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CN-122025836-A - Lithium battery with micro-defect self-repairing and short-circuit fault self-isolating dual safety mechanism and preparation method thereof

CN122025836ACN 122025836 ACN122025836 ACN 122025836ACN-122025836-A

Abstract

The invention discloses a safe lithium battery structure with dual intrinsic intelligent thermal runaway protection capability and a preparation method thereof. The structure integrates two sets of intrinsic response systems of behavior response particles and a sub-battery boundary fusing mechanism, and achieves self-consistent protection of a system for self-repairing of the battery microscopic defects and physical isolation of macroscopic short-circuit faults. And taking the electric field singular point as a targeting target, directionally transferring the behavior response particles to the microscopic defect under the drive of the electric field, releasing the precursor liquid and generating a protective film in situ, so that the formation and evolution progress of the endogenous short circuit are effectively prevented. When strong internal short circuit current occurs, the focusing effect triggers the boundary of the failed sub-battery to fuse and the thermosensitive conductive agent to fail, so that the physical isolation of the failed sub-battery is realized, and a thermal runaway chain is blocked. The system does not depend on an external controller and a sensor, and can obviously improve the safety, fault tolerance and service life of the lithium battery by means of intrinsic intelligence of materials. The invention is compatible with the existing production line of lithium batteries and has low cost and capacity.

Inventors

  • LIU WEIJIE
  • LIU MO

Assignees

  • 南京超凡精密机械制造有限公司

Dates

Publication Date
20260512
Application Date
20250917
Priority Date
20250811

Claims (17)

  1. 1. The lithium battery with the micro-defect self-repairing and short-circuit fault self-isolating dual safety mechanism is characterized in that the lithium battery structure comprises two safety protection systems which work cooperatively, namely a behavior response particle dynamic self-repairing system and a fault sub-battery self-isolating system, and is used for dynamically repairing the micro-defect of the battery and isolating the short-circuit fault, so that the dual aims of preventing the occurrence of thermal runaway of the battery and prolonging the service life of the battery are achieved: 1) The dynamic self-repairing system for behavior response particles consists of a plurality of groups of behavior response particles distributed near the cathode of the battery. The particles realize in-situ repair of the microstructure defects through identification and response of electric field singular points induced by SEI film breakage, solid electrolyte crystal defects and lithium dendrite tips, so that the early evolution rate of endogenous short circuits is effectively reduced; 2) The fault sub-battery self-isolation system is composed of a plurality of sub-battery units arranged on a battery positive electrode foil. When an internal short circuit fault occurs, the focusing effect of the short circuit current at the position of the fault point fuses the boundary of the faulty sub-battery, the short circuit current path is cut off, the risk of thermal runaway is relieved, the faulty sub-battery is physically isolated, and the rest sub-battery units in the battery can keep normal operation.
  2. 2. The lithium battery structure of claim 1, wherein the behavior-responsive particles have a shell-core structure: 1) The shell is made of a composite material with high dielectric response capability and has the property of inducing polarization under the action of an external electric field. The preferable material of the shell is a composite system of polyvinylidene fluoride-hexafluoropropylene copolymer and titanium-based or barium-titanium-based oxide particles, and specifically PVDF-HFP@TiO 2 or PVDF-HFP@BaTiO 3 ; 2) The inner core consists of a precursor liquid comprising the cationic components Li + and Hf 4+ , the anionic components F - and Cl - , and water molecules released by the hydrates, hydrolysis by-product HF and process residues (water-acetonitrile). The precursor liquid is formed by hydrolysis and dissolution reaction of electrolyte lithium salt LiPF 6 and hydrated inorganic hafnium salt HfOCl 2 •8H 2 O in a water-acetonitrile mixed solution in the particle encapsulation process.
  3. 3. The lithium battery structure of claim 1, wherein the behavior-responsive particles are arranged in a manner that: 1) In the liquid electrolyte battery, behavior response particles are distributed on the surface of one side of a battery diaphragm, which is close to a negative electrode, in a physical adsorption, spraying or interface printing mode, so that the particles have instant induction capability on the change of an electric field of a negative electrode area; 2) In a solid electrolyte battery, particles are arranged in a flexible intermediate layer between a solid electrolyte and a negative electrode in an in-situ solidification or interface embedding mode, the flexible intermediate layer is a composite material film with the thickness of 100-3000 nanometers, PEO-PVDF-HFP copolymer is selected as a base material, and a micro-water regulating chain segment, dielectric enhancement particles and ion conduction auxiliary agents are doped to endow the flexible intermediate layer with proper elasticity, ion conductivity and electric field responsiveness; 3) The behavior response particles are statistically distributed in the layout area, and the response time sequence of the behavior response particles depends on the differences of specific layout positions, electric field intensities and trigger thresholds, so that the spatial and temporal diversity of response behaviors is shown. Therefore, only part of particles are activated in any electric field period, and the rest of particles are in a standby state, so that the periodic response and the multi-round-like release effect are realized.
  4. 4. The behavior-responsive particle of claim 2, wherein the shell has the following electric field response properties: 1) Under the action of a non-uniform electric field, the shell material can generate obvious polarization response and form a dipole moment structure, and under the drive of dielectrophoresis force, particles can directionally migrate to a target area with abrupt change of electric field strength along the gradient of the electric field, so that active positioning of defect-induced electric field singular points is realized; 2) The induced charge layer formed by the polarization on the particle surface can reconstruct the local electric field line distribution of the position where the induced charge layer is positioned, and effectively passivate the high-strength electric field, so that the local excessive aggregation trend of lithium ions in a defect area is inhibited, and the dendrite growth risk is reduced; 3) The housing is configured with an electric field response threshold that matches the typical electric field strength at lithium dendrite tips or interface structure defects during a battery charging cycle. When the intensity of the environmental electric field where the particles are located reaches or exceeds the set threshold, the shell is subjected to dielectric expansion deformation, and breaks after the stress accumulation reaches a critical point, so that the precursor liquid in the core is released. During the battery discharge period, the housing remains closed because the electric field strength is well below the response threshold. This feature of the shell imparts a periodic selective response capability to the behavior-responsive particles, enabling them to achieve adaptive activation and suppression during charge and discharge.
  5. 5. The behavior-responsive particle of claim 2, wherein after the precursor liquid is released into the liquid electrolyte or the flexible intermediate layer between the solid electrolyte and the negative electrode, functional cation clusters are generated, the clusters including hafnium hydroxyl clusters ([ Hf (OH) x ] (4-x)+ ), lithium fluorine clusters ([ Li j F] + ), and lithium hydroxyl clusters ([ Li k OH] + ), the number of which carry positive charges being determined by the number of lithium ions in the system. The clusters migrate to the surface of the microscopic defect under the action of electric field force, and in the migration process, the clusters are compressed in space due to the electric field line focusing effect, so that the local ion concentration is increased.
  6. 6. The functional cationic clusters according to claim 5, wherein after the clusters migrate to the surface of the microscopic defect, the coordination center of the clusters receives electrons to undergo a reduction reaction, so that the cluster structure is dissociated or recombined, and a lithium fluoride (LiF) and hafnium oxide (HfO 2 ) composite protective film is generated in situ under the induction of high reactivity of the defect surface. The composite protective film has excellent electronic insulation and electric field passivation capability, and can effectively inhibit the sprouting and growth of lithium dendrites.
  7. 7. The functional ion clusters of claim 5, wherein the microscopic defects include at least one of (a) localized breach of solid electrolyte interface film (SEI), (b) lithium dendrite tips, and (c) crystal defects in solid electrolyte.
  8. 8. The behavior-responsive particles of claim 2, wherein the behavior-responsive particles are produced by a double emulsion templating method, an interfacial deposition method, a Pickering emulsion assisted assembly method, or the like, having a particle size of 1-5 microns.
  9. 9. The lithium battery structure according to claim 1, wherein the sub-battery cell is composed of a region defined by a cell pattern boundary constructed on a surface of the positive electrode current collector and a positive electrode active material containing a heat-sensitive conductive agent applied to the surface of the region, wherein: 1) The cell pattern boundary is a cell wall structure formed by connecting a series of grooves or micro-pore bridge arrays generated on a current collector by a double-sided embossing (plane embossing or rolling embossing) process or a laser drilling process, so as to form a 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 by boundary fusing; 3) The cell pattern may be selected from any polygon that can fill a planar space, including but not limited to triangular, rectangular, or diamond, preferably honeycomb hexagonal, to minimize impact on the mechanical properties of the current collector; 4) When the subcell boundaries are formed using microbore bridges, it is preferable to use microbore bridges formed of equally spaced circular micropores to reduce its impact on the mechanical strength of the current collector.
  10. 10. The subcell structure of claim 9, wherein the subcell boundary has a resistivity substantially higher than the current collector body and is fusible when the current density exceeds its fuse threshold j_fuse to achieve physical isolation of the failed subcell from adjacent subcells, wherein the subcell boundary resistivity and its fuse threshold j_fuse are adjustable by varying the embossing depth or the microbridge width.
  11. 11. The subcell structure of claim 9 wherein the current collector material is aluminum metal or aluminum-based alloy suitable for use in lithium battery electrochemical environments and has a melting point no greater than 660.3 ℃ to ensure controlled fusing of subcell boundaries under high current density.
  12. 12. The subcell structure according to claim 9, wherein the grooves or micropores forming the boundary of the subcell are filled with oxide nanosphere particles, which function to 1) physically block the aluminum liquid microspheres generated during boundary fusing from being sputtered onto the surface of the positive electrode active material, and 2) rapidly absorb the boundary fusing heat by utilizing the inherent high thermal diffusivity property thereof so as to avoid a small amount of electrolyte between the particles from being thermally decomposed.
  13. 13. Oxide nanosphere particles according to claim 12, preferably of SiO 2 , preferably having a diameter of 0.1-1 micron.
  14. 14. The oxide nanosphere particles according to claim 12, wherein the filling method is to fill slurry containing oxide particles into grooves or micropores of a positive electrode current collector by using a dipping or scraping method, and then to coat a positive electrode active material on the current collector by a conventional process after drying and solidification.
  15. 15. The subcell structure according to claim 9, wherein the capacity of the subcell is determined by the area of the cell pattern and the area should be smaller than the predetermined subcell safety area (a_sub) to ensure that the electrical energy released by the subcell is limited to the subcell safety capacity (q_sub) upon occurrence of an internal short circuit failure, thereby preventing thermal runaway of the entire lithium battery.
  16. 16. The subcell structure according to claim 9, wherein the thermally sensitive conductive agent is selected from the group consisting of a pyrolytic carbon-based conductive agent, a thermally sensitive silver paste conductive paste, and a thermally sensitive catalytic conductive agent, each having a characteristic of losing conductivity due to structural or chemical changes when the temperature reaches a predetermined response threshold (120-200 ℃). In the invention, the heating source of the thermosensitive conductive agent is joule heat generated by internal short-circuit current flowing through the thermosensitive conductive agent, and the heat can heat the conductive agent to be above a preset response threshold value in millisecond time scale, so that the conductivity of the conductive agent is reduced to be below a preset failure value (< 10 -4 S/cm), and the current path of the failure sub-battery in the electrode layer is effectively cut off.
  17. 17. The lithium battery structure according to claim 1, wherein the entire sub-battery cells constitute the same sub-battery pack in parallel by means of current collectors, the sub-battery pack having the following functional properties: 1) In a normal working state, the sub-battery pack has the charge and discharge performance equivalent to that of a traditional lithium battery cell; 2) When internal short circuit occurs, the short circuit current generates focusing effect at the short circuit fault point in the faulty sub-battery, if the current density exceeds the sub-battery boundary fusing threshold value J_fuse, the fusing response mechanism is triggered in sequence, namely a) the boundary of the faulty sub-battery is fused due to the Joule heat effect, the current path on the current collector is cut off, b) the heat-sensitive conductive agent in the electrode layer of the faulty sub-battery generates heat and loses conductivity, the current path in the electrode layer is cut off, c) the double-disconnection mechanism fully isolates the faulty sub-battery unit from the sub-battery pack, and the rest part of the sub-battery pack is kept in normal operation; 3) When the abnormal working conditions such as external short circuit, overcharge or overdischarge are encountered, a current peak value appears in the tab area of the battery cell, and if the current density of the tab neighborhood exceeds J_fuse, the boundary of the sub-battery adjacent to the tab is synchronously fused, so that the battery cell is electrically disconnected from the battery pack, and the fault is prevented from diffusing to a higher system level. It should be noted that the above-mentioned external short circuit causing the tab area to be fused is not triggered under the normal operation condition of the Battery Management System (BMS), and is automatically started only in the extreme scenario of BMS failure or delayed response as a safety bottom policy.

Description

Lithium battery with micro-defect self-repairing and short-circuit fault self-isolating dual safety mechanism and preparation method thereof Technical Field The invention relates to the technical field of safety protection of lithium-based batteries, in particular to an active intervention type battery structure with double intrinsic response capability, which is suitable for various lithium batteries (including lithium ion batteries and lithium metal batteries) adopting liquid, solid and semi-solid electrolyte systems, and has the capability of dynamically identifying, intervening and cutting off internal short-circuit behaviors in the battery operation process, thereby effectively preventing the occurrence of thermal runaway, and remarkably improving the safety, stability and service life of a battery system. Background With the wide application of high-energy density lithium batteries in electric traffic, energy storage systems and consumer electronics, potential safety risks of the lithium batteries are becoming more interesting, particularly thermal runaway events, which are often accompanied by severe temperature rise, gas release, fire and even explosion once triggered, and pose a serious threat to terminal equipment and personnel safety. Studies have shown that almost all cases of thermal runaway can be traced to the occurrence of internal short circuits in batteries, and that the mechanisms can be categorized into endogenous and invasive short circuits. Endogenous shorts result from the gradual evolution of microscopic defects in the cell during normal operation, typically undergoing three stages of induction, nucleation, and growth. For example, in a liquid electrolyte system, factors such as degradation of the anode material, lithium deposition, and rupture of a solid electrolyte interface film (Solid Electrolyte Interphase, SEI) induce lithium dendrite growth, which causes short circuit of anode and cathode connection after penetrating through a separator, while in a solid electrolyte system, microstructure defects such as grain boundaries, holes and the like form local electric field singularities, thereby inducing lithium ion deposition and gradually constructing penetrating short circuit channels. Invasive short circuits are caused by external disturbance or manufacturing defects, including mechanical impact, foreign matter residues, high-temperature penetration of a diaphragm and other scenes, and usually do not have early warning to trigger strong short circuit current and instantaneously cause severe thermal runaway reaction. Once thermal runaway occurs, the battery can be caused to have severe interlocking effects such as temperature rise, rapid gas release, fire and even explosion, and the destructive power is enough to destroy the whole battery system and even the whole terminal equipment, so that the safety of personnel and equipment is seriously endangered. Particularly in lithium metal batteries, the thermal runaway process is more violent and uncontrollable, and is particularly harmful due to the extremely high reactivity of the negative electrode. The existing lithium battery safety protection scheme mainly comprises: 1) The Battery Management System (BMS) has the defects that the battery management system depends on external signal monitoring, has delayed response to the internal abnormality of the battery cell, and cannot find and cope with the internal short circuit behavior in time; 2) The material body modification scheme is that if ceramic is coated on the surface of a diaphragm or an electrode, or a flame retardant is added into electrolyte or the diaphragm, although the heat resistance of a battery can be improved to a certain extent, the limitation of static and passive protection is not eliminated, and the active recognition capability of the defect evolution process is lacking. Recent research on lithium battery safety technology has begun to gradually turn to the direction of constructing material response type protection mechanisms, in an attempt to achieve suppression of thermal runaway through intelligent behavior of the material body. For example, a flame retardant is released under high temperature conditions by using a thermally triggered microcapsule structure, or a voltage triggered conductive fault structure is designed to cut off a short circuit current path when a voltage suddenly drops. While these strategies have a role in improving battery safety, there are some key technology shortboards, such as: 1) The response mechanism depends on global variables (such as temperature and voltage), the triggering threshold is high, and the local defects in the battery cell are difficult to accurately identify; 2) The thermal trigger response has obvious hysteresis, is usually started after the thermal runaway enters an acceleration stage, and cannot realize pre-intervention; 3) The voltage change is insensitive to internal short circuit, and particularly, the voltage i