Solid-state battery and method of manufacturing the same

Abstract

The application provides a solid-state battery and a preparation method thereof, and belongs to the technical field of secondary batteries.The solid-state battery comprises a solid-state electrolyte film, the solid-state electrolyte film comprises a sulfide electrolyte and a binder, the binder comprises at least one of a fluorine-containing monomer, a fluorine-containing dimer and a fluorine-containing multimer, and the molar ratio of carbon elements to fluorine elements on the surface of the binder is 0.41-1.The solid-state electrolyte film assembled in the solid-state battery of the application has higher mechanical strength and ionic conductivity under the action of the modified binder with the same content, can effectively solve the problems of electrolyte film rupture and battery short circuit caused by electrode volume change during the charging and discharging process of the solid-state battery, and improves the service life and cycle performance of the solid-state battery.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, specifically to a solid-state battery and its preparation method. Background Technology

[0002] All-solid-state batteries use non-flammable solid electrolyte membranes instead of organic liquid electrolytes and polymer separators, simplifying battery design, improving battery safety and energy density, and expanding the battery's operating temperature range. Solid electrolyte membranes primarily use oxide, sulfide, and polymer electrolytes. Among these, sulfide electrolytes have attracted significant attention due to their high ionic conductivity, low Young's modulus, and ease of large-scale processing. In particular, solid electrolyte membranes based on sulfide electrolytes, when matched with high-capacity positive and negative electrodes, can enable solid-state batteries to achieve energy densities exceeding 500 Wh / kg, making them a promising future power source.

[0003] The presence of binders in solid-state electrolyte membranes (SSMEs) results in lower ionic conductivity compared to sulfide electrolytes. Furthermore, the decrease in ionic conductivity becomes more pronounced with increasing binder percentage. To maintain high ionic conductivity, the binder percentage should be below 10%. However, low binder content can lead to poor mechanical strength, making the membrane more susceptible to uneven stress and rupture during battery assembly or charge-discharge cycles, potentially causing short circuits and impacting the cycle life of all-solid-state batteries.

[0004] Therefore, it is necessary to design a solid-state battery and its fabrication method to solve the above problems. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention provides a solid-state battery and its preparation method to improve the technical problem that the sulfide solid electrolyte membrane in the existing solid-state battery is difficult to achieve both high ionic conductivity and high mechanical strength.

[0006] To achieve the above and other related objectives, the present invention provides a solid-state battery comprising a solid electrolyte membrane, wherein the solid electrolyte membrane comprises a sulfide electrolyte and a binder, wherein the binder comprises at least one of a fluorine-containing monomer, dimer, and polymer, and the molar ratio of carbon to fluorine on the surface of the binder is 0.41 to 1.

[0007] In one example of the present invention, the molar ratio of carbon to fluorine on the surface of the adhesive is 0.41 to 0.88.

[0008] In one example of the present invention, the thickness of the solid electrolyte membrane is 30–60 μm.

[0009] In one example of the present invention, the adhesive includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-hexafluoropropylene copolymer, and ethylene-tetrafluoroethylene copolymer.

[0010] In one example of the present invention, the mass of the sulfide electrolyte is 90% to 99.5% of the mass of the solid electrolyte membrane; and the mass of the binder is 0.5% to 10% of the mass of the solid electrolyte membrane.

[0011] In one example of the present invention, the ionic conductivity of the sulfide electrolyte is greater than 1 mS / cm.

[0012] In one example of the present invention, the particle size of the sulfide electrolyte is 1 to 10 μm.

[0013] In one example of the present invention, the sulfide electrolyte includes Li3PS4 and Li7P3S. 11 Li 10 GeP2S 12 Li 10 SnP2S 12 Li6PS5Br, Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 At least one of them.

[0014] The present invention also provides a method for preparing a solid-state battery according to any of the above examples, the method comprising providing a positive electrode, a solid electrolyte membrane, and a negative electrode; assembling the positive electrode, the solid electrolyte membrane, and the negative electrode into a cell, and encapsulating the cell to obtain a solid-state battery;

[0015] The method for preparing the solid electrolyte membrane includes:

[0016] A sulfide electrolyte and a binder are provided, the binder comprising at least one of a fluorinated monomer, dimer, and polymer;

[0017] The adhesive is surface modified so that the molar ratio of carbon to fluorine on the surface of the adhesive is 0.41 to 1.

[0018] The sulfide electrolyte is mixed with the binder to form a solid electrolyte membrane.

[0019] In one example of the present invention, surface modification of the binder includes: plasma etching the surface of the binder to remove fluorine atoms from the surface of the binder and generate free radicals; exposing the binder to a dopant source gas, so that the dopant element in the dopant source gas combines with the free radicals on the surface of the binder to form active groups; the dopant element includes nitrogen and / or oxygen.

[0020] In one example of the present invention, the sulfide electrolyte and the binder are mixed to form a solid electrolyte membrane, comprising: mixing the sulfide electrolyte and the binder by wet coating or dry extrusion to form a solid electrolyte membrane; wherein the mass ratio of the sulfide electrolyte to the binder is (90-99.5):(0.5-10).

[0021] This invention provides a solid-state battery in which a solid electrolyte membrane comprises a sulfide electrolyte and a fluorinated binder. The fluorinated binder in the solid electrolyte membrane undergoes surface treatment to acquire more surface-active groups, which improves the binder's lithium-ion transport performance and further enhances its adhesion and tensile strength. In summary, a solid electrolyte membrane using the same amount of modified binder exhibits higher mechanical strength and ionic conductivity, effectively solving the problems of electrolyte membrane rupture and battery short circuits caused by electrode volume changes during charging and discharging in solid-state batteries, thereby improving the battery's lifespan and cycle performance. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic flowchart of a method for preparing a solid electrolyte in one embodiment of the present invention;

[0024] Figure 2 This is a flowchart illustrating step S2 in one embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In this invention, it should be noted that the terms "first" and "second" are used only for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0027] This invention provides a solid-state battery, which is a solid-state lithium-ion secondary battery. The solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte membrane. The solid electrolyte membrane is disposed between the positive and negative electrode to isolate the positive and negative electrode and acts as a lithium-ion conductor between the positive and negative electrode.

[0028] The solid electrolyte membrane comprises a sulfide electrolyte and a binder. The binder includes at least one of fluorine-containing monomers, dimers, and polymers. The binder is a surface-modified fluorine-containing binder in which the fluorine atoms (F) on the surface of the binder are modified and removed and replaced with other doped atoms, resulting in a molar ratio of carbon to fluorine on the surface of the binder of 0.41 to 1.

[0029] Specifically, some fluorine atoms on the binder surface are modified and removed, generating free radicals. These free radicals, when doped with other elements (such as O and N), form new active groups. These active groups effectively increase the surface free energy of the binder, improving its adhesion and tensile strength. Simultaneously, the low electronegativity of the doped atoms on the binder surface exhibits strong electron-withdrawing properties, allowing lithium ions in the sulfide electrolyte to migrate through ion-dipole interactions, thereby enhancing the lithium-ion conductivity of the solid electrolyte membrane. Therefore, solid electrolyte membranes using the same amount of modified binder exhibit higher mechanical strength and ionic conductivity.

[0030] The molar ratio of carbon (C) to fluorine (F) on the binder surface is 0.41 to 1. For example, the C / F molar ratio on the binder surface can be 0.41, 0.56, 0.59, 0.60, 0.65, 0.68, 0.7, 0.75, 0.8, 0.85, 0.88, 0.89, 0.9, 0.95, or 1. A C / F molar ratio within the above-mentioned suitable range allows the ionic conductivity and mechanical strength of the solid electrolyte membrane to reach their optimal levels. If the C / F molar ratio on the binder surface is too low, the improvement effect of the binder on lithium-ion conductivity and mechanical strength will be insignificant; if the C / F molar ratio on the binder surface is too high, the binder surface will be too rough, making it difficult to fibrousize, resulting in a decrease in the mechanical strength of the solid electrolyte membrane.

[0031] In some embodiments, the molar ratio of carbon to fluorine on the adhesive surface is 0.41 to 0.88. For example, the C / F molar ratio on the adhesive surface can be 0.41, 0.45, 0.47, 0.5, 0.53, 0.56, 0.59, 0.6, 0.63, 0.65, 0.68, 0.7, 0.75, 0.8, 0.83, 0.85, or 0.88. Optionally, the molar ratio of carbon to fluorine on the adhesive surface is 0.56 to 0.75. For example, the C / F molar ratio on the adhesive surface can be 0.56, 0.6, 0.63, 0.65, 0.67, 0.7, 0.73, or 0.75.

[0032] In some embodiments, the mass of the sulfide electrolyte is 90% to 99.5% of the mass of the solid electrolyte membrane, and correspondingly, the mass of the binder is 0.5% to 10% of the mass of the solid electrolyte membrane. For example, the mass content of the binder in the solid electrolyte membrane can be 0.5%, 0.8%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. Optionally, the mass content of the binder in the solid electrolyte membrane can be 0.5% or 1%. When the mass content of the binder in the solid electrolyte membrane is within the above range, the solid electrolyte membrane can achieve both good ionic conductivity and mechanical strength. If the mass content of the binder in the solid electrolyte membrane is too low, the solid electrolyte membrane will be close to powder, resulting in poor film formation or even difficulty in film formation; if the mass content of the binder in the solid electrolyte membrane is too high, the ionic conductivity of the solid electrolyte membrane will be too low, making lithium-ion conduction difficult.

[0033] In some embodiments, the thickness of the solid electrolyte membrane is 30–60 μm, for example, the thickness of the solid electrolyte membrane can be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm or 60 μm. Optionally, the thickness of the solid electrolyte membrane can be 40 μm.

[0034] In some embodiments, the particle size of the sulfide electrolyte is 1–10 μm, and the ionic conductivity of the sulfide electrolyte is greater than 1 mS / cm.

[0035] In some embodiments, the sulfide electrolyte is selected from Li3PS4 and Li7P3S. 11 Li 10 GeP2S 12 Li 10 SnP2S 12 Li6PS5Br, Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 At least one of the following. That is, the sulfide electrolyte can be any of the types listed above, such as Li3PS4, Li7P3S...11 Li 10 GeP2S 12 Li 10 SnP2S 12 Li6PS5Cl, Li6PS5Br or Li 5.5 PS 4.5 Cl 1.5 Optionally, the sulfide electrolyte may be Li. 5.5 PS 4.5 Cl 1.5 The sulfide electrolyte can also be a combination of any of the types listed above, such as Li3PS4 and Li7P3S. 11 The composition, or Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 The composition, or Li 10 GeP2S 12 and Li 5.5 PS 4.5 Cl 1.5 The composition, or Li 10 SnP2S 12 and Li 5.5 PS 4.5 Cl 1.5 The composition, or Li6PS5Br and Li 5.5 PS 4.5 Cl 1.5 The composition, or Li 10 SnP2S 12 Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 The composition. It should be noted that when the sulfide electrolyte is a composition, there are no restrictions on the proportions of the components within the composition; they can be mixed in any proportion.

[0036] In some embodiments, the adhesive comprises at least one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFE), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and ethylene-tetrafluoroethylene copolymer (ETFE) with a surface C / F molar ratio of 0.41 to 1. That is, the adhesive can be any one of the types listed above, such as PTFE, PVDF, ETFE, PVDF-HFP, or PVDF-HFE. Optionally, PTFE is selected as the adhesive. The adhesive can also be a combination of any number of the types listed above, such as a combination of PTFE and PVDF, or a combination of PTFE and PVDF-HFP, or a combination of PTFE and PVDF-HFE, or a combination of ETFE and PVDF, or a combination of PTFE, PVDF, and PVDF-HFP, or a combination of PTFE, PVDF, and PVDF-HFE. It should be noted that when the adhesive is a composition, the proportions between the components in the composition are not limited, and they can be mixed in any proportion.

[0037] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer coated on at least one side of the positive current collector. The positive active material layer includes a positive electrode material, a positive electrode binder, a positive electrode conductive agent, and a solid electrolyte. The solid electrolyte is a sulfide electrolyte used in the solid electrolyte membrane. The mass ratio of the positive active material, solid electrolyte, positive electrode binder, and positive electrode conductive agent can be (50–75):(20–50):(0–3):(1–3).

[0038] The positive electrode current collector can be made of foil with good conductivity and mechanical strength, such as aluminum, nickel, titanium, gold, silver, chromium, molybdenum, copper, stainless steel or carbon. In addition to foil, the positive electrode current collector can also be made of any one or more of the following forms: film, mesh, porous, foam or non-woven fabric.

[0039] The cathode material can be a layered cathode material, an olivine cathode material, or a spinel cathode material. The layered cathode material can be lithium cobalt oxide (LCO), lithium nickel cobalt manganese oxide (NCM), or lithium nickel cobalt aluminum oxide (NCA), etc.; the olivine cathode material can be lithium iron phosphate (LFP), lithium manganese iron phosphate (LFMP), etc.; and the spinel cathode material can be lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium-rich manganese oxide (LRMO), etc.

[0040] The positive electrode binder is selected from one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), and styrene-butadiene rubber (SBR).

[0041] The positive electrode conductive agent is selected from one of carbon black, Ketjen black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, porous carbon, etc., or a combination of two or more in any proportion.

[0042] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active material layer coated on at least one side of the negative current collector. The negative active material layer includes a negative electrode material, a solid electrolyte, a negative electrode binder, and a negative electrode conductive agent. The solid electrolyte is a sulfide electrolyte used in the solid electrolyte membrane. The mass ratio of the negative active material, solid electrolyte, negative electrode binder, and negative electrode conductive agent can be (50–75):(20–50):(0–3):(1–3).

[0043] The negative electrode current collector can be made of foil with good conductivity and mechanical strength, such as aluminum, nickel, titanium, gold, silver, chromium, molybdenum, copper, stainless steel or carbon. In addition to foil, the negative electrode current collector can also be made of any one or more of the following forms: film, mesh, porous, foam or non-woven fabric.

[0044] The negative electrode active material is selected from one or more of the following: tin, artificial graphite (single crystal graphite, polycrystalline graphite, pyrolytic graphite, graphite fiber, etc.), natural graphite (bulk graphite, flake graphite, earthy graphite, etc.), soft carbon, hard carbon, pure silicon (crystalline silicon, amorphous silicon or organosilicon), silicon oxide, silicon carbide, and nano metal oxides (Fe2O3, CuO, SnO2, Mn3O4 nanoparticles).

[0045] The negative electrode conductive agent is selected from one or more of carbon black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers, or a mixture of two or more in any proportion.

[0046] The negative electrode binder is selected from any one of fluoroethylene-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), polymethyl methacrylate (PMMA), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), and styrene-butadiene rubber (SBR), or a combination of several in any proportion.

[0047] In other embodiments, the negative electrode can be a lithium metal sheet, an indium metal sheet, or a lithium-containing alloy sheet (such as a lithium-tin-indium alloy sheet, a lithium-silicon alloy sheet, a lithium-tin alloy sheet, or a lithium-aluminum alloy sheet). For example, in one example, the negative electrode is selected from a lithium metal sheet.

[0048] In another aspect, the present invention also provides a method for preparing a solid-state battery, the method comprising: providing a positive electrode, a solid electrolyte membrane, and a negative electrode; assembling the positive electrode, the solid electrolyte membrane, and the negative electrode into a battery cell, and encapsulating the battery cell to obtain a solid-state battery.

[0049] like Figure 1 As shown, the preparation method of the solid electrolyte membrane in the above-mentioned solid-state battery includes the following steps:

[0050] S1. Provide a sulfide electrolyte and a binder; the binder includes at least one of a fluorinated monomer, dimer, and polymer;

[0051] S2. Surface modification of the adhesive is performed so that the molar ratio of carbon to fluorine on the surface of the adhesive is 0.41 to 1.

[0052] S3. The sulfide electrolyte is mixed with the binder to form a solid electrolyte membrane.

[0053] In some embodiments, the sulfide electrolyte provided in step S1 is selected from Li3PS4 and Li7P3S. 11 Li 10 GeP2S 12 Li 10 SnP2S 12 Li6PS5Br, Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 One or more of the following; optionally, the sulfide electrolyte is selected from Li 5.5 PS 4.5 Cl 1.5 The sulfide electrolyte selected in step S11 has a particle size of 1–10 μm and an ionic conductivity greater than 1 mS / cm.

[0054] In some embodiments, the adhesive provided in step S1 is selected from at least one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFE), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and ethylene-tetrafluoroethylene copolymer (ETFE).

[0055] like Figure 2 As shown, in some embodiments, step S2 includes the following steps:

[0056] S21. Plasma etching is performed on the surface of the adhesive to remove fluorine atoms and generate free radicals.

[0057] S22. The binder is exposed to a doping source gas, so that the doping element in the doping source gas combines with the free radical on the surface of the binder to form active groups; the doping element includes nitrogen and / or oxygen.

[0058] Specifically, in step S21, the binder is placed into the cavity of the plasma etching equipment, and the binder in the cavity is subjected to plasma etching to remove fluorine atoms on the surface of the binder and generate free radicals, which triggers cross-linking reaction or the formation of unsaturated bonds on the surface; and by modulating parameters such as the atmosphere, plasma power, etching time, and gas flow rate of the plasma etching equipment, the C / F molar ratio on the surface of the binder is controlled to any value between 0.41 and 1.

[0059] In step S21, the gas used for plasma etching is one or a mixture of several of the following: argon, helium, nitrogen, oxygen, hydrogen, and ammonia. Optionally, oxygen is used for plasma etching. The plasma power applied for plasma etching is 10–200 W; the etching time for plasma etching is 10–1800 s; and the gas flow rate for plasma etching is 0–300 ml / min.

[0060] The C / F molar ratio on the binder surface can be controlled by adjusting parameters such as plasma application power, etching time, and gas flow rate during plasma etching. When the plasma application power, etching time, and gas flow rate are low, the C / F molar ratio on the binder surface does not increase significantly, the adhesion of the binder is not significantly improved, and the mechanical strength of the prepared solid electrolyte membrane is only slightly enhanced. When the plasma application power, etching time, and gas flow rate are high, the C / F molar ratio on the binder surface is higher than 1. At this point, the binder surface is rough, which is not conducive to subsequent fibrosis, and the mechanical strength of the prepared solid electrolyte membrane begins to decrease. Therefore, in step S21, by adjusting parameters such as plasma application power, etching time, and gas flow rate during plasma etching, the C / F molar ratio on the binder surface is limited to 0.41–1 to ensure improved mechanical strength and ionic conductivity of the prepared solid electrolyte membrane.

[0061] Specifically, in step S22, the adhesive powder after plasma etching is placed in the air and left to stand for 1 to 10 hours. After the adhesive is exposed to the air, the unsaturated bonds on the surface react with dopant source gases such as oxygen and nitrogen, thereby introducing O and / or N elements and generating new active groups, increasing the surface free energy of the fluorine-containing adhesive, and thus improving the adhesive's adhesion, tensile strength and ability to migrate lithium ions.

[0062] In step S3, a solid electrolyte membrane is prepared by mixing the sulfide electrolyte and the binder using wet coating or dry extrusion; wherein the mass ratio of the sulfide electrolyte to the binder is (90-99.5):(0.5-10).

[0063] In one example, step S3 prepares a solid electrolyte membrane using a wet coating method. Step S3 includes the following steps: mixing a sulfide electrolyte and a modified binder in a low-polarity solvent at a mass ratio of (90-99.5):(0.5-10); adjusting the solid content of the slurry and vacuum-treating the slurry using a vacuum degassing machine to obtain a uniform mixed slurry; coating the mixed slurry onto the substrate surface using a sprayer or coating machine; drying to remove the solvent from the coating on the substrate to obtain a solid electrolyte coating; and peeling the solid electrolyte coating off the substrate to obtain the solid electrolyte membrane. The low-polarity solvent is a solvent with a polarity index lower than 2.5. For example, the first solvent is selected from at least one of toluene, xylene, n-pentane, hexane, and cyclohexane; optionally, xylene is selected as the low-polarity solvent. The substrate is selected from one of aluminum foil, copper foil, PET board, release paperboard, PTFE board, and glass plate.

[0064] In another example, step S3 uses a dry extrusion method to prepare a solid electrolyte membrane. Step S3 includes the following steps: mixing a sulfide electrolyte and a modified binder at a mass ratio of (90–99.5):(0.5–10) to obtain a mixed powder; and repeatedly rolling the mixed powder at a preset temperature for a preset rolling time to obtain a solid electrolyte membrane. The preset temperature is 60–100°C, and the preset rolling time is 30–120 min.

[0065] It should be noted that the positive electrode, negative electrode, and solid-state battery assembly process in solid-state batteries can be prepared using conventional methods in this field.

[0066] In some embodiments, the positive electrode preparation process is as follows: Positive electrode material, solid electrolyte, positive electrode binder, and positive electrode conductive agent are mixed in a mass ratio of (50–75):(20–50):(0–3):(1–3). N-methylpyrrolidone (NMP) solvent is added to adjust the slurry solid content to 55%. The mixture is then thoroughly stirred under vacuum to obtain a positive electrode slurry. This positive electrode slurry is uniformly coated onto a positive electrode current collector. The current collector is then air-dried at room temperature and transferred to an oven for drying. Finally, it is cold-pressed and slit to obtain the positive electrode sheet.

[0067] The positive electrode current collector can be a foil material with good conductivity and mechanical strength, such as aluminum, nickel, titanium, gold, silver, chromium, molybdenum, copper, stainless steel, or carbon. Besides foil materials, the positive electrode current collector can also be any one or more combinations of various forms such as film, mesh, porous, foam, or nonwoven fabric. The solid electrolyte is the same type of sulfide electrolyte used in the solid electrolyte membrane. The positive electrode material is selected from one or more combinations of lithium cobalt oxide (LCO), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium iron phosphate (LFP), lithium manganese iron phosphate (LFMP), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), and lithium-rich manganese-based oxide (LRMO). The positive electrode binder is selected from one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), and styrene-butadiene rubber (SBR). The positive electrode conductive agent is selected from one or more combinations of carbon black, Ketjen black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, and porous carbon, or in any proportion.

[0068] In some embodiments, the negative electrode preparation process is as follows: the negative electrode material, solid electrolyte, negative electrode binder, and negative electrode conductive agent are mixed in a mass ratio of (50-75):(20-50):(0-3):(1-3), deionized water is added, the solid content of the slurry is adjusted to 55%, and then the mixture is thoroughly stirred and mixed under the action of a vacuum mixer to obtain a negative electrode slurry; the negative electrode slurry is uniformly coated on the negative electrode current collector; after drying at room temperature, it is transferred to an oven for drying, and then the negative electrode is obtained through cold pressing, slitting and other processes.

[0069] The negative electrode current collector can be a foil material with good conductivity and mechanical strength, such as aluminum, nickel, titanium, gold, silver, chromium, molybdenum, copper, stainless steel, or carbon. Besides foil materials, the negative electrode current collector can also be any one or more of the following forms: film, mesh, porous, foam, or non-woven fabric. The solid electrolyte is the same type of sulfide electrolyte used in the solid electrolyte membrane. The negative electrode active material is selected from one or more of the following: tin, artificial graphite (single-crystal graphite, polycrystalline graphite, pyrolytic graphite, graphite fiber, etc.), natural graphite (bulk graphite, flake graphite, amorphous graphite, etc.), soft carbon, hard carbon, pure silicon (crystalline silicon, amorphous silicon, or organosilicon), silicon oxides, silicon carbide compounds, and nano-metal oxides (Fe2O3, CuO, SnO2, Mn3O4 nanoparticles). The negative electrode conductive agent is selected from one or a combination of two or more of the following: carbon black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers, or in any proportion. The negative electrode binder is selected from any one of fluoroethylene-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), polymethyl methacrylate (PMMA), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), and styrene-butadiene rubber (SBR), or a combination of several in any proportion.

[0070] In other embodiments, lithium metal sheets, indium metal sheets, and lithium-containing alloy sheets (such as lithium-tin-indium alloy sheets, lithium-silicon alloy sheets, lithium-tin alloy sheets, and lithium-aluminum alloy sheets) are used as negative electrode sheets.

[0071] The following is an example of how to assemble a secondary battery: A positive electrode is integrated onto one side of a solid electrolyte membrane. For example, the solid electrolyte membrane is placed on the positive active material layer of the positive electrode, and the solid electrolyte membrane and the positive electrode are pressed together under a pressure of 200 MPa. Then, a negative electrode is integrated onto the other side of the solid electrolyte membrane. For example, a negative electrode is placed on the other side of the solid electrolyte membrane, so that the negative active material layer of the negative electrode is in contact with the solid electrolyte membrane. The negative electrode is then pressed together with the solid electrolyte membrane and the positive electrode under a pressure of 200 MPa. After sealing and encapsulating the pressed cell under a vacuum or inert atmosphere, a solid-state lithium-ion battery is obtained.

[0072] The technical solution of the present invention will be described in detail below through several specific embodiments and comparative examples. Unless otherwise stated, the raw materials and reagents used in the following embodiments are commercially available products or can be prepared by conventional methods in the art.

[0073] Example 1

[0074] This embodiment provides a solid-state battery in which a solid electrolyte membrane comprises 99% by mass of a sulfide electrolyte and 1% by mass of a modified binder. The sulfide electrolyte is Li. 5.5 PS4.5 Cl 1.5 The binder is PTFE with a surface C / F molar ratio of 0.41.

[0075] The preparation process of this solid electrolyte membrane is as follows:

[0076] S1, provides sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 and PTFE binder;

[0077] S2. Place the binder powder into the cavity of the plasma etching equipment and perform plasma etching on the binder in the cavity. Set the plasma application power to 50W, process under argon atmosphere for 50s, and introduce gas into the cavity at a flow rate of 150ml / min. Place the etched binder powder in air for 1 hour to obtain a surface-modified binder.

[0078] S3. Grind and mix the sulfide electrolyte and modified binder at a mass ratio of 99:1 for 5 minutes, and place them at 80°C for rolling. Gradually reduce the gap between the rollers until it reaches 40μm. Repeat the rolling process at this gap for 60 minutes to obtain a solid electrolyte membrane with a thickness of 40μm.

[0079] The fabrication process of this solid-state battery is as follows:

[0080] (1) Preparation of the positive electrode sheet: The positive electrode material, solid electrolyte, positive electrode binder, and positive electrode conductive agent were ground and mixed in a mass ratio of 75:23:1:1 for 5 minutes to obtain a positive electrode slurry. The positive electrode slurry was placed at 80°C for rolling, and the gap between the rollers was gradually reduced to 40 μm. After repeated rolling under this gap for 60 minutes, a positive electrode active material layer with a thickness of 40 μm was obtained. This positive electrode active material layer was transferred onto the positive electrode current collector aluminum foil to obtain the positive electrode sheet. The positive electrode material is LiNbO3-coated LiNi. 0.9 Co 0.05 Mn 0.05 O2; the solid electrolyte is a sulfide electrolyte of the same type as that used in solid electrolyte membranes; the positive electrode binder is the same modified binder used in solid electrolyte membranes; the positive electrode conductive agent is conductive carbon black.

[0081] (2) Preparation of negative electrode sheet: The negative electrode material, solid electrolyte, negative electrode binder, and negative electrode conductive agent are mixed in a mass ratio of 75:23:1:1. Xylene is added to adjust the solid content of the slurry to 55%. The mixture is then thoroughly stirred under vacuum to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated onto the negative electrode current collector copper foil. After drying at room temperature, it is transferred to an oven for drying. Then, the negative electrode sheet is obtained through cold pressing, slitting, and other processes. The negative electrode material is silicon; the solid electrolyte is a sulfide electrolyte of the same type as that used in solid electrolyte membranes; the negative electrode binder is the same modified binder used in solid electrolyte membranes; and the negative electrode conductive agent is conductive carbon black.

[0082] (3) Solid-state battery assembly:

[0083] The solid electrolyte membrane and the positive electrode are stacked together, and a pressure of 200 MPa is applied to press the positive electrode and the solid electrolyte membrane into one piece. Then, the negative electrode is stacked on the side of the solid electrolyte membrane opposite to the positive electrode, and a pressure of 200 MPa is applied to press the positive electrode, the solid electrolyte membrane and the negative electrode together to obtain the cell. After the cell is sealed in a vacuum or inert atmosphere, it is formed, capacity tested and aged to obtain a solid-state battery.

[0084] Example 2

[0085] This embodiment provides a solid-state battery with the same system as that in Embodiment 1. The difference between this embodiment and Embodiment 1 is that in step S2 of preparing the solid electrolyte membrane, the time for introducing gas into the cavity during the plasma etching process is set to 300s, so that the C / F molar ratio of the binder surface is 0.56.

[0086] Example 3

[0087] This embodiment provides a solid-state battery with the same system as that in Embodiment 2. The difference between this embodiment and Embodiment 2 is that in step S2 of preparing the solid electrolyte membrane, the applied power of plasma etching is set to 100W, so that the C / F molar ratio of the binder surface is 0.60.

[0088] Example 4

[0089] This embodiment provides a solid-state battery with the same system as that in Embodiment 2. The difference between this embodiment and Embodiment 2 is that in step S2 of preparing the solid electrolyte membrane, the applied power of plasma etching is set to 200W, so that the C / F molar ratio of the binder surface is 0.68.

[0090] Example 5

[0091] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that in step S2 of preparing the solid electrolyte membrane, the etching time of plasma etching is set to 600s, so that the C / F molar ratio of the binder surface is 0.65.

[0092] Example 6

[0093] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that in step S2 of preparing the solid electrolyte membrane, the etching time of plasma etching is set to 900s, so that the C / F molar ratio of the binder surface is 0.75.

[0094] Example 7

[0095] This embodiment provides a solid-state battery with the same system as that in Embodiment 3. The difference between this embodiment and Embodiment 3 is that in step S2 of preparing the solid electrolyte membrane, the etching time of plasma etching is set to 1800s, so that the C / F molar ratio of the binder surface is 0.89.

[0096] Example 8

[0097] This embodiment provides a solid-state battery with the same system as that in Embodiment 6. The difference between this embodiment and Embodiment 6 is that in step S2 of preparing the solid electrolyte membrane, the gas flow rate in the cavity during the plasma etching process is set to 50 ml / min, so that the C / F molar ratio of the binder surface is 0.59.

[0098] Example 9

[0099] This embodiment provides a solid-state battery with the same system as that in Embodiment 6. The difference between this embodiment and Embodiment 6 is that in step S2 of preparing the solid electrolyte membrane, the gas flow rate in the cavity during the plasma etching process is set to 300 ml / min, so that the C / F molar ratio of the binder surface is 0.88.

[0100] Example 10

[0101] This embodiment provides a solid-state battery with the same system as that in Embodiment 6. The difference between this embodiment and Embodiment 6 is that in step S3 of preparing the solid electrolyte membrane, the mass ratio of sulfide electrolyte and modified binder is adjusted to 99.5:0.5.

[0102] Example 11

[0103] This embodiment provides a solid-state battery with the same system as that in Embodiment 6. The difference between this embodiment and Embodiment 6 is that in step S3 of preparing the solid electrolyte membrane, the mass ratio of sulfide electrolyte and modified binder is adjusted to 95:5.

[0104] Example 12

[0105] This embodiment provides a solid-state battery with the same system as that in Embodiment 6. The difference between this embodiment and Embodiment 6 is that in step S3 of preparing the solid electrolyte membrane, the mass ratio of sulfide electrolyte and modified binder is adjusted to 90:10.

[0106] Example 13

[0107] This embodiment provides a solid-state battery with the same system as Embodiment 6. The difference between this embodiment and Embodiment 6 is that:

[0108] In the preparation of the solid electrolyte membrane, PVDF-HFP is used as the binder in the solid electrolyte membrane; the sulfide electrolyte and the modified binder are mixed into xylene at a mass ratio of 98:2, and the solid content of the slurry is adjusted to obtain a uniform mixed slurry; the mixed slurry is coated onto release paper using a sprayer or coating machine, and after vacuum drying at 60°C, the solid electrolyte coating is peeled off from the substrate to obtain the solid electrolyte membrane.

[0109] In the preparation of the positive electrode sheet, the positive electrode material, solid electrolyte, negative electrode binder, and negative electrode conductive agent are mixed in a mass ratio of 75:23:1:1. Xylene is added to adjust the solid content of the slurry to 55%. Then, the mixture is thoroughly stirred under the action of a vacuum mixer to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil. After being dried at room temperature, it is transferred to an oven for drying. Then, the positive electrode sheet is obtained through processes such as cold pressing and slitting.

[0110] Example 14

[0111] This embodiment provides a solid-state battery with the same system as that in Embodiment 6. The difference between this embodiment and Embodiment 6 is that the sulfide electrolyte in the positive electrode, negative electrode and solid electrolyte membrane is adjusted to Li6PS5Cl.

[0112] Comparative Example 1

[0113] This comparative example provides a solid-state battery with the same system as Example 6. The difference between this example and Example 6 is that the binder in the solid electrolyte membrane uses unmodified PTFE.

[0114] Comparative Example 2

[0115] This comparative example provides a solid-state battery with the same system as Example 6. The difference between this example and Example 6 is that in step S2 of preparing the solid electrolyte membrane, the applied power of plasma etching is set to 250W, the etching time is 1500s, and the gas flow rate in the cavity is 300ml / min, so that the C / F molar ratio of the binder surface is 1.17.

[0116] Comparative Example 3

[0117] This comparative example provides a solid-state battery with the same system as Example 6. The difference between this example and Example 6 is that in step S3 of preparing the solid electrolyte membrane, the mass ratio of sulfide electrolyte and modified binder is adjusted to 99.9:0.1.

[0118] Comparative Example 4

[0119] This comparative example provides a solid-state battery with the same system as Example 6. The difference between this example and Example 6 is that in step S3 of preparing the solid electrolyte membrane, the mass ratio of sulfide electrolyte and modified binder is adjusted to 70:30.

[0120] To further verify the efficacy of the present invention, the mechanical strength and ionic conductivity of the solid electrolyte membranes prepared in Examples 1 to 14 and Comparative Examples 1 to 4 were first tested, and the test results are shown in Table 1. Then, the cycle life of the solid batteries prepared in Examples 1 to 14 and Comparative Examples 1 to 4 was tested, and the test results are shown in Table 2. The test process is as follows:

[0121] 1. C / F molar ratio test of adhesive surface: Take a small amount of adhesive powder from the examples and comparative examples and stick it onto the copper tape. Use XPS to test the C and F element content on the adhesive surface.

[0122] 2. Stress-strain curve test of solid electrolyte membrane: The solid electrolyte membranes obtained in the examples and comparative examples are cut into regular rectangles, the samples are fixed on a universal testing machine, and the solid electrolyte membrane is stretched at a speed of 1 cm / min until it breaks, and the stress and strain values ​​of the solid electrolyte membrane at the time of fracture are obtained.

[0123] 3. Lithium-ion conductivity test of solid electrolyte membrane: The solid electrolyte membranes obtained in the examples and comparative examples were cut into circular pieces with a diameter of 10 mm. Using stainless steel as the blocking electrode, a mold battery was assembled under a certain pressure. The solid electrolyte membrane was subjected to AC impedance testing using an electrochemical workstation to obtain the ionic conductivity of the solid electrolyte membrane.

[0124] 4. Cycle life test of solid-state battery: At room temperature of 25℃, within the test voltage range of 2.5V (discharge cut-off voltage) to 4.2V (charge cut-off voltage), the solid-state battery is subjected to the first cycle of charge-discharge test at a charge-discharge current rate of 0.1C / 0.1C; then, the solid-state battery is subjected to 3 cycles of charge-discharge at current rates of 0.2C / 0.2C, 0.5C / 0.5C, 1C / 1C, and 2C / 2C; finally, the solid-state battery is charged and discharged at a current rate of 0.5C / 0.5C. When the discharge capacity of the solid-state battery reaches 80% of the discharge capacity of the first cycle at the 0.5C rate, the test is stopped, and the number of cycles at room temperature is recorded.

[0125] Table 1: Stress-strain and ionic conductivity test results of solid electrolyte membranes provided in Examples 1 to 14 and Comparative Examples 1 to 4

[0126]

[0127] Table 2: Test results of cycle life of solid-state batteries provided in Examples 1 to 14 and Comparative Examples 1 to 4

[0128]

[0129] Comparing the test results of Examples 1 to 9 and Comparative Example 1, it can be seen that after plasma treatment, the C / F molar ratio of the binder surface in the solid electrolyte membrane increases. The O and N elements introduced after plasma etching of the binder surface form new active groups, which increase the surface free energy of the binder and improve the adhesion of the binder. Under the condition of ensuring that the ionic conductivity does not decrease significantly, the mechanical strength of the solid electrolyte membrane is improved, thereby further improving the cycle life of the solid battery.

[0130] Comparing the test results of Examples 1 to 9 and Comparative Examples 1 to 2, it can be seen that limiting the C / F molar ratio on the surface of the modified binder to a suitable range of 0.41 to 1, especially when the C / F molar ratio is 0.41 to 0.88, can balance the improvement of ionic conductivity and mechanical strength of the solid electrolyte membrane, thereby improving the cycle performance of the solid battery. If the C / F molar ratio on the surface of the binder is too low (<0.41), the surface properties of the binder do not change much, only a small number of F atoms detach from the surface of the binder and only a small number of new active groups are formed, and the improvement effect on lithium-ion conductivity and mechanical strength of the prepared solid electrolyte membrane is not obvious. If the C / F molar ratio on the surface of the binder is too high (>1), the surface of the binder is too rough and difficult to fibrousize, resulting in a decrease in the mechanical strength of the prepared solid electrolyte membrane.

[0131] Comparing the test results of Examples 6, 11 to 13 and Comparative Examples 3 and 4, it can be seen that limiting the mass ratio of sulfide electrolyte to binder in the solid electrolyte membrane to (90-99.5):(0.5-10) allows the solid electrolyte membrane to achieve both good ionic conductivity and mechanical strength, thereby optimizing the cycle life improvement of the solid-state battery. However, when the mass content of binder in the solid electrolyte membrane is too low (<0.5%), the ionic conductivity of the solid electrolyte membrane is close to that of sulfide electrolyte powder, but the film-forming properties of the solid electrolyte membrane are poor or difficult to form, making it impossible for the assembled battery to achieve charge-discharge cycles. As the binder content increases, excessive binder coats the surface of sulfide electrolyte particles in the solid electrolyte membrane, hindering ion transport between sulfide electrolyte particles through mutual contact, thus reducing the ionic conductivity of the solid electrolyte membrane. In particular, when the binder content in the solid electrolyte membrane is too high (>10%), the binder coats the surface of the sulfide electrolyte, reducing the ionic conductivity of the solid electrolyte membrane to below 0.1 mS / cm, making lithium-ion conduction between the positive and negative electrodes impossible.

[0132] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A solid-state battery, characterized in that, The invention includes a solid electrolyte membrane comprising a sulfide electrolyte and a binder, wherein the binder comprises at least one of a fluorine-containing monomer, dimer, and polymer, and the binder is modified by plasma etching, wherein the molar ratio of carbon to fluorine on the surface of the binder is 0.41 to 1.

2. The solid-state battery according to claim 1, characterized in that, The molar ratio of carbon to fluorine on the surface of the adhesive is 0.41 to 0.

88.

3. The solid-state battery according to claim 1, characterized in that, The thickness of the solid electrolyte membrane is 30–60 μm.

4. The solid-state battery according to claim 1, characterized in that, The adhesive includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, and ethylene-tetrafluoroethylene copolymer.

5. The solid-state battery according to claim 1, characterized in that, The mass of the sulfide electrolyte is 90% to 99.5% of the mass of the solid electrolyte membrane; the mass of the binder is 0.5% to 10% of the mass of the solid electrolyte membrane.

6. The solid-state battery according to claim 1, characterized in that, The sulfide electrolyte has an ionic conductivity greater than 1 mS / cm; and / or the sulfide electrolyte has a particle size of 1–10 μm.

7. The solid-state battery according to claim 1 or 6, characterized in that, The sulfide electrolyte includes Li3PS4 and Li7P3S. 11 Li 10 GeP2S 12 Li 10 SnP2S 12 Li6PS5Br, Li6PS5Cl and Li 5.5 PS 4.5 Cl 1.5 At least one of them.

8. A method for preparing a solid-state battery, characterized in that, include: We provide positive electrode plates, solid electrolyte membranes, and negative electrode plates; The positive electrode, the solid electrolyte membrane, and the negative electrode are assembled into a cell, and the cell is then encapsulated to obtain a solid-state battery. The method for preparing the solid electrolyte membrane includes: A sulfide electrolyte and a binder are provided, the binder comprising at least one of a fluorinated monomer, dimer, and polymer; The adhesive is surface modified by plasma etching so that the molar ratio of carbon to fluorine on the adhesive surface is 0.41 to 1. The sulfide electrolyte is mixed with the binder to form a solid electrolyte membrane.

9. The preparation method according to claim 8, characterized in that, Surface modification of the adhesive includes: Plasma etching is performed on the surface of the adhesive to remove fluorine atoms and generate free radicals. The binder is exposed to a doping source gas, allowing the dopant elements in the doping source gas to combine with free radicals on the surface of the binder to form active groups; the doping elements include nitrogen and / or oxygen.

10. The preparation method according to claim 8, characterized in that, The sulfide electrolyte is mixed with the binder to form a solid electrolyte membrane, comprising: A solid electrolyte membrane is prepared by mixing the sulfide electrolyte with the binder using wet coating or dry extrusion; wherein the mass ratio of the sulfide electrolyte to the binder is (90-99.5):(0.5-10).

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