Material for improving interface performance of solid electrolyte and electrode in solid-state battery, preparation method and application

Abstract

The invention belongs to the technical field of solid-state battery preparation, and particularly relates to a material for improving the interface performance of a solid-state electrolyte and an electrode in a solid-state battery, a preparation method and application. The material comprises an ethylene-vinyl acetate grafted maleic anhydride polymer and an oxide, the oxide comprises aluminum oxide and / or silicon oxide. When the material is applied to a solid-state battery, the compatibility, the interface thermal stability and the structural stability of an electrode and a solid-state electrolyte can be remarkably improved. Aluminum oxide and / or silicon oxide are / is adopted to modify an ethylene-vinyl acetate grafted maleic anhydride polymer (MAH-g-EVA), and the unique structure and property of MAH-g-EVA are utilized, so that the surface properties of two incompatible materials, namely a solid electrolyte and an electrode, can be effectively improved, and homogenization and high performance at an interface are favorably realized.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery preparation technology, specifically relating to a material, preparation method and application for improving the interface performance between solid electrolyte and electrode in solid-state batteries. Background Technology

[0002] Solid-state batteries are considered a core development direction for next-generation energy storage technology due to their high safety and high energy density. However, the solid-solid interface contact problem has become a key bottleneck restricting their effectiveness.

[0003] Unlike traditional liquid batteries where electrodes and electrolytes form a close contact through liquid phase wetting, solid-state batteries have all components in solid state, leading to numerous problems at the interface. These problems mainly manifest in the following ways: (1) In solid-state batteries, the electrodes and solid electrolytes have a solid-solid contact with a small contact area. Poor physical contact results in high interfacial contact impedance, limiting lithium-ion transport efficiency. (2) Chemical contact is unstable. After the lithium metal anode comes into contact with the solid electrolyte, chemical side reactions easily occur, forming a passivation layer or harmful substances such as Li2S and Li2CO3, which significantly increase interfacial impedance and reduce battery performance. (3) During charging and discharging, the positive and negative electrode materials undergo volume expansion. The contact between the solid electrolyte and the electrodes is difficult to adapt to this change, resulting in volume expansion mismatch, which leads to deterioration of interfacial contact and further exacerbates battery capacity decay. (4) The interface stability between the solid electrolyte and the electrodes is poor, and voids, cracks, or space charge layers are easily generated during cycling, leading to increased interfacial impedance and affecting the cycle life and safety of the battery. (5) Solid electrolytes contain a large number of grain boundaries. The grain boundary resistance is higher than the bulk resistance of the material, which is not conducive to lithium ion transport, resulting in low ionic conductivity and affecting the fast charging performance and cycle life of the battery.

[0004] To address these issues, existing research has attempted to improve interface performance through methods such as introducing buffer layers, surface coatings, and interface modifications, but these methods still fail to significantly improve interface contact and stability. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to improve the solid-solid interface contact, high interface impedance, poor interface stability and low ion transport efficiency of solid electrolyte and electrode in existing solid-state batteries, thereby providing a material, preparation method and application to improve the interface performance of solid electrolyte and electrode in solid-state batteries.

[0006] To this end, the present invention provides the following technical solution.

[0007] The first aspect of the present invention provides a material for improving the interface performance between the solid electrolyte and the electrode in a solid-state battery, comprising: an ethylene-vinyl acetate grafted maleic anhydride polymer and an oxide; wherein the oxide comprises aluminum oxide and / or silicon oxide.

[0008] In one optional embodiment, the molecular weight of the ethylene-vinyl acetate grafted maleic anhydride polymer is 800-3000.

[0009] In one optional embodiment, the median particle size D50 of the oxide is 1-50 nm. As an example, the median particle size D50 can be any value such as 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, etc.

[0010] In one optional embodiment, the grafting rate of maleic anhydride in the ethylene-vinyl acetate-grafted maleic anhydride polymer is 2-15 mol%. As an example, the grafting rate can be any value such as 2 mol%, 3 mol%, 5 mol%, 7 mol%, 9 mol%, 11 mol%, 13 mol%, 15 mol%.

[0011] In one optional embodiment, the vinyl acetate content in the ethylene-vinyl acetate is 20-40% by mass; it should be explained that this mass content refers to the vinyl acetate content in the ethylene-vinyl acetate before grafting maleic anhydride.

[0012] Ethylene-vinyl acetate copolymer (EVA) is obtained by copolymerizing non-polar ethylene monomer (E) with highly polar vinyl acetate monomer (VA). Too low a vinyl acetate content will affect the flexibility and maleic anhydride grafting rate; too high a vinyl acetate content will make EVA close to a rubber elastomer, with a completely amorphous structure, high transparency and high adhesion, but the mechanical strength and heat resistance will decrease.

[0013] In one alternative embodiment, the mass content of the oxide in the material is 0.1-5%. As an example, this mass content can be any value such as 0.1%, 1%, 2%, 3%, 4%, 5%.

[0014] A second aspect of the present invention provides a solid-state battery, comprising a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode;

[0015] A first interface layer is provided between the positive electrode sheet and the solid electrolyte layer, and the first interface layer includes the aforementioned material.

[0016] And / or, a second interface layer is provided between the negative electrode and the solid electrolyte layer, the second interface layer comprising the aforementioned material.

[0017] In one optional implementation, the thickness of the first interface layer is less than the thickness of the second interface layer.

[0018] In one optional implementation, the thickness of the first interface layer is 0.1-3 μm;

[0019] In one alternative embodiment, the thickness of the second interface layer is 1-10 μm.

[0020] This invention controls the thickness of these two interface layers. A thinner film is used on the positive electrode side to penetrate into the pores between the positive electrode and the solid electrolyte, forming an "anchoring structure" to enhance interfacial contact. A thicker film layer (1-10 μm) is used on the negative electrode side to buffer the deposition of metallic lithium with a larger elastic modulus and suppress the formation of lithium dendrites.

[0021] In one alternative embodiment, the solid-state battery includes a lithium-ion battery or a sodium-ion battery.

[0022] In one alternative embodiment, the solid electrolyte layer includes an electrolyte, which includes one or more of polymer electrolytes, oxide electrolytes, halide electrolytes, and sulfide electrolytes.

[0023] In one optional embodiment, the mass content of the electrolyte in the solid electrolyte layer is 50-100%;

[0024] In one alternative embodiment, the solid electrolyte layer further includes an adhesive, such as polytetrafluoroethylene.

[0025] In one alternative implementation, the thickness of the solid electrolyte layer may be not limited to 10-50 μm.

[0026] It should be noted that the type of electrode, including the positive electrode, negative electrode, and solid electrolyte layer, is determined by the type of battery. For example, when the solid-state battery is a lithium-ion battery, the positive electrode, negative electrode, and solid electrolyte layer all use materials commonly found in lithium-ion batteries. An example is shown below:

[0027] In a lithium-ion battery, the positive electrode sheet includes a positive electrode active material layer; the positive electrode active material layer includes a positive electrode active material, which includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, and lithium-rich layered materials; the positive electrode active material layer also includes conductive agents, binders, and other additives, the conductive agents including but not limited to carbon nanotubes, acetylene black, and other known conductive agents; the binders including but not limited to polyvinylidene fluoride, and other known binders; the mass ratio of the positive electrode active material, conductive agent, and binder adopts a ratio known in the art, for example, a ratio of (95.5-98):(1-1.5):(1-3). The thickness of one side of the positive electrode active material layer adopts a conventional thickness in the art, for example, 60-200 μm.

[0028] In a lithium-ion battery, the negative electrode sheet includes a negative electrode active material layer; the negative electrode active material layer includes a negative electrode active material, which includes one or more of lithium metal, natural graphite, artificial graphite, pure silicon, silicon oxide, and silicon carbon. The thickness of the negative electrode active material layer on one side adopts a conventional thickness in the art, for example, 10-160 μm. Optionally, the negative electrode active material layer includes conductive agents, binders, and other additives, all of which use amounts known in the art, and this invention does not limit this.

[0029] In lithium-ion batteries, the polymer electrolyte includes at least one of PEO, PAN, PMMA, PVA, PVP, PVDF, PVDF-HFP, PPC, PEC, PEDGA, PDMS, succinate (SN), and polyethylene glycol (PEG); the halide electrolyte includes any one or more of Li₂MnCl₄, Li₂ZnCl₄, Li₃YCl₆, Li₃BrCl₆, Li₃InCl₆, Li₆CoCl₈, and Li₆VCl₈; the oxide electrolyte includes any one or more of LATP, LLZO, LLZTO, LiPON, and LAGP; and the sulfide electrolyte includes Li₃PS₄ and Li₇P₃S. 11 Li 10 GeP2S 12 Any one or more of Li6PS5Cl, Li4SnS4 and Li3SbS4.

[0030] In a sodium-ion battery, the positive electrode includes a positive electrode active material layer; the positive electrode active material layer includes a positive electrode active material, which includes a layered transition metal oxide with the general formula NaMO2 (M includes Co, Mn, Fe or Ni) containing active sodium ions, or a layered transition metal oxide with the general formula Na... x M y (X a O b ) z Z w The positive electrode active material layer comprises one or more of the following: a polyanionic compound containing V, Fe, Mn, Ti, Co, etc.; X containing P, S, B, Si, etc.; and Z containing F, OH, etc.; a Prussian blue analogue material with a cubic framework structure NaM2(CN)6 (M selected from transition metals); and an additive such as a conductive agent and a binder. The conductive agent includes, but is not limited to, known conductive agents such as carbon nanotubes and acetylene black. The binder includes, but is not limited to, known binders such as polyvinylidene fluoride. The mass ratio of the positive electrode active material, conductive agent, and binder adopts a ratio known in the art, for example, a ratio of (96-98):(1-1.5):(1-3). The thickness of one side of the positive electrode active material layer adopts a conventional thickness in the art, for example, 50-250 μm.

[0031] In a sodium-ion battery, the negative electrode sheet includes a negative electrode active material layer. This layer comprises a negative electrode active material, which includes one or more of the following: hard carbon, graphite, metallic sodium, metal oxides, alloys, and phosphorus compounds, capable of intercalating and deintercalating active sodium ions. The negative electrode active material is selected from materials known in the art. The thickness of the negative electrode active material layer on one side is a conventional thickness in the art, for example, 10-200 μm. Optionally, the negative electrode active material layer includes conductive agents, binders, and other additives. All additives are used in amounts known in the art, and this invention does not limit their application.

[0032] In sodium-ion batteries, the polymer electrolyte includes at least one of PEO, PAN, PMMA, PVA, PVP, PVDF, PVDF-HFP, PPC, PEC, PEDGA, PDMS, succinate (SN), and polyethylene glycol (PEG); the oxide electrolyte includes Na3Zr2Si2PO4. 12 Sodium superionic conductors such as Na3Ti2(PO4)3 (NASICON); halide electrolytes include Na 3-x M 1-x Zr x Cl6; where M is one or more transition metal elements or lanthanide elements; the value of x ranges from 0 to x < 1; sulfide electrolytes include crystalline Na3PS4 and crystalline Na 10 GeP2S 12 Novel sulfide glass-ceramic solid electrolyte Na3P 1-x As x S4, where 0 <x<1。

[0033] The technical solution of this invention has the following advantages:

[0034] 1. The present invention provides a material for improving the interfacial performance between solid electrolyte and electrode in solid-state batteries, comprising an ethylene-vinyl acetate-grafted maleic anhydride polymer and an oxide; the oxide comprising alumina and / or silicon oxide. When this material is applied to solid-state batteries, it can significantly improve the compatibility, interfacial thermal stability, and structural stability of the electrode and solid electrolyte. Modifying the ethylene-vinyl acetate-grafted maleic anhydride polymer (MAH-g-EVA) with alumina and / or silicon oxide, utilizing the unique structure and properties of MAH-g-EVA, can effectively improve the surface properties of these two incompatible materials, the solid electrolyte and the electrode, facilitating uniformity and high performance at the interface. Alumina and / or silicon oxide can also address the defects of low mechanical strength and poor stability at the solid electrolyte and electrode interface, preventing MAH-g-EVA interface cracking under pressure, thereby improving interfacial mechanical stability.

[0035] Applying MAH-g-EVA modified with nano-oxide to solid-state batteries offers several advantages. First, it enables micron-level filling of the electrode-solid electrolyte interface, significantly increasing the interfacial contact area to over 80%. This significantly improves upon the small solid-solid contact area in existing solid-state batteries, mitigating issues such as high interfacial impedance and limited lithium-ion transport efficiency caused by poor contact. Second, the modified EVA, specifically MAH-g-EVA, exhibits excellent elastic deformation (elongation at break > 300%), accommodating the volume expansion of the electrode material during charging and discharging, thus mitigating the deterioration of interfacial performance and battery life due to volume expansion mismatch. Third, it forms a chemically inert insulating layer between the electrode and solid electrolyte layers, suppressing side reactions and lithium dendrite growth, and reducing the loss of active lithium ions. The combination of alumina and / or silicon oxide with MAH-g-EVA creates a "rigid-flexible" effect, improving interfacial contact while maintaining the stability of the interfacial layer and preventing crack formation. Attached Figure Description

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 This is a partial structural schematic diagram of the solid-state battery in Embodiment 1 of the present invention;

[0038] Figure 2 This is a SEM image of the interface between the positive electrode and the solid electrolyte layer in Example 1.

[0039] Figure 3 The image shows the SEM morphology of the interface between the positive electrode and the solid electrolyte layer in Comparative Example 1.

[0040] Figure label:

[0041] 1-Positive electrode current collector; 2-Positive electrode active material layer; 3-First interface layer; 4-Solid electrolyte layer; 5-Second interface layer; 6-Negative electrode current collector; 7-Negative electrode active material layer. Detailed Implementation

[0042] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0043] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0044] The following embodiments and comparative examples illustrate the improved solid-state battery fabrication method, which includes: preparing a positive electrode, a negative electrode, a material for improving the interface performance between the solid electrolyte and the electrode in the solid-state battery (modified EVA film), and a solid electrolyte layer; stacking the positive electrode, modified EVA film (first interface layer), solid electrolyte layer, modified EVA film (second interface layer), and negative electrode in that order; preheating to 80-100°C; hot-pressing composite at 0.1-1 MPa and 100-120°C; cooling and shaping at 0.1-1 MPa and 20-30°C; and encapsulation to obtain the solid-state battery. During the fabrication of the solid-state battery, the pressure and temperature are only subject to fluctuations and must meet the above-mentioned ranges.

[0045] Example 1

[0046] This embodiment provides a material for improving the interface performance between solid electrolyte and electrode in solid-state batteries, comprising an ethylene-vinyl acetate-grafted maleic anhydride polymer (MAH-g-EVA, weight-average molecular weight of 1000, manufactured by KOAS Chemical Co., Ltd.) in a mass ratio of 98.5:1.5 and alumina, wherein the median particle size D50 of the alumina is 40 nm, the grafting rate of maleic anhydride in MAH-g-EVA is 5 mol%, and the mass content of vinyl acetate in ethylene-vinyl acetate (EVA) is 25%.

[0047] This embodiment provides a solid-state battery; a partial structural schematic diagram of the solid-state battery is shown below. Figure 1 ,include:

[0048] Positive electrode sheet: includes a positive current collector 1 and a positive active material layer 2 located on its two surfaces. The thickness of the positive active material layer on one side is 80 μm. The positive active material layer includes a nickel-cobalt-manganese ternary material active material, a conductive agent carbon nanotube, and a binder polyvinylidene fluoride in a mass ratio of 96:1.5:2.5.

[0049] Negative electrode sheet: includes a negative electrode current collector 6 and a negative electrode active material layer 7 located on its two surfaces. The thickness of the negative electrode active material layer on one side is 20 μm, and the negative electrode active material layer includes lithium metal.

[0050] Solid electrolyte layer 4: 30 μm thick, consisting of Li6PS5Cl in a mass ratio of 98:2 and polytetrafluoroethylene as a binder.

[0051] First interface layer 3: Composed of the above-mentioned materials; disposed between the positive electrode and the solid electrolyte layer 4, with a thickness of 0.8 μm.

[0052] The second interface layer 5 consists of the materials described above and is disposed between the negative electrode and the solid electrolyte layer 4, with a thickness of 3 μm.

[0053] Example 2

[0054] This embodiment provides a material for improving the interface performance between the solid electrolyte and the electrode in a solid-state battery, which is the same as in Embodiment 1.

[0055] This embodiment provides a solid-state battery, such as Figure 1 As shown, it includes:

[0056] Positive electrode sheet: includes a positive current collector and a positive active material layer on its two surfaces. The thickness of the positive active material layer on one side is 100μm. The positive active material layer includes active material lithium iron phosphate material, conductive agent acetylene black, conductive agent carbon nanotube and binder polyvinylidene fluoride in a mass ratio of 96.5:0.8:0.2:2.5.

[0057] Negative electrode sheet: includes a negative current collector and a negative active material layer located on its two surfaces. The thickness of the negative active material layer on one side is 25 μm, and the negative active material layer includes lithium metal.

[0058] Solid electrolyte layer: 30 μm thick, consisting of Li6PS5Cl in a mass ratio of 98:2 and polytetrafluoroethylene as a binder.

[0059] First interface layer: composition is the same as in Example 1; disposed between the positive electrode and the solid electrolyte layer, with a thickness of 1 μm.

[0060] Second interface layer: composition is the same as in Example 1; disposed between the negative electrode and the solid electrolyte layer, with a thickness of 5 μm.

[0061] Example 3

[0062] This embodiment provides a material for improving the interface performance between the solid electrolyte and the electrode in a solid-state battery, which is the same as in Embodiment 1.

[0063] This embodiment provides a solid-state battery, such as Figure 1 As shown, it includes:

[0064] Positive electrode sheet: includes a positive current collector and positive active material layers located on two surfaces. The thickness of the positive active material layers is 100 μm, and the positive active material layers consist of layered transition metal oxide Na with a mass ratio of 96:1.5:2.5. 0.696 Ni 0.329 Mn 0.671 O2, conductive agent carbon nanotubes, adhesive polyvinylidene fluoride.

[0065] Negative electrode sheet: includes a negative electrode current collector and a negative electrode active material layer located on two surfaces. The thickness of the negative electrode active material layer is 30μm. The negative electrode active material layer includes a negative electrode active material hard carbon material, a conductive agent carbon nanotube, and a binder polyvinylidene fluoride in a mass ratio of 95:2.5:2.5.

[0066] Solid electrolyte layer: 15 μm thick, consisting of Na3Zr2Si2PO4 in a mass ratio of 15:85. 12 With polyoxyethylene (PEO).

[0067] First interface layer: composition is the same as in Example 1; disposed between the positive electrode and the solid electrolyte layer, with a thickness of 3 μm.

[0068] Second interface layer: composition is the same as in Example 1; disposed between the negative electrode and the solid electrolyte layer, with a thickness of 8 μm.

[0069] Example 4

[0070] This embodiment provides a material for improving the interface performance between solid electrolyte and electrode in solid-state batteries, comprising an ethylene-vinyl acetate-grafted maleic anhydride polymer (MAH-g-EVA, molecular weight 1000) in a mass ratio of 95:5 and alumina, wherein the median particle size D50 of the alumina is 40 nm, the grafting rate of maleic anhydride in MAH-g-EVA is 8 mol%, and the mass content of vinyl acetate in ethylene-vinyl acetate (EVA) is 25%.

[0071] This embodiment provides a solid-state battery, such as Figure 1 As shown, it includes:

[0072] Positive electrode sheet: includes a positive current collector and a positive active material layer on its two surfaces. The thickness of the positive active material layer is 100μm. The positive active material layer includes a nickel-cobalt-manganese ternary material active material with a mass ratio of 96:1.5:2.5, a conductive agent carbon nanotube, and a binder polyvinylidene fluoride.

[0073] Negative electrode sheet: includes a negative current collector and a negative active material layer on its two surfaces. The thickness of the negative active material layer is 20 μm. The negative active material layer includes active material silicon carbon, conductive agent carbon nanotubes, and binder polyvinylidene fluoride in a mass ratio of 95:2.5:2.5.

[0074] Solid electrolyte layer: 30 μm thick, consisting of Li6PS5Cl in a mass ratio of 98:2 and polytetrafluoroethylene as a binder.

[0075] First interface layer: Composed of the above-mentioned materials; disposed between the positive electrode and the solid electrolyte layer, with a thickness of 0.5 μm.

[0076] Second interface layer: Composed of the above-mentioned materials; disposed between the negative electrode and the solid electrolyte layer, with a thickness of 2μm.

[0077] Example 5

[0078] This embodiment provides a material for improving the interface performance between solid electrolyte and electrode in solid-state batteries, comprising an ethylene-vinyl acetate-grafted maleic anhydride polymer (MAH-g-EVA, molecular weight 1000) in a mass ratio of 98:2 and silicon oxide, wherein the median particle size of the silicon oxide is 50 nm, the grafting rate of maleic anhydride in MAH-g-EVA is 2 mol%, and the mass content of vinyl acetate in EVA is 25%.

[0079] This embodiment provides a solid-state battery. The first interface layer and the second interface layer use the materials described above, and the rest is the same as in Embodiment 1.

[0080] Example 6

[0081] This embodiment provides a material for improving the interface performance between solid electrolyte and electrode in solid-state batteries. The material comprises an ethylene-vinyl acetate-grafted maleic anhydride polymer (MAH-g-EVA, molecular weight 1500, manufactured by KOS Chemical Co., Ltd.) in a mass ratio of 99.5:0.5 and silicon dioxide. The median particle size D50 of the silicon dioxide is 20 nm. The grafting rate of maleic anhydride in MAH-g-EVA is 15 mol%, and the mass content of vinyl acetate in EVA is 35%.

[0082] This embodiment provides a solid-state battery, including:

[0083] Positive electrode sheet: includes a positive current collector and a positive active material layer on its two surfaces. The thickness of the positive active material layer is 80 μm. The positive active material layer includes a nickel-cobalt-manganese ternary material active material with a mass ratio of 96:1.5:2.5, a conductive agent carbon nanotube, and a binder polyvinylidene fluoride.

[0084] Negative electrode sheet: includes a negative electrode current collector and a negative electrode active material layer located on its two surfaces. The thickness of the negative electrode active material layer is 20 μm, and the negative electrode active material layer includes lithium metal.

[0085] Solid electrolyte layer: 30 μm thick, consisting of Li6PS5Cl in a mass ratio of 98:2 and polytetrafluoroethylene as a binder.

[0086] First interface layer: Composed of the above-mentioned materials; disposed between the positive electrode and the solid electrolyte layer, with a thickness of 0.6 μm.

[0087] Second interface layer: Composed of the above-mentioned materials; disposed between the negative electrode and the solid electrolyte layer, with a thickness of 2.5 μm.

[0088] Comparative Example 1

[0089] This comparative example provides a solid-state battery, which differs from the solid-state battery of Example 1 in that it does not contain a first interface layer and a second interface layer.

[0090] Comparative Example 2

[0091] This comparative example provides an interface material comprising an ethylene-vinyl acetate-grafted maleic anhydride polymer (MAH-g-EVA, molecular weight 1000), wherein the grafting rate of maleic anhydride in MAH-g-EVA is 5 mol% and the mass content of vinyl acetate in EVA is 25%.

[0092] This comparative example provides a solid-state battery, which differs from the solid-state battery of Example 1 in that the composition of the first interface layer and the second interface layer adopts the interface material provided in this comparative example.

[0093] Comparative Example 3

[0094] This comparative example provides an interface material comprising ethylene-vinyl acetate and alumina in a mass ratio of 98.5:1.5, wherein the median particle size D50 of the alumina is 40 nm.

[0095] This comparative example provides a solid-state battery, which differs from the solid-state battery of Example 1 in that the composition of the first interface layer and the second interface layer adopts the interface material provided in this comparative example.

[0096] Test case

[0097] This test case provides performance tests for various embodiments and comparative solid-state batteries, as detailed below:

[0098] Test method for interface contact: Disassemble the solid-state battery, remove the solid electrolyte layer on the surface of the positive electrode, and observe the surface morphology of the positive electrode. Directly observe the solid-solid interface morphology between the positive electrode and the solid electrolyte layer in the solid-state batteries of Example 1 and Comparative Example 1 using a scanning electron microscope to evaluate the contact state. Figure 2 This is a morphology diagram of the interface between the positive electrode and the solid electrolyte layer in Example 1. Figure 3 The figure shows the interface morphology of the positive electrode and the solid electrolyte layer in Comparative Example 1. As can be seen from the figure, the surface of the positive electrode in Example 1 is in a monolithic state with no obvious boundary, while the positive electrode in Comparative Example 1 has obvious particles, indicating that the interface contact between the positive electrode and the solid electrolyte layer of the present invention is better.

[0099] Method for testing ionic conductivity: Following the solid-state battery structures of each embodiment and comparative example, a first interface layer, a solid electrolyte layer, and a second interface layer are stacked and pressed into a disc with a thickness of 50 μm and a diameter of 16 mm. The disc surface is then sputter-coated with gold. The impedance value R is measured using a high-frequency impedance meter (>10 MHz). The conductivity is then calculated using the electrolyte thickness T and the test area A. The formula for calculating ionic conductivity (σ) is σ = T / (R × A). It should be noted that when the solid-state battery lacks an interface layer, the ionic conductivity of the solid electrolyte layer is directly tested.

[0100] Test method for volume expansion: At room temperature, using a battery thickness gauge and pressure control system, record the thickness change of the solid-state battery from 0% to 100% charge during charging, and calculate the volume expansion rate. The thickness at 0% charge is denoted as h1, and the thickness at 100% charge is denoted as h2. The formula for calculating the volume expansion rate is: (h2-h1) / h1×100%.

[0101] Fast charging performance testing method: Solid-state batteries are charged and discharged at room temperature using a 3C charging rate and a 1C discharging rate for 3 cycles, and then charged and discharged at a 0.5C charging rate and a 1C discharging rate for 3 cycles. The average value of the 3C and 0.5C charging capacity is calculated respectively. The capacity retention rate is calculated as: average value of 3C charging capacity / average value of 0.5C charging capacity × 100% to evaluate fast charging performance.

[0102] Cycle life testing method: Solid-state batteries are subjected to charge-discharge cycles (0.5C charge – 1C discharge) at a constant current density at room temperature for n cycles, until the battery capacity retention is ≤80%. The number of cycles is recorded to evaluate the battery's cycle life. The capacity retention rate is calculated as: (n-cycle discharge capacity / 1-cycle discharge capacity) × 100%.

[0103] The test results are shown in Table 1.

[0104] Table 1 Test Results

[0105] Example Ionic conductivity Volume expansion Fast charging performance Cycle life Example 1 2.85 mS / cm 6.6％ 90％ 1000 times Example 2 2.32 mS / cm 6.7％ 88％ 1500 times Example 3 1.26 mS / cm 5.3％ 85％ 1300 times Example 4 2.44 mS / cm 9.1％ 89％ 1000 times Example 5 3.03 mS / cm 6.4％ 91％ 1100 times Example 6 4.77 mS / cm 6.1％ 94％ 1200 times Comparative Example 1 0.32mS / cm 8.5％ 77％ 600 times Comparative Example 2 0.89mS / cm 7.9％ 81％ 800 times Comparative Example 3 1.13 mS / cm 7.6％ 84％ 1000 times

[0106] Combining Table 1 and Figure 2 This indicates that when the material provided by this invention, which improves the interface performance between the solid electrolyte and the electrode in a solid-state battery, is applied to a solid-state battery, it can improve the compatibility between the electrode and the solid electrolyte layer, improve the interface performance, and thus improve the ionic conductivity of the solid-state battery, reduce charge and discharge volume expansion, and extend battery life.

[0107] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A material for improving the interfacial performance between solid electrolyte and electrode in solid-state batteries, characterized in that, include: Ethylene-vinyl acetate grafted with maleic anhydride polymer and oxide; said oxide includes aluminum oxide and / or silicon oxide.

2. The material according to claim 1, characterized in that, The weight-average molecular weight of the ethylene-vinyl acetate grafted maleic anhydride polymer is 800-3000. And / or, the median particle size D50 of the oxide is 1-50 nm.

3. The material according to claim 1 or 2, characterized in that, The grafting rate of maleic anhydride in the ethylene-vinyl acetate-grafted maleic anhydride polymer is 2-15 mol.

4. The material according to claim 1 or 2, characterized in that, The vinyl acetate content in the ethylene-vinyl acetate mixture is 20-40% by mass.

5. The material according to claim 1 or 2, characterized in that, The mass content of the oxide in the material is 0.1-5%.

6. A solid-state battery, characterized in that, It includes a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode; A first interface layer is provided between the positive electrode sheet and the solid electrolyte layer, and the first interface layer includes the material described in any one of claims 1-5; And / or, a second interface layer is provided between the negative electrode and the solid electrolyte layer, the second interface layer comprising the material described in any one of claims 1-5.

7. The solid-state battery according to claim 6, characterized in that, The thickness of the first interface layer is less than the thickness of the second interface layer.

8. The solid-state battery according to claim 7, characterized in that, The thickness of the first interface layer is 0.1-3 μm; And / or, the thickness of the second interface layer is 1-10 μm.

9. The solid-state battery according to any one of claims 6-8, characterized in that, The solid-state battery includes a lithium-ion battery or a sodium-ion battery.

10. The solid-state battery according to any one of claims 6-9, characterized in that, The solid electrolyte layer includes an electrolyte, which includes one or more of polymer electrolytes, halide electrolytes, oxide electrolytes, and sulfide electrolytes. Preferably, the mass content of the electrolyte in the solid electrolyte layer is 50-100%.

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