Lithium metal battery and manufacturing method therefor, and battery pack

Abstract

A lithium metal battery and a battery pack. The lithium metal battery comprises a positive electrode, a lithium metal negative electrode, a composite solid electrolyte separator between the positive electrode and the lithium metal negative electrode, and a polymer electrolyte for infiltrating the composite solid electrolyte separator. The lithium metal battery has good electrochemical stability, high energy density, low interface impedance, and high safety.

Description

A lithium metal battery and its preparation method and battery pack Technical Field

[0001] The present invention relates to a lithium metal battery, a preparation method thereof and a battery pack. Background Art

[0002] With the rapid development of electric vehicles, lithium-ion batteries have become the primary type of power battery. However, lithium-ion batteries still face limitations in terms of energy density, safety, and cost. Therefore, research and development of new battery technologies has become a hot topic in the development of the electric vehicle industry.

[0003] Quasi-solid-state lithium metal batteries are a new battery technology that combines the advantages of traditional lithium-ion batteries and solid-state batteries. Compared with traditional lithium-ion batteries, quasi-solid-state lithium metal batteries have higher energy density and improved safety. Compared with all-solid-state batteries, quasi-solid-state lithium metal batteries are easier to manufacture and lower cost, and have broad application prospects in electric vehicles, drones, energy storage, and other fields. With the advancement of science and technology and the accumulation of engineering practice, quasi-solid-state lithium metal batteries are expected to become one of the next generation of high-energy-density, high-safety, and low-cost battery technologies.

[0004] Currently, quasi-solid-state lithium metal batteries face many challenges, among which the most important ones include the electrochemical stability of the electrolyte and electrode materials, interfacial impedance, and the formation of lithium dendrites. Therefore, it is crucial to design a quasi-solid-state lithium metal battery with good electrochemical stability, low interfacial impedance, and the ability to suppress dendrite growth.

[0005] Summary of the Invention

[0006] In response to the above technical problems, the first aspect of the present invention provides a lithium metal battery, which includes a positive electrode, a lithium metal negative electrode, a composite solid electrolyte membrane between the positive electrode and the lithium metal negative electrode, and a polymer electrolyte that impregnates the composite solid electrolyte membrane; wherein the composite solid electrolyte membrane includes a base layer, a composite electrolyte layer and a first interface polymer electrolyte layer stacked in sequence, and the composite electrolyte layer contains a ceramic oxide, a first 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 80 weight% or more.

[0007] In some embodiments, the polymer electrolyte comprises a second lithium salt, a second solvent, and a second polymer.

[0008] In some specific embodiments, the second 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.

[0009] In some specific embodiments, the second solvent is selected from one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, and ethylene glycol dimethyl ether.

[0010] In some specific embodiments, the second polymer is selected from one or more polymers of (meth)acrylic acid compounds, (meth)acrylate compounds, (meth)acrylonitrile compounds, unsaturated carbonates and alkylene oxide compounds, preferably selected from one or more polymers of acrylic acid, methacrylic acid, methyl methacrylate, butyl acrylate, trifluoroethyl acrylate, acrylonitrile, ethylene carbonate, vinylene carbonate, polyethylene glycol methyl ether methacrylate, ethylene oxide and 1,3-dioxolane.

[0011] In some embodiments, the polymer electrolyte is formed in situ by an in situ curing electrolyte.

[0012] In some embodiments, the content of the second lithium salt is 0.5-4 M. In some embodiments, the content of the second polymer is 1-50 wt % relative to the total weight of the polymer electrolyte.

[0013] In some specific embodiments, the first 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.

[0014] 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.

[0015] 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.

[0016] In some embodiments, the first polymer is selected from one or more of polyethylene oxide, polyvinylidene fluoride, and polyethylene glycol.

[0017] 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 first lithium salt is 0.3-17 wt %, and the content of the binder is 0-5 wt %.

[0018] In some specific embodiments, the base layer is a polyethylene film, a polypropylene film, or a polyethylene-polypropylene composite film.

[0019] In some specific embodiments, a second interfacial polymer electrolyte layer is further provided between the substrate layer and the composite electrolyte layer.

[0020] 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.

[0021] In some specific embodiments, the lithium metal battery is a quasi-solid-state battery or a semi-solid-state battery.

[0022] A second aspect of the present invention provides a method for preparing a lithium metal battery, the lithium metal battery comprising a positive electrode, a lithium metal negative electrode, a composite solid electrolyte membrane between the positive electrode and the lithium metal negative electrode, and a polymer electrolyte;

[0023] The preparation method comprises: hot pressing a composite solid electrolyte diaphragm and a lithium metal negative electrode, cooling the composite solid electrolyte diaphragm and the positive electrode to form a battery core, allowing an in-situ solidified electrolyte to infiltrate the composite solid electrolyte diaphragm from the positive electrode side, encapsulating and polymerizing the composite solid electrolyte diaphragm to form a polymer electrolyte;

[0024] The composite solid electrolyte membrane comprises a base layer, a composite electrolyte layer and a first interfacial polymer electrolyte layer stacked in sequence, wherein the composite electrolyte layer contains a ceramic oxide, a first 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%.

[0025] In some specific embodiments, the in-situ curing electrolyte comprises a second lithium salt, a second solvent, a monomer, a cross-linking agent, and an initiator.

[0026] In some specific embodiments, the second 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.

[0027] In some specific embodiments, the second solvent is selected from one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate and ethylene glycol dimethyl ether.

[0028] In some specific embodiments, the monomer is selected from one or more of (meth)acrylic acid compounds, (meth)acrylate compounds, (meth)acrylonitrile compounds, unsaturated carbonates and alkylene oxide compounds, preferably selected from one or more of acrylic acid, methacrylic acid, methyl methacrylate, butyl acrylate, trifluoroethyl acrylate, acrylonitrile, ethylene carbonate, vinylene carbonate, polyethylene glycol methyl ether methacrylate, ethylene oxide and 1,3-dioxolane.

[0029] In some specific embodiments, the cross-linking agent is selected from one or more of organic peroxides, amines, oximes, organic sulfides, phenolic resins, organic dibasic acids, polyols, compounds containing unsaturated double bonds in the molecule, and polythiol polymers.

[0030] In some specific embodiments, the initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl, dicumyl peroxide, dibenzoyl peroxide, or ammonium persulfide.

[0031] A third aspect of the present invention provides a battery pack, which includes the lithium metal battery of the present invention or the lithium metal battery obtained by the preparation method of the present invention.

[0032] In the lithium metal battery of the present invention, a ceramic oxide-polymer composite solid electrolyte with a high ceramic content (above 80%) is attached to a flexible substrate layer, and a deformable polymer solid electrolyte layer with high ionic conductivity is added to achieve close contact between the electrolyte and the lithium metal, reducing interfacial impedance. This results in a highly flexible, high-performance, and highly safe composite solid electrolyte separator. Simultaneously, the use of a polymer electrolyte significantly reduces the content of the flowable liquid electrolyte, improving battery safety. As a result, the lithium metal battery of the present invention exhibits good electrochemical stability, high energy density, low interfacial impedance, and high safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 shows a schematic structural diagram of a lithium metal battery according to the present invention.

[0034] FIG2 is a schematic structural diagram of a first embodiment of the composite solid electrolyte membrane of the present invention.

[0035] FIG3 shows a schematic structural diagram of a second embodiment of the composite solid electrolyte membrane of the present invention.

[0036] FIG4 shows the battery impedance change results of the lithium metal battery of the present invention before and after in-situ solidification.

[0037] FIG5 shows a lithium metal battery of the present invention using LiNi 0.8 Co 0.1 Mn 0.1 Capacity-voltage curves of different embodiments of O2 as the positive electrode.

[0038] FIG6 shows the capacity-voltage curve of the lithium metal battery of the present invention using lithium iron phosphate as the positive electrode. DETAILED DESCRIPTION

[0039] 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.

[0040] A first aspect of the present invention provides a lithium metal battery, as shown in Figure 1, the lithium metal battery includes a positive electrode 10, a lithium metal negative electrode 40, a composite solid electrolyte membrane 30 between the positive electrode and the lithium metal negative electrode, and a polymer electrolyte 20 that impregnates the composite solid electrolyte membrane; as shown in Figure 2 or Figure 3, the composite solid electrolyte membrane 30 includes a base layer 1, a composite electrolyte layer 2 and a first interface polymer electrolyte layer 3 stacked in sequence, the composite electrolyte layer 2 contains a ceramic oxide, a first 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.

[0041] According to the present invention, as shown in Figure 1, the lithium metal battery further comprises a shell 50 covering the above structure. For the composite solid electrolyte separator, its first interface polymer electrolyte layer 3 contacts the electrolyte 20, and the base layer 1 contacts the positive electrode.

[0042] According to the present invention, the solid-state lithium metal battery may be 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 accounts for 1-10% by weight of the battery.

[0043] By using the composite solid electrolyte diaphragm structure of the present invention, the problem of the ceramic oxide-polymer composite electrolyte layer being hard and brittle when the ceramic content exceeds 60% is solved; furthermore, by adding a deformable polymer solid electrolyte layer with high ionic conductivity on 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, thereby achieving good flexibility, a stable and tight electrolyte-electrode interface, ultra-thinness, high ionic conductivity and the effect of inhibiting the growth of lithium dendrites.

[0044] The lithium metal battery of the present invention has a battery structure with the above-mentioned composite solid electrolyte membrane and polymer electrolyte, which not only solves the problems of electrolyte 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 does not require liquid electrolyte to form a close interface contact with the lithium metal negative electrode, further reducing the amount of liquid electrolyte used while effectively reducing the interface impedance.

[0045] In the polymer electrolyte of the present invention, the polymer electrolyte may, for example, comprise a second lithium salt, a second solvent, and a second polymer. The second lithium salt includes, but is not limited to, 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); the second solvent includes, but is not limited to, ethylene carbonate (EC), diethyl carbonate (DEC), diethyl carbonate (DEC), and difluoromethanesulfonate (DFC). The present invention relates to a polymer comprising: a common electrolyte solvent such as dimethyl methacrylate (DMC), ethyl methyl carbonate (EMC), propylene carbonate (PC), and ethylene glycol dimethyl ether (DME); the second polymer includes but is not limited to one or more selected from (meth) acrylic acid compounds, (meth) acrylic ester compounds, (meth) acrylonitrile compounds, unsaturated carbonates, and alkylene oxide compounds, for example, a polymer formed from one or more of acrylic acid, methacrylic acid, methyl methacrylate, butyl acrylate, trifluoroethyl acrylate, acrylonitrile, ethylene carbonate, vinylene carbonate, polyethylene glycol methyl ether methacrylate, ethylene oxide, and 1,3-dioxolane.

[0046] In the above polymer electrolyte, preferably, the concentration of lithium salt (calculated as lithium ions) is 0.5-4M, preferably 1-2M; relative to the total weight of the polymer electrolyte, the content of the second polymer is 1-50% by weight, 2-10% by weight.

[0047] According to some preferred embodiments of the present invention, the electrolyte is an in-situ solidification electrolyte. More preferably, the in-situ solidification electrolyte comprises a second solvent, a second lithium salt, a monomer, a cross-linking agent, and an initiator.

[0048] The monomer may be one or more selected from (meth)acrylic acid compounds, (meth)acrylate compounds, (meth)acrylonitrile compounds, unsaturated carbonates and alkylene oxide compounds, for example, may be one or more selected from acrylic acid, methacrylic acid, methyl methacrylate, butyl acrylate, trifluoroethyl acrylate, acrylonitrile, ethylene carbonate, vinylene carbonate, polyethylene glycol methyl ether methacrylate, ethylene oxide and 1,3-dioxolane.

[0049] The cross-linking agents include organic peroxides, amines, oximes, organic sulfides, phenolic resins, organic dibasic acids, polyols, compounds containing multiple unsaturated double bonds in the molecule (such as pentaerythritol tetraacrylate, pentaerythritol, triacrylate, polyethylene glycol diacrylate, etc.) and polythiol polymers.

[0050] The initiator includes one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl, dicumyl peroxide, dibenzoyl peroxide or ammonium persulfide.

[0051] In the above-mentioned in-situ solidification electrolyte, preferably, the concentration of the lithium salt (calculated as lithium ions) is 0.5-4M, more preferably 1-2M; the content of the monomer is 1-50 weight %, more preferably 2-10 weight %; the content of the cross-linking agent is 0.5-25 weight %, more preferably 1-5 weight %; and / or the content of the initiator is 0.01-1 weight %, more preferably 0.1-0.5 weight %. Specifically, the concentration of the lithium salt (calculated as lithium ions) can be 0.5M, 1M, 1.5M, 2M, 2.5M, 3M, 3.5M or 4M, etc.; the content of the monomer can be 1 weight %, 5 weight %, 10 weight %, 15 weight %, 20 weight %, 25 weight %, 30 weight %, 35 weight %, 40 weight %, 45 weight % or 50 weight %, etc.; the content of the cross-linking agent can be 0.5 weight %, 1 weight %, 5 weight %, 10 weight %, 15 weight %, 20 weight % or 25 weight %, etc.; the content of the initiator can be 0.01 weight %, 0.05 weight %, 0.1 weight %, 0.2 weight %, 0.3 weight %, 0.4 weight %, 0.5 weight %, 0.6 weight %, 0.7 weight %, 0.8 weight %, 0.9 weight % or 1 weight %, etc.

[0052] By using this composition, the in-situ solidified electrolyte can be injected and solidified between the positive electrode and the separator, significantly reducing the amount of liquid electrolyte that can flow, improving battery safety, and having a minimal impact on the overall impedance of the battery. As a result, the production process is highly similar to that of traditional lithium-ion batteries, facilitating industrial production and application.

[0053] In the composite solid electrolyte membrane of 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, and tantalum.

[0054] 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.

[0055] In the present invention, the first 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).

[0056] 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). The adhesive may 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).

[0057] 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.

[0058] 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 first lithium salt may be 0.3-17 wt%, preferably 1-10 wt%; the content of the adhesive may be 0-10 wt%.

[0059] 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.;

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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. In other words, the composite solid electrolyte membrane of the present invention can be a three-layer structure (substrate layer / composite electrolyte layer / first interfacial polymer electrolyte layer) or a four-layer structure (substrate layer / second interfacial polymer electrolyte layer / composite electrolyte layer / first interfacial polymer electrolyte layer).

[0065] In the present invention, the composition and thickness of the first and second interfacial polymer electrolyte layers may be the same or different. The thickness of the first and second interfacial polymer electrolyte layers may be independently 1-5 μm, preferably 2-3 μm.

[0066] The polymers in the first interfacial polymer electrolyte layer and the optional second interfacial polymer electrolyte layer each independently 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).

[0067] 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.

[0068] 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. The binder content can be 0-5% by weight, preferably 0-3% by weight.

[0069] In addition, relative to the total weight of the first interface polymer electrolyte layer or the second interface polymer electrolyte layer, the content of lithium salt can be, for example, 7 weight%, 10 weight%, 20 weight%, 30 weight%, 40 weight% or 44 weight%; the content of polymer can be, for example, 56 weight%, 60 weight%, 70 weight%, 80 weight%, 90 weight% or 93 weight%; the content of binder can be, for example, 0 weight%, 1 weight%, 2 weight%, 3 weight%, 4 weight% or 5 weight%.

[0070] 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.

[0071] The preparation method of the composite solid electrolyte membrane of the present invention may include the following steps:

[0072] (1) coating a composite electrolyte slurry on the substrate to form a composite electrolyte layer;

[0073] (2) forming a first interfacial polymer electrolyte layer on the composite electrolyte layer formed in step (1);

[0074] The composite electrolyte slurry contains a ceramic oxide, a first lithium salt, a first 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).

[0075] In the present invention, the first 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, and can be, for example, acetonitrile, N,N-dimethylformamide, tetrahydrofuran, isopropyl alcohol, etc. The amount of the first 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. In order to obtain a uniform composite electrolyte slurry, the ceramic oxide, the first lithium salt, the first solvent, and at least one selected from the first polymer and the binder are preferably thoroughly mixed by grinding, for example, ball milling at a rotation speed of 200-800 rpm for 1-5 hours.

[0076] 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.

[0077] According to some preferred embodiments of the present invention, the preparation method further includes: 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 the composite electrolyte layer. That is, the preparation method of the present invention may include the following steps:

[0078] (i) forming a second interfacial polymer electrolyte layer on the substrate;

[0079] (ii) coating a composite electrolyte slurry on the second interfacial polymer electrolyte layer formed in step (i) to form a composite electrolyte layer;

[0080] (iii) forming a first interfacial polymer electrolyte layer on the composite electrolyte layer formed in step (ii).

[0081] 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.

[0082] A second aspect of the present invention provides a method for preparing a lithium metal battery, the lithium metal battery comprising a positive electrode, a lithium metal negative electrode, a composite solid electrolyte membrane between the positive electrode and the lithium metal negative electrode, and a polymer electrolyte;

[0083] The preparation method comprises: hot pressing a composite solid electrolyte diaphragm and a lithium metal negative electrode, cooling the composite solid electrolyte diaphragm and the positive electrode to form a battery core, allowing an in-situ solidified electrolyte to infiltrate the composite solid electrolyte diaphragm from the positive electrode side, encapsulating and polymerizing the composite solid electrolyte diaphragm to form a polymer electrolyte;

[0084] The composite solid electrolyte membrane comprises a base layer, a composite electrolyte layer and a first interfacial polymer electrolyte layer stacked in sequence, wherein the composite electrolyte layer contains a ceramic oxide, a first 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%.

[0085] The preparation method of the second aspect of the present invention can be used to prepare the lithium metal battery of the first aspect. The structure and composition of the composite solid electrolyte membrane and polymer electrolyte, etc. can be the same as those of the first aspect and will not be repeated here.

[0086] The preparation method of a lithium metal battery may include, for example: laminating the polymer side of the above-mentioned composite solid electrolyte membrane to lithium metal, hot pressing at 80-100°C (such as 90°C) and a pressure of 0.5-1.5 MPa for 10-30 minutes; after cooling, laminating the battery with the positive electrode to obtain a battery cell, injecting an in-situ solidifying electrolyte on the positive electrode side, packaging the battery and heating and curing it, and obtaining a semi-solid / quasi-solid-state lithium metal battery after formation.

[0087] A third aspect of the present invention provides a battery pack, which includes the lithium metal battery of the present invention or the lithium metal battery obtained by the preparation method of the present invention.

[0088] Example

[0089] 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 all conventional methods unless otherwise specified.

[0090] The aluminum-doped lithium lanthanum zirconium oxide (Li 6.28 Al 0.24 La3Zr2O 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.

[0091] Preparation Example 1

[0092] This preparation example provides a three-layer composite solid electrolyte membrane, comprising 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.

[0093] 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.

[0094] First, a composite solid electrolyte slurry was prepared according to the following preparation steps.

[0095] 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.

[0096] 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.

[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] 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.

[0100] S20: Composite electrolyte layer preparation

[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] Preparation Example 2

[0105] This preparation example is used to illustrate the preparation of an in-situ curing electrolyte.

[0106] Ethylene carbonate (EC) and dimethyl carbonate (DMC) were measured in a volume ratio of 3:7, and LiPF6 was added to a final concentration of 1M and magnetically stirred until completely dissolved. Subsequently, polyethylene glycol methyl ether methacrylate (3 wt %), pentaerythritol tetraacrylate (1.5 wt %), and azobisisobutyronitrile (0.1 wt %) were added and stirred until completely dissolved.

[0107] Example 1

[0108] This embodiment is used to illustrate a method for preparing a semi-solid / quasi-solid-state lithium metal battery using the above-mentioned composite solid electrolyte membrane and in-situ solidified electrolyte.

[0109] The first interface polymer layer of the composite solid electrolyte membrane prepared in the above-mentioned preparation example 1 was attached to the lithium metal by hot pressing at 90°C and a pressure of 1 MPa for 10 minutes. 0.8 Co 0.1 Mn 0.1 The O2 positive electrode is encapsulated by a button battery, and 20 μL of the in-situ solidified electrolyte prepared in Preparation Example 2 is injected into the positive electrode side. The battery is encapsulated using an aluminum-plastic film using a button battery encapsulation machine and kept warm at 70°C for 12 hours. After formation, a semi-solid / quasi-solid-state lithium metal battery can be obtained.

[0110] Example 2

[0111] The difference between this embodiment and embodiment 1 is that LiNi 0.8 Co 0.1 Mn 0.1 The O2 positive electrode was replaced with a lithium iron phosphate positive electrode, and the remaining steps and parameters were exactly the same as in Example 1.

[0112] Comparative Example 1

[0113] The difference between this comparative example and Example 1 is that a 9 μm PE separator without a solid electrolyte layer is used, and no in-situ curing component is added to the electrolyte (i.e., polyethylene glycol methyl ether methacrylate, pentaerythritol tetraacrylate and azobisisobutyronitrile are included; the same below), and the remaining step parameters are exactly the same as in Example 1.

[0114] Comparative Example 2

[0115] The difference between this comparative example and Example 1 is that no in-situ curing component is added to the electrolyte, and the remaining steps and parameters are exactly the same as those in Example 1.

[0116] Test Case

[0117] This test example is used to illustrate the test of the batteries prepared in the above embodiments and comparative examples.

[0118] Test conditions: room temperature;

[0119] Test method: 0.33C constant current charge and discharge;

[0120] Test equipment: Xinwei battery test system, CT-4008Tn-mA

[0121] The capacity-voltage curve and capacity retention rate after 20 cycles of charge and discharge of the obtained semi-solid / quasi-solid-state lithium metal battery were measured, and the results are shown in Figures 4-6 and Table 1.

[0122] Table 1

[0123] It can be seen from the results in Table 1 that the diaphragm containing a solid electrolyte of the present invention can reduce the side reaction between the electrolyte and the positive and negative electrode materials of the battery and inhibit the growth of lithium dendrites, thereby improving the cycle stability of the battery, compared with the traditional PE diaphragm combined with the in-situ solidified electrolyte.

[0124] As can be seen from FIG4 , compared with a battery using a liquid electrolyte, the impedance increase of the battery using the in-situ solidified electrolyte of the present invention is smaller, and can fully meet the battery usage requirements.

[0125] As can be seen from FIG5 , compared with the battery using liquid electrolyte, the charge and discharge capacity of the battery using the in-situ solidified electrolyte of the present invention has no obvious attenuation.

[0126] As can be seen from FIG6 , the in-situ solidified electrolyte combined with the composite electrolyte separator system of the present invention is applicable to both lithium iron phosphate and ternary cathode material systems.

[0127] Examples 3-5

[0128] A semi-solid / quasi-solid-state lithium metal battery was prepared according to the method of Example 1, except that the in-situ curing components shown in the following table were used. The results are shown in Table 2.

[0129] Table 2

[0130] The results in Table 2 show that the in-situ curing system is suitable for various common monomers and cross-linking agents, and the ratio of monomer and cross-linking agent content has a significant impact on battery performance. A comparison of Example 3 with Example 1 shows that increasing the monomer and cross-linking agent content will affect the battery's ion transport efficiency and thus the battery's cycling stability.

[0131] 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 lithium metal battery, characterized in that: The lithium metal battery comprises a positive electrode, a lithium metal negative electrode, a composite solid electrolyte membrane between the positive electrode and the lithium metal negative electrode, and a polymer electrolyte that impregnates the composite solid electrolyte membrane; The composite solid electrolyte membrane comprises 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 first 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 %.

2. The lithium metal battery according to claim 1, wherein The polymer electrolyte includes a second lithium salt, a second solvent, and a second polymer.

3. The lithium metal battery according to claim 2, wherein: The second 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; and / or The second solvent is selected from one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, and ethylene glycol dimethyl ether; and / or The second polymer is a polymer selected from one or more of (meth) acrylic acid compounds, (meth) acrylic acid ester compounds, (meth) acrylonitrile compounds, unsaturated carbonates and alkylene oxide compounds, preferably selected from acrylic acid, methacrylic acid, methyl methacrylate, butyl acrylate, trifluoroethyl acrylate, acrylonitrile, ethylene carbonate, vinylene carbonate, A polymer formed from one or more of polyethylene glycol methyl ether methacrylate, ethylene oxide and 1,3-dioxolane.

4. The lithium metal battery according to any one of claims 1 to 3, wherein The polymer electrolyte is formed in situ from an in situ curing electrolyte.

5. The lithium metal battery according to any one of claims 1 to 4, wherein The content of the second lithium salt is 0.5-4M; relative to the total weight of the polymer electrolyte, the content of the second polymer is 1-50 wt%.

6. The lithium metal battery according to claim 1, wherein The first lithium salt is selected from one or more of lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(oxalatoborate), lithium bis(fluorosulfonyl)imide, and lithium difluorooxalatoborate; and / or 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; and / or The adhesive is selected from one or more of polytetrafluoroethylene, polyvinyl pyrrolidone, polyvinyl butyral, styrene-butadiene rubber latex, carboxymethyl cellulose, polyacrylic acid, and polyacrylonitrile; and / or The first polymer is selected from one or more of polyethylene oxide, polyvinylidene fluoride, and polyethylene glycol.

7. The lithium metal battery according to any one of claims 1 to 6, 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 first lithium salt is 0.3-17 wt %, and the content of the adhesive is 0-5 wt %.

8. The lithium metal battery according to any one of claims 1 to 7, wherein The base layer is a polyethylene film, a polypropylene film or a polyethylene-polypropylene composite film.

9. The lithium metal battery according to any one of claims 1 to 8, wherein A second interface polymer electrolyte layer is provided between the substrate layer and the composite electrolyte layer.

10. The lithium metal battery according to claim 9, wherein 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 lithium metal battery according to any one of claims 1 to 10, wherein: The lithium metal battery is a quasi-solid-state battery or a semi-solid-state battery.

12. A method for preparing a lithium metal battery, characterized in that: The lithium metal battery comprises a positive electrode, a lithium metal negative electrode, a composite solid electrolyte diaphragm between the positive electrode and the lithium metal negative electrode, and a polymer electrolyte; The preparation method comprises: hot pressing a composite solid electrolyte diaphragm and a lithium metal negative electrode, cooling the composite solid electrolyte diaphragm and the positive electrode to form a battery core, allowing an in-situ solidified electrolyte to infiltrate the composite solid electrolyte diaphragm from the positive electrode side, encapsulating and polymerizing the composite solid electrolyte diaphragm to form a polymer electrolyte; The composite solid electrolyte membrane comprises 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 first 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 %.

13. The preparation method according to claim 12, wherein: The in-situ solidification electrolyte comprises a second lithium salt, a second solvent, a monomer, a cross-linking agent and an initiator.

14. The preparation method according to claim 13, wherein: The second 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; and / or The second solvent is selected from one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, and ethylene glycol dimethyl ether; and / or The monomer is selected from one or more of (meth) acrylic acid compounds, (meth) acrylic acid ester compounds, (meth) acrylonitrile compounds, unsaturated carbonates and alkylene oxide compounds, preferably selected from one or more of acrylic acid, methacrylic acid, methyl methacrylate, butyl acrylate, trifluoroethyl acrylate, acrylonitrile, ethylene carbonate, vinylene carbonate, polyethylene glycol methyl ether methacrylate, ethylene oxide and 1,3-dioxolane; and / or The cross-linking agent is selected from one or more of organic peroxides, amines, oximes, organic sulfides, phenolic resins, organic dibasic acids, polyols, compounds containing unsaturated double bonds in the molecule and polythiol polymers; and / or The initiators are azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl, diisopropylbenzene peroxide, One or more of dibenzoyl peroxide or ammonium persulfide.

15. A battery pack, comprising the lithium metal battery according to any one of claims 1 to 11 or the lithium metal battery prepared by the method according to any one of claims 12 to 14.

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