Composite sulfide electrolyte, and preparation method therefor and use thereof

Abstract

The present invention relates to a composite sulfide electrolyte, and a preparation method therefor and a use thereof. The composite sulfide electrolyte has a three-dimensional crosslinked structure formed by connecting a sulfide electrolyte and a dynamic bond-containing crosslinked polymer by means of chemical bonds. The polymer contains a sulfur element and exhibits relatively higher stability when interacting with the sulfide electrolyte, the chemical crosslinking between the sulfide electrolyte and the dynamic bond-containing crosslinked polymer is formed by means of multiple chemical bonds, such as a disulfide bond and an amido bond, and a strong binding force and self-healing function are provided, in order to simultaneously solve the problems of interfacial delamination and cracking caused by mechanical stress inside the sulfide electrolyte. When applied in an all-solid-state battery, the composite sulfide electrolyte can improve the limiting current density and cycle stability of the all-solid-state battery.

Description

Composite sulfide electrolyte and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application 202311869967.9 filed on December 29, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the field of solid electrolytes, and in particular to a composite sulfide electrolyte and a preparation method and application thereof. Background Art

[0004] Lithium-ion batteries and lead-acid batteries are the most widely used electrochemical energy storage. Compared with lead-acid batteries, lithium-ion batteries have advantages in specific energy, cycle life, and service life. The batteries commonly used at present are liquid-phase batteries, which contain organic solvents, are flammable, and pose safety risks. Using inorganic solid electrolytes instead of organic flammable electrolytes is an effective measure to solve this problem. The use of inorganic solid electrolytes can effectively alleviate the problem of lithium dendrites and increase energy density. Among inorganic solid electrolytes, sulfide electrolytes have attracted widespread attention due to their high ionic conductivity. However, there is internal mechanical stress between sulfide electrolytes and electrode materials during the continuous lithium insertion and deintercalation process, which leads to interfacial delamination and cracks in the electrolyte layer, resulting in battery degradation or failure. Therefore, effective measures need to be taken to alleviate this problem and improve the electrochemical performance of the battery.

[0005] Currently, most approaches to alleviate these issues involve introducing polymers into sulfide electrolytes or adding polymer interface layers. Ideal sulfide-polymer composite electrolytes should possess the mechanical flexibility of the polymer matrix, strong interactions at the polymer / electrolyte interface to prevent delamination, and three-dimensional continuous channels to achieve high ionic conductivity. However, existing techniques primarily combine sulfide electrolytes and polymers through physical mixing. The resulting composite electrolytes still exhibit delamination during prolonged lithium insertion and deintercalation, failing to effectively address the cracking and interfacial delamination issues caused by internal mechanical stress.

[0006] CN112909322A discloses an in-situ formed sulfide composite solid electrolyte, including a polymer three-dimensional skeleton and an interpenetrating network structure formed with the sulfide electrolyte. The network structure formed by the sulfide electrolyte in the composite solid electrolyte serves as the main carrier of high ionic conductivity, and the in-situ formed polymer three-dimensional skeleton plays a role in supporting and reinforcing, improving the interfacial ionic conductivity of the sulfide electrolyte, and increasing the flexibility of the electrolyte. However, the sulfide electrolyte and the polymer in the composite solid electrolyte are physically mixed and do not involve chemical bonding, so the improvement ability of internal mechanical stress to generate cracks and interface delamination is limited. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of cracks and interface peeling caused by internal mechanical stress in the prior art, and to provide a composite sulfide electrolyte and its preparation method and application. The composite sulfide electrolyte forms chemical crosslinks between the sulfide electrolyte and the cross-linked polymer containing dynamic bonds through multiple chemical bonds, and contains disulfide bonds and amide bonds. It has strong binding force and self-repairing function, which can effectively improve the interface stratification and cracks caused by internal mechanical stress in the electrolyte or electrolyte membrane during the cycle, thereby improving the battery's limiting current density, cycle performance and other properties.

[0008] To achieve the above objectives, the present invention provides a composite sulfide electrolyte in a first aspect. The composite sulfide electrolyte comprises a three-dimensional cross-linked structure formed by chemically connecting a sulfide electrolyte and a cross-linked polymer containing dynamic bonds.

[0009] A second aspect of the present invention provides a method for preparing a composite sulfide electrolyte, the preparation method comprising the following steps:

[0010] Under polymerization reaction conditions, the sulfide electrolyte is in-situ cured with monomer A, monomer B and optional monomer C in an optional solvent; wherein the monomer A is selected from one or more compounds having a structure represented by formula (1); the monomer B is selected from one or more compounds containing an amine group and a compound containing both an amine group and a disulfide bond; and the monomer C is selected from one or more compounds containing a double bond;

[0011] In formula (1), R1 is a group containing a carbon-carbon double bond or a carbon-carbon triple bond.

[0012] The third aspect of the present invention provides a composite sulfide electrolyte prepared by the preparation method described in the second aspect.

[0013] A fourth aspect of the present invention provides use of the composite sulfide electrolyte described in the first and third aspects in electrodes and batteries.

[0014] A fifth aspect of the present invention provides an electrode comprising a positive electrode and / or a negative electrode, wherein the positive electrode comprises a positive electrode active material and the composite sulfide electrolyte described in the first and third aspects; and the negative electrode comprises a negative electrode active material and the composite sulfide electrolyte described in the first and third aspects.

[0015] A sixth aspect of the present invention provides an all-solid-state battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte contains the composite sulfide electrolyte described in the first and third aspects above.

[0016] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0017] 1) The composite sulfide electrolyte provided by the present invention contains a three-dimensional cross-linked structure formed by chemical bonds between a sulfide electrolyte and a cross-linked polymer containing dynamic bonds. The polymer contains the S element and is relatively more stable with the sulfide electrolyte. The sulfide electrolyte and the cross-linked polymer containing dynamic bonds are chemically cross-linked through multiple chemical bonds such as phosphorus-nitrogen bonds and disulfide bonds. It has strong binding force and self-repair function, and is expected to simultaneously solve the problems of interface stratification and cracking caused by mechanical stress inside the sulfide electrolyte.

[0018] 2) The method of the present invention adopts an in-situ reaction mode. After the sulfide electrolyte ion conductive channel is formed, the polymer is solidified in situ in the gaps between the sulfide electrolyte particles. On the basis of not affecting the ion transport of the sulfide electrolyte, the porosity of the sulfide electrolyte is reduced to form a three-dimensional conductive network. Moreover, the sulfide electrolyte and the polymer are more evenly distributed and the contact is closer.

[0019] 3) The composite sulfide electrolyte of the present invention is applied to all-solid-state batteries, which can improve the limiting current density and cycle stability of all-solid-state batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 is an XPS data diagram of the composite sulfide electrolyte prepared in Example 1 of the present invention;

[0021] FIG2 is an infrared spectrum of the composite sulfide electrolyte prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0022] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0023] A first aspect of the present invention provides a composite sulfide electrolyte comprising a three-dimensional cross-linked structure formed by chemically connecting a sulfide electrolyte and a cross-linked polymer containing dynamic bonds.

[0024] In some embodiments of the present invention, the chemical bond is selected from at least one of a PN bond, a SC bond, and a SS bond, and preferably contains all three of the above chemical bonds.

[0025] In the present invention, the sulfide electrolyte and the cross-linked polymer containing dynamic bonds are chemically cross-linked through multiple chemical bonds. The cross-linked polymer containing dynamic bonds contains the S element and is relatively more stable with the sulfide electrolyte. It also contains chemical bonds such as disulfide bonds and amide bonds, has strong binding force and self-repair function, and is expected to solve the interface stratification and cracking problems caused by mechanical stress inside the sulfide electrolyte.

[0026] In some embodiments of the present invention, the composite sulfide electrolyte is obtained by in-situ curing of a sulfide electrolyte with a monomer A, a monomer B, and an optional monomer C; wherein the monomer A is selected from one or more compounds having a structure represented by formula (1); the monomer B is selected from one or more compounds containing an amine group and a compound containing both an amine group and a disulfide bond; and the monomer C is selected from one or more compounds containing a double bond.

[0027] In formula (1), R1 is a group containing a carbon-carbon double bond or a carbon-carbon triple bond.

[0028] In the present invention, monomer A is a compound containing both thiolactone and a double bond or a triple bond, and monomer B is selected from one or more of an amine-containing compound and a compound containing both an amine group and a disulfide bond, preferably one or more of a compound containing both an amine group and a disulfide bond. The monomers used are in situ polymerized in the gaps between the sulfide electrolyte particles to form a polymer; the formed polymer can react with the sulfide electrolyte through nucleophilic addition, thiolactone ring opening, and other reactions to form a structure cross-linked by chemical bonds; the chemical bonds formed above ensure a strong connection between the sulfide electrolyte and the polymer, wherein the SS bond and the amide bond both have self-repairing functions.

[0029] In some embodiments of the present invention, the sulfide electrolyte is selected from one or more sulfide electrolytes containing P=S bonds.

[0030] In some preferred embodiments of the present invention, the sulfide electrolyte is selected from one or more of LiM1PSX1, LiPSX1, LiM2PS and lithium thiophosphate (LPS); wherein M1 is selected from one or more of Ge, Si, Nb, Sb, Zn, Fe, Bi, Al, In, Cu, Ce and Sn; X1 is selected from one or more of Cl, Br, I, O, N; M2 is selected from one or more of Ge, Si, P, Sn, Al, As, Sb, Zn, Y and Ga.

[0031] More preferably, the sulfide electrolyte is selected from Li6PS5Cl (LPSCl), Li 5.5 PS 4.5 Cl 1.5 、Li3PS4、Li7P3S 11 、Li 10 GeP2S 12 (LGPS) and Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 One or more of .

[0032] In some embodiments of the present invention, the monomer A is selected from one or more compounds having structures shown in Formula A-1 to Formula A-17;

[0033] Wherein, R is a hydrocarbon group containing 1 to 9 carbon atoms with or without an alkyl branch; Z1 is hydrogen or methyl; and Z2 is a saturated alkylene group containing 1 to 9 carbon atoms with or without an alkyl branch.

[0034] In some embodiments of the present invention, the monomer B is selected from one or more of n-hexylamine, polyethyleneimine, ethylenediamine, propylenediamine, butylenediamine, 2,5-diaminopentanoic acid, tris(2-aminoethyl)amine, 4,4'-dithiodiphenylamine, 2,2'-dithiodiethylamine, 4,4'-dithiodiylbis(2-aminobutyric acid), 3,3'-dithiodiylbis(2-aminopropionic acid), disulfide formamidine, 2-(2-amino-5-methoxyphenyl)disulfide-4-methoxyaniline and a substance having a structure represented by formula B-1;

[0035] Preferably, the monomer B is selected from one or more of 4,4'-dithiodiphenylamine, 2,2'-dithiodiethylamine, 4,4'-dithiodiylbis(2-aminobutyric acid), 3,3'-dithiodiylbis(2-aminopropionic acid), disulfide formamidine, 2-(2-amino-5-methoxyphenyl)disulfide-4-methoxyaniline and a substance having a structure shown in formula B-1.

[0036] In some embodiments of the present invention, the monomer C is selected from one or more of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, diethylene glycol diacrylate and triethylene glycol diacrylate.

[0037] In the present invention, monomer C can be optionally added during the reaction to further improve the mechanical strength and ion transport of the composite sulfide electrolyte.

[0038] In some embodiments of the present invention, the molar ratio of monomer A, monomer B and monomer C is 1-5:0.5-5:0-4.5, preferably 1-2:1-3:0.5-1.

[0039] In some embodiments of the present invention, the ratio of the total mass of the sulfide electrolyte to the monomer A, the monomer B and the monomer C is 5-9.8:0.2-5, preferably 7-9.8:0.2-3.

[0040] In the present invention, the positive electrode active material is at least one selected from iron sulfide, ferrous sulfide, lithium iron phosphate, lithium cobaltate, lithium manganate, lithium titanate, ternary materials and modified materials thereof.

[0041] In the present invention, the negative electrode active material is at least one selected from the group consisting of graphite, elemental silicon, silicon oxide, silicon monoxide, transition metal oxides, transition metal sulfides, transition metal phosphides, and silicon carbide.

[0042] In the present invention, the initiator is selected from one or more of azobisisobutyronitrile, benzoyl peroxide, azobisisoheptanenitrile, ammonium persulfate and azobisisobutylimidazoline hydrochloride.

[0043] In the present invention, lithium salt additives such as lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bis(trifluoromethylsulfonylimide), lithium bis(fluorosulfonylimide) and the like may be added during the preparation process to further enhance the lithium ion conduction of the composite electrolyte.

[0044] A second aspect of the present invention provides a method for preparing a composite sulfide electrolyte, the preparation method comprising the following steps:

[0045] Under polymerization reaction conditions, a sulfide electrolyte is in-situ cured with monomer A, monomer B, and optional monomer C in an optional solvent; wherein the monomer A is selected from one or more compounds having a structure represented by formula (1); the monomer B is selected from one or more compounds containing an amine group and a disulfide bond, preferably one or more compounds containing an amine group and a disulfide bond; and the monomer C is selected from one or more compounds containing a double bond;

[0046] In formula (1), R1 is a group containing a carbon-carbon double bond or a carbon-carbon triple bond.

[0047] In the present invention, the preparation method uses a sulfide electrolyte as a main body and performs in-situ curing with monomer A, monomer B and optional monomer C in an optional solvent in the presence of an initiator to obtain a composite sulfide electrolyte.

[0048] In some embodiments of the present invention, the sulfide electrolyte is selected from one or more sulfide electrolytes containing P=S bonds.

[0049] In some embodiments of the present invention, the monomer A is selected from one or more compounds having structures represented by Formula A-1 to Formula A-17.

[0050] In some embodiments of the present invention, the monomer B is selected from one or more of n-hexylamine, polyethyleneimine, ethylenediamine, propylenediamine, butylenediamine, 2,5-diaminopentanoic acid, tris(2-aminoethyl)amine, 4,4'-dithiodiphenylamine, 2,2'-dithiodiethylamine, 4,4'-dithiodiylbis(2-aminobutyric acid), 3,3'-dithiodiylbis(2-aminopropionic acid), disulfide formamide, 2-(2-amino-5-methoxyphenyl)disulfide-4-methoxyaniline and a substance having a structure shown in formula B-1.

[0051] Preferably, the monomer B is selected from one or more of 4,4'-dithiodiphenylamine, 2,2'-dithiodiethylamine, 4,4'-dithiodiylbis(2-aminobutyric acid), 3,3'-dithiodiylbis(2-aminopropionic acid), disulfide formamidine, 2-(2-amino-5-methoxyphenyl)disulfide-4-methoxyaniline and a substance having a structure shown in formula B-1.

[0052] In some embodiments of the present invention, the monomer C is selected from one or more of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, diethylene glycol diacrylate and triethylene glycol diacrylate.

[0053] In the present invention, the specific selection of the sulfide electrolyte, monomer A, monomer B and monomer C is the same as that of the first aspect mentioned above. Please refer to the previous description for details and will not be repeated here.

[0054] In some embodiments of the present invention, the solvent is selected from one or more low-polarity solvents.

[0055] In the present invention, the low polarity solvent includes but is not limited to tetrahydrofuran, ether solvents, alkane solvents, ester solvents, etc., and the amount of the solvent added is 0-50%.

[0056] In some embodiments of the present invention, the molar ratio of monomer A, monomer B and monomer C is 1-5:0.5-5:0-4.5, preferably 1-2:1-3:0.5-1.

[0057] In some embodiments of the present invention, the ratio of the total mass of the sulfide electrolyte to the monomer A, the monomer B and the monomer C is 5-9.8:0.2-5, preferably 7-9.8:0.2-3.

[0058] In the present invention, if the number of amino groups on monomer B is reduced or the amount of monomer B added is too small, the number of chemical bonds formed will decrease, the self-repair performance will decrease, and the battery cycle performance will deteriorate; conversely, the cycle performance will improve. If the amount of monomer C added is further increased, the ion conductivity of the composite electrolyte will be improved, the flexibility of the electrode sheet will be enhanced, and the battery cycle performance will be improved.

[0059] In some embodiments of the present invention, the polymerization reaction conditions include: temperature of 45-80° C. and time of 1-24 h.

[0060] In some embodiments of the present invention, the polymerization reaction conditions include: adding an initiator; the initiator is selected from one or more of azobisisobutyronitrile, benzoyl peroxide, azobisisoheptanenitrile, ammonium persulfate and azobisisobutylimidazoline hydrochloride.

[0061] In the present invention, a lithium salt additive may be added during the polymerization reaction to further enhance the lithium ion conduction function of the composite electrolyte.

[0062] In some embodiments of the present invention, the polymerization reaction conditions include the addition of a lithium salt additive; the lithium salt additive is selected from one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bis(trifluoromethylsulfonylimide), and lithium bis(fluorosulfonylimide). In the present invention, in-situ curing is carried out under polymerization reaction conditions; that is, the polymerization reaction conditions are the same as the in-situ curing conditions.

[0063] The third aspect of the present invention provides a composite sulfide electrolyte prepared by the preparation method described in the second aspect.

[0064] The fourth aspect of the present invention provides the use of the composite sulfide electrolyte as described in the first and third aspects in electrodes and batteries, especially in all-solid-state batteries.

[0065] A fifth aspect of the present invention provides an electrode comprising a positive electrode and / or a negative electrode, wherein the positive electrode comprises a positive electrode active material and the composite sulfide electrolyte described in the first and third aspects; and the negative electrode comprises a negative electrode active material and the composite sulfide electrolyte described in the first and third aspects. In the present invention, the positive electrode active material is selected from at least one of iron sulfide, ferrous sulfide, lithium iron phosphate, lithium cobaltate, lithium manganate, lithium titanate, ternary materials, and modified materials thereof.

[0066] In the present invention, the negative electrode active material is at least one selected from graphite, elemental silicon, silicon oxide, silicon monoxide, transition metal oxides, transition metal sulfides, transition metal phosphides and silicon carbide.

[0067] The sixth aspect of the present invention provides an all-solid-state battery, comprising a positive electrode, a negative electrode and an electrolyte; wherein the electrolyte contains the composite sulfide electrolyte described in the first and third aspects above.

[0068] In some embodiments of the present invention, the positive electrode includes a positive electrode active material and the composite sulfide electrolyte described in the first and third aspects.

[0069] In some embodiments of the present invention, the negative electrode includes a negative electrode active material and the composite sulfide electrolyte described in the first and third aspects above.

[0070] The composite sulfide electrolyte of the present invention is applied to all-solid-state batteries, and can improve the limiting current density and cycle stability of the all-solid-state batteries.

[0071] The present invention will be described in detail below through examples. In the following examples and comparative examples, unless otherwise specified, all starting materials used are commercially available.

[0072] Preparation Example

[0073] Preparation of Monomer A: 9.2 g (0.06 mol) of DL-homocysteine ​​thiolactone hydrochloride and 24 g (2.37 mol) of triethylamine were dissolved in 900 mL of dichloromethane, stirred and dissolved in an ice-water bath, and 9.06 g (0.1 mol) of acryloyl chloride was slowly added dropwise, the temperature was controlled not to exceed 0°C, and the reaction was carried out for 5 hours; the organic phase after the reaction was washed three times with saturated brine and dried over anhydrous sodium sulfate. After filtering, the filtrate was concentrated under reduced pressure, and the residue was dissolved in 180 mL of ethyl acetate, filtered through a short silica column, and the filtrate was recrystallized using petroleum ether and filtered to obtain Monomer A.

[0074] Test Case

[0075] Preparation of a polymer mixture: Monomer A prepared in Preparation Example was mixed with n-hexylamine, polyethylene glycol diacrylate, and azobisisobutyronitrile in a molar ratio of 2:1:1:0.01 to obtain a mixture; 1 wt % of lithium bistrifluoromethylsulfonyl imide (LiTFSI) was added to the mixture, and the mixture was stirred for 30 minutes until uniformly mixed to obtain a polymer mixture;

[0076] Preparation of composite sulfide electrolyte: The sulfide electrolyte Li6PS5Cl was added to the above-mentioned polymer mixture, wherein the mass ratio of sulfide electrolyte to polymer mixture was 9.5:0.5, and then the solvent tetrahydrofuran was added with a solid content of 50wt%. Stirring for 30 minutes, after sufficient infiltration, it was applied on the polytetrafluoroethylene substrate using a scraper coating method, and heated at 60°C for 4 hours for in-situ curing to obtain a composite sulfide electrolyte with a thickness of 200μm.

[0077] The XPS data of the composite sulfide electrolyte prepared in the above test example is shown in Figure 1. As can be seen from Figure 1, there is an obvious PN bond peak, indicating that cross-linking is successfully generated between the sulfide electrolyte and the polymer, which is impossible for the original electrolyte Li6PS5Cl.

[0078] The infrared spectrum of the composite sulfide electrolyte prepared in the above test example is shown in FIG2 . As can be seen from FIG2 , the composite sulfide electrolyte has an infrared spectrum at 2570 cm -1 The peaks that appeared proved the formation of disulfide bonds (SS bonds) in the final product.

[0079] Example 1

[0080] Preparation of a polymer mixture: Monomer A prepared in Preparation Example was mixed with diphenyl disulfide, polyethylene glycol diacrylate, and azobisisobutyronitrile in a molar ratio of 2:1:1:0.01 to obtain a mixture; 1 wt % of lithium bistrifluoromethylsulfonyl imide (LiTFSI) was added to the mixture, and the mixture was stirred for 30 minutes. After mixing evenly, a polymer mixture was obtained;

[0081] Preparation of composite sulfide electrolyte: The sulfide electrolyte Li6PS5Cl was added to the above-mentioned polymer mixture, wherein the mass ratio of sulfide electrolyte to polymer mixture was 9.5:0.5, and then the solvent tetrahydrofuran was added with a solid content of 50wt%. Stirring for 30 minutes, after sufficient infiltration, it was applied on the polytetrafluoroethylene substrate using a scraper coating method, and heated at 60°C for 4 hours for in-situ curing to obtain a composite sulfide electrolyte with a thickness of 200μm.

[0082] Example 2

[0083] A composite sulfide electrolyte was prepared according to the method of Example 1, except that the sulfide electrolyte was Li3PS4; the remaining steps were the same as those of Example 1.

[0084] Example 3

[0085] A composite sulfide electrolyte was prepared according to the method of Example 1, except that the monomer A prepared in the Preparation Example was mixed with diphenyl disulfide, polyethylene glycol diacrylate, and azobisisobutyronitrile in a molar ratio of 2:1:0.5:0.01 to obtain a mixture; the remaining steps were the same as in Example 1.

[0086] Example 4

[0087] A composite sulfide electrolyte was prepared according to the method of Example 1, except that the monomer A prepared in the Preparation Example was mixed with diphenyl disulfide, polyethylene glycol diacrylate, and azobisisobutyronitrile in a molar ratio of 2:1:2:0.01 to obtain a mixture; the remaining steps were the same as in Example 1.

[0088] Example 5

[0089] A composite sulfide electrolyte was prepared according to the method of Example 1, except that the coated electrolyte membrane was left to stand at room temperature for 24 hours under an argon atmosphere, thereby obtaining a composite sulfide electrolyte with a thickness of 200 μm.

[0090] Comparative Example 1

[0091] A composite sulfide electrolyte was prepared according to the method of Example 1, except that monomer A and monomer B were not added, only monomer C was added, and the mass ratio of sulfide electrolyte to polyethylene glycol diacrylate was 9.5:0.5; the remaining steps were the same as in Example 1.

[0092] Comparative Example 2

[0093] The method of curing first and then mixing is adopted, which specifically includes the following steps:

[0094] Preparation of a polymer: Monomer A prepared in Preparation Example was mixed with diphenyl disulfide, polyethylene glycol diacrylate, and azobisisobutyronitrile in a molar ratio of 2:1:1:0.01 to obtain a mixture; 1 wt % of lithium bistrifluoromethylsulfonyl imide (LiTFSI) was added to the mixture, stirred for 30 minutes, and after mixing thoroughly, heated at 60°C for 4 hours for in-situ curing to obtain a polymer;

[0095] Preparation of composite sulfide electrolyte: sulfide electrolyte Li6PS5Cl was added to the polymer obtained by in-situ curing, wherein the mass ratio of sulfide electrolyte to polymer was 9.5:0.5. After thorough grinding and mixing, a powdered composite sulfide electrolyte was obtained.

[0096] The buckle pressure was prepared by cold pressing to obtain a composite sulfide electrolyte with a thickness of 200 μm.

[0097] Comparative Example 3

[0098] A composite sulfide electrolyte was prepared according to the method of Example 1, except that monomer A, monomer B, and monomer C were not added, and nitrile rubber was added, wherein the mass ratio of sulfide electrolyte to nitrile rubber was 9.8:0.2; the remaining steps were the same as in Example 1.

[0099] Comparative Example 4

[0100] Only conventional sulfide electrolyte Li6PS5Cl is used, of which Li6PS5Cl accounts for 100%. The buckle voltage is manufactured by cold pressing to obtain a sulfide electrolyte with a thickness of 200μm.

[0101] Application Example 1

[0102] Preparation of composite cathode materials:

[0103] (1) Weigh 1.4 g of nickel 83, 0.04 g of Super-P and 0.56 g of sulfide electrolyte Li6PS5Cl and mix them evenly to obtain a composite positive electrode material C1.

[0104] (2) Weigh 1.4 g of nickel 83, 0.04 g of Super-P and 0.56 g of the composite sulfide electrolyte prepared in Example 5, mix them evenly, and obtain a composite positive electrode material C2.

[0105] Preparation of composite negative electrode materials:

[0106] (1) Weigh 2 g of silicon negative electrode material and add it to a mixing tank, then add tetrahydrofuran and stir for 2 h to mix evenly to obtain an active material slurry with a solid content of 40-45%; use a doctor blade to coat the active material slurry on the negative electrode current collector copper foil, then bake at 60°C for 2 h and bake at 100°C until dry to obtain a composite negative electrode material A1.

[0107] (2) A composite negative electrode material was prepared according to the preparation method of composite negative electrode material A1, except that 2 g of the silicon negative electrode material was replaced by a mixture of 1.2 g of silicon negative electrode material and 0.8 g of the composite sulfide electrolyte prepared in Example 5 to obtain composite negative electrode material A2.

[0108] All-solid-state battery assembly method 1:

[0109] The composite sulfide electrolytes with a thickness of 200 μm prepared in Examples 1-4 and Comparative Examples 1-4 were cut to obtain small discs with a diameter of 10 mm. The composite positive electrode material C1 was pressed on one side of the small disc to obtain a composite positive electrode having a positive electrode active material loading density of 5 mg / cm 2 ; The negative electrode sheet A1 is attached to the other side of the small disc. After pressing, the assembled all-solid-state batteries are obtained, which are respectively recorded as batteries S1-S4 and batteries D1-D4. The compositions of each are shown in Table 1.

[0110] All-solid-state battery assembly method 2:

[0111] The method is the same as the all-solid-state battery assembly method 1, except that the non-in-situ cured composite sulfide electrolyte obtained in Example 5 is used when assembling the battery, and after the battery is pressed, it is heated at 60°C for 4 hours for in-situ curing to obtain the assembled battery S5, whose composition is shown in Table 1.

[0112] All-solid-state battery assembly method three:

[0113] The method is the same as the second method for assembling an all-solid-state battery, except that the composite positive electrode material C1 is replaced by the composite positive electrode material C2, and the composite negative electrode material A1 is replaced by the composite negative electrode material A2, to obtain an assembled battery S6, the composition of which is shown in Table 1.

[0114] Table 1

[0115] The electrochemical tests were performed on the assembled all-solid-state button batteries in Table 1. The test steps are as follows:

[0116] Battery charge and discharge settings: The test was performed using a NEWARE high-performance battery testing system; (1) the battery was charged at a constant current rate of 0.1C to 4.2V, and then discharged at a constant current rate of 0.1C to 2.7V, for two cycles; (2) the battery was charged at a constant current rate of 0.5C to 4.2V, and then discharged at a constant current rate of 0.5C to 2.7V; step (2) was repeated for cyclic charge and discharge tests (nominal specific capacity of the battery was 200mAh / g).

[0117] The cycle test results of the all-solid-state button battery are shown in Table 2.

[0118] Table 2

[0119] As can be seen from the data in Table 2, compared with the battery D1 assembled in Comparative Example 1, the cycle performance of the all-solid-state batteries S1-S6 assembled using the composite sulfide electrolyte obtained in Examples 1-5 as the electrolyte layer was significantly improved, indicating that the three-phase cross-linked structure obtained by linking the chemical bonds in the composite electrolyte of the present invention plays an effective role, has the characteristics of relieving internal stress, reducing the generation of cracks and interface delamination, and self-repairing. Compared with the all-solid-state batteries D2 and D3 assembled in Comparative Examples 2 and 3, the cycle performance of the all-solid-state batteries S1-S6 assembled using the composite sulfide electrolyte obtained in Examples 1-5 as the electrolyte layer was improved, indicating that the polymer and sulfide electrolyte in the composite electrolyte obtained by the in-situ curing method of the present invention are in close contact and uniformly distributed; compared with the all-solid-state battery D4 assembled in Comparative Example 4, the first-cycle efficiency of the all-solid-state battery S1 assembled using the composite sulfide electrolyte obtained in Example 1 as the electrolyte layer was 1-2% lower, and the magnitude of the decrease in the first-cycle discharge specific capacity was small, indicating that the ion transport of the composite sulfide electrolyte obtained in the present invention is slightly lower than that of the original sulfide electrolyte powder, but the cycle performance is significantly improved.

[0120] In Comparative Example 1, only monomer C was added, which greatly affected the ion conduction of the electrolyte layer, resulting in a decrease in the initial efficiency of the battery and a slight improvement in the cycle performance. In Comparative Example 2, monomer A, compound B, and monomer C were mixed and solidified to obtain solid particles, which increased the solid-solid contact interface of the particles in the composite electrolyte layer and hindered the ion transport of the electrolyte layer, resulting in a decrease in battery performance. Comparative Example 3 had obvious interface problems due to the solid-solid contact between the sulfide electrolyte particles. Under long-term cycling, there was a risk of capacity decay and lithium dendrite puncture.

[0121] Application Example 2

[0122] Limiting current density test symmetrical battery assembly:

[0123] The composite sulfide electrolyte prepared in Example 1 was cut into small discs with a diameter of 10 mm. Metal lithium with a thickness of 20 μm was attached to both sides of the small disc to obtain a symmetrical battery.

[0124] Limiting current density test: set the current density to 0.4 mA / cm 2 The long cycle test was carried out using a charge and discharge method with a charging time of 1 hour and a discharge time of 1 hour at the same current density.

[0125] Test results: The symmetrical cell assembled using the composite sulfide electrolyte prepared in Example 1 showed no obvious short circuit phenomenon after 100 cycles, while the symmetrical cell assembled using the conventional Li6PS5Cl electrolyte short circuited after 35 cycles. This indicates that the composite sulfide electrolyte prepared in the present invention can withstand higher current density in all-solid-state batteries and is expected to improve the rate performance of all-solid-state batteries.

[0126] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A composite sulfide electrolyte, characterized in that, The composite sulfide electrolyte contains a three-dimensional cross-linked structure formed by chemically bonding a sulfide electrolyte and a cross-linked polymer containing dynamic bonds.

2. The composite sulfide electrolyte according to claim 1, wherein The chemical bond is selected from at least one of P-N bond, S-C bond and S-S bond.

3. The composite sulfide electrolyte according to claim 1 or 2, wherein, The composite sulfide electrolyte is obtained by in-situ curing of a sulfide electrolyte with monomer A, monomer B, and optionally monomer C; wherein, monomer A is selected from one or more of the compounds having the structure shown in formula (1); monomer B is selected from one or more of the compounds containing amino groups and the compounds containing both amino groups and disulfide bonds; monomer C is selected from one or more of the compounds containing double bonds; In formula (1), R1 is a group containing a carbon-carbon double bond or a carbon-carbon triple bond.

4. The composite sulfide electrolyte according to any one of claims 1-3, wherein, The sulfide electrolyte is selected from one or more of sulfide electrolytes containing P=S bonds; Preferably, the sulfide electrolyte is selected from one or more of LiM1PSX1, LiPSX1, LiM2PS and lithium thiophosphate; wherein, M1 is selected from one or more of Ge, Si, Nb, Sb, Zn, Fe, Bi, Al, In, Cu, Ce and Sn; X1 is selected from one or more of Cl, Br, I, O, N; M2 is selected from one or more of Ge, Si, P, Sn, Al, As, Sb, Zn, Y and Ga.

5. The composite sulfide electrolyte according to claim 3, wherein, The monomer A is selected from one or more of the compounds having the structures shown in Formula A-1 to Formula A-17; Wherein, R is a hydrocarbon group with or without an alkyl side chain containing 1-9 carbon atoms; Z1 is hydrogen or methyl; Z2 is a saturated alkylene group containing 1-9 carbon atoms with or without an alkyl side chain.

6. The composite sulfide electrolyte according to claim 3, wherein, The monomer B is selected from one or more of n-hexylamine, polyethyleneimine, ethylenediamine, propanediamine, butanediamine, 2,5-diaminopentanoic acid, tris(2-aminoethyl)amine, 4,4'-dithiobis(aniline), 2,2'-dithiobis(diethylamine), 4,4'-dithiobis(2-aminobutyric acid), 3,3'-dithiobis(2-aminopropionic acid), dithioformamidine, 2-(2-amino-5-methoxyphenyl)dithio-4-methoxyaniline, and a substance having the structure shown in Formula B-1; preferably, the monomer B is selected from one or more of 4,4'-dithiobis(aniline), 2,2'-dithiobis(diethylamine), 4,4'-dithiobis(2-aminobutyric acid), 3,3'-dithiobis(2-aminopropionic acid), dithioformamidine, 2-(2-amino-5-methoxyphenyl)dithio-4-methoxyaniline, and a substance having the structure shown in Formula B-1; And / or, the monomer C is selected from one or more of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, diethylene glycol diacrylate and triethylene glycol diacrylate.

7. A method for preparing a composite sulfide electrolyte, characterized in that, The preparation method includes the following steps: Under polymerization reaction conditions, a sulfide electrolyte is in-situ cured with monomer A, monomer B and optional monomer C in an optional solvent; wherein, the monomer A is selected from one or more of the compounds having the structure shown in formula (1); the monomer B is selected from one or more of the compounds containing amino groups and the compounds containing both amino groups and disulfide bonds; the monomer C is selected from one or more of the compounds containing double bonds; In formula (1), R1 is a group containing a carbon-carbon double bond or a carbon-carbon triple bond.

8. The preparation method according to claim 7, wherein, The sulfide electrolyte is selected from one or more of sulfide electrolytes containing P=S bonds; And / or, the monomer B is selected from one or more of n-hexylamine, polyethyleneimine, ethylenediamine, propanediamine, butanediamine, 2,5-diaminopentanoic acid, tris(2-aminoethyl)amine, 4,4'-dithiobisbenzenamine, 2,2'-dithiobis(diethylamine), 4,4'-dithiobis(2-aminobutyric acid), 3,3'-dithiobis(2-aminopropionic acid), dithioformamidine, 2-(2-amino-5-methoxyphenyl)dithio-4-methoxyaniline, and the substance having the structure shown in formula B-1; preferably, the monomer B is selected from one or more of 4,4'-dithiobisbenzenamine, 2,2'-dithiobis(diethylamine), 4,4'-dithiobis(2-aminobutyric acid), 3,3'-dithiobis(2-aminopropionic acid), dithioformamidine, 2-(2-amino-5-methoxyphenyl)dithio-4-methoxyaniline, and the substance having the structure shown in formula B-1; And / or, the monomer C is selected from one or more of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, diethylene glycol diacrylate and triethylene glycol diacrylate; And / or, the solvent is selected from one or more of low-polarity solvents.

9. The preparation method according to claim 7 or 8, wherein The molar ratio of the monomer A, monomer B and monomer C is 1-5:0.5-5:0-4.5, preferably 1-2:1-3:0.5-1; And / or, the mass ratio of the sulfide electrolyte to the total mass of the monomer A, monomer B and monomer C is 5-9.8:0.2-5, preferably 7-9.8:0.2-3.

10. The preparation method according to any one of claims 7-9, wherein, The polymerization reaction conditions include: the temperature is 45-80 °C and the time is 1-24 h; And / or, the polymerization reaction conditions include: adding an initiator; the initiator is selected from one or more of azobisisobutyronitrile, benzoyl peroxide, azobisisoheptonitrile, ammonium persulfate and azobisisobutylimidazoline hydrochloride; And / or, the polymerization reaction conditions include: adding a lithium salt additive; the lithium salt additive is selected from one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide.

11. A composite sulfide electrolyte prepared by the preparation method according to any one of claims 7-10.

12. Use of the composite sulfide electrolyte according to any one of claims 1-6 and 11 in the preparation of an electrode or a battery.

13. An electrode, characterized in that, The electrode includes a positive electrode and / or a negative electrode, wherein the positive electrode includes a positive electrode active material and the composite sulfide electrolyte described in any one of claims 1-6 and 11; the negative electrode includes a negative electrode active material and the composite sulfide electrolyte described in any one of claims 1-6 and 11.

14. A all-solid-state battery, characterized in that, The all-solid-state battery includes a positive electrode, a negative electrode, and an electrolyte; wherein the electrolyte contains the composite sulfide electrolyte described in any one of claims 1-6 and 11.

15. The all-solid-state battery according to claim 14, wherein, The positive electrode includes a positive electrode active material and the composite sulfide electrolyte described in any one of claims 1-6 and 11; and / or, the negative electrode includes a negative electrode active material and the composite sulfide electrolyte described in any one of claims 1-6 and 11.

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