Biomass solid electrolyte thin film and method of making same, membraneless solid state battery, solid state battery, and mechanical device

Abstract

The application provides a biomass solid-state electrolyte film and a preparation method thereof, a solid-state battery without a diaphragm, a solid-state battery and a mechanical device. The method comprises the following steps: (1) mixing biomass sugar, an alkaline lithium salt and a first solvent to obtain lithiumated biomass sugar, wherein the biomass sugar comprises at least one of chitosan, alginic acid and cellulose; (2) mixing the lithiumated biomass sugar, a polymer solid-state electrolyte monomer, an inorganic material, an active lithium salt, an initiator and a second solvent and then performing polymerization to obtain a precursor solution; and (3) applying the precursor solution on a substrate and drying to obtain a biomass solid-state electrolyte film. Thus, the solid-state electrolyte film prepared by the method has excellent mechanical strength and toughness and high processability, and the solid-state battery prepared by using the biomass solid-state electrolyte film has high ionic conductivity, can replace a diaphragm, can prepare a diaphragm-free battery and can improve the cycle life and safety of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state batteries, in particular to a biomass solid-state electrolyte film, a preparation method thereof, a separator-free solid-state battery, a solid-state battery and a mechanical device. BACKGROUND

[0002] Traditional lithium-ion batteries seriously affect the high-temperature performance and safety of the batteries due to the use of liquid electrolyte and separators, and the use of separators inevitably affects the energy density of the batteries. In order to improve the energy density and safety of lithium-ion batteries, a solid-state electrolyte film can be used to replace the separator and the liquid electrolyte. Biomass sugar widely exists in nature and has the advantages of low cost and wide source. If biomass sugar can be fully utilized as a raw material for battery production, not only the battery production cost is reduced, but also a new idea is provided for the development of solid-state batteries.

[0003] Solid-state batteries have many advantages, such as non-flammable or less flammable solid-state electrolyte, which can effectively inhibit the growth of lithium dendrites, prevent short circuit and improve the safety of solid-state batteries. However, there are still problems to be solved in completely replacing the separator and the electrolyte with the solid-state electrolyte, such as low ionic conductivity, short cycle life, poor mechanical and processing properties, high cost and the like. Using biomass sugar for battery production can overcome the above problems existing in the current solid-state batteries, which has very important significance. SUMMARY

[0004] The present application aims to at least partially solve one of the problems in the related art. To this end, one object of the present application is to provide a biomass solid-state electrolyte film, a preparation method thereof, a separator-free solid-state battery, a solid-state battery and a mechanical device.

[0005] In a first aspect, the present application provides a preparation method of a biomass solid-state electrolyte film. According to an embodiment of the present application, the method comprises:

[0006] (1) mixing biomass sugar, alkali lithium salt and first solvent to obtain lithiumated biomass sugar, wherein the biomass sugar comprises at least one of chitosan, alginic acid and cellulose;

[0007] (2) mixing the lithiumated biomass sugar, polymer solid-state electrolyte monomer, inorganic material, active lithium salt, initiator and second solvent and then polymerizing to obtain a precursor solution;

[0008] (3) applying the precursor solution on a substrate and drying to obtain a biomass solid-state electrolyte film.

[0009] According to the preparation method of the biomass solid-state electrolyte film in the above embodiment of the present application, first, biomass sugar, an alkaline lithium salt and an organic solvent are mixed to obtain a lithiated biomass sugar, the biomass sugar including at least one of chitosan, alginic acid and cellulose, the biomass sugar material being widely available and low in cost and being applicable to the positive and negative electrodes to replace the PVDF and PAA binders from the perspective of adhesion. The lithiated modified biomass sugar can graft lithium ions on the carboxyl or hydroxyl groups of the biomass sugar to form a single-ion conductor, which is beneficial to improving the lithium ion conductivity of the system. During the charging and discharging process, the electrolyte film will inevitably form a CEI film and a SEI film at the interface, thereby consuming part of the active lithium ions, and the lithiated biomass sugar can make up for the loss of the lithium ions, reduce the decrease of the ion conductivity caused by the loss of the active lithium ions and improve the interface stability and the first coulombic efficiency of the positive and negative electrodes.

[0010] The lithiated modified biomass sugar can reduce the carboxyl and hydroxyl groups rich in the original biomass sugar, the stability of these groups in the positive and negative electrodes being not as good as that of the PVDF polymer, the groups being decomposed under high pressure and corroding lithium metal under low pressure, so that the content of the remaining carboxylic acid and hydroxyl groups can be controlled by regulating the lithiation degree of the biomass sugar, the content of the unstable groups being much lower than that of the biomass sugar in the non-lithiated state, and the cycle performance of the battery is improved. Meanwhile, the carboxylic acid and hydroxyl groups can form a cross-linked structure through hydrogen bonds to improve the rigidity of the solid-state electrolyte film, and the lithiated modified biomass sugar can improve the flexibility of the solid-state electrolyte film, so that the mechanical properties of the solid-state electrolyte film as a whole are improved. In summary, the lithiated modified biomass sugar not only improves the mechanical properties and the ability to resist lithium dendrites of the solid-state electrolyte film, but also improves the cycle life of the battery.

[0011] Then, the lithiated biomass sugar, the polymer solid-state electrolyte monomer, the inorganic material and the active lithium salt are mixed to perform polymerization to obtain a precursor solution. The inventors have also found that the lithiated biomass sugar can improve the compatibility of the inorganic material and the polymer solid-state electrolyte monomer, the lithiated biomass sugar being able to form a covalent bond or a hydrogen bond with the hydroxyl or oxide on the surface of the inorganic material and form a hydrogen bond or a covalent bond with the other end of the polymer solid-state electrolyte monomer, so as to organically connect the inorganic material and the polymer solid-state electrolyte monomer, which not only can wet the surface of the inorganic material, but also can help the inorganic material to be uniformly dispersed. The lithiated biomass sugar is a linear polymer, which can greatly reduce the proportion of the crystalline region of the polymer, reduce the mutual entanglement between the chains, increase the mobility of different polymer segments and increase the sites for complexing and dissociating with lithium ions, so as to greatly enhance the lithium ion transport capacity. Moreover, the lithiated biomass sugar and the flexible polymer monomer have the characteristics of rigidity and flexibility, and through the method of rigidity and flexibility, the continuity and flatness of the interface contact between the solid-state electrolyte and the positive and negative electrodes are improved, and the structural degradation caused by the volume change of the electrodes is reduced.

[0012] Therefore, the solid-state electrolyte film prepared by the method has excellent mechanical strength and toughness and strong processability, the solid-state battery prepared by using the biomass solid-state electrolyte film has high ionic conductivity, can replace the separator, and can prepare a separator-free battery, and the battery has high cycle life and high safety performance, the method is suitable for production of the separator-free battery, the raw material cost is controllable, and the separator-free battery can be prepared in batches.

[0013] In addition, the method for preparing the biomass solid-state electrolyte film according to the above-mentioned embodiments of the application also has the following technical features:

[0014] In some embodiments of the application, in step (1), the mass ratio of the alkaline lithium salt to the biomass sugar is (1-35): 100.

[0015] In some embodiments of the application, the solid content of the system after mixing of the biomass sugar, the alkaline lithium salt and the first solvent is 10%-25%.

[0016] In some embodiments of the application, in step (1), the mixing temperature is 20°C-60°C.

[0017] In some embodiments of the application, the alkaline lithium salt includes at least one of lithium hydroxide, lithium carbonate and lithium hydride.

[0018] In some embodiments of the application, the first solvent includes at least one of N,N-dimethylacetamide, N-methylmorpholine-N-oxide, water, hydrochloric acid, formic acid, acetic acid and lactic acid.

[0019] In some embodiments of the application, in step (2), the mass ratio of the lithiated biomass sugar, the polymer solid-state electrolyte monomer, the inorganic material and the active lithium salt is (15-25):(5-10):(50-90):(10-20).

[0020] In some embodiments of the application, in step (2), the polymerization includes photopolymerization or thermal polymerization.

[0021] In some embodiments of the application, the light source used in the photopolymerization includes ultraviolet light or visible light, and the photopolymerization time is 1 min-60 min.

[0022] In some embodiments of the application, the heating temperature of the thermal polymerization is 30°C-120°C, and the heating time is 1 h-80 h.

[0023] In some embodiments of the application, the polymer solid-state electrolyte monomer comprises at least one of vinylidene fluoride, tetrafluoroethylene, epoxy ethylene, vinylidene fluoride-hexafluoropropylene, hexafluoropropylene, 1,3,5-trioxane, 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, 1,4-dioxolane, dithiolane, boroxine, vinylene carbonate, vinyl ethylene sulfite, vinylene trithiocarbonate, vinyl acetate, methyl vinyl sulfone, ethyl vinyl sulfone, dipropenyl phthalate, pentaerythritol tetraacrylate, methacrylate, ethylene glycol methacrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, ethylene glycol acrylate, methyl methacrylate, propylene carbonate, acrylonitrile, lactam, thioctic acid, cyclo-sulfurane, alkyl disulfide, tetramethylammonium chloride phosphonium, melamine, alkenylated monophosphine ligand, bisphosphine ligand, arginine methyl ester, arginine ethyl ester, acrylamide, methoxy polyethylene glycol, isocyanate, quaternary ammonium salt monomer, trifluoromethyl benzene boronic acid methylene imino diacetate, methacryloyloxyethyl, pentaerythritol acrylate, 1,3-propenyl-sulfolactone, 1,3-propenyl-sulfolactone, and acrylamide.

[0024] Preferably, the polymer solid-state electrolyte monomer comprises at least one of vinylene carbonate, methyl methacrylate, and acrylamide.

[0025] In some embodiments of the application, the inorganic material comprises at least one of inorganic solid-state electrolyte, inorganic ceramic.

[0026] In some embodiments of the application, the active lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bistrifluoromethanesulfonylimide, lithium bisfluorosulfonylimide, lithium bisoxalate borate, lithium difluorooxalate borate, and lithium difluorophosphate.

[0027] In some embodiments of the application, the inorganic solid-state electrolyte comprises at least one of oxide solid-state electrolyte, sulfide solid-state electrolyte, halide solid-state electrolyte, nitride solid-state electrolyte, boride solid-state electrolyte, hydride solid-state electrolyte.

[0028] In some embodiments of the application, the inorganic ceramic comprises at least one of metal oxide, nitride, carbide, boride.

[0029] In some embodiments of the application, in step (3), the drying comprises air blowing drying, vacuum drying, or heat-press drying.

[0030] In some embodiments of the application, the substrate comprises a positive electrode sheet, a negative electrode sheet, or a base film.

[0031] In a second aspect, the present application provides a biomass solid-state electrolyte film. According to an embodiment of the present application, the biomass solid-state electrolyte film is prepared by the method described above.

[0032] In a third aspect, the present application provides a membrane-free solid-state battery. According to an embodiment of the present application, the membrane-free solid-state battery comprises the biomass solid-state electrolyte film described above.

[0033] In a fourth aspect, the present application provides a solid-state battery. According to an embodiment of the present application, the solid-state battery comprises the biomass solid-state electrolyte film described above.

[0034] In a fifth aspect, the present application provides a mechanical device. According to an embodiment of the present application, the mechanical device comprises the membrane-free solid-state battery or the solid-state battery described above.

[0035] The present application has at least the following technical effects:

[0036] (1) The present application uses biomass sugar to prepare a solid-state electrolyte. Biomass sugar materials are widely available and can be obtained from nature, and are environmentally friendly, water-soluble, renewable, and low-cost. At the same time, biomass sugar has abundant polar functional groups, which can improve the electrochemical performance of the solid-state battery and the compatibility of the positive and negative electrode interfaces, thereby improving the ionic conductivity of the solid-state battery.

[0037] (2) The present application modifies biomass sugar by lithiation, grafting lithium ions onto the carboxyl or hydroxyl groups of biomass sugar to form a single-ion conductor, thereby improving the lithium ion conductivity of the system. Lithiated biomass sugar can compensate for the active lithium ions consumed in the formation of CEI and SEI films, thereby improving the stability of the positive and negative electrode interfaces and the first coulombic efficiency. By controlling the degree of lithiation, the content of residual carboxylic acid and hydroxyl groups can be controlled. Carboxylic acid and hydroxyl groups can form cross-linked structures through hydrogen bonds. Since the content of unstable groups is much lower than that of un-lithiated biomass sugar at this time, the cross-linked structure formed by hydrogen bonds not only improves the mechanical properties of the solid-state electrolyte film and the ability to resist lithium dendrites, but also improves the cycle life of the battery.

[0038] (3) Lithiated biomass sugar can improve the compatibility of inorganic materials and polymer solid-state electrolyte monomers, thereby organically connecting inorganic materials and polymer solid-state electrolyte monomers. It not only can wet the surface of inorganic materials, but also can help the uniform dispersion of inorganic materials.

[0039] (4) Lithiated biomass sugar is a linear polymer. Through cross-linking polymerization with monomers, the chain segment mobility of the polymer is effectively increased, greatly enhancing the lithium ion transport. In addition, by combining the characteristics of rigid biomass sugar and flexible polymer monomers, a rigid-flexible method is used to improve the continuity and flatness of the interface contact between the positive and negative electrodes, and to reduce the structural degradation caused by the volume change of the electrode. DETAILED DESCRIPTION

[0040] All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present application without creative labor fall within the scope of protection of the present application.

[0041] In a first aspect, the present application provides a method for preparing a biomass solid-state electrolyte film. According to an embodiment of the present application, the method comprises:

[0042] S100: mixing biomass sugar, alkali lithium salt and first solvent

[0043] In this step, the biomass sugar, alkali lithium salt and first solvent are mixed to obtain a lithiated biomass sugar, wherein the biomass sugar comprises at least one of chitosan, alginic acid and cellulose. By modifying the biomass sugar through lithiation, lithium ions can be grafted onto the carboxyl or hydroxyl groups of the biomass sugar to form a single-ion conductor, which is conducive to improving the lithium ion conductivity of the system. During the charging and discharging process, the electrolyte film will inevitably form a CEI film and a SEI film at the interface, thereby consuming part of the active lithium ions, and the lithiated biomass sugar can make up for the loss of lithium ions, reduce the decrease in ion conductivity caused by the loss of active lithium ions, and improve the stability of the positive and negative electrode interfaces and the first coulombic efficiency. The lithiated modified biomass sugar can reduce the content of carboxyl and hydroxyl groups rich in the original biomass sugar. The stability of these groups in the positive and negative electrodes is not as good as that of PVDF polymer, and they will decompose under high pressure and corrode lithium metal under low pressure. Therefore, the content of the remaining carboxylic acid and hydroxyl groups can be controlled by adjusting the degree of lithiation of the biomass sugar, and the carboxylic acid and hydroxyl groups can form a cross-linked structure through hydrogen bonds. Since the content of unstable groups at this time is much lower than that of the biomass sugar without lithiation, the hydrogen bond cross-linked structure not only improves the mechanical properties of the solid-state electrolyte film and the ability to resist lithium dendrites, but also improves the cycle life of the battery.

[0044] According to an embodiment of the present application, the first solvent comprises at least one of N,N-dimethylacetamide, N-methylmorpholine-N-oxide, water, hydrochloric acid, formic acid, acetic acid and lactic acid.

[0045] According to an embodiment of the present application, the alkali lithium salt comprises at least one of lithium hydroxide, lithium carbonate and lithium hydride. By selecting the above alkali lithium salt, the biomass sugar can be effectively modified, so that lithium ions are successfully grafted onto the carboxyl or hydroxyl groups of the biomass sugar to form a single-ion conductor and improve the lithium ion conductivity of the system.

[0046] According to an embodiment of the present application, the mass ratio of the basic lithium salt to the biomass sugar is (1-35):100. For example, the mass ratio is 1:100, 5:100, 10:100, 15:100, 20:100, 25:100, 30:100, 35:100, etc. The inventors have found that controlling the mass ratio of the basic lithium salt to the biomass sugar in the above range can reduce the content of carboxylic acid and hydroxyl groups in the biomass sugar, reduce the content of unstable groups, and improve the cycle stability of the battery; at the same time, it can also avoid that the content of residual carboxylic acid and hydroxyl groups in the biomass sugar is too low, and reduce the mechanical properties of the electrolyte membrane.

[0047] According to an embodiment of the present application, the solid content of the system after mixing the biomass sugar, the basic lithium salt, and the first solvent is 10%-25%. The inventors have found that controlling the solid content of the system after mixing the biomass sugar, the basic lithium salt, and the first solvent in the above range is helpful for the biomass sugar to be fully dissolved and for the lithiation reaction to proceed.

[0048] According to an embodiment of the present application, the mixing temperature is 20°C-60°C. Controlling the mixing temperature in the above range is helpful for the biomass sugar to be quickly and fully dissolved in the first solvent.

[0049] S200: mixing the lithiated biomass sugar, the polymer solid electrolyte monomer, the inorganic material, the active lithium salt, the initiator, and the second solvent to perform polymerization

[0050] In this step, the lithiated biomass sugar, the polymer solid electrolyte monomer, the inorganic material, the active lithium salt, the initiator, and the second solvent are mixed to perform polymerization to obtain a precursor solution. The inventors have found that the lithiated biomass sugar can improve the compatibility of the inorganic material and the polymer solid electrolyte monomer, the lithiated biomass sugar can form covalent bonds or hydrogen bonds with the hydroxyl groups or oxides on the surface of the inorganic material, and the other end can form hydrogen bonds or covalent bonds with the polymer solid electrolyte monomer, thereby organically connecting the inorganic material and the polymer solid electrolyte monomer, which not only can wet the surface of the inorganic material, but also can help the inorganic material to be uniformly dispersed. The lithiated biomass sugar is a linear polymer, which can greatly reduce the proportion of the crystalline region of the polymer, reduce the mutual entanglement between the chains, increase the mobility of different polymer chain segments, increase the sites for complexation and dissociation with lithium ions, and thereby greatly enhance the lithium ion transport capacity. Moreover, by combining the characteristics of the rigid biomass sugar and the flexible polymer monomer, the continuity and flatness of the interface contact between the solid electrolyte and the positive and negative electrodes are improved, and the structural degradation caused by the volume change of the electrodes is reduced.

[0051] It should be noted that the active lithium salt, the second solvent, and the initiator are conventional materials in the art, and those skilled in the art can select them according to actual needs. For example, the active lithium salt includes, but is not limited to, at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethane)xanimide, lithium bis(fluorosulfonyl)imide, lithium dioxalate borate, lithium difluorooxalate borate, and lithium difluorophosphate. The second solvent includes, but is not limited to, at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, N-methylpyrrolidone, acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, ethyl acetate, butyl butyrate, chloroform, dichloromethane, diethyl ether, toluene, acetone, and tetrahydrofuran. Initiators include, but are not limited to, at least one of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), azobisisovalerate (AMBN), dimethyl azobisisobutyrate (AIBME), azoisobutyl cyanoformamide (CABN), diisopropyl azodicarbonate (DIAD), azobiscyclohexylformitrile (ACCN), benzoyl peroxide (BPO), di(2-ethylhexyl) percarbonate (EHP), tert-butyl peroxide (TBPB), methyl ethyl ketone peroxide (MEKP), mercaptobenzene, thiolates, and alkyl thiols.

[0052] According to embodiments of the present invention, the mass ratio of lithium-ionized biomass sugar, polymer solid electrolyte monomer, inorganic material, and active lithium salt is (15~25):(5~10):(50~90):(10~20). The inventors have discovered that by controlling the mass ratio of lithium-ionized biomass sugar, polymer solid electrolyte monomer, inorganic material, and active lithium salt within the above range, the rigid segments in the biomass sugar and the flexible segments in the polymer complement each other, jointly regulating the mechanical strength and flexibility of the solid electrolyte membrane, achieving a balance of rigidity and flexibility; furthermore, a high ceramic content helps improve the electrochemical stability and thermal stability of the electrolyte membrane at high temperatures.

[0053] According to embodiments of the present invention, polymerization includes photopolymerization or thermal polymerization.

[0054] According to an embodiment of the present invention, the light source used for photopolymerization includes ultraviolet light or visible light, and the photopolymerization time is 1 min to 60 min.

[0055] According to an embodiment of the present invention, the heating temperature for the thermal polymerization is 30°C to 120°C, and the heating time is 1 hour to 80 hours.

[0056] According to embodiments of the present invention, the polymer solid electrolyte monomers include vinylidene fluoride, tetrafluoroethylene, ethylene oxide, vinylidene fluoride-hexafluoropropylene, hexafluoropropylene, 1,3,5-trioxane, 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, 1,4-dioxolane, dithiopentane, cycloboroxane, vinylene carbonate, vinyl sulfite, trithiovinyl carbonate, vinyl acetate, methyl vinyl sulfone, ethyl vinyl sulfone, phthalate diacrylate, pentaerythritol tetraacrylate, methacrylate, ethylene glycol monoacrylate, etc. The following are at least one of the following: alcohol methacrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, ethylene glycol acrylate, methyl methacrylate, propylene carbonate, acrylonitrile, lactam, thioctic acid, cyclothioalkylene, alkyl disulfide, tetramethylphosphorus chloride, melamine, alkenylated monophosphine ligand, bisphosphine ligand, arginine methyl ester, arginine ethyl ester, acrylamide, methoxy polyethylene glycol, isonitrile, quaternary ammonium salt monomer, trifluoromethylphenylboronic acid methyliminodiacetic acid, methacryloyloxyethyl ester, pentaerythritol acrylate, 1,3-propenyl-sulfonate lactone, 1,3-propenyl-sulfonate lactone and acrylamide.

[0057] Preferably, the polymer solid electrolyte monomer includes at least one of vinylene carbonate, methyl methacrylate, and acrylamide.

[0058] According to embodiments of the present invention, the inorganic material includes at least one of inorganic solid electrolytes and inorganic ceramics.

[0059] According to an embodiment of the present invention, the inorganic solid electrolyte includes at least one of oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, nitride solid electrolyte, boride solid electrolyte, and hydride solid electrolyte.

[0060] As an example, oxide solid electrolytes include, but are not limited to, one or more combinations of lithium lanthanum zirconium oxide (LLZO), niobium-doped lithium lanthanum zirconium oxide (LLZNO), tantalum-doped lithium lanthanum zirconium oxide (LLZTO), niobium-tantalum dual-doped lithium lanthanum zirconium oxide (LLZNTO), lithium lanthanum titanium oxide (LLTO), lithium titanium aluminum phosphate (LATP), titanium yttrium phosphate (LYTP), lithium germanium aluminum phosphate (LAGP), and lithium aluminum oxide (LiAlO2).

[0061] As an example, sulfide solid electrolytes include, but are not limited to, one or more combinations of lithium germanium phosphorus sulfide (LGPS), lithium phosphorus sulfide chloride (LPSCl), lithium thiophosphate (LPS), and glassy sulfides (Li2S-P2S5, Li2S-SiS2, Li2S-B2S3).

[0062] As examples, halide solid electrolytes include, but are not limited to, Li3OCl, LiI, Li5ZnI4, and Li3OCl.1-x Br x (where 0 < x < 1), Li2XCl4 (X includes Cd and / or Mg), Li2X′I4 (X′ includes Cd and / or Zn), LiMCl5X′′ (M includes one or more of La, Ta, Nb; X′′ includes any one of O, Cl, F, OH), Li 3-x Zr x M′ 1-x Cl6 (M′ includes one or more of Y, Er, Yb, Ho, Lu, 0 ≤ x ≤ 1) or a combination of one or more thereof.

[0063] As an example, the nitride solid electrolyte includes, but is not limited to, one or a combination of one or more of LiPON, Li3N, Li7PN4, LiSi2N3.

[0064] As an example, the boride solid electrolyte includes, but is not limited to, one or a combination of one or more of Li2B4O7, Li2O - B2O3 - P2O5, Li 6+2x [B 10 S 18 S x or a combination of one or more thereof.

[0065] As an example, the hydride solid electrolyte includes, but is not limited to, one or a combination of one or more of Li3AlH6, LiBH4, LiNH2, Li2NH, LiBH4 - LiNH2, LiBH4 - LiX (X = Cl, Br, I).

[0066] According to an embodiment of the present invention, the inorganic ceramic includes at least one of metal oxides, nitrides, carbides, and borides.

[0067] As an example, the metal oxide includes, but is not limited to, at least one of alumina, titanium dioxide, zirconium dioxide, and magnesium oxide.

[0068] As an example, the nitride includes, but is not limited to, at least one of silicon nitride, titanium nitride, aluminum nitride, boron nitride, magnesium nitride, and zirconium nitride.

[0069] As an example, the carbide includes at least one of silicon carbide and boron carbide.

[0070] As an example, the boride includes, but is not limited to, at least one of silicon boride, vanadium boride, magnesium boride, and titanium boride.

[0071] S300: Apply the precursor solution on the substrate and dry

[0072] In this step, the precursor solution obtained in S200 is applied to a substrate and dried to obtain a biomass solid electrolyte film. It should be noted that the application method is conventional in the art, such as coating or spraying.

[0073] According to embodiments of the present invention, drying includes forced-air drying, vacuum drying, or hot-press drying.

[0074] According to embodiments of the present invention, the substrate includes a positive electrode, a negative electrode, or a base film. For example, a precursor solution can be applied to the positive or negative electrode and dried to form an electrode-solid electrolyte film assembly. Alternatively, the precursor solution can be applied to at least one side of the base film and dried to form a biomass solid electrolyte film on at least one side of the base film.

[0075] The base film is a conventional material in the art, including, for example, polyethylene terephthalate (PET), ethyl terephthalate, polybutylene terephthalate, polyethylene (PE), polypropylene (PP), poly-1-butene, polyisobutylene, polybutadiene, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polyacrylonitrile, polyvinylidene fluoride-hexafluoropropylene, cellulose, polyvinyl alcohol, polymethyl methacrylate, polyurethane, polycarbonate, polysulfide, alumina film, polyimide nonwoven film, polyarylsulfone nonwoven film, silicone release film, non-silicone release film, fluorine release film, or glass fiber. Further, the thickness of the base film is 1 μm to 50 μm, preferably 2 μm to 20 μm.

[0076] Preferably, the substrate is a positive electrode or a negative electrode. Applying the precursor solution to the positive or negative electrode and drying it can increase the contact area between the solid electrolyte layer and the electrode, reduce the interfacial impedance between the solid electrolyte layer and the electrode, and the resulting positive electrode-solid electrolyte thin film assembly and negative electrode-solid electrolyte thin film assembly have excellent ionic conductivity.

[0077] In a second aspect, the present invention provides a biomass solid electrolyte film. According to an embodiment of the present invention, the biomass solid electrolyte film is prepared using the method described above. Therefore, solid-state batteries prepared using this biomass solid electrolyte film exhibit high ionic conductivity, long cycle life, and the biomass solid electrolyte film possesses excellent mechanical strength and toughness, as well as strong processability. It should be noted that the features and advantages described above for the method of preparing the biomass solid electrolyte film also apply to this biomass solid electrolyte film, and will not be repeated here.

[0078] According to embodiments of the present invention, the thickness of the biomass solid electrolyte film is 5µm to 10µm. When the thickness of the solid electrolyte film is too low, lithium dendrites are prone to puncture, leading to a short circuit in the battery. When the thickness of the solid electrolyte film is too high, the ion transport distance increases, affecting the rate performance of the battery. Therefore, the thickness of the biomass solid electrolyte film in this application is controlled within the above-mentioned range, resulting in a battery with higher safety and rate performance.

[0079] In a third aspect, the present invention provides a separatorless solid-state battery. According to an embodiment of the present invention, the separatorless solid-state battery includes the aforementioned biomass solid electrolyte membrane. Therefore, the separatorless solid-state battery exhibits high ionic conductivity, long cycle life, and reliable safety. It should be noted that the features and advantages described above for the biomass solid electrolyte membrane also apply to this separatorless solid-state battery, and will not be repeated here.

[0080] In a fourth aspect, the present invention provides a solid-state battery. According to an embodiment of the invention, the solid-state battery includes the aforementioned biomass solid electrolyte film. Therefore, the solid-state battery exhibits high ionic conductivity, long cycle life, and reliable safety. It should be noted that the features and advantages described above for the biomass solid electrolyte film also apply to this solid-state battery, and will not be repeated here.

[0081] According to an embodiment of the present invention, a solid-state battery includes a positive electrode, a solid electrolyte film, and a negative electrode. For example, the positive electrode, the solid electrolyte film, and the negative electrode are sequentially stacked and hot-pressed to prepare an integrated solid-state battery.

[0082] As an example, the main materials of the positive electrode include, but are not limited to, one or more combinations of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and lithium vanadium phosphate; the main materials of the negative electrode include, but are not limited to, one or more combinations of graphite, graphene, carbon nanotubes, silicon-based alloys, silicon-oxygen negative electrodes, silicon-carbon negative electrodes, lithium metal, lithium alloy negative electrodes, lithium titanium oxides, transition metal oxides, and transition metal sulfides.

[0083] In a fifth aspect, the present invention provides a mechanical device. According to embodiments of the invention, the mechanical device comprises the aforementioned membrane-free solid-state battery or the aforementioned solid-state battery. Therefore, the mechanical device has a longer driving range, higher safety performance, and a longer cycle life. It should be noted that the features and advantages described above for solid-state batteries also apply to this mechanical device, and will not be repeated here.

[0084] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0085] Example 1

[0086] (1) Chitosan, lithium hydroxide and aqueous solution were mixed at 45°C to obtain lithium-ionized chitosan, wherein the mass ratio of alkaline lithium salt to biomass sugar was 20:100, and the solid content of the system after mixing was 15%;

[0087] (2) The lithium-ionized chitosan, vinylene carbonate, LLZTO, LiTFSI, AIBN and DMF are mixed and polymerized at 60°C for 12 h to obtain a precursor solution; wherein the mass ratio of lithium-ionized biomass sugar, polymer solid electrolyte monomer, inorganic material and active lithium salt is 15:5:70:10, the amount of initiator added is 1 wt% of polymer solid electrolyte monomer, and the solid content of the precursor solution is 50%;

[0088] (3) The precursor solution was applied to PET and dried at 60°C for 12 hours to obtain a biomass solid electrolyte film.

[0089] Example 2

[0090] Unlike Example 1, the biomass sugar in this example is alginic acid.

[0091] Example 3

[0092] Unlike Example 1, the biomass sugar in this example is cellulose.

[0093] Example 4

[0094] Unlike Example 1, the mass ratio of alkaline lithium salt to biomass sugar in this example is 10:100.

[0095] Example 5

[0096] Unlike Example 1, the mass ratio of alkaline lithium salt to biomass sugar in this example is 30:100.

[0097] Example 6

[0098] Unlike Example 1, the mass ratio of alkaline lithium salt to biomass sugar in this example is 40:100.

[0099] Example 7

[0100] Unlike Example 1, the mass ratio of lithium-ionized biomass sugar, polymer solid electrolyte monomer, inorganic material, and active lithium salt in this example is 20:7:58:15.

[0101] Example 8

[0102] Unlike Example 1, the mass ratio of lithium-ionized biomass sugar, polymer solid electrolyte monomer, inorganic material, and active lithium salt in this example is 25:10:50:15.

[0103] Example 9

[0104] Unlike Example 1, the mass ratio of lithium-ionized biomass sugar, polymer solid electrolyte monomer, inorganic material, and active lithium salt in this example is 30:15:45:30.

[0105] Example 10

[0106] Unlike Example 1, the polymer solid electrolyte monomer in this example is methyl methacrylate.

[0107] Example 11

[0108] Unlike Example 1, the polymer solid electrolyte monomer in this example is acrylamide.

[0109] Example 12

[0110] Unlike Example 1, the inorganic material in this example is the boride Li2B4O7.

[0111] Example 13

[0112] Unlike Example 1, the inorganic material in this example is boron nitride.

[0113] Example 14

[0114] Unlike Example 1, the active lithium salt in this example is LiDFOB.

[0115] Example 15

[0116] Unlike Example 1, the active lithium salt in this example is lithium difluorophosphate.

[0117] Example 16

[0118] Unlike Example 1, the initiator in this example is BPO.

[0119] Comparative Example 1

[0120] Unlike Example 1, the biomass sugar in this example is not lithiumized.

[0121] Comparative Example 2

[0122] Unlike Example 1, no polymer solid electrolyte monomer is added in this example.

[0123] Comparative Example 3

[0124] Unlike Example 1, this example does not add polymer solid electrolyte monomers, but instead adds polymer solid electrolyte polyvinyl carbonate.

[0125] The following describes the battery performance testing process and results:

[0126] (1) Ionic conductivity testing method:

[0127] Assemble a stainless steel-solid electrolyte-stainless steel symmetric cell and perform electrochemical impedance spectroscopy on the cell. The frequency range is 0.1 Hz-4 MHz and the test amplitude is 5 mV.

[0128] Solid-state battery assembly:

[0129] 1) Positive electrode sheet: The mass ratio of lithium nickel cobalt manganese oxide, PVDF and conductive carbon black is 96:2:2.

[0130] 2) Use lithium metal anode as the anode plate.

[0131] 3) Assemble a solid-state battery by stacking the positive electrode, solid electrolyte, and negative electrode in sequence.

[0132] 4) The battery was tested using the Xinwei Battery Performance Testing System. The voltage range was 2.7V-4.3V, and the charge / discharge conditions were 1 cycle at room temperature. After 100 cycles, the corresponding capacity retention rate was calculated.

[0133] (2) Tensile strength test method:

[0134] The solid electrolyte was cut into strips of 8 cm × 2 cm and its tensile strength was tested using a tensile testing machine at a tensile rate of 20 mm / min.

[0135] (3) Heat shrinkage rate test:

[0136] The solid electrolyte membrane was cut into 10 cm × 10 cm square strips, placed in an oven at 150°C for 1 hour, and the solid electrolyte membrane was removed. The difference between the current length and width and the original length and width was measured, and the difference was divided by the original length and width to obtain the shrinkage rate.

[0137] The results of testing the batteries of Examples 1-16 and Comparative Examples 1-3 according to the above process and method are shown in Table 1:

[0138] Table 1

[0139]

[0140] As can be seen from the data in Table 1, appropriate lithiation of biomass sugar in Examples 1 and 4-5 helps to improve ionic conductivity while reducing residual carboxyl and hydroxyl groups; excessive lithiation in Example 6 leads to a reduction in the number of carboxyl and hydroxyl groups that can complex with lithium ions, thus reducing ionic conductivity; the reduction in the number of residual carboxyl and hydroxyl groups also leads to a reduction in the number of hydrogen bonds formed and a weakening of cross-linking between the polymer solid electrolyte monomer, thus reducing the tensile strength, elongation and thermal stability of the electrolyte membrane.

[0141] As can be seen from Examples 1 and 7-9, reducing the content of inorganic materials with high ionic conductivity and high electrochemical window will lead to a decrease in the ionic conductivity of the electrolyte membrane and a decrease in the cycle stability of the matched high voltage cathode; at the same time, since inorganic materials have extremely high thermal stability, the component with high inorganic material content has a lower thermal shrinkage rate.

[0142] As can be seen from Example 1 and Comparative Example 1, lithium modification of biomass sugar helps to improve the ionic conductivity of the electrolyte membrane, and reducing the number of carboxyl and hydroxyl groups in biomass sugar helps to improve the cycle stability of the electrolyte membrane in high voltage cathode; and the reduction in the number of carboxyl and hydroxyl groups helps to improve the flexibility of the electrolyte membrane.

[0143] As can be seen from Example 1 and Comparative Examples 2-3, cross-linking polymerization of biomass sugar and polymer solid electrolyte monomers can effectively increase the polymer chain segment mobility and reduce the polymer crystallization region, thereby enhancing lithium-ion transport.

[0144] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a biomass solid electrolyte film, characterized in that, include: (1) A mixture of biomass sugar, alkaline lithium salt and a first solvent is used to obtain lithium-ionized biomass sugar, wherein the biomass sugar includes at least one of chitosan, alginate and cellulose; (2) The lithium-ionized biomass sugar, polymer solid electrolyte monomer, inorganic material, active lithium salt, initiator and second solvent are mixed and polymerized to obtain a precursor solution; (3) The precursor solution is applied to the substrate and dried to obtain a biomass solid electrolyte film; The inorganic material includes at least one of inorganic solid electrolytes and inorganic ceramics.

2. The method according to claim 1, characterized in that, In step (1), the mass ratio of the alkaline lithium salt to the biomass sugar is (1~35):100; And / or, the solid content of the system after mixing the biomass sugar, the alkaline lithium salt and the first solvent is 10%~25%.

3. The method according to claim 1 or 2, characterized in that, In step (1), the mixing temperature is 20℃~60℃; And / or, the alkaline lithium salt includes at least one of lithium hydroxide, lithium carbonate, and lithium hydride.

4. The method according to claim 1 or 2, characterized in that, Step (2) must satisfy at least one of the following conditions: (a) The mass ratio of the lithium-ionized biomass sugar, the polymer solid electrolyte monomer, the inorganic material, and the active lithium salt is (15~25):(5~10):(50~90):(10~20); (b) The polymerization includes photopolymerization or thermal polymerization; (c) The polymer solid electrolyte monomers include vinylidene fluoride, tetrafluoroethylene, ethylene oxide, vinylidene fluoride-hexafluoropropylene, hexafluoropropylene, 1,3,5-trioxane, 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, 1,4-dioxolane, dithiopentane, cycloboroxane, vinylene carbonate, vinyl sulfite, trithiovinyl carbonate, vinyl acetate, methyl vinyl sulfone, ethyl vinyl sulfone, phthalate diacrylate, pentaerythritol tetraacrylate, methacrylate, and ethylene glycol. The following are at least one of the following: methacrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, ethylene glycol acrylate, methyl methacrylate, propylene carbonate, acrylonitrile, lactam, lipoic acid, cyclothiocyanates, alkyl disulfides, tetramethylphosphorus chloride, melamine, alkenylated monophosphine ligand, bisphosphine ligand, arginine methyl ester, arginine ethyl ester, methoxy polyethylene glycol, isocyanate, quaternary ammonium salt monomer, trifluoromethylphenylboronic acid methyliminodiacetic acid, methacryloyloxyethyl ester, 1,3-propenyl-sulfonate lactone, and acrylamide; (d) The active lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxarate borate, lithium difluorooxarate borate, and lithium difluorophosphate.

5. The method according to claim 4, characterized in that, The light source used for photopolymerization includes ultraviolet light or visible light, and the photopolymerization time is 1 min to 60 min.

6. The method according to claim 4, characterized in that, The heating temperature for the thermal polymerization is 30℃~120℃, and the heating time is 1h~80h.

7. The method according to claim 4, characterized in that, The polymer solid electrolyte monomer is at least one of vinylene carbonate, methyl methacrylate, and acrylamide.

8. The method according to claim 4, characterized in that, The inorganic solid electrolyte includes at least one of oxide solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, nitride solid electrolyte, boride solid electrolyte and hydride solid electrolyte; And / or, the inorganic ceramic includes at least one of metal oxides, nitrides, carbides and borides.

9. The method according to claim 1 or 2, characterized in that, In step (3), the drying includes forced air drying, vacuum drying, or hot pressing drying; And / or, the substrate includes a positive electrode sheet, a negative electrode sheet, or a base film.

10. A biomass solid electrolyte film, characterized in that, Prepared using the method described in any one of claims 1-9.

11. A membrane-free solid-state battery, characterized in that, Includes the biomass solid electrolyte membrane as described in claim 10.

12. A solid-state battery, characterized in that, Includes the biomass solid electrolyte membrane as described in claim 10.

13. A mechanical device, characterized in that, This includes the membraneless solid-state battery of claim 11 or the solid-state battery of claim 12.

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