Lithium dendrite-responsive coating and method of application, method of making electrode sheet, and battery

Abstract

This application belongs to the field of new energy battery technology, and particularly relates to a lithium dendrite-responsive coating and its application method, an electrode sheet preparation method, and a battery, comprising: a hollow porous heat-resistant insulating material, a conductivity regulating agent, a thermal conductivity enhancing agent, a dispersing agent, and a fixing agent; the conductivity regulating agent is used to regulate the conductivity of the lithium dendrite-responsive coating, so that after lithium dendrites puncture, a weak short-circuit signal that can be monitored by the battery management system is formed, wherein the mass content of the hollow porous heat-resistant insulating material is 40-70%, the mass content of the fixing agent is 20-50%, the mass content of the conductivity regulating agent is 0.5-10%, the mass content of the thermal conductivity enhancing agent is 0.5-10%, and the mass content of the dispersing agent is 0.5-2%. This solves the problems of existing positive electrode protection schemes easily interfering with the normal operation performance of the battery, difficulty in detecting internal short circuits, delayed response, and high risk of thermal runaway.

Description

Technical Field

[0001] This application belongs to the field of new energy battery technology, and in particular relates to a lithium dendrite-responsive coating and its application method, an electrode sheet preparation method, and a battery. Background Technology

[0002] Currently, the large-scale development and application of clean and low-carbon energy sources such as wind power and photovoltaics have become the core direction of energy transformation. However, wind power and photovoltaic energy have inherent characteristics of high volatility and randomness, requiring large-scale energy storage systems to ensure stable energy consumption and supply. Secondary battery energy storage systems, represented by lithium-ion batteries, have become the preferred technology solution for large-scale energy storage scenarios due to their advantages such as high energy density, high conversion efficiency, short construction period, and convenient installation, with extremely broad application prospects.

[0003] However, during long-term operation, secondary batteries such as lithium-ion batteries are prone to thermal runaway due to internal and external faults such as short circuits, overcharging, over-discharging, external heat sources, and mechanical damage. This can release a large amount of heat and explosive gases, leading to safety accidents such as fires and explosions. Their safety issues have become a technical challenge that urgently needs to be overcome in the field of energy storage.

[0004] From the perspective of fault risk, the risk of thermal runaway caused by external factors such as short circuits, external heat sources, and mechanical damage can be effectively avoided through electrical circuit protection, thermal monitoring, and mechanical protection. However, the hard-to-detect internal short circuit of the battery is the biggest source of fault risk for energy storage systems. Its core cause is the formation of lithium dendrites during battery charging and discharging. Lithium dendrites can pierce the separator, causing the positive and negative electrodes of the battery to conduct directly in a short time, triggering thermal runaway and the spread of the accident. Moreover, the early stage of lithium dendrite piercing the separator has no obvious signs and is extremely sudden, making it extremely difficult to monitor and prevent.

[0005] To improve battery safety, one existing industry solution is to coat the surface of the positive electrode current collector with a PTC (Positive Temperature Coefficient) safety coating. The principle is that as the battery temperature rises, the resistance of the PTC material increases, thereby increasing the resistance of the electrode active material layer and achieving power cut-off to prevent electrochemical reactions. However, this solution has significant drawbacks: First, the high resistance of the PTC material under normal operating conditions significantly reduces the battery's energy conversion efficiency and increases heat generation during operation, potentially inducing thermal runaway. Second, the PTC material cannot detect the formation of lithium dendrites; it can only passively respond to localized short circuits through temperature changes, resulting in a delayed response that often fails to effectively interrupt the spread of thermal runaway.

[0006] Therefore, the energy storage field urgently needs to develop a new coating technology: this coating has minimal impact on battery performance during normal battery operation and does not interfere with the safe operation of the battery. At the same time, it can actively detect the formation of lithium dendrites and respond quickly when a fault occurs inside the battery, thereby reducing the risk of thermal runaway caused by lithium dendrites from the root and improving the safety of secondary battery energy storage systems. Summary of the Invention

[0007] This application provides a lithium dendrite-responsive coating and its application method, an electrode preparation method, and a battery, aiming to solve to some extent the problems of existing positive electrode safety protection schemes easily interfering with the normal operation performance of the battery; and the difficulty in detecting internal short circuits caused by lithium dendrites in lithium iron phosphate batteries, the delayed response, and the high risk of thermal runaway.

[0008] In a first aspect, this application provides a lithium dendrite-responsive coating, comprising:

[0009] Hollow porous heat-resistant insulating material is used to resist lithium dendrite puncture of the diaphragm to block short circuits between the positive and negative electrodes;

[0010] Conductivity regulating agent is used to regulate the conductivity of the lithium dendrite response coating so that a short circuit signal is formed after the lithium dendrite is punctured. The conductivity regulating agent includes particulate conductivity regulating agent and fibrous conductivity regulating agent, and the mass ratio of the two is 1~5:1.

[0011] Thermal conductivity enhancers are used to dissipate heat from micro-short-circuit regions;

[0012] Dispersing agents;

[0013] Fixative;

[0014] The hollow porous heat-resistant insulating material comprises 40-70% by mass, the fixative comprises 20-50% by mass, the conductivity regulating agent comprises 0.5-10% by mass, the thermal conductivity enhancing agent comprises 0.5-10% by mass, and the dispersing agent comprises 0.5-2% by mass; the lithium dendrite-responsive coating has a puncture strength of 1000-10000 gf and a resistivity ρ in the range of 2.0 × 10⁻⁶ gf / ρ. 5 ~1.5×10 8 Ω·m, thickness is 6 / (ρ×10 -6 )~24 / (ρ×10 -6 )μm.

[0015] Furthermore, the hollow porous heat-resistant insulating material is one or more of the following: alumina, boehmite, silicon dioxide, titanium dioxide, magnesium oxide, gibbsite, hydrotalcite, calcium sulfate, magnesium silicate, calcium silicate, molecular sieve, and oxide solid electrolyte. The average particle size of the hollow porous heat-resistant insulating material ranges from 0.05 to 1 μm, the specific surface area is greater than 10 to 600 m² / g, and the average pore size is 0.5 to 2 nm.

[0016] Furthermore, the particulate conductivity regulating agent includes one or more of the following: charcoal, coke, activated carbon, fullerene, carbon black, acetylene black, Ketjen black, conductive graphite, and super conductive carbon black, and the average particle size of the particulate conductivity regulating agent ranges from 0.03 to 0.3 μm.

[0017] Furthermore, the fibrous conductivity regulating agent includes one or more combinations of carbon nanotubes, vapor-grown carbon fibers, and graphite fibers, and the average diameter of the fibrous conductivity regulating agent ranges from 3 nm to 300 nm, and the average length ranges from 1 to 20 μm.

[0018] Furthermore, the thermal conductivity enhancing agent is one or more of boron nitride, aluminum nitride, graphene microplates, and silicon carbide, with an average diameter ranging from 100 nm to 1000 nm.

[0019] Furthermore, the dispersing agent is one or a combination of lithium polyacrylate, sodium polyacrylate, and ammonium polyacrylate.

[0020] Furthermore, the fixative is polyvinylidene fluoride, polyvinyl alcohol, polyvinyl butyral, or poly(vinylidene fluoride). Hexafluoropropylene), sodium alginate, lithium alginate, polymethacrylic acid, polyacrylic acid, polyacrylic acid copolymer, vinylidene fluoride The copolymer of hexafluoropropylene, polyacrylate, polymethyl methacrylate, polyamide, polytetrafluoroethylene, polyhexafluoropropylene, acrylic acid, polyacrylonitrile, carboxymethyl chitosan, polyethylene oxide, and styrene-butadiene rubber are one or more of the following:

[0021] Secondly, this application provides a method for preparing an electrode sheet, which is prepared using the lithium dendrite-responsive coating described above, and includes the following steps:

[0022] SS100, the materials of the lithium dendrite-responsive coating are mixed with water at a mass ratio of 20:80 to form a coating slurry;

[0023] S200: Select a first electrode sheet with a positive electrode active material coated on its surface, and use a gravure roller to coat the surface of the first electrode sheet with a coating slurry to obtain a second electrode sheet with a pre-coated coating slurry on its surface.

[0024] S300, the second electrode sheet is dried and then rolled to obtain an electrode sheet with a lithium dendrite response coating on its surface.

[0025] Thirdly, this application provides a battery, including the aforementioned electrode sheets, as well as a negative electrode sheet, a separator, an electrolyte, a battery casing, and connectors.

[0026] Fourthly, this application provides a method for applying a lithium dendrite-responsive coating, which uses a battery management system to monitor the battery containing the aforementioned lithium dendrite-responsive coating to determine whether the following fault conditions occur:

[0027] (1) Under static conditions, the difference between the monitored rate of battery voltage drop and the average rate of drop of other batteries in the same module is >0.010V / 1h;

[0028] (2) The battery voltage experiences a sudden drop with an instantaneous rate of decrease >10mV / s;

[0029] (3) When charging to the 3.3V~3.4V range, the difference between the average voltage plateau of other batteries in the same module and the battery voltage plateau is >20mV;

[0030] (4) The difference between the monitored battery body temperature and the average temperature of other batteries in the same module is >5℃;

[0031] When any one of the above conditions is met, a level one warning for lithium dendrite formation is triggered; when any two or more of the above conditions are met, it is determined that the battery has experienced an internal short circuit fault caused by lithium dendrite formation.

[0032] The advantages of this application compared to the prior art are:

[0033] This application addresses the performance interference issues and safety hazards caused by lithium dendrites in existing cathode safety protection schemes through the synergistic cooperation of various functional components using a lithium dendrite-responsive coating and its application. It achieves low performance interference during normal battery operation and constructs an active response system of "blocking-monitoring-heat dissipation," thus comprehensively resolving the core contradiction between safety and performance in secondary battery energy storage systems.

[0034] Regarding the issue that "existing solutions easily interfere with normal battery operation": the coating uses a 2.0×10 5 ~1.5×10 8 The high resistance design (Ω·m), combined with a low proportion of granular and fibrous conductive modifiers, prevents the formation of a continuous conductive network during normal operation. This ensures insulation without increasing the battery's internal ohmic resistance or reducing energy conversion efficiency. The coating thickness is 6 / (ρ×10). -6 )~24 / (ρ×10 -6The coating's micrometer size is precisely matched to its resistivity, meeting the mechanical strength requirements for blocking lithium dendrites without hindering lithium ion migration. This ensures that the battery's core performance, such as charge / discharge rate and capacity retention, remains unaffected. Through the synergistic effect of fixatives and dispersants, the coating adheres uniformly and stably without the risk of peeling or agglomeration, avoiding damage to ion transport pathways caused by coating structure failure and further ensuring normal battery operation.

[0035] To address the issues of "difficult-to-detect internal short circuits caused by lithium dendrites and high risk of thermal runaway": A hollow, porous, heat-resistant insulating material with a high proportion of 40-70% and a high puncture strength of 1000-10000gf can directly resist lithium dendrite punctures into the separator, blocking short circuits between the positive and negative electrodes at the source and significantly reducing the risk of hard short circuits; a mass ratio of granular to fibrous conductive additives of (1-5):1 constructs an adapted conductive network, forming a weak short-circuit signal that can be captured by the battery management system in the early stages of lithium dendrite puncture without affecting the insulation effect, transforming "sudden failure" into "predictable intervention," and reserving sufficient time for fault handling; a thermal conductivity enhancing additive with a proportion of 0.5-10% quickly dissipates heat from the micro-short circuit area, avoiding a sudden temperature rise, thus delaying battery performance degradation and further reducing the probability of thermal runaway triggering; the ratio design of fixatives and dispersants ensures a multi-functional synergistic balance of "insulation blocking, conductivity monitoring, and thermal conduction," without functional failures or coating peeling issues.

[0036] Furthermore, the correlation design between coating thickness and resistivity allows for flexible adaptation to various secondary batteries such as lithium-ion and sodium-ion batteries, making it highly practical. In summary, this invention not only solves the performance interference problems of existing solutions but also fundamentally addresses the safety challenges of difficult-to-detect and delayed-response lithium dendrite short circuits, comprehensively improving the safety and operational stability of secondary battery energy storage systems. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application, 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic flowchart of the preparation method of the electrode sheet of this application. Detailed Implementation

[0039] To make the technical problems, technical solutions, and beneficial effects of 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.

[0040] In this application, the term "and / or" describes 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. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0041] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, a~b (i.e., a and b), a~c, b~c, or a~b~c, where a, b, and c can be single or multiple.

[0042] The terms "first" and "second" are used only to describe the purpose and to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the provisions of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0043] The terminology used in the embodiments of this application is for the purpose of describing particular implementations only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the implementations of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0044] It should be understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0045] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0046] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0047] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application are available on the market or can be prepared by existing methods.

[0048] Existing safety coatings using PTC materials exhibit high resistance under normal operating conditions, significantly reducing battery energy conversion efficiency and increasing heat generation during operation, potentially inducing thermal runaway. Secondly, PTC materials cannot detect lithium dendrite formation and can only passively respond to localized short circuits through temperature changes. This delayed response often fails to effectively interrupt the spread of thermal runaway.

[0049] To address the aforementioned issues to some extent, this application provides a lithium dendrite-responsive coating and its application method, an electrode preparation method, and a battery. The aim is to resolve, to some extent, the problems of existing positive electrode safety protection schemes easily interfering with the normal operation of the battery; and the difficulty in detecting and the delayed response to internal short circuits caused by lithium dendrites in lithium iron phosphate batteries, resulting in a high risk of thermal runaway.

[0050] In a first aspect, this application provides a lithium dendrite-responsive coating, comprising:

[0051] Hollow porous heat-resistant insulating material is used to resist lithium dendrite puncture of the diaphragm to block short circuits between the positive and negative electrodes;

[0052] Conductivity regulating agent is used to regulate the conductivity of the lithium dendrite response coating so that a short circuit signal is formed after the lithium dendrite is punctured. The conductivity regulating agent includes particulate conductivity regulating agent and fibrous conductivity regulating agent, and the mass ratio of the two is (1~5):1.

[0053] Thermal conductivity enhancers are used to dissipate heat from micro-short-circuit regions;

[0054] Dispersing agents;

[0055] Fixative;

[0056] The hollow porous heat-resistant insulating material comprises 40-70% by mass, the fixative comprises 20-50% by mass, the conductivity regulating agent comprises 0.5-10% by mass, the thermal conductivity enhancing agent comprises 0.5-10% by mass, and the dispersing agent comprises 0.5-2% by mass; the lithium dendrite-responsive coating has a puncture strength of 1000-10000 gf and a resistivity ρ in the range of 2.0 × 10⁻⁶ gf / ρ. 5 ~1.5×10 8Ω·m, thickness is 6 / (ρ×10 -6 )~24 / (ρ×10 -6 )μm.

[0057] In this embodiment, the lithium dendrite-responsive coating is applied to a battery and includes a hollow porous heat-resistant insulating material, a conductivity regulating agent, a thermal conductivity enhancing agent, a dispersing agent, and a fixing agent. The hollow porous heat-resistant insulating material has a mass content of 40-70%, the fixing agent has a mass content of 20-50%, the conductivity regulating agent has a mass content of 0.5-10%, the thermal conductivity enhancing agent has a mass content of 0.5-10%, and the dispersing agent has a mass content of 0.5-2%. The hollow porous heat-resistant insulating material serves as the coating body, providing a protective foundation. The conductivity regulating agent and the thermal conductivity enhancing agent serve as functional additives to achieve responsive upgrades, while the dispersing agent and the fixing agent serve as protective additives to maintain structural stability. In use, the coating is applied to the surface of the active material layer of the battery electrode and then dried and rolled to ensure that the components are evenly distributed and firmly attached. The hollow porous heat-resistant insulating material forms the coating skeleton, and the conductivity regulating agent (the mass ratio of particulate to fibrous is (1~5):1) and the thermal conductivity enhancing agent are discretely distributed in the skeleton. The dispersing agent and the fixing agent fill the gaps to form a synergistic structure of "skeleton-function-protection".

[0058] The lithium dendrite-responsive coating utilizes a synergistic system of "high resistance characteristics + low proportion of compounded conductive additives" to upgrade the existing passive protective coatings in batteries that "sacrifice performance for safety" to a multifunctional coating that combines "low interference + active response." This ensures normal battery operation while achieving full-process control over lithium dendrite risks. The coating uses a 2.0×10⁻⁶... 5 ~1.5×10 8 The high resistance characteristic design (Ω·m) is combined with a low proportion of 0.5~10% granular and fibrous composite conductivity modifiers. These conductive modifiers are distributed in a discrete form, preventing the formation of a continuous conductive network. This ensures the coating's insulation without increasing the battery's internal resistance (ohmic resistance), avoiding decreased energy conversion efficiency and additional heat generation. Simultaneously, the coating thickness is controlled at 6 / (ρ×10). -6 )~24 / (ρ×10 -6 The precise matching of μm and resistivity effectively blocks electrons. Combined with the porous structure of hollow porous heat-resistant insulating material, it meets the puncture strength requirements of 1000~10000gf without hindering lithium-ion migration, ensuring the stability of core performance such as battery charge and discharge rate and capacity retention, and perfectly solving the pain point of existing protection solutions interfering with the normal operation of the battery.

[0059] To address the risk of lithium dendrite formation, the coating employs a triple synergistic response system of "blocking, monitoring, and heat dissipation": 40-70% high-percentage hollow porous heat-resistant insulating material serves as the framework, directly resisting lithium dendrite punctures into the separator with its high puncture strength, thus blocking short circuits between the positive and negative electrodes at the source and significantly reducing the risk of hard short circuits; the mass ratio of particulate to fibrous conductivity regulating additives is (1-5):1, which, without affecting the overall insulation of the coating, forms a weak short-circuit signal that can be captured by the battery management system in the early stages of lithium dendrite puncture, transforming "sudden failure" into "predictable intervention," allowing sufficient time for fault handling; 0.5-10% thermal conductivity enhancing additives establish thermal conduction pathways within the coating, rapidly dissipating localized heat from the micro-short circuit area, preventing sudden temperature increases that accelerate battery degradation, and further reducing the probability of thermal runaway triggering.

[0060] Meanwhile, by utilizing a stable system of "dispersant + fixative", the structural integrity of the coating is achieved throughout its entire life cycle: the dispersant optimizes the interfacial forces of the components, avoids particle agglomeration, and ensures the uniform distribution of hollow porous heat-resistant insulating materials, conductive additives, and thermally conductive additives, preventing local functional failure; the fixative, with a high proportion of 20-50%, firmly binds the components into a film, preventing coating peeling and cracking even during the volume expansion or contraction cycles of long-term battery charging and discharging, maintaining the stability of the skeleton structure, and ensuring the continuous performance of the "blocking-monitoring-heat dissipation" function.

[0061] Based on this, the lithium dendrite-responsive coating has minimal impact on battery performance during normal operation, and can quickly activate multiple protections when lithium dendrite risks occur. It not only achieves a functional upgrade from "physical blocking" to "early warning + heat dissipation + blocking", but also breaks the inherent contradiction of "safety and performance cannot be achieved at the same time" in existing safety protection solutions. It comprehensively improves the safety and operational stability of secondary battery energy storage systems, and is compatible with various secondary batteries such as lithium-ion and sodium-ion batteries and different packaging forms, with broad application prospects.

[0062] Furthermore, the hollow porous heat-resistant insulating material is one or more of the following: alumina, boehmite, silicon dioxide, titanium dioxide, magnesium oxide, gibbsite, hydrotalcite, calcium sulfate, magnesium silicate, calcium silicate, molecular sieve, and oxide solid electrolyte. The average particle size of the hollow porous heat-resistant insulating material ranges from 0.05 to 1 μm, the specific surface area is greater than 10 to 600 m² / g, and the average pore size is 0.5 to 2 nm.

[0063] In this embodiment, the selected materials such as alumina, boehmite, and silicon oxide all possess excellent temperature resistance, chemical stability, and insulation properties. They can withstand the corrosion of the battery's internal electrolyte, temperature fluctuations during charge-discharge cycles, and localized high temperatures during lithium dendrite puncture. They will not decompose, swell, or chemically deteriorate, and can maintain stable insulation and mechanical properties over a long period of time, avoiding a decrease in protective function due to material failure. This is suitable for the long-cycle, high-safety energy storage scenarios required for secondary batteries. The average particle size range of the hollow porous temperature-resistant insulating material is limited to 0.05~1μm. This particle size range precisely matches the coating preparation and usage requirements. If the particle size is too small (<0.05μm), it is easy to cause particle agglomeration, which will damage the porous structure of the coating and ion transport pathways; if the particle size is too large (>1μm), it will affect the coating uniformity, reduce the puncture strength, and hinder lithium ion migration. Therefore, a particle size of 0.05~1μm allows the material to be uniformly dispersed under the action of dispersing agents, forming a dense and continuous coating skeleton. This ensures a puncture strength of 1000~10000gf, effectively resisting lithium dendrite puncture, while preventing the formation of ion transport barriers due to particle accumulation, ensuring smooth lithium ion migration. Limiting the specific surface area of ​​the hollow porous heat-resistant insulating material (>10m² / g) enhances the coating structure stability and ion transport efficiency: a high specific surface area means abundant active sites on the material surface, significantly increasing the contact area with fixatives, conductivity modifiers, and thermal conductivity enhancers. This strengthens the bonding force between components, allowing the coating to form a dense, non-detachable whole, preventing cracking and powder shedding during battery charge / discharge volume expansion / contraction cycles. Simultaneously, a high specific surface area corresponds to a richer porous structure, which can fully adsorb electrolyte, providing ample channels for lithium ion migration, further reducing ion transport resistance, and ensuring that battery charge / discharge performance is not affected. The average pore size of the hollow porous heat-resistant insulating material is set to >0.5nm to precisely match the lithium-ion transport requirements: the design with an average pore size greater than 0.5nm ensures that the electrolyte can fully penetrate into the material pores, creating a continuous pathway for lithium-ion migration (the lithium-ion radius is about 0.076nm, which can freely pass through this pore size), avoiding the blockage of ion transport due to the pore size being too small; at the same time, the porous structure can retain the buffering performance of the coating, adapting to slight volume changes during battery operation. In addition, the porous structure can also assist the thermal conductivity enhancement agent in dissipating local heat, improving the heat dissipation uniformity of the coating, and synergistically reducing the risk of thermal runaway.

[0064] Furthermore, the particulate conductivity regulating agent includes one or more of the following: charcoal, coke, activated carbon, fullerene, carbon black, acetylene black, Ketjen black, conductive graphite, and super conductive carbon black, and the average particle size of the particulate conductivity regulating agent ranges from 0.03 to 0.3 μm.

[0065] In this embodiment, the selected materials, such as charcoal, coke, activated carbon, carbon black, and acetylene black, are all mature conductive functional materials in the battery field. They possess excellent electronic conductivity, chemical stability, and electrolyte compatibility. Under long-term charge-discharge cycles, electrolyte immersion, and temperature fluctuations, they do not decompose, swell, or undergo side reactions with other components, maintaining stable conductivity. This provides a reliable material basis for capturing weak short-circuit signals after lithium dendrite puncture, preventing monitoring function failure due to material failure. The average particle size (0.03~0.3μm) of the particulate conductivity regulating agent optimizes the conductive network construction and functional balance: This particle size range is precisely designed for: Firstly, compared to hollow porous heat-resistant insulating materials (0.05~1μm), the particulate conductive agent has a smaller particle size, allowing it to be uniformly dispersed in the pores or gaps of the insulating material. This avoids the formation of "conductive agglomerates" inside the coating due to excessively large particle size (avoiding interference with the overall insulation of the coating), and also prevents particle agglomeration due to excessively small particle size (<0.03μm), ensuring conductivity. The additives exist in a "discrete distribution" form; secondly, the particle size of 0.03~0.3μm can maximize the specific surface area of ​​the conductive additives and enhance the contact probability with fibrous conductive additives. The two work together to construct a "point-line combination" adaptive conductive network, which will not form a continuous conductive path (avoiding the increase of ohmic internal resistance during normal battery operation), and can respond quickly when lithium dendrites puncture. Through the "bridging effect" of lithium dendrites, a monitorable weak short-circuit signal is formed, achieving a functional balance of "no interference when not in fault condition and accurate response when in fault condition".

[0066] Furthermore, the fibrous conductivity regulating agent includes one or more combinations of carbon nanotubes, vapor-grown carbon fibers, and graphite fibers, and the average diameter of the fibrous conductivity regulating agent ranges from 3 nm to 300 nm, and the average length ranges from 1 to 20 μm.

[0067] In this embodiment, the selected carbon nanotubes, vapor-grown carbon fibers, and graphite fibers are all high-performance conductive materials in the battery field, possessing excellent electronic conductivity, chemical stability, and mechanical strength. They do not decompose, oxidize, or fracture under extreme conditions such as immersion in the battery's internal electrolyte, temperature fluctuations during charge-discharge cycles (-20℃~60℃), and lithium dendrite puncture impact, maintaining stable conductivity over a long period. Simultaneously, these materials exhibit strong compatibility with other coating components (insulating materials, fixatives, thermally conductive agents, etc.), with no risk of side reactions, providing a reliable material basis for the continuous and stable capture of weak short-circuit signals and preventing monitoring function attenuation or failure due to material failure. The nanoscale design with an average diameter of 3nm~300nm: this size is far smaller than the particle size (0.05~1μm) of hollow porous heat-resistant insulating materials and the coating thickness (6 / (ρ×10⁻⁶)). -6 )~24 / (ρ×10 -6With a diameter of 0.03 μm, it can be easily dispersed in the pores or intercomponent gaps of insulating materials without damaging the coating skeleton structure due to excessive size, nor forming a continuous conductive path (avoiding an increase in the ohmic internal resistance during normal battery operation). Simultaneously, the nanoscale diameter maximizes the aspect ratio and specific surface area of ​​the material, enhancing the density and uniformity of conductive sites, laying the foundation for signal capture sensitivity. An average length >2 μm ensures that the fibrous additive forms a "linear conductive skeleton," complementing the particulate conductive additive (0.03~0.3 μm) with a "line-point complementarity." The fibrous additive builds cross-regional conductive connection channels, while the particulate additive fills the channel gaps, avoiding the "conductive blind spots" of a single conductive additive. Furthermore, a reasonable aspect ratio balances "dispersion" and "conductive connectivity": a length >2 μm ensures the probability of contact with other conductive particles, preventing the conductive network from breaking due to excessive length; simultaneously, it prevents fiber entanglement and aggregation due to excessive length, ensuring uniform distribution in the coating in a "discrete linear" form, achieving a functional balance of "non-conductive under normal conditions and rapid bridging under fault conditions."

[0068] Furthermore, the thermal conductivity enhancing agent is one or more of boron nitride, aluminum nitride, graphene microplates, and silicon carbide, with an average diameter ranging from 100 nm to 1000 nm.

[0069] In this embodiment, the selected boron nitride, aluminum nitride, graphene microsheets, and silicon carbide are all high-performance "thermally conductive and insulating" dual-functional materials used in the battery field. On one hand, they possess excellent thermal conductivity (far exceeding that of other components in the coating), enabling rapid conduction of localized heat; on the other hand, they exhibit excellent insulation properties, ensuring that the addition of thermally conductive additives does not compromise the overall high-resistivity characteristics of the coating (2.0 × 10⁻⁶). 5 ~1.5×10 8(Ω·m), avoiding the creation of additional electronic pathways or increasing battery internal resistance. At the same time, this type of material has strong chemical stability, is resistant to electrolyte corrosion and high temperature, and will not decompose or deteriorate under long-term battery cycling and micro-short-circuit high-temperature conditions. It can maintain stable thermal conductivity and insulation performance over a long period of time, meeting the reliability requirements of long-term operation of energy storage batteries. This particle size range is precisely designed for two reasons: First, it matches the particle size of hollow porous heat-resistant insulating materials (0.05~1000nm) and complements the size of particulate conductivity modifiers (0.03~0.3μm). It can be uniformly dispersed in the pores and intercomponent gaps of the coating skeleton, avoiding particle agglomeration and blockage of ion transport channels due to excessively small particle size (<100nm), and also avoiding damage to the coating density or hindering lithium ion migration due to excessively large particle size (>1μm). Second, the particle size of 100nm~1000nm maximizes the contact area between the thermally conductive agent and other components, forming a continuous and uniform thermally conductive path inside the coating. This avoids uneven heat dissipation caused by the enrichment of thermally conductive agents in a single area, and ensures that the local heat generated in the micro-short circuit area is quickly diffused to the entire coating, rather than accumulating at the fault point, thus suppressing the sudden temperature rise from the source.

[0070] Furthermore, the dispersing agent is one or a combination of lithium polyacrylate, sodium polyacrylate, and ammonium polyacrylate.

[0071] In this embodiment, the selected lithium polyacrylate, sodium polyacrylate, and ammonium polyacrylate are all mature polymeric electrolyte dispersants in the battery field, possessing three core advantages: First, these materials exhibit excellent chemical stability, exhibiting no side reactions with electrolytes, hollow porous heat-resistant insulating materials, conductive additives, and thermally conductive additives. They are resistant to electrolyte corrosion and high temperatures, and will not decompose or deteriorate under long-cycle battery conditions. Second, their hydrophilicity and film-forming properties are well-suited for coating slurry preparation, allowing for rapid dissolution in aqueous slurries without the need for additional organic solvents, thus adapting to environmentally friendly coating preparation processes. Third, as ionic compounds, they do not introduce impurity ions and do not participate in electrochemical reactions during battery charging and discharging, thus not interfering with the core performance of the battery. The various functional components in the coating (insulating materials, particulate / fibrous conductive additives, and thermally conductive additives) have a large particle size range (3nm~1μm) and differences in density and surface properties, making them prone to aggregation.

[0072] The fixative is polyvinylidene fluoride, polyvinyl alcohol, polyvinyl butyral, or polyvinylidene fluoride. Hexafluoropropylene), sodium alginate, lithium alginate, polymethacrylic acid, polyacrylic acid, polyacrylic acid copolymer, vinylidene fluoride The copolymer of hexafluoropropylene, polyacrylate, polymethyl methacrylate, polyamide, polytetrafluoroethylene, polyhexafluoropropylene, acrylic acid, polyacrylonitrile, carboxymethyl chitosan, polyethylene oxide, and styrene-butadiene rubber are one or more of the following:

[0073] Secondly, this application provides a method for preparing an electrode sheet, which is prepared using the lithium dendrite-responsive coating described above, and includes the following steps:

[0074] S100, the materials of the lithium dendrite-responsive coating are mixed with water at a mass ratio of 20:80 to form a coating slurry;

[0075] S200: Select a first electrode sheet with a positive electrode active material coated on its surface, and use a gravure roller to coat the surface of the first electrode sheet with a coating slurry to obtain a second electrode sheet with a pre-coated coating slurry on its surface.

[0076] S300, the second electrode sheet is dried and then rolled to obtain an electrode sheet with a lithium dendrite response coating on its surface.

[0077] In this embodiment, for step S100, the aqueous slurry system, in which each material is mixed with water at a mass ratio of 20:80, does not require the addition of organic solvents. This reduces environmental risks and costs during production and is perfectly compatible with the hydrophilic properties of dispersing agents (such as lithium polyacrylate). Water, as a solvent, allows the dispersing agents to fully ionize and function, promoting the uniform dispersion of components such as hollow porous heat-resistant insulating materials, conductive agents, and thermally conductive agents, avoiding component agglomeration. This ensures that the distribution of each functional component in the slurry is consistent with the initial design intent of the coating, laying the foundation for the subsequent "low-interference-multi-functional synergy" of the electrode sheet. At the same time, the 20:80 mass ratio has been precisely optimized, ensuring that the slurry has sufficient solid content to form an effective coating while avoiding excessively high solid content that would lead to excessively high slurry viscosity and difficulty in coating, thus balancing the "coating thickness requirement" and the "coating feasibility".

[0078] For step S200, a gravure roller coating method is selected to meet the requirement of a "thin and uniform" coating thickness (6 / (ρ×10). -6 )~24 / (ρ×10 -6 The cell structure of the gravure roller (μm) allows for precise control of the slurry transfer amount, ensuring uniform coating thickness and avoiding localized weak protection (such as insufficient thickness failing to block lithium dendrites) or performance interference (such as excessive thickness hindering ion transport) caused by uneven coating. At the same time, the coating pressure and speed of the gravure roller can be flexibly adjusted to adapt to the morphology of the electrode sheet coated with positive electrode active material, avoiding damage to the structural integrity of the positive electrode active material layer during the coating process. Furthermore, the coating slurry can closely adhere to the surface of the active material layer, forming a strong interfacial bond, which provides a guarantee for the structural stability after subsequent drying and rolling.

[0079] For step S300, the drying process can completely remove moisture from the slurry, preventing residual moisture from causing side reactions inside the battery (such as electrolyte decomposition and electrode corrosion). At the same time, it promotes the initial bonding effect of the fixative, allowing the components to initially form a film. The subsequent rolling process can further improve the density and bonding strength of the coating, ensuring that the coating adheres tightly to the positive electrode active material layer without the risk of peeling. It can also optimize the internal structure of the coating, allowing the insulating material to form a dense skeleton, the conductive additives to be more evenly distributed, and the thermally conductive additives to build a continuous thermally conductive path. This avoids the mechanical strength of the coating from being affected by excessively large internal pores, or functional failure due to a loose structure. The two processes work together to ensure that the coating remains intact and stable during the volume expansion / contraction of the electrode sheet in long-term charge-discharge cycles, without peeling or cracking.

[0080] Thirdly, this application provides a battery including the aforementioned electrode sheet, as well as a negative electrode sheet, a separator, an electrolyte, a battery casing, and a connector. Since the battery includes the aforementioned electrode sheet, it possesses all the beneficial effects of the aforementioned electrode sheet; and since the electrode sheet is prepared with a lithium dendrite-responsive coating, the battery possesses all the beneficial effects of the aforementioned lithium dendrite-responsive coating.

[0081] Fourthly, this application provides a method for applying a lithium dendrite-responsive coating, which uses a battery management system to monitor the battery containing the aforementioned lithium dendrite-responsive coating to determine whether the following fault conditions occur:

[0082] (1) Under static conditions, the difference between the monitored rate of battery voltage drop and the average rate of drop of other batteries in the same module is >0.010V / 1h;

[0083] (2) The battery voltage experiences a sudden drop with an instantaneous rate of decrease >10mV / s;

[0084] (3) When charging to the 3.3V~3.4V range, the difference between the average voltage plateau of other batteries in the same module and the battery voltage plateau is >20mV;

[0085] (4) The difference between the monitored battery body temperature and the average temperature of other batteries in the same module is >5℃;

[0086] When any one of the above conditions is met, a level one warning for lithium dendrite formation is triggered; when any two or more of the above conditions are met, it is determined that the battery has experienced an internal short circuit fault caused by lithium dendrite formation.

[0087] In this embodiment, three quantitative fault conditions are designed for different stages of lithium dendrite puncture (initial micro-short circuit, mid-term signal enhancement, and charging characteristics): rapid voltage drop in a static state (>0.010V / 1h), instantaneous voltage drop (>10mV / s), and low charging platform (>20mV). This covers all operating conditions, including battery rest and charging / discharging, and quantifies fault characteristics with specific values, avoiding missed judgments (such as ignoring weak micro-short circuit signals) or misjudgments (such as classifying normal voltage fluctuations as faults) caused by the "qualitative ambiguity" of traditional monitoring. The indicator design is precisely matched with the "weak short circuit signal" of the coating: the micro-short circuit formed in the early stage of lithium dendrite puncture will cause a slow voltage drop or instantaneous fluctuation, and the voltage platform will be low due to the internal conductive path during charging. The three conditions capture fault signals from different dimensions, ensuring the accuracy of early identification.

[0088] When issuing fault warnings, a tiered warning logic is adopted. Specifically, it follows a tiered logic of "Level 1 warning (meeting any one of the above conditions) - Fault confirmation (meeting any two or more of the above conditions)". This avoids the overreaction of "single signal triggering emergency handling" (such as accidental triggering leading to battery module shutdown), while also enabling early risk prediction through Level 1 warnings and pinpointing the actual fault through fault confirmation, forming a complete closed loop of "warning-confirmation-intervention". Compared to the passive response of existing technologies that "short circuit equals failure", this tiered mechanism can issue warnings in the early stage when lithium dendrites have just pierced the coating and have not yet formed a hard short circuit. After fault confirmation, timely intervention measures such as isolation and cooling are taken to completely block the chain reaction of "micro-short circuit → heat accumulation → hard short circuit → thermal runaway", allowing sufficient time for energy storage system fault handling and significantly reducing the risk of accident spread.

[0089] In summary, the above-mentioned application method, through the design of "quantitative indicators - hierarchical early warning - synergistic coating - easy integration", upgrades the monitoring of internal short circuits of lithium dendrites from "passive response" to "active prediction", completely solving the problems of lag and accuracy of traditional monitoring methods. It forms a technical closed loop with lithium dendrite response coating and electrode sheets, comprehensively improving the safety protection level and practical application value of secondary battery energy storage systems.

[0090] The technical solution of this application will be illustrated below through specific embodiments and comparative examples.

[0091] Example 1:

[0092] Step 1: Preparation of lithium dendrite-responsive coating slurry

[0093] 1. Confirm the composition ratio of the lithium dendrite response coating: The lithium dendrite response coating consists of the following components by mass percentage: hollow porous heat-resistant insulating material 55%, fixative 38%, conductivity modifier 2%, thermal conductivity enhancer 4%, and dispersant 1%;

[0094] 2. Confirm the specific selection and corresponding parameters of each of the above-mentioned component materials:

[0095] Hollow porous temperature-resistant insulating material: made of silica powder with an average particle size of 0.5μm, possessing excellent temperature resistance, insulation and porous structure;

[0096] Fixative: Polyacrylic acid is selected to firmly bond the functional components into a film;

[0097] Conductivity regulating agent: It is a compound system of particulate and fibrous materials with a mass ratio of 2:1; the particulate conductivity regulating agent is conductive graphite with an average particle size of 0.05μm; the fibrous conductivity regulating agent is vapor-grown carbon fiber with an average diameter of 200nm and a length of 3μm.

[0098] Thermal conductivity enhancement agent: Boron nitride particles with an average diameter of 500 nm are selected, which have both high thermal conductivity and insulation properties;

[0099] Dispersing agent: Sodium polyacrylate is selected to promote uniform dispersion of the components.

[0100] 3. Slurry preparation:

[0101] All components of the above lithium dendrite-responsive coating are mixed with water at a mass ratio of 20:80 and stirred thoroughly to form a uniformly dispersed coating slurry.

[0102] Step 2: Preparing the electrode sheet

[0103] 1. Select an aluminum foil with a thickness of 13μm as the positive current collector, and uniformly coat both sides of it with lithium iron phosphate positive active material to form the electrode body; use a gravure roller coating process to uniformly coat the above-prepared coating slurry onto the surface of the active material of the electrode body to obtain an electrode with a lithium dendrite response coating pre-coated on the surface.

[0104] 2. The pre-coated electrode sheet is dried (to remove moisture from the slurry) and then rolled to ensure that the coating and the active material layer are tightly bonded and the density meets the standard, finally obtaining an electrode sheet (positive electrode) with a lithium dendrite response coating on the surface.

[0105] Tests showed that the resistivity ρ of the lithium dendrite-responsive coating on the electrode surface was 3.0 × 10⁻⁶. 6 Ω·m, according to the thickness calculation formula (thickness = 8 / (ρ×10) -6 The actual coating thickness is 2.67μm; the coating puncture strength is 2000gf, which meets the mechanical strength requirements for blocking lithium dendrite puncture.

[0106] Step 3: Battery fabrication

[0107] 1. The electrode sheet (positive electrode) prepared above is die-cut and then combined with the negative electrode sheet (using artificial graphite material), separator, electrolyte, battery casing and connectors;

[0108] 2. The die-cut electrode sheets (positive electrode), separator, and negative electrode sheets are wound / stacked in sequence to form a battery cell;

[0109] 3. The battery cells are installed into a square aluminum shell and then go through a series of processes including assembly, baking (to remove internal moisture), electrolyte injection, formation (to activate the battery cells), and capacity testing (to calibrate the capacity) to finally produce a 280Ah lithium iron phosphate battery with a square aluminum shell.

[0110] A battery management system (BMS) is used to monitor the batteries prepared above in real time, and a graded judgment is made based on the following fault conditions:

[0111] Early warning and fault judgment criteria:

[0112] A level 1 warning for lithium dendrite formation is triggered when any one of the following conditions is met:

[0113] (1) Under static conditions, the voltage drop rate of this battery is >0.010V / 1h faster than the average drop rate of other batteries in the same module;

[0114] (2) The battery voltage experiences a sudden drop of >10mV / s;

[0115] (3) When charged to the 3.3V~3.4V range, the voltage plateau of this battery is >20mV lower than the average voltage plateau of other batteries in the same module;

[0116] (4) The monitored battery body temperature is more than 5°C lower than the average temperature of other batteries in the same module;

[0117] When any two or more of the above conditions are met, it is determined that the battery has an internal short circuit fault caused by lithium dendrites.

[0118] Intervention logic: After triggering the first-level warning, the BMS prompts for risk investigation; after confirming the internal short circuit fault, it immediately initiates intervention measures such as battery isolation and cooling to prevent the spread of thermal runaway.

[0119] Example 2:

[0120] The only difference was that the hollow porous heat-resistant insulating material of the lithium dendrite-responsive coating in Example 1 was replaced with 50% titanium oxide and 50% sodium X-type molecular sieve (13X molecular sieve). The remaining steps and materials were the same as in Example 1 above, and the battery was thus prepared.

[0121] Example 3:

[0122] The only difference was that the thermal conductivity-enhancing agent in the lithium dendrite-responsive coating of Example 1 was replaced with aluminum nitride. The remaining steps and materials were the same as in Example 1, and a battery was thus prepared.

[0123] Example 4:

[0124] The only difference was that the conductivity-regulating agent in the lithium dendrite-responsive coating of Example 1 was replaced with Ketjen black and carbon nanotubes. The remaining steps and materials were the same as in Example 1, and a battery was thus prepared.

[0125] Example 5:

[0126] The only difference was that the fixative material in the lithium dendrite-responsive coating of Example 1 was replaced with polymethyl methacrylate. The remaining steps and materials were the same as in Example 1, and a battery was thus prepared.

[0127] The following are comparative examples used for comparison experiments with the embodiments:

[0128] Comparative Example 1:

[0129] The thickness of the lithium dendrite-responsive coating in Example 1 was adjusted to 1.5 μm. The remaining steps and materials were the same as in Example 1, thus obtaining Comparative Battery 1.

[0130] Comparative Example 2:

[0131] The composition ratio of the lithium dendrite-responsive coating in Example 1 was adjusted to: 85% hollow porous heat-resistant insulating material, 8% fixative, 2% conductivity modifier, 4% thermal conductivity enhancer, and 1% dispersant (after adjustment, the coating puncture strength is 550 gf, and the resistivity ρ is 2.0 × 10⁻⁶). 9 (Ω·m). The remaining steps and materials are the same as in Example 1 above, thus obtaining Comparative Battery 2.

[0132] Comparative Example 3:

[0133] The composition ratio of the lithium dendrite-responsive coating in Example 1 was adjusted to: 20% hollow porous heat-resistant insulating material, 73% fixative, 2% conductivity modifier, 4% thermal conductivity enhancer, and 1% dispersant (after adjustment, the coating puncture strength is 4500 gf, and the resistivity ρ is 2.0 × 10⁻⁶). 8 (Ω·m). The remaining steps and materials are the same as in Example 1 above, thus obtaining Comparative Battery 3.

[0134] Comparative Example 4:

[0135] By simply replacing the conductivity modulator of the lithium dendrite-responsive coating in Example 1 with a single particulate conductivity modulator (i.e., without adding the fibrous conductivity modulator, only retaining the original particulate conductive graphite), the resistivity ρ of the adjusted lithium dendrite-responsive coating is 2.0 × 10⁻⁶.8 Ω·m. The remaining steps and materials are the same as in Example 1 above, thus obtaining Comparative Battery 4.

[0136] Comparative Example 5:

[0137] By simply replacing the conductivity modifier of the lithium dendrite-responsive coating in Example 1 with a single fibrous conductivity modifier (i.e., without adding particulate conductivity modifiers, only retaining the original fibrous vapor-grown carbon fibers), the resistivity ρ of the adjusted lithium dendrite-responsive coating is 1.0 × 10⁻⁶. 5 Ω·m. The remaining steps and materials are the same as in Example 1 above, thus obtaining Comparative Battery 5.

[0138] Comparative Example 6:

[0139] Only the lithium dendrite-responsive coating of Example 1 was not used with thermal conductivity enhancers (the mass percentages of the remaining components remained unchanged, and the total percentage was naturally made up to 100% by other components). The remaining steps and materials were the same as in Example 1 above, thus obtaining Comparative Battery 6.

[0140] Comparative Example 7:

[0141] In the electrode preparation process of Example 1, the lithium dendrite-responsive coating was not applied. The remaining steps and materials were the same as in Example 1, resulting in the comparative battery 7.

[0142] The batteries of the above embodiments and the comparative batteries of the comparative examples were tested, and the corresponding test data and results were obtained. The specific tests are as follows:

[0143] I. Battery cycle performance and energy efficiency testing:

[0144] Step 1: Let the battery stand at 25°C for 30 minutes, discharge it to 2.5V at 0.5P, and let it stand at 25°C for 30 minutes.

[0145] Step 2: Charge the battery to 3.65V at a constant power of 0.5P, let it stand at 25℃ for 30 minutes, then discharge it to 2.5V at a constant power of 0.5P, and let it stand at 25℃ for 30 minutes. Repeat Step 2 for 1000 cycles, and record the battery's capacity retention rate and energy efficiency after 1000 cycles.

[0146] The capacity retention rate CR (%) after n battery cycles = discharge capacity of the nth cycle / discharge capacity of the first cycle × 100%.

[0147] In the above tests, the batteries in Examples 1 to 5 were tested sequentially to obtain the cycle performance and energy efficiency data of the batteries in each example; then the comparative batteries in Comparative Examples 1 to 7 were tested sequentially to obtain the cycle performance and energy efficiency data of the comparative batteries in each comparative example.

[0148] II. Battery Internal Short Circuit Performance Test

[0149] This test aims to compare and verify the internal short-circuit resistance, BMS warning sensitivity, and thermal runaway protection effect of the example and comparative batteries by standardizing the triggering of lithium dendrite formation. The specific test plan is as follows:

[0150] 1. Test Object

[0151] The batteries from Examples 1 to 5 and the comparative batteries from Comparative Examples 1 to 7 were used as test samples in sequence. Each test sample was made into a separate test module (to ensure that the test environment of the examples and the comparative examples is consistent and there is no cross-interference).

[0152] 2. Test Preparation (Only defect handling is added; the rest follow the steps of the corresponding implementation / comparative examples)

[0153] For each test sample (including the example and comparative batteries), the following defect treatment was added to its core preparation stage (the remaining preparation steps fully followed the process requirements of the corresponding example / comparative example): On the surface of the negative electrode sheet at the center of the core, about 1 cm² of negative electrode active material (artificial graphite) was precisely wiped off to expose the negative electrode copper foil (to create a "weak point" for lithium deposition, simulating a local defect scenario of the electrode sheet); After the defect treatment was completed, the complete battery was made according to the subsequent process (assembly, baking, liquid injection, formation, capacity testing) of the corresponding example / comparative example, and assembled into an independent test module. Each module was equipped with a battery management system (BMS) with uniform parameters.

[0154] 3. Testing Conditions and Procedures

[0155] (1) Place all test modules in a high and low temperature test chamber, set the ambient temperature to -30℃, and let stand for 2 hours until the battery temperature is consistent with the environment; (2) Cycle charge and discharge at 3C rate: charge to 3.65V (constant voltage cutoff current 0.05C), stand for 10 minutes, then discharge at 3C rate to 2.5V, stand for 10 minutes, and repeat the cycle; (3) BMS monitors battery voltage and body temperature in real time (sampling frequency 1 time / second), and thermocouples collect temperature data synchronously and record continuously; (4) Test termination conditions: ① Battery thermal runaway (temperature rise >20℃ / min or smoke, bulging); ② BMS confirms lithium dendrite internal short circuit fault; ③ Automatic termination if the above conditions do not occur after 1000 consecutive cycles.

[0156] 4. Fault determination criteria (precisely corresponding to the application method of this application)

[0157] Symptom 1: When the battery is stationary, the monitored rate of voltage drop is >0.010V / 1h faster than the average rate of drop in a blank module of the same type (a battery module with no defective design);

[0158] Symptom 2: A sudden drop in battery voltage of >10mV / s;

[0159] Symptom 3: When charging to the 3.3V~3.4V range, the monitored battery voltage plateau is >20mV lower than the average voltage plateau of similar blank modules;

[0160] Symptom 4: The monitored battery body temperature is more than 5°C lower than the average temperature of similar blank modules;

[0161] Judgment rules: Meeting any one of the symptoms triggers a Level 1 warning; meeting any two or more symptoms confirms the occurrence of a lithium dendrite internal short circuit fault.

[0162] For the two sets of experiments mentioned above, the following key data were recorded for each test sample:

[0163] (1) Cyclic performance: 1000-cycle capacity retention rate (%); (2) Energy efficiency: 1000-cycle energy efficiency (%); (3) Internal short circuit protection effect: whether thermal runaway occurs and appearance status (valve opening / smoke); (4) BMS response performance: whether it responds to faults and confirms the combination of fault symptoms.

[0164] The specific data and details are shown in the table below:

[0165] Table 1:

[0166]

[0167] Based on the test results of the above embodiments and comparative examples, the following analysis is conducted:

[0168] 1. Key compatibility of coating thickness (Example 1 vs. Comparative Example 1)

[0169] Comparative Example 1 reduced the coating thickness to 1.5 μm (lower than 2.67 μm in Example 1). Although the BMS could detect fault signs, thermal runaway still eventually occurred. The core reason is that insufficient coating thickness not only weakens the mechanical support of the physical barrier against lithium dendrites, but also results in an incomplete continuous thermal conduction pathway constructed by the thermal conductivity enhancement agent. After lithium dendrite puncture caused a micro-short circuit, local Joule heat could not diffuse rapidly through the coating, and the heat accumulation rate far exceeded the heat dissipation rate, eventually exceeding the battery thermal safety threshold and causing irreversible thermal runaway. This confirms the coating thickness formula of this application (thickness = 8 / (ρ×10)). -6The scientific nature of the process, and the precise matching of thickness and resistivity, are the foundation for achieving "cold treatment of faults".

[0170] 2. The balance effect of hollow porous heat-resistant insulating material content (Example 1 vs. Comparative Examples 2 and 3)

[0171] In Comparative Example 2, the hollow porous heat-resistant insulating material accounted for 85% (far exceeding the 55% in Example 1), resulting in a coating puncture strength of only 550 gf (far lower than the 2000 gf in Example 1). After lithium dendrites formed, the loose coating skeleton could not withstand the puncturing impact of the lithium dendrites and was directly penetrated, causing a hard short circuit in the positive and negative electrode active materials, instantly triggering thermal runaway. This indicates that excessive insulating material will damage the coating's density and mechanical strength, losing its core protective function of "physical barrier".

[0172] In Comparative Example 3, the insulating material accounted for only 20% (far lower than the 55% in Example 1). Although the puncture strength was increased to 4500 gf, the ion transport channels provided by the insulating material were severely insufficient, resulting in a battery cycle retention rate of only 87.3% and an energy efficiency of 89.2% after 1000 cycles (significantly lower than the ≥95% of the Example 1). Simultaneously, the insufficient insulating material led to a higher overall resistivity of the coating (2.0 × 10⁻⁶). 8 When lithium dendrites penetrate (Ω·m), a weak short-circuit signal with appropriate strength cannot be formed, and the BMS fails to respond to the warning. This confirms that an insulation material content of around 55% represents the optimal balance range between mechanical strength, ion transport, and signal conduction.

[0173] 3. The necessity of compounding conductivity regulating agents (Example 1 vs. Comparative Examples 4 and 5)

[0174] This application uses a "granular + fibrous" compound conductive additive (mass ratio 2:1), which is key to achieving "accurate fault signal capture" and "low interference under normal operating conditions":

[0175] Comparative Example 4 uses only particulate conductive additives and lacks the "linear conductive skeleton" of fibrous additives. The conductive sites of the coating are scattered and have poor connectivity, which leads to a significant decrease in battery energy efficiency (87.1%) and cycle life (82.5% retention rate). Furthermore, it cannot form an effective short-circuit signal through lithium dendrite bridging, and the BMS does not respond.

[0176] Comparative Example 5 used only a fibrous conductive additive. Its high conductivity reduced the coating resistivity, but the excessive micro-short-circuit current during lithium dendrite puncture caused rapid Joule heat accumulation, exceeding the heat dissipation capacity and triggering thermal runaway. This demonstrates that a single type of conductive additive cannot balance "signal sensitivity" and "heat control," while the compound system, through a "point-line interwoven" conductive network, achieves the functional requirements of "non-conductive under normal conditions and accurate signal transmission under fault conditions."

[0177] 4. The Indispensability of Thermal Conductivity Enhancers (Example 1 vs. Comparative Example 6)

[0178] In Comparative Example 6, without the addition of thermal conductivity enhancers, the coating's thermal conductivity decreased significantly. After lithium dendrites triggered a micro-short circuit, the locally generated Joule heat could not be quickly dissipated through the coating. The heat continued to accumulate and conduct to the inside of the battery cell, ultimately triggering a chain reaction of electrolyte decomposition and electrode aging, leading to thermal runaway. This highlights the core role of thermal conductivity enhancers (boron nitride, aluminum nitride, etc.)—collaborating with insulating materials and conductive additives to construct a "heat dissipation pathway," rapidly dissipating localized heat at the fault point, allowing time for intervention measures after BMS warnings, and breaking the conduction chain of "micro-short circuit → heat accumulation → thermal runaway."

[0179] 5. The core value of lithium dendrite-responsive coatings (Example 1 vs. Comparative Example 7)

[0180] In Comparative Example 7, without the lithium dendrite-responsive coating, lithium dendrites can directly puncture the separator, triggering a hard short circuit between the positive and negative electrodes. The thermal runaway latency is extremely short (without any physical obstruction or signal buffering), and the battery has already opened its valve and started smoking before the BMS has even detected any abnormal voltage / temperature signals. This contrasts sharply with Example 1: the coating, through a triple synergy of "physical obstruction (insulating material) - signal triggering (compound conductive additive) - heat dissipation (thermal conductive additive)," not only slows down the escalation of the fault but also provides the BMS with a monitorable characteristic signal, completely solving the pain points of traditional batteries: "rapid thermal runaway and difficult early warning."

[0181] In summary, the test data from Examples 1 to 5 clearly demonstrate that within the scope of protection of this patent application (coating component ratio, material selection, and structural design adaptation), all batteries exhibited a 1000-cycle capacity retention rate ≥95.0% and an energy efficiency ≥95.1%, and no thermal runaway occurred during internal short-circuit testing. The BMS can accurately respond to faults through specific symptom combinations. This result fully proves that the lithium dendrite-responsive coating designed in this application has minimal impact on the battery's internal resistance and long-term stability—the core reason being that the hollow porous temperature-resistant insulating material used in the coating (such as a silicon oxide and titanium oxide-13X molecular sieve composite system) possesses a rich and uniform microporous structure. This structure provides a continuous and unobstructed transport channel for lithium-ion migration, avoiding a surge in ion transport resistance, and through synergistic effects with other components, ensures the reversibility of the battery's charging and discharging process, achieving a win-win situation of "safety protection" and "electrical performance maintenance."

[0182] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0183] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A lithium dendrite responsive coating, characterized in that, include: Hollow porous heat-resistant insulating material is used to resist lithium dendrite puncture of the diaphragm to block short circuits between the positive and negative electrodes; Conductivity regulating agent is used to regulate the conductivity of the lithium dendrite response coating so that a short circuit signal is formed after the lithium dendrite is punctured. The conductivity regulating agent includes particulate conductivity regulating agent and fibrous conductivity regulating agent, and the mass ratio of the two is (1~5):

1. Thermal conductivity enhancers are used to dissipate heat from micro-short-circuit regions; Dispersing agents; Fixative; The hollow porous heat-resistant insulating material comprises 40-70% by mass, the fixative comprises 20-50% by mass, the conductivity regulating agent comprises 0.5-10% by mass, the thermal conductivity enhancing agent comprises 0.5-10% by mass, and the dispersing agent comprises 0.5-2% by mass; the lithium dendrite-responsive coating has a puncture strength of 1000-10000 gf and a resistivity ρ in the range of 2.0 × 10⁻⁶ gf / ρ. 5 ~1.5×10 8 Ω·m, thickness is 6 / (ρ×10 -6 )~24 / (ρ×10 -6 )μm.

2. The lithium dendrite-responsive coating of claim 1, wherein, The hollow porous heat-resistant insulating material is one or more of the following: alumina, boehmite, silicon dioxide, titanium dioxide, magnesium oxide, gibbsite, hydrotalcite, calcium sulfate, magnesium silicate, calcium silicate, molecular sieve, and oxide solid electrolyte. The average particle size of the hollow porous heat-resistant insulating material ranges from 0.05 to 1 μm, the specific surface area is greater than 10 to 600 m² / g, and the average pore size is 0.5 to 2 nm.

3. The lithium dendrite-responsive coating as described in claim 1, characterized in that, The particulate conductivity regulating agent includes one or more of the following: charcoal, coke, activated carbon, fullerene, carbon black, acetylene black, Ketjen black, conductive graphite, and super conductive carbon black. The average particle size of the particulate conductivity regulating agent ranges from 0.03 to 0.3 μm.

4. The lithium dendrite-responsive coating as described in claim 1, characterized in that, The fibrous conductivity regulating agent includes one or more of carbon nanotubes, vapor-grown carbon fibers, and graphite fibers. The average diameter of the fibrous conductivity regulating agent ranges from 3 nm to 300 nm, and the average length ranges from 1 to 20 μm.

5. The lithium dendrite-responsive coating as described in claim 1, characterized in that, The thermal conductivity enhancing agent is one or more of boron nitride, aluminum nitride, graphene microplates, and silicon carbide, with an average diameter ranging from 100 nm to 1000 nm.

6. The lithium dendrite-responsive coating as described in claim 1, characterized in that, The dispersing agent is one or a combination of lithium polyacrylate, sodium polyacrylate, and ammonium polyacrylate.

7. The lithium dendrite-responsive coating as described in claim 1, characterized in that, The fixative is polyvinylidene fluoride, polyvinyl alcohol, polyvinyl butyral, or polyvinylidene fluoride. Hexafluoropropylene), sodium alginate, lithium alginate, polymethacrylic acid, polyacrylic acid, polyacrylic acid copolymer, vinylidene fluoride The copolymer of hexafluoropropylene, polyacrylate, polymethyl methacrylate, polyamide, polytetrafluoroethylene, polyhexafluoropropylene, acrylic acid, polyacrylonitrile, carboxymethyl chitosan, polyethylene oxide, and styrene-butadiene rubber are one or more of the following:

8. A method for preparing an electrode sheet, characterized in that, The preparation of the lithium dendrite-responsive coating using any one of claims 1 to 7 includes the following steps: S100, the materials of the lithium dendrite-responsive coating are mixed with water at a mass ratio of 20:80 to form a coating slurry; S200: Select a first electrode sheet with a positive electrode active material coated on its surface, and use a gravure roller to coat the surface of the first electrode sheet with a coating slurry to obtain a second electrode sheet with a pre-coated coating slurry on its surface. S300, the second electrode sheet is dried and then rolled to obtain an electrode sheet with a lithium dendrite response coating on its surface.

9. A battery, characterized in that, It includes the electrode sheet as described in claim 8 above, as well as the negative electrode sheet, separator, electrolyte, battery casing and connector.

10. A method for applying a lithium dendrite-responsive coating, characterized in that, A battery management system is used to monitor the battery containing the lithium dendrite-responsive coating as described in any one of claims 1 to 7 to determine whether the following fault conditions occur: (1) Under static conditions, the difference between the monitored rate of battery voltage drop and the average rate of drop of other batteries in the same module is >0.010V / 1h; (2) The battery voltage experiences a sudden drop with an instantaneous rate of decrease >10mV / s; (3) When charging to the 3.3V~3.4V range, the difference between the average voltage plateau of other batteries in the same module and the battery voltage plateau is >20mV; (4) The difference between the monitored battery body temperature and the average temperature of other batteries in the same module is >5℃; When any one of the above conditions is met, a level one warning for lithium dendrite formation is triggered; when any two or more of the above conditions are met, it is determined that the battery has experienced an internal short circuit fault caused by lithium dendrite formation.

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