Gel electrolyte, solid electrolyte membrane, and all-solid-state battery

Abstract

The application provides a gel electrolyte, a solid electrolyte membrane and a full solid-state battery. The gel electrolyte comprises a base and a lithium salt dispersed in the base. The base has ether oxygen groups, and hydrogen atoms on adjacent carbon atoms of the ether oxygen groups are partially substituted. The gel electrolyte can effectively avoid reaction with a sulfide solid-state electrolyte, can ensure excellent ion transmission capacity, and has good compatibility with the chemical structure of the sulfide solid-state electrolyte, thereby improving the electrochemical performance of the sulfide solid-state battery. Meanwhile, the base has a specific chemical structure, which can better adapt to the volume change of the electrode material. In addition, the gel electrolyte is a flexible electrolyte, can fill pores, act as an interface buffer layer, reduce interface impedance, and further improve the electrochemical performance of the sulfide solid-state battery.

Description

Technical Field

[0001] This application relates to the field of electrolytes, and more specifically, to a gel electrolyte, a solid electrolyte membrane, and an all-solid-state battery. Background Technology

[0002] As one of the main development directions of new energy technologies, sulfide solid-state batteries have shown great potential due to their superior performance. Compared with traditional lithium-ion batteries, sulfide solid-state batteries have significant improvements in safety, energy density, and cycle life. However, the technological development of sulfide solid-state batteries also faces some challenges, such as the interface problem between the electrolyte and the positive and negative electrodes, and the air stability of the sulfide solid electrolyte itself.

[0003] Gel electrolytes are electrolyte materials made from polymer matrices, salts, and solvents. They combine the excellent properties of both all-solid-state electrolytes and traditional liquid electrolytes, effectively improving the mechanical stability, conductivity, and safety of batteries. Gel electrolytes offer a potential solution to the challenges of sulfide solid-state batteries. On one hand, gel electrolytes can combine with sulfide solid-state electrolytes through covalent bonds to form a stable electrolyte structure, thereby improving the battery's mechanical stability and cycle life. On the other hand, gel electrolytes can effectively reduce solid-solid interface impedance.

[0004] In view of the above, this application is hereby submitted. Summary of the Invention

[0005] The main objective of this application is to provide a gel electrolyte, a solid electrolyte membrane, and an all-solid-state battery to solve the problems of high interfacial impedance and poor ion conductivity in existing sulfide solid-state batteries.

[0006] To achieve the above objectives, according to the first aspect of this application, a gel electrolyte is provided, comprising a matrix and a lithium salt dispersed in the matrix, the matrix having a structure as shown in Formula I, and the molecular weight of the matrix being 500~800 g / mol.

[0007] Formula I

[0008] Wherein, R is at least one of methyl or ethyl, R1 is a nonpolar group, R2 is selected from C4 to C10 alkyl groups, m is an integer between 4 and 18, and n is an integer between 2 and 9.

[0009] Furthermore, the molecular weight of the matrix is ​​500~750 g / mol.

[0010] Furthermore, the molecular weight of the matrix is ​​600~700 g / mol.

[0011] Furthermore, R2 is selected from C4 to C8 alkyl groups.

[0012] Furthermore, R2 is selected from C6-C8 alkyl groups.

[0013] Furthermore, m is an integer between 5 and 15, and n is an integer between 3 and 8.

[0014] Further, R1 is selected from at least one of methyl, ethyl, phenyl, benzyl, phenethyl, and C1-C2 haloalkyl groups; wherein, R1 is a C y H 2y+1 X is a haloalkyl group, wherein y is an integer between 1 and 2, and preferably X is selected from at least one of F, Cl, Br, and I.

[0015] Furthermore, the matrix is ​​selected from at least one having the structure shown in formula (A1), formula (A2), and formula (A3):

[0016] Formula (A1);

[0017] Formula (A2);

[0018] Formula (A3).

[0019] Furthermore, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, and lithium bisfluoroamideimide.

[0020] Furthermore, the mass ratio of the matrix to the lithium salt is 1:(0.18~0.50).

[0021] Furthermore, the mass ratio of the matrix to the lithium salt is 1:(0.22~0.43).

[0022] To achieve the above objectives, according to a second aspect of this application, a solid electrolyte membrane is provided, the raw materials of which include a sulfide solid electrolyte, a binder, and a gel electrolyte, wherein the gel electrolyte is the gel electrolyte provided in the first aspect of this application.

[0023] Furthermore, the preparation method of the solid electrolyte membrane includes: mixing a sulfide solid electrolyte, a binder, a gel electrolyte and an organic solvent to obtain a mixed slurry, coating the mixed slurry on a current collector, and removing the organic solvent to obtain a solid electrolyte membrane.

[0024] Furthermore, the sulfide solid electrolyte is selected from Li6PS5Cl, Li6PS5Br, Li6PS5I, and Li7P3S. 11 At least one of them.

[0025] Furthermore, the adhesive is selected from at least one of polyvinylidene fluoride hexafluoropropylene, nitrile rubber, styrene-butadiene rubber, and hydrogenated nitrile rubber.

[0026] Furthermore, the organic solvent is selected from at least one of isobutyl isobutyrate, butyl acetate, butyl butyrate, and isoamyl isovalerate.

[0027] Furthermore, the mass ratio of the sulfide solid electrolyte, binder, and gel electrolyte is (8~10):(0.1~1):(0.1~0.5).

[0028] Furthermore, the solid content of the mixed slurry is 50~55wt%.

[0029] According to a third aspect of this application, a sulfide all-solid-state battery is provided, the sulfide all-solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte membrane, wherein the solid electrolyte membrane is the solid electrolyte membrane provided in the second aspect of this application.

[0030] Furthermore, the mass of the gel electrolyte in the solid electrolyte membrane accounts for 1 to 5% of the total mass of the solid electrolyte membrane.

[0031] Furthermore, the mass of the gel electrolyte in the solid electrolyte membrane accounts for 2-3% of the total mass of the solid electrolyte membrane.

[0032] The gel electrolyte provided in this application comprises a matrix and a lithium salt dispersed in the matrix. The matrix contains etheroxy groups, and by partially substituting hydrogen atoms on the adjacent carbon atoms of the etheroxy groups, the reaction between the gel electrolyte and the sulfide solid electrolyte can be effectively avoided, while ensuring excellent ion transport capabilities. Furthermore, the chemical structure of the matrix has good compatibility with the sulfide solid electrolyte, thereby improving the electrochemical performance of the sulfide solid battery. Simultaneously, the specific chemical structure of the matrix allows it to better adapt to changes in electrode material volume. In addition, the gel electrolyte provided in this application is a flexible electrolyte and can also act as an interfacial buffer layer by filling pores, reducing interfacial impedance and further improving the electrochemical performance of the sulfide solid battery.

[0033] In addition, the gel electrolyte provided in this application is less prone to leakage and has better thermal stability compared to traditional liquid electrolytes. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0035] In this specification, the expression for C1 to C10 alkyl groups indicates that the group has 1 to 10 carbon atoms. Unless otherwise specified, this number of carbon atoms generally does not include the number of carbon atoms of substituents. When describing C1 to C10, it includes, but is not limited to, C1, C2, C3, C4, C5, C6, C7, C8, C9, and C10, etc. Other numerical ranges are not elaborated. In this specification, C6 to C8 aromatic groups refer to monocyclic or fused polycyclic aromatic hydrocarbons derived from aromatic hydrocarbons, including phenyl, benzyl, and biphenyl. In this specification, "C1 to C2 haloalkyl" refers to alkyl groups substituted with one or more halogen atoms, especially C1 to C2 fluoroalkyl or C1 to C2 chloroalkyl.

[0036] As described in the background section of this application, existing technologies suffer from high interfacial impedance and poor ion conductivity in sulfide solid-state batteries. To address these issues, this application provides a gel electrolyte, a solid electrolyte membrane, and an all-solid-state battery.

[0037] In a first typical embodiment of this application, a gel electrolyte is provided, comprising a matrix and a lithium salt dispersed in the matrix. The matrix has a structure as shown in Formula I, and the molecular weight of the matrix is ​​500-800 g / mol.

[0038] Formula I

[0039] Wherein, R is at least one of methyl or ethyl, R1 is a nonpolar group, R2 is selected from C4 to C10 alkyl groups, m is an integer between 4 and 18, and n is an integer between 2 and 9.

[0040] The gel electrolyte provided in this application comprises a matrix and a lithium salt dispersed in the matrix. The matrix contains etheroxy groups, and by partially substituting hydrogen atoms on the adjacent carbon atoms of the etheroxy groups, the reaction between the gel electrolyte and the sulfide solid electrolyte can be effectively avoided, while ensuring excellent ion transport capabilities. Furthermore, the chemical structure of the matrix has good compatibility with the sulfide solid electrolyte, thereby improving the electrochemical performance of the sulfide solid battery. Simultaneously, the specific chemical structure of the matrix allows it to better adapt to changes in electrode material volume. In addition, the gel electrolyte provided in this application is a flexible electrolyte and can also act as an interfacial buffer layer by filling pores, reducing interfacial impedance and further improving the electrochemical performance of the sulfide solid battery.

[0041] In addition, the gel electrolyte provided in this application is less prone to leakage and has better thermal stability compared to traditional liquid electrolytes.

[0042] Specifically, the molecular weight of the matrix is ​​any value or a range between any two of 500 g / mol, 550 g / mol, 600 g / mol, 650 g / mol, 700 g / mol, 750 g / mol, and 800 g / mol; m is 4, 6, 8, 10, 12, 14, 16, and 18; and n is 2, 3, 4, 5, 6, 7, 8, and 9.

[0043] In this application, a nonpolar group refers to an atomic group in a molecule with a uniform charge distribution and a dipole moment of zero or very low. Nonpolar groups include methyl, ethyl, propyl, phenyl, benzyl, phenethyl, vinyl, and haloalkyl groups.

[0044] In some embodiments, the molecular weight of the matrix is ​​500-750 g / mol, preferably 600-700 g / mol. By limiting the molecular weight of the matrix, the fluidity and flexibility of the gel electrolyte can be further improved, which is beneficial to improving interfacial contact, further reducing interfacial impedance, and thus improving the electrochemical performance of sulfide all-solid-state batteries.

[0045] To further optimize the matrix structure and improve the compatibility and ionic conductivity of the gel electrolyte, in some embodiments, R2 is selected from C4-C8 alkyl groups, preferably C6-C8 alkyl groups.

[0046] In some embodiments, m is an integer between 5 and 15, and n is an integer between 3 and 8. Further limiting m and n is beneficial for optimizing the compatibility of the matrix structure.

[0047] To further improve the fluidity and flexibility of the matrix structure and suppress adverse reactions, thereby better adapting to changes in electrode material volume, in some embodiments, R1 is selected from at least one of methyl, ethyl, phenyl, benzyl, phenethyl, and C1-C2 haloalkyl groups; wherein, R1 is a C y H 2y+1 X is a haloalkyl group, wherein y is an integer between 1 and 2, and preferably X is selected from at least one of F, Cl, Br, and I.

[0048] In some specific embodiments, the substrate is selected from at least one having the structure shown in formula (A1), formula (A2), and formula (A3):

[0049] Formula (A1);

[0050] Formula (A2);

[0051] Formula (A3);

[0052] The matrix having the structures shown in formulas (A1), (A2), and (A3) has an etheroxy group. By partially substituting hydrogen atoms on the adjacent carbon atoms of the etheroxy group in the matrix, the reaction between the gel electrolyte and the sulfide solid electrolyte can be effectively avoided, while ensuring excellent ion transport capability. Furthermore, the chemical structure of the matrix has good compatibility with the sulfide solid electrolyte, thereby improving the electrochemical performance of the sulfide solid battery.

[0053] In some embodiments, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluorooxalate borate (LiODFB), and lithium bisfluoroamide imide (LiFSI). The lithium salt can further enhance ion conductivity, improve interfacial contact, and reduce interfacial impedance.

[0054] In this application, the preparation method of the gel electrolyte includes: mixing and stirring a matrix and a lithium salt to obtain a gel electrolyte, wherein the stirring speed is 100~300 rpm and the stirring time is 6~10 h. The preparation method of the gel electrolyte is simple and has strong practicality in industrial production. Specifically, the stirring speed is any value or a range between 100 rpm, 150 rpm, 200 rpm, 250 rpm, and 300 rpm; the stirring time is any value or a range between 6 h, 7 h, 8 h, 9 h, and 10 h.

[0055] In some embodiments, the mass ratio of the matrix to the lithium salt is 1:(0.18~0.50), and in some preferred embodiments, the mass ratio is 1:(0.22~0.43). By further limiting the mass of the matrix and the lithium salt, the matrix and the lithium salt can be better mixed to obtain a gel electrolyte. Specifically, the mass ratio of the matrix to the lithium salt is any value or a range between any two of 1:0.18, 1:0.2, 1:0.22, 1:0.24, 1:0.26, 1:0.28, 1:0.30, 1:0.32, 1:0.34, 1:0.36, 1:0.38, 1:0.40, 1:0.43, 1:0.44, 1:0.46, 1:0.48, and 1:0.50.

[0056] In a second typical embodiment of this application, a solid electrolyte membrane is provided. The raw materials of the solid electrolyte membrane include a sulfide solid electrolyte, a binder, and a gel electrolyte, wherein the gel electrolyte is the gel electrolyte provided in the first typical embodiment of this application.

[0057] The gel electrolyte provided in this application comprises a matrix and a lithium salt dispersed in the matrix. The etheroxy groups in the matrix, due to the partial substitution of hydrogen atoms on adjacent carbon atoms, effectively prevent the gel electrolyte from reacting with the sulfide solid electrolyte while ensuring excellent ion transport capabilities. Furthermore, the matrix structure exhibits good compatibility with the sulfide solid electrolyte, thereby improving the electrochemical performance of the sulfide solid battery. Simultaneously, the specific structure of the matrix allows it to better adapt to changes in electrode material volume. This flexible gel electrolyte can fill pores, acting as an interfacial buffer layer to reduce interfacial impedance, thus improving the electrochemical performance of the sulfide solid battery.

[0058] In some embodiments, the method for preparing a solid electrolyte membrane includes: mixing a sulfide solid electrolyte, a binder, a gel electrolyte, and an organic solvent to obtain a mixed slurry; coating the mixed slurry onto a current collector; and removing the organic solvent to obtain a solid electrolyte membrane. The solid electrolyte membrane prepared by this method is beneficial for improving the interfacial compatibility of the solid electrolyte membrane, and the process is simple and suitable for industrial production.

[0059] In this application, the mixed slurry is coated onto a current collector with a doctor blade moving at a speed of 20–70 mm / min and a height of 150–250 μm. After coating, the slurry is placed in a vacuum oven for drying at a temperature of 80–120 °C for 6–10 h. Further limiting the doctor blade speed and height, as well as the drying temperature and time, improves the coating effect and allows the mixed slurry to better form a solid electrolyte membrane. Specifically, the scraper moving speed is any value or a range between any two of 20 mm / min, 30 mm / min, 40 mm / min, 50 mm / min, 60 mm / min, and 70 mm / min; the scraper height is any value or a range between any two of 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, and 250 μm; the drying temperature is any value or a range between any two of 80℃, 90℃, 100℃, 110℃, and 120℃; and the drying time is any value or a range between any two of 6h, 7h, 8h, 9h, and 10h.

[0060] In some embodiments, the release film is selected from at least one of PET release film, PE release film, and PP release film.

[0061] In some specific embodiments, the sulfide solid electrolyte is selected from Li6PS5Cl, Li6PS5Br, Li6PS5I, and Li7P3S. 11 At least one of them.

[0062] In some specific embodiments, the adhesive is selected from at least one of polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), nitrile rubber, styrene-butadiene rubber, and hydrogenated nitrile rubber.

[0063] In some specific embodiments, the organic solvent is selected from at least one of isobutyl isobutyrate, isobutyl isobutyrate, butyl acetate, butyl butyrate, and isoamyl isovalerate.

[0064] In some embodiments, the mass ratio of the sulfide solid electrolyte, binder, and gel electrolyte is (8~10):(0.1~1):(0.1~0.5). Further limiting the mass ratio of the sulfide solid electrolyte, binder, and gel electrolyte is beneficial for improving the ion conductivity of the solid electrolyte membrane, reducing interfacial impedance, and thus better adapting to volume changes in the electrode material. Specifically, the mass ratio of the sulfide solid electrolyte, binder, and gel electrolyte is any value from 8:0.1:0.1, 8:0.5:0.1, 8:1:0.1, 9:0.1:0.1, 9:0.5:0.5, 9:1:0.5, 10:0.1:0.1, 10:0.5:0.5, 10:1:0.5, or a range between any two.

[0065] In some embodiments, the solid content of the mixed slurry is 50-55 wt%. Further limiting the solid content of the mixed slurry facilitates more uniform subsequent coating. Too high or too low a solid content is detrimental to subsequent coating; excessively high solid content leads to uneven coating thickness, while excessively low solid content may result in poor electrolyte dispersion in the solid electrolyte membrane. Specifically, the solid content of the mixed slurry is any value from 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, and 55 wt%, or a range between any two.

[0066] In the third typical embodiment of this application, a sulfide all-solid-state battery is provided, which includes a positive electrode, a negative electrode, a separator, and a solid electrolyte membrane. The solid electrolyte membrane is the solid electrolyte membrane provided in the second typical embodiment of this application.

[0067] The gel electrolyte provided in this application comprises a matrix and a lithium salt dispersed in the matrix. The etheroxy groups in the matrix, due to the partial substitution of hydrogen atoms on adjacent carbon atoms, effectively prevent the gel electrolyte from reacting with the sulfide solid electrolyte while ensuring excellent ion transport capabilities. Furthermore, the matrix structure exhibits good compatibility with the sulfide solid electrolyte, thereby improving the electrochemical performance of the sulfide solid battery. Simultaneously, the specific structure of the matrix allows it to better adapt to changes in electrode material volume. This flexible gel electrolyte can fill pores, acting as an interfacial buffer layer to reduce interfacial impedance, thus improving the electrochemical performance of the sulfide solid battery.

[0068] In some embodiments, the mass of the gel electrolyte in the solid electrolyte membrane accounts for 1-5% of the total mass of the solid electrolyte membrane, preferably 2-3%. Further control of the proportion of gel electrolyte in the solid electrolyte membrane is beneficial to further improve the electrochemical performance of the gel electrolyte in the sulfide all-solid-state battery. Specifically, the mass of the gel electrolyte accounts for any value from 1%, 2%, 3%, 4%, and 5% of the total mass of the solid electrolyte membrane, or any range between two values. In this application, the positive electrode, the solid electrolyte membrane, and the negative electrode are stacked accordingly.

[0069] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples.

[0070] The gel electrolytes used in the following examples and comparative examples have the following structures:

[0071] Equation (A1)

[0072] Formula (A2);

[0073] Formula (A3)

[0074] Equation (A4)

[0075] Formula (A5)

[0076] Formula (B1)

[0077] Formula (B2)

[0078] Formula (B3)

[0079] Example 1

[0080] This embodiment provides a solid electrolyte membrane, the preparation method of which is as follows:

[0081] (1) 1g LiTFSI and 3.5g of matrix with a molecular weight of 700g / mol (the matrix has the structure shown in formula (A1)) were stirred and mixed to obtain a gel electrolyte, wherein the stirring speed was 200rpm and the stirring time was 8h.

[0082] (2) Dissolve 9.5g of sulfide solid electrolyte, 0.5g of PVDF-HFP (polyvinylidene fluoride hexafluoropropylene) and 0.3g of gel electrolyte in 10g of isobutyl isobutyrate and stir at 400rpm for 2h to obtain a mixed slurry. Coat the mixed slurry on an aluminum foil current collector and obtain a solid electrolyte membrane after drying. During the coating process, the doctor blade moving speed is 50mm / min, the doctor blade height is 200μm, the drying temperature is 100℃, and the drying time is 8h.

[0083] Example 2

[0084] The difference between this embodiment and embodiment 1 is that in step (1), the mass of the matrix is ​​adjusted to 4g.

[0085] Example 3

[0086] The difference between this embodiment and embodiment 1 is that in step (1), the molecular weight of the matrix is ​​adjusted to 600 g / mol (the matrix has the structure shown in formula (A2)).

[0087] Example 4

[0088] The difference between this embodiment and embodiment 1 is that in step (1), the structure of the substrate is adjusted to have the structure shown in formula (A3).

[0089] Example 5

[0090] The difference between this embodiment and embodiment 1 is that in step (2), the mass of the gel electrolyte is adjusted to 0.2g.

[0091] Example 6

[0092] The difference between this embodiment and embodiment 1 is that in step (1), the mass of the matrix is ​​adjusted to 5.5g.

[0093] Example 7

[0094] The difference between this embodiment and embodiment 1 is that in step (1), the mass of the matrix is ​​adjusted to 2g.

[0095] Example 8

[0096] The difference between this embodiment and embodiment 1 is that in step (1), the mass of the matrix is ​​adjusted to 4.5g.

[0097] Example 9

[0098] The difference between this embodiment and embodiment 1 is that in step (1), the mass of the matrix is ​​adjusted to 2.3g.

[0099] Example 10

[0100] The difference between this embodiment and embodiment 1 is that in step (1), the structure of the substrate is adjusted to have the structure shown in formula (A4).

[0101] Example 11

[0102] The difference between this embodiment and embodiment 1 is that in step (1), the structure of the substrate is adjusted to have the structure shown in formula (A5).

[0103] Example 12

[0104] The difference between this embodiment and embodiment 1 is that in step (2), the mass of the gel electrolyte is adjusted to 0.1g.

[0105] Example 13

[0106] The difference between this embodiment and embodiment 1 is that in step (2), the mass of the gel electrolyte is adjusted to 0.5g.

[0107] Example 14

[0108] The difference between this embodiment and embodiment 1 is that in step (1), the mass of the matrix is ​​adjusted to 9g.

[0109] Example 15

[0110] The difference between this embodiment and embodiment 1 is that in step (1), the mass of the matrix is ​​adjusted to 1.3g.

[0111] Example 16

[0112] The difference between this embodiment and embodiment 1 is that in step (2), the mass of the gel electrolyte is adjusted to 0.05g.

[0113] Example 17

[0114] The difference between this embodiment and embodiment 1 is that in step (2), the mass of the gel electrolyte is adjusted to 0.7g.

[0115] Comparative Example 1

[0116] The difference between this comparative example and Example 1 is that in step (1), the structure of the substrate is adjusted to have the structure shown in formula (B1).

[0117] Comparative Example 2

[0118] The difference between this comparative example and Example 1 is that in step (1), the structure of the substrate is adjusted to have the structure shown in formula (B2).

[0119] Comparative Example 3

[0120] The difference between this comparative example and Example 1 is that in step (1), the structure of the substrate is adjusted to have the structure shown in formula (B3).

[0121] Comparative Example 4

[0122] The difference between this comparative example and Example 1 is that step (1) is omitted, and the sulfide solid electrolyte, PVDF-HFP (polyvinylidene fluoride hexafluoropropylene), and matrix are dissolved in isobutyl isobutyrate in step (2) to obtain a mixed slurry.

[0123] Experimental Example 1

[0124] The solid electrolyte membranes prepared in the above embodiments and comparative examples were subjected to ionic conductivity tests and impedance tests at 5 MPa.

[0125] The ionic conductivity can be calculated using the following formula after the resistance of the solid electrolyte membrane is obtained by AC impedance testing:

[0126]

[0127] Where σ is the ionic conductivity (S·cm) -1 R is resistance (Ω), l is thickness (cm), and A is area (cm²). 2 ).

[0128] The test results are shown in Table 1.

[0129] Table 1

[0130]

[0131] Experimental Example 2

[0132] The solid electrolyte membrane, positive electrode, and negative electrode prepared in the above examples and comparative examples were assembled into a sulfide solid-state battery, and its electrochemical performance was tested.

[0133] (a) Assembling sulfide solid-state batteries

[0134] (1) Positive electrode sheet: The ternary positive electrode active material (NCM811), sulfide solid electrolyte (Li6PS5Cl), conductive agent (carbon nanotubes), and binder (styrene-butadiene rubber (SBR)) are mixed in a mass ratio of 69:25:2:4 and ball-milled at 300 rpm for 1 h to obtain a positive electrode slurry. The positive electrode slurry is coated on aluminum foil and then dried at 120°C for 10 h to obtain a positive electrode sheet.

[0135] (2) Negative electrode sheet: Graphite, sulfide solid electrolyte (Li6PS5Cl), conductive agent (carbon nanotubes) and binder (styrene-butadiene rubber (SBR)) are mixed in a mass ratio of 75:20:2:3 and ball-milled at 300 rpm for 1 h to obtain a negative electrode slurry. The negative electrode slurry is coated on aluminum foil and then dried at 120°C for 10 h to obtain a negative electrode sheet.

[0136] (3) Assembly of sulfide solid-state battery: Die-cut the positive electrode and negative electrode into shape; stack the negative electrode, solid electrolyte membrane and positive electrode in the aluminum-plastic film in the order of layer by layer, and seal the three sides of the aluminum-plastic film, leaving the tab lead-out edge; place it in the built-in tabletop flat press in the glove box, and press it under 100~200MPa pressure for 10~20min; vacuum seal the aluminum-plastic film containing the battery cell.

[0137] (II) Electrochemical performance testing

[0138] (1) Charge / discharge specific capacity test: At 25℃, the assembled all-solid-state battery was charged and discharged. First, it was charged at a constant current rate of 0.1C to 2.8V, and then discharged at a constant current rate of 0.1C to 4.2V. The specific capacity at 0.1C charging and 0.1C discharging was recorded, and the first efficiency was calculated according to the formula:

[0139] First-time efficiency (%) = 0.1C discharge specific capacity / 0.1C charge specific capacity × 100%.

[0140] (2) Charge-discharge capacity retention test at 0.33C and 0.5C:

[0141] At 25℃, a constant current discharge test was conducted at a rate of 0.33C. First, the voltage was charged to 2.8V at a constant current rate of 0.33C, and then discharged to 4.2V at a constant current rate of 0.33C. The discharge specific capacity was recorded.

[0142] At 25℃, a constant current discharge test was conducted at a rate of 0.5C. First, the voltage was charged to 2.8V at a constant current rate of 0.5C, and then discharged to 4.2V at a constant current rate of 0.5C. The discharge specific capacity was recorded.

[0143] The test results are shown in Table 2.

[0144] Table 2

[0145]

[0146] Comparing Examples 1-17 and Comparative Examples 1-4, it can be seen that the gel electrolytes provided in Examples 1-17, employing a matrix with a specific structure, effectively prevent the gel electrolyte from reacting with the sulfide solid electrolyte while ensuring excellent ion transport capabilities. Furthermore, the chemical structure of the matrix exhibits good compatibility with the sulfide solid electrolyte, thereby improving the electrochemical performance of the sulfide solid battery. Simultaneously, the specific chemical structure of the matrix allows it to better adapt to changes in electrode material volume. In addition, the gel electrolyte provided in this application serves as a flexible electrolyte, and the resulting solid electrolyte membrane can also reduce interfacial impedance by filling pores, thus improving the electrochemical performance of the sulfide solid battery. The lack of a matrix with a specific structure in Comparative Examples 1-3 may result in significant steric hindrance, hindering the achievement of good compatibility between the gel electrolyte and the sulfide solid electrolyte, as well as excellent electrochemical performance. In Comparative Example 4, only the matrix was used without adding lithium salt to obtain the gel electrolyte. It can be seen that the solid electrolyte membrane exhibits high interfacial impedance and poor ion conductivity, leading to poor electrochemical performance of the sulfide all-solid battery.

[0147] Comparing Examples 1-13 and Examples 14-15, it can be seen that a suitable matrix mass can be mixed with lithium salt to obtain a more uniform gel electrolyte, thereby enabling the prepared solid electrolyte membrane to have both excellent ion transport capability and good electrochemical performance.

[0148] Comparing Examples 1-13 and Examples 16-17, it can be seen that a suitable gel electrolyte quality can help improve the ion conductivity of the solid electrolyte membrane and reduce interfacial impedance. The gel electrolyte is a flexible electrolyte that can fill the pores and act as an interfacial buffer layer, thereby better adapting to the volume changes of the electrode material and improving the electrochemical performance of the sulfide solid battery.

[0149] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0150] The gel electrolyte provided in this application comprises a matrix and a lithium salt dispersed in the matrix. The matrix contains etheroxy groups, and by partially substituting hydrogen atoms on the adjacent carbon atoms of the etheroxy groups, the reaction between the gel electrolyte and the sulfide solid electrolyte can be effectively avoided, while ensuring excellent ion transport capabilities. Furthermore, the chemical structure of the matrix has good compatibility with the sulfide solid electrolyte, thereby improving the electrochemical performance of the sulfide solid battery. Simultaneously, the specific chemical structure of the matrix allows it to better adapt to changes in electrode material volume. In addition, the gel electrolyte provided in this application is a flexible electrolyte and can also act as an interfacial buffer layer by filling pores, reducing interfacial impedance and further improving the electrochemical performance of the sulfide solid battery.

[0151] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A gel electrolyte, characterized in that, The gel electrolyte comprises a matrix and a lithium salt dispersed in the matrix, the matrix having a structure as shown in Formula I, and the molecular weight of the matrix being 500-800 g / mol. Formula I Wherein, R is methyl or ethyl, R1 is a nonpolar group, R2 is selected from C4 to C10 alkyl groups, m is an integer between 4 and 18, and n is an integer between 2 and 9.

2. The gel electrolyte according to claim 1, characterized in that, The molecular weight of the matrix is ​​500~750 g / mol, preferably 600~700 g / mol; And / or, the R2 is selected from C4-C8 alkyl groups, preferably C6-C8 alkyl groups; And / or, where m is an integer between 5 and 15, and n is an integer between 3 and 8.

3. The gel electrolyte according to claim 1 or 2, characterized in that, R1 is selected from at least one of methyl, ethyl, phenyl, benzyl, phenethyl, and C1-C2 haloalkyl groups; wherein, R1 is CyH2y. +1 X is a haloalkyl group, wherein y is an integer between 1 and 2, and preferably X is selected from at least one of F, Cl, Br, and I.

4. The gel electrolyte according to any one of claims 1 to 3, characterized in that, The matrix is ​​selected from at least one having the structure shown in formula (A1), formula (A2), and formula (A3): Formula (A1); Formula (A2); Formula (A3).

5. The gel electrolyte according to any one of claims 1 to 4, characterized in that, The lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, and lithium bisfluoroamideimide; And / or, the mass ratio of the matrix to the lithium salt is 1:(0.18~0.50), preferably 1:(0.22~0.43).

6. A solid electrolyte membrane, characterized in that, The raw materials for the solid electrolyte membrane include sulfide solid electrolyte, binder and gel electrolyte, wherein the gel electrolyte is the gel electrolyte according to any one of claims 1 to 5.

7. The solid electrolyte membrane according to claim 6, characterized in that, The method for preparing the solid electrolyte membrane includes: mixing the sulfide solid electrolyte, the binder, the gel electrolyte and the organic solvent to obtain a mixed slurry, coating the mixed slurry on a release film, and removing the organic solvent to obtain the solid electrolyte membrane; Preferably, the sulfide solid electrolyte is selected from Li6PS5Cl, Li6PS5Br, Li6PS5I, and Li7P3S. 11 At least one of them; Preferably, the adhesive is selected from at least one of polyvinylidene fluoride hexafluoropropylene, nitrile rubber, styrene-butadiene rubber, and hydrogenated nitrile rubber; Preferably, the organic solvent is selected from at least one of isobutyl isobutyrate, butyl acetate, butyl butyrate, and isoamyl isovalerate.

8. The solid electrolyte membrane according to claim 6 or 7, characterized in that, The mass ratio of the sulfide solid electrolyte, the binder, and the gel electrolyte is (8~10):(0.1~1):(0.1~0.5). And / or, the solid content of the mixed slurry is 50~55wt%.

9. A sulfide all-solid-state battery, characterized in that, The sulfide all-solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte membrane, wherein the solid electrolyte membrane is the solid electrolyte membrane according to any one of claims 6 to 8.

10. The sulfide all-solid-state battery according to claim 9, characterized in that, The mass of the gel electrolyte in the solid electrolyte membrane accounts for 1 to 5% of the total mass of the solid electrolyte membrane, preferably 2 to 3%.

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