance of the solid-state battery.

[0057] The solid-state batteries described in this application are applicable to battery devices and electrical devices that use battery devices.

[0058] Electrical devices can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of this application do not impose special limitations on the above-mentioned electrical devices.

[0059] For ease of explanation, the following implementation method uses a vehicle as an example of an electrical device.

[0060] Figure 1 is a structural schematic diagram of vehicle 1 provided in some embodiments of this application.

[0061] As shown in Figure 1, a battery device is installed inside the vehicle 1. The battery device can be located at the bottom, front, or rear of the vehicle 1. The battery device can be used to power the vehicle 1; for example, the battery device can serve as the operating power source for the vehicle 1.

[0062] Vehicle 1 may also include controller 3 and motor 4. Controller 3 is used to control the battery device to supply power to motor 4, for example, for the power needs of vehicle 1 during starting, navigation and driving.

[0063] In some embodiments of this application, the battery device can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0064] The battery apparatus mentioned in the embodiments of this application may include one or more solid-state battery assemblies for providing voltage and capacity. A solid-state battery assembly may include multiple solid-state cells, which are connected in series, parallel, or mixed connections via a busbar.

[0065] In some embodiments, a solid-state battery assembly is typically formed by arranging multiple solid-state batteries.

[0066] As an example, a solid-state battery assembly can be a battery module, which consists of multiple solid-state batteries arranged and fixed together to form a single module. As another example, a battery module can be formed by bundling multiple solid-state batteries together with cable ties.

[0067] In some embodiments, the battery device may be a battery pack 2, which includes a housing and one or more solid-state battery components housed within the housing.

[0068] As an example, a solid-state battery assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0069] As an example, solid-state battery assemblies can also be housed in a housing by directly fixing multiple solid-state batteries to the housing.

[0070] Figure 2 is an exploded view of a battery pack 2 provided in some embodiments of this application. As shown in Figure 2, the battery pack 2 includes a housing 5 and a solid-state battery (not shown in Figure 2), with the solid-state battery housed within the housing 5.

[0071] The housing 5 is used to house the solid-state battery, and the housing 5 can have various structures. In some embodiments, the housing 5 may include a first housing portion 5a and a second housing portion 5b, which overlap each other, and together define a housing space 5c for housing the solid-state battery. The second housing portion 5b may be a hollow structure with one end open, and the first housing portion 5a may be a plate-like structure, with the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c; alternatively, both the first housing portion 5a and the second housing portion 5b may be hollow structures with one side open, with the open side of the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as cylinders, cuboids, etc.

[0072] To improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 5a and the second housing part 5b.

[0073] Assuming that the first box section 5a covers the top of the second box section 5b, the first box section 5a can also be called the upper box cover, and the second box section 5b can also be called the lower box.

[0074] Figure 3 is a schematic diagram of the structure of the battery module 6 shown in Figure 2.

[0075] In some embodiments, as shown in Figure 3, there are multiple solid-state batteries 7. These batteries are first connected in series, parallel, or in a mixed configuration to form a battery module 6. The multiple battery modules 6 are then connected in series, parallel, or in a mixed configuration to form a whole, which is housed within a casing.

[0076] Multiple solid-state batteries 7 in battery module 6 can be electrically connected through busbars to achieve parallel, series, or mixed connection of the multiple solid-state batteries 7 in battery module 6. There can be one or more busbars, and each busbar is used to electrically connect at least two solid-state batteries 7.

[0077] Figure 4 is a schematic diagram of the structure of a solid-state battery 7 provided in some embodiments of this application; Figure 5 is a schematic diagram of the structure of the electrode assembly 10 of a solid-state battery 7 provided in some embodiments of this application.

[0078] As shown in Figures 4 and 5, in some embodiments, the solid-state battery 7 includes an electrode assembly 10 and a housing 20, with the electrode assembly 10 housed within the housing 20.

[0079] The internal cavity formed by the outer casing 20 can be used to accommodate the electrode assembly 10, the electrolyte, and other components. The outer casing 20 can be of various shapes, such as a cylinder or a cuboid. The shape of the outer casing 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 has a cylindrical structure, the outer casing 20 can be a cylindrical structure. If the electrode assembly 10 has a cuboid structure, the outer casing 20 can be a cuboid structure.

[0080] The outer shell 20 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc. This application does not impose any special restrictions on this.

[0081] The electrode assembly 10 housed within the housing 20 may be one or more. In this embodiment, the electrode assembly 10 may be a wound structure or a stacked structure, and may be a stacked structure.

[0082] The electrode assembly 10 includes a negative electrode 12 and a positive electrode 11, as well as a sulfide solid electrolyte layer 13. During the charging and discharging process of the solid-state battery 7, active ions (e.g., lithium ions) are inserted and extracted back and forth between the positive electrode 11 and the negative electrode 12.

[0083] Positive electrode sheet

[0084] In some embodiments, the positive electrode may include a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0085] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0086] As an example, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, titanium, silver-surfaced aluminum, or stainless steel can be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0087] As an example, the positive electrode active material may include one or more of the following materials: phosphates, layered transition metal oxides, and their respective modified compounds; optionally, the positive electrode active material may include layered transition metal oxides and their respective modified compounds, which is beneficial for improving the energy density of solid-state batteries. However, this application is not limited to these materials, and other conventional materials that can be used as the positive electrode film layer of a battery may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0088] Examples of phosphates may include, but are not limited to, one or more of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0089] Layered transition metal oxides include those with the general formula Li a Ni b Co c M d O e A f One or more of the compounds and their modified compounds. 0.8≤a≤1.2, 0.3≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M includes one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes one or more of N, F, S and Cl.

[0090] Examples of layered transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides (lithium nickel manganese oxide), and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.80 Co 0.15 Al 0.05 One or more of O2 and its modified compounds.

[0091] In the embodiments of this application, the modified compounds of the above-mentioned positive electrode active materials can be doped and / or surface coated to modify the positive electrode active materials, such as carbon coating modification, fast ion conductor coating modification, etc.

[0092] During the charging and discharging process of solid-state batteries, active ions such as Li undergo insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. After charge-discharge cycles, the molar Li content may change when the positive electrode active material is applied to the battery system.

[0093] In the embodiments of this application, the molar content of oxygen (O) in the positive electrode active materials is only a theoretical value. Oxygen release from the crystal lattice will cause the molar content of oxygen (O) to change. In reality, the molar content of oxygen (O) will fluctuate.

[0094] In some embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the positive electrode, a positive electrode film layer may or may not be provided on the surface of the foamed metal. As an example, lithium source material, potassium metal, or sodium metal may also be filled and / or deposited within the foamed metal, where the lithium source material is lithium metal and / or a lithium-rich material.

[0095] In some embodiments, the positive electrode film layer may optionally include a positive electrode conductive agent. This application does not impose particular limitations on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent in the positive electrode film layer is ≤5 wt%.

[0096] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose particular limitations on the type of positive electrode binder. As an example, the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. In some embodiments, the mass percentage of the positive electrode binder in the positive electrode film layer is ≤5 wt%.

[0097] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0098] Negative electrode sheet

[0099] In some embodiments, the solid-state battery is an ion-type battery such as a lithium-ion battery or a metal-type battery such as a lithium metal battery, with lithium metal batteries being an option.

[0100] In some implementations, the negative electrode may include a negative current collector.

[0101] As an example, the negative electrode current collector may include a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it may be aluminum or stainless steel with a silver surface treatment, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0102] Optionally, the negative electrode current collector may further include a lithium metal layer, for example, the lithium metal layer is disposed on at least one side of the negative electrode current collector. Optionally, the lithium metal layer may include lithium metal or a lithium alloy, for example, the lithium alloy may include lithium element and alloying elements, the alloying elements may include indium element, etc., and the mass ratio of lithium element and alloying element is 1:9 to 9:1.

[0103] Optionally, the negative electrode sheet may further include a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material.

[0104] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0105] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in solid-state batteries. As an example, the negative electrode active material may include one or more of the following materials: carbon materials (e.g., carbon materials include one or more of artificial graphite, natural graphite, soft carbon, and hard carbon), silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode films in batteries may also be used. These negative electrode films may be used alone or in combination of two or more.

[0106] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose particular limitations on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon fibers. In some embodiments, the mass percentage of the negative electrode conductive agent in the negative electrode film layer is ≤5 wt%.

[0107] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose particular limitations on the type of negative electrode binder. As an example, the negative electrode binder may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage of the negative electrode binder in the negative electrode film layer is ≤5 wt%.

[0108] In some embodiments, the negative electrode film layer may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass percentage of other additives in the negative electrode film layer is ≤2 wt%.

[0109] Sulfur-containing lithium salt solid electrolyte

[0110] In some embodiments, the solid-state battery also includes a sulfur-containing lithium salt solid electrolyte. The sulfur-containing lithium salt solid electrolyte is located between the positive and negative electrode plates. During the charging and discharging process of the solid-state battery, active ions are inserted and extracted back and forth between the positive and negative electrode plates. The sulfur-containing lithium salt solid electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0111] Sulfur-containing lithium salt solid electrolytes can be disposed on the positive electrode in the form of a film layer, or on the negative electrode in the form of a film layer, or located between the positive and negative electrode layers as an independent film layer.

[0112] In some embodiments, the sulfur-containing lithium salt solid electrolyte includes additives, which include cellulose derivatives and organic functional materials. The end groups of the organic functional materials include oxygen-containing groups, and the relative molecular weight of the organic functional materials is 50 to 500.

[0113] Cellulose derivatives can be understood as cellulose in which some hydrogen atoms of the hydroxyl group are replaced by alkyl groups. This results in cellulose derivatives including not only hydroxyl groups but also one or more alkyl and hydroxyalkyl groups, giving them an amphiphilic structure. The hydroxyl group and other structures can form bonds with sulfur-containing lithium salts in sulfur-containing lithium solid electrolytes, enhancing adhesion and promoting uniform dispersion of the sulfur-containing lithium salts. The alkyl and hydroxyalkyl groups can increase the nonpolarity of cellulose derivatives or decrease their polarity, which is beneficial for uniform dispersion of cellulose derivatives in sulfur-containing lithium solid electrolytes and improves the electrochemical performance of the sulfur-containing lithium solid electrolytes.

[0114] However, the hydroxyl groups of cellulose derivatives may enable strong van der Waals forces or hydrogen bonds to form between the molecular chains of cellulose derivatives. Moreover, cellulose derivatives have a certain hydrophobic effect, which makes them more rigid and prone to cracking in sulfur-containing lithium salt solid electrolytes.

[0115] The additives in this application also include organic functional materials. The molecular weight of organic functional materials is relatively small, resulting in a smaller molecular volume. Through the interaction between the oxygen-containing groups of organic functional materials and the hydroxyl groups of cellulose derivatives, the interaction between the molecular chains of cellulose derivatives is weakened, which can reduce the rigidity between the molecular chains of cellulose derivatives and reduce their brittleness, thereby improving flexibility and enhancing the flexibility of sulfur-containing lithium salt solid electrolytes. This allows the sulfur-containing lithium salt solid electrolytes to change with the volume change of the electrode during cyclic charging and discharging, making them less prone to problems such as detachment and cracking, and thus improving the cycle performance of solid-state batteries.

[0116] Cellulose derivatives have a relatively stable structure and are not prone to side reactions with other substances in sulfur-containing lithium salt solid electrolytes. Under the operating voltage of solid-state batteries, sulfur-containing lithium salt solid electrolytes can stably exert their electrochemical performance, so that the capacity of solid-state batteries will not decay rapidly, which is beneficial to improving the cycle performance of solid-state batteries.

[0117] In some embodiments, the ratio of the mass content of cellulose derivatives to the mass content of organic functional materials is 1.5:8.5 to 8.5:1.5, and optionally 5:5 to 8:2, based on the mass content of the sulfur-containing lithium salt solid electrolyte.

[0118] For example, the ratio of the mass content of cellulose derivatives to the mass content of organic functional materials is 1.5:8.5, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 1.5:8.5 or any range of two of the above values.

[0119] The higher the mass content of cellulose derivatives, the higher the rigidity and brittleness of the additive, and the higher the fracture strength of the sulfur-containing lithium salt solid electrolyte; the higher the mass content of organic functional materials, the higher the flexibility of the additive; in other words, as the mass content of organic functional materials increases, the fracture strength of the additive decreases and the elongation at break increases.

[0120] When the ratio of the mass content of cellulose derivatives to the mass content of organic functional materials is within the above range, the sulfur-containing lithium salt solid electrolyte has superior mechanical properties, such as fracture strength and flexibility, such as elongation at break. During the cyclic charging and discharging process of solid-state batteries, the sulfur-containing lithium salt solid electrolyte is not prone to structural damage.

[0121] In some embodiments, the additive is present in a mass content of 1% to 5% in the sulfur-containing lithium salt solid electrolyte, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any combination of two of the above values.

[0122] When the mass content of the additive is within the above-mentioned range, the sulfur-containing lithium salt solid electrolyte exhibits superior mechanical properties, such as fracture strength and flexibility. During the cyclic charge-discharge process of solid-state batteries, the sulfur-containing lithium salt solid electrolyte is less prone to structural damage. Furthermore, the mass content of the additive is not excessively high, ensuring that the ionic conductivity of the sulfur-containing lithium salt solid electrolyte remains high, resulting in excellent electrochemical performance.

[0123] In the embodiments of this application, the mass content of cellulose derivatives and organic functional materials has a meaning known in the art. A sulfur-containing lithium salt solid electrolyte is taken as a sample and weighed. The sulfur-containing lithium salt solid electrolyte is dispersed in an organic solvent (e.g., toluene and isopropanol in a mass ratio of 8:2). Cellulose derivatives and organic functional additives are dissolved in the organic solvent. The sulfur-containing lithium salt is separated by means of filtration, centrifugation, etc. Utilizing the difference in solubility between cellulose derivatives and organic functional materials, the cellulose derivatives and organic functional materials are separated by means of extraction, recrystallization, etc. The mass of each organic solvent can be obtained by drying the solvent and weighing it. The percentage of the mass of this component relative to the sulfur-containing lithium salt solid electrolyte is the mass content of that component.

[0124] [Organic Functional Materials]

[0125] In the embodiments of this application, the relative molecular weight of the organic functional material is 50 to 500, and can be selected as 50 to 300. For example, the relative molecular weight of the organic functional material is 50, 100, 150, 200, 250, 300, 350, 400, 450, 500 or any range of two of the above values.

[0126] Organic functional materials have relatively small molecular weights, resulting in smaller molecular volumes. As a result, organic functional materials themselves do not significantly increase rigidity. However, through the interaction between organic functional materials and cellulose derivatives, the interaction between the cellulose derivatives themselves is weakened, thereby reducing the rigidity of the cellulose derivatives and improving their flexibility.

[0127] In some embodiments, the organic functional material includes a compound represented by Formula I.

[0128] In formula I,

[0129] M1 and M2 each independently represent an end group, and at least one of M1 and M2 includes an oxygen-containing group;

[0130] R includes R 11 and R 12 Each independently comprises C1 to C4 alkylene groups, R 13 This includes single bonds, ether bonds, or disulfide bonds, with # indicating the connection site between R and the adjacent group.

[0131] Both M1 and M2 are end groups of organic functional materials. M1 and M2 are in the same compound structure and can contain the same or different groups. When M1 and M2 contain the same group, they can both include oxygen-containing groups. When M1 and M2 contain different groups, they can both include different oxygen-containing groups, or one of M1 and M2 may contain an oxygen-containing group while the other contains other groups.

[0132] Optionally, the oxygen-containing group includes a hydroxyl or a carboxyl group, preferably a hydroxyl group. These groups can interact with cellulose derivatives, reducing the self-interactions of the cellulose derivatives and improving their flexibility, thereby enhancing the flexibility of the sulfur-containing lithium salt solid electrolyte. Furthermore, there are virtually no side reactions between these groups and the sulfur-containing lithium salt, further improving the electrochemical performance of the sulfur-containing lithium salt solid electrolyte.

[0133] For example, organic functional materials include one or more compounds from Formula I-1 to Formula I-4.

[0134] Hydroxyethyl disulfide

[0135] Optionally, the organic functional material includes one or more of the compounds shown in Formula I-1 to Formula I-3.

[0136] [Cellulose derivatives]

[0137] In some embodiments, the cellulose derivative satisfies the following condition: V is 90 cP to 110 cP, for example, 90 cP, 91 cP, 92 cP, 93 cP, 94 cP, 95 cP, 96 cP, 97 cP, 98 cP, 99 cP, 100 cP, 101 cP, 102 cP, 103 cP, 104 cP, 105 cP, 106 cP, 107 cP, 108 cP, 109 cP, 110 cP, or a range consisting of any two of the above values.

[0138] V represents the viscosity of the mixture, which includes cellulose derivatives and a mixed solvent. The cellulose derivatives account for 5% of the mass of the mixture, and the mixed solvent includes toluene and isopropanol in a mass ratio of 8:2.

[0139] Specifically, toluene and isopropanol in a mass ratio of 8:2 are mixed as a mixed solvent, and cellulose derivatives are dissolved in the mixed solvent to obtain a mixed solution, wherein the mass content of cellulose derivatives in the mixed solution is 5%.

[0140] When cellulose derivatives satisfy the above relationship, they can effectively bind the effective components in sulfur-containing lithium salt solid electrolytes, enabling the sulfur-containing lithium salt solid electrolytes to form a continuous film layer, which is beneficial to improving the electrochemical performance of solid electrolytes.

[0141] In the embodiments of this application, viscosity has a meaning known in the art and can be tested using equipment and methods known in the art, such as according to standard GB / T 22235-2008.

[0142] In some embodiments, the weight-average molecular weight of the cellulose derivative is 1 × 10⁻⁶. 5 g / mol to 5×10 5 g / mol.

[0143] For example, the weight-average molecular weight of the cellulose derivative is 1 × 10⁻⁶. 5 g / mol, 1.5×10 5 g / mol, 2×10 5 g / mol, 2.5×10 5 g / mol, 3×10 5 g / mol, 3.5×10 5 g / mol, 4×10 5 g / mol, 4.5×10 5 g / mol, 5×10 5 g / mol or a range consisting of any two of the above values.

[0144] When the weight-average molecular weight of cellulose derivatives is within the above range, the adhesiveness of cellulose derivatives can be effectively improved, enabling the sulfur-containing lithium salt solid electrolyte to form a continuous film layer, which is beneficial to improving the electrochemical performance of the solid electrolyte.

[0145] In the embodiments of this application, the cellulose derivatives include one or more of alkyl cellulose, hydroxyalkyl cellulose, and alkylhydroxyalkyl cellulose.

[0146] In some embodiments, alkyl cellulose includes C1 to C10 alkyl cellulose, which refers to alkyl cellulose derived from cellulose with C1 to C10 alkyl substitution, wherein the hydrogen atom of the hydroxyl group of the cellulose is substituted with C1 to C10 alkyl, and the substitution may be complete or partial.

[0147] Optionally, the alkyl cellulose includes C1 alkyl cellulose, C2 alkyl cellulose, C3 alkyl cellulose, C4 alkyl cellulose, C5 alkyl cellulose, C6 alkyl cellulose, C7 alkyl cellulose, C8 alkyl cellulose, C9 alkyl cellulose, C10 alkyl cellulose, or any combination of two of the above values. The alkyl groups in the alkyl cellulose facilitate the uniform dispersion of alkyl cellulose in the sulfur-containing lithium salt solid electrolyte, thereby promoting the uniform dispersion of the sulfur-containing lithium salt. In the preparation of the sulfur-containing lithium salt solid electrolyte, the organic solvent can be selected as a non-polar or low-polar solvent with high solubility for alkyl groups, allowing the alkyl cellulose to be uniformly dispersed in the organic solvent, thus facilitating the preparation of a sulfur-containing lithium salt solid electrolyte with uniform performance.

[0148] For example, alkyl cellulose includes one or more of ethyl cellulose, propyl cellulose, and butyl cellulose.

[0149] In some embodiments, hydroxyalkyl cellulose includes C1 to C10 hydroxyalkyl cellulose, which refers to hydroxyalkyl cellulose derived from cellulose that has been substituted with C1 to C10 hydroxyalkyl groups, wherein the hydrogen atoms of the hydroxyl groups of the cellulose are substituted with C1 to C10 hydroxyalkyl groups, and the substitution may be complete or partial.

[0150] Optionally, the hydroxyalkyl cellulose includes C1 hydroxyalkyl cellulose, C2 hydroxyalkyl cellulose, C3 hydroxyalkyl cellulose, C4 hydroxyalkyl cellulose, C5 hydroxyalkyl cellulose, C6 hydroxyalkyl cellulose, C7 hydroxyalkyl cellulose, C8 hydroxyalkyl cellulose, C9 hydroxyalkyl cellulose, C10 hydroxyalkyl cellulose, or any combination of two of the above values. The hydroxyalkyl groups in the hydroxyalkyl cellulose facilitate the uniform dispersion of hydroxyalkyl cellulose in the sulfur-containing lithium salt solid electrolyte, thereby promoting the uniform dispersion of the sulfur-containing lithium salt. In the preparation of the sulfur-containing lithium salt solid electrolyte, the organic solvent can be selected as a non-polar or low-polar solvent with high solubility for the hydroxyalkyl groups, allowing the hydroxyalkyl cellulose to be uniformly dispersed in the organic solvent, thus facilitating the preparation of a sulfur-containing lithium salt solid electrolyte with uniform performance.

[0151] For example, hydroxyalkyl cellulose includes one or more of hydroxypropyl cellulose and hydroxybutyl cellulose.

[0152] In some embodiments, alkyl hydroxyalkyl cellulose is derived from cellulose substituted with C1 to C10 alkyl or C1 to C10 hydroxyalkyl, wherein the hydrogen atom of the hydroxyl group of the cellulose is substituted with C1 to C10 alkyl or C1 to C10 hydroxyalkyl, and the substitution may be complete or partial.

[0153] For example, alkyl hydroxyalkyl cellulose includes one or more of ethyl hydroxyethyl cellulose, methyl hydroxyethyl cellulose, and methyl hydroxypropyl cellulose.

[0154] In the embodiments of this application, the weight-average molecular weight of cellulose derivatives can be tested using methods such as gel permeation chromatography (CPC) or mass spectrometry.

[0155] In some embodiments, the additive satisfies the following condition: E is 6% to 50%, for example, 6%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any combination of two of the above values. Optionally, E is 10% to 35%.

[0156] E represents the elongation at break of the organic film. The organic film is prepared by adding additives to a mixed solvent and then drying it. The thickness of the organic film is 0.1 mm. The mixed solvent includes toluene and isopropanol in a mass ratio of 8:2. Optionally, drying can be performed in a vacuum oven at 110°C for 12 hours.

[0157] Specifically, toluene and isopropanol in a mass ratio of 8:2 are mixed as a mixed solvent, and cellulose derivatives are dissolved in the mixed solvent to obtain a mixed solution, wherein the mass content of cellulose derivatives in the mixed solution is 5%; then the mixed solution is dried and the mixed solvent is removed to prepare an organic film layer.

[0158] Elongation at break measures the maximum deformation a film layer can withstand during stretching. The organic film layer prepared by the additive in this application has a high elongation at break, which means that when the additive is located in the sulfur-containing lithium salt solid electrolyte, the sulfur-containing lithium salt solid electrolyte has excellent flexibility and is not prone to breakage. During the cyclic charging and discharging of the solid battery, the sulfur-containing lithium salt solid electrolyte can undergo adaptive deformation when subjected to the squeezing action of adjacent electrodes, which can reduce the risk of cracking and breakage of the sulfur-containing lithium salt solid electrolyte.

[0159] In some embodiments, the additive satisfies the following condition: B is from 0.3 MPa to 32 MPa, for example, 0.3 MPa, 5 MPa, 10 MPa, 15 MPa, 20 MPa, 25 MPa, 30 MPa, 32 MPa, or a range of any two of the above values. Optionally, B is from 5 MPa to 25 MPa.

[0160] B represents the tensile strength of the organic film layer, which is prepared by adding additives to a mixed solvent and then drying. The thickness of the organic film layer is 0.1 mm. Optionally, drying can be performed in a vacuum oven at 110°C for 12 hours.

[0161] The tensile strength of an organic film can measure the maximum stress that the film can withstand during stretching, characterize the ultimate load-bearing capacity of the material under external force, and reflect the strength of the organic film. When the tensile strength of the organic film is within the above-mentioned range, and the additive is located in a sulfur-containing lithium salt solid electrolyte, the sulfur-containing lithium salt solid electrolyte has high mechanical strength. During the cyclic charging and discharging process of a solid-state battery, the sulfur-containing lithium salt solid electrolyte is not prone to cracking or breakage even under the pressure of adjacent electrodes.

[0162] After the additive is prepared into an organic film, the elongation at break and the tensile strength of the organic film are tested to reflect the mechanical strength of the additive after film formation, and to infer the performance of the sulfur-containing lithium salt solid electrolyte formed after the additive is added to the electrolyte slurry.

[0163] In the embodiments of this application, the elongation at break and tensile strength of the membrane are known in the art and can be tested using equipment and methods known in the art. Specifically, the test can be performed in accordance with the standard GB / T 13022-91.

[0164] [Sulfur-containing lithium salts]

[0165] In this application embodiment, the sulfur-containing lithium salt solid electrolyte includes sulfur-containing lithium salts. Optionally, the sulfur-containing lithium salts include Li2S-P2S5, Li2S-GeS2, Li2S-SiS2, Li6PS5X, and Li7P3S. 11 One or more of Li3PS4 and Li4SnS4, wherein X includes at least one of Cl, Br, and I, and may be Cl.

[0166] Cellulose derivatives and sulfur-containing lithium salts have a certain bonding effect. Cellulose derivatives are conducive to the uniform dispersion of sulfur-containing lithium salts, so that the sulfur-containing lithium salts are evenly distributed in the solid electrolyte, which is conducive to the uniform diffusion of lithium ions in the solid electrolyte and thus improves the electrochemical performance of the solid electrolyte.

[0167] In some embodiments, the ionic conductivity of the sulfur-containing lithium salt solid electrolyte is from 1.8 mS / cm to 2.7 mS / cm, for example, 1.8 mS / cm, 1.9 mS / cm, 2.0 mS / cm, 2.1 mS / cm, 2.2 mS / cm, 2.3 mS / cm, 2.4 mS / cm, 2.5 mS / cm, 2.6 mS / cm, 2.7 mS / cm, or any combination of two of the above values.

[0168] When the ionic conductivity of the sulfur-containing lithium salt solid electrolyte is within the above range, the ionic conductivity of the sulfur-containing lithium salt solid electrolyte is relatively high, which is conducive to the diffusion of lithium ions in the sulfur-containing lithium salt solid electrolyte, reduces the interfacial impedance between the sulfur-containing lithium salt solid electrolyte and the negative electrode, and improves the cycle performance of the solid battery.

[0169] In the embodiments of this application, the ionic conductivity of the sulfur-containing lithium salt solid electrolyte has a well-known meaning in the art and can be tested using well-known equipment and methods in the art. For example, the ohmic impedance of the sulfur-containing lithium salt solid electrolyte can be measured using a Chenhua electrochemical workstation at a test temperature of 25°C, a frequency range of 1Hz-1MHz, and a perturbation signal of 5mV. The ionic conductivity can be calculated based on the impedance, thickness, and area of ​​the sulfur-containing lithium salt solid electrolyte.

[0170] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer including the additives of the above embodiments.

[0171] The additives have excellent adhesion, which can effectively bond the positive electrode active material, as well as the positive electrode active material and the positive electrode current collector, so that the positive electrode film is continuous and the positive electrode film is not easy to peel off from the positive electrode current collector. Moreover, the additives have excellent flexibility, which can improve the flexibility of the positive electrode film, making the positive electrode film less prone to cracking and peeling, and improving the cycle performance of solid-state batteries.

[0172] In the process of preparing the positive electrode film, the components of the positive electrode film are added to the solvent in advance to prepare the positive electrode slurry. The introduction of additives makes the positive electrode slurry viscous and fluid, and has excellent stability, making it less prone to sedimentation.

[0173] In some embodiments, the additive content in the positive electrode film layer is 1% to 5% by mass, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any combination of two of the above values.

[0174] When the mass content of the additive is within the above range, it can effectively improve the flexibility of the positive electrode film, making the positive electrode film less prone to cracking and peeling, and improving the cycle performance of solid-state batteries.

[0175] In some embodiments, the positive electrode film may also include a sulfur-containing lithium salt. The types of sulfur-containing lithium salts have been described above and will not be repeated here. The sulfur-containing lithium salt in the positive electrode film can provide an ion conduction path inside the positive electrode film, reduce interfacial impedance, optimize ion transport inside the positive electrode film, and further improve the cycle performance of the solid-state battery.

[0176] The selection of the materials and mass ratios of the additives in the positive electrode film layer has been described above and will not be repeated here.

[0177] This application also provides a method for preparing a sulfur-containing lithium salt solid electrolyte, the method comprising:

[0178] Cellulose derivatives, organic functional materials, and sulfur-containing lithium salts are added to an organic solvent to form an electrolyte slurry;

[0179] The electrolyte slurry is processed into a sulfur-containing lithium salt solid electrolyte through a film-forming process.

[0180] In some embodiments, the organic solvent includes one or more of tetrahydrofuran, acetonitrile, pyridine, alcohols, carboxylic acid esters, alkanes, ethers, and benzenes.

[0181] For example, alcohols include one or more of methanol, ethanol, propanol, isopropanol, and butanol.

[0182] For example, carboxylic acid esters include one or more of propyl propionate, butyl propionate, and butyl butyrate.

[0183] For example, alkanes include one or more of octane, nonane, decane, undecane, and dodecane.

[0184] For example, ethers include one or more of anisole, dibutyl ether, diethyl ether, tributylmethyl ethyl ether, isopropyl ether, and tetraethylene glycol dimethyl ether.

[0185] For example, benzene compounds include one or more of toluene, p-xylene, and pseudotrimethylbenzene.

[0186] The aforementioned organic solvents have relatively weak polarity, making them less prone to side reactions with sulfur-containing lithium salts, thus ensuring the stability of the performance of the sulfur-containing lithium salts. Cellulose derivatives have high solubility in the aforementioned organic solvents, which is beneficial for the uniform dispersion of cellulose derivatives in organic solvents. Due to the bonding between cellulose derivatives and sulfur-containing lithium salts, cellulose derivatives can drive the uniform dispersion of sulfur-containing lithium salts in organic solvents, resulting in uniform performance and excellent electrochemical performance of the formed sulfur-containing lithium salt solid electrolyte film.

[0187] During the preparation of electrolyte slurry films, cellulose derivatives have excellent flexibility and processing performance, resulting in low drying stress. This makes it less likely for the electrolyte slurry to crack during film formation, thus giving the formed sulfur-containing lithium salt solid electrolyte film a certain degree of flexibility.

[0188] In this embodiment of the application, the film-forming process may optionally include drying.

[0189] In some implementations, the drying process is carried out in a vacuum environment with a vacuum degree of less than -90 kPa, and the drying temperature is 100°C to 120°C; optionally, the drying time is 8 hours to 15 hours.

[0190] This application also provides a method for preparing a solid-state battery, the method comprising:

[0191] Cellulose derivatives, organic functional materials, and sulfur-containing lithium salts are added to a mixed solvent to form an electrolyte slurry;

[0192] The electrolyte slurry is processed into a sulfur-containing lithium salt solid electrolyte through a film-forming process.

[0193] A positive electrode, a sulfur-containing lithium salt solid electrolyte, and a negative electrode are assembled into an electrode assembly.

[0194] The electrode assembly is assembled into the casing to prepare a solid-state battery.

[0195] In the embodiments of this application, the materials of the positive electrode and the electrolyte can be selected according to the content described above, and will not be repeated here.

[0196] Example

[0197] The following embodiments describe the contents disclosed in 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 the embodiments 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.

[0198] Example 1

[0199] (1) Preparation of the positive electrode sheet:

[0200] The positive electrode active material lithium nickel manganese oxide, the conductive agent acetylene black, and the binder PVDF are mixed in a mass ratio of 97:2:3. The solvent N-methylpyrrolidone (NMP) is added and stirred until the system is homogeneous to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated on both sides of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying to obtain the positive electrode sheet.

[0201] (2) Preparation of negative electrode sheet:

[0202] The negative electrode includes a negative current collector, which uses copper foil as the negative current collector, and lithium-indium alloy layers are rolled on both sides of the negative current collector, wherein the mass ratio of lithium metal to indium metal is 3:7.

[0203] (3) Preparation of sulfur-containing lithium salt solid electrolytes:

[0204] Li6PS5Cl sulfur-containing lithium salt and additives were mixed at a mass ratio of 98:2, and toluene solvent was added to prepare an electrolyte slurry (solid content 50%). The mixture was then thoroughly mixed using a degassing machine.

[0205] The mixed slurry was evenly coated onto aluminum foil using a coating machine and then dried in a vacuum oven at 110°C for 12 hours to obtain a solid electrolyte.

[0206] (4) Solid-state battery assembly:

[0207] A solid-state battery is formed by matching positive and negative electrode plates, using a solid electrolyte to isolate the positive and negative electrodes, and wrapping them in an aluminum-plastic film shell.

[0208] Examples 2-1 to 2-4

[0209] Solid-state batteries were prepared using a method similar to that of Example 1, except that the mass ratio of cellulose derivatives and organic functional materials was adjusted.

[0210] Example 3

[0211] Solid-state batteries were prepared using a method similar to that of Example 1, except that the total mass content of cellulose derivatives and organic functional materials was adjusted.

[0212] Examples 4-1 to 4-4

[0213] Solid-state batteries were prepared using a method similar to that of Example 1, except that the material of the cellulose derivative was adjusted.

[0214] Examples 5-1 and 5-2

[0215] Solid-state batteries were prepared using a method similar to that of Example 1, except that the material composition of the organic functional materials was adjusted.

[0216] Example 6

[0217] Solid-state batteries were prepared using a method similar to that of Example 1, except that the material of the sulfur-containing lithium salt was adjusted to Li6PS5Br.

[0218] Comparative Example 1

[0219] Solid-state batteries were prepared using a method similar to that of Example 1, except that the preparation of the sulfur-containing lithium salt solid electrolyte was adjusted:

[0220] Li6PS5Cl sulfur-containing lithium salt and ethyl cellulose were mixed at a mass ratio of 98:2, and toluene solvent was added to prepare an electrolyte slurry (solid content 50%). The mixture was then thoroughly mixed using a degassing machine.

[0221] The mixed slurry was evenly coated onto aluminum foil using a coating machine, and then dried in a vacuum oven at 110°C for 12 hours. After removing the aluminum foil, a solid electrolyte was obtained.

[0222] Test section

[0223] 1. Cycle life of solid-state batteries

[0224] Cyclic performance test: At 25°C, the solid-state battery was charged at a constant current of 0.33C to a voltage of 4.2V, and then discharged at a constant current of 0.33C until the final voltage was 2.8V. The discharge capacity of the first cycle was recorded.

[0225] Then, perform the charging and discharging cycles as described above. When the cycle reaches 800 cycles, stop charging and discharging. The ratio of the discharge capacity at this point to the discharge capacity of the first cycle is the battery's cycle capacity retention rate.

[0226] Excellent cycle performance: 500 or more cycles;

[0227] Good cycle performance: the number of cycles is greater than or equal to 300 cycles and less than 500 cycles;

[0228] Moderate cycle performance: the number of cycles is greater than or equal to 200 and less than 300;

[0229] Poor cycle performance: fewer than 200 cycles.

[0230] Test Results

[0231] Table 1

[0232] The weight-average molecular weight of ethyl cellulose in Comparative Example 1 and Example 1 was 2 × 10⁻⁶. 5 g / mol.

[0233] The adhesion was tested using the electrolyte slurry formulation of Comparative Example 1. The electrolyte slurry of Example 1 was placed on aluminum foil and dried in a vacuum oven at 110°C for 12 hours. After 1 hour, it rapidly detached.

[0234] The adhesion was tested using the electrolyte slurry formulation of Example 1. The electrolyte slurry of Example 1 was placed on copper foil and dried in a vacuum oven at 110°C for 12 hours. After 1 hour, the structure was stable and not prone to delamination.

[0235] Compared to Comparative Example 1, the sulfide solid electrolyte of this application embodiment has higher viscosity and is less prone to delamination after being assembled into a solid-state battery.

[0236] The mass ratio of cellulose derivatives to organic functional materials can affect the elongation at break of organic membranes. For example, the higher elongation at break in Examples 1, 2-2, 2-3, and 2-4 indicates that increasing the content of organic functional materials significantly improves the flexibility of organic membranes, thereby improving the flexibility of sulfide solid electrolytes.

[0237] The trend of fracture strength is opposite to that of elongation at break. When the content of organic functional materials is low, such as in Example 2-1, the fracture strength is high; however, when the content of organic functional materials increases, the fracture strength decreases significantly, such as in Example 2-3. This indicates that while increasing the content of organic functional materials can improve flexibility, it may weaken the mechanical strength of the material.

[0238] The mass ratio of cellulose derivatives to organic functional materials in the embodiments of this application is within an appropriate range, which can improve the flexibility of sulfide solid electrolytes, and the sulfide solid electrolytes have high mechanical strength, thus improving the cycle performance of solid batteries.

[0239] In Example 3, the total mass content of cellulose derivatives and organic functional materials has a slight effect on ionic conductivity, but the overall effect is small, resulting in excellent ionic conductivity of the sulfide solid electrolyte.

[0240] Examples 4-1 to 4-4 show that cellulose derivatives of different materials can effectively improve the flexibility of sulfide solid electrolytes and improve the cycle performance of solid batteries.

[0241] Examples 5-1 and 5-2 show that organic functional materials of different materials can effectively improve the flexibility of sulfide solid electrolytes and improve the cycle performance of solid batteries.

[0242] This application is applicable to a variety of sulfide solid electrolytes, such as the sulfur-containing lithium salt, which can be Li6PS5Cl of Example 1 or Li6PS5Br of Example 6.

[0243] Example 7

[0244] Solid-state batteries were prepared using a method similar to that of Example 1, except that the preparation of the positive electrode was adjusted:

[0245] The positive electrode active material lithium nickel manganese oxide, wet-milled Li6PS5Cl sulfur-containing lithium salt, conductive agent carbon black and additives are mixed in a mass ratio of 80:15:3:2, toluene is added and stirred until the system is homogeneous (solid content is 50%) to obtain the positive electrode slurry.

[0246] The positive electrode slurry is evenly coated on both sides of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying to form the positive electrode sheet.

[0247] Example 8

[0248] Solid-state batteries were prepared using a method similar to that of Example 1, except that the total mass content of cellulose derivatives and organic functional materials in the positive electrode film was adjusted.

[0249] The test results are shown in Table 2.

[0250] Table 2

[0251] The introduction of additives can improve the flexibility of the positive electrode film, and the positive electrode film has excellent ion conduction ability, which improves the cycle performance of solid-state batteries.

[0252] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A solid-state battery comprising a sulfur-containing lithium salt solid electrolyte, wherein the sulfur-containing lithium salt solid electrolyte comprises an additive, the additive comprising a cellulose derivative and an organic functional material, wherein the cellulose derivative comprises one or more of alkyl cellulose, hydroxyalkyl cellulose and alkylhydroxyalkyl cellulose, wherein the end group of the organic functional material comprises an oxygen-containing group, and the relative molecular weight of the organic functional material is 50 to 500.

2. The solid-state battery according to claim 1, wherein, Based on the mass content of the sulfur-containing lithium salt solid electrolyte, the ratio of the mass content of the cellulose derivative to the mass content of the organic functional material is from 1.5:8.5 to 8.5:1.

5.

3. The solid-state battery according to claim 1 or 2, wherein, Based on the mass content of the sulfur-containing lithium salt solid electrolyte, the ratio of the mass content of the cellulose derivative to the mass content of the organic functional material is 5:5 to 8:

2.

4. The solid-state battery according to any one of claims 1 to 3, wherein, The additive is present in a mass content of 1% to 5% in the sulfur-containing lithium salt solid electrolyte.

5. The solid-state battery according to any one of claims 1 to 4, wherein, The relative molecular weight of the organic functional material is 50 to 300.

6. The solid-state battery according to any one of claims 1 to 5, wherein, The organic functional materials include compounds represented by Formula I. In Formula I, M1 and M2 are the terminal groups, and at least one of M1 and M2 includes an oxygen-containing group, which includes a hydroxyl or a carboxyl group; R includes R 11 and R 12 Each independently comprises C1 to C4 alkylene groups, R 13 This includes single bonds, ether bonds, or disulfide bonds, with # indicating the connection site between R and the adjacent group.

7. The solid-state battery according to any one of claims 1 to 6, wherein, The organic functional materials include one or more compounds from Formula I-1 to Formula I-4.

8. The solid-state battery according to any one of claims 1 to 7, wherein, The cellulose derivatives satisfy the following condition: V is 90 cP to 110 cP; V represents the viscosity of the mixture, which includes the cellulose derivative and a mixed solvent. The cellulose derivative has a mass content of 5% in the mixture, and the mixed solvent includes toluene and isopropanol in a mass ratio of 8:

2.

9. The solid-state battery according to any one of claims 1 to 8, wherein, The weight-average molecular weight of the cellulose derivative is 1×10⁻⁶. 5 g / mol to 5×10 5 g / mol.

10. The solid-state battery according to any one of claims 1 to 9, wherein, The alkyl cellulose includes one or more of ethyl cellulose, propyl cellulose, and butyl cellulose; and / or The hydroxyalkyl cellulose includes one or more of hydroxypropyl cellulose and hydroxybutyl cellulose; and / or The alkyl hydroxyalkyl cellulose includes one or more of ethyl hydroxyethyl cellulose, methyl hydroxyethyl cellulose, and methyl hydroxypropyl cellulose.

11. The solid-state battery according to any one of claims 1 to 10, wherein, The additives satisfy the following condition: E is 6% to 50%; E represents the elongation at break of the organic film layer. The organic film layer is prepared by drying the mixture. The thickness of the organic film layer is 0.1 mm. The mixture includes the cellulose derivative and a mixed solvent. The cellulose derivative has a mass content of 5% in the mixture. The mixed solvent includes toluene and isopropanol in a mass ratio of 8:

2. and / or The additive satisfies the following condition: B is 0.3 MPa to 32 MPa; B represents the tensile strength of the organic film layer. The organic film layer is prepared by drying the mixture. The thickness of the organic film layer is 0.1 mm. The mixture includes the cellulose derivative and a mixed solvent. The cellulose derivative has a mass content of 5% in the mixture. The mixed solvent includes toluene and isopropanol in a mass ratio of 8:

2.

12. The solid-state battery according to any one of claims 1 to 11, wherein, The sulfur-containing lithium salt solid electrolyte has an ionic conductivity of 1.8 mS / cm to 2.7 mS / cm.

13. The solid-state battery according to any one of claims 1 to 12, wherein, The sulfur-containing lithium salt solid electrolyte includes Li2S-P2S5, Li2S-GeS2, Li2S-SiS2, Li6PS5X, and Li7P3S. 11 One or more of Li3PS4 and Li4SnS4, wherein X includes at least one of Cl, Br, and I.

14. The solid-state battery according to any one of claims 1 to 13, comprising a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer comprising a cellulose derivative and an organic functional material, the cellulose derivative comprising one or more of alkyl cellulose, hydroxyalkyl cellulose and alkylhydroxyalkyl cellulose, the end group of the organic functional material comprising an oxygen-containing group, and the relative molecular weight of the organic functional material being 50 to 500.

15. The solid-state battery according to any one of claims 1 to 14, further comprising a negative electrode sheet, said negative electrode sheet comprising a negative current collector.

16. A method for preparing a solid-state battery, comprising: Cellulose derivatives, organic functional materials, and sulfur-containing lithium salts are added to an organic solvent to form an electrolyte slurry. The cellulose derivatives include one or more of alkyl cellulose, hydroxyalkyl cellulose, and alkylhydroxyalkyl cellulose. The end groups of the organic functional materials include oxygen-containing groups. The relative molecular weight of the organic functional materials is 50 to 500. The electrolyte slurry is processed into a sulfur-containing lithium salt solid electrolyte through a film-forming process. The positive electrode, the sulfur-containing lithium salt solid electrolyte, and the negative electrode are assembled into an electrode assembly. The electrode assembly is assembled into a housing to prepare a solid-state battery.

17. A sulfur-containing lithium salt solid electrolyte, comprising an additive, the additive comprising a cellulose derivative and an organic functional material, the cellulose derivative comprising one or more of alkyl cellulose, hydroxyalkyl cellulose and alkylhydroxyalkyl cellulose, the organic functional material having an end group comprising an oxygen-containing group, and the organic functional material having a relative molecular weight of 50 to 500.

18. A battery device comprising a solid-state battery as described in any one of claims 1 to 15, a solid-state battery prepared by the preparation method of claim 16, or a sulfur-containing lithium salt solid electrolyte as described in claim 17.

19. An electrical device comprising the battery device as described in claim 18.

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