Composite solid electrolyte separator and preparation method therefor

Abstract

Disclosed in present invention are a composite solid electrolyte separator and a preparation method therefor. The composite solid electrolyte separator comprises a substrate layer, a composite electrolyte layer and a first interface polymer electrolyte layer, which are stacked in sequence, wherein the composite electrolyte layer comprises a ceramic oxide, a lithium salt and at least one selected from a first polymer and a binder; and the content of the ceramic oxide is 80 wt% or higher relative to the total weight of the composite electrolyte layer. The composite solid electrolyte separator of the present invention can reduce interface impedance and induce uniform deposition of lithium ions, and the composite solid electrolyte separator also has a high elastic modulus, can prevent penetration of lithium dendrites, and can meet the usage requirements of a solid lithium metal battery.

Description

A composite solid electrolyte membrane and preparation method thereof Technical Field

[0001] The present invention relates to a composite solid electrolyte membrane and a preparation method thereof, as well as a solid-state lithium metal battery comprising the composite solid electrolyte membrane. Background Art

[0002] Lithium-ion batteries, with their long cycle life and high energy density, have become a vital energy storage device in our daily lives. The rapid growth of electric vehicles in recent years has placed higher demands on battery energy density and safety. Solid-state lithium metal batteries, which use lithium metal as the negative electrode and a solid electrolyte instead of traditional separators and electrolytes, not only significantly increase the battery's energy density but also significantly reduce the risk of spontaneous combustion and explosion.

[0003] Currently, the large-scale application of all-solid-state lithium metal batteries still faces many major challenges, including poor interface stability between the solid electrolyte and the electrode material, short cycle life, and insufficient ionic conductivity, which hinder the commercial application of solid-state lithium metal batteries. During the technological development process, the transition from semi-solid-state batteries to quasi-solid-state batteries and finally to all-solid-state batteries is achieved by reducing the electrolyte.

[0004] Separators in semi-solid-state and quasi-solid-state lithium metal batteries require good electrolyte wettability or solid electrolyte interfacial compatibility, good stability at the lithium metal interface, and the ability to inhibit lithium dendrite growth. Currently commercially available polyolefin separators and solid electrolyte films cannot simultaneously meet these requirements.

[0005] Therefore, designing a separator for lithium metal semi-solid batteries that can inhibit the growth of lithium dendrites while forming a stable interface contact has become a very critical technology.

[0006] Summary of the Invention

[0007] The technical problem to be solved by the present invention is that the separator in the current semi-solid battery cannot simultaneously meet the problems of electrolyte infiltration, inhibition of lithium dendrite growth, and high conductivity. It provides a composite solid electrolyte separator and its preparation method that can reduce interfacial impedance, induce uniform deposition of lithium ions, and at the same time have a high elastic modulus, prevent lithium dendrite penetration, and can meet the needs of solid-state lithium metal batteries.

[0008] A first aspect of the present invention provides a composite solid electrolyte membrane, which includes a base layer, a composite electrolyte layer and a first interface polymer electrolyte layer stacked in sequence; wherein the composite electrolyte layer contains a ceramic oxide, a lithium salt, and at least one selected from a first polymer and an adhesive; relative to the total weight of the composite electrolyte layer, the content of the ceramic oxide is greater than 80 weight%.

[0009] In some specific embodiments, the lithium salt is selected from one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalatoborate), lithium bis(fluorosulfonyl)imide, and lithium difluorooxalatoborate.

[0010] In some specific embodiments, the ceramic oxide is a lithium-containing ceramic oxide, preferably one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum titanium oxide, and lithium germanium aluminum phosphate. More preferably, the lithium-containing ceramic oxide also contains one or more doping elements selected from aluminum, gallium, and tantalum.

[0011] In some specific embodiments, the adhesive is selected from one or more of polytetrafluoroethylene, polyvinyl pyrrolidone, polyvinyl butyral, styrene-butadiene rubber latex, carboxymethyl cellulose, polyacrylic acid, and polyacrylonitrile.

[0012] In some specific embodiments, the first polymer is selected from one or more of polyethylene oxide, polyvinylidene fluoride, and polyethylene glycol.

[0013] In some specific embodiments, relative to the total weight of the composite electrolyte layer, the content of the ceramic oxide is 80-98.5 wt %, the content of the first polymer is 0-15 wt %, the content of the lithium salt is 0.3-17 wt %, and the content of the binder is 0-5 wt %.

[0014] In some specific embodiments, the base layer is a polyethylene film, a polypropylene film, or a polyethylene-polypropylene composite film.

[0015] In some specific embodiments, the thickness of the composite electrolyte layer is 0.5-20 μm, preferably 5-15 μm.

[0016] In some specific embodiments, a second interfacial polymer electrolyte layer is further provided between the substrate layer and the composite electrolyte layer.

[0017] In some specific embodiments, the first interfacial polymer electrolyte layer and the second interfacial polymer electrolyte layer each independently contain one or more selected from polyethylene oxide, polyvinylidene fluoride, and polyethylene glycol.

[0018] In some embodiments, the thickness of the first interfacial polymer electrolyte layer is 1-5 μm. In some embodiments, the thickness of the second interfacial polymer electrolyte layer is 1-5 μm.

[0019] A second aspect of the present invention provides a method for preparing a composite solid electrolyte membrane, the method comprising the following steps:

[0020] (1) coating a composite electrolyte slurry on the substrate to form a composite electrolyte layer;

[0021] (2) forming a first interfacial polymer electrolyte layer on the composite electrolyte layer formed in step (1);

[0022] The composite electrolyte slurry contains ceramic oxide, lithium salt, solvent, and at least one selected from a first polymer and a binder; the amount of the ceramic oxide is greater than 80 weight% relative to the dry weight of the composite electrolyte slurry (i.e., the total weight of the composite electrolyte slurry minus the weight of the solvent).

[0023] In some specific embodiments, the preparation method further comprises: before forming the composite electrolyte layer on the substrate layer, forming a second interfacial polymer electrolyte layer on the substrate layer, and then coating the second interfacial polymer electrolyte layer with a composite electrolyte slurry to form a composite electrolyte layer.

[0024] In some specific embodiments, the first interfacial polymer electrolyte layer and the second interfacial polymer electrolyte layer each independently contain one or more selected from polyethylene oxide, polyvinylidene fluoride, and polyethylene glycol.

[0025] In some specific embodiments, the lithium salt is selected from one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalatoborate), lithium bis(fluorosulfonyl)imide, and lithium difluorooxalatoborate.

[0026] In some specific embodiments, the ceramic oxide is a lithium-containing ceramic oxide, preferably one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum titanium oxide, and lithium germanium aluminum phosphate. More preferably, the lithium-containing ceramic oxide also contains one or more doping elements selected from aluminum, gallium, and tantalum.

[0027] In some specific embodiments, the adhesive is selected from one or more of polytetrafluoroethylene, polyvinyl pyrrolidone, polyvinyl butyral, styrene-butadiene rubber latex, carboxymethyl cellulose, polyacrylic acid, and polyacrylonitrile.

[0028] In some specific embodiments, the first polymer is selected from one or more of polyethylene oxide, polyvinylidene fluoride, and polyethylene glycol.

[0029] In some specific embodiments, relative to the dry weight of the composite electrolyte slurry, the amount of the ceramic oxide is 80-98.5 wt %, the amount of the first polymer is 0-15 wt %, the amount of the lithium salt is 0.3-17 wt %, and the amount of the binder is 0-5 wt %.

[0030] In some specific embodiments, the base layer is a polyethylene film, a polypropylene film, or a polyethylene-polypropylene composite film.

[0031] In some specific embodiments, the conditions for forming the composite electrolyte layer include: a temperature of 60-90° C. and a time of 6-24 hours.

[0032] The third aspect of the present invention provides the use of the composite solid electrolyte membrane of the first aspect of the present invention or the composite solid electrolyte membrane obtained by the preparation method of the second aspect of the present invention in a solid-state lithium metal battery.

[0033] The fourth aspect of the present invention provides a solid-state lithium metal battery, which includes the composite solid-state electrolyte membrane of the first aspect of the present invention or the composite solid-state electrolyte membrane obtained by the preparation method of the second aspect of the present invention.

[0034] Specifically, the solid-state lithium metal battery is a semi-solid-state battery or a quasi-solid-state battery.

[0035] In the composite solid electrolyte membrane of the present invention, a ceramic oxide-polymer composite solid electrolyte with a high ceramic content (more than 80%) is attached to a diaphragm such as PE with good flexibility, thereby solving the problem that the ceramic oxide-polymer composite electrolyte layer becomes hard and brittle after the ceramic content exceeds 60%; furthermore, by adding a deformable polymer solid electrolyte layer with high ionic conductivity to the surface of the composite electrolyte layer, close contact between the electrolyte and the lithium metal is achieved, the interface impedance is reduced, and the hard and brittle ceramic oxide-polymer composite electrolyte layer forms a close interface contact with the lithium metal interface.

[0036] Through the composite structure of a ceramic oxide-polymer composite electrolyte layer with a high solid content, the composite solid electrolyte membrane of the present invention can not only solve the problems of electrolytic wettability and interface contact between the membrane and the positive electrode material; it also enables the composite solid electrolyte membrane to have higher ionic conductivity and mechanical strength, and can effectively inhibit the growth and puncture of lithium dendrites while reducing impedance; and it can form a close interface contact with the lithium metal negative electrode without the need for liquid electrolyte, further reducing the amount of liquid electrolyte used while effectively reducing the interface impedance.

[0037] The composite solid electrolyte separator of the present invention realizes good flexibility, stable and tight electrolyte-electrode interface, ultra-thinness, high ion conductivity and the effect of inhibiting lithium dendrite growth under the synergistic effect of the composite membrane layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG1 is a schematic structural diagram of a first embodiment of a composite solid electrolyte membrane according to the present invention.

[0039] FIG2 is a schematic structural diagram of a second embodiment of the composite solid electrolyte membrane of the present invention.

[0040] FIG3 shows the charge and discharge capacity-voltage curves of batteries made from separators of comparative examples and examples of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, the terms used herein have the same meaning as those of ordinary skill in the art would normally understand. The numerical limits or ranges stated herein include endpoints, specifically all values ​​and subranges within the numerical limits or ranges. In the present invention, "optional" means that the corresponding components may or may not be present.

[0042] A first aspect of the present invention provides a composite solid electrolyte membrane, as shown in Figure 1, comprising a base layer 1, a composite electrolyte layer 2, and a first interface polymer electrolyte layer 3 stacked in sequence; wherein the composite electrolyte layer 2 contains a ceramic oxide, a lithium salt, and at least one selected from a first polymer and an adhesive; relative to the total weight of the composite electrolyte layer 2, the content of the ceramic oxide is 80 weight % or more.

[0043] In the present invention, the ceramic oxide is a lithium-containing ceramic oxide, including but not limited to one or more of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), lithium lanthanum titanate oxide (LLTO), and lithium aluminum germanium phosphate (LAGP). Furthermore, as needed, the ceramic oxide may also contain doping elements such as aluminum, gallium, tantalum, etc. In some preferred embodiments of the present invention, the ceramic oxide may be aluminum-doped lithium lanthanum zirconium oxide (LALZO), such as Li (7-3x) Al (x) La3Zr2O 12 , where x can be 0.01-0.8.

[0044] In the present invention, the lithium salt can use any existing lithium salt that can be used for solid-state battery separators, for example, it can be selected from one or more of lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(trifluoromethylsulfonyl)imide (LiN(CF3SO2)2), lithium bis(oxalatoborate) (LiBOB), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium difluorooxalatoborate (LiDFOB).

[0045] In the present invention, the first polymer may be selected from one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), and polyethylene glycol (PEG).

[0046] In the present invention, the adhesive can be selected from one or more of polytetrafluoroethylene (PTFE), polyvinyl pyrrolidone (PVP), polyvinyl butyral (PVB), styrene-butadiene rubber (SBR) emulsion, carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and polyacrylonitrile (PAN).

[0047] In the present invention, to further improve the performance of the composite electrolyte layer, the composite electrolyte layer may further contain a modifier as needed. For example, the first polymer (such as PEO) may be modified by adding copper fluoride to improve its ionic conductivity. The amount of copper fluoride added is, for example, 0.1% to 1% by weight, preferably 0.25% to 0.5% by weight, relative to the first polymer.

[0048] According to some preferred embodiments of the present invention, relative to the total weight of the composite electrolyte layer, the content of the ceramic oxide may be 80-98.5 wt%, preferably 85-96 wt%; the content of the first polymer may be 0-15 wt%, preferably 1-15 wt%, more preferably 1.12-15 wt%, further preferably 3.1-11.5 wt%; the content of the lithium salt may be 0.3-17 wt%, preferably 1-10 wt%; the content of the adhesive may be 0-10 wt%.

[0049] In addition, relative to the total weight of the composite electrolyte layer, the content of the ceramic oxide can be, for example, 80 weight %, 85 weight %, 90 weight %, 95 weight % or 98 weight %, etc.; the content of the first polymer can be, for example, 0 weight %, 5 weight %, 10 weight % or 15 weight %, etc.; the content of the binder can be, for example, 0 weight %, 1 weight %, 3 weight %, 8 weight % or 10 weight %, etc.;

[0050] According to the present invention, the composite electrolyte layer may contain a first polymer or a binder, or may contain both the first polymer and the binder. Preferably, the combined content of the first polymer and the binder (when both are present) is 5-20 wt %, preferably 6-15 wt %, relative to the total weight of the composite electrolyte layer.

[0051] Furthermore, as needed, the composite electrolyte layer may further contain a plasticizer. The plasticizer may be, for example, one or more of succinonitrile (SN), polyethylene glycol, and dioctyl phthalate, with succinonitrile being preferred. The amount of the plasticizer may be, for example, 1-8 wt %, preferably 3-5 wt %, relative to the total weight of the composite electrolyte layer.

[0052] In the present invention, the thickness of the composite electrolyte layer can be 0.5-20 μm, preferably 5-15 μm. In addition, the ionic conductivity of the composite electrolyte layer is greater than 10 -5 S / cm.

[0053] In the present invention, there is no particular limitation on the substrate layer; any existing separator that can be used for solid-state battery separators can be used, preferably a polyolefin microporous membrane, such as a polyethylene film, a polypropylene film, or a polyethylene-polypropylene composite film. In some preferred embodiments, the substrate layer includes, but is not limited to, a polyethylene (PE) monolayer film, a polypropylene (PP) monolayer film, and a PP / PE / PP three-layer composite film.

[0054] According to some preferred embodiments of the present invention, a second interfacial polymer electrolyte layer 4 is further provided between the substrate layer and the composite electrolyte layer. As shown in FIG2 , the composite solid electrolyte membrane of the present invention comprises a substrate layer 1, a second interfacial polymer electrolyte layer 4, a composite electrolyte layer 2, and a first interfacial polymer electrolyte layer 3 stacked in sequence.

[0055] That is, the composite solid electrolyte membrane of the present invention can be a three-layer structure (base layer / composite electrolyte layer / first interface polymer electrolyte layer) or a four-layer structure (base layer / second interface polymer electrolyte layer / composite electrolyte layer / first interface polymer electrolyte layer).

[0056] In the present invention, the composition and thickness of the first and second interfacial polymer electrolyte layers can be the same or different. The thickness of the first and second interfacial polymer electrolyte layers can be 1-5 μm, preferably 2-3 μm, respectively.

[0057] The polymers in the first interfacial polymer electrolyte layer and the second interfacial polymer electrolyte layer include, but are not limited to, one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), and polyethylene glycol (PEG). Preferably, the polymers are selected from (i) PEO; (ii) a mixture of PEO and PEG (e.g., a PEO:PEG weight ratio of 1:0.5-1); and (iii) a mixture of PEO, PEG, and PVDF (e.g., a PEO:PEG:PVDF weight ratio of 1:0.1-0.5:0.3-0.8).

[0058] In addition, the first interfacial polymer electrolyte layer and the second interfacial polymer electrolyte layer may each independently further include a lithium salt and an optional binder, etc. The specific compounds that can be used as the lithium salt and the binder are the same as those in the composite electrolyte layer.

[0059] In the first interfacial polymer electrolyte layer and the second interfacial polymer electrolyte layer, preferably, the lithium salt content can be 7-44% by weight, preferably 15-38.7% by weight, relative to the total weight of the first interfacial polymer electrolyte layer or the second interfacial polymer electrolyte layer, respectively. The polymer content can be 56-93% by weight, preferably 61.3-85% by weight, and the binder content can be 0-5% by weight, preferably 0-3% by weight.

[0060] In addition, the content of lithium salt can be, for example, 7 weight %, 10 weight %, 20 weight %, 30 weight %, 40 weight % or 44 weight % relative to the total weight of the first interface polymer electrolyte layer or the second interface polymer electrolyte layer; the content of polymer can be, for example, 56 weight %, 60 weight %, 70 weight %, 80 weight %, 90 weight % or 93 weight % or the like.

[0061] In addition, the polymer, lithium salt and binder in the first and second interfacial polymer electrolyte layers may be the same as or different from the first polymer in the composite electrolyte layer.

[0062] A second aspect of the present invention provides a method for preparing a composite solid electrolyte membrane, comprising the following steps:

[0063] (1) coating a composite electrolyte slurry on the substrate to form a composite electrolyte layer;

[0064] (2) forming a first interfacial polymer electrolyte layer on the composite electrolyte layer formed in step (1);

[0065] The composite electrolyte slurry contains ceramic oxide, lithium salt, solvent, and at least one selected from a first polymer and a binder; the amount of the ceramic oxide is greater than 80 weight% relative to the dry weight of the composite electrolyte slurry (i.e., the total weight of the composite electrolyte slurry minus the weight of the solvent).

[0066] In the present invention, the ceramic oxide is a lithium-containing ceramic oxide, including but not limited to one or more of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum zirconium tantalum oxide (LLZTO), lithium lanthanum titanate oxide (LLTO), and lithium aluminum germanium phosphate (LAGP).

[0067] In the present invention, the lithium salt can be selected from one or more of lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(trifluoromethylsulfonyl)imide (LiN(CF3SO2)2), lithium bis(oxalatoborate) (LiBOB), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium difluorooxalatoborate (LiDFOB).

[0068] In the present invention, the first polymer may be selected from one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), and polyethylene glycol (PEG).

[0069] In the present invention, the adhesive can be selected from one or more of polytetrafluoroethylene (PTFE), polyvinyl pyrrolidone (PVP), polyvinyl butyral (PVB), styrene-butadiene rubber (SBR) emulsion and carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and polyacrylonitrile (PAN).

[0070] According to some preferred embodiments of the present invention, relative to the dry weight of the composite electrolyte slurry, the content of the ceramic oxide may be 80-98.5 wt%, preferably 85-96 wt%; the content of the first polymer may be 0-15 wt%, preferably 1-15 wt%, more preferably 1.12-15 wt%, further preferably 3.1-11.5 wt%; the content of the lithium salt may be 0.3-17 wt%, preferably 1-10 wt%; the content of the adhesive may be 0-10 wt%.

[0071] According to the present invention, the composite electrolyte layer may contain a first polymer or a binder, or may contain both the first polymer and the binder. Preferably, the total content of the first polymer or the binder (when both are present) is 5-20 wt %, preferably 6-15 wt %, relative to the total weight of the composite electrolyte layer.

[0072] In the present invention, the solvent can be any solvent capable of forming the desired composite electrolyte slurry from the above components and used to form the composite electrolyte layer. Examples include acetonitrile, N,N-dimethylformamide, tetrahydrofuran, isopropyl alcohol, and the like. The amount of solvent used can be, for example, 5-50 parts by weight, preferably 10-30 parts by weight, relative to 1 part by weight of the first polymer. To obtain a uniform composite electrolyte slurry, the ceramic oxide, lithium salt, solvent, and at least one selected from the first polymer and the binder are preferably thoroughly mixed by grinding, for example, by ball milling at a rotational speed of 200-800 rpm for 1-5 hours.

[0073] There is no particular limitation on the method for forming the composite electrolyte layer, as long as a composite electrolyte slurry layer of the desired thickness is formed on the substrate layer and the composite electrolyte layer is obtained after drying and / or pressurizing. Specifically, the composite electrolyte slurry can be evenly applied to the substrate layer with a scraper. Drying conditions may include, for example, a temperature of 60-90°C and a time of 6-24h; preferably, a temperature of 70-80°C and a time of 12-24h. Pressurization conditions may include, for example, a pressure of 10-100MPa and a time of 1-60min; preferably, a pressure of 20-100MPa and a time of 10-30min.

[0074] In the present invention, the thickness of the composite electrolyte layer can be 0.5-20 μm, preferably 5-15 μm. In addition, the ionic conductivity of the composite electrolyte layer is greater than 10 -5 S / cm.

[0075] In the present invention, the substrate layer is not particularly limited and any existing separator that can be used for solid-state battery separators can be used, preferably a polyolefin microporous membrane, such as a polyethylene film, a polypropylene film, or a polyethylene-polypropylene composite film. Specifically, the substrate layer includes but is not limited to a polyethylene (PE) monolayer film, a polypropylene (PP) monolayer film, and a PP / PE / PP three-layer composite film.

[0076] According to some preferred embodiments of the present invention, in order to further improve the interfacial contact effect between the electrolyte and the negative electrode, the preparation method may further include: before forming the composite electrolyte layer on the substrate layer, first forming a second interfacial polymer electrolyte layer on the substrate layer, and then coating the second interfacial polymer electrolyte layer with a composite electrolyte slurry to form a composite electrolyte layer. That is, the preparation method of the present invention may include the following steps:

[0077] (i) forming a second interfacial polymer electrolyte layer on the substrate;

[0078] (ii) coating a composite electrolyte slurry on the second interfacial polymer electrolyte layer formed in step (i) to form a composite electrolyte layer;

[0079] (iii) forming a first interfacial polymer electrolyte layer on the composite electrolyte layer formed in step (ii).

[0080] The polymers in the first interfacial polymer electrolyte layer and the second interfacial polymer electrolyte layer include, but are not limited to, one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), and polyethylene glycol (PEG).

[0081] In addition, the first interfacial polymer electrolyte layer and the second interfacial polymer electrolyte layer may each independently further comprise a lithium salt and an optional binder, wherein the specific range of compounds that can be used as the lithium salt and the binder is the same as that of the composite electrolyte layer.

[0082] The first interfacial polymer electrolyte layer and the optional second interfacial polymer electrolyte layer may have the same or different compositions and thicknesses, and the thicknesses of the first interfacial polymer electrolyte layer and the second interfacial polymer electrolyte layer may be 0.1-5 μm, preferably 2-3 μm, respectively.

[0083] In addition, the preparation method of the first interfacial polymer electrolyte layer and the optional second interfacial polymer electrolyte layer can be carried out in a similar manner to the composite electrolyte layer, that is, using the corresponding polymer electrolyte solution to form the desired thickness and drying it. Specifically, the polymer electrolyte solution can be evenly applied to the substrate layer using a scraper. Drying can include atmospheric pressure drying and vacuum drying. Specific conditions may include, for example, a temperature of 60-90°C for 6-24 hours; preferably, a temperature of 70-80°C for 12-24 hours.

[0084] The third aspect of the present invention provides the use of the composite solid electrolyte membrane of the first aspect of the present invention or the composite solid electrolyte membrane obtained by the preparation method of the second aspect of the present invention in a solid-state lithium metal battery.

[0085] The fourth aspect of the present invention provides a solid-state lithium metal battery, which includes the composite solid-state electrolyte membrane of the first aspect of the present invention or the composite solid-state electrolyte membrane obtained by the preparation method of the second aspect of the present invention.

[0086] Preferably, the solid-state lithium metal battery is a semi-solid-state battery or a quasi-solid-state battery, wherein a semi-solid-state battery or a quasi-solid-state battery refers to a solid-state battery in which the liquid weight of the battery accounts for 1-10%.

[0087] The present invention is described in detail below by way of examples, which are not intended to limit the present invention. The experimental methods in the following examples are conventional methods unless otherwise specified. The aluminum-doped lithium lanthanum zirconium oxide (Li 6.28 Al 0.24La3Zr2O 12 , hereinafter referred to as LALZO) was purchased from Dongguan Kelude Innovation Technology Co., Ltd., and PEO polymer powder (Mw ~ 600000) was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0088] Example

[0089] Example 1

[0090] This embodiment provides a three-layer composite solid electrolyte membrane, as shown in FIG1 , which includes a base layer 1 , a composite electrolyte layer 2 and a first interface polymer electrolyte layer 3 stacked in sequence, wherein the base layer 1 is a PE membrane.

[0091] The composite electrolyte layer is made of aluminum-doped lithium lanthanum zirconium oxide (Li 6.28 Al 0.24 La3Zr2O 12 ), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and PEO polymer (Mw~600000), wherein the weight parts of the above components are: 80 parts of aluminum-doped lithium lanthanum zirconium oxide, 6.7 parts of LiTFSI, and 13.3 parts of PEO polymer.

[0092] First, a composite solid electrolyte slurry was prepared according to the following preparation steps.

[0093] S1: Preparation of polymer solution

[0094] PEO and LiTFSI were weighed and mixed with acetonitrile according to the above ratio, with the weight ratio of acetonitrile being PEO:acetonitrile = 1:20. The mixture was stirred magnetically at 80° C. until the powder was completely dissolved.

[0095] S2: Preparation of composite solid electrolyte slurry

[0096] LALZO and polymer solution were weighed according to the above ratio and evenly dispersed by ball milling at a speed of 500 rpm / min for 2 hours to obtain a uniformly dispersed composite solid electrolyte slurry.

[0097] Then, a three-layer composite solid electrolyte membrane was prepared according to the following preparation steps.

[0098] S10: Preparation of interfacial polymer layer solution

[0099] 0.56 parts by weight of PEO powder, 0.14 parts by weight of polyethylene glycol (PEG), 0.3 parts by weight of polyvinylidene fluoride, 0.316 parts by weight of LiTFSI and 20 parts by weight of acetonitrile were weighed and mixed, and stirred magnetically at 80° C. until all the powders were dissolved.

[0100] S20: Preparation of composite electrolyte layer

[0101] The composite solid electrolyte slurry prepared above was evenly coated onto a PE separator using a doctor blade and baked at 80°C for 24 hours. The film was then pressed at 25 MPa using a hydraulic press for 30 minutes, forming a dense composite electrolyte layer approximately 20 μm thick.

[0102] S30: Preparation of the first interfacial polymer electrolyte layer

[0103] The prepared interfacial polymer layer solution was evenly applied to the surface of the separator on which the composite electrolyte layer was formed using a scraper and baked at 80°C for 24 hours. The membrane was then dried in a vacuum drying oven for 24 hours to form a first interfacial polymer electrolyte layer with a thickness of approximately 2 μm, thereby obtaining a three-layer composite solid electrolyte separator.

[0104] Example 2

[0105] This embodiment provides a three-layer composite solid electrolyte membrane, which includes a base layer, a composite electrolyte layer and a first interface polymer electrolyte layer stacked in sequence, wherein the base layer is a PE membrane.

[0106] The composite electrolyte layer is made of aluminum-doped lithium lanthanum zirconium oxide (Li 6.28 Al 0.24 La3Zr2O 12 ), PEO polymer (Mw ~ 600000), succinonitrile (SN) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and the weight proportions of the above components are: 80 parts of aluminum-doped lithium lanthanum zirconium oxide, 9.1 parts of PEO polymer, 4.3 parts of succinonitrile and 6.6 parts of lithium bis(trifluoromethanesulfonyl)imide.

[0107] First, a composite solid electrolyte slurry was prepared according to the following preparation steps.

[0108] S1: Preparation of polymer solution

[0109] PEO, succinonitrile and LiTFSI were weighed and mixed with acetonitrile according to the above proportions. The amount of acetonitrile used was a weight ratio of PEO:acetonitrile = 0.67:20. The mixture was stirred magnetically at 80° C. until all the powders were dissolved.

[0110] S2: Preparation of composite solid electrolyte slurry

[0111] Aluminum-doped lithium lanthanum zirconium oxide (LALZO) and the polymer solution were weighed according to the above ratio and evenly dispersed by ball milling at a speed of 500 rpm for 2 hours to obtain a uniformly dispersed composite solid electrolyte slurry.

[0112] Then, a three-layer composite solid electrolyte membrane was prepared according to the following preparation steps.

[0113] S10: Preparation of interfacial polymer layer solution

[0114] 0.56 parts by weight of PEO powder, 0.14 parts by weight of polyethylene glycol (PEG), 0.3 parts by weight of polyvinylidene fluoride, 0.316 parts by weight of lithium bis(trifluoromethanesulfonyl)imide) and 20 parts by weight of acetonitrile were mixed and stirred magnetically at 80° C. until all the powders were dissolved.

[0115] S20: Composite electrolyte layer preparation

[0116] The composite solid electrolyte slurry prepared above was evenly coated onto a PE separator using a doctor blade and baked at 80°C for 24 hours. The film was then pressed at 25 MPa using a hydraulic press for 30 minutes, forming a dense composite electrolyte layer approximately 20 μm thick.

[0117] S30: Preparation of the first interfacial polymer electrolyte layer

[0118] The prepared interfacial polymer layer solution was evenly applied to the surface of the separator on which the composite electrolyte layer was formed using a scraper and baked at 80°C for 24 hours. The membrane was then dried in a vacuum drying oven for 24 hours to form a first interfacial polymer electrolyte layer with a thickness of approximately 2 μm, thereby obtaining a three-layer composite solid electrolyte separator.

[0119] Example 3

[0120] This embodiment provides a three-layer composite solid electrolyte membrane, including a base layer, a composite electrolyte layer and a first interface polymer electrolyte layer stacked in sequence, wherein the base layer is a PE membrane.

[0121] The composite electrolyte layer is made of aluminum-doped lithium lanthanum zirconium oxide (Li 6.28 Al 0.24 La3Zr2O 12 ), PEO polymer, polyvinylidene fluoride (PVDF) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and the weight proportions of the above components are: 80 parts of aluminum-doped lithium lanthanum zirconium oxide, 9.3 parts of PEO polymer, 4 parts of polyvinylidene fluoride, and 6.7 parts of lithium bis(trifluoromethanesulfonyl)imide.

[0122] First, a composite solid electrolyte slurry was prepared according to the following preparation steps.

[0123] S1: Preparation of polymer solution

[0124] PEO, polyvinylidene fluoride, LiTFSI and acetonitrile were weighed and mixed according to the above proportions, with the weight ratio of acetonitrile being PEO:acetonitrile = 0.7:20. The mixture was stirred magnetically at 80° C. until all the powders were dissolved.

[0125] S2: Preparation of composite solid electrolyte slurry

[0126] Aluminum-doped lithium lanthanum zirconium oxide (LALZO) and the polymer solution were weighed according to the above ratio and evenly dispersed by ball milling at a speed of 500 rpm for 2 hours to obtain a uniformly dispersed composite solid electrolyte slurry.

[0127] Then, a three-layer composite solid electrolyte membrane was prepared according to the following preparation steps.

[0128] S10: Preparation of interfacial polymer layer solution

[0129] 0.56 parts by weight of PEO powder, 0.14 parts by weight of polyethylene glycol (PEG), 0.3 parts by weight of polyvinylidene fluoride, 0.316 parts by weight of lithium bis(trifluoromethanesulfonyl)imide) and 20 parts by weight of acetonitrile were mixed and stirred magnetically at 80° C. until all the powders were dissolved.

[0130] S20: Preparation of composite electrolyte layer

[0131] The composite solid electrolyte slurry prepared above was evenly coated onto a PE separator using a doctor blade and baked at 80°C for 24 hours. The film was then pressed at 25 MPa using a hydraulic press for 30 minutes, forming a dense composite electrolyte layer approximately 20 μm thick.

[0132] S30: Preparation of the first interfacial polymer electrolyte layer

[0133] The prepared interfacial polymer layer solution was evenly applied to the surface of the separator on which the composite electrolyte layer was formed using a scraper and baked at 80°C for 24 hours. The membrane was then dried in a vacuum drying oven for 24 hours to form a first interfacial polymer electrolyte layer with a thickness of approximately 2 μm, thereby obtaining a three-layer composite solid electrolyte separator.

[0134] Example 4

[0135] This embodiment provides a three-layer composite solid electrolyte membrane, including a base layer, a composite electrolyte layer and a first interface polymer electrolyte layer stacked in sequence, wherein the base layer is a PE membrane.

[0136] The composite electrolyte layer is made of aluminum-doped lithium lanthanum zirconium oxide (Li 6.28 Al 0.24 La3Zr2O 12 ), polyvinyl butyral and lithium bis(trifluoromethanesulfonyl imide), the weight parts of the above components are respectively: 90 parts of aluminum-doped lithium lanthanum zirconium oxide, 7 parts of polyvinyl butyral, and 3 parts of lithium bis(trifluoromethanesulfonyl imide.

[0137] First, a composite solid electrolyte slurry was prepared according to the following preparation steps.

[0138] According to the above proportions, polyvinyl butyral, LiTFSI and isopropyl alcohol were weighed and mixed, with the weight ratio of polyvinyl butyral to acetonitrile being 14:260. The mixture was stirred magnetically until the polyvinyl butyral was completely dissolved.

[0139] Aluminum-doped lithium lanthanum zirconium oxide (LALZO) was added according to the above ratio and evenly dispersed by ball milling at a speed of 500 rpm for 2 hours to obtain a uniformly dispersed composite solid electrolyte slurry.

[0140] Then, a three-layer composite solid electrolyte membrane was prepared according to the following preparation steps.

[0141] S10: Preparation of interfacial polymer layer solution

[0142] The components were weighed and mixed according to a weight ratio of PEO:LiTFSI:acetonitrile = 1:0.316:20, and stirred magnetically at 80° C. until all the powders were dissolved.

[0143] S20: Composite electrolyte layer preparation

[0144] The composite solid electrolyte slurry prepared above was evenly coated onto a PE separator using a doctor blade and baked at 80°C for 24 hours. The film was then pressed at 25 MPa using a hydraulic press for 30 minutes, forming a dense composite electrolyte layer approximately 20 μm thick.

[0145] S30: Preparation of the first interfacial polymer electrolyte layer

[0146] The prepared interfacial polymer layer solution was evenly applied to the surface of the separator on which the composite electrolyte layer was formed using a scraper and baked at 80°C for 24 hours. The membrane was then dried in a vacuum drying oven for 24 hours to form a first interfacial polymer electrolyte layer with a thickness of approximately 2 μm, thereby obtaining a three-layer composite solid electrolyte separator.

[0147] Example 5

[0148] This embodiment provides a four-layer composite solid electrolyte membrane, as shown in FIG2 , comprising a base layer 1 , a second interface polymer electrolyte layer 4 , a composite electrolyte layer 2 and a first interface polymer electrolyte layer 3 , wherein the base layer 1 is a PE membrane.

[0149] The composite solid electrolyte layer is made of aluminum-doped lithium lanthanum zirconium oxide (Li 6.28 Al 0.24 La3Zr2O 12), PEO polymer, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), wherein the weight proportions of the above components are: 90 parts of aluminum-doped lithium lanthanum zirconium oxide, 7.5 parts of PEO polymer, and 2.5 parts of lithium bis(trifluoromethanesulfonyl)imide.

[0150] First, a composite solid electrolyte slurry was prepared according to the following preparation steps.

[0151] S1: Preparation of polymer solution

[0152] PEO, LiTFSI and acetonitrile were weighed and mixed according to the above ratio, with the weight ratio of acetonitrile being PEO:acetonitrile = 1:20. The mixture was stirred magnetically at 80° C. until all the powders were dissolved.

[0153] S2: Preparation of composite solid electrolyte slurry

[0154] Aluminum-doped lithium lanthanum zirconium oxide (LALZO) and the polymer solution were weighed according to the above ratio and evenly dispersed by ball milling at a speed of 500 rpm for 2 hours to obtain a uniformly dispersed composite solid electrolyte slurry.

[0155] Then, a four-layer composite solid electrolyte membrane was prepared according to the following preparation steps.

[0156] S10: Preparation of interfacial polymer layer solution

[0157] A solution was prepared according to the ratio of PEO: polyethylene glycol: LiTFSI: acetonitrile = 6:4:3.16:200, and stirred magnetically at 80°C until all the powders were dissolved.

[0158] S20: Preparation of the second interfacial polymer electrolyte layer 4

[0159] The polymer solution prepared above was evenly coated onto the surface of the separator using a scraper, baked at 80° C. for 24 hours, and then dried in a vacuum drying oven for 24 hours to form a second interface polymer electrolyte layer 4 with a thickness of about 2 μm.

[0160] S30: Composite electrolyte layer preparation

[0161] The composite solid electrolyte slurry prepared above was evenly applied using a doctor blade to the surface of the PE separator on which the second interfacial polymer electrolyte layer 4 was formed, and baked at 80°C for 24 hours. The film was then pressed using a hydraulic press at 25 MPa for 30 minutes, forming a dense composite electrolyte layer approximately 20 μm thick.

[0162] S40: Preparation of the first interfacial polymer electrolyte layer 3

[0163] The prepared interfacial polymer layer solution was evenly applied to the surface of the separator on which the composite electrolyte layer was formed using a scraper and baked at 80°C for 24 hours. The solution was then dried in a vacuum drying oven for 24 hours to form a first interfacial polymer electrolyte layer 3 with a thickness of approximately 2 μm, thereby obtaining a four-layer composite solid electrolyte separator.

[0164] Comparative Example 1

[0165] A composite solid electrolyte membrane was prepared according to the method of Example 1, except that it only contained a membrane layer and a composite electrolyte layer, but did not contain a first interface polymer electrolyte layer. The remaining steps and conditions were exactly the same as those of Example 1.

[0166] Comparative Example 2

[0167] A composite solid electrolyte membrane was prepared according to the method of Example 1, except that it only contained a membrane layer and a first interface polymer electrolyte layer, but did not contain a composite electrolyte layer. The remaining steps and conditions were exactly the same as those of Example 1.

[0168] Comparative Example 3

[0169] A composite solid electrolyte membrane was prepared according to the method of Example 1, except that the content of aluminum-doped lithium lanthanum zirconium oxide in the composite electrolyte layer was 70 wt %.

[0170] Comparative Example 4

[0171] A composite solid electrolyte membrane was prepared according to the method of Example 1, except that the composite electrolyte layer did not contain lithium salt.

[0172] Test Case

[0173] This test case is used to illustrate the application of composite solid electrolyte membranes in semi-solid / quasi-solid-state lithium metal batteries.

[0174] The first interfacial polymer layer of the composite solid electrolyte membrane prepared in the above examples and comparative examples was bonded to lithium metal and hot-pressed at 90°C and 1 MPa for 10 minutes. After cooling, it was assembled with a lithium iron phosphate positive electrode to form a battery. A small amount of electrolyte was injected into the positive electrode side and the battery was encapsulated in a button cell case. After formation, a semi-solid / quasi-solid-state lithium metal battery was obtained.

[0175] Test conditions: room temperature;

[0176] Test method: 0.33C constant current charge and discharge;

[0177] Test equipment: Xinwei battery test system, CT-4008Tn-mA

[0178] The capacity-voltage curve and capacity retention rate after 20 cycles of charge and discharge of the obtained semi-solid / quasi-solid lithium metal battery were measured, and the results are shown in Figure 3 and Table 1. Comparative Example 4 could not be charged and discharged normally, so the corresponding test data is not reflected in Figure 3.

[0179] Table 1

[0180] It can be seen from the results of Figure 3 and Table 1 that the composite solid electrolyte diaphragm of the present invention can provide good cycle stability performance. In contrast, when a diaphragm that does not include a composite electrolyte layer is used (Comparative Example 2), the lithium metal battery quickly fails, and when a diaphragm that does not contain a lithium salt in the composite electrolyte layer is used (Comparative Example 4), the lithium metal battery cannot perform normal charge and discharge cycles. In addition, when a diaphragm that does not include a first interfacial polymer electrolyte layer (Comparative Example 1) and a diaphragm in which the content of aluminum-doped lithium lanthanum zirconium oxygen in the composite electrolyte layer does not meet the requirements of the present invention (Comparative Example 3) are used, the capacity retention rate of the lithium metal battery is much worse than that of Example 1.

[0181] The above examples are used to describe exemplary embodiments of the present invention, but the present invention is not limited thereto. It should be understood by those skilled in the art that the above examples are for illustrative purposes only, and the specific embodiments and examples of the present invention should not be construed as limiting the scope of the present invention. The embodiments can be changed and modified within the scope of the present invention, and such changes and modifications should fall within the scope of protection of the present invention.

Claims

1. A composite solid electrolyte membrane, characterized in that: The composite solid electrolyte membrane comprises a substrate layer, a composite electrolyte layer and a first interface polymer electrolyte layer which are stacked in sequence; The composite electrolyte layer contains ceramic oxide, lithium salt, and at least one selected from a first polymer and an adhesive; the content of the ceramic oxide is greater than 80 weight % relative to the total weight of the composite electrolyte layer.

2. The composite solid electrolyte membrane according to claim 1, wherein: The lithium salt is selected from one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalatoborate), lithium bis(fluorosulfonyl)imide, and lithium difluorooxalatoborate.

3. The composite solid electrolyte membrane according to claim 1 or 2, wherein: The ceramic oxide is a lithium-containing ceramic oxide, preferably one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum titanium oxide, and lithium germanium aluminum phosphate. More preferably, the lithium-containing ceramic oxide also contains one or more doping elements selected from aluminum, gallium, and tantalum.

4. The composite solid electrolyte membrane according to any one of claims 1 to 3, wherein: The adhesive is selected from one or more of polytetrafluoroethylene, polyvinyl pyrrolidone, polyvinyl butyral, styrene-butadiene rubber latex, carboxymethyl cellulose, polyacrylic acid, and polyacrylonitrile.

5. The composite solid electrolyte membrane according to any one of claims 1 to 4, wherein: The first polymer is selected from one or more of polyethylene oxide, polyvinylidene fluoride, and polyethylene glycol.

6. The composite solid electrolyte membrane according to any one of claims 1 to 5, wherein: Relative to the total weight of the composite electrolyte layer, the content of the ceramic oxide is 80-98.5 wt %, the content of the first polymer is 0-15 wt %, the content of the lithium salt is 0.3-17 wt %, and the content of the adhesive is 0-5 wt %.

7. The composite solid electrolyte membrane according to any one of claims 1 to 6, wherein: The base layer is a polyethylene film, a polypropylene film or a polyethylene-polypropylene composite film; Preferably, the composite electrolyte layer has a thickness of 0.5-20 μm, preferably 5-15 μm.

8. The composite solid electrolyte membrane according to any one of claims 1 to 7, wherein: A second interfacial polymer electrolyte layer is also provided between the substrate layer and the composite electrolyte layer; Preferably, the first interfacial polymer electrolyte layer and the second interfacial polymer electrolyte layer each independently contain one or more selected from polyethylene oxide, polyvinylidene fluoride, polyethylene glycol; Preferably, the thickness of the first interfacial polymer electrolyte layer is 1-5 μm; Preferably, the thickness of the second interfacial polymer electrolyte layer is 1-5 μm.

9. A method for preparing a composite solid electrolyte membrane, characterized in that: The preparation method comprises the following steps: (1) coating a composite electrolyte slurry on the substrate to form a composite electrolyte layer; (2) forming a first interfacial polymer electrolyte layer on the composite electrolyte layer formed in step (1); The composite electrolyte slurry contains ceramic oxide, lithium salt, solvent, and at least one selected from a first polymer and an adhesive; the amount of the ceramic oxide is more than 80 weight % relative to the dry weight of the composite electrolyte slurry.

10. The preparation method according to claim 9, wherein: The preparation method further comprises: before forming the composite electrolyte layer on the substrate layer, forming a second interface polymer electrolyte layer on the substrate layer, and then coating the composite electrolyte slurry on the second interface polymer electrolyte layer to form the composite electrolyte layer; Preferably, the first interfacial polymer electrolyte layer and the second interfacial polymer electrolyte layer each independently contain one or more selected from polyethylene oxide, polyvinylidene fluoride, and polyethylene glycol.

11. The preparation method according to claim 9 or 10, wherein: The lithium salt is selected from one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalatoborate), lithium bis(fluorosulfonyl)imide, and lithium difluorooxalatoborate.

12. The preparation method according to any one of claims 9 to 11, wherein The ceramic oxide is a lithium-containing ceramic oxide, preferably one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum titanium oxide, and lithium germanium aluminum phosphate. More preferably, the lithium-containing ceramic oxide further contains one or more doping elements selected from aluminum, gallium, and tantalum. Preferably, the adhesive is one or more selected from polytetrafluoroethylene, polyvinyl pyrrolidone, polyvinyl butyral, styrene-butadiene rubber latex, carboxymethyl cellulose, polyacrylic acid, and polyacrylonitrile; Preferably, the first polymer is selected from one or more of polyethylene oxide, polyvinylidene fluoride and polyethylene glycol.

13. The preparation method according to any one of claims 9 to 12, wherein: Relative to the dry weight of the composite electrolyte slurry, the amount of the ceramic oxide is 80-98.5% by weight, the amount of the first polymer is 0-15% by weight, the amount of the lithium salt is 0.3-17% by weight, and the amount of the adhesive is 0-5% by weight.

14. The preparation method according to any one of claims 9 to 13, wherein The base layer is a polyethylene film, a polypropylene film or a polyethylene-polypropylene composite film; Preferably, the conditions for forming the composite electrolyte layer include: a temperature of 60-90° C. and a time of 6-24 h.

15. Use of the composite solid electrolyte membrane according to any one of claims 1 to 8 or the composite solid electrolyte membrane obtained by the preparation method according to any one of claims 9 to 14 in a solid-state lithium metal battery; Preferably, the solid-state lithium metal battery is a semi-solid-state battery or a quasi-solid-state battery.

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