Composite electrode, method for preparing the same, and all-solid-state battery

Abstract

The application provides a composite electrode, a preparation method thereof and a full solid-state battery. The composite electrode comprises: a pole piece; and a composite electrolyte film arranged on the surface of the pole piece, wherein the composite electrolyte film comprises a first layer of electrolyte film close to one side of the pole piece and a second layer of electrolyte film adjacent to the first layer of electrolyte film and located away from the other side of the pole piece, the first layer of electrolyte film contains lithium salt, inorganic electrolyte and polymer, and the second layer of electrolyte film contains sulfide electrolyte, a binder and a dispersing agent. According to the composite electrode provided by the application, the coating of the electrolyte on the pole piece is uniform and reliable, and the mechanical strength of the electrolyte film as a whole is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of all-solid-state batteries, in particular to a composite electrode, a preparation method thereof and an all-solid-state battery. BACKGROUND

[0002] In recent years, with the vigorous support of the country, the electric vehicle industry has developed rapidly. With the increasing demand of people for the endurance mileage of electric vehicles, all-solid-state batteries have become the focus of the industry due to their safety, higher energy density, fast charging, and recyclable convenience. Among them, the solid-state electrolyte is the technical core of the all-solid-state battery.

[0003] At present, the film forming method of solid-state electrolyte mainly includes dry method and wet method.

[0004] The dry method mainly introduces a binder into the solid-state electrolyte, and then obtains a film through mixing, shearing and repeated rolling. This film forming method is more environmentally friendly and does not introduce solvents, but the porosity of the film after film forming is large, and the battery assembled with the dry film electrolyte is prone to short circuit.

[0005] The wet film mainly introduces a binder and a solvent into the electrolyte powder to form a slurry with a certain solid content, and then coats the slurry on a certain substrate by means of doctor blade coating. The wet film forming method has high requirements for solvents and binders, which can greatly reduce the conductivity of the powder electrolyte. Moreover, the use of organic solvents in the film forming process will cause environmental pollution and resource waste. In addition, the electrolyte film formed by direct film forming with the wet method has low conductivity and poor mechanical strength, and cannot realize roll-to-roll film forming. In order to improve the mechanical strength of the electrolyte film, the currently available method is to coat the electrolyte slurry on the positive and negative electrode sheets to form a composite electrode sheet. However, when the electrolyte slurry is coated on the positive and negative electrode sheets, the solvent in the electrolyte slurry will penetrate into the voids of the electrode sheet due to the high porosity and large pore size of the active material layer on the surface of the electrode sheet, which will cause the slurry on the positive and negative electrode sheets to be slurryized during the coating process, resulting in poor coating uniformity or normal coating failure. SUMMARY

[0006] Therefore, the present application provides a composite electrode, a preparation method thereof and an all-solid-state battery, which can make the coating of electrolyte on the electrode sheet uniform and reliable.

[0007] To solve the above technical problems, the present application adopts the following technical solutions:

[0008] The composite electrode according to the first aspect of the present application comprises:

[0009] an electrode sheet;

[0010] A composite electrolyte membrane is disposed on the surface of the electrode. The composite electrolyte membrane includes a first electrolyte membrane layer close to the electrode and a second electrolyte membrane layer adjacent to the first electrolyte membrane layer and located away from the electrode.

[0011] The first electrolyte membrane contains lithium salt, inorganic electrolyte, and polymer.

[0012] The second electrolyte membrane contains a sulfide electrolyte and a binder.

[0013] Furthermore, the electrode includes a current collector and an active material layer disposed on the surface of the current collector, wherein the composite electrolyte membrane is disposed on the active material layer.

[0014] Furthermore, the electrode is either a positive electrode or a negative electrode.

[0015] Further, the lithium salt includes lithium bis(fluorosulfonyl)imide, LiPF6, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxolaneborate, or mixtures thereof;

[0016] The inorganic electrolyte includes lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, or a mixture thereof;

[0017] The polymer includes polydioxolane, polyvinyl chloride, polyfluoroethylene carbonate, or mixtures thereof;

[0018] The sulfide electrolyte includes Li₂SP₂S₅, Li 10 GeP2S 12 Li 954 Si 174 P 14.4 S 117 Cl3, Li 10 SnP2S 12 , Li6PS5Cl, Li6PS5I, Li6PS5Br, Li 55 PS 45 Cl 15 or mixtures thereof;

[0019] The adhesive includes nitrile rubber, hydrogenated nitrile rubber, styrene-butadiene-styrene block copolymer, or mixtures thereof.

[0020] The method for preparing a composite electrode according to a second aspect embodiment of the present invention includes the following steps:

[0021] S1 provides electrode plates;

[0022] S2, providing a first slurry containing a polymer monomer, a lithium salt, and an inorganic electrolyte;

[0023] S3, providing a second slurry containing a sulfide electrolyte, a binder, and a solvent;

[0024] S4, using the first slurry and the second slurry, a double-layer coating is applied to the surface of the electrode, so that the first slurry is coated on the surface of the electrode and the second slurry is coated on the coating of the first slurry, to obtain a preform.

[0025] S5, the preform is heated so that the coating of the first slurry forms a first electrolyte film and the coating of the second slurry forms a second electrolyte film, thereby obtaining a composite electrode.

[0026] Further, step S2 includes:

[0027] The polymer monomer, lithium salt, and inorganic electrolyte are thoroughly mixed to obtain the first slurry.

[0028] In the first slurry, the mass content of the inorganic electrolyte is 20wt%-40wt%;

[0029] The concentration of the lithium salt is 0.5–1 M;

[0030] The polymer monomers include dioxolane, vinyl chloride, or fluoroethylene carbonate;

[0031] The lithium salt includes lithium bis(fluorosulfonyl)imide, LiPF6, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxaborate, or mixtures thereof;

[0032] The inorganic electrolyte includes lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide, or mixtures thereof.

[0033] Further, step S3 includes:

[0034] Weigh out the sulfide electrolyte, binder, and solvent;

[0035] The sulfide electrolyte, binder, and solvent are mixed using a mixer to obtain the second slurry, wherein the mixing time is 20-30 minutes and the rotation speed is 800-1000 rpm.

[0036] Furthermore, the sulfide electrolyte includes Li₂SP₂S₅ and Li₂S₂S₅. 10 GeP2S 12 Li 954 Si 174 P 14.4 S 117 Cl3, Li 10 SnP2S 12, Li6PS5Cl, Li6PS5I, Li6PS5Br, Li 55 PS 45 Cl 15 or mixtures thereof;

[0037] The adhesive includes nitrile rubber, hydrogenated nitrile rubber, styrene-butadiene-styrene block copolymer, or a mixture thereof;

[0038] The solvent includes toluene, anisole, isobutyl isobutyrate, or n-heptane.

[0039] Furthermore, in the second slurry, the content of the sulfide electrolyte is 30-70 wt%, and the binder is 0.2-5% of the mass of the sulfide electrolyte.

[0040] Further, step S4 includes:

[0041] The first slurry and the second slurry are respectively injected into the double-layer coating mold of the coating machine;

[0042] The coating machine is used to perform double-layer coating on the electrode at a coating speed of 50-2000 mm / s, with a scraping gap of 15-50 μm for the first slurry and a scraping gap of 50-400 μm for the second slurry, so that the first slurry is directly coated on the surface of the electrode, and the second slurry is coated on the surface of the first slurry.

[0043] Furthermore, in step S5, heating is performed under vacuum conditions at a temperature of 70-120°C for a duration of 10-15 hours.

[0044] According to a third aspect of the present invention, an all-solid-state battery includes a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode is a composite electrode according to any embodiment of the first aspect, or a composite electrode prepared according to any embodiment of the second aspect.

[0045] The above-described technical solution of the present invention has at least one of the following beneficial effects:

[0046] According to the composite electrode of the present invention, a first electrolyte film is polymerized in situ on the surface of the electrode, which can avoid the slurry formation caused by the direct coating of electrolyte slurry (i.e., sulfide electrolyte slurry) on the electrode side and increase the uniformity of electrolyte slurry coating.

[0047] In addition, by directly coating the electrolyte slurry onto the positive and negative electrode sheets, the contact area between the positive and negative electrode active materials and the electrolyte is greatly increased, providing more interfacial ion transport channels, greatly reducing interfacial impedance, and enhancing the rate capability and other electrical performance of the all-solid-state battery.

[0048] In addition, by adding an in-situ polymerized buffer layer to the surface of the positive and negative electrode sheets, the expansion of the material volume of the positive and negative electrode active materials during charging and discharging is suppressed, especially the expansion of the Si negative electrode, which makes the all-solid-state battery more stable during cycling.

[0049] In addition, a second electrolyte membrane is coated on the side adjacent to the first electrolyte membrane and located away from the electrode. The second electrolyte membrane contains sulfide electrolyte and binder. While ensuring conductivity, it enhances the overall mechanical strength of the pure wet electrolyte membrane and is beneficial for the roll-to-roll formation of the sulfide electrolyte. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the structure of the composite electrode according to the first aspect of the present invention;

[0051] Figure 2 This is a flowchart illustrating a method for preparing a composite electrode according to a second aspect of the present invention;

[0052] Figure 3 This is a schematic diagram showing the relationship between the number of cycles and capacity retention rate of an all-solid-state battery at 0.33C, according to a third aspect embodiment of the present invention.

[0053] Reference numerals: 100. Composite electrode; 110. Electrode sheet; 120. Composite electrolyte membrane; 121. First electrolyte membrane; 122. Second electrolyte membrane. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0055] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0056] The composite electrode according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0057] According to the first aspect of the embodiment of the composite electrode 100, such as Figure 1 As shown, it includes: electrode 110 and composite electrolyte membrane 120.

[0058] The composite electrolyte membrane 120 is disposed on the surface of the electrode 110. The composite electrolyte membrane 120 includes a first electrolyte membrane 121 close to the electrode 110 and a second electrolyte membrane 122 adjacent to the first electrolyte membrane 121 and located away from the electrode 110.

[0059] The first electrolyte membrane 121 contains lithium salt, inorganic electrolyte, and polymer.

[0060] The second electrolyte membrane 122 contains sulfide electrolyte and binder.

[0061] According to an embodiment of the present invention, the composite electrode 100 is constructed by sequentially coating a first electrolyte film 121 and a second electrolyte film 122 on one side surface of the electrode 110, wherein the second electrolyte film 122 is coated on the first electrolyte film 121. In other words, by constructing the first electrolyte film 121 in situ on one side surface of the electrode as a buffer layer, the slurry containing sulfide electrolyte can be avoided from being directly coated on the electrode side, thus increasing the uniformity of the sulfide electrolyte slurry coating. In addition, by polymerizing the first electrolyte film in situ on the surface of the electrode, which contains lithium salt and inorganic electrolyte, the interfacial impedance between the positive and negative electrodes and the electrolyte layer is significantly reduced. Furthermore, in the case of a composite negative electrode, the expansion of the silicon negative electrode can be suppressed. By coating the second electrolyte film adjacent to the first electrolyte film and located away from the electrode, the overall mechanical strength of the pure wet-process sulfide electrolyte film can be enhanced while ensuring conductivity, which is beneficial for the preparation of the sulfide electrolyte roll-to-roll film.

[0062] Furthermore, the electrode 110 includes a current collector (not shown) and an active material layer (not shown) disposed on the surface of the current collector, wherein the composite electrolyte membrane 120 is disposed on the active material layer.

[0063] In other words, the composite electrolyte membrane 120 is coated on the active material layer of the electrode 110, so that the electrolyte is coated uniformly and reliably on the electrode 110.

[0064] Furthermore, electrode 110 can be either a positive or negative electrode.

[0065] In other words, the electrode 110 can be either a positive electrode or a negative electrode. Specifically, by coating the positive electrode side with a first electrolyte film 121 formed by in-situ polymerization with good elasticity, the impedance of the positive electrode side and the sulfide electrolyte layer can be greatly reduced, enabling the full cell to achieve better rate performance. Introducing the first electrolyte film 121 formed by in-situ polymerization with good elasticity on the negative electrode side (e.g., a silicon negative electrode sheet) can also suppress the expansion of the silicon negative electrode during charging, making the silicon negative electrode more stable in cycling.

[0066] Preferably, the lithium salt may include lithium bis(fluorosulfonyl)imide (LiFSI), LiPF6, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium dioxolaneborate (LiBOB), or mixtures thereof.

[0067] Inorganic electrolytes may include lithium lanthanum zirconium oxide (LLZO), tantalum-doped lithium lanthanum zirconium oxide (LLZTO), lithium lanthanum titanium oxide (LLTO), or mixtures thereof.

[0068] The polymer may include polydioxolane (PDOL), polyvinyl chloride (PVC), polyfluoroethylene carbonate (PFEC), or mixtures thereof.

[0069] Sulfide electrolytes may include Li₂SP₂S₅, Li 10 GeP2S 12 Li 954 Si 174 P 14.4 S 117 Cl3, Li 10 SnP2S 12 , Li6PS5Cl, Li6PS5I, Li6PS5Br, Li 55 PS 45 Cl 15 Or a mixture thereof.

[0070] The adhesive may include nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), styrene-butadiene-styrene block copolymer (SBS), or mixtures thereof.

[0071] According to a second aspect embodiment of the present invention, a method for preparing a composite electrode is as follows: Figure 2 As shown, it includes the following steps:

[0072] S1 provides electrode plates;

[0073] S2 provides a first slurry containing polymer monomers, lithium salts, and an inorganic electrolyte;

[0074] S3 provides a second slurry containing a sulfide electrolyte, a binder, and a solvent;

[0075] S4, using the first slurry and the second slurry, a double-layer coating is applied to the surface of the electrode, so that the first slurry is coated on the surface of the electrode and the second slurry is coated on the coating of the first slurry, to obtain a preform;

[0076] S5, the preform is heated so that the coating of the first slurry forms a first electrolyte film and the coating of the second slurry forms a second electrolyte film, thus obtaining a composite electrode.

[0077] In other words, according to the method for preparing the composite electrode according to the embodiments of the present invention, a double layer of slurry is coated on the surface of the electrode sheet, that is, a first slurry and a second slurry are sequentially coated on the surface of the electrode sheet, with the first slurry coated on the surface of the electrode sheet and the second slurry coated on the coating of the first slurry. After the coating is completed, it is heated so that the coatings of the first slurry and the second slurry respectively form a first electrolyte film and a second electrolyte film, and finally a composite electrode sheet is obtained.

[0078] Below, each step will be explained in more detail.

[0079] In step S1, the electrode can be either a positive electrode or a negative electrode.

[0080] The positive electrode can be a ternary, lithium iron phosphate, or lithium manganese oxide electrode. The current collector of the positive electrode is coated with an active material layer with a thickness of 200-400 μm.

[0081] The negative electrode can be, for example, a silicon or silicon-carbon composite electrode. The current collector of the negative electrode is coated with a 50-80 μm layer of active material.

[0082] There are no specific restrictions on the active material layers in the positive and negative electrode sheets; they can be active material layers commonly used in this field.

[0083] In some embodiments of this application, step S2 may include:

[0084] The polymer monomer, lithium salt, and inorganic electrolyte are thoroughly mixed to obtain the first slurry.

[0085] In the first slurry, the inorganic electrolyte content is 20wt%-40wt%.

[0086] The concentration of lithium salt is 0.5–1 M.

[0087] The polymer monomers include dioxolane (DOL), vinyl chloride (VC), or fluoroethylene carbonate (FEC).

[0088] Lithium salts include lithium bis(fluorosulfonyl)imide (LiFSI), LiPF6, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium dioxolaneborate (LiBOB), or mixtures thereof.

[0089] Inorganic electrolytes include lithium lanthanum zirconium oxide (LLZO), tantalum-doped lithium lanthanum zirconium oxide (LLZTO), or mixtures thereof.

[0090] In other words, the first slurry composed of the above-mentioned material components can be used to prepare a flexible buffer layer, and can further reduce the interfacial impedance between the positive and negative electrodes and the electrolyte layer, improve the conductivity, and increase the rate of the battery cell.

[0091] Further, step S3 may include:

[0092] Weigh out the sulfide electrolyte, binder, and solvent.

[0093] The sulfide electrolyte, binder, and solvent are mixed in a mixer to obtain a second slurry. The mixing time is 20-30 minutes and the rotation speed is 800-1000 rpm.

[0094] Furthermore, the sulfide electrolyte may include Li₂SP₂S₅, Li 10 GeP2S 12 Li 954 Si 174 P 14.4 S 117 Cl3, Li 10 SnP2S 12 , Li6PS5Cl, Li6PS5I, Li6PS5Br, Li 55 PS 45 Cl 15 Or a mixture thereof.

[0095] The adhesive may include nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), styrene-butadiene-styrene block copolymer (SBS), or mixtures thereof.

[0096] Solvents may include toluene, anisole, isobutyl isobutyrate, or n-heptane. The solvent can be selected in conjunction with the specific sulfide electrolyte and binder used.

[0097] In other words, the second slurry composed of the above-mentioned material components, after being coated on the electrode, realizes a composite electrode of the electrode and the sulfide electrolyte layer. This not only ensures sufficient conductivity but also effectively improves the overall strength of the electrolyte membrane and facilitates the roll-to-roll production of the sulfide electrolyte membrane.

[0098] Furthermore, in the second slurry, the content of sulfide electrolyte is 30-70 wt%, and the binder is 0.2-5% of the mass of the sulfide electrolyte.

[0099] It should be noted that a dispersant can be added to the second slurry to improve the uniformity of the sulfide electrolyte dispersion. For example, commercially available Croda dispersant can be added. The amount of dispersant can be, for example, 0.1-5% of the mass of the sulfide electrolyte.

[0100] Further, step S4 may include:

[0101] The first slurry and the second slurry are injected into the double-layer coating mold of the coating machine, respectively.

[0102] Specifically, the machine can be set to coat the electrode sheet with a coating speed of 50-2000 mm / s, a scraping gap of 15-50 μm for the first slurry and a scraping gap of 50-400 μm for the second slurry, so that the first slurry is directly coated on the surface of the electrode sheet and the second slurry is coated on the surface of the first slurry.

[0103] The thickness of the first electrolyte membrane, which serves as a buffer layer, can be changed by adjusting the coating gap of the first slurry; similarly, the thickness of the sulfide electrolyte layer, i.e., the second electrolyte membrane, can be changed by adjusting the coating gap of the second slurry. The coating speed can be set by combining the viscosities of the first and second slurries, as well as the coating gap between them, to achieve better coating uniformity. For example, the coating speed can be set to 50 mm / s, 100 mm / s, 500 mm / s, 1000 mm / s, 1500 mm / s, 2000 mm / s, etc.

[0104] Furthermore, in step S5, heating is carried out under vacuum conditions, with a heating temperature of 70-120℃ and a heating time of 10-15h.

[0105] In other words, after coating, the material is heated. On the one hand, heating causes the polymer monomers in the first slurry to polymerize in situ, generating a three-dimensional polymer network that forms a first electrolyte membrane with high mechanical strength, acting as a buffer layer. On the other hand, heating allows the solvent in the second slurry to evaporate, thus forming a second electrolyte membrane.

[0106] In addition, heating under vacuum conditions can prevent the oxidation of substances such as sulfide electrolytes.

[0107] In addition, in order to control the solvent evaporation rate in the coating formed by the second slurry on the surface, it can be optionally left to stand at room temperature for 1-12 hours before being heated under vacuum conditions.

[0108] According to a third aspect of the present invention, an all-solid-state battery includes a positive electrode, a solid electrolyte layer, and a negative electrode, wherein at least one of the positive electrode and the negative electrode is a composite electrode prepared according to any embodiment of the first aspect, or a composite electrode prepared according to any embodiment of the second aspect.

[0109] There are no particular limitations on the method for preparing all-solid-state batteries using the above-mentioned composite electrode. For example, it can be done as follows:

[0110] S100 provides a positive composite electrode and a negative composite electrode.

[0111] For example, the positive electrode composite electrode and the negative electrode composite electrode prepared through the second aspect embodiments described above. The positive electrode composite electrode refers to a composite electrode obtained by combining a positive electrode as an electrode sheet with a composite electrolyte membrane. The negative electrode composite electrode refers to a composite electrode obtained by combining a negative electrode as an electrode sheet with an electrolyte membrane.

[0112] It should be noted that this application is not limited to this; either the positive electrode or the negative electrode may be a composite electrode prepared by the above method on only one side.

[0113] S200 provides a solid electrolyte layer.

[0114] Regarding the solid electrolyte layer, this application is for sulfide electrolyte batteries. Here, the solid electrolyte layer refers to the sulfide electrolyte layer, which can be any conventionally used sulfide electrolyte material, or a corresponding material selected in combination with the components in the sulfide electrolyte membrane in the composite electrode.

[0115] There are no specific restrictions on the preparation method of the solid electrolyte layer; it can be prepared by any method commonly used in the field.

[0116] S300 is a process in which a positive electrode composite electrode, a solid electrolyte, and a negative electrode composite electrode are stacked sequentially, and then assembled after isostatic pressing to obtain an all-solid-state battery.

[0117] The composite electrode of this application is particularly suitable for the preparation of pouch cells.

[0118] Examples of the preparation of the all-solid-state battery of the present invention are listed below.

[0119] Example 1

[0120] (1) Preparation of positive electrode composite sheet and negative electrode composite sheet.

[0121] The active material layer of the positive electrode has a composition mass ratio of ternary lithium (NCM811): sulfide electrolyte: binder: conductive agent = 70:26:2.5:1.5. The binder is nitrile rubber (NBR), the conductive agent is carbon nanofiber (VGCF), the sulfide electrolyte is Li6PS5Cl, and the coating thickness of the active material on the positive electrode is 200μm.

[0122] In the active material layer of the negative electrode sheet, the mass ratio of the components is Si:graphite:polyvinylidene fluoride (PVDF):VGCF = 70:27:1.5:1.5, and the coating thickness of the active material on the negative electrode sheet is 70μm.

[0123] The prepared positive and negative electrode sheets are fixed on the coating machine respectively.

[0124] (2) Prepare the first slurry, which consists of dioxolane (DOL), lithium bis(fluorosulfonyl)imide (LiFSI) and lithium lanthanum titanium oxide (LLTO), with a mass ratio of DOL:LiFSI:LLTO = 60:10:20.

[0125] (3) Prepare a second slurry. The main components of the slurry are Li6PS5Cl, NBR binder, Croda dispersant, and toluene solvent. Specifically, in the second slurry, the mass content of Li6PS5Cl is 40%, the content of the binder is 5% of the mass of the sulfide electrolyte, and the content of the dispersant is 1% of the mass of the sulfide electrolyte.

[0126] (4) The first slurry and the second slurry are poured into the tank of the double-layer coating mold, respectively. The coating speed of the coating machine is set to 500 mm / s, the coating gap of the first slurry is 15 μm, and the coating gap of the second slurry is 200 μm. The coating is then performed by scraping. The first slurry is directly coated on the positive / negative electrode sheet, and the second slurry is coated on top of the coating of the first slurry. The preform is thus obtained.

[0127] (5) The preforms were placed in an oven and vacuum dried. The temperature of the oven was 100°C and the heating time was 11 hours. Positive and negative composite electrodes were obtained respectively.

[0128] (6) Preparation of the solid electrolyte layer. Prepare a sulfide electrolyte slurry with a specific ratio: Weigh 1.96g of LPSCl electrolyte powder, add 0.04g of NBR, then add 0.01g of Croda dispersant and 2g of toluene solution. Mix the mixture in a mixer for half an hour to obtain a slurry of a certain concentration. Place the PET film on a coating machine, with the slurry applied to the inside of the scraper blade, with a blade gap of 100μm. Place the prepared electrolyte film in a drying room at a temperature between -50℃ and -60℃ for 6 hours. Finally, transfer it to a 70℃ oven for 12 hours to obtain the solid electrolyte layer.

[0129] (7) The prepared positive electrode composite electrode, solid electrolyte layer and negative electrode composite electrode are stacked and subjected to isostatic pressing. The isostatic pressing pressure is 500 MPa, the isostatic pressing time is 5 min, and the test pressure is 100 MPa.

[0130] After assembly, an all-solid-state battery was produced.

[0131] Example 2

[0132] (1) Preparation of positive electrode composite sheet and negative electrode composite sheet.

[0133] In the active material layer of the positive electrode, the mass ratio of the components is ternary lithium (NCM811): sulfide electrolyte: binder: conductive agent = 70:30:1.5:1.5. The binder is nitrile rubber (NBR), the conductive agent is carbon nanofiber (VGCF), the sulfide electrolyte is Li6PS5Cl, and the coating thickness of the active material on the positive electrode is 260μm.

[0134] In the active material layer of the negative electrode sheet, the mass ratio of the components is Si:graphite:polyvinylidene fluoride (PVDF):VGCF = 70:27:1.5:1.5, and the thickness of the active material coated on the negative electrode sheet is 60μm.

[0135] The prepared positive and negative electrode sheets are fixed on the coating machine respectively.

[0136] (2) Prepare the first slurry, which consists of FEC (fluoroethylene carbonate), lithium bis(fluorosulfonyl)imide (LiFSI) and lithium lanthanum titanium oxide (LLTO), with a mass ratio of FEC:LiFSI:LLTO = 50:10:20.

[0137] (3) Prepare a second slurry, which consists of Li6 PS5 Cl, NBR binder, Croda dispersant and solvent. In the second slurry, the content of Li6 PS5 Cl is 30%, the content of binder is 2% of the mass of sulfide electrolyte, and the content of dispersant is 1% of the mass of sulfide electrolyte.

[0138] (4) Pour the first and second slurries into the groove of the double-layer coating mold respectively, set the coating speed of the coating machine to 500 mm / s, the coating gap of the first layer of slurry to 15 μm, the coating gap of the second layer of slurry to 200 μm, and perform scraping to obtain the preform.

[0139] (5) The preforms were placed in an oven and vacuum dried at a temperature of 100°C for 11 hours to obtain composite electrodes.

[0140] (6) Preparation of the solid electrolyte layer. Prepare a sulfide electrolyte slurry with a specific ratio: Weigh 1.96g of LPSCl electrolyte powder, add 0.04g of NBR, then add 0.01g of Croda dispersant and 2g of toluene solution. Mix the mixture in a mixer for half an hour to obtain a slurry of a certain concentration. Place the PET film on a coating machine, with the slurry applied to the inside of the scraper blade, with a blade gap of 100μm. Place the prepared electrolyte film in a drying room at a temperature between -50℃ and -60℃ for 6 hours. Finally, transfer it to a 70℃ oven for 12 hours to obtain the solid electrolyte layer.

[0141] (7) The prepared positive electrode composite electrode, solid electrolyte layer, and negative electrode composite electrode are stacked and subjected to isostatic pressing. The isostatic pressing pressure is 500 MPa and the isostatic pressing time is 5 min. After that, they are assembled to obtain an all-solid-state battery.

[0142] Comparative Example

[0143] The all-solid-state battery was prepared in the same manner as in Example 1, except that the first slurry was not prepared and the second slurry was directly coated onto the positive / negative electrode sheets.

[0144] Charge-discharge tests were conducted on the all-solid-state batteries prepared in the above embodiments and comparative examples. Table 1 shows the cycle performance test results. Figure 3 The graph shows the relationship between the number of cycles and capacity retention at 0.33°C.

[0145] Table 1 Cyclic Performance Evaluation

[0146]

[0147] From Table 1 and Figure 3 It is evident that the all-solid-state battery utilizing this sulfide electrolyte composite membrane exhibits high initial efficiency, good rate performance, and good cycle stability. This indicates that the double-layer coating of the electrolyte membrane on the electrode layer in this invention is highly effective, significantly improving not only the overall mechanical strength of the electrode and electrolyte membrane composite but also its electrochemical performance. This is mainly due to the in-situ polymerization reducing the interfacial impedance between the sulfide electrolyte and the electrode, resulting in less battery polarization and thus significantly improved electrochemical stability. This demonstrates that the method employed in this invention can further reduce interfacial impedance by improving the contact between the sulfide electrolyte and the positive and negative electrodes, thereby achieving a relatively high discharge capacity and excellent rate performance in the all-solid-state battery. Furthermore, the in-situ polymerization product possesses good chemical and electrochemical stability, contributing to the good cycle stability of the all-solid-state battery prepared by this method.

[0148] Furthermore, as seen in Examples 1 and 2, the DOL system exhibits lower specific capacity utilization and first-efficiency, as well as poorer rate performance. The FEC in-situ polymerization system demonstrates superior conductivity and stability compared to the DOL system. This is because the specific capacity utilization and concrete capacity differ between the DOL and FEC in-situ polymerization systems, leading to differences in conductivity and polymer material stability, which in turn cause differences in first-efficiency and rate performance.

[0149] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite electrode, characterized in that, include: Electrode; A composite electrolyte membrane is disposed on the surface of the electrode. The composite electrolyte membrane includes a first electrolyte membrane layer close to the electrode and a second electrolyte membrane layer adjacent to the first electrolyte membrane layer and located away from the electrode. The first electrolyte membrane contains lithium salt, inorganic electrolyte, and polymer. The second electrolyte membrane contains a sulfide electrolyte and a binder; the method for preparing the composite electrode includes the following steps: S1 provides electrode plates; S2, providing a first slurry, the first slurry containing polymer monomers of the polymer, the lithium salt, and the inorganic electrolyte; S3, providing a second slurry containing the sulfide electrolyte, the binder, and a solvent; S4, using the first slurry and the second slurry, a double-layer coating is applied to the surface of the electrode, so that the first slurry is coated on the surface of the electrode and the second slurry is coated on the coating of the first slurry, to obtain a preform. S5, the preform is heated so that the coating of the first slurry forms a first electrolyte film and the coating of the second slurry forms a second electrolyte film, thereby obtaining a composite electrode.

2. The composite electrode according to claim 1, characterized in that, The electrode includes a current collector and an active material layer disposed on the surface of the current collector, wherein the composite electrolyte membrane is disposed on the active material layer.

3. The composite electrode according to claim 1, characterized in that, The electrode is either a positive electrode or a negative electrode.

4. The composite electrode according to claim 1, characterized in that, The lithium salt includes lithium bis(fluorosulfonyl)imide, LiPF6, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxaborate, or mixtures thereof; The inorganic electrolyte includes lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, or a mixture thereof; The polymer includes polydioxolane, polyvinyl chloride, polyfluoroethylene carbonate, or mixtures thereof; The sulfide electrolyte includes Li₂SP₂S₅, Li 10 GeP2S 12 Li 954 Si 174 P 14.4 S 117 Cl3, Li 10 SnP2S 12 , Li6PS5Cl, Li6PS5I, Li6PS5Br, Li 55 PS 45 Cl 15 or mixtures thereof; The adhesive includes nitrile rubber, hydrogenated nitrile rubber, styrene-butadiene-styrene block copolymer, or mixtures thereof.

5. A method for preparing a composite electrode as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1 provides electrode plates; S2, providing a first slurry containing a polymer monomer, a lithium salt, and an inorganic electrolyte; S3, providing a second slurry containing a sulfide electrolyte, a binder, and a solvent; S4, using the first slurry and the second slurry, a double-layer coating is applied to the surface of the electrode, so that the first slurry is coated on the surface of the electrode and the second slurry is coated on the coating of the first slurry, to obtain a preform. S5, the preform is heated so that the coating of the first slurry forms a first electrolyte film and the coating of the second slurry forms a second electrolyte film, thereby obtaining a composite electrode.

6. The preparation method according to claim 5, characterized in that, Step S2 includes: The polymer monomer, lithium salt, and inorganic electrolyte are thoroughly mixed to obtain the first slurry. In the first slurry, the mass content of the inorganic electrolyte is 20wt%-40wt%; The concentration of the lithium salt is 0.5–1 M; The polymer monomers include dioxolane, vinyl chloride, or fluoroethylene carbonate; The lithium salt includes lithium bis(fluorosulfonyl)imide, LiPF6, lithium bis(trifluoromethanesulfonyl)imide, lithium dioxaborate, or mixtures thereof; The inorganic electrolyte includes lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide, or mixtures thereof.

7. The preparation method according to claim 6, characterized in that, Step S3 includes: Weigh out the sulfide electrolyte, binder, and solvent; The sulfide electrolyte, binder, and solvent are mixed using a mixer to obtain the second slurry, wherein the mixing time is 20-30 minutes and the rotation speed is 800-1000 rpm.

8. The preparation method according to claim 7, characterized in that, The sulfide electrolyte includes Li₂SP₂S₅, Li 10 GeP2S 12 Li 954 Si 174 P 14.4 S 117 Cl3, Li 10 SnP2S 12 , Li6PS5Cl, Li6PS5I, Li6PS5Br, Li 55 PS 45 Cl 15 or mixtures thereof; The adhesive includes nitrile rubber, hydrogenated nitrile rubber, styrene-butadiene-styrene block copolymer, or a mixture thereof; The solvent includes toluene, anisole, isobutyl isobutyrate, or n-heptane.

9. The preparation method according to claim 7, characterized in that, In the second slurry, the content of the sulfide electrolyte is 30-70 wt%, and the binder is 0.2-5% of the mass of the sulfide electrolyte.

10. The preparation method according to claim 5, characterized in that, Step S4 includes: The first slurry and the second slurry are respectively injected into the double-layer coating mold of the coating machine; The coating machine is used to perform double-layer coating on the electrode at a coating speed of 50-2000 mm / s, with a scraping gap of 15-50 μm for the first slurry and a scraping gap of 50-400 μm for the second slurry, so that the first slurry is directly coated on the surface of the electrode, and the second slurry is coated on the surface of the first slurry.

11. The preparation method according to claim 5, characterized in that, In step S5, heating is performed under vacuum conditions at a temperature of 70-120°C for 10-15 hours.

12. An all-solid-state battery, characterized in that, It includes a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode is a composite electrode according to any one of claims 1 to 4, or a composite electrode prepared by the preparation method according to any one of claims 5 to 11.

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