Composite sulfide electrolyte and preparation method and application thereof

Abstract

The invention discloses a composite sulfide electrolyte as well as a preparation method and application thereof. The composite sulfide electrolyte contains a three-dimensional cross-linked structure formed by connecting a sulfide electrolyte and a cross-linked polymer containing dynamic bonds through chemical bonds. The composite sulfide electrolyte provided by the invention contains a three-dimensional cross-linked structure formed by the sulfide electrolyte and the cross-linked polymer containing dynamic bonds through chemical bonds, and the polymer contains sulfur element, so that the polymer and the sulfide electrolyte are relatively stable; various chemical bonds form chemical cross-linking between the sulfide electrolyte and the cross-linked polymer containing the dynamic bonds, for example, disulfide bonds, amido bonds and the like are contained at the same time, strong binding force and a self-repairing function are achieved, and the problems of interface layering and cracking caused by internal mechanical stress of the sulfide electrolyte are expected to be solved at the same time. When the composite sulfide electrolyte is applied to the all-solid-state battery, the limiting current density and the cycling stability of the all-solid-state battery can be improved.

Description

Technical Field

[0001] The present invention relates to the field of solid electrolytes, and particularly to composite sulfide electrolytes, their preparation methods and applications. Background Art

[0002] Electrochemical energy storage is most widely applied in lithium-ion batteries and lead-acid batteries. Compared with lead-acid batteries, lithium-ion batteries have more advantages in specific energy, cycle life, and usage duration; currently, the commonly used batteries are liquid-phase batteries containing organic solvents, which are flammable and pose safety hazards. Using inorganic solid electrolytes instead of organic flammable electrolytes is an effective measure to solve this problem. Using inorganic solid electrolytes can effectively alleviate the lithium dendrite problem and improve the energy density. Sulfide electrolytes in inorganic solid electrolytes have received extensive attention due to their high ionic conductivity. However, there is an internal mechanical stress during the continuous lithium deintercalation and intercalation processes between the sulfide electrolyte solid electrolyte and the electrode material, resulting in interface delamination and cracks in the electrolyte layer, thereby causing battery attenuation or failure. Therefore, effective means need to be taken to alleviate this problem to improve the electrochemical performance of the battery.

[0003] Currently, most methods to alleviate the above problems are to introduce polymers into sulfide electrolytes or increase the polymer interface layer. An ideal sulfide-polymer composite electrolyte should have the mechanical flexibility of the polymer matrix, a strong interaction at the polymer / electrolyte interface to avoid delamination, a smaller electrolyte size to reduce fracture, and three-dimensional continuous channels to achieve high ionic conductivity. However, in the prior art, sulfide electrolytes and polymers are mainly compounded by physical mixing, and the resulting composite electrolytes still exhibit peeling phenomena during the long-term lithium deintercalation and intercalation processes, and cannot effectively solve the problems of cracks and interface peeling caused by internal mechanical stress.

[0004] CN112909322A discloses an in-situ formed sulfide composite solid electrolyte, including a polymer three-dimensional skeleton and an interpenetrating network structure formed with a sulfide electrolyte. The network structure formed by the sulfide electrolyte in this composite solid electrolyte serves as the main carrier of high ionic conductivity, and the in-situ formed polymer three-dimensional skeleton plays roles in supporting and strengthening, improving the interfacial ionic conductivity of the sulfide electrolyte, and increasing the flexibility of the electrolyte. However, in this composite solid electrolyte, the sulfide electrolyte and the polymer are physically mixed and do not involve chemical bond interactions, so the ability to improve cracks and interface delamination caused by internal mechanical stress is limited. Summary of the Invention

[0005] The object of the present invention is to overcome the problems such as cracks and interfacial delamination caused by internal mechanical stress in the prior art, and to provide a composite sulfide electrolyte, a preparation method and an application thereof. The composite sulfide electrolyte forms a chemical crosslinking between a sulfide electrolyte and a crosslinked polymer containing dynamic bonds through a variety of chemical bonds, and contains disulfide bonds and amide bonds at the same time, has strong binding force and has a self-healing function, and can effectively improve the interfacial delamination and cracks caused by internal mechanical stress during the cycling process of the electrolyte or electrolyte membrane, thereby improving the performance of the battery such as the limiting current density and cycling.

[0006] To achieve the above object, in the first aspect of the present invention, a composite sulfide electrolyte is provided, and the composite sulfide electrolyte contains a three-dimensional crosslinked structure formed by connecting a sulfide electrolyte and a crosslinked polymer containing dynamic bonds through chemical bonds.

[0007] In the second aspect of the present invention, a preparation method of a composite sulfide electrolyte is provided, and the preparation method includes the following steps:

[0008] Under polymerization reaction conditions, the sulfide electrolyte, monomer A, monomer B and optional monomer C are subjected to in-situ curing in an optional solvent D to obtain a composite sulfide electrolyte; wherein, the monomer A is selected from one or more of the compounds having the structure shown in formula I; the monomer B is selected from one or more of the compounds containing amino groups and / or the compounds containing both amino groups and disulfide bonds; the monomer C is selected from one or more of the compounds containing double bonds; the solvent D is selected from one or more of low-polarity solvents;

[0009]

[0010] In formula (1), R1 is a group containing a carbon-carbon double bond or a carbon-carbon triple bond.

[0011] In the third aspect of the present invention, an electrode is provided, which includes the composite sulfide electrolyte described in the first aspect or the composite sulfide electrolyte prepared by the preparation method described in the second aspect.

[0012] In the fourth aspect of the present invention, a all-solid-state battery is provided, and the all-solid-state battery includes the electrode described in the third aspect, the composite sulfide electrolyte described in the first aspect or the composite sulfide electrolyte prepared by the preparation method described in the second aspect.

[0013] Through the above technical solutions, the beneficial technical effects obtained by the present invention are as follows:

[0014] 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 sulfur element and is relatively more stable with the sulfide electrolyte. The sulfide electrolyte and the cross-linked polymer containing dynamic bonds form chemical cross-links through various chemical bonds such as P-N bonds and disulfide bonds, having strong binding force and self-healing function, and is expected to solve the problems of interfacial delamination and cracks caused by internal mechanical stress in the sulfide electrolyte at the same time.

[0015] 2) The method of the present invention adopts an in-situ reaction method. After forming the ionic conductive channels of the sulfide electrolyte, a polymer is in-situ cured in the voids of the sulfide electrolyte particles. On the basis of not affecting the ionic transport of the sulfide electrolyte, the porosity of the sulfide electrolyte is reduced to form a three-dimensional conductive network; and the sulfide electrolyte and the polymer are more uniformly distributed and in closer contact.

[0016] 3) The composite sulfide electrolyte of the present invention is applied to an all-solid-state battery, which can improve the limiting current density and cycle stability of the all-solid-state battery. Description of the Drawings

[0017] Figure 1 is the XPS data graph of the composite sulfide electrolyte prepared in Example 1 of the present invention;

[0018] Figure 2 is the infrared spectrum graph of the composite sulfide electrolyte prepared in Example 1 of the present invention. Detailed Embodiments

[0019] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0020] The first aspect of the present invention provides a composite sulfide electrolyte, and the composite sulfide electrolyte contains a three-dimensional cross-linked structure formed by chemical bonds between a sulfide electrolyte and a cross-linked polymer containing dynamic bonds.

[0021] In some embodiments of the present invention, the chemical bond contains at least one of P-N bond, S-C bond, and S-S bond, and preferably contains the above three chemical bonds at the same time.

[0022] In the present invention, the sulfide electrolyte and the cross-linked polymer containing dynamic bonds are chemically cross-linked through a variety of chemical bonds. The cross-linked polymer containing dynamic bonds contains S element, is relatively more stable with the sulfide electrolyte, and contains chemical bonds such as disulfide bonds and amide bonds, has strong binding force and has self-healing function, and is expected to solve the interface delamination and crack problems caused by internal mechanical stress in the sulfide electrolyte at the same time.

[0023] In some embodiments of the present invention, the composite sulfide electrolyte is obtained by in-situ curing of a sulfide electrolyte with monomer A, monomer B and optional monomer C; wherein, monomer A is selected from one or more of the compounds having the structure shown in formula I; monomer B is selected from one or more of the compounds containing amino groups and / or the compounds containing both amino groups and disulfide bonds; monomer C is selected from one or more of the compounds containing double bonds;

[0024]

[0025] In formula (1), R1 is a group containing a carbon-carbon double bond or a carbon-carbon triple bond.

[0026] In the present invention, monomer A is a compound containing both a sulfur lactone and a double bond or a triple bond, monomer B is selected from one or more of the compounds containing amino groups and / or the compounds containing both amino groups and disulfide bonds, and the monomers used undergo in-situ polymerization between the voids of the sulfide electrolyte particles to form a polymer; the formed polymer can react with the sulfide electrolyte, wherein the double bond or triple bond reacts with the sulfide electrolyte to form an S-C bond; the amino group undergoes nucleophilic addition with the P=S bond in the sulfide electrolyte to form a P-N bond; the amino group can also react and cross-link with the sulfur lactone, and the mercapto group generated by the ring-opening of the sulfur lactone is dehydrogenated by oxidation with the mercapto group in the sulfide electrolyte during the heating and drying process to form an S-S bond; the chemical bonds formed above ensure a strong connection force between the sulfide electrolyte and the polymer, and both the S-S bond and the amide bond have self-healing functions.

[0027] In some embodiments of the present invention, the sulfide electrolyte is selected from one or more of the sulfide electrolytes containing P=S bonds.

[0028] In some preferred embodiments of the present invention, the sulfide electrolyte is selected from one or more of LiM1PSX1, 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.

[0029] 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 or one or more of them.

[0030] In some embodiments of the present invention, the monomer A is selected from one or more of the compounds having the structures shown in Formula A-1 to Formula A-17;

[0031]

[0032]

[0033] 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 with or without an alkyl side chain containing 1-9 carbon atoms.

[0034] In some embodiments of the present invention, 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(ethylamine), 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;

[0035]

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

[0037] In the reaction of the present invention, the monomer C can be optionally added 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 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;

[0039] And / or, the mass ratio of the sulfide electrolyte to monomers A, B, and 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 selected from at least one of iron sulfide, iron(II) sulfide, lithium iron phosphate, lithium cobaltate, lithium manganate, lithium titanate, ternary materials, and their modified materials.

[0041] In the present invention, the negative electrode active material is selected from at least one 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, azodiisooctanenitrile, ammonium persulfate, and azobisisobutylimidazoline hydrochloride.

[0043] In the present invention, a lithium salt additive such as lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, etc. can also be added during the preparation process to further enhance the lithium ion conduction of the composite electrolyte.

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

[0045] Under polymerization reaction conditions, in-situ curing of the sulfide electrolyte with monomers A, B, and optionally monomer C in an optional solvent D is carried out to obtain a composite sulfide electrolyte; wherein, monomer A is selected from one or more of the compounds having the structure shown in formula I; monomer B is selected from one or more of the compounds containing an amino group and / or the compounds containing both an amino group and a disulfide bond; monomer C is selected from one or more of the compounds containing a double bond; the solvent D is selected from one or more of low-polarity solvents;

[0046]

[0047] In formula (1), R1 is a group containing a carbon-carbon double bond or a carbon-carbon triple bond.

[0048] In the present invention, this preparation method uses the sulfide electrolyte as the main body to carry out in-situ curing with monomers A, B, and optionally monomer C in an optional solvent D in the presence of an initiator to obtain a composite sulfide electrolyte.

[0049] In some embodiments of the present invention, the sulfide electrolyte is selected from one or more of the sulfide electrolytes containing a P=S bond.

[0050] In some embodiments of the present invention, the monomer A is selected from one or more of the compounds having the structures shown in Formula A-1 to Formula A-17.

[0051] In some embodiments of the present invention, 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(ethylamine), 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.

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

[0053] In the present invention, the specific selections of the sulfide electrolyte, monomer A, monomer B, and monomer C are the same as those in the aforementioned first aspect. For specific reference, see the previous description and will not be elaborated here.

[0054] In the present invention, the positive electrode active material used is selected from at least one of iron sulfide, iron sulfide, lithium iron phosphate, lithium cobaltate, lithium manganate, lithium titanate, ternary materials, and their modified materials.

[0055] In the present invention, the negative electrode active material used is selected from at least one of graphite, elemental silicon, silicon oxide, silicon monoxide, transition metal oxides, transition metal sulfides, transition metal phosphides, and silicon carbide.

[0056] In the present invention, the solvent D is selected from one or more of low-polarity solvents. The low-polarity solvents include, but are not limited to, tetrahydrofuran, ether solvents, alkane solvents, ester solvents, etc. The addition amount of the solvent D is 0-50%.

[0057] In the present invention, a lithium salt additive such as lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, etc. is added during the preparation process to further improve the lithium ion conduction of the composite electrolyte.

[0058] In some embodiments of the present invention, 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.

[0059] 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.

[0060] In the present invention, if the number of amino groups contained in monomer B decreases or the addition amount of monomer B is too small, it will lead to: 1) a decrease in the number of P-N bonds formed with the electrolyte; 2) a decrease in the number of ring openings of thiolactone, resulting in a decrease in the number of -S-S- bonds formed and a decline in the self-healing performance, and the battery cycle performance deteriorates; on the contrary, the cycle performance is improved. If the addition amount of monomer C is further increased, the ionic conductivity of the composite electrolyte becomes better, the flexibility of the electrode sheet is enhanced, and the battery cycle performance is improved.

[0061] In some embodiments of the present invention, the polymerization reaction conditions include: in the presence of an initiator, the reaction temperature is 45 - 80 °C, and the reaction time is 1 - 24 h.

[0062] In the present invention, the conditions for in-situ curing are the same as those for the polymerization reaction.

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

[0064] The third aspect of the present invention provides an electrode, which includes the composite sulfide electrolyte described in the first aspect above or the composite sulfide electrolyte prepared by the preparation method described in the second aspect.

[0065] In the present invention, the electrode is a positive electrode and / or a negative electrode.

[0066] The present invention also provides the application of the composite sulfide electrolyte described in the first aspect or the third aspect above in a battery, especially in a all-solid-state battery.

[0067] The fourth aspect of the present invention provides a all-solid-state battery, which includes the electrode described in the third aspect above, the composite sulfide electrolyte described in the first aspect above or the composite sulfide electrolyte prepared by the preparation method described in the second aspect.

[0068] When the composite sulfide electrolyte of the present invention is applied in a all-solid-state battery, it can improve the limiting current density and cycle stability of the all-solid-state battery.

[0069] The present invention will be described in detail below through examples.

[0070] In the following examples and comparative examples, without special instructions, various initial raw materials used are commercially available.

[0071] Preparation Example

[0072] Preparation of monomer A: Dissolve 9.2 g (0.06 mol) of DL-homocysteine thiolactone hydrochloride and 24 g (2.37 mol) of triethylamine in 900 mL of dichloromethane, stir and dissolve in an ice-water bath, slowly add dropwise 9.06 g (0.1 mol) of acryloyl chloride, control the temperature not exceeding 0 °C, and react for 5 h; Wash the organic phase after the reaction 3 times with saturated brine, and dry it with anhydrous sodium sulfate. After filtration, concentrate the filtrate under reduced pressure. Dissolve the residue in 180 mL of ethyl acetate, filter through a short silica column, and recrystallize the filtrate with petroleum ether, then filter to obtain monomer A.

[0073] Test example

[0074] Preparation of polymer mixture: Mix monomer A prepared in the preparation example with n-hexylamine, polyethylene glycol diacrylate and azobisisobutyronitrile in a molar ratio of 2:1:1:0.01 to obtain a mixture; Add 1 wt% of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to this mixture, stir for 30 min, and after mixing evenly, obtain a polymer mixture;

[0075] Preparation of composite sulfide electrolyte: Add sulfide electrolyte Li6PS5Cl to the above polymer mixture, where the mass ratio of the sulfide electrolyte to the polymer mixture is 9.5:0.5, then add the solvent tetrahydrofuran, and the solid content is 50 wt%. Stir for 30 min, after sufficient infiltration, use a scraping method to coat on a polytetrafluoroethylene substrate, and heat at 60 °C for 4 h for in-situ curing to obtain a composite sulfide electrolyte with a thickness of 200 μm.

[0076] XPS data graph of the composite sulfide electrolyte prepared in the test example of the present invention, from Figure 1 It can be seen that there is an obvious peak of P-N bond, which is impossible for the original electrolyte Li6PS5Cl to have, indicating that cross-linking is successfully generated between the sulfide electrolyte and the polymer.

[0077] Infrared spectrum of the composite sulfide electrolyte prepared in the test example of the present invention, as Figure 2 shown, from Figure 2 it can be seen that the peak appearing at 2570 cm -1 of this composite sulfide electrolyte proves the formation of disulfide bonds in the final product.

[0078] Example 1

[0079] Preparation of polymer mixture: Mix monomer A prepared in the preparation example with diphenyl disulfideamine, polyethylene glycol diacrylate and azobisisobutyronitrile in a molar ratio of 2:1:1:0.01 to obtain a mixture; Add 1 wt% of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to this mixture, stir for 30 min, and after mixing evenly, obtain a polymer mixture;

[0080] Preparation of composite sulfide electrolyte: Add sulfide electrolyte Li6PS5Cl to the above polymer mixture. Among them, the mass ratio of sulfide electrolyte to polymer mixture is 9.5:0.5. Then add solvent tetrahydrofuran, and the solid content is 50 wt%. Stir for 30 min. After full infiltration, use a doctor blade coating method to coat on a polytetrafluoroethylene substrate, and heat at 60 °C for 4 h for in-situ curing to obtain a composite sulfide electrolyte with a thickness of 200 μm.

[0081] Example 2

[0082] Prepare the composite sulfide electrolyte according to the method of Example 1, except that the sulfide electrolyte is Li3PS4; the remaining steps are the same as those in Example 1.

[0083] Example 3

[0084] Prepare the composite sulfide electrolyte according to the method of Example 1, except that the monomer A prepared in the preparation example is mixed with diphenyldisulfideamine, polyethylene glycol diacrylate and azobisisobutyronitrile in a molar ratio of 2:1:0.5:0.01 to obtain a mixture; the remaining steps are the same as those in Example 1.

[0085] Example 4

[0086] Prepare the composite sulfide electrolyte according to the method of Example 1, except that the monomer A prepared in the preparation example is mixed with diphenyldisulfideamine, polyethylene glycol diacrylate and azobisisobutyronitrile in a molar ratio of 2:1:2:0.01 to obtain a mixture; the remaining steps are the same as those in Example 1.

[0087] Example 5

[0088] Prepare the composite sulfide electrolyte according to the method of Example 1, except that the coated electrolyte membrane is allowed to stand at room temperature for 24 h in an argon atmosphere to obtain a composite sulfide electrolyte with a thickness of 200 μm.

[0089] Comparative Example 1

[0090] Prepare the composite sulfide electrolyte according to the method of Example 1, except that monomer A and monomer B are not added, and only monomer C is added, and the mass ratio of sulfide electrolyte to polyethylene glycol diacrylate is 9.5:0.5; the remaining steps are the same as those in Example 1.

[0091] Comparative Example 2

[0092] Adopt the method of curing first and then mixing, which specifically includes the following steps:

[0093] Preparation of polymer: Monomer A obtained in the 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 bis(trifluoromethanesulfonyl)imide (LiTFSI) was added to the mixture, and the mixture was stirred for 30 min. After being uniformly mixed, it was heated at 60 °C for 4 h for in-situ curing to obtain a polymer;

[0094] Preparation of composite sulfide electrolyte: Sulfide electrolyte Li6PS5Cl was added to the polymer obtained by the above in-situ curing. Among them, the mass ratio of the sulfide electrolyte to the polymer was 9.5:0.5. After being sufficiently ground and mixed, a powdery composite sulfide electrolyte was obtained.

[0095] The composite sulfide electrolyte with a thickness of 200 μm was obtained by cold pressing.

[0096] Comparative Example 3

[0097] The 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. Among them, the mass ratio of the sulfide electrolyte to the nitrile rubber was 9.8:0.2; the remaining steps were the same as those in Example 1.

[0098] Comparative Example 4

[0099] Only the conventional sulfide electrolyte Li6PS5Cl was used, in which the proportion of Li6PS5Cl was 100%. The sulfide electrolyte with a thickness of 200 μm was obtained by cold pressing.

[0100] Application Example 1

[0101] Preparation of composite cathode material:

[0102] (1) Weigh 1.4 g of nickel 83, 0.04 g of Super-P, and 0.56 g of sulfide electrolyte, and mix them evenly to obtain cathode material C1.

[0103] (2) The composite cathode was prepared according to the preparation method of cathode material C1, except that 0.56 g of the composite sulfide electrolyte prepared in Example 5 was used, denoted as cathode material C2.

[0104] Preparation of composite anode material:

[0105] (1) Weigh 2 g of silicon anode material and add it to a stirring 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%; using a doctor blade coating, the active material slurry was coated on the anode current collector copper foil, and then baked at 60 °C for 2 h and baked to dryness at 100 °C to obtain anode material A1.

[0106] (2) Prepare the composite negative electrode according to the preparation method of the composite negative electrode A1, except that the silicon negative electrode material used is the mixed material, and the mixing method is: weigh 1.2 g of the silicon negative electrode material and 0.8 g of the composite sulfide electrolyte prepared in Example 5, and mix evenly to obtain the composite negative electrode, denoted as negative electrode material A2.

[0107] Full solid-state battery assembly method 1:

[0108] Cut the composite sulfide electrolytes with a thickness of 200 μm prepared in Examples 1-4 and Comparative Examples 1-3 respectively to obtain small round pieces with a diameter of 10 mm; press the composite positive electrode material C1 on one side of the small round piece to obtain the composite positive electrode, and the loading surface density of the positive electrode active material is 5 mg / cm 2 ; Stick the negative electrode sheet A1 on the other side of the small round piece, and after pressing, obtain the assembled full solid-state battery, denoted as batteries S1-S4 and batteries D1-D3 respectively, and the compositions are shown in Table 1.

[0109] Full solid-state battery assembly method 2:

[0110] The same as the full solid-state battery assembly method 1, the difference is 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 h for in-situ curing to obtain the assembled battery S6, and its composition is shown in Table 1.

[0111] Full solid-state battery assembly method 3:

[0112] The same as the full solid-state battery assembly method 2, the difference is that the positive electrode used is C2 and the negative electrode used is A2.

[0113] Table 1

[0114]

[0115] Perform electrochemical tests on the assembled full solid-state button cells in Table 1 above respectively, and the test steps are as follows:

[0116] Battery charge and discharge settings: Use the NEWARE high-performance battery detection system for testing; (1) Charge at a constant current rate of 0.1C to 4.2V, and then discharge at a constant current rate of 0.1C to 2.7V for 2 cycles; (2) Charge at a constant current rate of 0.5C to 4.2V, and then discharge at a constant current rate of 0.5C to 2.7V; Repeat step (2) for cyclic charge and discharge testing (the nominal specific capacity of the battery is 200 mAh / g).

[0117] The cyclic test results of the full solid-state button cells are shown in Table 2.

[0118] Table 2

[0119]

[0120]

[0121] It can be seen from the data in Table 2 that, compared with the battery D1 assembled in Comparative Example 1, the cycle performance of the all-solid-state batteries S1-S6 assembled with the composite sulfide electrolyte obtained in Examples 1-5 as the electrolyte layer has been significantly improved, indicating that the composite electrolyte of the present invention has the characteristic of self-healing. 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 with the composite sulfide electrolyte obtained in Examples 1-5 as the electrolyte layer is improved, indicating that the polymer and the sulfide electrolyte in the composite electrolyte obtained by the in-situ curing method of the present invention are in close contact and evenly distributed; compared with the all-solid-state battery D4 assembled in Comparative Example 4, the first-week efficiency of the all-solid-state battery S1 assembled with the composite sulfide electrolyte obtained in Example 1 as the electrolyte layer differs by 1-2%, and the decrease in the first-week discharge specific capacity is 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.

[0122] In Comparative Example 1, only monomer C was added, and this monomer filled the voids of the sulfide electrolyte. While improving the flexibility of the electrolyte layer, it 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 cured to obtain solid particles, which were ground with the sulfide electrolyte, increasing the solid-solid contact interface of the electrolyte layer and at the same time hindering the ion transport of the electrolyte layer, resulting in a decrease in battery performance. Comparative Example 3 is a battery with a pure sulfide electrolyte layer. It has a high initial performance but poor cycling performance. The reason is the high ionic conductivity of the sulfide electrolyte itself. However, there are obvious interface problems due to the solid-solid contact between the sulfide electrolyte particles. During long-term cycling, the capacity decays and there is a risk of lithium dendrite piercing.

[0123] Application Example 2

[0124] Assembly of a symmetric battery for testing the limiting current density:

[0125] The composite sulfide electrolyte prepared in Example 1 was cut into small round pieces with a diameter of 10 mm, and metallic lithium with a thickness of 20 μm was pasted on both sides of the small round pieces to obtain a symmetric battery.

[0126] Limiting current density test: Set the current density to 0.4 mA / cm 2 , and a long-term cycling test was carried out using a charge-discharge method with a charging time of 1 h and a discharge time of 1 h at the same current density.

[0127] Test results: No obvious short - circuit phenomenon was found in the symmetric battery assembled with the composite sulfide electrolyte prepared in Example 1 after 100 cycles, while the symmetric battery assembled with the conventional Li6PS5Cl electrolyte short - circuited after 35 cycles. This shows that the composite sulfide electrolyte prepared by the present invention can withstand a higher current density in all - solid - state batteries and is expected to improve the rate performance of all - solid - state batteries.

[0128] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

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

2. The composite solid electrolyte according to claim 1, wherein, The chemical bond contains 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 optional monomer C; wherein, monomer A is selected from one or more of the compounds having the structure shown in Formula I; monomer B is selected from one or more of the compounds containing amino groups and / or 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 the sulfide electrolytes containing P=S bonds. Preferably, the sulfide electrolyte is selected from one or more of LiM1PSX1, 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, and 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 4, wherein, 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 with or without an alkyl side chain containing 1-9 carbon atoms.

6. The composite sulfide electrolyte according to claim 3, wherein, 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'-dithiobis(aniline), 2,2'-dithiobis(ethylamine), 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, monomer C is preferably 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, in-situ curing of a sulfide electrolyte with monomer A, monomer B, and optional monomer C in optional solvent D to obtain a composite sulfide electrolyte; wherein, monomer A is selected from one or more of the compounds having the structure shown in Formula I; monomer B is selected from one or more of the compounds containing amino groups and / or the compounds containing both amino groups and disulfide bonds; monomer C is selected from one or more of the compounds containing double bonds; solvent D is selected from one or more of low-polarity solvents; 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 the sulfide electrolytes containing P=S bonds. And / or, 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'-dithiobis(aniline), 2,2'-dithiobis(ethylamine), 4,4'-dithiobis(2-aminobutyric acid), 3,3'-dithiobis(2-aminopropionic acid), dithioformamidine, 2-(2-amino-5-methoxyphenyl)dithio-4-methoxyaniline, and the substance with the structure shown in formula B-1; And / or, the monomer C is preferably selected from one or more of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, diethylene glycol diacrylate, and triethylene glycol diacrylate; And / or, the solvent D 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. An electrode, characterized in that, Comprising the composite sulfide electrolyte according to any one of claims 1-6 or the composite sulfide electrolyte prepared by the preparation method according to any one of claims 7-9, as the positive electrode and / or negative electrode.

11. A all-solid-state battery, characterized in that, The all-solid-state battery comprises at least one of the electrode according to claim 10, the composite sulfide electrolyte according to any one of claims 1-6, or the composite sulfide electrolyte prepared by the preparation method according to any one of claims 7-9.

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