Batteries and electrical devices

Abstract

This application provides a battery and an electrical device. By having the fluorinated SEI film on the negative electrode side and the fluorinated barrier layer on the solid electrolyte side co-evolve and couple with each other during the battery formation process, a composite interface phase with compositional and functional gradients can be constructed in situ in the interface region. This can achieve spatial decoupling and functional separation of lithium-ion transport pathways and electron tunneling channels at the nanoscale, thereby fundamentally suppressing the reduction reaction of high-valence titanium from both thermodynamic and kinetic perspectives and alleviating the "blackening" side reaction.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more particularly to a battery and an electrical device. Background Technology

[0002] Currently, silicon-carbon (Si / C) anodes have become a key material for next-generation batteries due to their high capacity. However, when directly combined with titanium-containing solid electrolytes (such as LATP), there are serious interface compatibility issues, which can easily generate side reaction interfaces, leading to reduced initial efficiency and capacity decay.

[0003] Related technologies attempt to alleviate the above problems by modifying the surface of titanium-containing solid electrolytes or optimizing electrolyte formulations, but the effects are limited.

[0004] Therefore, there is an urgent need to develop new battery modules that can stably match Si / C anodes with titanium-containing solid electrolytes. Summary of the Invention

[0005] This application provides a battery and an electrical device that aims to improve the interface compatibility between existing Si / C anodes and titanium-containing solid electrolytes.

[0006] To solve the above problems, this application provides the following technical solution: This application proposes a battery, including a negative electrode, a positive electrode, and a composite separator, wherein the composite separator is disposed between the negative electrode and the positive electrode; The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. The negative active material layer includes a negative active material and a first inorganic fluorine-containing lithium salt. The negative active material includes silicon-carbon material. The composite separator includes a base membrane, a first coating and a second coating. The first coating is disposed on the surface of the base membrane, and the second coating is disposed on the surface of the first coating at least facing the negative electrode. The first coating includes a titanium-containing solid electrolyte, and the second coating includes a second inorganic fluorine-containing lithium salt.

[0007] In the battery provided in this application embodiment, a first inorganic fluorinated lithium salt is introduced into the negative electrode active material layer comprising silicon-carbon material, and a second coating comprising a second inorganic fluorinated lithium salt is introduced onto the surface of a first coating comprising a titanium-containing solid electrolyte. The first inorganic fluorinated lithium salt dispersed in the negative electrode active material layer preferentially participates in electrochemical reactions during the first charge-discharge process of the battery, guiding the formation of a solid electrolyte interface (SEI) film dominated by lithium fluoride (LiF) with high ionic conductivity and high mechanical stability. This not only optimizes the lithium-ion transport kinetics at the interface but also serves as a supplementary lithium source, compensating for the unpredictable lithium ion transport caused by film formation. Reverse lithium loss; while the second coating, including the second inorganic fluorinated lithium salt, acts as a fluorination barrier layer, which can retain ion transport channels and selectively block electron migration paths; the fluorinated SEI film on the negative electrode side and the fluorinated barrier layer on the solid electrolyte side co-evolve and couple with each other during battery formation, which can construct a composite interface phase with compositional and functional gradients in situ in the interface region, and realize the spatial decoupling and functional separation of lithium ion transport paths and electron tunneling channels at the nanoscale, thereby fundamentally suppressing the reduction reaction of high-valence titanium from both thermodynamic and kinetic perspectives and alleviating the "blackening" side reaction.

[0008] Furthermore, in the battery, the first inorganic fluorinated lithium salt includes at least one of lithium fluoride and lithium hexafluorosilicate; and / or, The second inorganic fluorinated lithium salt includes at least one of lithium fluoride and lithium hexafluorosilicate.

[0009] Furthermore, in the battery, the mass content of the first inorganic fluorinated lithium salt in the negative electrode active material layer is 1%~3%; and / or, The second inorganic fluorinated lithium salt has a mass content of 70% to 95% in the second coating.

[0010] Furthermore, in the battery, the thickness of the second coating is 3μm~5μm.

[0011] Furthermore, in the battery, the second coating has a discontinuous structure; and / or, The porosity of the second coating is 20% to 60%.

[0012] Furthermore, in the battery, the second coating further includes an adhesive, the adhesive comprising at least one of a fluoropolymer and a fluorinated modified elastomer; The fluoropolymer includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyvinylidene fluoride-hexafluoropropylene copolymer.

[0013] Furthermore, in the battery, the surface of the silicon-carbon material has a fluorocarbon layer.

[0014] Furthermore, in the battery, the silicon content in the silicon-carbon is ≥50% by mass, and the particle size is 4μm~10μm.

[0015] Furthermore, the battery further includes an electrolyte, which comprises lithium salt and organic solvent.

[0016] This application also proposes an electrical device, including a battery as described above, wherein the battery serves as the power supply for the electrical device. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the battery structure provided in an embodiment of this application. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0019] Currently, silicon (Si) is considered the most promising next-generation anode material due to its extremely high theoretical specific capacity. However, its dramatic volume expansion (>300%) during charge and discharge processes easily leads to the pulverization of active materials and repeated cracking and regeneration of the solid electrolyte interface (SEI), resulting in severe capacity decay. Silicon-carbon (Si / C) composite materials significantly improve the electrochemical performance of silicon-based anodes by introducing a carbon matrix to buffer volume stress and enhance electronic conductivity.

[0020] Meanwhile, the use of solid-state electrolytes to construct high-safety battery systems has become a clear trend. Among them, titanium-containing solid-state electrolytes based on the NASICON structure (such as lithium aluminum titanium phosphate, LATP) have high room-temperature ionic conductivity (approximately 10). -3 S cm -1 It has attracted much attention due to its excellent air stability and simple preparation process, and is an ideal electrolyte material for hybrid solid-liquid batteries.

[0021] The inventors discovered that directly combining a high-capacity Si / C anode with a LATP solid electrolyte presents a severe interfacial compatibility problem. The root cause lies in the significant electrochemical potential mismatch between the two: during battery charging, the Si / C anode potential can drop below 0.1 V, while the Ti in LATP... 4+ The reduction potential is typically above 2.0 V. Thermodynamically, the Si / C anode will spontaneously reduce the Ti layer on the LATP surface. 4+This process generates a mixed conductive interface phase containing low-valent titanium (macroscopically manifested as "black matter"), leading to irreversible consumption of active lithium, a sharp increase in interface impedance, and a significant decrease in initial coulombic efficiency, becoming a key technological bottleneck restricting the development of high-energy-density batteries.

[0022] To address the aforementioned interface issues, related technologies, including surface modification of titanium-containing solid electrolytes or optimization of electrolyte formulations, are insufficient to maintain efficient lithium-ion transport while effectively blocking electron migration. They often fall into the dilemma of "sacrificing ionic conductivity to suppress side reactions, and exacerbating side reactions to ensure ion transport," failing to fundamentally eliminate the interface "blackening" phenomenon and the resulting performance degradation.

[0023] Therefore, there is an urgent need to develop a new type of battery module and its construction method that can be stably matched with titanium-containing solid electrolytes, has high initial coulombic efficiency and long cycle life, in order to break through the current technical bottlenecks and promote the practical application of high-energy-density and high-safety batteries.

[0024] To address the aforementioned problems, this application provides a battery 10, such as... Figure 1 As shown, the device includes a negative electrode 11, a positive electrode 12, and a composite separator 13, with the composite separator 13 disposed between the negative electrode 11 and the positive electrode 12. The negative electrode 11 includes a negative current collector 111 and a negative active material layer 112 disposed on at least one surface of the negative current collector 111. The negative active material layer includes a negative active material and a first inorganic fluorinated lithium salt, and the negative active material includes silicon-carbon material. The composite separator 13 includes a base film 131, a first coating 132, and a second coating 133. The first coating 132 is disposed on the surface of the base film 131, and the second coating 133 is disposed on at least the surface of the first coating 132 facing the negative electrode 11. The first coating 132 includes a titanium-containing solid electrolyte, and the second coating 133 includes a second inorganic fluorinated lithium salt.

[0025] In the embodiments of this application, the titanium-containing solid electrolyte is a high-valence titanium (Ti) electrolyte. 4+ The electrolyte is an oxide electrolyte, such as a NASICON-type solid electrolyte or a perovskite-type solid electrolyte; the base membrane can be one or more of PE membrane, PP membrane, non-woven membrane, and PI membrane.

[0026] In some embodiments, a first coating is disposed on the surface of a base film; the first coating comprises: a titanium-containing solid electrolyte, an alkaline oxide, and a polymer adhesive; the titanium-containing solid electrolyte and the alkaline oxide are dispersed in the polymer adhesive; the alkaline oxide includes at least one of alumina and boehmite.

[0027] In some embodiments, the titanium-containing solid electrolyte may specifically be at least one of lithium lanthanum titanate (LLTO) and lithium titanium aluminum phosphate (LATP).

[0028] In this embodiment, a first inorganic fluorinated lithium salt is introduced into the negative electrode active material layer comprising silicon-carbon material, and a second coating comprising a second inorganic fluorinated lithium salt is introduced onto the surface of a first coating comprising a titanium-containing solid electrolyte. The first inorganic fluorinated lithium salt dispersed in the negative electrode active material layer preferentially participates in electrochemical reactions during the first charge-discharge process of the battery, guiding the formation of a solid electrolyte interface (SEI) film dominated by lithium fluoride (LiF) with high ionic conductivity and high mechanical stability. This not only optimizes the lithium-ion transport kinetics at the interface but also serves as a supplementary lithium source to compensate for irreversible lithium loss due to film formation. The second coating, including the second inorganic fluorinated lithium salt, acts as a fluorination barrier layer, which can retain ion transport channels and selectively block electron migration paths. The fluorinated SEI film on the negative electrode side and the fluorinated barrier layer on the solid electrolyte side evolve synergistically and couple with each other during battery formation. They can construct a composite interface phase with compositional and functional gradients in situ in the interface region, which can realize the spatial decoupling and functional separation of lithium ion transport paths and electron tunneling channels at the nanoscale. This fundamentally suppresses the reduction reaction of high-valence titanium from both thermodynamic and kinetic perspectives, and alleviates the "blackening" side reaction.

[0029] Therefore, the battery provided in this application can improve the interface compatibility problem between existing Si / C anodes and titanium-containing solid electrolytes.

[0030] Experiments show that the battery provided in this application embodiment can achieve a stable first coulombic efficiency of over 90% while maintaining the intrinsic high electronic conductivity of the electrode material. It also exhibits excellent rate performance and long-cycle stability, providing a practical interface solution for a new generation of high-energy-density and high-safety lithium-ion batteries for electric vehicles, large-scale energy storage and other fields.

[0031] In some embodiments, the structure of each layer in the composite membrane can be detected by scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS); the first inorganic fluorinated lithium salt in the negative electrode active material layer and the second inorganic fluorinated lithium salt in the second coating layer can also be detected by Fourier transform infrared spectroscopy, X-ray diffraction (XRD) patterns, X-ray photoelectron spectroscopy (XPS).

[0032] Optionally, in one embodiment, the positive electrode 12 includes a positive current collector 121 and a positive active material layer 122 disposed on the positive current collector 121. The positive active material layer 122 includes a positive active material, which includes at least one of lithium-rich manganese-based layered oxide, lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate.

[0033] Optionally, in one embodiment, the positive current collector includes at least one of pure aluminum current collector and composite aluminum current collector.

[0034] Optionally, in one embodiment, the positive current collector is a pure aluminum current collector, and the thickness of the pure aluminum current collector is 8~15 μm, for example, it can be one or any two of the following values: 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm.

[0035] Optionally, in one embodiment, the composite aluminum current collector includes a polymer substrate layer, a base layer, and a conductive layer stacked together, wherein the base layer is disposed between the polymer substrate layer and the conductive layer, and the base layer is used to increase the bonding force between the polymer substrate layer and the conductive layer.

[0036] In this embodiment, by providing an underlayer between the polymer substrate layer and the conductive layer, the bonding force between the polymer substrate layer and the conductive layer can be increased.

[0037] Optionally, in one embodiment, the material of the polymer substrate layer is selected from one or more blends or copolymers of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polyamide (PA), and polyphenylene sulfide (PPS). The thickness of the polymer substrate layer can be 1~8 μm, which can effectively balance safety, battery energy density, and processing economy.

[0038] Optionally, the thickness of the polymer substrate layer can be a range of one or any two of 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm.

[0039] Optionally, in one embodiment, the material of the underlayer is selected from one or more composites of metallic nickel, metallic titanium, and aluminum oxide, and the thickness of the underlayer is 10~1000 nm, which can effectively increase the bonding force between the polymer substrate layer and the conductive layer.

[0040] Optionally, the thickness of the underlayer can be 10 nm, 15 nm, 20 nm, 50 nm, 100 nm, 200 nm, 500 nm, 800 nm, or 1000 nm.

[0041] Optionally, in one embodiment, the conductive layer can be metallic aluminum or aluminum alloy, and the thickness of the conductive layer can be 0.1~2 μm, which is convenient to prepare by physical vapor deposition (PVD), chemical vapor deposition (CVD), electroplating and other methods, and can also effectively improve the overall conductivity of the composite current collector.

[0042] Optionally, the thickness of the conductive layer can be one or any two of the following: 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm.

[0043] In the battery provided in this application embodiment, the positive electrode sheet further includes a first conductive agent and a first binder; optionally, the first conductive agent includes at least one of graphite, hard carbon, soft carbon, carbon nanotubes, graphene, porous carbon, superconducting carbon black (Super P), acetylene black, and furnace black, and the first binder includes at least one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), silicone rubber, styrene-butadiene rubber (SBR), hydrogenated nitrile butadiene rubber (HNBR), boronized polyethylene glycol, cellulose, cellulose ester, cellulose ether, nitrocellulose, carboxyalkyl cellulose, cellulose salt, sodium carboxymethyl cellulose and cellulose salt derivatives, polyacrylic acid (PAA), polyamide (PAI), polyvinyl alcohol (PVA), polyethyleneimine (PEI), and polyimide (PI).

[0044] In some embodiments, the mass percentage of each component in the positive electrode active material layer is: 80-99 wt% positive electrode active material, 0.5-10 wt% first conductive agent, and 0.5-10 wt% additives.

[0045] When the mass percentage of the positive electrode active material in the positive electrode active material layer is within the above range, the positive electrode sheet can have a high specific capacity, which can fully utilize the rate performance of the battery and meet the battery's fast charging and discharging requirements.

[0046] In some embodiments, the positive electrode active material layer further contains 0.1-30 wt% of a solid electrolyte, while the proportions of the remaining components remain unchanged. The solid electrolyte includes, but is not limited to, one or more of the following: NASICON (sodium fast ion conductor) type solid electrolyte, LISICON (lithium fast ion conductor) type solid electrolyte, garnet type solid electrolyte, perovskite type solid electrolyte, anti-perovskite type solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer electrolyte. The polymer electrolyte includes polymers and lithium salts; polymers include, but are not limited to, PEO (ethylene oxide), PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene), PMMA (polymethyl methacrylate), and PAN (polyacrylonitrile); lithium salts include, but are not limited to, LiPF6, LiTFSI, LiFSI, and LiDFOB.

[0047] In some embodiments, the positive electrode sheet is prepared by a wet process: the components used to prepare the positive electrode sheet, such as the positive active material, the first binder and any other components, are dispersed in a solvent such as N-methylpyrrolidone to form a positive electrode slurry; the positive electrode slurry is coated on both sides of a positive current collector with a base coating on its upper and lower surfaces; after baking, rolling, cutting and slitting, the positive electrode sheet can be obtained.

[0048] In some embodiments, the positive electrode sheet is prepared by fibrillation: the components used to prepare the positive electrode sheet, such as the positive active material, binder and any other components, are mixed, and shear force is applied to the mixed powder to fibrillate the binder to obtain a preform; the preform is extruded or rolled into a self-supporting film; the self-supporting film is loaded onto a positive current collector that is rolled between two rollers and has a base coating on its upper and lower surfaces, and after processes such as rolling, cutting and slitting, the positive electrode sheet can be obtained.

[0049] In some embodiments, the negative electrode current collector is selected from a metallic material that can conduct electrons. Preferably, the negative electrode current collector includes one or more of aluminum, nickel, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0050] The negative electrode sheet can be prepared according to conventional methods in the art. For example, the negative electrode active material layer is typically prepared by coating a negative electrode slurry, consisting of a negative electrode active material, a first inorganic fluorinated lithium salt, a negative electrode conductive agent, a negative electrode binder, and any other components, onto a negative electrode current collector, followed by drying and cold pressing. The solvent can be an aqueous solvent, but is not limited to it.

[0051] Optionally, in some embodiments, the silicon-carbon material surface also has a fluorinated carbon layer, that is, the negative electrode active material is a silicon-carbon composite material with a fluorinated carbon layer on the surface, which can form a fluorine-fluorine interface synergy with the second coating lithium fluoride through the surface fluorinated carbon layer, reduce the interface energy and enhance the interface compatibility; at the same time, the fluorinated carbon layer on the surface of the silicon-carbon material and the core silicon-carbon particles achieve structural locking through chemical bonding and mechanical intercalation, suppressing the particle pulverization caused by the volume expansion of silicon during the lithium insertion and extraction process, thereby maintaining the integrity of the electrode structure in a high silicon content (≥50%) system.

[0052] In some embodiments, fluorinated silicon carbon materials can be prepared in the following manner: Using fully dried commercial silicon-carbon anode material (silicon content ≥50%, particle size distribution 4~10 μm) as raw material, it is placed together with polyvinylidene fluoride (PVDF) powder in a planetary ball mill jar or other ball milling equipment. Under the protection of a protective gas such as argon, it is ball milled, for example, at a speed of 200 rpm~500 rpm for 1~5 hours, to achieve PVDF coating on the surface of silicon-carbon particles. The ball-milled mixture is then placed in a quartz boat in a tube furnace and heated to 450℃~550℃ at a rate of 1~10℃ / min under a continuous protective gas flow and held for annealing for 2~4 hours. This allows the PVDF to undergo intermediate-temperature pyrolysis, and the released active fluorine species react with the silicon surface to form Si-F bonds and a conductive carbon layer in situ, achieving stable interfacial fluorination. After the process is completed, the material is cooled to room temperature with the furnace under a protective atmosphere to obtain fluorinated silicon-carbon material.

[0053] Optionally, in some embodiments, the silicon-carbon material contains ≥50% silicon by mass and has a particle size of 4μm~10μm. This enables the silicon-carbon material to provide a suitable carrier for "dual-sided synergistic fluorination" interface engineering while possessing high energy density. Its high silicon content enhances the gain effect of fluorination modification on interface stability, while the micron-sized particle size is beneficial for achieving uniform coating of the fluorinated carbon layer to suppress interfacial side reactions and can also maintain the effective diffusion of lithium ions within the active particles, thereby synergistically improving the overall performance of the battery.

[0054] Optionally, in some embodiments, the silicon content in the silicon-carbon material is less than or equal to 70% by mass, so as to ensure energy density while maintaining stable cycle performance.

[0055] Optionally, in some embodiments, the mass content of the first inorganic fluorinated lithium salt in the negative electrode active material layer is 1% to 3%, for example, it can be one of 1%, 2%, 3% or any two of them, which can effectively compensate for the first lithium loss (pre-lithiation) and avoid causing a significant increase in interface impedance.

[0056] Optionally, in some embodiments, the first inorganic fluorinated lithium salt includes at least one of lithium fluoride and lithium hexafluorosilicate, which can be embedded in the negative electrode active layer in particulate form. It can preferentially participate in the electrochemical reaction during the first charge and discharge of the battery, and guide the formation of a solid electrolyte interface (SEI) layer dominated by lithium fluoride (LiF) with high ionic conductivity and high mechanical stability. This SEI can not only optimize the lithium ion transport kinetics at the interface, but also serve as a supplementary lithium source to compensate for irreversible lithium loss caused by film formation.

[0057] In some embodiments, the mass percentage of each component in the negative electrode active material layer is: 77-99 wt% negative electrode active material, 1%-3% first inorganic fluorinated lithium salt, 0-10 wt% conductive agent, and 0-10 wt% binder.

[0058] In some embodiments, the negative electrode active material layer includes a negative electrode active material, a first inorganic fluorinated lithium salt, a second conductive agent, a second binder, and a thickener.

[0059] In some embodiments, the second conductive agent includes one or more of Super-P (conductive carbon black), VGCF (vapor-grown carbon fiber), and CNT (carbon nanotube).

[0060] In some embodiments, the second adhesive includes one or more of PVDF (polyvinylidene fluoride), SBR (styrene-butadiene rubber), NBR (nitrile rubber), BR (polybutadiene rubber), CMC (sodium carboxymethyl cellulose), and PAA (polyacrylic acid).

[0061] In some embodiments, the thickener includes one or more of sodium alginate, sodium carboxymethyl cellulose, and carboxymethyl chitosan.

[0062] In some embodiments, the negative electrode current collector is selected from a metallic material that can conduct electrons. Preferably, the negative electrode current collector includes one or more of aluminum, nickel, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0063] The negative electrode sheet can be prepared according to conventional methods in the art. For example, the negative electrode active material layer is typically formed by coating a negative electrode slurry, consisting of a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and any other components, onto a negative electrode current collector, followed by drying and cold pressing. The solvent can be an aqueous solvent, but is not limited to it.

[0064] Optionally, in some embodiments, the mass content of the second inorganic fluorinated lithium salt in the second coating is 70% to 95%, for example, it can be one of 70%, 2%, 3% or any two of them. This can prevent the third binder from forming a continuous insulating phase, blocking the lithium ion transport channel, and causing a significant increase in interface impedance. It also ensures the mechanical strength and electron blocking reliability of the second coating, making it difficult to peel off from the membrane surface.

[0065] Optionally, in some embodiments, the second inorganic fluorinated lithium salt includes at least one of lithium fluoride and lithium hexafluorosilicate, which can effectively construct an electron blocking layer on the membrane side and suppress interfacial side reactions.

[0066] Optionally, in some embodiments, the thickness of the second coating is 3μm to 5μm, for example, it can be one of 3μm, 4μm, 5μm or any two of them, which can effectively balance the interface barrier effect and the mechanical strength of the second coating.

[0067] Optionally, in some embodiments, the second coating is a discontinuous structure, such as a patterned or lattice-shaped fluoride structure layer, which can effectively construct an electron blocking layer to suppress interfacial side reactions, ensure the effective transport of lithium ions, and cope with the mechanical stress of silicon volume expansion to avoid cracking failure.

[0068] Optionally, in some embodiments, the porosity of the second coating is 20% to 60%, for example, it can be one or any two of the following values: 20%, 21%, 25%, 30%, 40%, 50%, 60%, which can effectively construct an electron blocking layer, suppress interfacial side reactions, and ensure the effective transport of lithium ions.

[0069] Optionally, in some embodiments, the second coating further includes a third adhesive.

[0070] Optionally, in some embodiments, the third adhesive includes one or more of PVDF (polyvinylidene fluoride), SBR (styrene-butadiene rubber), NBR (nitrile rubber), BR (polybutadiene rubber), CMC (sodium carboxymethyl cellulose), and PAA (polyacrylic acid), which can effectively adhere the second inorganic fluorinated lithium salt to the surface of the first coating to form the second coating.

[0071] Optionally, in some embodiments, the third adhesive includes at least one of a fluoropolymer and a fluorinated modified elastomer; wherein the fluoropolymer includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and a polyvinylidene fluoride-hexafluoropropylene copolymer, which can effectively adhere the second inorganic fluorinated lithium salt to the surface of the first coating to form a second coating.

[0072] Optionally, in some embodiments, when applying the second coating to the surface of the first coating, the surface of the first coating (LATP ceramic layer) on the base film can be functionalized by physical activation or chemical modification methods to introduce hydroxyl, carboxyl, or amino functional groups, thereby improving its wettability and adhesion to the second inorganic fluorinated lithium salt slurry. The physical activation is preferably low-temperature plasma treatment with a power of 50W~800W and a treatment time of 10s~300s; or UV-ozone treatment with a treatment time of 1min~60min. The chemical modification preferably includes silane coupling agent treatment with a concentration of 0.05wt%~5wt%; or mild acid-base treatment with a treatment solution of 0.001M~0.5M dilute nitric acid, dilute hydrochloric acid, or dilute sodium hydroxide solution, and the treatment method is immersion at room temperature for 1 second~60 seconds.

[0073] Optionally, in some embodiments, the battery further includes an electrolyte, which includes lithium salts and organic solvents.

[0074] The electrolyte plays a role in conducting ions between the positive and negative electrodes. The electrolyte can be in liquid or gel state.

[0075] Electrolytes include electrolytes, which include liquid electrolytes, semi-solid electrolytes, and all-solid electrolytes. Semi-solid electrolytes are obtained by mixing liquid electrolytes and solid electrolytes in any proportion.

[0076] Liquid electrolytes, semi-solid electrolytes, and all-solid electrolytes are all used in one or more of the following: pouch cells, cylindrical cells, or prismatic cells.

[0077] In some embodiments, the electrolyte may be selected from inorganic solid electrolytes (halide solid electrolytes, oxide solid electrolytes, sulfide solid electrolytes), polymer solid electrolytes, and composite solid electrolytes (inorganic filler + polymer matrix).

[0078] In some embodiments, the solid electrolyte includes, but is not limited to, one or more of the following: NASICON (sodium fast ion conductor) type solid electrolyte, LISICON (lithium fast ion conductor) type solid electrolyte, garnet type solid electrolyte, perovskite type solid electrolyte, anti-perovskite type solid electrolyte, sulfide solid electrolyte, halide solid electrolyte, and polymer electrolyte. Polymer electrolytes include polymers and lithium salts; polymers include, but are not limited to, PEO (ethylene oxide), PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene), PMMA (polymethyl methacrylate), and PAN (polyacrylonitrile); lithium salts include, but are not limited to, LiPF6, LiTFSI, LiFSI, and LiDFOB.

[0079] In some embodiments, the electrolyte is a liquid electrolyte comprising an electrolyte salt and a solvent. The electrolyte salt is a lithium salt, and the solvent includes, but is not limited to, one or more of the following: ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, diphenyl carbonate, fluoroethylene carbonate, and dimethyl glycol ether.

[0080] In some embodiments, the electrolyte is a gel electrolyte, comprising a polymer matrix, a plasticizing solvent, and a lithium salt.

[0081] In some embodiments, the electrolyte is an in-situ polymerized electrolyte, comprising polymer monomers, lithium salts, solvents, and initiators.

[0082] In some embodiments, the electrolyte is a eutectic electrolyte, comprising a small molecule polar matrix and a lithium salt; or an ionic liquid electrolyte, comprising an ionic liquid and a lithium salt.

[0083] In some embodiments, the lithium salts mentioned above include, but are not limited to, lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroantimonyate (LiSbF6), lithium bis(trifluoromethanesulfonate imide) (LiTFSI or LiN(SO2CF3)2), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide (LiFSI or LiN(SO2CF3)2), lithium perchlorate (LiClO4), lithium iodide (LiI), and lithium magnesium bis(fluorosulfonyl)imide (Li2Mg(N(SO2CF3)2)2).

[0084] In practical applications, the negative electrode, separator, and positive electrode are stacked or wound in sequence, and then packaged to obtain a bare cell. After baking, the bare cell is injected with electrolyte, formed, resealed, and sorted to obtain the battery described above.

[0085] In some implementations, a liquid cylindrical battery, a pouch battery, or a prismatic battery can be formed by stacking or winding negative electrode plates, positive electrode plates, a composite separator, and an electrolyte. In some implementations, a semi-solid cylindrical battery, a pouch battery, or a prismatic battery can be formed by stacking or winding negative electrode plates, positive electrode plates, and gel electrolyte. In some implementations, a semi-solid cylindrical battery, a pouch battery, or a prismatic battery can be formed by stacking or winding negative electrode plates, positive electrode plates, solid electrolyte, and 0.5-50% electrolyte additives. In some implementations, a solid cylindrical battery, a pouch battery, or a prismatic battery can be formed by stacking or winding negative electrode plates, positive electrode plates, and a solid electrolyte.

[0086] The present invention also proposes an electrical device, wherein the battery described above is included, and the battery serves as the power supply for the electrical device.

[0087] Batteries can be used as a power source for electrical devices or as energy storage units for electrical devices. Electrical devices can include, but are not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0088] The above-described electrical device embodiment includes the aforementioned battery and achieves the same technical effect. To avoid repetition, it will not be described again here. For relevant details, please refer to the description of the battery embodiment.

[0089] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention is further described below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0090] The present invention will be described in detail below through embodiments.

[0091] Test method: (1) First-efficiency test: at 0.01~2.0V (vs. Li + At a voltage window of / Li and a rate of 0.1C, the first constant current discharge (lithiation, to 0.01V) and the first constant current charge (lithiation, to 2.0V) of the half cell were performed. The first coulombic efficiency ICE = (first charge capacity / first discharge capacity) × 100%.

[0092] (2) Cyclic test: Under the same voltage window, the constant current charging at 0.33C (to 2.0V) and constant current discharging at 1C (to 0.01V) were continuously cycled. The discharge capacity of the first and 200th cycles was recorded. The capacity retention rate CR = (discharge capacity of the 200th cycle / discharge capacity of the first cycle) × 100%.

[0093] (3) Rate test: After constant current charging at 0.1C (to 2.0V), discharge at constant current at 1C and 3C (to 0.01V) respectively, and record the corresponding discharge capacity C. 1C With C 3C 3C rate capacity retention rate = (C 3C / C 1C )×100%.

[0094] Unless otherwise specified, the techniques or conditions described in the literature in this field or the product instructions shall be followed. Reagents or instruments whose manufacturers are not specified are all commercially available standard products.

[0095] Example 1 (1) Battery fabrication: S10. By mass, 10 parts of fully dried commercial silicon-carbon anode material with a silicon content ≥50% and a particle size distribution of 4μm~10 μm were placed together with 1.1 parts of polyvinylidene fluoride (PVDF) powder in a planetary ball mill jar and dry-milled at 350 rpm for 3 hours under argon protection. The milled mixture was then placed in a quartz boat in a tube furnace and heated to 500℃ at a rate of 5℃ / min under a continuous argon flow and held for annealing for 3 hours. After the process was completed, the mixture was cooled to room temperature with the furnace under a protective atmosphere to obtain fluorinated silicon-carbon material (Si-C@F). S20. By mass, 0.2 parts of LiF powder were dissolved in deionized water, and after ultrasonic treatment to form a uniform suspension, 8.0 parts of fluorinated silicon carbon material were added. The mixture was mechanically stirred for 2 hours to achieve full loading. After centrifugation, washing, and vacuum drying at 85°C, LiF-loaded fluorinated silicon carbon material was obtained. S30. By mass, first, 0.1 parts of single-walled carbon nanotubes (SWCNTs) are ultrasonically dispersed in N-methylpyrrolidone (NMP) for 30 minutes. Then, 1.0 parts of binder PVDF are completely dissolved, and 8.0 parts of LiF-supported fluorinated silicon carbon material, 0.9 parts of conductive agent Super P and dispersion are added sequentially. The mixture is stirred at 2000 rpm for 4 hours to form a uniform slurry. This slurry is then coated onto a copper foil current collector and dried under vacuum at 110℃ to obtain the negative electrode sheet. S40. A commercial PE / LATP membrane (7μm PE base membrane + 2μm LATP coating) is activated by mild acid and alkali activation treatment to activate the surface. Then, lithium fluoride (LiF) powder and polyvinylidene fluoride (PVDF) binder are dispersed in NMP solvent at a mass ratio of 90:10 and ground to form a uniform slurry with a solid content of 20%. A second coating with a dry film thickness of 4μm is applied to the LATP coating surface of the membrane using an adjustable scraper with a gap of 20 μm. The wet film is cured in a vacuum environment at 80℃ for 12 hours to complete solvent evaporation. S50. In an argon glove box, place the negative electrode shell, negative electrode sheet, 15μL electrolyte, composite separator (second coating facing the negative electrode sheet), 15μL electrolyte, LATP solid electrolyte sheet, lithium metal sheet and gasket in sequence. Finally, cover with the positive electrode shell and seal using a coin cell packaging machine at 40 MPa to obtain a battery based on interface synergistic fluorination. The lithium salt in the electrolyte is 1M LiPF6, the solvent is ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1, and 2% by mass of fluoroethylene carbonate is added as a film-forming additive.

[0096] Examples 2-3 The difference between Examples 2 and 3 and Example 1 is that, in step S20, the amount of LiF powder added is adjusted to 0.1 parts and 0.3 parts, respectively.

[0097] Examples 4-6 The difference between Examples 4-6 and Example 1 is that, in step S40, the mass ratio of lithium fluoride (LiF) powder to polyvinylidene fluoride (PVDF) binder is adjusted to 80:20, 70:30, and 95:5.

[0098] Examples 7-8 The difference between Examples 7 and 8 and Example 1 is that, in step S40, the thickness of the dry film coated is adjusted to 5 μm and 3 μm, respectively.

[0099] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that steps S20 and S40 are omitted. In step S30, the LiF-supported fluorinated silicon carbon material is changed to a fluorinated silicon carbon material; In step S50, the composite membrane is adjusted to a commercial PE / LATP membrane (7μm PE base membrane + 2μm LATP coating).

[0100] Comparative Example 2 The difference between Comparative Example 1 and Example 1 is that steps S10 and S20 are omitted, and in step S30, the LiF-supported fluorinated silicon carbon material is changed to a silicon carbon material.

[0101] The batteries in each embodiment and comparative example were subjected to first-efficiency test, rate test and cycle life test, and the results are shown in Table 1.

[0102] Table 1

[0103] A comparison of the data from Examples 1 to 7 and Comparative Examples 1 and 2 in Table 1 shows that a complete dual-sided synergistic fluorination interface engineering is key to improving the overall performance of the battery. Comparative Example 1 only fluorinated the negative electrode; due to the failure to completely eliminate the blackening side reaction on the LATP side, its cycle stability and first-cycle efficiency were poor, with a capacity retention of only 65.4% and a first-cycle efficiency of 85.8%. Comparative Example 2 only fluorinated the separator; because it did not compensate for the loss of active lithium on the negative electrode side, its first-cycle efficiency further decreased to 82.4%, and its capacity retention was only 70.1%. In contrast, Example 1, through the synergistic effect of constructing a stable SEI on the negative electrode side and building an electron blocking layer on the separator side, achieved a high first-cycle efficiency of 93.9%, a capacity retention of 85.6% after 200 cycles, and a capacity retention of 88.3% at 3C rate, demonstrating a comprehensive performance improvement. The performance of Examples 2 and 3 under different process parameters further illustrates that precisely controlling the LiF compensation amount and the functional layer component ratio within the optimal process window is crucial for maximizing performance.

[0104] In summary, the dual-sided synergistic fluorination strategy proposed in this application solves the interfacial compatibility problem between high-silicon carbon anodes and titanium-containing solid electrolytes at the system level, providing an effective technical solution for the development of high-performance solid-state batteries.

[0105] In summary, the proposed solution has at least the following beneficial effects: (1) High initial coulombic efficiency: A stable Si / CF interface layer is constructed in situ by pyrolysis fluorination of PVDF on the negative electrode side, and the first inorganic fluorinated lithium salt is loaded as a sacrificial lithium source for targeted compensation, thereby increasing the initial coulombic efficiency of the battery to over 90%, effectively reducing active lithium loss and improving energy density utilization.

[0106] (2) Long-term cycle stability: Based on the "dual-sided synergistic fluorination" mechanism, the fluorination layer on the negative electrode side inhibits silicon volume expansion and enhances the stability of the SEI film. At the same time, the first inorganic fluorinated lithium salt incorporated can continuously repair the micro-damage of the SEI during cycling. The discontinuous fluorination layer on the membrane side can effectively limit the Ti content in the titanium-containing solid electrolyte. 4+ The reduction side reaction; the synergistic effect of the two makes the battery capacity retention rate significantly improved to over 85% after long cycles, greatly extending the service life.

[0107] (3) Excellent rate performance: The conductive carbon black and single-arm carbon nanotube composite conductive network constructed on the negative electrode side, combined with the ion transport channel optimized by the porous second coating on the separator side, significantly reduces the interfacial charge transfer impedance and improves the ion / electron transport efficiency, so that the battery can maintain excellent capacity retention at high rates.

[0108] (4) Enhanced intrinsic interfacial safety: By constructing a discontinuous second inorganic fluorinated lithium salt (LiF, etc.) electron blocking layer at the interface of the titanium-containing solid electrolyte, and by fully utilizing the wide electrochemical window (0~5.5 V), high melting point (~870℃), and intrinsic electronic insulation properties of the second inorganic fluorinated lithium salt, this functional layer can effectively suppress electron migration across the interface and effectively block Ti 4+ The reduction side reaction ("blackening") significantly enhances the intrinsic safety level of the battery while improving interface stability.

[0109] (5) Process compatibility and scalability: This invention is based on commercial silicon-carbon anode, composite membrane and conventional electrode preparation process, no special equipment is required, the parameters of key steps (such as solid phase fluorination and scraping) are controllable, with good process compatibility and large-scale production potential, and outstanding overall cost-effectiveness.

[0110] (6) Comprehensive performance synergistic optimization: Through the systematic interface engineering of "dual-sided synergistic fluorination", high first efficiency and long cycle life are achieved while taking into account high rate performance and safety, providing an innovative interface solution and feasible technical path for silicon-based batteries with high energy density and high safety.

[0111] Terminology Explanation In this application, "multiple" refers to two or more.

[0112] The terms “first,” “second,” “third,” “fourth,” etc., in this application (if any) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0113] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0114] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, if the method includes steps A and B, it means that the method may include steps A and B performed sequentially, or it may include steps B and A performed sequentially. For example, if the method may also include step C, it means that step C may be added to the method in any order. For example, the method may include steps A, B, and C, or it may include steps A, C, and B, or it may include steps C, A, and B, etc.

[0115] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A battery, characterized in that, It includes a negative electrode, a positive electrode, and a composite separator, wherein the composite separator is disposed between the negative electrode and the positive electrode; The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. The negative active material layer includes a negative active material and a first inorganic fluorine-containing lithium salt. The negative active material includes silicon-carbon material. The composite separator includes a base membrane, a first coating and a second coating. The first coating is disposed on the surface of the base membrane, and the second coating is disposed on the surface of the first coating at least facing the negative electrode. The first coating includes a titanium-containing solid electrolyte, and the second coating includes a second inorganic fluorine-containing lithium salt.

2. The battery according to claim 1, characterized in that, The first inorganic fluorinated lithium salt includes at least one of lithium fluoride and lithium hexafluorosilicate; and / or, The second inorganic fluorinated lithium salt includes at least one of lithium fluoride and lithium hexafluorosilicate.

3. The battery according to claim 1, characterized in that, The first inorganic fluorinated lithium salt has a mass content of 1% to 3% in the negative electrode active material layer; and / or, The second inorganic fluorinated lithium salt has a mass content of 70% to 95% in the second coating.

4. The battery according to claim 1, characterized in that, The thickness of the second coating is 3μm~5μm.

5. The battery according to claim 1, characterized in that, The second coating is a discontinuous structure; and / or, The porosity of the second coating is 20% to 60%.

6. The battery according to claim 1, characterized in that, The second coating further includes an adhesive, said adhesive comprising at least one of a fluoropolymer and a fluorinated modified elastomer; The fluoropolymer includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, and polyvinylidene fluoride-hexafluoropropylene copolymer.

7. The battery according to claim 1, characterized in that, The silicon-carbon material has a fluorocarbon layer on its surface.

8. The battery according to claim 1, characterized in that, The silicon-carbon material contains ≥50% silicon by mass and has a particle size of 4μm~10μm.

9. The battery according to claim 1, characterized in that, The battery also includes an electrolyte, which comprises lithium salt and organic solvent.

10. An electrical device, characterized in that, Includes the battery as described in any one of claims 1 to 9, wherein the battery serves as the power supply for the electrical device.

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