Lithium battery with double safety mechanisms of microdefect self-repairing and short-circuit fault self-isolation and preparation method of lithium battery

Abstract

The invention discloses a safe lithium battery structure with dual intrinsic intelligent thermal runaway protection capability and a preparation method thereof. According to the structure, two intrinsic response systems of behavior response particles and a sub-battery boundary fusing mechanism are fused, and system self-consistent protection of battery microdefect self-repairing and macroscopic short-circuit fault physical isolation is achieved. An electric field singular point is used as a targeted target, behavior response particles are driven by an electric field to directionally migrate to a microdefect position, precursor liquid is released, a protective film is generated in situ, and the formation and evolution process of endogenous short circuit is effectively inhibited. When strong internal short-circuit current appears, the focusing effect of the strong internal short-circuit current triggers boundary fusing of the faulty sub-battery and enables the thermosensitive conductive agent to be invalid, so that physical isolation of the faulty sub-battery is realized, and a thermal runaway chain is blocked. The system does not depend on an external controller and a sensor, depends on intrinsic intelligence of materials, and can remarkably improve the safety and fault tolerance of the lithium battery and prolong the service life of the lithium battery. The method is compatible with an existing lithium battery production line and has low-cost mass production capacity.

Description

Technical Field

[0001] This invention relates to the field of lithium-based battery safety protection technology, and in particular to an active intervention battery structure with dual intrinsic response capability. It is applicable to various types of lithium batteries (including lithium-ion batteries and lithium metal batteries) that use liquid, solid and semi-solid electrolyte systems. It has the ability to dynamically identify, intervene and cut off internal short circuit behavior during battery operation, thereby effectively preventing thermal runaway and significantly improving the safety, stability and service life of the battery system. Background Technology

[0002] With the widespread application of high-energy-density lithium batteries in electric transportation, energy storage systems, and consumer electronics, their potential safety risks are attracting increasing attention, especially thermal runaway events. Once triggered, these events are often accompanied by rapid temperature increases, gas release, fires, and even explosions, posing a serious threat to the safety of end-user equipment and personnel. Research shows that almost all cases of thermal runaway can be traced back to internal short circuits within the battery, and their mechanisms can be divided into two categories: endogenous short circuits and invasive short circuits.

[0003] Endogenous short circuits originate from the gradual evolution of microscopic defects during normal battery operation, typically involving three stages: induction, nucleation, and growth. For example, in liquid electrolyte systems, factors such as negative electrode material degradation, lithium deposition, and rupture of the solid electrolyte interphase (SEI) film can induce lithium dendrite growth. Once these dendrites pierce the separator, they cause a short circuit by connecting the positive and negative electrodes. In solid electrolyte systems, microstructural defects such as grain boundaries and pores can create local electric field singularities, inducing lithium ion deposition and gradually building penetrating short-circuit channels. Intrusive short circuits, on the other hand, originate from external disturbances or manufacturing defects, including mechanical impacts, foreign object residues, and high-temperature melt-through of the separator. These typically trigger a strong short-circuit current without warning and instantly cause a violent thermal runaway reaction. Once thermal runaway occurs, it can lead to a chain reaction of drastic battery temperature increases, rapid gas release, fire, and even explosion. Its destructive power is sufficient to destroy the entire battery system or even the entire terminal equipment, seriously endangering the safety of personnel and equipment. Especially in lithium metal batteries, the thermal runaway process is more violent and uncontrollable due to the extremely high reactivity of the negative electrode, resulting in even greater harm.

[0004] Existing lithium battery safety protection solutions mainly include: 1) Battery Management System (BMS): Its shortcomings are that it relies on external signal monitoring, which makes it slow to react to abnormalities inside the battery cell and unable to detect and respond to internal short circuits in a timely manner. 2) Material modification schemes: such as coating the surface of the separator or electrode with ceramics, or adding flame retardants to the electrolyte or separator, can improve the heat resistance of the battery to a certain extent, but still cannot get rid of the limitations of static and passive protection, and lack the ability to actively identify the defect evolution process.

[0005] In recent years, research on lithium battery safety technology has gradually shifted towards constructing material-responsive protection mechanisms, attempting to suppress thermal runaway through the intelligent behavior of the materials themselves. For example, thermally triggered microcapsule structures release flame retardants under high-temperature conditions, or voltage-triggered conductive tomography structures are designed to interrupt short-circuit current paths during voltage drops. While these strategies have played a role in improving battery safety, some key technological shortcomings remain, such as: 1) The response mechanism relies on global variables (such as temperature and voltage), has a high trigger threshold, and is difficult to accurately identify local defects inside the battery cell; 2) Thermal triggering response has a significant lag, often starting only after thermal runaway has entered the acceleration phase, making it impossible to achieve early intervention; 3) Voltage changes are not sensitive to internal short circuits, especially in the early stages of a short circuit when the voltage remains at a normal level, making it difficult for the protection mechanism to intervene in a timely manner; 4) The overall protection logic is still passive, lacking intrinsic response capabilities at the material level, and cannot build a truly closed-loop security system.

[0006] Therefore, there is an urgent need to develop an intelligent protection system with intrinsic material response capabilities that can intervene in a timely manner at the initiation stage of intrinsic short circuits and quickly isolate faults when macroscopic short circuits occur. This would drive the leap of lithium battery safety technology from "static defense" to "dynamic pre-intervention" and provide a highly reliable systematic safety solution for the next generation of lithium batteries. Summary of the Invention

[0007] This invention constructs a dual safety mechanism consisting of a "behavioral response particle dynamic self-repair system" and a "faulty sub-cell self-isolation system." The former is used to eliminate the initiation of endogenous short circuits, while the latter is used to address the risk of macroscopic strong short circuits. Working together, the two can achieve proactive intervention and prevention of thermal runaway, significantly improving the safety, fault tolerance, and lifespan of lithium battery systems.

[0008] 1 - Behavioral Response Particle Dynamic Self-Healing System

[0009] Endogenous short circuits typically originate from microscopic physical defects commonly found inside lithium batteries, such as SEI film cracks, solid electrolyte crystal defects, and lithium dendrite tips. Due to their geometric sharpness or structural discontinuities, these defects generate localized electric field enhancements at their locations, forming so-called "electric field singularities." These become the natural target and response signal for the behavioral response particles of this invention.

[0010] The behaviorally responsive particles consist of a shell constructed from a high-dielectric-responsive composite material (such as PVDF-HFP@TiO2) and an encapsulated "precursor liquid" within it. The precursor liquid contains cationic Li. + With Hf 4+ Anion F - With Cl - The water molecules released from the hydrate, along with the hydrolysis byproduct HF and process residues (water-acetonitrile), are products of the hydrolysis and dissolution reaction between the electrolyte lithium salt LiPF6 and the hydrated inorganic hafnium salt HfOCl2•8H2O in the water-acetonitrile solvent during particle encapsulation. Representative reactions are as follows: LiPF6 hydrolysis reaction: LiPF6 + H2O → Li + + F - + POF3↑ + 2HF Dissolution process of HfOCl2•8H2O: HfOCl2•8H2O → Hf 4+ + 2Cl - + 8H2O The particle shell possesses a high degree of electric field-induced polarization capability, enabling it to form a stable induced dipole moment in a non-uniform electric field. Driven by "dielectric force," it migrates along the electric field gradient direction to the electric field singularity region, i.e., the surface of microscopic defects. When the particle shell senses an electric field gradient in this region exceeding its set response threshold, it undergoes dielectric deformation and cracks, releasing the internally encapsulated pre-container liquid.

[0011] The particle response threshold is one of the core technical parameters of this invention. Its main function is to allow the particle shell to open and release the pre-encapsulated liquid during the battery charging phase (i.e., during lithium dendrite growth) to achieve in-situ sealing of microscopic defects; while during the battery discharging phase (i.e., during dendrite degradation), it ensures that the particle shell remains closed to avoid interfering with the rounding process of the dendrite tips. To achieve this selective response, the particle response threshold must be set at an appropriate level. Strictly speaking, the response threshold should be defined in units of local electric field gradient. However, if the background electric field strength is constant and the particle size distribution is narrow, a linear proportional relationship between the local electric field gradient and the local electric field strength can be derived. Therefore, for ease of engineering implementation and parameter calibration, this invention uses electric field strength to define the particle response threshold.

[0012] The intensity, spatial distribution, and periodic variations of the local electric field inside a lithium battery are closely related to the presence and evolution of microscopic defects. For example, during charging, the dendrite tip, due to its geometric sharpness, results in a much higher local electric field intensity than the surrounding area, forming an electric field singularity. Lithium ions preferentially migrate to the dendrite tip under the induction of this strong electric field, and after gaining electrons, are reduced to lithium atoms and deposited, promoting continuous dendrite growth. At the very tip of the dendrite, there are always fresh lithium atoms driven by the electric field. These atoms have not yet formed lattice coordination, are in a high free energy, and are unstable, rapidly diffusing into the stable, coordinated lattice below to reduce their own free energy. However, because the lithium ion concentration in the tip region remains consistently high, new "dynamic atomic protrusions" are continuously generated at the dendrite tip—temporary protrusions composed of uncoordinated lithium atoms. These protrusions keep the radius of curvature of the dendrite tip close to the lithium atom scale (approximately 0.2–0.5 nm), such as... Figure 1 As shown in Figure 1-a, when charging stops, the electric driving force disappears, the ion cloud at the dendrite tip dissipates rapidly, the "dynamic atomic protrusions" degenerate quickly due to the loss of lithium ion supply, and the radius of curvature of the dendrite tip returns to a thermodynamically stable state, typically within the range of tens of nanometers, as shown in Figure 1-b.

[0013] During the discharge cycle, lithium atoms at the dendrite tips are preferentially oxidized to lithium ions (Li₂) due to their higher free energy. + ), and migrate to the positive electrode, causing the dendrite tip to be gradually consumed and rounded (e.g. Figure 1 (as shown in -c). Electron microscopy observations show that the radius of curvature at the dendrite tip can increase to hundreds of nanometers at this stage, and the local electric field enhancement effect is significantly weakened.

[0014] The local electric field intensity E_sgl (singularity electric field intensity) at the micro-defect exhibits an exponential increasing trend as the curvature of the defect tip decreases, and can be estimated using the spherical head electric field enhancement model:

[0015] Where V is the voltage (set to 3.7V), r is the radius of curvature of the defect, and d is the distance between the electrodes (set to 100μm).

[0016] For a given battery, E_sgl is a univariate function of r. The calculation results of Equation 1 are shown in Figure 2. The results clearly show the trend of the singularity electric field intensity as a function of the radius of curvature at the defect tip. It can be seen that the singularity electric field intensity is typically about 1-2 orders of magnitude higher during the charging cycle than during the discharging cycle. This intensity difference enables the particle system to achieve "selective precursor release": when the response threshold is set to approximately 4 x 10⁻⁶. 7At V / m, the particle shell can open and release the precursor during the charging cycle to suppress dendrite growth; while during the discharging cycle, because the tip electric field strength is much lower than the response threshold, the particles remain in a quiescent state and do not affect dendrite degradation or the normal discharge process of the battery.

[0017] Since the electric field strength is also affected by factors such as battery structure, voltage, and electrolyte type, the above-mentioned response threshold is only for reference. The actual value should be calibrated and adjusted based on experimental data. The particle response threshold can be matched with the external electric field strength by changing the particle shell material ratio. Specific methods include adjusting the fluorine content of the PVDF-HFP polymer, introducing a polymer matrix with dynamic coordination ability, or adjusting the amount of TiO2 added to change the stress concentration state of the shell.

[0018] When the external electric field strength exceeds the particle shell's response threshold, the shell undergoes dielectric deformation, ruptures, and releases its internally encapsulated pre-formant liquid. This liquid then undergoes a series of reactions in the electric field: 1) The acetonitrile component in the precursor liquid is diluted, causing the water molecules to regain activity and break down under the induction of the electric field, producing hydroxide ions: H₂O → H₂O + + OH - ; 2) Hafnium ions (Hf) in the precursor liquid 4+ ) and hydroxide ions (OH) - A coordination reaction occurs, forming hafnium hydroxyl clusters: Hf 4+ + xOH - → [Hf(OH) x ] (4-x)+ Where x = 2 or 3, the specific value depends on the active OH groups in the system. - Concentration effect; 3) Active OH - It is an OH group capable of participating in the formation of hafnium hydroxyl clusters. - The concentration of lithium ions is determined by both the local electric field strength and the lithium ion concentration. The stronger the electric field, the more water molecules break down, and the higher the concentration of OH- ions. - The more there are, the greater the quantity. And Li + The higher the density, the more OH - With Li + Composition of lithium hydrogen oxygen clusters ([Li k OH] + The greater the probability of loss of activity (k>1), the higher the chance of inactivity. This is because the positive electrode of the battery releases a large amount of Li... + Most OH - The ions will form [Li] with it. k OH] +Clustering leads to loss of activity, resulting in the OH groups involved in coordination. - The quantity decreases. Therefore, [Hf(OH)] x ] (4-x)+ In this case, x is usually less than 4 and is positively charged; 4) Anions F in the precursor liquid - Li released from the positive electrode of a large number of batteries + The surrounding structure tends to form multi-lithium coordinated cluster structures [Li] j F] + , where j>1; 5) The above-mentioned functional ion clusters ([Li j F] + [Hf(OH)] x ] (4-x)+ and [Li k OH] + Driven by the "electric field force", they migrate to regions with enhanced electric field strength, such as SEI film cracks, lithium dendrite tips or solid electrolyte crystal defects. The electric field line aggregation effect causes the clusters to undergo spatial compression during migration, increasing the density of functional ion clusters and thus enhancing their ability to precipitate in situ on the defect surface. 6) Upon contact with the negatively charged defect surface, the aforementioned ion clusters undergo a series of further reactions: a) [Li j F] + Li disintegrates after accepting electrons. + It is reduced to atoms, but leaves behind a Li atom. + With F - LiF:Li is generated on the defect surface. + + F - → LiF↓; b) [Li k OH] + Li disintegrates after accepting electrons. + Reduced to atoms, OH - Released; active OH - Increasing the concentration leads to [Hf(OH)] x ] (4-x)+ Further hydrolysis occurs to form saturated hydroxyl clusters Hf(OH)4; c) Hf(OH)4 undergoes a dehydration condensation precipitation reaction to form hafnium oxide HfO2 with a high dielectric constant on the defect surface. The reaction formula is: Hf(OH)4 → HfO2↓ + 2H2O; 7) Finally, a lithium fluoride (LiF) and hafnium oxide (HfO2) composite protective film is formed on the defect surface, which can prevent electron penetration and passivate the electric field singularity. This film can effectively seal SEI cracks and inhibit dendrite growth, reduce the early evolution rate of endogenous short circuits, and thus effectively extend battery life. As shown in Figure 3, the formation of this protective film goes through a series of steps: "precursor liquid release → functional ion cluster formation → cluster migration-compression → cluster disintegration → in-situ precipitation".

[0019] Regarding the HF and Cl in the precursor liquid not mentioned above - While these components may enhance the stability of the cluster structure through hydrogen bonding or electrostatic adsorption, and migrate to the surface of microscopic defects via ion dragging under an electric field, they do not directly participate in the formation of the main product in the film-forming reaction; therefore, they can be considered auxiliary components in the reaction system. It is worth noting that HF ​​may dissociate during migration, releasing F... - This indirectly participates in the in-situ deposition process of LiF, and has a synergistic promoting effect on the formation of the protective film.

[0020] The aforementioned behaviorally responsive particle system is applicable to liquid, semi-solid, and solid electrolyte systems. In liquid and semi-solid systems, particles can be deployed on the side of the separator near the negative electrode via physical adsorption, spraying, or printing. In solid systems, particles can be deployed in a flexible interlayer between the solid electrolyte and the negative electrode via in-situ curing or interfacial embedding. This interlayer is an elastic polymer film with a thickness of 100–3000 nanometers, based on a PEO–PVDF-HFP copolymer, and doped with micro-water-regulating segments, dielectric-enhancing particles, and ion-conducting agents.

[0021] By deploying a sufficient number of behavioral response particles, they are made to respond sequentially when different electric field singularities are generated. Since the response sequence of particles is influenced by factors such as their spatial location, electric field distribution, and response threshold, typically only a small number of particles initiate release behavior within a specific period, while the rest remain in a pending state. This enables a system-level multi-round release-like dynamic response capability.

[0022] The aforementioned flexible interlayer can be prepared using solution casting. Specifically, PEO (polyethylene oxide), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer), and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) are dissolved in a mixed solvent composed of acetonitrile, acetone, or DMF at a mass ratio of 0.35:0.65:0.10. Then, appropriate amounts of optional additives (such as micro-water, SiO2, plasticizers, etc.) are added. The mixture is stirred at 40–60°C until a uniform and transparent solution is obtained. The solution is then poured onto a glass plate or Teflon template, and the solvent is evaporated in a constant temperature drying oven to form a flexible film.

[0023] The aforementioned behaviorally responsive particles can be prepared using various conventional microparticle assembly pathways, such as dual-emulsion induction, interfacial deposition and solidification, microencapsulation, or Pickering emulsion-assisted methods, to form microparticles with core-shell structure characteristics, enabling electric field sensing and directional migration. Different preparation techniques have their own advantages in particle size control, structural uniformity, and material compatibility, and can be flexibly selected according to the actual system requirements.

[0024] Four technical parameters affecting the performance of "behavioral response particles" and their control methods: 1) Electric field response sensitivity: This can be achieved by adjusting the relative permittivity and polarizability of the particle shell material. For example, compared to PVDF-HFP@TiO2 (ε... r ≈ 50–100), using PVDF-HFP@BaTiO3 (ε r (≈ 100–1000) can further improve the particle's ability to sense electric field gradients. Furthermore, optimization of particle size, surface charge distribution, and shell thickness also significantly affects the response threshold; 2) Directional migration capability: The dielectrophoretic driving effect can be enhanced by controlling particle size, shell thickness, surface functional asymmetry, and the viscosity and dielectric constant of the medium. Asymmetric particles with a Janus structure can further improve the particle's orientation sensing ability and migration stability in non-uniform electric fields; 3) Formation rate and thickness of in-situ reaction membrane: The thickness and density of the membrane can be controlled by adjusting the composition of the precursor liquid, the pH value and water content of the electrolyte environment, as well as the intensity and duration of the electric field induction. 4) Enhance the compatibility between particles and battery interface materials: Polar groups (such as –OH, –COOH, etc.) can be introduced on the surface of the shell. At the same time, the stability and integration quality of particles in different systems can be improved by using spraying, in-situ curing, interface embedding and other placement methods.

[0025] It should be noted that in the actual trial production process, the above key process parameters need to be determined and optimized through repeated experimental feedback.

[0026] 2 - Faulty Sub-Battery Self-Isolation System

[0027] If the aforementioned microscopic protection mechanisms fail to effectively curb the evolution of internal short-circuit faults, subsequent events such as lithium dendrite membrane puncture and solid electrolyte lithium plating bridging may occur, causing the endogenous short circuit to enter a growth phase. Both endogenous short circuits in the growth phase and invasive short circuits caused by external forces will trigger strong internal short-circuit currents in the battery and bring the risk of thermal runaway. The second protection mechanism provided by this invention, namely the faulty sub-cell self-isolation system, can identify and locate sub-cells exhibiting strong short-circuit currents in real time and accurately isolate them. This not only effectively blocks the thermal runaway evolution chain but also allows the entire battery to escape the short-circuit path and resume normal operation, thereby significantly improving system safety and battery lifespan.

[0028] The faulty sub-cell self-isolation system consists of multiple sub-cell units disposed on the positive electrode foil of the battery. Each sub-cell unit consists of a region defined by the boundary of a cell-like pattern constructed on the surface of the positive electrode current collector and a positive electrode active material containing a thermosensitive conductive agent coated on the surface of that region. Each sub-cell has the same geometry, size, and independent electrochemical function, and can be physically isolated from the overall battery through boundary melting.

[0029] The aforementioned cellular pattern boundary is a cell wall-like structure formed by a series of grooves or microporous bridges connected on the current collector surface using double-sided embossing (planar embossing or roll embossing) or laser drilling processes. This structure defines the boundaries of each sub-cell and has a resistivity much higher than that of the current collector itself. All sub-cells are connected in parallel through the current collector to form a single sub-cell pack, which participates in the charging and discharging process collaboratively under normal operating conditions, exhibiting overall performance equivalent to a conventional lithium battery cell. When any sub-cell experiences an internal short-circuit fault, its potential drops rapidly, causing surrounding sub-cells to discharge to the fault point through the current collector, forming an internal short-circuit current.

[0030] like Figure 4 The one-dimensional array sub-cell model shown has multiple sub-cells with the same internal resistance discharging to a short-circuit fault point through a current collector constructed with a microporous array (sub-cell boundary). The current intensity through the boundary of the sub-cell containing the short-circuit fault point (faulty sub-cell) can be written as:

[0031] in: n is the number of sub-cells arranged along a one-dimensional direction; E is the electromotive force of the sub-cell and the overall lithium battery; R is the internal resistance of the sub-cell (the internal resistance of all sub-cells is the same). r is the resistance of the internal short-circuit contact point; I_sub It is the internal short-circuit current output by a single sub-cell (the output current of all sub-cells is the same).

[0032] The internal short-circuit current intensities at the boundaries of the first, second, and nth adjacent sub-cells of the faulty sub-cell can be expressed as follows:

[0033] The results show that the intensity of the short-circuit current transmitted along the current collector is distance-dependent; the closer to the fault point, the greater the short-circuit current, exhibiting a focusing effect of the short-circuit current at the fault point. Therefore, the boundary current of the faulty sub-cell... I 0 represents the peak value of the short-circuit current within the system. Since the resistivity of the sub-cell boundary is much higher than that of the current collector body, the localized Joule heat generated by this peak current is sufficient to instantly melt the boundary of the faulty sub-cell. Similarly, this peak current will simultaneously flow through the thermosensitive conductive agent in the active material of the faulty sub-cell, generating sufficient Joule heat to render it non-conductive. Therefore, the conductive paths between the faulty sub-cell and other parts of the battery, including the current collector and the active material electrode layer, are severed, achieving physical isolation of the faulty sub-cell, completely terminating the short-circuit current conduction path, and blocking the subsequent thermal runaway evolution chain.

[0034] Therefore, the working principle of the "faulty sub-cell self-isolation system" proposed in this invention is as follows: First, the focusing effect of the short-circuit current at the short-circuit point is used to accurately locate the faulty sub-cell; then, the Joule thermal triggering fuse mechanism is activated to selectively fuse the sub-cell boundary and selectively remove the thermally sensitive conductive agent. As a result, the entire battery system prevents thermal runaway and restores the overall battery function at the cost of losing only the capacity of a local sub-cell, greatly improving the battery's safety, fault tolerance, and service life.

[0035] The boundary melting process of the sub-cell is extremely rapid and brief. The boundary is rapidly heated above the melting point of aluminum within a short time, generating a large number of molten aluminum droplets. However, as the short-circuit current is interrupted, the source of heat is also instantly removed, resulting in a very small total melting heat. Most of the boundary melting heat is carried to the surface of the positive electrode active particles by the sputtered molten aluminum droplets. There, a redox reaction occurs, reducing elements such as nickel, manganese, and cobalt in the active particles to metallic monomers and forming conductive metal bridges. Simultaneously, because the resulting interfacial compounds have very low interfacial energy, unreacted molten aluminum droplets can form a metallic aluminum film coating the surface of the positive electrode particles, ultimately leading to a short circuit and the failure of the positive electrode material.

[0036] To avoid the side effect of sub-cell boundary melting, this invention first fills the trenches or micropores of the sub-cell boundary with a certain oxide, such as silicon dioxide (SiO2), using a dip-coating or coating method before applying the active material to the positive electrode current collector. After drying and curing, the positive electrode active material is then applied. This process completely isolates the sub-cell boundary melting point from the positive electrode active particles by SiO2 particles. SiO2 has high electrochemical inertness and will not react with aluminum droplets or the electrolyte; its high surface energy causes the aluminum droplets to eventually solidify into isolated aluminum microspheres; and its much higher thermal efficiency than the electrolyte allows it to preferentially absorb most of the heat carried by the aluminum droplets, preventing the electrolyte penetrating into the particle gaps from being thermally decomposed. This ensures that neither the battery's active material nor the electrolyte is affected by sub-cell boundary melting. However, it should be noted that for boundaries formed by microporous bridges, since it is impossible to completely isolate the melting point from the positive electrode material, the performance of such batteries will be slightly affected by the melting of the sub-cell boundary. Therefore, trench structures should be used as sub-cell boundaries whenever possible.

[0037] To achieve the above technical solution, the present invention considers the following four key technical parameters.

[0038] 1) Sub-cell safe capacity (Q_sub) and safe area (A_sub) Based on experimental results, when the capacity of a single battery cell does not exceed 100mAh, its short-circuit behavior generally does not lead to thermal runaway. Therefore, in the sub-battery system defined in this invention, the safe capacity Q_sub of the sub-battery should satisfy: Q_sub = 100mAh / n (4) Where n represents the number of sub-cells that may short-circuit simultaneously in a single incident. For lithium batteries operating in static or quasi-static conditions, such as those used in 3C devices and grid energy storage, n = 1, because internal short-circuit faults in these batteries are typically confined to a single sub-cell. For electric vehicle power batteries, safety redundancy needs to consider the extreme scenario of the battery being completely punctured. Therefore, for laminated power batteries, n = 2L; for wound power batteries, n = 4L. Here, L is the number of laminated layers or the number of winding turns.

[0039] The relationship between the safe area and safe capacity of a sub-cell is: A_sub = Q_sub / Q_a, where Q_a is the "capacity per unit area of ​​the electrode".

[0040] 2) Sub-cell boundary fusing current density (J_fuse) To ensure that the fuse-breaking behavior is both responsive and avoids false triggering, this invention sets the "boundary fuse-breaking current density" threshold J_fuse to ζ times the battery's maximum design operating current density J_max, that is: J_fuse = ζ•J_max (5) Among them, ζ>1 is the empirical safety factor, the specific value of which is determined by the "system current impact tolerance" and the thermal response characteristics of the electrode material.

[0041] 3) Sub-cell boundary geometry optimization The sub-cell boundary is formed by a regularly distributed array of high-resistivity double-sided imprinted trenches or microporous bridges on the current collector, which can provide sufficient Joule heat to melt itself under short-circuit current. This can be achieved by adjusting the thickness of the bottom of the double-sided imprinted trenches (i.e., the imprinting depth) or changing the width of the microporous bridges (see...). Figure 5 It can adjust the resistivity and thermal fusing performance of the sub-cell boundary to precisely match the boundary current density threshold J_fuse and the fusing response time.

[0042] Double-sided embossing offers advantages such as low cost, good consistency, and minimal impact on the current collector's mechanical properties, making it suitable for large-scale mass production. Laser drilling, on the other hand, offers high flexibility and is suitable for pilot production phases.

[0043] The cell pattern of the sub-cell can be any polygon that can fill a planar space, including but not limited to triangles, rectangles or rhombuses. A honeycomb hexagonal structure is preferred because it has the least impact on the mechanical properties of the current collector while ensuring structural uniformity.

[0044] If microporous bridges are selected as the boundaries of sub-cell cells, it is recommended to use microporous bridges composed of equally spaced circular micropores to minimize the impact on the tensile strength of the current collector.

[0045] 4) Selection of thermosensitive conductive agent Conductive agents are essential components of lithium-ion battery cathode materials, providing electron pathways for active particles. In this invention, traditional conductive agents are replaced by thermosensitive conductive agents, characterized by their ability to lose conductivity under the Joule heating generated by strong internal short-circuit currents, i.e., when the temperature reaches a set threshold (120–200°C). Various thermosensitive conductive agents are available, including pyrolytic carbon-based conductive agents, thermosensitive silver paste / conductive adhesives, and thermosensitive catalytic conductive agents.

[0046] In summary, this invention proposes a "dual protection mechanism" for lithium batteries. Through seamless collaboration between behaviorally responsive particles and the sub-battery system, it achieves full-process safety protection from the self-repair of an internal short circuit to the self-isolation of a faulty sub-battery. This mechanism aims to block the formation path of thermal runaway and effectively extend battery life. Figure 6 The working logic flow of this invention is vividly illustrated: 1) Behavioral response particles identify the location of microstructural defects inside the battery, such as SEI cracks, crystal defects, and lithium dendrites, through electric field singularity signals; 2) Driven by the dielectrophoretic force, particles migrate to the defect region; 3) When the electric field strength reaches the response threshold, the particle shell cracks, releasing the precursor liquid, which then gives rise to functional ion clusters; 4) Driven by the electric field, ion clusters migrate to the defect and generate a composite protective film in situ, thereby achieving electric field passivation and electronic blockade of the defect; 5) If successful, the behavioral response particle system returns to the monitoring state; if it fails or the system suffers intrusive damage, a strong internal short-circuit current is triggered. 6) The faulty sub-battery self-isolation system detects and locates the sub-battery experiencing a strong internal short-circuit current, and then physically isolates the faulty sub-battery through a boundary fuse mechanism; 7) Subsequently, the battery returned to normal operation, and the entire protection system also returned to monitoring mode.

[0047] This invention integrates a dual protection mechanism of microscopic repair and macroscopic isolation, possessing full-stack protection capabilities of active identification, precise response, and rapid escape, providing key technical guarantees for the safe application of high-energy lithium batteries. Technological advantages and application value

[0048] 1. Preventive Protection Against Thermal Runaway: This invention achieves preemptive intervention in the thermal runaway development chain of lithium batteries through the synergistic effect of microscopic defect self-repair and macroscopic fault self-isolation mechanisms. It can eliminate endogenous short circuits in their incipient stage and cut off the path of sudden intrusive short-circuit currents within millisecond response time, eliminating the triggering factors for thermal runaway at the source. This dual mechanism can effectively cope with thermal runaway events caused by various inducing factors such as mechanical abuse, thermal abuse, electrical abuse, manufacturing defects, performance aging, and system failure, exhibiting high adaptability and system resilience.

[0049] 2. Intrinsic Intelligent Response Capability: The behavioral response particles introduced in this invention target electric field singularities, enabling proactive detection, tracking, and repair of various microstructural defects in batteries (such as dendrites, SEI cracks, grain boundaries, and voids). Simultaneously, the introduced sub-cell structure utilizes the focusing effect of short-circuit current to instantly detect and melt down faulty sub-cell boundaries, achieving self-consistent system escape. All of the above response processes are triggered by the intrinsic behavior of the material, independent of external sensors or control logic, possessing intrinsic intelligent characteristics of "native recognition, autonomous response, and immediate handling," significantly improving the system's safety response speed and fault tolerance.

[0050] 3. Safety Assurance Based on "Healing": Traditional safety strategies often fail to repair faulty batteries. Once an internal short circuit or thermal runaway occurs, the only options are usually to replace the cells or battery pack, or even scrap the entire system. This invention proposes a novel design concept based on "healing," breaking away from traditional passive defense thinking: first, it eliminates endogenous short-circuit triggers through behavioral response particles; second, it rapidly isolates intrusive events through sub-battery pack structures; and finally, it restores the normal function of the overall battery, thus constructing a safety assurance system that prioritizes repair, relies on isolation, and is fundamentally based on healing. This strategy significantly improves the fault controllability and lifespan boundary of the battery system, providing a replicable and engineerable implementation path for building a new generation of highly reliable, long-life intelligent battery systems. More innovatively, this "repair" and "healing" behavior is entirely completed by the battery's intrinsic intelligence, requiring no external intervention.

[0051] 4. Broad Adaptability and Platform-Level Compatibility: The structural system proposed in this invention is applicable to various battery structures, including wound and stacked types, and supports the functional integration of liquid, semi-solid, and all-solid electrolyte systems, covering application needs from consumer-grade small-capacity cells to power-type large-module systems. It possesses excellent structural dimensional compatibility and system platform integration capabilities, making it suitable for building a multi-scenario safe battery family and possessing the potential for platform-based promotion.

[0052] 5. Process-friendly and low-cost mass production: The novel battery components involved in this invention—including current collectors with sub-cell boundaries, thermosensitive conductive agents, separators carrying behaviorally responsive particles, and flexible interlayers—can all be prepared using existing industry chain processes or have commercially available procurement channels. The overall structural design is highly compatible with current lithium battery manufacturing processes, requiring no significant modifications to production lines or additional investment in equipment. This enables product technology upgrades and system integration deployment, and allows for industrialization without affecting cost structure and production pace. Attached Figure Description

[0053] Figure 1 illustrates the evolution of the curvature of the micro-defect (dendritic) tip during different battery operating cycles: a) Charging cycle: dendrites gradually grow, and dynamic atomic protrusions are generated at the tip; b) Post-charge resting period: atomic protrusions disappear, and the dendritic structure tends to stabilize; c) Discharging cycle: dendrites degenerate, and the tip curvature becomes rounded.

[0054] Figure 2 shows the relationship between electric field strength and defect tip curvature, which can be divided into two target regions: a charging region and a discharging region. The pre-existing body release response threshold is set at the lower edge of the electric field strength in the charging region, i.e., 4x10. 7 V / m. In the charging zone, when the electric field strength exceeds the precursor release threshold, the particles are triggered and release the precursor liquid; in the discharging zone, when the electric field strength is below the above threshold, the particles remain in the off state and do not release the precursor.

[0055] Figure 3 shows the formation pathway of the LiF-HfO2 protective film: a) release of precursor liquid; b) formation of functional ion clusters; c) cluster migration-compression; d) cluster disintegration; e) in-situ precipitation.

[0056] Figure 4 is a schematic diagram of the current path of the lithium battery of the present invention under the condition of internal short circuit fault. It shows that multiple one-dimensional parallel sub-cells discharge to the internal short circuit fault point through the micro-hole connecting bridge (sub-cell boundary) on the current collector, and a current focusing phenomenon occurs at the short circuit point.

[0057] Figure 5 shows three types of sub-cell boundary (cross-sectional view): a) Circular groove type, prepared by imprinting process, r = radius of circular groove, b = thickness of opposite groove bottom; b) Trapezoidal groove type, prepared by imprinting process, w = groove bottom width, b = thickness of opposite groove bottom; c) Micro-hole bridge type, prepared by laser drilling process, b = width of micro-hole bridge.

[0058] Figure 6 is a flowchart of the working logic of the dual protection mechanism of the present invention: ① Behavioral response particles identify microstructural defects inside the battery through electric field singularity signals; ② Driven by dielectric force, the particles migrate to the defect region; ③ When the electric field strength reaches the response threshold, the particle shell cracks, releasing the precursor liquid, which then gives rise to functional ion clusters; ④ Driven by electric field force, the ion clusters migrate to the defect and generate a composite protective film in situ, performing electric field passivation and electronic blockade on the defect; ⑤ If successful, the behavioral response particle system returns to the monitoring state; if it fails or the system suffers invasive damage, a strong internal short-circuit current is triggered; ⑥ The faulty sub-battery self-isolation system detects and locates the sub-battery that has experienced a strong internal short-circuit current, and then physically isolates the faulty sub-battery from the system through a boundary fuse mechanism; ⑦ Subsequently, the battery resumes normal operation, and the entire protection system also returns to the monitoring mode.

[0059] Figure 7 shows a schematic diagram of the honeycomb structure double-sided imprinted circular groove sub-cell boundary on the positive electrode current collector foil of the 18650 safety type 3C lithium battery: a) honeycomb structure circular groove sub-cell boundary on the current collector foil; b) enlarged view of the sub-cell cell boundary.

[0060] Figure 8 shows a schematic diagram of the boundary of a rectangular sub-cell with microporous bridges on the positive electrode current collector foil of a 4680 safety-type power lithium battery: a) Along the length direction, 13 rows of micropores are evenly arranged at 5 mm intervals within the active electrode material, and multiple rows of micropores are arranged at 2.5 mm intervals along the width direction; b) Enlarged view of the sub-cell cell boundary.

[0061] Figure 9 is a schematic diagram of the boundary of the rectangular sub-cell with micro-hole bridge on the positive electrode current collector foil of BYD's blade-type power lithium battery: a) Nine rows of micro-holes are evenly distributed along the length direction, and multiple rows of micro-holes are arranged at 6mm intervals along the width direction; b) Enlarged view of the sub-cell boundary. Detailed Implementation

[0062] Behavioral response particle preparation and deployment process (applicable to Examples 1-3 below) The behaviorally responsive particles described in this embodiment are prepared using an "interface deposition method," with a particle size controlled between 1 and 5 micrometers. They possess high dielectric response, polarization migration, and electric field-induced release capabilities. The following description applies to all types of lithium-ion battery structures listed in Examples 1 to 3 of this specification.

[0063] I. Particle preparation method (interface deposition method) 1) Aqueous phase in the pre-treatment body: First, mix deionized water and acetonitrile (analytical grade) in a 1:1 ratio, stir well, and then add lithium salt pre-treatment LiPF6 per 10 ml. ６ Hydrated inorganic hafnium salt HfOCl ２ •8H ２ Add 0.1 mmol of each of O and stir magnetically for 15-30 minutes to form a stable and homogeneous in vivo aqueous phase liquid. 2) Particle shell oil phase: Add PVDF-HFP polymer to chloroform at a ratio of 1-3 g per 100 mL, and stir magnetically at room temperature for about 30 minutes until the polymer is completely dissolved. Then add anatase TiO2 with a particle size of 15-25 nm at 5-15 wt% of the PVDF-HFP polymer mass. ２ The nanofiller is ultrasonically dispersed for 5-10 minutes to obtain a homogeneous and stable composite solution. Finally, 0.5-2 wt% of the nonionic surfactant Span 80 is added, and the mixture is magnetically stirred for 10-15 minutes to form a particle shell oil phase. 3) Water-in-oil emulsion: Place the obtained particle shell oil phase in a high-speed shear emulsifier and start stirring (6000~8000 rpm). Slowly drop the pre-aqueous phase, which is 1 / 3 to 1 / 5 the volume of the particle shell oil phase, into the oil phase, controlling the dropping rate at 1~2 mL / min. Maintain a constant shear rate during the dropping process, and continue shearing for 2~5 minutes after the dropping is completed. 4) External aqueous phase: Prepare a 0.5~1 wt% PVA (polyvinyl alcohol) aqueous solution using deionized water, heat it to 50℃ and stir to fully dissolve the PVA, then cool it to room temperature for later use; 5) Interface Deposition and Particle Formation: Place the external aqueous phase, with a volume ratio of approximately 5-10 times that of the water-in-oil emulsion, into the emulsification reactor. Start stirring (300-500 rpm). Slowly add the water-in-oil emulsion dropwise to the external aqueous phase at a rate of 1-2 mL / min, maintaining stirring throughout the addition. After the addition is complete, gradually raise the temperature to 40-60℃ and maintain this temperature for 30-60 minutes while continuing stirring. During this stage, chloroform begins to evaporate, and PVDF-HFP and TiO₂... ２ A shell is formed by depositing on the surface of the aqueous droplets in the pre-concentrated body. After heating is complete, stirring is stopped, and the mixture is cooled to room temperature. 6) Particle Collection and Drying: The particles were washed 2-3 times by centrifugation (3000-5000 rpm, 5-10 minutes). After each washing, the particles were redispersed with deionized water, and the centrifugation was repeated. Finally, the precipitated particles were collected. The collected particles were vacuum dried at 40-50℃ for 12 hours to obtain particles with a diameter of 1-5 μm and a shell structure of PVDF-HFP@TiO. ２ The core is a shell-core type behaviorally responsive particle encapsulated with a precursor liquid. The particle possesses the ability to migrate and release in response to an electric field.

[0064] II. Particle Deployment Method and Location The behavior-responsive particle dry powder is evenly distributed on the surface of the battery separator near the negative electrode by sieving or dispersing liquid drop coating. The adhesion of the particles is enhanced by natural drying or low-pressure heat bonding. The cell pressing process further increases the adhesion of the particles on the separator. Specific Implementation

[0065] The technical solution of the present invention will be further described below with reference to specific embodiments. It should be understood that the embodiments are only used to illustrate the present invention and not to limit the scope of protection of the present invention.

[0066] Description of the battery assembly used in the specific embodiments: 1) The battery separators have all been processed by embedding the behavioral response particles described in claim 2 using the method described in claim 3. The specific preparation process and deployment method are all implemented in accordance with the aforementioned "preparation and deployment process of behavioral response particles"; 2) The positive electrode current collector foil has been modified using the method provided in claim 9, that is, using an imprinting process to construct trench-type sub-cell boundaries on the current collector foil, or using laser drilling technology to construct micro-bridge-type sub-cell boundaries; the oxide (SiO2) described in claims 12 and 13 is processed using the method described in claim 14. ２ The granular slurry is filled into the above-mentioned trenches and micropores, and the slurry is dried and cured before the conventional positive electrode active material coating operation is carried out. 3) The conductive agent in the traditional cathode material has been replaced with a pyrolytic carbon-based conductive agent in accordance with claims 9 and 16; 4) The remaining battery components will retain their existing structure.

[0067] Using the above-mentioned battery components, no modifications are required to the existing lithium battery manufacturing process and equipment to produce various types of safe lithium batteries with dual safety mechanisms of self-repair of micro-defects and self-isolation of short-circuit faults. The only thing to note is to ensure that the particles on the separator face the negative electrode.

[0068] The following describes three typical implementation schemes: 18650 safety type 3C lithium battery (wound cylindrical structure), 4680 safety type power lithium battery (wound cylindrical structure), and BYD blade safety type power lithium battery (stacked structure). 1) 18650 safety type 3C lithium battery (wound cylindrical structure)

[0069] The parameters of the 18650 lithium battery are as follows: Rated voltage: 3.7 V Battery capacity: 3400 mAh Charging current: 2C, 6.8 A PP (polypropylene) diaphragm: Length: Slightly longer than the electrode sheet Width: 60mm Behavioral response particles: deployed on the side facing the negative pole Aluminum foil positive current collector: Thickness: 10 µm Length: Total length 3250 mm, active material coating length 3100 mm Width: 50 mm Monopole: Sub-cell boundary: honeycomb structure, circular groove type.

[0070] Based on the above parameters, the "electrode unit area capacity" of this battery can be determined by the battery capacity (3400 mAh) and the electrode area (3100 cm²). ２ The calculation is as follows: Q_a = 3400 mAh / 3100 cm³ ２ ≈ 1.1 mAh / cm ２ Since this embodiment is designed for 3C devices, n=1, therefore the "safe capacity of the sub-battery" is Q_sub = 100 mAh. Accordingly, the "safe area of ​​the sub-battery" can be calculated using the following formula: A_sub = Q_sub / Q_a, substituting the values: A_sub = 90cm² ２ .

[0071] As shown in Figure 7, a honeycomb-structured circular trench sub-cell boundary with a side length of 1 cm was fabricated on an aluminum foil positive electrode current collector using an imprinting process. The sub-cell area is 2.6 cm². ２ This is much smaller than the sub-cell safety area A_sub = 90 cm². ２ It has sufficient safety redundancy. The entire electrode area is divided into 1192 sub-cells.

[0072] The maximum safe charging current linear density of the battery is J_max = 6.8 A / 50 mm = 0.136 A / mm. Assuming ζ = 11, the boundary fusing current density of the sub-cell is obtained as J_fuse = 1.5 A / mm.

[0073] According to finite element simulation results, when the linear current density on the current collector reaches J_fuse, and the radius of the groove circular cross-section is set to a circle with r = 50 micrometers, and the imprint depth is 3.9 micrometers, the boundary "melting time" is approximately 1000 milliseconds. If the current density increases to 15 A / mm, the melting time is shortened to 10 milliseconds. 2) 4680 safety-type power lithium battery (wound cylindrical structure)

[0074] The parameters of the 4680 lithium battery are as follows: Rated voltage: 3.7 V Battery capacity: 25000 mAh Maximum safe charging current: 4C, 100A PP (polypropylene) diaphragm: Length: Slightly longer than the electrode sheet Width: 80mm Behavioral response particles: deployed on the side facing the negative pole Aluminum foil positive current collector: Thickness: 15 µm Length: Total length 3270 mm, active material coating length: 2480 mm Width: Total width 76mm, active material coating width: 70mm Total pole: All pole Number of turns, L: 26 Sub-cell boundary: matrix microporous bridge type.

[0075] Based on the above parameters, the "electrode unit area capacity" of this battery can be determined by the battery capacity (25000 mAh) and the electrode area (3472 cm²). ２ The calculation is as follows: Q_a = 25000 mAh / 3472 cm⁻¹ ２ ≈ 7.2 mAh / cm ２.

[0076] Because this embodiment uses a wound cylindrical battery designed for electric vehicles, a single needle puncture impact can simultaneously cause short circuits in n = 4L = 104 sub-cells. The safe capacity of each sub-cell is Q_sub = 100 mAh / n = 0.96 mAh. Therefore, the safe area of ​​the sub-cell can be calculated using the following formula: A_sub = Q_sub / Q_a, substituting the values: A_sub = 0.133 cm² ２ .

[0077] As shown in Figure 8, the following micropore array structure is generated on the aluminum foil positive electrode current collector foil using laser drilling technology: Thirteen rows of micropores are uniformly arranged at 5 mm intervals along the length of the active electrode material. Multiple rows of micropores are arranged at equal intervals of 2.5 mm along the width direction; Sub-cell area = 0.125 cm² ２ < 0.133 cm ２ (Sub-cell safety area) has a certain safety redundancy; The electrode region is divided into 27,776 sub-cells.

[0078] The maximum fast-charging line current density of the battery is J_max = 100 A / 2480 mm = 0.04 A / mm. Assuming ζ = 30, the current density of the sub-cell boundary fuse line is obtained as J_fuse = 1.2 A / mm.

[0079] According to the finite element simulation results, when the linear current density on the current collector reaches J_fuse, and the microorifice is set to be circular (diameter = 0.1 mm) with a microorifice bridge width of b = 0.042 mm, the boundary fusing time is approximately 1000 milliseconds. If the current density increases to 12 A / mm, the fusing time is shortened to 10 milliseconds. 3) BYD Blade Safety Type Power Lithium Battery (Stacked Structure)

[0080] The technical parameters of BYD's blade battery are as follows: Rated voltage: 3.2 V Battery capacity: 135 Ah Battery fast charging current: 10C, 1350 A PP / PE / PP three-layer co-extruded separator: Length: Slightly longer than the electrode sheet Width: 85mm Behavioral response particles: deployed on the side facing the negative pole Aluminum foil positive current collector: Thickness: 12 µm Length: 945 mm Width: 83 mm Bipolar ear: Maximum safe charging current for the current collector: 1350 A / 26 / 2 = 26 A Number of floors, L: 26 Sub-cell boundary: matrix microporous bridge type.

[0081] Based on the above parameters, the electrode capacity per unit area of ​​the battery can be calculated as Q_a = 135000 mAh / 40786cm². ２ ≈ 3.3 mAh / cm ２ .

[0082] Because this embodiment is a stacked battery designed for electric vehicles, a single needle puncture impact can cause a maximum of n = 2L = 52 sub-cells to simultaneously experience internal short circuits. The safe capacity of each sub-cell is Q_sub = 100mAh / n = 1.92 mAh. Therefore, the safe area of ​​the sub-cell can be calculated using the following formula: A_sub = Q_sub / Q_a, substituting the values: A_sub = 0.58 cm² ２ .

[0083] As shown in Figure 9, the following micropore array was fabricated on the aluminum foil positive current collector foil using laser drilling technology: Nine rows of micropores are evenly distributed along the length direction. Multiple rows of micropores are arranged at equal intervals of 6 mm along the width direction. Sub-cell area = 0.5 cm² ２ < 0.58 cm ２ (Sub-cell safety area) has a certain safety redundancy. The electrode region was divided into 81,572 sub-cells.

[0084] The maximum safe charging current linear density of the battery is J_max = 26 A / 83 mm = 0.3 A / mm. Assuming ζ = 3.3, the current density of the sub-cell boundary fuse line is J_fuse = 1 A / mm.

[0085] According to the finite element simulation results, when the linear current density on the current collector reaches J_fuse, and the microorifice is set to be circular (diameter = 0.1 mm) with a microorifice bridge width of b = 0.042 mm, the boundary fusing time is approximately 1000 milliseconds. If the current density increases to 10 A / mm, the fusing time is shortened to 10 milliseconds.

[0086] In all the above embodiments, when the line current density at any part of the current collector exceeds the fusing threshold J_fuse, whether triggered by an internal or external short circuit, the fusing behavior at the sub-cell boundary can be triggered. However, there are mechanistic differences between the triggering location of the fusing response and the subsequent results: 1) When the triggering cause is an internal short circuit, the boundary of the faulty sub-cell will be fusing, the faulty sub-cell will be physically isolated, the sub-cell pack will complete self-repair, and the system will return to normal operation; 2) When the triggering cause is an external short circuit accompanied by BMS failure or lag, the sub-cell boundary near the tab will be concentratedly fusing, and the entire cell will be detached from the battery system. Appendix – Glossary of Terms

[0087] Intrinsic intelligence refers to the ability of a material or structure to identify, respond to, and repair itself without external controllers, sensors, or algorithms, relying on its own physical or chemical properties.

[0088] An endogenous short circuit refers to a short circuit path that is gradually induced by microstructural defects during the normal operation of a lithium battery, typically going through three stages: induction, nucleation, and growth.

[0089] An exogenous short circuit refers to a sudden short circuit caused by external disturbances or foreign objects. Common causes include residual conductive particles from manufacturing processes, electrode debris, mechanical punctures or compression, etc. It is usually accompanied by a strong instantaneous short circuit current and high heat release, and is an important cause of thermal runaway.

[0090] An electric field singularity refers to a localized region of high electric field strength formed by the focusing of electric field lines due to defects such as cracks, grain boundaries, or dendrites. Its electric field strength is much higher than the background electric field of the battery.

[0091] Behavior-Responsive Particles are functional microparticles with a core-shell structure that can migrate directionally to the electric field singularity region under the induction of an electric field and release the core precursor liquid to complete the repair of battery defects.

[0092] Dielectrophoretic force is the driving force acting on polarized particles in a non-uniform electric field, used to guide particles to defect regions.

[0093] Electric field force is the driving force that acts on charged particles in a uniform or non-uniform electric field. Its magnitude is related to the particle charge and the electric field strength.

[0094] A sub-cell is an independent electrochemical functional unit divided according to the cellular pattern boundary on the current collector surface. Each sub-cell has an independent electrode material distribution, current path and capacity control structure. They can be connected in parallel in the overall battery system to form a sub-cell pack, or they can be physically isolated from the overall battery by boundary melting.

[0095] The sub-cell boundary is a linear, high-resistivity cell wall-like structure formed by embossed grooves or microporous bridges on the current collector foil. It is used to separate independent sub-cells and achieve a fusible function.

[0096] A trench refers to a narrow, elongated recessed structure formed on the surface of a current collector by an imprinting process. It forms the cell wall-like structure at the boundary of a sub-cell and has a resistivity much higher than that of the current collector body, allowing it to be melted by high-density current.

[0097] Micropore bridges are connecting bridges between micropores generated on the surface of the current collector through laser drilling. They form cell wall-like structures at the boundaries of sub-cells and have a resistivity much higher than that of the current collector body, and can be melted by high-density current.

[0098] Boundary Fusing Current Density (J_fuse) refers to the threshold of line current density required to trigger the boundary fusing of a sub-cell, which is usually higher than the maximum design operating current density.

[0099] Thermo-Responsive Conductive Additives are materials whose conductivity decreases with increasing temperature. Above a threshold temperature, they lose conductivity, thereby blocking the electronic pathway of the positive electrode active material.

[0100] Sub-cell Safety Capacity (Q_sub) is the maximum electrical capacity that a sub-cell can withstand without causing thermal runaway in the battery system.

Claims

1. A lithium battery with a dual safety mechanism of self-repair of microscopic defects and self-isolation of short-circuit faults, characterized in that, This lithium battery structure includes two collaborative safety protection systems: a behavior-responsive particle dynamic self-healing system and a faulty sub-cell self-isolation system. These systems are used to dynamically repair microscopic defects in the battery and isolate short-circuit faults, achieving the dual goals of preventing battery thermal runaway and extending battery life. 1) A dynamic self-healing system of behavioral response particles, consisting of multiple sets of behavioral response particles deployed near the negative electrode of the battery. These particles achieve in-situ repair of microstructural defects induced by SEI film damage, solid electrolyte crystal defects, and electric field singularities induced by lithium dendrite tips, thereby effectively reducing the early evolution rate of endogenous short circuits; 2) The faulty sub-cell self-isolation system consists of multiple sub-cell units set on the positive electrode foil of the battery. When an internal short circuit fault occurs, the focusing effect of the short circuit current at the fault point melts the boundary of the faulty sub-cell, the short circuit current path is cut off, the risk of thermal runaway is eliminated, the faulty sub-cell is physically isolated, and the remaining sub-cell units in the battery can continue to operate normally.

2. The lithium battery structure according to claim 1, characterized in that, The behaviorally responsive particles have a shell-core structure: 1) Shell: Constructed of a composite material with high dielectric response, possessing the ability to induce polarization under an applied electric field. The preferred material for the shell is a composite system of polyvinylidene fluoride-hexafluoropropylene copolymer and titanium-based or barium titanium-based oxide particles, specifically PVDF-HFP@TiO2 or PVDF-HFP@BaTiO3; 2) Core: Composed of precursor liquid, which includes cationic component Li + and Hf 4+ Anionic component F - and Cl - The precursor liquid consists of water molecules released from hydrates, hydrolysis byproduct HF, and process residues (water-acetonitrile). The precursor liquid is generated from the electrolyte lithium salt LiPF6 and the hydrated inorganic hafnium salt HfOCl2•8H2O through hydrolysis and dissolution reactions in a water-acetonitrile mixed solution during particle encapsulation.

3. The lithium battery structure according to claim 1, characterized in that, The deployment method of the behavioral response particles is as follows: 1) In liquid electrolyte batteries, behavioral response particles are deployed on the surface of the battery separator near the negative electrode by means of physical adsorption, spraying or interface printing to ensure that the particles have the ability to sense changes in the electric field in the negative electrode area in real time. 2) In a solid electrolyte battery, the particles are arranged in a flexible interlayer between the solid electrolyte and the negative electrode by in-situ curing or interfacial embedding. The flexible interlayer is a composite film with a thickness of 100–3000 nanometers, using PEO–PVDF-HFP copolymer as the substrate and doped with micro-water control segments, dielectric reinforcing particles and ion conduction aids to give it suitable elasticity, ion conduction and electric field responsiveness. 3) The behavioral response particles are statistically distributed within the deployment area, and their response timing depends on the specific deployment location, electric field strength, and trigger threshold, exhibiting spatial and temporal diversity in response behavior. Therefore, only some particles are activated within any given electric field cycle, while the remaining particles remain in a standby state, thus achieving a phased response and a multi-round release-like effect.

4. The behavioral response particle according to claim 2, characterized in that, The housing has the following electric field response properties: 1) Under the action of a non-uniform electric field, the shell material can generate a significant polarization response and form a dipole moment structure. Driven by the dielectric force, the particles can migrate directionally along the electric field gradient to the target region where the electric field intensity changes abruptly, thereby realizing the active localization of the singularity of the defect-induced electric field. 2) The induced charge layer formed on the particle surface by the above polarization behavior can reconstruct the local electric field line distribution at its location and effectively passivate the high-intensity electric field, thereby suppressing the tendency of lithium ions to accumulate excessively in the defect region and reducing the risk of dendrite growth. 3) The casing is configured with an electric field response threshold, which matches the typical electric field strength at lithium dendrite tips or interface structural defects during a battery charging cycle. When the electric field strength of the environment in which the particles are located reaches or exceeds this threshold, the casing undergoes dielectric expansion deformation and ruptures after stress accumulation reaches a critical point, releasing the precursor liquid in the core. During a battery discharging cycle, because the electric field strength is much lower than the response threshold, the casing remains closed. This characteristic of the casing endows the behaviorally responsive particles with periodic selective response capabilities, enabling adaptive activation and suppression during the charging and discharging process.

5. The behavioral response particle according to claim 2, characterized in that, After the precursor liquid is released into the flexible interlayer between the liquid electrolyte or solid electrolyte and the negative electrode, functional cationic clusters are generated, including hafnium hydroxyl clusters ([Hf(OH)]). x ] (4-x)+ ), lithium fluorine clusters ([Li) j F] + ) and lithium hydrogen oxygen clusters ([Li k OH] + The number of positive charges carried by the clusters is determined by the number of lithium ions in the system. Under the action of an electric field, the clusters migrate toward the surface of the micro-defects. During the migration, the focusing effect of the electric field lines causes the clusters to be compressed in space, resulting in an increase in the local ion concentration.

6. The functional cationic cluster according to claim 5, characterized in that, After migrating to the surface of microscopic defects, the clusters undergo reduction reactions at their coordination centers, leading to cluster dissociation or recombination. Under the induction of high reactivity on the defect surface, a composite protective film of lithium fluoride (LiF) and hafnium oxide (HfO2) is generated in situ. This composite protective film possesses excellent electronic insulation and electric field passivation capabilities, effectively suppressing the initiation and growth of lithium dendrites.

7. The functional ion cluster according to claim 5, characterized in that, The microscopic defects include, but are not limited to, at least one of the following: (a) localized cracks in the solid electrolyte interphase (SEI) film; (b) lithium dendrite tips; and (c) crystal defects in the solid electrolyte.

8. The behavioral response particle according to claim 2, characterized in that, The behavioral response particles are manufactured using methods such as dual emulsion template method, interface deposition method, and Pickering emulsion-assisted assembly method, and have a particle size of 1–5 micrometers.

9. The lithium battery structure according to claim 1, characterized in that, The sub-cell unit comprises a region defined by the boundary of a cell-like pattern constructed on the surface of the positive electrode current collector and a positive electrode active material containing a thermosensitive conductive agent coated on the surface of that region, wherein: 1) The cell-like pattern boundary is a cell wall-like structure formed by connecting a series of grooves or microporous bridge arrays generated on the current collector by double-sided imprinting (planar imprinting or roll imprinting) or laser drilling process, which constitutes the sub-cell boundary; 2) Each sub-cell has the same geometry, size and independent electrochemical function, and can be physically isolated from the battery system through boundary melting; 3) The cell-like pattern can be selected from any polygon that can fill a planar space, including but not limited to triangles, rectangles or rhombuses, preferably honeycomb hexagons, in order to minimize the impact on the mechanical properties of the current collector; 4) When the sub-cell boundary is constructed using microporous bridges, it is preferable to use microporous bridges constructed of equally spaced circular micropores to reduce their impact on the mechanical strength of the current collector.

10. The sub-battery cell structure according to claim 9, characterized in that, The sub-cell boundary has a resistivity much higher than that of the current collector body, and can be melted when the current density exceeds its melting threshold J_fuse, thus achieving physical isolation between the faulty sub-cell and the adjacent sub-cell; the resistivity of the sub-cell boundary and its melting threshold J_fuse can be adjusted by changing the imprinting depth or the width of the micro-hole bridge.

11. The sub-battery cell structure according to claim 9, characterized in that, The current collector material is aluminum metal or aluminum-based alloy suitable for the electrochemical environment of lithium batteries, with a melting point not exceeding 660.3 °C, to ensure that the sub-cell boundary has controllable melting resistance under high current density.

12. The sub-battery cell structure according to claim 9, characterized in that, The grooves or micropores constituting the boundary of the sub-battery are filled with oxide nanospheres, which serve to: 1) physically prevent the aluminum liquid microspheres generated during the boundary melting process from sputtering onto the surface of the positive electrode active material; and 2) utilize their inherent high thermal diffusivity to quickly absorb the heat of boundary melting, thereby preventing the thermal decomposition of a small amount of electrolyte between particles.

13. The oxide nanospheres according to claim 12, wherein the preferred material is SiO2, and the preferred diameter is 0.1-1 micrometer.

14. The oxide nanospheres according to claim 12, characterized in that, The filling method involves using a dip-scraping or coating method to fill the grooves or micropores of the positive electrode current collector with a slurry containing oxide particles. After drying and curing, the positive electrode active material is then coated onto the current collector using conventional processes.

15. The sub-battery cell structure according to claim 9, characterized in that, The capacity of the sub-cell is determined by the area of ​​its cell pattern, and this area should be smaller than the preset sub-cell safety area (A_sub) to ensure that in the event of an internal short circuit fault, the released electrical energy is limited to the sub-cell safety capacity (Q_sub) to prevent thermal runaway of the entire lithium battery.

16. The sub-battery cell structure according to claim 9, characterized in that, The thermosensitive conductive agent can be selected from pyrolytic carbon-based conductive agents, thermosensitive silver paste conductive adhesives, or thermosensitive catalytic conductive agents, all of which have the characteristic of losing conductivity due to structural or chemical changes when the temperature reaches a preset response threshold (120–200 °C). In this invention, the heating source of the thermosensitive conductive agent is Joule heating generated by the internal short-circuit current flowing through it. This heat can heat the conductive agent to above the preset response threshold within a millisecond timescale, reducing its conductivity to below a predetermined failure value (<10). -4 (S / cm), thereby effectively cutting off the current path of the faulty sub-cell in the electrode layer.

17. The lithium battery structure according to claim 1, characterized in that, All the sub-battery units are connected in parallel via current collectors to form a single sub-battery pack, which has the following functional attributes: 1) Under normal operating conditions, the sub-battery pack has charge and discharge performance equivalent to that of a traditional lithium battery cell; 2) When an internal short circuit occurs, the short-circuit current focuses at the fault point within the faulty sub-cell. If this current density exceeds the sub-cell boundary fusing threshold J_fuse, the following fusing response mechanisms will be triggered sequentially: a) The faulty sub-cell boundary melts due to Joule heating, thus cutting off its current path on the current collector; b) The thermally conductive agent in the electrode layer of the faulty sub-cell heats up and loses its conductivity, thus cutting off its current path in the electrode layer; c) The above dual disconnection mechanism completely isolates the faulty sub-cell from the sub-cell group, while allowing the rest of the sub-cell group to continue operating normally. 3) When encountering abnormal operating conditions such as external short circuits, overcharging, or over-discharging, the current peak will appear in the tab area of ​​the cell. If the current density in the tab neighborhood exceeds J_fuse, the boundary of the sub-cell adjacent to the tab will fuse synchronously, causing the cell to be electrically disconnected from the battery pack, thereby preventing the fault from propagating to higher system levels. It should be noted that the above scenario of external short circuit causing tab area fuse will not be triggered under normal operation of the battery management system (BMS), and will only be automatically activated as a safety fallback strategy in extreme scenarios of BMS failure or delayed response.

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