Composite interface layer, preparation method thereof and all-solid-state battery

Abstract

The invention discloses a composite interface layer, a preparation method thereof and an all-solid-state battery, belongs to the technical field of all-solid-state batteries, and solves the problems that the all-solid-state battery needs to operate under relatively high restraint pressure, and the battery performance is quickly reduced. The composite interface layer comprises a functional layer and a stress buffer layer, the functional layer comprises the following components in percentage by mass: 10%-50% of a ceramic fast lithium ion conductor, 20%-70% of an elastic polymer A and 0.1%-30% of a lithium salt A, the Poisson ratio of the functional layer is 0.01-0.3, and the Young modulus of the functional layer is 0.1-2 GPa; the stress buffer layer comprises the following components in percentage by mass: 65%-90% of an elastic polymer B, 1%-15% of a plasticizer and 0.1%-20% of lithium salt B, the Poisson ratio of the stress buffer layer is 0.2-0.5, and the Young modulus of the stress buffer layer is 0.01-0.5 GPa; and the elastic polymer B contains dynamic reversible chemical bonds.

Description

Technical Field

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

[0002] The ever-increasing demand for battery life is pushing existing liquid lithium-ion batteries close to their energy density limits, and further changes to the material system would pose significant safety risks. Compared to liquid batteries, all-solid-state lithium batteries utilize a non-flammable solid electrolyte instead of a liquid electrolyte and can be paired with cathode and anode materials with higher specific energy. Therefore, they offer significant advantages in energy density and safety, potentially significantly improving the battery life of consumer electronics and electric vehicles.

[0003] However, during long-term operation, all-solid-state batteries experience continuous volume contraction and expansion of the positive and negative electrodes, which can easily lead to gaps at the interface between the electrode and the electrolyte membrane. Internal stress accumulated within the electrodes can also cause microcracks at the interface. This phenomenon can cause localized interfacial contact failure, leading to increased local impedance, which in turn reduces the battery's charge and discharge performance and cycle life, and in severe cases, can lead to all-solid-state battery failure.

[0004] One of the existing solutions is to operate the all-solid-state battery under a certain restraint pressure in order to eliminate the problem of interface contact failure caused by volume change. However, this method requires a larger restraint pressure (≥20Mpa) and still cannot solve the problem of internal stress accumulation. The larger operating pressure will aggravate the internal microcracks of the all-solid-state battery, which may eventually lead to a rapid decline in battery performance. Providing an electrode / electrolyte membrane interface buffer layer can also improve the interface contact failure problem to a certain extent and reduce the gap at the interface. However, the interface buffer layer of the prior art will usually be damaged in actual use due to the influence of internal stress and volume change, thereby losing its effect, resulting in a rapid decline in battery performance. Summary of the Invention

[0005] One of the purposes of this application is to provide a composite interface layer to solve the problem in the prior art that all-solid-state batteries need to operate under a larger restraint pressure, and the interface layer between the negative electrode sheet and the solid electrolyte is easily caused to fall off and microcracks due to volume changes and stress concentration, thereby causing rapid decline in battery performance; the second purpose is to provide a method for preparing a composite interface layer; and the third purpose is to provide an all-solid-state battery.

[0006] In order to achieve the above objectives, the technical solutions adopted in this application are as follows:

[0007] In a first aspect, the present application provides a composite interface layer, comprising a functional layer and a stress buffer layer;

[0008] The functional layer comprises, by mass percentage, 10%-50% of a ceramic fast lithium ion conductor, 20%-70% of an elastic polymer A, and 0.1%-30% of a lithium salt A. The Poisson's ratio of the functional layer is 0.01-0.3, and the Young's modulus of the functional layer is 0.1-2 GPa.

[0009] The stress buffer layer comprises, by mass percentage, 65%-90% of an elastic polymer B, 1%-15% of a plasticizer, and 0.1%-20% of a lithium salt B. The Poisson's ratio of the stress buffer layer is 0.2-0.5, and the Young's modulus of the stress buffer layer is 0.01-0.5 GPa.

[0010] The elastic polymer B contains dynamically reversible chemical bonds.

[0011] In one possible embodiment, the thickness of the functional layer is 0.1-0.5 μm;

[0012] In a possible implementation manner, the stress buffer layer has a thickness of 0.4-4.5 μm.

[0013] In one possible embodiment, the ceramic fast lithium ion conductor includes Li 1.3 Al 0.3 Ti 1.7 (PO4)3、Li7La3Zr2O 12 、Li 6.75 La3Zr 1.75 Nb 0.25 O 12 、Li 6-y PS5Cl 1+y 、Li 10 SnP2S 12 At least one of , where 0≤y≤1;

[0014] In a possible implementation, the particle size D50 of the ceramic fast lithium ion conductor is 50-500 nm.

[0015] In a possible implementation, the elastic polymer A includes at least one of polycaprolactone, polyurethane, polythiourethane, polyethylene glycol-polycarbonate copolymer, and polydimethylsiloxane.

[0016] In one possible embodiment, the elastic polymer B includes at least one of a polycarbonate polymer, a polythiourethane polymer, and a polydimethylsiloxane polymer;

[0017] In one possible embodiment, the dynamically reversible chemical bond includes at least one of a disulfide bond, a borate bond, and a Diels-Alder bond.

[0018] In one possible embodiment, the plasticizer raw material includes at least one of vinylene carbonate, fluoroethylene carbonate, succinonitrile, polyethylene glycol diacrylate, polyethylene glycol dimethyl ether, polyethylene glycol methacrylate, polyethylene glycol dimethacrylate, 1,3-dioxolane, and tetrahydrofuran;

[0019] In one possible implementation, the molecular weight of the plasticizer raw material is ≤1000 g / mol.

[0020] In one possible embodiment, the lithium salt A includes at least one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), and lithium difluorooxalatoborate;

[0021] In a possible embodiment, the lithium salt B includes at least one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), and lithium difluorooxalatoborate.

[0022] In a possible implementation manner, based on the mass of the stress buffer layer, the stress buffer layer further includes 0.1%-5% of a nano-enhancer.

[0023] In one possible embodiment, the nano-reinforcement agent includes at least one of MXene, boron nitride nanosheets, molybdenum disulfide nanosheets, titanium dioxide nanosheets, and graphene oxide, and its aspect ratio is ≥30.

[0024] In a second aspect, the present application provides a method for preparing the composite interface layer, comprising the following steps:

[0025] S1, mixing a ceramic fast lithium ion conductor, an elastic polymer A, a lithium salt A, and a first organic solvent to obtain a functional layer slurry, and using the functional layer slurry to prepare a functional layer on at least one side of a negative electrode sheet;

[0026] S2. Mixing the elastic polymer B, the plasticizer raw material, the initiator, the lithium salt B, and the second organic solvent to obtain a stress buffer layer slurry, coating the stress buffer layer slurry on the functional layer, and heating and curing the mixture to obtain the composite interface layer.

[0027] In one possible embodiment, in S2, the curing temperature is 50-150° C., and the curing time is 10-60 min;

[0028] In one possible embodiment, in S1, the ceramic fast lithium ion conductor, the elastic polymer A, the lithium salt A, and the first organic solvent are mixed for 1 to 5 hours;

[0029] In one possible embodiment, the initiator includes at least one of diisopropyldicarbonamide, lithium hexafluorophosphate, lithium tetrafluoroborate, phenyllithium, azobisisobutyronitrile, and Lewis acidic dimetal halide salts;

[0030] In one possible embodiment, the amount of the initiator added is 0.1%-1% of the sum of the mass of the elastic polymer B, the plasticizer raw material, the initiator, and the lithium salt B;

[0031] In a possible embodiment, the first organic solvent and the second organic solvent independently include at least one of ethylene carbonate, propylene carbonate, N-methylpyrrolidone, tetrahydrofuran, ethylene glycol dimethyl ether, acetonitrile, anisole, and p-xylene.

[0032] In a third aspect, the present application provides an all-solid-state battery comprising a positive electrode sheet, a negative electrode sheet and a solid electrolyte membrane, wherein at least one interface between the negative electrode sheet and the electrolyte membrane is provided with the composite interface layer or the composite interface layer prepared according to the preparation method.

[0033] The composite interface layer can spontaneously repair the micro cracks in the pole piece and the damage in the interface layer under heating conditions of 40-100°C.

[0034] Beneficial effects of this application:

[0035] The composite interface layer of the present application includes a functional layer and a stress buffer layer; the functional layer includes, by mass percentage, 10%-50% of a ceramic fast lithium ion conductor, 20%-70% of an elastic polymer A, and 0.1%-30% of a lithium salt A. The Poisson's ratio of the functional layer is 0.01-0.3, and the Young's modulus of the functional layer is 0.1-2GPa; the stress buffer layer includes, by mass percentage, 65%-90% of an elastic polymer B, 1%-15% of a plasticizer, and 0.1%-20% of a lithium salt B. The Poisson's ratio of the stress buffer layer is 0.2-0.5, and the Young's modulus of the stress buffer layer is 0.01-0.5GPa; the elastic polymer B contains dynamically reversible chemical bonds.

[0036] The present application provides a composite interface layer with adaptive self-healing function, which is arranged between the negative electrode sheet and the electrolyte membrane of the battery. The composite interface layer is composed of a functional layer and a stress buffer layer to form a secondary gradient structure. When a gap is generated due to inconsistent volume changes of the positive and negative electrodes, the functional layer can work together with the stress buffer layer to adaptively deform and fill the interface gap, thereby preventing the increase of battery impedance and the disconnection of ion paths, and reducing the increase of polarization of the battery during use. Thus, under reduced external restraining pressure, the interface peeling and microcracks caused by volume change and stress concentration between the negative electrode sheet and the electrolyte membrane are effectively alleviated. At the same time, the composite interface layer of the present application also has excellent self-healing ability. When the interface is subjected to stress impact or local stress concentration is generated inside the battery, the stress buffer layer can effectively relieve stress and prevent the interface layer from being damaged due to excessive stress. If microcracks appear in the interface layer during use, the self-healing function can spontaneously repair the microcracks during self-heating during the charge and discharge process or under certain temperature conditions, thereby preventing the microcracks from further expanding and preventing damage to the interface layer, thereby improving the first effect and cycle performance of the battery. The composite interface layer of this application can achieve self-healing function at 40-100°C, which enables the battery to operate normally in a wider range of temperature environments. In addition, under complex charging and discharging conditions and self-heating, the composite interface layer can adaptively adjust the interface state to ensure stable battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the all-solid-state battery structure of Example 1 of the present application;

[0038] Figure 2 This is a top view of the composite interface layer of Example 1 of the present application.

[0039] Reference numerals:

[0040] 1-Negative electrode sheet; 11-Negative electrode current collector; 12-Negative electrode active material layer; 2-Positive electrode sheet; 21-Positive electrode current collector; 22-Positive electrode active material layer; 3-Solid electrolyte membrane; 4-Composite interface layer; 41-Functional layer; 411-Elastic polymer matrix A; 412-Ceramic fast lithium ion conductor; 42-Stress buffer layer; 421-Elastic polymer matrix B. DETAILED DESCRIPTION

[0041] The following will describe the embodiments of the present application with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand the other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for the purpose of illustrating the present application and are not intended to limit the scope of protection of the present application.

[0042] In a first aspect, the present application provides a composite interface layer, comprising a functional layer and a stress buffer layer;

[0043] The functional layer comprises, by mass percentage, 10%-50% of a ceramic fast lithium ion conductor, 20%-70% of an elastic polymer A, and 0.1%-30% of a lithium salt A. The Poisson's ratio of the functional layer is 0.01-0.3, and the Young's modulus of the functional layer is 0.1-2 GPa.

[0044] The stress buffer layer comprises, by mass percentage, 65%-90% of an elastic polymer B, 1%-15% of a plasticizer, and 0.1%-20% of a lithium salt B. The Poisson's ratio of the stress buffer layer is 0.2-0.5, and the Young's modulus of the stress buffer layer is 0.01-0.5 GPa.

[0045] The elastic polymer B contains dynamically reversible chemical bonds.

[0046] Dynamically reversible chemical bonds refer to a type of chemical bonds that can be reversibly broken and recombined under certain external stimuli (such as heat, light, pH, mechanical force, etc.).

[0047] In the present application, the composite interface layer refers to an interface layer formed by two or more different composition structures, the purpose of which is to distinguish different functional areas of the interface layer, and it is expected to have a targeted design effect for the different changes of the electrode and the solid electrolyte membrane during the charge and discharge process of the all-solid-state battery. Among them, the functional layer is based on an elastic polymer A and a ceramic fast lithium ion conductor as a filler. On the one hand, it ensures that it has a good and uniform lithium ion transmission path to facilitate the uniform insertion and extraction of lithium on the electrode; on the other hand, it can provide good support and deformation capabilities, while alleviating volume changes and preventing damage to the interface layer and the electrolyte membrane due to particle crushing or lithium dendrite precipitation. The stress buffer layer is composed of an elastic polymer B, a plasticizer and a lithium salt. The dynamic reversible chemical bonds of the elastic polymer B can break and reorganize at a specific temperature to achieve self-healing. The plasticizer can lower the glass transition temperature of the elastic polymer and improve the chain segment mobility, thereby enhancing the self-healing efficiency. The presence of lithium salt in the two layers is to improve ionic conductivity. The content of lithium salt A in the functional layer is controlled at 0.1%-30% to improve ion transmission, and the content of lithium salt B in the stress buffer layer is controlled at 0.1%-20%, which can take into account both ionic conduction and elasticity of the stress buffer layer.

[0048] Poisson’s ratio refers to the ratio of the absolute value of the lateral normal strain to the axial normal strain when the material is under unidirectional compression or tension. It is an elastic parameter that reflects the lateral deformation of the material. The present application controls the Poisson’s ratio of the functional layer close to the electrode side to 0.01-0.3, which can ensure that the functional layer is not prone to lateral deformation during the volume change process, thereby ensuring the uniformity of the lithium ion flow on the electrode surface and the anti-dendrite ability, preferably within 0.05-0.25. The stress buffer layer on the solid electrolyte membrane side has a higher Poisson’s ratio of 0.2-0.5, which can release the internal stress accumulated in the interface and the pole piece during the volume transformation through multi-directional deformation, and inhibit the generation of interface separation and microcracks, preferably 0.25-0.4.

[0049] In a specific embodiment, the Poisson's ratio of the stress buffer layer is greater than or equal to the Poisson's ratio of the functional layer.

[0050] Young's modulus, also known as elastic modulus, refers to the ratio of axial stress to axial strain of a material during the elastic deformation stage, and is an indicator of the ease of elastic deformation of a material. The present application controls the degree of deformation by controlling the Young's modulus of the functional layer close to the electrode side to 0.1-2GPa. For example, it can be 0.1GPa, 0.2GPa, 0.5GPa, 0.8GPa, 1.0GPa, 1.2GPa, 1.5GPa, 1.7GPa, 2.0GPa or any value between any two of the above points, preferably within 0.5-2GPa. The Young's modulus of the stress buffer layer close to the solid electrolyte membrane is controlled to 0.01-0.5GPa to ensure its buffering effect. For example, it can be 0.01GPa, 0.1GPa, 0.2GPa, 0.3GPa, 0.4GPa, 0.5GPa or any value between any two of the above points, preferably within 0.2-0.5GPa.

[0051] In a specific embodiment, the thickness of the composite interface layer is 0.5-5 μm, preferably 0.8-3 μm.

[0052] In a possible embodiment, the thickness of the functional layer is 0.1-0.5 μm, and illustratively, it can be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, or any value between any two of the above points, preferably 0.3-0.5 μm.

[0053] In a possible embodiment, the thickness of the stress buffer layer is 0.4-4.5 μm, for example, 0.4 μm, 1 μm, 2 μm, 3 μm, 4 μm, or any value between any two of the above values, preferably 0.5-3.5 μm.

[0054] The thicker the composite interface layer, the more it helps the solid-state battery withstand uniform pressure and absorb volume changes during cycling. The stress buffer layer primarily plays a role in deformation. However, the composite interface layer's lithium-ion conductivity is inferior to that of the solid electrolyte membrane, and the thicker it is, the lower the cell energy density. Therefore, the composite interface layer is controlled within the aforementioned thickness range to ensure both its improvement and the cell energy density.

[0055] In one possible embodiment, the ceramic fast lithium ion conductor includes Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP), Li7La3Zr2O 12 (LLZO), Li 6.75 La3Zr 1.75 Nb 0.25 O 12 (LLZNO), Li 6-yPS5Cl 1+y (LPSC), Li 10 SnP2S 12 At least one of (LSPS), where 0≤y≤1;

[0056] In one possible embodiment, the particle size D50 of the ceramic fast lithium ion conductor is 50-500 nm, preferably 100-400 nm. Within this particle size range, the ceramic fast lithium ion conductor can be evenly dispersed and improve the ionic conductivity and mechanical properties of the film layer.

[0057] In one possible embodiment, the ionic conductivity of the ceramic fast lithium ion conductor is ≥4×10 -4 S / cm.

[0058] In one possible embodiment, the elastic polymer A includes at least one of polycaprolactone, polyurethane, polythiourethane, polyethylene glycol-polycarbonate copolymer, and polydimethylsiloxane;

[0059] In one possible implementation, the elastic polymer A has a glass transition temperature Tg ≤ -30°C.

[0060] In one possible embodiment, the elastic polymer B includes at least one of a polycarbonate polymer, a polythiourethane polymer, and a polydimethylsiloxane polymer;

[0061] In one possible embodiment, the dynamically reversible chemical bond includes at least one of a disulfide bond, a borate bond, and a Diels-Alder bond.

[0062] In one possible embodiment, the plasticizer raw material includes at least one of vinylene carbonate, fluoroethylene carbonate, succinonitrile, polyethylene glycol diacrylate, polyethylene glycol dimethyl ether, polyethylene glycol methacrylate, polyethylene glycol dimethacrylate, 1,3-dioxolane, and tetrahydrofuran;

[0063] In one possible embodiment, the molecular weight of the plasticizer raw material is ≤1000 g / mol, preferably ≤750 g / mol. Plasticizer raw materials with lower molecular weight can be better dispersed in the slurry and better improve the overall plasticity of the stress buffer layer after heating and curing.

[0064] In one possible embodiment, the lithium salt A includes at least one of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalatoborate) (LiBOB), and lithium difluorooxalatoborate (LiDFOB);

[0065] In a possible embodiment, the lithium salt B includes at least one of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalatoborate) (LiBOB), and lithium difluorooxalatoborate (LiDFOB).

[0066] In a possible implementation manner, based on the mass of the stress buffer layer, the stress buffer layer further includes 0.1%-5% of a nano-enhancer.

[0067] In one possible embodiment, the nano-reinforcement agent includes at least one of MXene, boron nitride nanosheets, molybdenum disulfide nanosheets, titanium dioxide nanosheets, and graphene oxide, and its aspect ratio is ≥30.

[0068] In a second aspect, the present application provides a method for preparing a composite interface layer, comprising the following steps:

[0069] S1, mixing a ceramic fast lithium ion conductor, an elastic polymer A, a lithium salt A, and a first organic solvent to obtain a functional layer slurry, and using the functional layer slurry to prepare a functional layer on at least one side of a negative electrode sheet;

[0070] S2. Mixing the elastic polymer B, the plasticizer raw material, the initiator, the lithium salt B, and the second organic solvent to obtain a stress buffer layer slurry, coating the stress buffer layer slurry on the functional layer, and heating and curing the mixture to obtain the composite interface layer.

[0071] In one possible embodiment, in S2, the curing temperature is 50-150° C., preferably 60-120° C., and the curing time is 10-60 min, preferably 30-60 min;

[0072] In one possible embodiment, in S1, the ceramic fast lithium ion conductor, the elastic polymer A, the lithium salt A, and the first organic solvent are mixed for 1 to 5 hours;

[0073] In one possible embodiment, in S1, the deposition voltage of the electrostatic spray method is 10-30 kV, and the ambient humidity is ≤15%;

[0074] In one possible embodiment, in S2, the coating method includes at least one of blade coating, spin coating, spray coating, and gravure coating;

[0075] In a possible implementation manner, the functional layer slurry has a mass solid content of 5% to 10%.

[0076] In a possible implementation manner, the weight solid content of the stress buffer layer slurry is 5% to 15%.

[0077] In one possible implementation, in S2, the stress buffer layer precursor slurry further includes an initiator;

[0078] In one possible embodiment, the initiator includes at least one of diisopropyldicarbonamide, lithium hexafluorophosphate, lithium tetrafluoroborate, phenyllithium, azobisisobutyronitrile, and Lewis acidic dimetal halide salts;

[0079] In one possible embodiment, the mass of the initiator is 0.1%-1%, preferably 0.3%-0.5%, of the mass of the stress buffer layer slurry excluding the organic solvent;

[0080] In a possible embodiment, the first organic solvent and the second organic solvent independently include at least one of ethylene carbonate, propylene carbonate, N-methylpyrrolidone, tetrahydrofuran, ethylene glycol dimethyl ether, acetonitrile, anisole, and p-xylene.

[0081] In one possible embodiment, in S1, the functional layer is prepared by electrostatic spraying. Optionally, the deposition voltage of the electrostatic spraying method is 10-30 kV, and the ambient humidity is ≤15%;

[0082] In one possible implementation, in S2, the stress buffer layer is prepared by a coating method, and optionally, the coating method includes at least one of blade coating, spin coating, spray coating, and gravure coating;

[0083] In a third aspect, the present application provides an all-solid-state battery comprising a positive electrode sheet, a negative electrode sheet and a solid electrolyte membrane, wherein at least one interface between the negative electrode sheet and the electrolyte membrane is provided with the composite interface layer or the composite interface layer prepared according to the preparation method described in 1.

[0084] In a specific embodiment, the composite interface layer is provided at the interface between the negative electrode sheet and the solid electrolyte membrane.

[0085] In a specific embodiment, the portion of the composite interface layer close to the negative electrode sheet is a functional layer, and the portion of the composite interface layer close to the solid electrolyte membrane is a stress buffer layer.

[0086] In a specific embodiment, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on both sides of the positive electrode current collector. The positive electrode active material layer is primarily composed of the positive electrode active material and may also include components such as a conductive agent and a binder. Specifically, the conductive agent includes, but is not limited to, one or more of conductive carbon black, SuperP, acetylene black, Ketjen black, carbon nanofibers, and carbon nanotubes; the binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC-Na), polyvinyl pyrrolidone, polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), hydrogenated nitrile rubber (HNBR), polyacrylic acid (PAA), lithium polyacrylate (PAA-Li), hydrogenated styrene-butadiene block copolymer (SEBS), and polyisobutylene (PIB). The positive electrode active material may be selected from among those commonly used in the art, including, but not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate, lithium iron manganese phosphate, and lithium-rich manganese-based materials.

[0087] In a specific embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer mainly comprises a negative electrode active material and may also include components such as a conductive agent and a binder. Specifically, the negative electrode active material includes, but is not limited to, one or more of graphite, silicon carbon, silicon oxide, and elemental silicon; the conductive agent includes, but is not limited to, one or more of conductive carbon black, SuperP, acetylene black, Ketjen black, carbon nanofiber (VGCF), and carbon nanotubes; and the binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC-Na), polyvinyl pyrrolidone, polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), hydrogenated nitrile-butadiene rubber (HNBR), polyacrylic acid (PAA), lithium polyacrylate (PAA-Li), hydrogenated styrene-butadiene block copolymer (SEBS), and polyisobutylene (PIB).

[0088] In addition, in another specific embodiment, the negative electrode sheet can be lithium metal, lithium alloy, lithium-free negative electrode, etc., wherein the lithium-free negative electrode includes but is not limited to one of silver-carbon negative electrode, magnesium-carbon negative electrode, copper foil, and carbon-coated copper foil.

[0089] The present invention is described in detail below by way of specific examples. It should also be understood that the following examples are only used to specifically illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, and those skilled in the art can make selections within a suitable range through the description herein, and are not to be limited to the specific numerical values exemplified below.

[0090] Source of raw materials:

[0091] Polyurethane diol was purchased from Aladdin and dried.

[0092] Polyethylene glycol methyl ether methacrylate was purchased from Aladdin, Mn ~950.

[0093] Polyhexane was purchased from Aladdin, Mw ~ 45000.

[0094] Polyurethane with borate ester (PU-BO) is prepared based on the preparation and properties of self-healing polyurethane wood coatings with borate ester bonds.

[0095] A disulfide bond-containing polydimethylsiloxane flexible polymer (PDMS-SS-IP-BNB) was prepared based on a universally autonomous self-healing elastomer with high stretchability. Example 1

[0096] This embodiment provides an all-solid-state battery, the structure of which is as follows Figure 1As shown, a composite interface layer 4 is disposed at the interface between the negative electrode sheet 1 and the solid electrolyte membrane 3. The all-solid-state battery includes two outermost negative electrode sheets 1 and a positive electrode sheet 2 disposed between the two negative electrode sheets 1. A solid electrolyte membrane 3 is also disposed between the negative electrode sheet 1 and the positive electrode sheet 2. The negative electrode sheet 1 includes a negative electrode current collector 11 and a negative electrode active material layer 12 located on the side of the negative electrode current collector 11 near the solid electrolyte membrane 3. A composite interface layer 4 is disposed on the surface of the negative electrode sheet 1. The portion of the composite interface layer near the negative electrode active material layer 12 is a functional layer 41 comprising an elastic polymer matrix A (comprising an elastic polymer A and a lithium salt A) 411 and a ceramic fast lithium ion conductor 412. The portion of the composite interface layer near the solid electrolyte membrane 3 is a stress buffer layer 42 comprising an elastic polymer matrix B 421 (comprising an elastic polymer B, a plasticizer, and a lithium salt B). The positive electrode sheet 2 includes a positive electrode current collector 21 and a positive electrode active material layer 22 disposed on both sides of the positive electrode current collector 21.

[0097] This embodiment also provides a method for preparing the above-mentioned all-solid-state battery, comprising the following steps:

[0098] S0. Preparation of solid electrolyte membrane: The fast ion conductor Li6PS5Cl and the binder PTFE were mixed in a mass ratio of 98:2, and then high-energy ball milled (without a medium) at a speed of 600 r / min for 12 hours. Subsequently, a sulfide solid electrolyte membrane with a thickness of 50 μm was prepared by extrusion.

[0099] S1. Preparation of positive electrode sheet: fast ion conductor Li6PS5Cl, positive electrode active material NCM811 (i.e. LiNi 0.8 Co 0.1 Mn 0.1 O2), binder SEBS and conductive agent VGCF were mixed in a mass ratio of 9:85:3:3 and then subjected to high-energy ball milling (paraxylene medium) at a speed of 550 r / min for 12 hours to obtain a positive electrode material precursor slurry, which was then coated on the surface of aluminum foil to obtain a positive electrode sheet.

[0100] S2. Preparation of negative electrode sheet: The negative electrode active material micron silicon, binder PVDF and conductive agent SuperP were mixed in a mass ratio of 94:3:3 and then high-energy ball milled (NMP medium) at a speed of 450 r / min for 12 hours to obtain a negative electrode material precursor slurry, which was then coated on the surface of copper foil to obtain a negative electrode sheet.

[0101] S3. Preparation of the electrode side functional layer: LATP nanoparticles (D50 = 120 nm), polyurethane diol, and LiFSI were weighed in a mass ratio of 40:55:5, and added to NMP. The mixture was ball-milled and stirred for 3 hours to obtain a functional layer slurry with a mass solid content of 5%. The slurry was then coated on the surface of the pure silicon negative electrode by electrostatic spraying (voltage 25 kV, humidity 10%) and dried at 80°C for 40 minutes to obtain an electrode side functional layer with a thickness of 0.35 μm.

[0102] S4. Preparation of stress buffer layer: PU-BO, vinylene carbonate (Mw~88.6), and LiTFSI were weighed and dispersed in tetrahydrofuran in a mass ratio of 72:13:5, and 0.5wt% of the total mass of initiator diisopropyldicarbonamide was added except tetrahydrofuran to obtain a stress buffer layer slurry with a mass solid content of 10%. The slurry was scraped onto the surface of the electrode side functional layer to form a film, and heat-cured at 60°C for 30 minutes to obtain a stress buffer layer with a thickness of 2.2μm. The actual picture of the composite interface layer prepared in this embodiment is shown in Figure 2 .

[0103] S5. Stack the silicon negative electrode sheet and positive electrode sheet modified with the composite interface layer with the solid electrolyte membrane and pressurize them at 120°C to obtain an all-solid-state battery, which is then tested at 10 MPa.

[0104] Example 2

[0105] This embodiment provides an all-solid-state battery, the structure of which is the same as that of Example 1. The preparation method of the all-solid-state battery of this embodiment includes the following steps:

[0106] S0. Preparation of solid electrolyte membrane: The fast ion conductor Li6PS5Cl and the binder PTFE were mixed in a mass ratio of 98:2, and then high-energy ball milled (without a medium) at a speed of 600 r / min for 12 hours. Subsequently, a sulfide solid electrolyte membrane with a thickness of 50 μm was prepared by extrusion.

[0107] S1. Preparation of positive electrode sheet: The fast ion conductor Li6PS5Cl, the positive electrode active material NCM811, the binder SEBS and the conductive agent VGCF were mixed in a mass ratio of 9:85:3:3 and then high-energy ball milled (paraxylene medium) at a speed of 550 r / min for 12 hours to obtain a positive electrode material precursor slurry, which was then coated on the surface of aluminum foil to obtain a positive electrode sheet.

[0108] S2. Preparation of negative electrode sheet: The negative electrode active material micron silicon, binder PVDF and conductive agent SuperP were mixed in a mass ratio of 94:3:3 and then high-energy ball milled (NMP medium) at a speed of 450 r / min for 12 hours to obtain a negative electrode material precursor slurry, which was then coated on the surface of copper foil to obtain a negative electrode sheet.

[0109] S3. Preparation of the electrode side functional layer: LATP nanoparticles (D50 = 120 nm), polyurethane diol, and LiFSI were weighed in a mass ratio of 30:65:5, and added to NMP. The mixture was ball-milled and stirred for 3 hours to obtain a functional layer slurry with a mass solid content of 5%. The slurry was then coated on the surface of the pure silicon negative electrode by electrostatic spraying (voltage 25 kV, humidity 10%) and dried at 80°C for 40 minutes to obtain an electrode side functional layer with a thickness of 0.32 μm.

[0110] S4. Preparation of stress buffer layer: borate-containing polyurethane (PU-BO), vinylene carbonate (Mw ~ 88.6), LiTFSI and Ti3C2T were weighed in a mass ratio of 72:13:3:2. x Nanosheets were dispersed in tetrahydrofuran, and 0.5 wt% of the total weight of initiator diisopropyldicarbonamide was added to obtain a stress buffer layer slurry with a solid content of 10%. The slurry was then scraped onto the surface of the electrode side functional layer to form a film, and then thermally cured at 60°C for 30 minutes to obtain a stress buffer layer with a thickness of 2.5 μm. x The aspect ratio of the nanosheets is approximately equal to 45.

[0111] S5. Stack the silicon negative electrode sheet and positive electrode sheet modified with the composite interface layer with the solid electrolyte membrane, hot press them at 120°C to obtain an all-solid-state battery, and test it at 10 MPa.

[0112] Example 3

[0113] This embodiment provides an all-solid-state battery, the structure of which is the same as that of Example 1. The preparation method of the all-solid-state battery of this embodiment includes the following steps:

[0114] S0. Preparation of solid electrolyte membrane: The fast ion conductor Li6PS5Cl and the binder PTFE were mixed in a mass ratio of 98:2, and then high-energy ball milled (without a medium) at a speed of 600 r / min for 12 hours. Subsequently, a sulfide solid electrolyte membrane with a thickness of 50 μm was prepared by extrusion.

[0115] S1. Preparation of positive electrode sheet: The fast ion conductor Li6PS5Cl, the positive electrode active material NCM811, the binder SEBS and the conductive agent VGCF were mixed in a mass ratio of 9:85:3:3 and then high-energy ball milled (paraxylene medium) at a speed of 550 r / min for 12 hours to obtain a positive electrode material precursor slurry, which was then coated on the surface of aluminum foil to obtain a positive electrode sheet.

[0116] S2. Preparation of negative electrode sheet: The negative electrode active material micron silicon, binder PVDF and conductive agent SuperP were mixed in a mass ratio of 94:3:3 and then high-energy ball milled (NMP medium) at a speed of 450 r / min for 12 hours to obtain a negative electrode material precursor slurry, which was then coated on the surface of copper foil to obtain a negative electrode sheet.

[0117] S3. Preparation of the electrode side functional layer: LATP nanoparticles (D50 = 120 nm), polyurethane diol (Aladdin, dried), and LiTFSI were weighed in a mass ratio of 40:55:5, and added to NMP. The mixture was ball-milled and stirred for 3 hours to obtain a functional layer slurry with a mass solid content of 5%. The slurry was then coated on the surface of the pure silicon negative electrode by electrostatic spraying (voltage 25 kV, humidity 10%) and dried at 80°C for 40 minutes to obtain an electrode side functional layer with a thickness of 0.35 μm.

[0118] S4. Preparation of a stress buffer layer: PU-BO, polyethylene glycol methyl ether methacrylate, LiTFSI, and boron nitride nanosheets were dispersed in tetrahydrofuran in a mass ratio of 72:13:3:2. Diisopropyldicarbonamide (DICA) was added as an initiator at a total mass ratio of 0.5 wt% to the total mass of the tetrahydrofuran to prepare a stress buffer layer slurry with a solid content of 10%. This slurry was then applied by doctor blade to the surface of the electrode-side functional layer and thermally cured at 60°C for 30 min to obtain a stress buffer layer with a thickness of 2.3 μm. The boron nitride nanosheets had an aspect ratio of approximately 40.

[0119] S5. Stack the silicon negative electrode sheet and positive electrode sheet modified with the composite interface layer with the solid electrolyte membrane, hot press them at 120°C to obtain an all-solid-state battery, and test it at 10 MPa.

[0120] Example 4

[0121] This embodiment provides an all-solid-state battery, the structure of which is the same as that of Example 1. The preparation method of the all-solid-state battery of this embodiment includes the following steps:

[0122] S0. Preparation of solid electrolyte membrane: The fast ion conductor Li6PS5Cl and the binder PTFE were mixed in a mass ratio of 98:2, and then high-energy ball milled (without a medium) at a speed of 600 r / min for 12 hours. Subsequently, a sulfide solid electrolyte membrane with a thickness of 50 μm was prepared by extrusion.

[0123] S1. Preparation of positive electrode sheet: The fast ion conductor Li6PS5Cl, the positive electrode active material NCM811, the binder SEBS and the conductive agent VGCF were mixed in a mass ratio of 9:85:3:3 and then high-energy ball milled (paraxylene medium) at a speed of 550 r / min for 12 hours to obtain a positive electrode material precursor slurry, which was then coated on the surface of aluminum foil to obtain a positive electrode sheet.

[0124] S2. Preparation of negative electrode sheet: The negative electrode active material micron silicon, binder PVDF and conductive agent SuperP were mixed in a mass ratio of 94:3:3 and then high-energy ball milled (NMP medium) at a speed of 450 r / min for 12 hours to obtain a negative electrode material precursor slurry, which was then coated on the surface of copper foil to obtain a negative electrode sheet.

[0125] S3. Preparation of electrode side functional layer: Li6PS5Cl nanoparticles (D50 = 350 nm), polyurethane diol, and LiFSI were weighed in a mass ratio of 30:65:5, and added to anisole. The mixture was ball-milled and stirred for 3 hours to obtain a functional layer slurry with a mass solid content of 5%. The slurry was then coated on the surface of the pure silicon negative electrode by electrostatic spraying (voltage 25 kV, humidity 10%) and dried at 80°C for 40 minutes to obtain an electrode side functional layer with a thickness of 0.35 μm.

[0126] S4. Preparation of a stress buffer layer: PU-BO, polyethylene glycol methyl ether methacrylate, LiTFSI, and boron nitride nanosheets were dispersed in tetrahydrofuran in a mass ratio of 72:13:3:2. Azobisisobutyronitrile (ABI) was added as an initiator at a total mass ratio of 0.2 wt% (excluding the total mass of the tetrahydrofuran) to prepare a stress buffer layer slurry with a solid content of 10%. This slurry was then applied by doctor blade to the surface of the electrode-side functional layer and thermally cured at 60°C for 30 minutes to obtain a stress buffer layer with a thickness of 2.5 μm. The boron nitride nanosheets had an aspect ratio of approximately 40.

[0127] S5. Stack the silicon negative electrode sheet and positive electrode sheet modified with the composite interface layer with the solid electrolyte membrane and hot press them at 120°C to obtain an all-solid-state battery, which is then tested at 5 MPa.

[0128] Example 5

[0129] This embodiment provides an all-solid-state battery, the structure of which is the same as that of Example 1. The preparation method of the all-solid-state battery of this embodiment includes the following steps:

[0130] S0. Preparation of solid electrolyte membrane: The fast ion conductor Li6PS5Cl and the binder PTFE were mixed in a mass ratio of 98:2, and then high-energy ball milled (without a medium) at a speed of 600 r / min for 12 hours. Subsequently, a sulfide solid electrolyte membrane with a thickness of 50 μm was prepared by extrusion.

[0131] S1. Preparation of positive electrode sheet: The fast ion conductor Li6PS5Cl, the positive electrode active material NCM811, the binder SEBS and the conductive agent VGCF were mixed in a mass ratio of 9:85:3:3 and then high-energy ball milled (paraxylene medium) at a speed of 550 r / min for 12 hours to obtain a positive electrode material precursor slurry, which was then coated on the surface of aluminum foil to obtain a positive electrode sheet.

[0132] S2. Preparation of negative electrode sheet: The negative electrode active material micron silicon, binder PVDF and conductive agent SuperP were mixed in a mass ratio of 94:3:3 and then high-energy ball milled (NMP medium) at a speed of 450 r / min for 12 hours to obtain a negative electrode material precursor slurry, which was then coated on the surface of copper foil to obtain a negative electrode sheet.

[0133] S3. Preparation of electrode side functional layer: Li6PS5Cl nanoparticles (D50 = 350 nm), polyurethane diol (Aladdin, dried), and LiFSI were weighed in a mass ratio of 30:65:5, and dissolved in anisole. The mixture was ball-milled and stirred for 3 hours to obtain a functional layer slurry with a mass solid content of 5%. The slurry was then coated on the surface of a pure silicon negative electrode by electrostatic spraying (voltage 25 kV, humidity 10%) and dried at 80°C for 40 minutes to obtain an electrode side functional layer with a thickness of 0.36 μm.

[0134] S4. Preparation of a stress buffer layer: PU-BO, polyethylene glycol methyl ether methacrylate, LiTFSI, and boron nitride nanosheets were dispersed in tetrahydrofuran in a mass ratio of 72:13:3:2. Azobisisobutyronitrile (ABI) was added as an initiator at a total mass ratio of 0.2 wt% (excluding the total mass of the tetrahydrofuran) to prepare a stress buffer layer slurry with a solid content of 10%. This slurry was then applied by doctor blade to the surface of the electrode-side functional layer and thermally cured at 60°C for 30 min to obtain a stress buffer layer with a thickness of 2.4 μm. The boron nitride nanosheets had an aspect ratio of approximately 40.

[0135] S5. Use a knife to make two perpendicular scratches in the center of the composite interface layer parallel to the length and width directions. The scratch depth is 2 μm and the length is 3 cm.

[0136] S6. Stack the silicon negative electrode sheet and positive electrode sheet modified with the scratched composite interface layer with the solid electrolyte membrane, hot press them at 120°C to obtain an all-solid-state battery, and test it at 10 MPa.

[0137] Example 6

[0138] This embodiment provides an all-solid-state battery, the structure of which is the same as that of Example 1. The preparation method of the all-solid-state battery of this embodiment includes the following steps:

[0139] S0. Preparation of solid electrolyte membrane: The fast ion conductor Li6PS5Cl and the binder PTFE were mixed in a mass ratio of 98:2, and then high-energy ball milled (without a medium) at a speed of 600 r / min for 12 hours. Subsequently, a sulfide solid electrolyte membrane with a thickness of 50 μm was prepared by extrusion.

[0140] S1. Preparation of positive electrode sheet: The fast ion conductor Li6PS5Cl, the positive electrode active material NCM811, the binder SEBS and the conductive agent VGCF were mixed in a mass ratio of 9:85:3:3 and then high-energy ball milled (paraxylene medium) at a speed of 550 r / min for 12 hours to obtain a positive electrode material precursor slurry, which was then coated on the surface of aluminum foil to obtain a positive electrode sheet.

[0141] S2. Preparation of negative electrode sheet: The negative electrode active material micron silicon, binder PVDF and conductive agent SuperP were mixed in a mass ratio of 94:3:3 and then high-energy ball milled (NMP medium) at a speed of 450 r / min for 12 hours to obtain a negative electrode material precursor slurry, which was then coated on the surface of copper foil to obtain a negative electrode sheet.

[0142] S3. Preparation of the electrode side functional layer: LATP nanoparticles (D50 = 120 nm), polycaprolactone, and LiDFOB were weighed in a mass ratio of 20:65:15 and dissolved in NMP. The mixture was ball-milled and stirred for 1.5 h to obtain a functional layer slurry with a mass solid content of 5%. The slurry was then coated on the surface of the pure silicon negative electrode by electrostatic spraying (voltage 20 kV, humidity 10%) and dried at 80°C for 20 min to obtain an electrode side functional layer with a thickness of 0.42 μm.

[0143] S4. Preparation of stress buffer layer: Weigh disulfide bond-containing polydimethylsiloxane-based flexible polymer (PDMS-SS-IP-BNB), polyethylene glycol dimethyl ether (Mw ~ 750), LiBOB and Ti3C2T in a mass ratio of 75:14:10:1. x Nanosheets were dispersed in tetrahydrofuran, and 0.2 wt% of the total weight of initiator azobisisobutyronitrile was added to obtain a stress buffer layer slurry with a solid content of 10%. The slurry was then scraped onto the surface of the electrode side functional layer to form a film, and then thermally cured at 65°C for 30 minutes to obtain a stress buffer layer with a thickness of 3.6 μm. x The aspect ratio of the nanosheets is approximately equal to 45.

[0144] S5. Stack the silicon negative electrode sheet and positive electrode sheet modified with the composite interface layer with the solid electrolyte membrane, hot press them at 120°C to obtain an all-solid-state battery, and test it at 10 MPa.

[0145] Example 7

[0146] This embodiment provides an all-solid-state battery, the structure of which is the same as that of Example 1. The preparation method of the all-solid-state battery of this embodiment includes the following steps:

[0147] S0. Preparation of solid electrolyte membrane: The fast ion conductor Li6PS5Cl and the binder PTFE were mixed in a mass ratio of 98:2, and then high-energy ball milled (without a medium) at a speed of 600 r / min for 12 hours. Subsequently, a sulfide solid electrolyte membrane with a thickness of 50 μm was prepared by extrusion.

[0148] S1. Preparation of positive electrode sheet: The fast ion conductor Li6PS5Cl, the positive electrode active material NCM811, the binder SEBS and the conductive agent VGCF were mixed in a mass ratio of 9:85:3:3 and then high-energy ball milled (paraxylene medium) at a speed of 550 r / min for 12 hours to obtain a positive electrode material precursor slurry, which was then coated on the surface of aluminum foil to obtain a positive electrode sheet.

[0149] S2. Preparation of negative electrode sheet: The negative electrode active material micron silicon, binder PVDF and conductive agent SuperP were mixed in a mass ratio of 94:3:3 and then high-energy ball milled (NMP medium) at a speed of 450 r / min for 12 hours to obtain a negative electrode material precursor slurry, which was then coated on the surface of copper foil to obtain a negative electrode sheet.

[0150] S3. Preparation of electrode side functional layer: Li6PS5Cl nanoparticles (D50 = 350 nm), polycaprolactone, and LiDFOB were weighed in a mass ratio of 10:70:20, and added to NMP. The mixture was ball-milled and stirred for 3 h to obtain a functional layer slurry with a mass solid content of 5%. The slurry was then coated on the surface of a pure silicon negative electrode by electrostatic spraying (voltage 15 kV, humidity 10%) and dried at 100 ° C for 20 min to obtain an electrode side functional layer with a thickness of 0.45 μm.

[0151] S4. Preparation of a stress buffer layer: PDMS-SS-IP-BNB, polyethylene glycol dimethyl ether (Mw ~750), LiFSI, and graphene oxide were weighed and dispersed in acetonitrile in a mass ratio of 85:8:6:1. Azobisisobutyronitrile (ABI) was added to a total weight ratio of 0.2 wt% of the initiator (excluding the acetonitrile) to obtain a stress buffer layer slurry with a mass solids content of 10%. This slurry was then applied by knife coating onto the surface of the electrode-side functional layer and thermally cured at 70°C for 40 min to obtain a stress buffer layer with a thickness of 3.5 μm. The graphene oxide had an aspect ratio of approximately 30.

[0152] S5. Stack the silicon negative electrode sheet and positive electrode sheet modified with the composite interface layer with the solid electrolyte membrane, hot press them at 120°C to obtain an all-solid-state battery, and test it at 10 MPa.

[0153] Comparative Example 1

[0154] This comparative example provides an all-solid-state battery. The preparation method of the all-solid-state battery in this comparative example includes the following steps:

[0155] S0. Preparation of solid electrolyte membrane: The fast ion conductor Li6PS5Cl and the binder PTFE were mixed in a mass ratio of 98:2, and then high-energy ball milled (without a medium) at a speed of 600 r / min for 12 hours. Subsequently, a sulfide solid electrolyte membrane with a thickness of 50 μm was prepared by extrusion.

[0156] S1. Preparation of positive electrode sheet: The fast ion conductor Li6PS5Cl, the positive electrode active material NCM811, the binder SEBS and the conductive agent VGCF were mixed in a mass ratio of 9:85:3:3 and then high-energy ball milled (paraxylene medium) at a speed of 550 r / min for 12 hours to obtain a positive electrode material precursor slurry, which was then coated on the surface of aluminum foil to obtain a positive electrode sheet.

[0157] S2. Preparation of negative electrode sheet: The negative electrode active material micron silicon, binder PVDF and conductive agent SuperP were mixed in a mass ratio of 94:3:3 and then high-energy ball milled (NMP medium) at a speed of 450 r / min for 12 hours to obtain a negative electrode material precursor slurry, which was then coated on the surface of copper foil to obtain a negative electrode sheet.

[0158] S3. Stack the silicon negative electrode sheet, positive electrode sheet and solid electrolyte membrane and hot press them at 120°C to obtain an all-solid-state battery, which is then tested at 10 MPa.

[0159] Comparative Example 2

[0160] This comparative example provides an all-solid-state battery. The preparation method of the all-solid-state battery in this comparative example includes the following steps:

[0161] S0. Preparation of solid electrolyte membrane: The fast ion conductor Li6PS5Cl and the binder PTFE were mixed in a mass ratio of 98:2, and then high-energy ball milled (without a medium) at a speed of 600 r / min for 12 hours. Subsequently, a sulfide solid electrolyte membrane with a thickness of 50 μm was prepared by extrusion.

[0162] S1. Preparation of positive electrode sheet: The fast ion conductor Li6PS5Cl, the positive electrode active material NCM811, the binder SEBS and the conductive agent VGCF were mixed in a mass ratio of 9:85:3:3 and then high-energy ball milled (paraxylene medium) at a speed of 550 r / min for 12 hours to obtain a positive electrode material precursor slurry, which was then coated on the surface of aluminum foil to obtain a positive electrode sheet.

[0163] S2. Preparation of negative electrode sheet: The negative electrode active material micron silicon, binder PVDF and conductive agent SuperP were mixed in a mass ratio of 94:3:3 and then high-energy ball milled (NMP medium) at a speed of 450 r / min for 12 hours to obtain a negative electrode material precursor slurry, which was then coated on the surface of copper foil to obtain a negative electrode sheet.

[0164] S3. Preparation of negative electrode interface layer: Li6PS5Cl nanoparticles, polyethylene glycol methacrylate monomer, LiFSI, and azobisisobutyronitrile were weighed in a mass ratio of 30:64:5:1, and added to anisole. The mixture was ball-milled and stirred for 3 hours to obtain a slurry with a mass solid content of 5%. The slurry was then coated on the surface of a pure silicon negative electrode by electrostatic spraying (voltage 25 kV, humidity 10%) and cured at 80°C for 40 minutes to obtain a negative electrode interface layer with a thickness of 0.55 μm.

[0165] S4. After stacking the interface layer modified silicon negative electrode sheet, the positive electrode sheet and the solid electrolyte membrane, hot pressing them at 120°C to obtain an all-solid-state battery, and testing them at 10 MPa.

[0166] Comparative Example 3

[0167] This comparative example provides an all-solid-state battery having the same structure as that of Example 1. The preparation method of the all-solid-state battery of this comparative example comprises the following steps:

[0168] S0. Preparation of solid electrolyte membrane: The fast ion conductor Li6PS5Cl and the binder PTFE were mixed in a mass ratio of 98:2, and then high-energy ball milled (without a medium) at a speed of 600 r / min for 12 hours. Subsequently, a sulfide solid electrolyte membrane with a thickness of 50 μm was prepared by extrusion.

[0169] S1. Preparation of positive electrode sheet: The fast ion conductor Li6PS5Cl, the positive electrode active material NCM811, the binder SEBS and the conductive agent VGCF were mixed in a mass ratio of 9:85:3:3 and then high-energy ball milled (paraxylene medium) at a speed of 550 r / min for 12 hours to obtain a positive electrode material precursor slurry, which was then coated on the surface of aluminum foil to obtain a positive electrode sheet.

[0170] S2. Preparation of negative electrode sheet: The negative electrode active material micron silicon, binder PVDF and conductive agent SuperP were mixed in a mass ratio of 94:3:3 and then high-energy ball milled (NMP medium) at a speed of 450 r / min for 12 hours to obtain a negative electrode material precursor slurry, which was then coated on the surface of copper foil to obtain a negative electrode sheet.

[0171] S3. Preparation of the electrode side functional layer: LATP nanoparticles (D50 = 500 nm), polycaprolactone, and LiTFSI were weighed in a mass ratio of 5:90:5, and added to NMP. The mixture was ball-milled and stirred for 3 h to obtain a functional layer slurry with a mass solid content of 5%. The slurry was then coated on the surface of the pure silicon negative electrode by electrostatic spraying (voltage 15 kV, humidity 10%) and dried at 100 ° C for 20 min to obtain an electrode side functional layer with a thickness of 0.41 μm.

[0172] S4. Preparation of stress buffer layer: PU-BO, polyethylene glycol dimethyl ether (Mw ~ 750), LiTFSI and Ti3C2T were weighed in a mass ratio of 95.5:0.5:3:1. x Nanosheets were dispersed in acetonitrile, and 0.1 wt% of the total weight of initiator azobisisobutyronitrile was added to obtain a stress buffer layer slurry with a solid content of 10%. The slurry was then scraped onto the surface of the electrode side functional layer to form a film, and then thermally cured at 70°C for 20 minutes to obtain a stress buffer layer with a thickness of 3.5 μm. x The aspect ratio of the nanosheets is approximately equal to 45.

[0173] S5. Stack the silicon negative electrode sheet and positive electrode sheet modified with the composite interface layer with the solid electrolyte membrane, hot press them at 120°C to obtain an all-solid-state battery, and test it at 10 MPa.

[0174] Comparative Example 4

[0175] This comparative example is basically the same as Example 1, except that the polythiourethane in S4 is replaced by polyethylene oxide:

[0176] S0. Preparation of solid electrolyte membrane: The fast ion conductor Li6PS5Cl and the binder PTFE were mixed in a mass ratio of 98:2, and then high-energy ball milled (without a medium) at a speed of 600 r / min for 12 hours. Subsequently, a sulfide solid electrolyte membrane with a thickness of 50 μm was prepared by extrusion.

[0177] S1. Preparation of positive electrode sheet: The fast ion conductor Li6PS5Cl, the positive electrode active material NCM811 (i.e., LiNi0.8Co0.1Mn0.1O2), the binder SEBS, and the conductive agent VGCF were mixed in a mass ratio of 9:85:3:3 and subjected to high-energy ball milling (paraxylene medium) at a speed of 550 r / min for 12 h to obtain a positive electrode material precursor slurry, which was then coated on the surface of aluminum foil to obtain a positive electrode sheet.

[0178] S2. Preparation of negative electrode sheet: The negative electrode active material micron silicon, binder PVDF and conductive agent SuperP were mixed in a mass ratio of 94:3:3 and then high-energy ball milled (NMP medium) at a speed of 450 r / min for 12 hours to obtain a negative electrode material precursor slurry, which was then coated on the surface of copper foil to obtain a negative electrode sheet.

[0179] S3. Preparation of the electrode side functional layer: LATP nanoparticles (D50 = 120 nm), polyurethane, and LiFSI were weighed in a mass ratio of 40:55:5, and added to NMP. The mixture was ball-milled and stirred for 3 h to obtain a functional layer slurry with a mass solid content of 5%. The slurry was then coated on the surface of the pure silicon negative electrode by electrostatic spraying (voltage 25 kV, humidity 10%) and cured at 80°C for 40 min to obtain an electrode side functional layer with a thickness of 0.35 μm.

[0180] S4. Preparation of stress buffer layer: polyethylene oxide (Mw ~ 600000), vinylene carbonate (Mw ~ 88.6), and LiTFSI were weighed in a mass ratio of 72:13:5 and dispersed in tetrahydrofuran, and 0.5 wt% of the initiator diisopropyldicarbonamide was added to the total mass excluding tetrahydrofuran. The film was scraped onto the surface of the functional layer on the electrode side and thermally cured at 60°C for 30 minutes to obtain a stress buffer layer with a thickness of 2.2 μm.

[0181] S5. Stack the silicon negative electrode sheet and positive electrode sheet modified with the composite interface layer with the solid electrolyte membrane and pressurize them at 120°C to obtain an all-solid-state battery, which is then tested at 10 MPa.

[0182] Battery parameter test method:

[0183] 1) Poisson's ratio test method: The functional layer slurry is placed in a mold and heated and dried to form a film layer sample. A universal material testing machine is used to apply a tensile load to the sample. During the loading process, the axial elongation and lateral width change of the sample are measured respectively. The axial strain (ΔL / L) and lateral strain (ΔB / B) are calculated. The Poisson's ratio ν is the ratio of lateral strain to axial strain, ν = -(ΔB / B) ÷ (ΔL / L). ΔL is the axial deformation of the sample, L is the original axial length of the sample, ΔB is the lateral deformation of the sample, and B is the original lateral length of the sample.

[0184] 2) Young's modulus test method: Pour the stress buffer layer slurry into the mold, heat and dry it to form a film layer specimen. The specimen is firmly mounted in the fixture of the material testing machine, ensuring that the loading direction is consistent with the axis of the specimen, and a tensile load is applied to the specimen at a certain rate, while recording the load value and the axial elongation of the specimen. A displacement sensor is used to measure the deformation of the specimen during the stretching process. Finally, based on the load-deformation data, the stress σ = F / S (F is the load, S is the area of the section perpendicular to the axis) and the strain ε = ΔL / L are calculated, and the formula E = σ / ε is applied to obtain the Young's modulus.

[0185] The test results are shown in Table 1.

[0186] Table 1

[0187]

[0188] Performance Testing

[0189] The following performance tests were performed on the all-solid-state batteries prepared in the examples and comparative examples: initial interface impedance, first efficiency and first cycle interface impedance at 0.1C; capacity retention rate, interface impedance at 10 cycles, capacity retention rate and interface impedance at 100 cycles at 0.5C. The charge and discharge test equipment was a NEWAREBTS type charge and discharge tester produced by Shenzhen Newwell Electronics Co., Ltd. The charge and discharge voltage was 2.5-4.2V. Unless otherwise specified, the test pressure was 10 MPa. The electrochemical AC impedance spectroscopy test equipment was an Auto-Lab, where the test frequency was 0.01Hz-10 6 Hz, and then calculate the first efficiency according to the formula first efficiency = first cycle discharge capacity / first cycle charge capacity * 100%, calculate the 10-cycle capacity retention rate according to the formula 10th cycle capacity retention rate = 10th cycle discharge capacity / 1st cycle discharge capacity * 100%, and calculate the 100-cycle capacity retention rate according to the formula 100th cycle capacity retention rate = 100th cycle discharge capacity / 1st cycle discharge capacity * 100%. The results are shown in Table 2.

[0190] Table 2 Performance test results

[0191]

[0192] As can be seen from Table 1, compared with the comparative example, the first-cycle interface impedance, 10-cycle interface impedance and 100-cycle interface impedance of the all-solid-state battery of the embodiment of the present application are significantly reduced, and the 10-cycle capacity retention rate and 100-cycle capacity retention rate are significantly increased. The results show that in the present invention, by introducing a double-layer composite interface layer between the electrode and the solid electrolyte membrane, on the one hand, the interface impedance of the all-solid-state battery under a lower restraint pressure (10 MPa) is effectively improved through the flexible polymer matrix. On the other hand, the double-layer design of the functional layer and the buffer layer simultaneously achieves the relief of the increase in interface impedance and the reduction in battery performance caused by volume changes, microcracks, lithium dendrite precipitation and other phenomena during the cycle. Combined with the elastic polymer containing dynamically reversible chemical bonds, the composite interface film has a self-repairing function, thereby improving the cycle life of the battery.

[0193] The above embodiments are only preferred embodiments for fully illustrating the present application, and the protection scope of the present application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art based on the present application are within the protection scope of the present application.

Claims

1. A composite interface layer, characterized in that: including a functional layer and a stress buffer layer; The functional layer comprises, by mass percentage, 10%-50% of a ceramic fast lithium ion conductor, 20%-70% of an elastic polymer A, and 0.1%-30% of a lithium salt A. The Poisson's ratio of the functional layer is 0.01-0.3, and the Young's modulus of the functional layer is 0.1-2 GPa. The stress buffer layer comprises, by mass percentage, 65%-90% of an elastic polymer B, 1%-15% of a plasticizer, and 0.1%-20% of a lithium salt B. The Poisson's ratio of the stress buffer layer is 0.2-0.5, and the Young's modulus of the stress buffer layer is 0.01-0.5 GPa. The elastic polymer B contains dynamically reversible chemical bonds.

2. The composite interface layer according to claim 1, characterized in that The thickness of the functional layer is 0.1-0.5 μm, and / or The thickness of the stress buffer layer is 0.4-4.5 μm.

3. The composite interface layer according to claim 1, characterized in that The ceramic fast lithium ion conductor includes Li 1.3 Al 0.3 Ti 1.7 (PO4)3、Li7La3Zr2O 12 、Li 6.75 La3Zr 1.75 Nb 0.25 O 12 、Li 6-y PS5Cl 1+y 、Li 10 SnP2S 12 At least one of , where 0≤y≤1; and / or The particle size D50 of the ceramic fast lithium ion conductor is 50-500 nm.

4. The composite interface layer according to any one of claims 1 to 3, characterized in that: The elastic polymer A includes at least one of polycaprolactone, polyurethane, polythiourethane, polyethylene glycol-polycarbonate copolymer, and polydimethylsiloxane.

5. The composite interface layer according to any one of claims 1 to 3, characterized in that: The elastic polymer B includes at least one of a polycarbonate polymer, a polythiourethane polymer, and a polydimethylsiloxane polymer; and / or The dynamically reversible chemical bond includes at least one of a disulfide bond, a borate bond, and a Diels-Alder bond.

6. The composite interface layer according to any one of claims 1 to 3, characterized in that: The raw material of the plasticizer includes at least one of vinylene carbonate, fluoroethylene carbonate, succinonitrile, polyethylene glycol diacrylate, polyethylene glycol dimethyl ether, polyethylene glycol methacrylate, polyethylene glycol dimethacrylate, 1,3-dioxolane, and tetrahydrofuran; and / or The molecular weight of the raw material of the plasticizer is ≤1000 g / mol.

7. The composite interface layer according to any one of claims 1 to 3, characterized in that: The lithium salt A includes at least one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), and lithium difluorooxalatoborate; and / or The lithium salt B includes at least one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalatoborate), and lithium difluorooxalatoborate.

8. The composite interface layer according to any one of claims 1 to 3, characterized in that: Based on the mass of the stress buffer layer, the stress buffer layer further comprises 0.1%-5% of a nano-enhancer.

9. The composite interface layer according to claim 8, characterized in that: The nano-enhancer includes at least one of MXene, boron nitride nanosheets, molybdenum disulfide nanosheets, titanium dioxide nanosheets, and graphene oxide; and / or The aspect ratio of the nano-reinforcement agent is ≥30.

10. A method for preparing the composite interface layer according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1, mixing a ceramic fast lithium ion conductor, an elastic polymer A, a lithium salt A, and a first organic solvent to obtain a functional layer slurry, and using the functional layer slurry to prepare a functional layer on at least one side of a negative electrode sheet; S2. Mixing the elastic polymer B, the plasticizer raw material, the initiator, the lithium salt B, and the second organic solvent to obtain a stress buffer layer slurry, coating the stress buffer layer slurry on the functional layer, and heating and curing the mixture to obtain the composite interface layer.

11. The method for preparing a composite interface layer according to claim 10, characterized in that: At least one of the following conditions is met: (1) In S2, the curing temperature is 50-150° C. and the curing time is 10-60 min; (2) In S1, the ceramic fast lithium ion conductor, the elastic polymer A, the lithium salt A, and the first organic solvent are mixed for 1 to 5 hours; (3) The initiator includes at least one of diisopropyldicarbonamide, lithium hexafluorophosphate, lithium tetrafluoroborate, phenyllithium, azobisisobutyronitrile, and Lewis acidic binary metal halide salts; (4) The amount of the initiator added is 0.1% to 1% of the sum of the mass of the elastic polymer B, the plasticizer raw material, the initiator, and the lithium salt B; (5) The first organic solvent and the second organic solvent independently include at least one of ethylene carbonate, propylene carbonate, N-methylpyrrolidone, tetrahydrofuran, ethylene glycol dimethyl ether, acetonitrile, anisole, and p-xylene.

12. An all-solid-state battery comprising a positive electrode sheet, a negative electrode sheet and a solid electrolyte membrane, characterized in that: The composite interface layer according to any one of claims 1 to 9 or the composite interface layer prepared according to the preparation method according to claim 10 or 11 is provided at the interface between at least one negative electrode sheet and the electrolyte membrane.

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