Solid-state electrolyte prepolymer, solid-state electrolyte, and battery

Abstract

The application discloses a solid electrolyte prepolymer solution, a solid electrolyte and a battery. The solid electrolyte prepolymer solution comprises monomers and an electrolyte, the electrolyte comprises a lithium salt, an organic solvent and an additive, and the monomers comprise one or more of compounds with a structural formula shown in formula (I): wherein m is any integer from 2 to 8. The solid electrolyte prepared by using the solid electrolyte prepolymer solution disclosed by the application can be used in a battery, and can effectively improve the heat resistance and safety performance of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more particularly to a solid electrolyte prepolymer, a solid electrolyte, and a battery. Background Technology

[0002] Currently, electrolytes commonly used in electrochemical devices such as batteries include liquid electrolytes and solid electrolytes. Among them, liquid electrolytes have a low thermal decomposition temperature, are flammable, and easily volatilize when heated to form toxic gases, which limits the improvement of battery safety performance and energy density.

[0003] Solid-state electrolytes (SSEs) are solid ionic conductor electrolytes that offer high safety, high power density, and cyclicability due to their non-leaking of toxic organic liquids, low flammability, non-volatility, strong mechanical properties, good thermal stability, ease of processing, and low self-discharge rate.

[0004] However, existing solid electrolytes and their solid batteries have poor heat resistance and need further improvement. Summary of the Invention

[0005] In view of this, this application provides a solid electrolyte prepolymer, a solid electrolyte, and a battery, aiming to improve the problem of poor heat resistance of solid electrolytes prepared from existing solid electrolyte prepolymers.

[0006] In a first aspect, embodiments of this application provide a solid electrolyte prepolymer, comprising a monomer and an electrolyte, wherein the electrolyte comprises a lithium salt, an organic solvent, and an additive, and the monomer comprises one or more compounds having the structural formula shown in formula (I):

[0007]

[0008] Where m is any integer from 2 to 8;

[0009] L is a linking group, selected from single bonds, substituted or unsubstituted -(CH2). n1 -, substituted or unsubstituted -(CH2) n2 CH=CH(CH2) n3 -, substituted or unsubstituted -(CH2) n4 C≡C(CH2) n5 -, substituted or unsubstituted -(CH2) n6 -O-(CH2) n7 -, substituted or unsubstituted -(CH2) n8 CO(CH2) n9 - Substituted or unsubstituted amino groups, substituted or unsubstituted C3-C4 groups 30One or more of cycloalkyl, aryl with 6 to 60 substituted or unsubstituted cyclic atoms, and heteroaryl with 6 to 60 substituted or unsubstituted cyclic atoms, wherein n1 to n9 are each independently selected from integers from 1 to 5;

[0010] R1, R2, and R3 are each independently selected from hydrogen, substituted or unsubstituted C1 to C3. 30 Alkyl, substituted or unsubstituted C3-C 30 One or more of the following: cycloalkyl, substituted or unsubstituted aryl groups having a ring atom number of 6 to 60.

[0011] Optionally, in some embodiments, at least one of the following features (1) to (2) is also included:

[0012] (1) The L is selected from single bond, substituted or unsubstituted -(CH2). n1 -, substituted or unsubstituted -(CH2) n2 CH=CH(CH2) n3 -, substituted or unsubstituted -(CH2) n4 C≡C(CH2) n5 -, substituted or unsubstituted -(CH2) n6 -O-(CH2) n7 -, substituted or unsubstituted -(CH2) n8 CO(CH2) n9 - Substituted or unsubstituted amino groups, substituted or unsubstituted C3-C4 groups 20 One or more of cycloalkyl, aryl with 6 to 30 substituted or unsubstituted cyclic atoms, and heteroaryl with 6 to 30 substituted or unsubstituted cyclic atoms, wherein n1 to n9 are each independently selected from integers from 1 to 5;

[0013] (2) R1, R2, and R3 are each independently selected from hydrogen, substituted or unsubstituted C1-C1 atoms. 20 Alkyl, substituted or unsubstituted C3-C 20 One or more of the following: cycloalkyl, substituted or unsubstituted aryl groups having a ring atom number of 6 to 30.

[0014] Optionally, in some embodiments, at least one of the following features (1) to (2) is also included:

[0015] (1) The L is selected from single bond, substituted or unsubstituted -(CH2). n1 -, substituted or unsubstituted -(CH2) n2 CH=CH(CH2) n3 -, substituted or unsubstituted -(CH2) n4 C≡C(CH2) n5-, substituted or unsubstituted -(CH2) n6 -O-(CH2) n7 -, substituted or unsubstituted -(CH2) n8 CO(CH2) n9 - Substituted or unsubstituted amino groups, substituted or unsubstituted C3-C4 groups 10 One or more of cycloalkyl, substituted or unsubstituted aryl groups having 6 to 15 ring atoms, and substituted or unsubstituted heteroaryl groups having 6 to 15 ring atoms, wherein n1 to n9 are each independently selected from integers from 1 to 5;

[0016] (2) R1, R2, and R3 are each independently selected from hydrogen, substituted or unsubstituted C1-C1 atoms. 10 Alkyl, substituted or unsubstituted C3-C 10 One or more of cycloalkyl, substituted or unsubstituted aryl groups having a ring atom number of 6 to 20.

[0017] Optionally, in some embodiments, at least one of the following features (1) to (2) is also included:

[0018] (1) The L is selected from single bond, substituted or unsubstituted -(CH2). n1 -, substituted or unsubstituted -(CH2) n6 -O-(CH2) n7 - One or more combinations of substituted or unsubstituted amino groups, substituted or unsubstituted cycloalkyl groups, and substituted or unsubstituted aryl groups, wherein n1, n6, and n7 are each independently selected from integers from 1 to 5;

[0019] (2) R1, R2, and R3 are each independently selected from one or more combinations of hydrogen, substituted or unsubstituted C1-C8 alkyl, substituted or unsubstituted C3-C8 cycloalkyl, and substituted or unsubstituted aryl with 6 to 10 ring atoms.

[0020] Optionally, in some embodiments, L is selected from one or more of the following groups:

[0021] -(CH2) n1 -、-(CH2) n6 -O-(CH2) n7 -、

[0022]

[0023] Among them, L1 to L 19 As linking groups, each is independently selected from single bonds and -(CH2). m’- any one of the following, where m' is selected from any integer from 1 to 5.

[0024] Optionally, in some embodiments, the monomer is also selected from one or more compounds represented by the following structural formulas:

[0025]

[0026] Optionally, in some embodiments, at least one of the following features (1) to (7) is also included:

[0027] (1) m is any integer from 2 to 4;

[0028] (2) The lithium salt includes one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium bistrifluoromethylsulfonylimide, lithium tetrafluoroborate, lithium bis(oxalate)borate, and lithium difluorooxalateborate.

[0029] (3) The organic solvent includes one or more of carbonate organic solvents and carboxylic acid ester organic solvents, wherein the carbonate organic solvent includes one or more of methyl ethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, and fluoroethylene carbonate, and the carboxylic acid ester organic solvent includes one or more of fluoroethylene carbonate, ethyl propionate, and propyl propionate.

[0030] (4) The additives are selected from nitrile additives and ester additives. The nitrile additives include one or more of adiponitrile, glutaronitrile, succinic anhydride, and ethylene glycol bis(propionitrile) ether. The ester additives include one or more of vinyl sulfate, propanesulfonic acid lactone, citrate anhydride, and triphenyl phosphite.

[0031] (5) In the solid electrolyte prepolymer solution, the content of the monomer is 1-15 wt%, and the content of the electrolyte is 85-99 wt%.

[0032] (6) In the electrolyte, the content of the lithium salt is 10-30 wt%, the content of the additive is 1-10 wt%, and the content of the organic solvent is 60-80 wt%.

[0033] (7) The viscosity range of the solid electrolyte prepolymer is 4 to 20 cP.

[0034] Secondly, embodiments of this application also provide a solid electrolyte, which is obtained by curing the above-mentioned solid electrolyte prepolymer liquid.

[0035] Optionally, in some embodiments, the solid electrolyte satisfies the following relationship:

[0036] B×50<(T+P)×W×A <B×250;

[0037] Where A is the peel strength, B is the viscosity of the solid electrolyte prepolymer, T is the thermal decomposition temperature of the solid electrolyte, P is the exothermic peak temperature of the solid electrolyte, and W is the mass percentage of the monomer in the solid electrolyte prepolymer.

[0038] Optionally, the value of A ranges from 20 to 200 mN / mm;

[0039] Optionally, the value of B ranges from 4 to 20 cP;

[0040] Optionally, the value of T ranges from 100 to 350°C;

[0041] Optionally, the value of P ranges from 100 to 400°C;

[0042] Optionally, the value of W ranges from 1 to 15%.

[0043] Thirdly, embodiments of this application also provide a battery, including a positive electrode, a negative electrode, and the solid electrolyte.

[0044] Optionally, in some embodiments, at least one of the following features (1) to (2) is also included:

[0045] (1) A first polymer layer is bonded to the surface of the positive electrode sheet, and the first polymer layer is located between the positive electrode sheet and the solid electrolyte;

[0046] (2) The surface of the negative electrode sheet has a second polymer layer, which is located between the negative electrode sheet and the solid electrolyte.

[0047] Optionally, in some embodiments, at least one of the following features (1) to (3) is also included:

[0048] (1) The first polymer layer is formed by polymerization of monomers in the solid electrolytic prepolymer solution;

[0049] (2) The second polymer layer is formed by polymerization of monomers in the solid electrolytic prepolymer solution;

[0050] (3) The thickness of the first polymer layer and the second polymer layer are each independently 5-200 nm.

[0051] The solid electrolyte prepared from the solid electrolyte prepolymer liquid described in this application can be used in batteries to effectively improve the battery's heat resistance and safety performance. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a schematic diagram of the structure of a battery provided in an embodiment of this application;

[0054] Figure 2 This is a flowchart of a battery manufacturing method provided in an embodiment of this application;

[0055] Figure 3 This is a SEM image of the positive electrode sheet stripped from the battery in Embodiment 1 of this application;

[0056] Figure 4 This is a SEM image of the positive electrode sheet stripped from the battery in Comparative Example 4 of this application;

[0057] Figure 5 This is a SEM image of the negative electrode sheet stripped from the battery in Embodiment 1 of this application;

[0058] Figure 6 This is a SEM image of the negative electrode sheet stripped from the battery in Comparative Example 4 of this application;

[0059] Figure 7 This is a path-load diagram of the peel strength of the battery in Embodiment 1 of this application;

[0060] Figure 8 This is a DTG curve of the solid electrolyte of Example 1 of this application;

[0061] Figure 9 This is the differential scanning calorimetry (DSC) curve of the solid electrolyte in Example 1 of this application.

[0062] Figure label:

[0063] Battery 100; positive electrode 10; negative electrode 20; separator 30; solid electrolyte 40; first polymer layer 50; second polymer layer 60. Detailed Implementation

[0064] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0066] In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operating state, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish a numerical order.

[0067] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0068] In this application, "at least one" means one or more, and "more than one" means two or more. "One or more", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0069] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0070] Currently, the electrolytes used in lithium-ion batteries are mainly organic liquid electrolytes (organic electrolytes). Due to their low thermal decomposition temperature, flammability, and tendency to volatilize and form toxic gases when heated, there are certain limitations to improving the safety performance and energy density of power batteries.

[0071] Liquid batteries mainly consist of a positive electrode, a negative electrode, an electrolyte, a separator, and external connections and packaging components. In conventional liquid batteries, the electrolyte is composed of solvents, lithium salts, additives, and other chemical substances. Due to its poor thermal stability, it is prone to decomposition reactions or even combustion when heated, leading to significant safety hazards in the battery and other electrochemical systems. Internal and external factors such as battery overload during charging and discharging, external short circuits, high external temperatures, or internal short circuits can all cause the battery to heat up or generate heat, operating under high-temperature conditions. High temperatures can cause the separator to melt, the electrolyte to volatilize or even burn, and damage the internal battery structure. A series of irreversible exothermic chemical reactions can occur between the positive and negative electrode materials, the electrolyte, and the foil, triggering a thermal runaway chain reaction. The high heat generated within a limited space and time can lead to fires and explosions, posing a public safety hazard. Furthermore, when a liquid lithium-ion battery experiences thermal runaway at high temperatures, the solid electrolyte interphase (SEI) film, lithium intercalation compounds, and electrolyte on the active material undergo irreversible thermal decomposition. A large amount of heat and flammable gases are released, causing the internal pressure of the battery to rise and gradually exceed the limit of the explosion-proof valve. When the explosion-proof valve opens, flammable fumes and powder particles are ejected. When these flammable gases and powders come into contact with oxygen in the environment, the flammable fumes are ignited, producing bright sparks or entering a fire state.

[0072] To overcome these shortcomings of liquid lithium-ion batteries, researchers have begun exploring the use of solid-state electrolytes as alternatives. Solid-state electrolytes are broadly classified into two categories: inorganic solid-state electrolytes and polymer solid-state electrolytes (organic solid-state electrolytes). Among them, polymer solid-state electrolytes have attracted widespread attention due to their excellent processing performance and high adaptability to battery shapes.

[0073] Compared to liquid electrolytes, the gelation of organic solid electrolytes can solve leakage problems and provides better mechanical strength and flexibility. Furthermore, organic solid electrolytes utilize intrinsically non-flammable polymer electrolytes, which are less volatile and have a higher decomposition temperature than liquid electrolytes. Their mechanical and electrochemical properties are relatively stable, their flame-retardant effect is more durable, and they can maintain good electrochemical performance at high temperatures. However, the heat resistance of existing organic solid electrolytes is not yet high enough and needs further improvement.

[0074] The technical solution of this application is as follows:

[0075] In a first aspect, embodiments of this application provide a solid electrolyte prepolymer liquid, comprising a monomer and an electrolyte.

[0076] The monomer includes one or more compounds having the structural formula shown in formula (I):

[0077]

[0078] Where m is any integer from 2 to 8;

[0079] L is a linking group, which can be selected from, but is not limited to, single bonds, substituted or unsubstituted -(CH2). n1 -, substituted or unsubstituted -(CH2) n2 CH=CH(CH2) n3 -, substituted or unsubstituted -(CH2) n4 C≡C(CH2) n5 -, substituted or unsubstituted -(CH2) n6 -O-(CH2) n7 -, substituted or unsubstituted -(CH2) n8 CO(CH2) n9 - Substituted or unsubstituted amino groups, substituted or unsubstituted C3-C4 groups 30 One or more of cycloalkyl, aryl with 6 to 60 substituted or unsubstituted cyclic atoms, and heteroaryl with 6 to 60 substituted or unsubstituted cyclic atoms, wherein n1 to n9 are each independently selected from integers from 1 to 5;

[0080] R1, R2, and R3 are each independently selected from, but not limited to, hydrogen, substituted or unsubstituted C1 to C3. 30 Alkyl, substituted or unsubstituted C3-C 30 One or more of the following: cycloalkyl, substituted or unsubstituted aryl groups having a ring atom number of 6 to 60.

[0081] It should be noted that, in this application, the substituents may be selected from, but are not limited to, hydrogen, C1 to C2. 10It is one or more of alkyl groups and aryl groups having a ring number of 6 to 60.

[0082] In at least one preferred embodiment, m is any integer from 2 to 4.

[0083] In some embodiments, the L is selected from single bond, substituted or unsubstituted -(CH2). n1 -, substituted or unsubstituted -(CH2) n2 CH=CH(CH2) n3 -, substituted or unsubstituted -(CH2) n4 C≡C(CH2) n5 -, substituted or unsubstituted -(CH2) n6 -O-(CH2) n7 -, substituted or unsubstituted -(CH2) n8 CO(CH2) n9 - Substituted or unsubstituted amino groups, substituted or unsubstituted C3-C4 groups 20 One or more combinations of cycloalkyl, aryl with 6 to 30 substituted or unsubstituted cyclic atoms, and heteroaryl with 6 to 30 substituted or unsubstituted cyclic atoms, wherein n1 to n9 are each independently selected from integers from 1 to 5.

[0084] Furthermore, in some embodiments, the L is selected from single-bonded, substituted, or unsubstituted -(CH2). n1 -, substituted or unsubstituted -(CH2) n2 CH=CH(CH2) n3 -, substituted or unsubstituted -(CH2) n4 C≡C(CH2) n5 -, substituted or unsubstituted -(CH2) n6 -O-(CH2) n7 -, substituted or unsubstituted -(CH2) n8 CO(CH2) n9 - Substituted or unsubstituted amino groups, substituted or unsubstituted C3-C4 groups 10 One or more combinations of cycloalkyl, substituted or unsubstituted aryl groups having 6 to 15 ring atoms, and substituted or unsubstituted heteroaryl groups having 6 to 15 ring atoms, wherein n1 to n9 are each independently selected from integers from 1 to 5.

[0085] Furthermore, in some embodiments, the L is selected from single-bonded, substituted, or unsubstituted -(CH2). n1 -, substituted or unsubstituted -(CH2) n6 -O-(CH2) n7- One or more combinations of substituted or unsubstituted amino groups, substituted or unsubstituted cycloalkyl groups, and substituted or unsubstituted aryl groups, wherein n1, n6, and n7 are each independently selected from integers from 1 to 5.

[0086] Furthermore, in at least some embodiments, the L is selected from one or more combinations of the following groups:

[0087] -(CH2) n1 -、-(CH2) n6 -O-(CH2) n7 -、

[0088] Among them, L1 to L 19 As linking groups, each is independently selected from, but not limited to, single bonds and -(CH2). m” - any one of the following, where m' is selected from any integer from 1 to 5.

[0089] In some embodiments, R1, R2, and R3 are each independently selected from, but not limited to, hydrogen, substituted or unsubstituted C1 to C3. 20 Alkyl, substituted or unsubstituted C3-C 20 One or more of the following: cycloalkyl, substituted or unsubstituted aryl groups having a ring atom number of 6 to 30.

[0090] Furthermore, in some embodiments, R1, R2, and R3 are each independently selected from, but not limited to, hydrogen, substituted or unsubstituted C1-C1 atoms. 10 Alkyl, substituted or unsubstituted C3-C 10 One or more of cycloalkyl, substituted or unsubstituted aryl groups having a ring atom number of 6 to 20.

[0091] Furthermore, in some embodiments, R1, R2, and R3 are each independently selected from, but not limited to, one or more combinations of hydrogen, substituted or unsubstituted C1-C8 alkyl groups, substituted or unsubstituted C3-C8 cycloalkyl groups, and substituted or unsubstituted aryl groups having 6 to 10 cyclic atoms.

[0092] As an example, in some embodiments, the monomer is selected from one or more compounds represented by the following structural formulas:

[0093]

[0094] When the solid electrolyte prepolymer is heated, the monomers can solidify in situ and cross-link with each other, forming polymer chains through chemical covalent bonds. The polymer chains form a three-dimensional network structure through the cross-linking points, thereby transforming the solid electrolyte prepolymer into a gel-like substance and forming a solid electrolyte.

[0095] The electrolyte comprises lithium salt, organic solvent, and additives. The electrolyte can improve the flexibility and ionic conductivity of solid electrolytes.

[0096] The lithium salt includes, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium tetrafluoroborate (LiBF4), lithium bis(oxalateborate)borate (LiBOB), and lithium di(fluorooxalateborate)borate (LiDFOB). The lithium salt can act as a catalyst and initiator, thereby enabling in-situ solidification of the monomer.

[0097] The organic solvents include, but are not limited to, one or more of carbonate organic solvents and carboxylic acid ester organic solvents.

[0098] In some embodiments, the carbonate organic solvents include, but are not limited to, one or more of methyl ethyl carbonate (ethyl methyl carbonate, EMC), diethyl carbonate (diethyl carbonate, DEC), propylene carbonate (PC), ethylene carbonate, and fluoroethylene carbonate.

[0099] In some embodiments, the carboxylic acid ester organic solvent includes, but is not limited to, one or more of fluoroethylene carbonate (FEC), ethyl propionate (EP), and propyl propionate (PP).

[0100] The additives may be selected from, but are not limited to, nitrile additives and ester additives. The nitrile additives include, but are not limited to, one or more of adiponitrile (AND), glutaronitrile, succinic anhydride (SN), and ethylene glycol bis(propionitrile) ether (DENE). The ester additives include, but are not limited to, one or more of vinyl sulfate (DTD), propanesulfonic acid lactone (PS), citrate anhydride, and triphenyl phosphite (TPP). These additives are functional additives used to form an electrode interface film, improve interface stability, and reduce the impedance of the solid electrolyte prepared from the solid electrolyte prepolymer solution. Triphenyl phosphite can also improve the flame retardant properties of the solid electrolyte prepared from the solid electrolyte prepolymer solution.

[0101] In some embodiments, the monomer content in the solid electrolyte prepolymer is 1–15 wt%, and the electrolyte content is 85–99 wt%. Within these content ranges, it is advantageous to prepare a solid electrolyte with high heat resistance, thereby facilitating the preparation of batteries with good conductivity, high heat resistance, high stability, and high safety.

[0102] As an example, the content of the monomer in the solid electrolyte prepolymer solution can be 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, etc.

[0103] As an example, the content of the electrolyte in the solid electrolyte prepolymer solution can be 85wt%, 86wt%, 87wt%, 88wt%, 89wt%, 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, 98wt%, 99wt%, etc.

[0104] In some embodiments, the electrolyte contains 10–30 wt% lithium salt, 1–10 wt% additives, and 60–80 wt% organic solvents. Within these ranges, it is advantageous to prepare a solid-state electrolyte with high heat resistance, thereby facilitating the preparation of batteries with good conductivity, high heat resistance, high stability, and high safety.

[0105] As an example, the content of lithium salt in the electrolyte can be 10wt%, 12wt%, 13wt%, 15wt%, 16wt%, 18wt%, 20wt%, 22wt%, 25wt%, 26wt%, 28wt%, 30wt%, etc.

[0106] As an example, the content of the additive in the electrolyte can be 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, etc.

[0107] As an example, the content of the organic solvent in the electrolyte can be 60wt%, 62wt%, 63wt%, 65wt%, 66wt%, 68wt%, 70wt%, 73wt%, 75wt%, 78wt%, 80wt%, etc.

[0108] In some embodiments, the viscosity range of the solid electrolyte prepolymer is 4–20 cP, for example, 4 cP, 5 cP, 6 cP, 7 cP, 8 cP, 9 cP, 10 cP, 12 cP, 14 cP, 15 cP, 16 cP, 18 cP, 20 cP, etc. Within this viscosity range, the solid electrolyte prepolymer exhibits good wettability at the positive and negative electrode interfaces, and can uniformly cover the surface interface layer between the electrode and the electrolyte, thereby ensuring that the polymer layer formed after the solid electrolyte prepolymer solidifies uniformly covers the surface interface layer between the electrode and the electrolyte.

[0109] The solid electrolyte prepolymer described in this application exhibits excellent wettability at the positive and negative electrode interfaces, and can uniformly cover the surface layer of the electrode and electrolyte interface. Furthermore, the solid electrolyte prepolymer forms a solid electrolyte after in-situ solidification, which, compared to the lower thermal evaporation temperature of the electrolyte, demonstrates higher thermal stability.

[0110] Battery thermal runaway typically begins with the decomposition and heat release of the SEI film on the negative electrode side. The SEI film mainly consists of an inorganic layer near the electrode and an organic layer away from the electrode. The inorganic layer is relatively stable, while the organic layer is relatively reactive and easily decomposes at high temperatures. When the organic components of the SEI film are exposed to air or high temperatures, they readily decompose and release heat. The battery negative electrode is generally made of graphite or carbon-coated material. The electrolyte solvent components decompose on the negative electrode surface to form the organic components of the SEI film, generating highly reactive products. In the solid electrolyte prepolymer system of this application, the monomer is in a liquid state before in-situ solidification. Due to the presence of multiple epoxy groups, it has low surface tension and a high affinity for the surface of the negative electrode active material particles, promoting the wetting and distribution of monomers on the surface of the negative electrode particles. This facilitates the formation of polymer molecular chains after the monomers are heated and polymerized, forming a uniform interfacial protective layer (polymer layer) on the surface of the negative electrode particles in situ. This polymer layer conducts ions but does not conduct electrons, thus playing a role in conducting ions and isolating the positive and negative electrodes. When a battery is placed at a high temperature, conventional polyolefin separators will thermally shrink, causing the positive and negative electrodes to come into contact and short-circuit internally. The highly active and high-energy positive and negative electrodes will generate local short circuits, causing energy to be released instantaneously in local areas, resulting in thermal runaway of the battery. However, the polymer layer formed by the solid electrolyte prepolymer of this application can cover the surface of the negative electrode and isolate it electronically, which helps to avoid thermal runaway caused by internal short circuits in the battery.

[0111] Furthermore, when the negative electrode of the battery is made of carbon material, functional groups such as hydroxyl or carboxyl groups often form at structural defects in the carbon layer on the negative electrode surface. The epoxy groups of the monomers in the solid electrolyte prepolymer can undergo ring-opening addition reactions to form chemical bonds such as ether or ester bonds, thereby promoting the effective connection between monomer molecules and the negative electrode surface, improving the adhesion of the polymer chain to the electrode interface, and resulting in strong adhesion of the in-situ cured organic solid electrolyte to the electrode. Further, the reaction between the epoxy groups of the monomers in the solid electrolyte prepolymer and the hydroxyl and carboxyl groups at the defects in the negative electrode interface can directionally repair surface defects in the negative electrode particles, forming chemical bonds with higher bond energy at the defects, improving the structural integrity of the defects, thus contributing to the integrity and stability of the SEI film at the negative electrode interface, and consequently contributing to the stability of the surface structure of the negative electrode under heating.

[0112] The positive electrode of a battery is typically a metal oxide or metal salt with a high oxidation potential, especially in the delithiated state. The positive electrode active material particles themselves are unstable, and when in contact with the electrolyte, redox reactions easily occur at the interface, leading to electrolyte decomposition and gas generation, exacerbating thermal runaway at high temperatures. In the solid electrolyte prepolymer system of this application, the monomers have large molecular dipole moments and strong polarity due to the presence of multiple epoxy groups. The organic solvent in the prepolymer is also a polar solvent, while the metal ions on the positive electrode surface have strong polarity. Thus, a good interfacial affinity can be generated between the solid electrolyte prepolymer and the positive electrode, promoting the wetting of the positive electrode interface and interparticle gaps by the prepolymer before solidification. Furthermore, when the monomers polymerize in situ to form polymer chains, the polymer chain molecules have multiple polar groups. Therefore, the solidified electrolyte molecules can form strong complexation interactions with metal ions, fixing them on the surface of the positive electrode particles and forming an effective protective and stabilizing layer. This improves the thermal stability of the positive electrode active material at high temperatures, thereby improving the high-temperature resistance of the lithium battery.

[0113] Furthermore, when the additive is a nitrile additive, it enables strong complexation between electrolyte molecules and the metal centers on the positive electrode surface, suppressing thermal side reactions of the positive electrode material and helping to further improve the thermal stability of the battery. Moreover, the metal ions complexed with cyano groups can act as Lewis acids, catalyzing the ring-opening effect of epoxy monomers. This is equivalent to targeting and catalyzing the ring-opening bonding of the epoxy groups of the monomers at the positive electrode complexation site, forming a robust polymer coating layer.

[0114] The solid electrolyte prepolymer liquid described in this application can undergo a polymerization reaction under the action of an initiator when heated, forming chemical bonds, generating a strong polymer network, and forming a stable and reliable polymer gel. This gel absorbs the electrolyte, effectively preventing its flow and slowing its volatilization, reducing the risk of large-scale electrolyte volatilization and combustion under high-temperature heating, thereby improving the thermal safety of the battery.

[0115] Furthermore, since the electrolyte is a liquid with a fluid state, it cannot form an effective bond on the surface of the active electrode. The composition and concentration of substances at the interface often change, affecting the stable operation of the electrode interface. In the solid electrolyte prepolymer of this application, the epoxy groups of the monomers form ether oxygen bonds after ring opening, resulting in ether oxygen bonds in the main chain of the solidified molecular chain. This endows the polymer molecular chain with flexibility, presenting a compliant and disordered molecular conformation, allowing the molecular groups to extend freely. This facilitates interaction with lithium salts and solvents in the electrolyte, improving the solubility and absorption capacity of the main chain for lithium salts and electrolytes. It further enhances the flexibility of the chain segments, making the polymer chain more mobile and reducing diffusion resistance at the electrode interface. This improves the wetting and adhesion effect of the polymer chain at the electrode interface, which is beneficial for improving the adhesion ability of the polymer chain, allowing the polymer to be firmly fixed on the electrode surface, forming a stable electrode-electrolyte interface, thereby improving interface stability and battery thermal safety.

[0116] Furthermore, the monomers containing multiple epoxy groups in the solid electrolyte prepolymer are thermo-cured in situ to form polymer molecular chains with a cross-linked network structure, constructing a gel system with excellent strength and easy absorption of electrolyte. This effectively solves the leakage caused by electrolyte flow and slows down electrolyte volatilization. At the same time, the polymer cross-linked network has a high thermal decomposition temperature and is difficult to thermally decompose, exhibiting strong high-temperature stability. All of these factors reduce the risk of large-scale electrolyte volatilization and combustion under high-temperature heating, thereby improving battery thermal safety.

[0117] In some embodiments, the preparation method of the solid electrolyte prepolymer includes: mixing monomers and electrolytes in a certain proportion to obtain the solid electrolyte prepolymer.

[0118] Secondly, embodiments of this application also provide a solid electrolyte, which is obtained by curing the solid electrolyte prepolymer liquid described above.

[0119] The solid electrolyte satisfies the following relationship:

[0120] B×50<(T+P)×W×A <B×250;

[0121] Where A is the peel strength, B is the viscosity of the solid electrolyte prepolymer, T is the thermal decomposition temperature of the solid electrolyte, P is the exothermic peak temperature of the solid electrolyte, and W is the mass percentage of the monomer in the solid electrolyte prepolymer.

[0122] The value of A ranges from 20 to 200 mN / mm, for example, 20 mN / mm, 30 mN / mm, 50 mN / mm, 60 mN / mm, 80 mN / mm, 100 mN / mm, 120 mN / mm, 130 mN / mm, 150 mN / mm, 160 mN / mm, 180 mN / mm, 200 mN / mm, etc.

[0123] The value of B ranges from 4 to 20 cP, for example, 4 cP, 5 cP, 6 cP, 7 cP, 8 cP, 9 cP, 10 cP, 12 cP, 14 cP, 15 cP, 16 cP, 18 cP, 20 cP, etc.

[0124] The value of T ranges from 100 to 350℃, for example, 100℃, 120℃, 150℃, 160℃, 180℃, 200℃, 220℃, 230℃, 250℃, 260℃, 280℃, 300℃, 320℃, 330℃, 350℃, etc.

[0125] The value of P ranges from 100 to 400℃, for example, 100℃, 120℃, 150℃, 160℃, 180℃, 200℃, 220℃, 250℃, 260℃, 280℃, 300℃, 320℃, 330℃, 350℃, 360℃, 380℃, 400℃, etc.

[0126] The value of W ranges from 1% to 15%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.

[0127] Solid electrolytes that meet the above numerical relationship requirements can, on the one hand, form good wetting and coverage on the positive and negative electrode surfaces, effectively protect the active interface, and suppress side reactions of the positive and negative electrodes at high temperatures; on the other hand, they have good heat resistance and can withstand high temperatures; and on yet another hand, they have good adhesion, adhering well to the positive and negative electrode surfaces and firmly sticking to the active surface, effectively isolating the positive and negative electrodes to prevent internal short circuits in the battery.

[0128] Thirdly, please refer to Figure 1 This application also provides a battery 100, including a positive electrode 10, a negative electrode 20, a separator 30, and the solid electrolyte 40 described above.

[0129] A first polymer layer 50 is bonded to the surface of the positive electrode 10, and the first polymer layer 50 is located between the positive electrode 10 and the solid electrolyte 40. The first polymer layer 50 is formed by curing monomers in the solid electrolyte prepolymer solution. The first polymer layer 50 has a strong bonding force with the positive electrode 10, which can effectively protect the battery 100 and isolate the positive and negative electrodes of the battery, preventing conduction between the positive and negative electrodes, and effectively improving the thermal stability and safety performance of the battery 100.

[0130] Understandably, the first polymer layer 50 is formed by polymerization of monomers in the solid electrolytic prepolymer solution.

[0131] The surface of the negative electrode 20 has a second polymer layer 60, which is located between the negative electrode 20 and the solid electrolyte 40. The second polymer layer 60 is formed by curing monomers in the solid electrolyte prepolymer solution. The second polymer layer 60 has a strong bonding force with the negative electrode 20, which can effectively protect the battery 100 and isolate the positive and negative electrodes of the battery, preventing conduction between the positive and negative electrodes, and effectively improving the thermal stability and safety performance of the battery.

[0132] Understandably, the second polymer layer 60 is formed by polymerization of monomers in the solid electrolytic prepolymer solution.

[0133] The thicknesses of the first polymer layer 50 and the second polymer layer 60 are each independently 5–200 nm, for example, 5 nm, 10 nm, 30 nm, 50 nm, 60 nm, 80 nm, 1000 nm, 120 nm, 130 nm, 150 nm, 160 nm, 180 nm, 200 nm, etc. Within this thickness range, the positive and negative electrodes of the battery can be effectively isolated, effectively improving the thermal stability and safety performance of the battery.

[0134] It is understood that the battery described in this application is a solid-state battery. In some embodiments, the solid-state battery is a lithium-ion solid-state battery.

[0135] Fourthly, please refer to Figure 2 This application also provides a method for preparing a battery, comprising the following steps:

[0136] Step S11: Mix the monomer and electrolyte in a certain proportion to obtain a solid electrolyte prepolymer solution;

[0137] Step S12: Inject the solid electrolyte prepolymer solution into a dry cell composed of a positive electrode, a negative electrode, and a separator, and perform heat treatment to solidify the monomers in the solid electrolyte prepolymer solution to form a solid electrolyte, thereby obtaining a battery.

[0138] In step S11:

[0139] The types and ratios of the monomers and electrolytes are as described above and will not be repeated here.

[0140] In step S12:

[0141] After injecting the solid electrolyte prepolymer into a dry cell composed of a positive electrode, a negative electrode, and a separator, the process further includes: pre-encapsulation and standing at room temperature for 24–72 hours.

[0142] In some embodiments, the pre-packaging is performed using a thermoforming machine.

[0143] In some embodiments, the heat treatment temperature is 40–80°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc., and the time is 6–48 hours, for example, 6 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, 48 ​​hours, etc. Within the temperature and time range, the solid electrolyte prepolymer can be effectively solidified, and a stable polymer coating can be formed on the surface of the positive and negative electrode sheets, which is beneficial for preparing batteries with high thermal stability and safety.

[0144] The present application will be specifically described below through specific embodiments. These embodiments are only some embodiments of the present application and are not intended to limit the present application. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.

[0145] Example 1

[0146] Preparation of solid electrolyte prepolymer solution:

[0147] An electrolyte is provided, comprising an organic solvent, additives, and a lithium salt. The organic solvent comprises 30g of methyl ethyl carbonate, 20g of diethyl carbonate, 16g of propylene carbonate, 7g of ethylene carbonate, and 6g of fluoroethylene carbonate. The additives comprise 3.8g of adiponitrile and 0.2g of citrate anhydride. The lithium salt comprises 10g of lithium hexafluorophosphate and 5g of lithium difluorosulfonylimide.

[0148] Mix 2g of monomer 1 with 98g of electrolyte and mix thoroughly at room temperature in a drying room (relative humidity below 2%, dew point below -40℃) to obtain a solid electrolyte prepolymer solution.

[0149] Solid-state battery fabrication:

[0150] Lithium nickel cobalt manganese oxide (NCM811) positive electrode active material (97% by mass) and acetylene black conductive agent (1% by mass) are ground and mixed. Polyvinylidene fluoride (PVDF) (2% by mass) is added, and then 1-methyl-2-pyrrolidone (NMP) solvent is added and ground and mixed to obtain the positive electrode material. NMP is used for mixing, dispersing and adjusting the viscosity of the slurry. It volatilizes during drying and is not included in the mass percentage of the positive electrode material. The positive electrode material is coated on the surface of aluminum foil and dried to obtain the positive electrode.

[0151] 96% by weight of silicon-oxygen-carbon composite negative electrode material is added to 1% by weight of conductive carbon black SP and ground and mixed. 1% by weight of sodium carboxymethyl cellulose CMC and 2% by weight of polystyrene-butadiene copolymer SBR are added and then mixed in water. The mixture is ground, dispersed and mixed, coated on the surface of copper foil, and dried to obtain the negative electrode sheet.

[0152] The positive electrode, the negative electrode, and the separator are assembled to obtain a dry cell, wherein the separator is a polypropylene / polyethylene separator / polypropylene three-layer separator, i.e., PP / PE / PP separator, and the total thickness of the separator is 12 micrometers.

[0153] The solid electrolyte prepolymer is injected into the dry cell, pre-sealed using a heat sealer, left to stand at room temperature for 24 hours, then placed in a hot oven and slowly heated to 60°C for 24 hours. During the static heating process, the electrolyte prepolymer reacts inside the dry cell, and a solid electrolyte is obtained through in-situ thermal curing, thus forming a solid-state battery.

[0154] Example 2

[0155] This embodiment is basically the same as Embodiment 1, except that:

[0156] In this embodiment, the preparation method of the solid electrolyte prepolymer solution includes:

[0157] An electrolyte is provided, comprising an organic solvent, additives, and a lithium salt. The organic solvent comprises 30g of methyl ethyl carbonate, 20g of diethyl carbonate, 16g of propylene carbonate, 6g of ethylene carbonate, and 6g of fluoroethylene carbonate. The additives comprise 3.8g of adiponitrile and 0.2g of citrate anhydride. The lithium salt comprises 10g of lithium hexafluorophosphate and 5g of lithium difluorosulfonylimide.

[0158] Mix 3g of monomer 2 with 97g of electrolyte and mix them evenly at room temperature in a drying room (relative humidity below 2% and dew point below -40℃) to obtain a solid electrolyte prepolymer solution.

[0159] In this embodiment, the solid-state battery is slowly heated to 50°C during fabrication.

[0160] Example 3

[0161] This embodiment is basically the same as Embodiment 1, except that monomer 3 described above is used to replace monomer 1 in Embodiment 1. The organic solvent in this embodiment includes 25g diethyl carbonate, 25g dimethyl carbonate, 13g ethylene carbonate, 7g ethyl propionate, and 6g fluoroethylene carbonate. The additives in this embodiment include 5.2g succinic anionyl, 1.0g propanesulfonate lactone, and 0.8g triphenyl phosphate. The lithium salt in this embodiment includes 10g lithium bis(fluorosulfonyl)imide and 5g lithium bis(trifluoromethyl)sulfonyl)imide.

[0162] Example 4

[0163] This embodiment is basically the same as embodiment 1, except that in this embodiment, monomer 4 is used to replace monomer 1 in embodiment 1.

[0164] Example 5

[0165] This embodiment is basically the same as embodiment 1, except that in this embodiment, monomer 5 is used to replace monomer 1 in embodiment 1.

[0166] Example 6

[0167] This embodiment is basically the same as embodiment 1, except that in this embodiment, monomer 6 is used to replace monomer 1 in embodiment 1.

[0168] Example 7

[0169] This embodiment is basically the same as embodiment 1, except that in this embodiment, monomer 7 is used to replace monomer 1 in embodiment 1.

[0170] Example 8

[0171] This embodiment is basically the same as embodiment 1, except that in this embodiment, monomer 8 is used to replace monomer 1 in embodiment 1.

[0172] Example 9

[0173] This embodiment is basically the same as embodiment 1, except that in this embodiment, monomer 9 is used to replace monomer 1 in embodiment 1.

[0174] Example 10

[0175] This embodiment is basically the same as embodiment 1, except that in this embodiment, monomer 10 is used to replace monomer 1 in embodiment 1.

[0176] Example 11

[0177] This embodiment is basically the same as embodiment 1, except that in this embodiment, monomer 11 is used to replace monomer 1 in embodiment 1.

[0178] Example 12

[0179] This embodiment is basically the same as embodiment 1, except that in this embodiment, monomer 12 is used to replace monomer 1 in embodiment 1.

[0180] Example 13

[0181] This embodiment is basically the same as embodiment 1, except that in this embodiment, monomer 13 is used to replace monomer 1 in embodiment 1.

[0182] Example 14

[0183] This embodiment is basically the same as Embodiment 1, except that in the lithium electrolyte of this embodiment, the organic solvent is 79g of methyl ethyl carbonate, the additive is 4g of adiponitrile, and the lithium salt is 15g of lithium hexafluorophosphate.

[0184] Example 15

[0185] This embodiment is basically the same as Embodiment 1, except that in this embodiment, 5g of monomer 1 is mixed with 95g of electrolyte, and the organic solvent in this embodiment includes 28g of methyl ethyl carbonate, 20g of diethyl carbonate, 15g of propylene carbonate, 7g of ethylene carbonate, and 6g of fluoroethylene carbonate.

[0186] Example 16

[0187] This embodiment is basically the same as Embodiment 1, except that in this embodiment, 15g of monomer 1 is mixed with 85g of electrolyte, and the organic solvent in this embodiment includes 20g of methyl ethyl carbonate, 18g of diethyl carbonate, 15g of propylene carbonate, 7g of ethylene carbonate, and 6g of fluoroethylene carbonate.

[0188] Example 17

[0189] This embodiment is basically the same as Embodiment 14, except that in the lithium electrolyte of this embodiment, the organic solvent is 84g of methyl ethyl carbonate, the additive is 4g of adiponitrile, and the lithium salt is 10g of lithium hexafluorophosphate.

[0190] Example 18

[0191] This embodiment is basically the same as embodiment 14, except that in the lithium electrolyte of this embodiment, the organic solvent is 64g of methyl ethyl carbonate, the additive is 4g of adiponitrile, and the lithium salt is 30g of lithium hexafluorophosphate.

[0192] Example 19

[0193] This embodiment is basically the same as embodiment 14, except that in the lithium electrolyte of this embodiment, the organic solvent is 82g of methyl ethyl carbonate, the additive is 1g of adiponitrile, and the lithium salt is 15g of lithium hexafluorophosphate.

[0194] Example 20

[0195] This embodiment is basically the same as Embodiment 14, except that in the lithium electrolyte of this embodiment, the organic solvent is 73g of methyl ethyl carbonate, the additive is 10g of adiponitrile, and the lithium salt is 15g of lithium hexafluorophosphate.

[0196] Example 21

[0197] This embodiment is basically the same as Embodiment 1, except that in this embodiment, the temperature is slowly heated to 40°C.

[0198] Example 22

[0199] This embodiment is basically the same as Embodiment 1, except that in this embodiment, the temperature is slowly heated to 80°C.

[0200] Comparative Example 1

[0201] This comparative example is basically the same as Example 1, except that this comparative example uses comparative monomer 1 instead of monomer 1 in Example 1.

[0202] The chemical structural formula of monomer 1 is as follows:

[0203]

[0204] Comparative Example 2

[0205] This comparative example is basically the same as Example 1, except that comparative monomer 2 is used in this comparative example to replace monomer 1 in Example 1.

[0206] The chemical structural formula of monomer 2 is as follows:

[0207]

[0208] Comparative Example 3

[0209] This comparative example is basically the same as Example 1, except that the electrolyte in this comparative example includes an organic solvent and a lithium salt (without additives). The organic solvent includes 30g of methyl ethyl carbonate and 20g of diethyl carbonate, and the lithium salt includes 10g of lithium hexafluorophosphate. In addition, this comparative example mixes 40g of comparative monomer 3 with 60g of electrolyte.

[0210] The chemical structural formula of monomer 3 is as follows:

[0211]

[0212] Comparative Example 4

[0213] This comparative example is basically the same as Example 1, except that the solid electrolyte prepolymer solution in this example does not contain monomers.

[0214] The solid-state batteries of Example 1 and Comparative Example 4 were formed as follows: 0.02C constant current charging for 60 min, 0.05C constant current charging for 60 min, 0.1C constant current charging for 120 min, and 0.2C constant current charging for 180 min, with an upper limit voltage of 3.9V. Then, a 1C current was used for constant current followed by constant voltage charging and discharging (CC-CV method), with a cutoff voltage of 2.75–4.2V. The positive and negative electrodes of the formed batteries were then separated from the solid electrolyte to obtain the positive and negative electrodes of the solid-state battery of Example 1 and Comparative Example 4, respectively. SEM tests were then performed on the surfaces of the positive and negative electrodes that were originally in contact with the solid electrolyte. Figure 3 The SEM image shown is of the positive electrode sheet separated from the battery in Example 1. Figure 4 The image shown is a SEM image of the positive electrode sheet of Comparative Example 4, which was peeled off from the battery. Figure 5 The image shown is an SEM image of the negative electrode sheet stripped from the battery in Example 1. Figure 6 The image shown is a SEM image of the negative electrode sheet stripped from the battery in Comparative Example 4.

[0215] Depend on Figure 3 and Figure 4 It can be seen that the surface morphology of the positive electrode sheet peeled off from the solid-state battery of Example 1 is significantly different from that of the positive electrode sheet peeled off from the solid-state battery of Comparative Example 4. The surface of the positive electrode sheet peeled off from the solid-state battery of Example 1 has obvious material adhering to it. It is evident that the monomer in Example 1 forms a relatively uniform polymer layer in situ on the surface of the positive electrode sheet.

[0216] Depend on Figure 5 and Figure 6 It can be seen that the surface morphology of the negative electrode sheet peeled off from the solid-state battery of Example 1 is significantly different from that of the negative electrode sheet peeled off from the solid-state battery of Comparative Example 4. The surface of the negative electrode sheet peeled off from the solid-state battery of Example 1 has obvious material adhesion, forming a first polymer layer. It is evident that the monomer in Example 1 forms a relatively uniform polymer layer in situ on the surface of the negative electrode sheet.

[0217] Viscosity tests were performed on the solid electrolyte prepolymer solutions of Examples 1-22 and Comparative Examples 1-3, and the test results are shown in Table 1.

[0218] The batteries of Examples 1-22 and Comparative Examples 1-3 were formed as follows: constant current charging at 0.02C for 60 min, constant current charging at 0.05C for 60 min, constant current charging at 0.1C for 120 min, and constant current charging at 0.2C for 180 min, with an upper limit voltage of 3.9V. Then, constant current charging and discharging were performed using a current of 1C followed by constant voltage charging, i.e., CC-CV method, with a cutoff voltage of 2.75-4.2V.

[0219] The peel strength between the electrode and the solid electrolyte, the thermal decomposition temperature of the solid electrolyte, and the peak enthalpy temperature of the solid electrolyte were tested on the formed battery. The test results are shown in Table 1 and Table 2. Figures 7-9 ,in, Figure 7 This is a path-load diagram showing the peel strength of the battery in Example 1. Figure 8 This is the DTG curve of the solid electrolyte in Example 1. Figure 9 The differential scanning calorimetry (DSC) curve of the solid electrolyte in Example 1 is shown.

[0220] The viscosity test method is as follows: The viscosity of the solid electrolyte prepolymer solution is tested using an NDJ-5S digital rotary viscometer. The solid electrolyte prepolymer solution is poured into a flat-bottomed container with a diameter greater than 60mm. The temperature of the solid electrolyte prepolymer solution is maintained at 25℃, and the operating surface is stable and vibration-free. The instrument protective bracket is screwed into the lower end of the instrument in reverse. Using the L0 rotor, it is screwed counterclockwise into the universal joint of the instrument. The lifting knob is rotated to slowly immerse the rotor in the solid electrolyte prepolymer solution until the rotor's liquid level mark (the groove scale) is flush with the liquid surface. The instrument is then leveled again. The rotor selection key is pressed to select the rotation speed, and then the OK key is pressed. The rotor begins to rotate. After the displayed value stabilizes, the stop key is pressed to read the viscosity value.

[0221] Peel strength was tested according to IPC-TM-6502.8 method using a Shimadzu AG-X 50N peeling machine. The mirror-finished steel plate was wiped with alcohol, and double-sided tape was applied to the mirror-finished copper plate. During the application process, it was ensured that the tape adhered firmly to the steel plate without air bubbles. The discharged battery was disassembled to obtain a single-cell battery material with the positive electrode, separator, and negative electrode bonded together. An organic solid electrolyte electrode sheet was placed between the three. The two sides of the battery material were metal foil: aluminum foil for the positive electrode and copper foil for the negative electrode. The electrode sheet was cut into 25mm*220mm strips. The positive aluminum foil side was adhered to the steel plate with double-sided tape, the electrode parallel to the steel plate, and rolled back and forth three times using an automatic pressure roller. The peeling machine was turned on, and the peeling speed was set to 50mm / min. The lower clamp held the steel plate, and the upper clamp held the smooth copper foil of the negative electrode. The speed was zeroed, and the test began. Each material was tested five times, and the average value was taken. According to the formula: A=F / L, where A is the peel strength in mN / mm, F is the average peel force in mN, and L is the test width of the sample in mm;

[0222] Thermal decomposition temperature test: Solid electrolyte prepolymers were prepared using the methods of Examples 1-22 and Comparative Examples 1-3. Solid electrolytes were then cured using the curing methods of the solid electrolyte prepolymers of Examples 1-22 and Comparative Examples 1-3, respectively. 10 mg of each solid electrolyte was weighed using a 1 / 20 ...

[0223] Exothermic peak temperature test: Solid electrolyte prepolymers were prepared using the methods of Examples 1-22 and Comparative Examples 1-3. Solid electrolytes were then cured using the curing methods of the solid electrolyte prepolymers of Examples 1-22 and Comparative Examples 1-3, respectively. 10 mg of each solid electrolyte was weighed using a 1 / 2500 balance. The DSC instrument was preheated for 3 hours. The weighed solid electrolyte was then placed in a high-pressure crucible and sealed using a press. The DSC instrument parameters were set, and the temperature was increased from 35°C to 600°C at a rate of 5°C / min. Nitrogen gas was purged during the test at a rate of 40 mL / min. The heat flow rate versus temperature curve (DSC) was obtained, and the temperature corresponding to the highest exothermic peak was read as the exothermic peak temperature P (°C).

[0224] Table 1:

[0225]

[0226]

[0227]

[0228] Depend on Figure 7 It is known that the solid electrolyte film has excellent adhesion to the positive and negative electrode surfaces and exhibits high peel strength, which can ensure efficient bonding between the polymer electrolyte and the positive and negative electrode active materials. During the charging and discharging process of the battery, the positive and negative electrode active materials undergo phase transitions, resulting in volume shrinkage and expansion. The high adhesion peel strength can ensure effective contact between the positive and negative electrodes and the electrolyte, improving the interface stability of the battery. At the same time, under high external temperatures, the separator in conventional systems shrinks at temperatures exceeding 150°C, causing a short circuit at the contact between the positive and negative electrodes, which in turn leads to violent heat release. In the organic solid electrolyte protected by this patent, it can form an adhesion with the positive and negative electrodes, effectively adsorbing the separator and firmly bonding it to the electrode surface, avoiding short circuits and violent heat release caused by large-area contact of the positive and negative electrodes due to heat, and improving the high-temperature resistance of the battery.

[0229] It can be seen from Figure 8 that: The DTG curve of the solid electrolyte in Example 1 shows the temperature corresponding to the fastest thermal weight loss rate, that is, the defined thermal decomposition temperature T is 201 °C, which is much higher than the operating temperature of conventional batteries, indicating that the application of organic solid electrolytes can improve the thermal safety performance of batteries. Before the thermal decomposition temperature T, some solvents volatilize due to heat at high temperatures, resulting in weight loss. As the temperature increases, the weight loss caused by solvent volatilization becomes more obvious. This part of the solvent volatilization absorbs heat due to its own thermal evaporation, slowing down the rate of temperature rise.

[0230] It can be seen from Figure 9 that: The DSC curve of the organic solid electrolyte in Example 1 shows the relationship between the energy difference transmitted to the sample and the reference blank sample and temperature. The largest enthalpy change appears at 210 °C, corresponding to exothermic reactions such as partial destruction and decomposition of the cross-linked structure of the organic solid electrolyte in the high-pressure crucible. There is an endothermic hump in the temperature range before this, corresponding to the slow volatilization and endothermic effect of the solvent in the electrolyte. This DSC curve shows that the enthalpy peak temperature of the organic solid electrolyte is much higher than the conventional heat resistance temperature of the battery, and its application can improve the thermal safety performance of the battery.

[0231] It can be seen from Table 1 that: The solid electrolytes of Examples 1 to 22 satisfy the relational expression B×50 < (T + P)×W×A < B×250 described above; compared with the batteries of Comparative Examples 1 to 4, the battery of Example 22 has a higher thermal decomposition temperature and a higher enthalpy peak temperature; it can be seen that the solid battery prepared by using the solid electrolyte prepolymer solution described in this application has high thermal stability, and thus can have high safety.

[0232] The technical solutions provided by the embodiments of the present application have been introduced in detail above. Specific examples are used in this article to elaborate on the principles and implementation manners of the present application. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A solid electrolyte, characterized in that, The solid electrolyte is obtained by curing a solid electrolyte prepolymer; the solid electrolyte prepolymer comprises a monomer and an electrolyte, the electrolyte comprises a lithium salt, an organic solvent and an additive, and the monomer comprises one or more compounds having the structural formula shown in formula (I): （I） Where m is any integer from 2 to 8; L is a linking group, selected from substituted or unsubstituted -(CH2). n2 CH=CH(CH2) n3 -, substituted or unsubstituted -(CH2) n4 C≡C(CH2) n5 -, substituted or unsubstituted -(CH2) n6 -O- (CH2) n7 -, substituted or unsubstituted -(CH2) n8 CO(CH2) n9 - Substituted or unsubstituted amino groups, substituted or unsubstituted C3~C 30 One or more of cycloalkyl, aryl with 6 to 60 substituted or unsubstituted cyclic atoms, and heteroaryl with 6 to 60 substituted or unsubstituted cyclic atoms, wherein n2 to n9 are each independently selected from integers from 1 to 5; R1, R2, and R3 are each independently selected from hydrogen, substituted or unsubstituted C1~C2. 30 Alkyl, substituted or unsubstituted C3~C 30 One or more of the following: cycloalkyl groups, substituted or unsubstituted aryl groups having a ring atom number of 6 to 60; The solid electrolyte satisfies the following relationship: B×50<(T+P)×W×A <B×250; Where A is the peel strength, B is the viscosity of the solid electrolyte prepolymer, T is the thermal decomposition temperature of the solid electrolyte, P is the exothermic peak temperature of the solid electrolyte, and W is the mass percentage of the monomer in the solid electrolyte prepolymer. The value of A ranges from 20 to 200 mN / mm; The value of B is in the range of 4~20 cP; The value of T is in the range of 100~350℃; The value of P ranges from 100 to 400℃; The value of W ranges from 1% to 15%. The peel strength test process includes: preparing a battery by solidifying a solid electrolyte prepolymer solution; disassembling the fully discharged battery after battery formation to obtain a single-cell battery material with a positive electrode, separator, and negative electrode bonded together; the positive electrode side of the single-cell battery material is aluminum foil, and the negative electrode side of the single-cell battery material is copper foil; fixing the positive electrode side to a steel plate; clamping the steel plate with the lower clamp of the peeling machine; and clamping the copper foil on the negative electrode side with the upper clamp for testing.

2. The solid electrolyte as described in claim 1, characterized in that, Includes at least one of the following features (1) to (2): (1) The L is selected from substituted or unsubstituted C3~C 20 One or more of cycloalkyl, aryl with 6 to 30 substituted or unsubstituted ring atoms, and heteroaryl with 6 to 30 substituted or unsubstituted ring atoms; (2) R1, R2, and R3 are each independently selected from substituted or unsubstituted C1~C1. 20 Alkyl, substituted or unsubstituted C3~C 20 One or more of the following: cycloalkyl, substituted or unsubstituted aryl groups having a ring atom number of 6 to 30.

3. The solid electrolyte as described in claim 1, characterized in that, Includes at least one of the following features (1) to (2): (1) The L is selected from substituted or unsubstituted C3~C 10 One or more of cycloalkyl, substituted or unsubstituted aryl groups having 6 to 15 ring atoms, and substituted or unsubstituted heteroaryl groups having 6 to 15 ring atoms; (2) R1, R2, and R3 are each independently selected from substituted or unsubstituted C1~C1. 10 Alkyl, substituted or unsubstituted C3~C 10 One or more of cycloalkyl, substituted or unsubstituted aryl groups having a ring atom number of 6 to 20.

4. The solid electrolyte as described in claim 1, characterized in that, R1, R2, and R3 are each independently selected from one or more combinations of substituted or unsubstituted C1-C8 alkyl groups, substituted or unsubstituted C3-C8 cycloalkyl groups, and substituted or unsubstituted aryl groups having 6 to 10 ring atoms.

5. The solid electrolyte as described in claim 1, characterized in that, The L is selected from one or more of the following groups: 、 、 、 、 、 ； Among them, L1 to L 19 As linking groups, each is independently selected from single bonds and -(CH2). m’ - any one of the following, where m' is selected from any integer from 1 to 5.

6. The solid electrolyte as described in claim 1, characterized in that, The monomer is selected from one or more compounds shown in the following structural formulas:

7. The solid electrolyte as described in claim 1, characterized in that, Includes at least one of the following features (1) to (7): (1) m is any integer from 2 to 4; (2) The lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalate)borate, and lithium difluorooxalateborate. (3) The organic solvent includes one or more of carbonate organic solvents and carboxylic acid ester organic solvents, wherein the carbonate organic solvent includes one or more of methyl ethyl carbonate, diethyl carbonate, propylene carbonate, ethylene carbonate, and fluoroethylene carbonate, and the carboxylic acid ester organic solvent includes one or more of fluoroethylene carbonate, ethyl propionate, and propyl propionate. (4) The additives are selected from nitrile additives and ester additives. The nitrile additives include one or more of adiponitrile, glutaronitrile, succinate, and ethylene glycol bis(propionitrile) ether. The ester additives include one or more of vinyl sulfate, propanesulfonic acid lactone, citrate anhydride, and triphenyl phosphite. (5) In the solid electrolyte prepolymer solution, the content of the monomer is 1~15 wt%, and the content of the electrolyte is 85~99 wt%; (6) In the electrolyte, the content of the lithium salt is 10-30 wt%, the content of the additive is 1-10 wt%, and the content of the organic solvent is 60-80 wt%; (7) The viscosity range of the solid electrolyte prepolymer is 4~20 cP.

8. A battery, characterized in that, It includes a positive electrode, a negative electrode, and a solid electrolyte as described in any one of claims 1 to 7.

9. The battery as claimed in claim 8, characterized in that, Includes at least one of the following features (1) to (2): (1) A first polymer layer is bonded to the surface of the positive electrode sheet, and the first polymer layer is located between the positive electrode sheet and the solid electrolyte; (2) The surface of the negative electrode sheet has a second polymer layer, which is located between the negative electrode sheet and the solid electrolyte.

10. The battery as claimed in claim 9, characterized in that, Includes at least one of the following features (1) to (3): (1) The first polymer layer is formed by polymerization of monomers in the solid electrolyte prepolymer solution; (2) The second polymer layer is formed by polymerization of monomers in the solid electrolyte prepolymer solution; (3) The thickness of the first polymer layer and the second polymer layer are each 5~200 nm.

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