BYD's Innovations in Li-ion Battery

Lithium battery with lithium supplementation during cycling to improve energy density and cycle life. The battery has a lithium-supplementing pole piece with a protective layer that deforms under pressure to expose the lithium-containing active layer to the electrode. This allows lithium replenishment when needed during cycling without increasing the initial NP ratio. The protective layer prevents premature lithium reaction during manufacturing. The lithium supplementation fills vacancies in the electrodes to utilize more capacity and reduce lithium ion loss compared to fixed NP ratio batteries.

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Lithium-ion battery design with internal liquid injection and isolation features for high capacity and safety. The battery has multiple accommodation cavities separated by separators. Each cavity contains a connected set of pole shanks forming the battery core. The separators have injection holes connecting adjacent cavities. A block mechanism closes the holes to isolate the cavities. During manufacturing, the mechanism is open for injection. Afterwards, it closes to isolate the cavities. This allows injecting electrolyte into all cavities simultaneously. The mechanism can switch between open and closed positions. This enables injection, then closure to block direct connections between cavities. This prevents electrolyte leakage or mixing. The mechanism can also be a magnetic substance.

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Self-heating method, device, and system for lithium-ion batteries in electric vehicles that avoids battery polarization effects during heating. The method involves adaptively adjusting the heating frequency based on the phase difference between battery current and voltage signals. If the phase difference is less than a threshold, the heating frequency is increased to avoid lithium plating. If the phase difference doesn't change after frequency increase, it indicates a malfunction and stops heating. This allows effective heating without degradation compared to fixed frequency heating.

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Ternary cathode material for lithium-ion batteries with improved performance compared to conventional ternary cathode materials with secondary spherical structure. The new material is a single-crystalline ternary cathode material with a unique particle structure that has a central area with higher nickel content surrounded by a surface layer with lower nickel content. This composition and structure provides higher capacity and rate performance compared to traditional ternary cathode materials. It also has advantages like improved cycle life, reduced side reactions, and lower expansion due to the smooth surface and uniform composition. The single-crystalline particle structure is prepared by co-precipitation and solid-state sintering techniques.

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Lithium-ion battery with improved cycle life and reduced expansion by using a unique nanostructured positive electrode material with multiple nested cores. The material has a first core with multiple nested second cores, each with an optional cladding layer. The nested core structure prevents particle reorientation during rolling that can hinder lithium ion movement and expansion. The nested cores also provide more surface area for intercalation while reducing stress concentration during cycling compared to monolithic particles.

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A lithium ion battery with improved capacity and cycle life by optimizing the ratio of lithium iron phosphate (LFP) to ternary materials like nickel-rich cathode materials in the positive electrode. It also involves using the ternary materials to consume excess lithium ions formed during charging to help form a protective SEI film on the graphite negative electrode. The ratio of LFP to ternary capacity should be between 0.49 and 1.15, and the total LFP capacity should be at least 135 mAh/g. This balance prevents excessive lithium loss from the LFP while allowing the ternary material to contribute. It also improves cycle life by reducing dissolution of LFP elements like Fe and Mn. The ternary material residual alkali, electrolyte injection coefficient, and residual hydrogen

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Pole piece design for lithium-ion batteries that allows controlled replenishment of lithium ions during battery cycling to improve capacity retention. The pole piece has a current collector, a semiconductor layer, and a lithium replenishment layer sandwiched between them. The semiconductor layer can be turned on or off to selectively allow electron transfer between the current collector and replenishment layer. When the semiconductor layer is off, it blocks electron exchange and prevents lithium loss from the replenishment layer. When the semiconductor layer is on, it allows electron transfer between the current collector and replenishment layer to replenish lithium ions during battery cycling. This controlled replenishment improves capacity retention compared to one-time lithium supplementing methods.

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Lithium iron manganese phosphate composite material for lithium-ion batteries with improved low-temperature and rate performance, reduced manganese dissolution, and enhanced structural stability. The composite consists of an inner core doped with strontium and an outer shell doped with zirconium. The strontium-doped inner core allows higher manganese content for higher voltage and capacity, while the zirconium-doped shell reduces manganese leaching and improves compaction density. The strontium and zirconium doping helps prevent cracking during cell assembly, reducing manganese dissolution and improving battery cycling.

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A lithium battery anode with a protective layer that prevents lithium dendrite growth and improves battery safety. The protective layer contains a carbon matrix doped with cobalt and nitrogen, as well as coated transition metal particles. The doped carbon matrix improves lithium ion deposition uniformity, while the coated particles provide additional lithium-philic sites. This prevents dendrites from growing through the anode and shorting the battery.

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Ternary lithium-ion battery anode material with improved cycling and safety over traditional agglomerated ternary materials. The new ternary precursor is made by agglomerating primary particles with a sheet structure. The sheet primary particles have lengths of 10-100nm and thicknesses of 10-20nm. The agglomerated secondary particles have diameters of 10-50 μm. This sheet primary particle structure reduces cracking and gaps between particles compared to agglomerated spherical particles. The sheet primary particles are prepared by a method involving dispersing precursor salts in water, adjusting pH, and evaporating the water. The resulting ternary precursor is used to make the ternary lithium-ion battery anode material.

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Polymer separator for lithium-ion batteries that prevents polymer solution penetration into the separator during coating and improves battery performance. The separator has a porous substrate, a hydrophilic blocking layer between it and the polymer coating, and porous polymer coating with node structures. The hydrophilic blocking layer prevents polymer solution invasion. It allows the porous substrate to absorb electrolyte and transmit ions while reducing shrinkage and swelling. The porous polymer coating improves adsorption and reduces bulk impedance.

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Lithium-ion battery electrolyte composition and battery with improved cycle performance at both normal and high temperatures. The electrolyte contains a blend of two film-forming additives, vinylene carbonate (VC) and 2-hydroxyethyl methacrylate (HEMA). This combination provides enhanced cycle stability and reduces polarization at both normal and elevated temperatures compared to using VC alone. The battery with this electrolyte has improved normal temperature cycling, low temperature cycling, high temperature cycling, and storage stability compared to conventional electrolytes.

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A conductive agent for lithium ion battery electrodes that improves conductivity and performance compared to traditional carbon black. The agent is a mix of conductive carbon black, two types of carbon nanotubes, and graphene. The nanotubes have different tube lengths. This combination provides better electrical connection between the electrode active material and current collector compared to just using carbon black. The shorter nanotubes form line-to-line connections while the longer nanotubes provide point-to-point connections. The graphene helps further. The mass ratios of the components are in a specific range.

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Electrode binder for lithium batteries with improved binding and ionic conductivity, preventing swelling and slurry separation. The binder is an ionic liquid polymer with imidazole cations on the main chain. The binder is prepared by dissolving the polymer in water for ion exchange, then drying. The water removes impurities and prevents solvent dissolution. The binder is used in lithium battery electrodes to bind the active material to the current collector without swelling or slurry separation.

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Lithium ion battery with controllable design and long service life for electric vehicles. The battery has a unique configuration with an independent lithium supplementing electrode that can be precisely controlled to compensate for lithium loss during cycling. This allows optimizing the battery's N/P ratio and lithium supplementing amount for improved capacity and cycle life compared to traditional lithium supplementing methods. The independent lithium electrode is either an additional lithium supplementing electrode or a lithium film on the negative electrode. This provides a controllable and optimized lithium supplementing amount without affecting the N/P ratio as much as other methods.

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Positive electrode material, preparation method, and battery for lithium-ion batteries with improved performance, cycle life, and reduced gas generation. The positive electrode material consists of secondary composite particles made of primary particles. The key is controlling the particle size distribution to meet certain relations. The secondary particle diameter, primary particle diameter, specific surface area, and number of primary particles per secondary particle should satisfy specific relations. This balances factors like lithium diffusion, capacity, impedance, gas generation, and side reactions. Coating the positive electrode further improves battery performance.

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Cathode material for lithium-ion batteries with improved cycling stability and reduced sulfur dissolution. The material has a core-shell structure with a central area of lithium oxide surrounded by an intermediate layer of elemental sulfur and an outer shell containing elemental sulfur and carbon. The core-shell structure prevents sulfur dissolution by trapping it in pores and blocking electrolyte access. The carbon further blocks electrolyte and improves conductivity. The pore size and compaction density allow volume energy density increase. The core-shell structure is formed by a two-step process: co-precipitating a lithium oxide precursor, then melting sulfur into the precursor surface and carbonizing the outer shell.

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Lithium ion battery cathode material with improved stability and performance by coating the active particles with an array structure. The coating particles are smaller than the active particles and are arranged in an array around the active particles. This provides a structured coating that bonds tightly to the active particles without the need for large amounts of binder. The array structure prevents particle shedding and improves cathode stability during cycling compared to conventional coatings.

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A positive electrode design for lithium-ion batteries that provides improved electrochemical performance by optimizing the balance between electronic and ionic conductivity in the positive electrode. The positive electrode layer contains a lithium iron phosphate active material and a combination of conductive agents like carbon nanotubes, carbon black, and conductive graphite. The conductive agent loading and particle size are chosen to meet specific conditions that enable formation of a conductive network with both good electronic and ionic conductivity. The conditions include porosity, carbon black, graphite, and nanotube loading, and particle sizes. This optimized conductive network improves the lithium ion battery's electrochemical performance compared to conventional positive electrode designs.

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A positive electrode sheet for lithium-ion batteries that improves performance by optimizing the balance of conductivity and electrolyte diffusion in the positive electrode material layer. The sheet contains lithium iron phosphate as the positive active material, carbon black as the conductive agent, and follows specific ratios and conditions. The weight percentage of carbon black, conductive agent weight relative to active material, electrode tortuosity, and porosity are related in a range to balance electronic conductivity and electrolyte diffusion. This optimizes the positive electrode's dynamic performance and reduces impedance.

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Lithium battery design that improves low temperature performance by optimizing the balance between negative electrode layer thickness, specific surface area, electrolyte viscosity, and scaling factor between the negative electrode layers on opposite sides. The equation is: (single-sided negative electrode layer density in mg/cm²) × (thickness in μm) × (specific surface area in m²/g) = (electrolyte viscosity in mPa·s) × (scaling factor between negative electrode layers). This balancing allows complete electrolyte infiltration into the negative electrode for consistent SEI formation and low impedance at low temperatures.

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Battery management system that enables fast charging and discharging of lithium batteries at low temperatures. The system uses an internal heating circuit to generate heat inside the battery. This is done by converting DC to AC and applying the resulting current to specific points on the battery electrodes. The heating circuit can be controlled based on battery temperature. This allows evenly distributed heating of the battery core to prevent cold spots. By providing internal heating, the battery can charge and discharge at low temperatures without limitations. It also avoids using external heating pads which are bulky and inefficient. The heating circuit can be integrated into the battery management system.

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Battery module design for lithium-ion power batteries that improves reliability, maintainability, and manufacturability compared to conventional modules. The module has an integrated battery management system (BMS) inside the cell support bracket instead of separate components. This allows direct connection of the BMS circuitry to the cells without wiring and reduces space requirements. The BMS detects cell parameters, manages charging/discharging, and provides fault protection. The integrated BMS improves accuracy, reduces failures, and simplifies module assembly.

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Lithium-ion battery cathode with optimized conductivity layers to improve battery performance and cycle life. The cathode has a stack of anode layers with reduced binder and increased conductive agent content as you move away from the current collector. This provides better electrical connection between layers and between the anode and collector. It reduces impedance and improves charge/discharge efficiency and stability.

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Diaphragm for lithium ion batteries that improves heat resistance and eliminates the need for binders compared to traditional separators. The diaphragm has inorganic particles embedded in a base film with protruding portions. The particles are pressed into the molten base film to embed and protrude when cured. This stable connection without binders enhances heat resistance compared to coated particles. The diaphragm can be made by extruding the base film with embedded particles between rollers.

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A negative electrode design for high energy density lithium-ion batteries that prevents lithium plating and separates during high charge rates. The negative electrode has a controlled surface texture and composition to prevent lithium segregation during fast charging. The texture is characterized by a parameter k. By gradually increasing k on the surface of the negative current collector as it is coated with active material, the plating and separation issues are mitigated. This allows higher charge rates without capacity fade.

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Lithium ion battery cathode material with improved charge/discharge rate performance. The cathode material has a core-shell structure with an inner core containing graphite and hard carbon, an intermediate shell with pores filled with graphite, and an outer shell with hard carbon. The intermediate shell with graphite pores allows faster lithium ion transport compared to pure graphite. The pore-forming agent in the intermediate shell has high melting point, low reduction potential, and reacts with acid to remove after graphitization. This allows pore filling without blocking lithium ion channels.

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Electrode slice design for lithium-ion batteries that eliminates the need for a separator diaphragm, reducing cost and improving safety. The electrode slice has an insulating layer between the current collector and active material, protecting against short circuits. Protective layers at the edge further prevent shorting. The insulating layer is thin and porous to conduct ions. By integrating insulation directly onto the electrode, the separator is eliminated. This reduces battery cost, as well as simplifying production by eliminating the separator step.

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Negative electrode sheet for lithium-ion batteries that improves charge/discharge efficiency and cycle life. The sheet uses a carbon-based material made by mixing primary and secondary particle carbon. The primary particles have smaller size than secondary particles. This provides better kinetics while the secondary particles improve cycle stability. The sheet has a specific ratio of primary to secondary particles that optimizes performance. The mixed particle carbon also has a higher compaction density compared to using just secondary particles. The primary particles provide dense packing and the secondary particles reduce full electrode inflation. The mixed particle carbon has better charge/discharge efficiency and cycle life compared to pure secondary particles.

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Polymer composite membrane for lithium-ion batteries with improved thermal stability and mechanical strength. The membrane consists of a porous base membrane covered by a heat-resistant fiber layer. The base membrane can be a ceramic membrane. The fiber layer contains a heat-resistant polymer like PEI and a swellable polymer like PVDF-HFP. This provides heat resistance from PEI and ion conduction from PVDF-HFP. The fiber layer has high porosity and surface density to balance conductivity and bonding. The ceramic membrane has a controlled surface density for high thermal resistance without thickening.

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Lithium ion battery anode material, positive plate, and battery with improved stability, cycle life, and overcharge protection. The anode material contains a mixture of MnO2 and Li2CO3. The MnO2 supplements lithium during initial charge to prevent SEI film consumption. Li2CO3 prevents excessive lithium carbonate decomposition during overcharge. The mixed additive can be prepared by physically mixing MnO2 and Li2CO3 powders, or reacting soluble lithium and carbonate salts.

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Nickel-based lithium ion battery cathode material with improved lithium ion transport properties and electrochemical performance. The cathode material has a unique structure with a coating layer containing rock salt phase (LiF-type) material on the surface of secondary particles. The coating rate and particle size ratio of the secondary particles vs primary particles are optimized to enhance lithium ion migration. This synergistic effect of the rock salt coating and secondary particle structure improves cycling stability and rate capability compared to uncoated secondary particles. The rock salt coating prevents swelling and bubbles, while the secondary particles have larger diameter to facilitate ion diffusion.

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Ceramic diaphragm for lithium ion batteries with improved properties like temperature resistance, ionic conductivity, and electrolyte retention compared to conventional ceramic diaphragms. The ceramic diaphragm uses a grafted ceramic powder coating that enhances performance. The grafted ceramic powder is made by coating nano ceramic particles with grafted polyolefin polymer. The grafted polyolefin improves the diaphragm's wettability, stability, and temperature resistance compared to bare ceramic coatings. The grafting process involves dispersing the ceramic powder in solvent, adding a surfactant, thickener, and binder, and stirring at different speeds.

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Lithium ion battery anode material with improved electrochemical performance for high-rate charging and discharging. The material is a ternary (Ni,Mn,Co) oxide with a unique spherical structure containing petal-shaped lamellar units. The lamellar thickness is 150-300nm and the surface area perpendicular to thickness is 60000-300000nm². This structure enables better rate capability, higher first charge-discharge efficiency, and larger specific capacity compared to conventional ternary materials. The spherical shape allows higher current densities and reduces stress during charging. The material can be prepared by mixing the ternary precursor, lithium source, and mold fixing agent, and calcining.

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A positive electrode material for lithium-ion batteries with improved stability and cycle life by coating the active material with molybdenum disulfide (MoS2) and carbon. The coating isolates the active material from moisture and prevents corrosion. The coating process involves mixing LiMBO3 (where M is Mn, Fe, or Co) with molybdenum and carbon sources, then sintering to form MoS2 and carbon closely coating the LiMBO3. This provides better conductivity and isolation compared to just carbon coating.

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Lithium ion battery electrolyte with improved stability, safety, and cycle life by using two different ionic liquids with specific cation structures, a lithium salt, and a film-forming agent. The electrolyte contains a first ionic liquid with a trisubstituted imidazole cation where the 2-position hydrogen is replaced with methyl, and a second ionic liquid with a trisubstituted imidazole cation where the 1-position imidazole ring is connected to an amino or sulfonate group with a long chain. This electrolyte composition balances electrochemical stability, interfacial tension, and conductivity for better performance and safety compared to conventional lithium ion battery electrolytes.

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Lithium-ion battery separator with improved heat resistance and weight reduction compared to conventional separators. The separator has a coating layer containing first ceramic particles with core particles and nano-scale ceramic particles on the outer surface, and second ceramic particles. The first ceramic particles have a rougher surface than the second ceramic particles. The weight ratio of the first to second ceramic particles is 1:0.4-5. This provides a separator with better adhesion strength and support compared to just using the first ceramic particles. The ratio allows using less binder, reducing weight and thickness. The coating also contains a lower ratio of total ceramic particles to binder, further reducing weight.

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Solid electrolyte for lithium-ion batteries that provides improved safety and energy density compared to existing sulfide electrolytes. The electrolyte composition is a lithium sulfide-based compound with varying amounts of crystal water. The formula is Li2S-MS2·nH2O, where M is Si, Ge, or Sn, and n is 1-12. This composition avoids short circuits and dendrite formation in lithium metal batteries, improves cycle stability, and reduces polarization compared to other sulfide electrolytes. It also has lower sensitivity to moisture.

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Lithium ion battery electrolyte and battery with improved stability at high voltages. The electrolyte contains a lithium salt, solvent, and a first additive with a specific structure. The additive compound has a nitrogen-containing heterocyclic group and optionally a cyano-substituted phenyl group. It forms a stable interface film between the electrolyte and high-voltage cathode materials like nickel-rich oxides and polyanionic oxides. The film prevents oxidation of the electrolyte at high voltages and protects the cathode structure.

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Polymer composite membrane for lithium-ion batteries that balances mechanical strength and high-temperature stability. The membrane has a porous base membrane covered by a heat-resistant fiber layer. The fiber layer contains a high-melting point polymer (>180°C) and a lower-melting point polymer (<180°C) with high electrolyte absorption. This allows the high-melting point polymer to provide heat resistance and the lower-melting point polymer to absorb electrolyte and bond to the base membrane. The composite membrane has high ion conductivity, mechanical strength, and thermal stability for battery applications.

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A battery shell design that improves safety and thermal management of lithium-ion batteries by adding an outer shell with higher thermal conductivity than the inner shell. This allows quicker dissipation of heat generated during battery operation or abuse, preventing thermal runaway and potential explosions. The outer shell can partially cover the inner shell or completely surround it. The outer shell material has higher thermal conductivity than the inner shell to rapidly dissipate heat. This prevents internal temperatures from rising to dangerous levels during abnormal conditions.

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Lithium-ion battery positive electrode with improved performance and reduced manganese dissolution compared to conventional lithium manganese iron phosphate (LMIHP) cathodes. The improvement comes from a core-shell structure with carbon and molybdenum nitride (Mo2N) coatings. The carbon shell improves conductivity and the Mo2N shell reduces manganese dissolution during cycling. The core contains LMIHP. The positive electrode is prepared by mixing LMIHP with carbon and molybdenum precursors, then sintering in reducing/nitrogen atmosphere.

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Lithium-ion battery design to improve energy density, reduce dendrite formation, and mitigate safety issues like thermal runaway. The battery uses a unique repeating unit structure with two negative electrodes. The first negative electrode has an inorganic porous conductive layer sandwiched between an active material layer and an insulating layer. The second negative electrode is directly connected to the first negative electrode. When charging, the second negative electrode charges first, preventing dendrite growth. This allows higher voltage first negative electrode materials with lower voltage second negative electrode materials. The porous conductive layer enables high electronic conductivity and reduces resistance.

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Polymer composite membrane for lithium-ion batteries with improved thermal stability and safety. The membrane has multiple layers: a base membrane, ceramic layer, heat-resistant fiber layer, and bonding layer. The heat-resistant fiber layer contains a high melting point polymer and a lower melting point polymer with high liquid absorption. This allows the lower melting point polymer to swell in electrolyte and bond to the heat-resistant fiber network, improving thermal stability. The high melting point polymer provides backbone strength. The ceramic layer further improves thermal stability. By balancing fiber layer porosity, density, and polymer properties, the composite membrane has high ion conductivity and safety.

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Electrode sheet for lithium-ion batteries with improved performance and reliability. The electrode has a conductive layer between the current collector and active material. The conductive layer has indentations that protrude into the active material side. This provides better electrical connection between the active material and current collector, preventing separation and corrosion. The indentations can be formed using a specialized priming device with a textured gravure roll.

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Battery separator with improved safety and performance for lithium-ion batteries. The separator has a sandwich structure with a thin polyolefin membrane, a non-woven fabric layer, and two inorganic layers. The inorganic layers prevent shrinking and melting at high temperatures. The polyolefin membrane allows ion transport and the fabric provides strength. The inorganic layers have particles with sizes around 100 nm. A binder holds them together. This separator design improves safety and storage performance over organic-inorganic composites or nonwoven fibers.

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Polymer membrane for lithium ion batteries with improved air permeability, adhesion to electrodes, and ionic conductivity. The membrane is made by dispersing polyvinylidene fluoride (PVDF) particles in water with a binder, polyoxyethylene ether, fluorine-containing compound, and additives like cellulose or acrylate polymers. The dispersion is coated on a porous substrate and dried to form a membrane with a polymer particle layer attached to the surface. This membrane has high porosity, low impedance, and good adhesion to electrodes compared to traditional membranes.

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