A heat exchange equalization method of a lithium ion battery cell

Abstract

The application discloses a heat exchange equalization method of a lithium ion battery cell, which comprises the following steps: A, an insulating cooling medium is introduced into the cooling flow channel of a composite hollow core pipe to perform internal forced heat exchange on the central region of a pole group; B, external heat exchange is performed on the outer wall region of the pole group through a heat transfer interface layer of the outer wall to form an internal and external bidirectional heat exchange network; C, during the charging process, the elastic porous insulating outer layer of the pole piece is expanded and extruded, so that the interlayer redundant electrolyte enters the cooling flow channel storage area through micropores; during the discharging process, the pole piece is contracted to form an interlayer negative pressure, and the electrolyte in the storage area is back-infiltrated to the interlayer of the pole group through micropores to realize dynamic self-balancing of the electrolyte; and D, when the local temperature of the battery cell reaches the triggering threshold of the heat-sensitive expansion blocking structure, the heat-sensitive structure is expanded to block the cooling flow channel and block the axial spread of thermal runaway. The application has the advantages that the radial temperature gradient in the battery cell can be effectively reduced, the risk of axial spread of thermal runaway is inhibited, and the safety performance and cycle stability of the battery cell are improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery thermal management technology, and in particular to a method for heat exchange equalization of lithium-ion cells. Background Technology

[0002] With the development trend of lithium-ion power batteries towards high-rate fast charging (typical value not less than 3C) and high energy density (typical value not less than 300Wh / kg), heat dissipation of the cell body and long-term cycle reliability have become key bottlenecks restricting the industrialization. Due to its high manufacturing efficiency and high yield, wound cells are currently the mainstream electrode configuration for large cylindrical (such as the 4680 system) and square aluminum-cased cells. However, its core electrode structure results in a long heat exchange path and a large radial temperature difference. Under high-rate conditions, local hot spots are prone to form in the center of the electrode assembly. These hot spots not only accelerate the degradation process of electrode materials, such as causing lithium metal precipitation and abnormal thickening of the solid electrolyte interface film, but may also trigger a chain reaction of thermal runaway.

[0003] To alleviate heat dissipation issues, the industry has attempted to design hollow channel structures inside battery cells to optimize heat conduction. For example, a utility model patent entitled "A Battery Cell and Battery," authorized on November 14, 2023, with authorization announcement number CN220021305U, describes a battery cell comprising a positive electrode and a negative electrode. The positive electrode has a hollow foil area in the middle of its positive active material for heat dissipation. This hollow foil area does not contain positive active material, and therefore does not generate heat during charging and discharging, thereby reducing the overall temperature of the battery, minimizing high-temperature conditions during battery use, reducing gas production, and improving battery capacity retention and volumetric energy efficiency.

[0004] However, the aforementioned existing technologies still have the following drawbacks that have not been effectively addressed: the heat exchange structure is simplistic, and the internal and external temperature differences remain significant. Under thermal runaway conditions, the central through-hole can easily become an axial acceleration channel for high-temperature flue gas and flames. Existing solutions lack a way to integrate a passive thermal blocking structure within the central channel, resulting in a high risk of overall thermal propagation.

[0005] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a heat exchange equalization method for lithium-ion cells, which can effectively reduce the radial temperature gradient inside the cell, suppress the risk of axial propagation of thermal runaway, and improve the safety performance and cycle stability of the cell.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] A method for heat exchange equalization of a lithium-ion battery cell, characterized in that the lithium-ion battery cell includes a metal shell, a sealing cover, and a coaxially wound electrode assembly housed within the shell. The lithium-ion battery cell also includes an adaptive composite hollow core tube, which is arranged along the winding center axis of the electrode assembly. The core tube includes an inner thermally conductive substrate and an elastic porous insulating outer layer covering the inner thermally conductive substrate. An axially penetrating cooling channel is provided inside the inner thermally conductive substrate. The core tube wall has several micropores to connect the cooling channel and the electrode assembly layer. At least one set of thermosensitive expansion blocking structures is axially arranged on the core tube. When the temperature reaches a trigger threshold, the thermosensitive expansion blocking structures expand and partially or completely block the cooling channel. A thermally conductive interface layer is provided between the outer wall of the electrode assembly and the metal shell. The specific process for heat exchange of the lithium-ion battery cell is as follows: A. Insulating cooling medium is introduced into the cooling channel of the composite hollow core tube to perform internal forced heat exchange in the central region of the electrode assembly; B. External heat exchange is carried out on the outer wall area through the heat transfer interface layer of the outer wall of the electrode group, forming a two-way heat exchange network inside and outside; C. During charging, the electrode expands and squeezes the elastic porous insulating outer layer, allowing the redundant electrolyte between the layers to enter the cooling channel storage area through the micropores; during discharging, the electrode contracts to form a negative pressure between the layers, and the electrolyte in the storage area seeps back into the electrode layer through the micropores, realizing the dynamic self-balancing of the electrolyte. D. When the local temperature of the battery cell reaches the trigger threshold of the thermal expansion blocking structure, the thermal structure expands and blocks the cooling channel, thus preventing the axial propagation of thermal runaway. The cooling medium in the cooling channel is insulating oil, deionized water, or an aqueous solution of ethylene glycol.

[0009] Forced heat exchange in the central region is achieved through cooling channels within the core tube, while efficient heat exchange in the external region is achieved through a thermally conductive interface layer, constructing a bidirectional heat exchange network that effectively solves the problems of large radial temperature differences and localized hot spots. Simultaneously, the elastic porous insulating outer layer and micropores of the core tube enable dynamic self-balancing of the electrolyte. More importantly, the thermosensitive expansion blocking structure can adaptively seal the cooling channels under abnormally high temperatures, effectively preventing the axial propagation of thermal runaway, thereby comprehensively improving the cell's heat dissipation efficiency, cycle life, and safety performance.

[0010] Preferably, the inner thermally conductive substrate is a thin-walled tubular structure made of copper, aluminum, or copper-aluminum alloy, and the elastic porous insulating outer layer is a porous material of polyurethane, polyolefin, or fluororubber with a thickness of 0.3~1.5mm and a porosity of 30%~70%.

[0011] By specifically defining the inner thermally conductive substrate of the core tube as a thin-walled tubular structure made of copper, aluminum, or a copper-aluminum alloy, the heat generated in the central region of the electrode assembly is ensured to be efficiently and rapidly conducted to the cooling medium inside the cooling channel, thereby effectively reducing the temperature gradient inside the cell. The thin-wall design minimizes thermal resistance while ensuring sufficient mechanical strength, improving overall heat exchange efficiency. Simultaneously, the elastic porous insulating outer layer uses porous materials such as polyurethane, polyolefin, or fluororubber, with its thickness precisely controlled between 0.3 and 1.5 mm and porosity between 30% and 70%. This outer layer not only provides reliable electrical insulation to prevent internal short circuits but also effectively buffers the stress generated by the electrodes during expansion and contraction during charging and discharging, maintaining a constant contact pressure between the electrode layers through its inherent elasticity and porous structure. Furthermore, this porous structure can also serve as a reservoir for the electrolyte, enabling dynamic absorption and reabsorption of the electrolyte when the internal pressure of the cell changes, thus solving the problem of uneven electrolyte distribution. The optimized selection of the aforementioned materials and structural parameters enables the core tube to achieve efficient thermal management while also ensuring the mechanical stability and electrolyte balance of the cell, significantly improving the overall performance and safety of the cell.

[0012] Preferably, the micropores on the core tube wall are distributed along the core tube axis, with the micropore diameter on the side facing the bottom of the electrode group being smaller than that on the side facing the top of the electrode group, and the micropore diameter range being 20~100μm.

[0013] By distributing micropores along the axial direction of the core tube wall, fluid exchange between the cooling channels and the electrode assembly layers is ensured throughout the entire axial length. Furthermore, the micropore diameter towards the bottom of the electrode assembly is designed to be smaller than that towards the top, with precise control within a diameter range of 20–100 μm. This differentiated diameter design allows for adaptive flow distribution of the cooling medium or electrolyte along the core tube axially, based on differences in fluid resistance at different locations. For example, during cell operation, if the heat dissipation demand in the bottom region of the electrode assembly is relatively low or requires finer electrolyte penetration, the smaller micropore diameter can effectively limit the fluid flow in that region; while the top region of the electrode assembly may require a larger fluid exchange volume due to heat accumulation or faster electrolyte consumption, in which case the larger micropore diameter provides more ample channels. This axially differentiated microporous design, together with the cooling channels inside the core tube and the interlayer of the electrode assembly, forms a precise fluid distribution network. This enables a more effective balance between the temperature distribution and electrolyte concentration inside the cell, preventing local overheating or electrolyte depletion, and improving the overall heat exchange efficiency and electrolyte self-balancing capability.

[0014] Preferably, the micropores of the elastic porous insulating outer layer can store excess electrolyte and allow it to permeate back into the electrode group under negative pressure between the electrode layers.

[0015] By designing the elastic porous insulating outer layer of the core tube to also function as a electrolyte storage layer, and utilizing its connectivity with the electrode layers through micropores, a dynamic electrolyte management system is constructed. During charging, the expansion of the electrodes compresses the electrolyte between the electrode layers. This excess electrolyte is not simply lost or accumulated, but is efficiently absorbed and stored by the abundant pores within the elastic porous insulating outer layer. This absorption process utilizes the capillary action and the capacity of the pores to effectively manage the electrolyte distribution within the core. Subsequently, during discharge or electrode contraction, a negative pressure naturally forms between the electrode layers. At this time, the electrolyte stored in the elastic porous insulating outer layer, driven by this negative pressure, can precisely seep back through the micropores on the core tube wall to the areas between the electrode layers that require electrolyte. This bidirectional electrolyte flow mechanism—absorbing and storing electrolyte during electrode expansion and replenishing it during electrode contraction—ensures that the electrolyte maintains a relatively balanced distribution within the electrode assembly. This mechanism, combined with the internal heat exchange function of the core tube, not only solves the thermal management problem inside the cell, but also further solves the dynamic balance problem of the electrolyte, avoiding local drying or electrolyte accumulation, thereby significantly improving the cycle life and safety performance of the cell.

[0016] Preferably, the thermal expansion blocking structure includes thermal expansion particles or thermal expansion plugs disposed in the cooling channel, with a trigger threshold of 100~150℃, and does not block or partially blocks the cooling channel at room temperature to retain the flow cross section of the cooling medium.

[0017] By incorporating a thermosensitive expansion blocking structure—specifically, thermosensitive expansion particles or thermal expansion plugs—within the cooling channels of the battery cell, these particles or plugs maintain their original shape under normal operating temperatures, preventing any substantial obstruction to the cooling channels. This ensures the smooth flow of the cooling medium through the channels, facilitating forced internal heat exchange in the central region of the electrode assembly. This design guarantees efficient heat dissipation and maintains temperature equilibrium within the battery cell under normal operating conditions. When an abnormal situation causes a rapid increase in local temperature within the cell, reaching a preset trigger threshold of 100-150°C, the thermosensitive expansion particles or plugs within the cooling channels rapidly expand. This expansion fills and seals the cooling channels, blocking the flow of the cooling medium. In this way, the thermosensitive expansion blocking structure effectively isolates the overheated area from the rest of the battery cell, preventing heat from spreading axially through the cooling channels. This allows for intervention in the early stages of thermal runaway, significantly improving the safety of the battery cell. This mechanism cleverly balances the heat dissipation requirements of the battery cell during normal operation with the safety protection requirements under abnormal conditions, enabling the battery cell to maintain high performance while having a stronger ability to suppress thermal runaway.

[0018] Preferably, the thermal interface layer is a highly thermally conductive flexible thermally conductive adhesive or a thermally conductive pad. The thermal interface layer is filled between the outer wall of the electrode assembly and the inner wall of the metal shell to construct an external heat exchange circuit. The cooling channels constitute an internal heat exchange circuit to form bidirectional heat exchange between the inside and outside of the battery cell.

[0019] By defining the thermal interface layer as a highly thermally conductive flexible adhesive or pad and filling it between the outer wall of the electrode assembly and the inner wall of the metal casing, a highly efficient external heat exchange loop is constructed. During cell operation, heat is generated inside the electrode assembly. Heat near the periphery can be transferred to the metal casing with extremely low thermal resistance through this highly thermally conductive interface layer, and then dissipated to the external environment. Simultaneously, heat generated in the central region of the cell is directly removed by the circulating cooling medium through the internal cooling channels forming an internal heat exchange loop. This synergistic effect of the internal cooling channels and the external thermal interface layer creates a bidirectional heat exchange mechanism between the inside and outside of the cell. The internal loop focuses on rapidly removing core heat, while the external loop is responsible for efficiently conducting overall heat to the casing. This bidirectional thermal management strategy ensures more uniform and efficient temperature control of the cell under different operating conditions, especially during high-power charging and discharging, effectively preventing localized overheating and thus improving the cell's safety, cycle life, and performance stability.

[0020] As a preferred option, the elastic porous insulating outer layer of the composite hollow core tube has a compressible resilience of 30% to 80%, and deforms synchronously with the expansion and contraction of the electrode during charging and discharging to maintain constant pressure between the electrode layers.

[0021] By designing the elastic porous insulating outer layer of the composite hollow core tube to have a compressible rebound capacity of 30%~80%, and enabling it to deform synchronously with the expansion and contraction of the electrode during charging and discharging, a constant pressure is maintained between the electrode layers. When the electrode expands during charging, the elastic porous insulating outer layer is compressed, absorbing the stress generated by the electrode expansion; when the electrode contracts during discharging, the elastic porous insulating outer layer rebounds, filling the gaps created by the electrode contraction. This dynamic adaptability ensures that the elastic porous insulating outer layer and the electrode layers always maintain a tight and stable contact, avoiding poor contact or uneven pressure caused by changes in electrode volume. The stable contact pressure not only ensures efficient heat exchange between the cooling channel and the electrode layers through micropores, but also facilitates the uniform distribution and dynamic self-balancing of the electrolyte between the electrode layers, thereby improving the overall performance and safety of the cell.

[0022] In existing technologies, hollow channels can easily become axial acceleration channels for high-temperature flue gas and flames during thermal runaway. This application addresses this by using a thermosensitive expansion blocking structure to rapidly expand and block the cooling channels at the trigger threshold temperature, physically cutting off the heat propagation path. Simultaneously, during charging, the expansion of the electrode sheets compresses the elastic porous insulating outer layer, causing redundant electrolyte to enter the storage area through these micropores. During discharging, the interlayer negative pressure drives electrolyte re-perfusion, achieving dynamic self-balancing of the electrolyte. This technical solution effectively solves the thermal propagation safety hazard associated with hollow channels, significantly reduces the overall thermal propagation risk, optimizes the electrolyte distribution within the electrode assembly, and improves the safety and cycle reliability of the battery cell. Attached Figure Description

[0023] Figure 1 This is a schematic cross-sectional view of the lithium-ion battery cell of the present invention. Figure 2 This is a schematic diagram of the overall transverse cross-sectional structure of the present invention; Figure 3 This is a schematic diagram of the principle of the method disclosed in this invention; in the figure: metal shell 1, sealing cover plate 2, coaxial wound electrode assembly 3, core tube 4, inner heat-conducting substrate 5, elastic porous insulating outer layer 6, cooling channel 7, thermosensitive expansion blocking structure 8, heat-conducting interface layer 9, micropores 10. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] This application proposes a heat exchange equalization method for lithium-ion battery cells, such as lithium-ion battery cells... Figure 1 and Figure 2 As shown, the device includes a metal outer shell 1, a sealing cover plate 2, and a coaxial wound electrode assembly 3 housed within the outer shell. It also includes an adaptive composite hollow core tube 4, which is arranged along the winding center axis of the electrode assembly. The core tube 4 includes an inner thermally conductive substrate 5 and an elastic porous insulating outer layer 6 covering the inner thermally conductive substrate 5. The inner thermally conductive substrate 5 has an axially penetrating cooling channel 7. The core tube 4 has several micropores 10 on its wall to connect the cooling channel 7 with the electrode assembly layer. The core tube 4 has at least one set of thermosensitive expansion blocking structures 8 arranged axially. When the temperature reaches the trigger threshold, the thermosensitive expansion blocking structures 8 expand and partially or completely block the cooling channel 7. A thermally conductive interface layer 9 is provided between the outer wall of the electrode assembly and the metal outer shell 1.

[0026] For ease of understanding, the following explains some key terms in this embodiment: Adaptive coaxial hollow bidirectional heat exchange self-balancing lithium-ion cell: This refers to a lithium-ion cell that integrates a coaxial hollow structure, enabling adaptive thermal management based on internal temperature changes. It also efficiently dissipates heat through bidirectional heat exchange paths, while achieving dynamic self-balancing of the electrolyte to improve cell safety, cycle life, and fast charging performance.

[0027] Metal Casing 1: An external structure used to encapsulate the internal components of the battery cell, providing mechanical protection and a sealed environment. This casing is typically made of metal materials such as aluminum or steel, which have good thermal conductivity and strength.

[0028] Sealing cover 2: It works in conjunction with the metal casing 1 to form a sealed cavity for the battery cell. This cover typically has electrode lead-out terminals and a safety pressure relief device to ensure the stability and safety of the internal environment of the battery cell.

[0029] Coaxial wound electrode assembly 3: The core functional component inside the cell, composed of layers of positive electrode plates, negative electrode plates, and separator wound together to form a cylindrical or flat cylindrical structure. This electrode assembly is the main area where electrochemical reactions occur.

[0030] Adaptive composite hollow core tube 4: A tubular structure located at the central axis of the electrode assembly winding. This core tube 4 is made of composite materials and is hollow inside, enabling adaptive adjustment according to the cell's operating state to achieve heat management and electrolyte balance.

[0031] Inner thermally conductive substrate 5: The internal structure of the core tube 4, primarily responsible for heat conduction. This substrate is typically made of a high thermal conductivity material and has internal channels for the flow of the cooling medium.

[0032] Elastic porous insulating outer layer 6: A material layer covering the outer surface of the inner thermally conductive substrate 5. This outer layer has an elastic and porous structure, providing insulation protection, liquid storage function, and adapting to the expansion and contraction of the electrode assembly.

[0033] Cooling channel 7: An axially penetrating channel located inside the inner heat-conducting substrate 5. The cooling medium flows through this channel, carrying away heat from the central region of the electrode assembly, thus achieving forced internal heat exchange.

[0034] Micropores 10: Tiny holes formed in the wall of the core tube 4. These micropores 10 connect the cooling channel 7 to the electrode layer, serving as channels for the exchange of cooling medium and electrolyte. For ease of demonstration, Figure 1 The micro-hole 10 has been enlarged, and the actual size of the micro-hole 10 is much smaller than the size in the drawing. The size ratio of the micro-hole 10 to the core tube 4 is not the actual ratio.

[0035] Thermal expansion blocking structure 8: A special structure installed within the cooling channel 7. This structure is temperature-sensitive; when the temperature reaches a preset trigger threshold, its material expands, thereby partially or completely blocking the cooling channel 7 to prevent the axial spread of heat within the channel.

[0036] Trigger threshold: refers to the specific temperature at which the thermal expansion blocking structure 8 begins to expand and exert its blocking effect. This threshold is usually set as the warning temperature before thermal runaway occurs in the battery cell.

[0037] Thermal interface layer 9: A material layer disposed between the outer wall of the electrode assembly and the inner wall of the metal shell 1. This layer has good thermal conductivity and is used to efficiently transfer heat from the outer region of the electrode assembly to the metal shell 1, thus constructing an external heat exchange loop.

[0038] This embodiment provides an adaptive coaxial hollow bidirectional heat exchange self-balancing lithium-ion battery cell. The overall structure of the battery cell includes a metal casing 1, a sealing cover 2, and a coaxial wound electrode assembly 3 housed within the casing. The metal casing 1 provides external protection and structural support for the battery cell, while the sealing cover 2 ensures the airtightness of the internal environment of the battery cell. The coaxial wound electrode assembly 3 is the core part of the battery cell for electrochemical reactions, and it is formed by winding the positive electrode, negative electrode, and separator. As one implementation, the metal casing 1 can be manufactured using a stamping process, the sealing cover 2 can be connected to the casing using laser welding, and the electrode assembly can be completed using automated winding equipment.

[0039] The cell also includes an adaptive composite hollow core tube 4, which is arranged along the winding center axis of the electrode assembly. The arrangement of the core tube 4 is designed to improve the heat dissipation efficiency in the central region of the electrode assembly and to provide a channel for the dynamic equilibration of the electrolyte. For example, the core tube 4 can be a simple hollow cylinder with an outer diameter that matches the inner diameter of the electrode assembly, and is installed at the center of the electrode assembly by mechanical fixing or adhesive bonding.

[0040] The core tube 4 comprises an inner thermally conductive substrate 5 and an elastic porous insulating outer layer 6 covering the inner layer. The inner thermally conductive substrate 5 is primarily responsible for heat conduction, and its material selection should possess good thermal conductivity. The elastic porous insulating outer layer 6 provides electrical insulation and possesses a certain degree of elasticity and porous structure. As one implementation method, the inner thermally conductive substrate 5 can be made of a metal material with high thermal conductivity, for example, by forming a tubular structure through extrusion or stretching processes. The elastic porous insulating outer layer 6 can be made of a polymer material with elastic and porous properties, coated or sleeved onto the outside of the inner thermally conductive substrate 5.

[0041] The inner thermally conductive substrate 5 has an axially continuous cooling channel 7 inside. This cooling channel 7 is the path for the flow of the cooling medium, used to remove the heat generated in the central region of the electrode assembly. For example, the cooling channel 7 can be a single straight channel, with the cooling medium flowing in from one end and out from the other end.

[0042] The core tube 4 has several micropores 10 formed in its wall to connect the cooling channel 7 with the electrode assembly layers. These micropores 10 serve as channels for mass exchange between the cooling channel 7 and the electrolyte inside the electrode assembly, and also assist in the transfer of heat from the electrode assembly layers to the cooling channel 7. As one implementation method, these micropores 10 can be uniformly distributed on the wall of the core tube 4 by laser drilling or mechanical drilling.

[0043] The core tube 4 is axially provided with at least one set of thermosensitive expansion blocking structures 8. When the temperature reaches a trigger threshold, the thermosensitive expansion blocking structure 8 expands and partially or completely blocks the cooling channel 7. The main function of this structure is to physically block the cooling channel 7 when the internal temperature of the cell abnormally rises, thereby limiting the rapid spread of heat along the axial direction and improving the safety of the cell. For example, the thermosensitive expansion blocking structure 8 can be made of a material whose volume increases significantly at a specific temperature and embedded in the cooling channel 7 in a ring or sheet structure.

[0044] A thermally conductive interface layer 9 is provided between the outer wall of the electrode assembly and the metal casing 1. This thermally conductive interface layer 9 is used to enhance the heat transfer efficiency between the outer periphery of the electrode assembly and the metal casing 1, thereby constructing an effective external heat dissipation path. As one implementation, the thermally conductive interface layer 9 can be made of a flexible material with good thermal conductivity, for example, by coating or filling between the outer wall of the electrode assembly and the inner wall of the metal casing 1.

[0045] The following example will provide a more detailed explanation of the above technical solution: Suppose user A's electric vehicle is undergoing high-rate fast charging at charging station A. In traditional lithium-ion cells, due to the solid wound structure of the electrode assembly, heat transfer from the central region to the outer casing is a long path, easily leading to excessively high temperatures at the center of the electrode assembly, forming localized hot spots. This can then cause lithium plating and abnormal thickening of the SEI film, affecting cell performance and lifespan. Furthermore, in the event of thermal runaway, the central channel may become a conduit for the axial propagation of heat and fumes, increasing safety risks.

[0046] The adaptive coaxial hollow bidirectional heat exchange self-balancing lithium-ion cell in this embodiment solves the above problems in the following ways: First, the coaxially wound electrode assembly 3 of the battery cell has an adaptive composite hollow core tube 4 at its center. The inner thermally conductive substrate 5 of the core tube 4 has an axially penetrating cooling channel 7. During fast charging, an insulating cooling medium is pumped into this cooling channel 7 to force heat exchange in the central region of the electrode assembly. As a result, the heat generated at the center of the electrode assembly can be directly carried away by the cooling medium, significantly shortening the heat conduction path from the center to the outside, effectively reducing the radial temperature difference of the electrode assembly, and preventing the formation of localized hot spots.

[0047] Meanwhile, a thermally conductive interface layer 9 is provided between the outer wall of the electrode assembly and the metal casing 1. This thermally conductive interface layer 9 efficiently transfers heat from the outer region of the electrode assembly to the metal casing 1, and dissipates it to the external environment through the metal casing 1. Together with the cooling channel 7 inside the core tube 4, this forms a bidirectional heat exchange network between the inside and outside of the battery cell. Through this bidirectional heat exchange mechanism, the overall heat dissipation efficiency of the battery cell is improved, ensuring that the battery cell temperature remains within a suitable range under high-rate fast charging conditions.

[0048] Furthermore, the core tube 4 has several micropores 10 on its wall, connecting the cooling channel 7 to the electrode assembly layers. During the charging and discharging process of the battery cell, the elastic porous insulating outer layer 6 of the core tube 4 deforms synchronously with the expansion and contraction of the electrode sheets. When the electrode sheets expand, they compress the elastic porous insulating outer layer 6, causing excess electrolyte between the electrode assembly layers to enter the liquid storage area within the cooling channel 7 through the micropores 10. When the electrode sheets contract, a negative pressure is formed between the electrode assembly layers, and the electrolyte in the liquid storage area seeps back into the electrode assembly layers through the micropores 10, thereby achieving dynamic self-balancing of the electrolyte, ensuring sufficient wetting of the electrolyte inside the electrode assembly, and improving the cycle performance of the battery cell.

[0049] More importantly, the core tube 4 is axially equipped with at least one set of thermosensitive expansion blocking structures 8. In extreme cases, such as when a region inside the cell experiences abnormal heating leading to a rapid temperature rise that reaches the trigger threshold of the thermosensitive expansion blocking structure 8, the structure will rapidly expand. This expanding structure will partially or completely block the cooling channel 7, thereby physically preventing the axial spread of heat, high-temperature flue gas, or flames along the cooling channel 7. Therefore, even if localized thermal runaway occurs within the cell, its propagation path is effectively limited, reducing the risk of overall thermal propagation and improving the intrinsic safety performance of the cell.

[0050] Based on the above examples, the adaptive coaxial hollow bidirectional heat exchange self-balancing lithium-ion cell of this embodiment demonstrates significant technological contributions.

[0051] Compared to the long heat exchange path, large radial temperature difference, and local hot spots caused by the solid electrode assembly structure in existing technologies, this embodiment achieves direct forced heat exchange in the central region of the electrode assembly by setting an adaptive composite hollow core tube 4 at the center of the electrode assembly and setting an axially penetrating cooling channel 7 inside the inner thermally conductive substrate 5. This internal heat exchange loop, combined with the external heat exchange loop constructed by the thermally conductive interface layer 9 between the outer wall of the electrode assembly and the metal shell 1, forms a bidirectional heat exchange network inside and outside the battery cell. As a result, the overall heat dissipation efficiency of the battery cell is improved, the radial temperature difference of the electrode assembly is effectively reduced, and the formation of local hot spots is avoided, thus solving the defects of the single heat exchange structure and significant internal and external temperature difference in existing technologies.

[0052] Furthermore, in existing technologies, the hollow channel can easily become an axial acceleration channel for high-temperature flue gas and flames under thermal runaway conditions, and it lacks a passive thermal blocking structure, resulting in a high risk of thermal propagation across the entire battery pack. This embodiment addresses this by axially installing a thermosensitive expansion blocking structure 8 in the core tube 4. This structure automatically expands and blocks the cooling channel 7 when the temperature reaches a trigger threshold. This innovative design can physically block the axial propagation of heat, flue gas, or flames along the central channel when a localized thermal anomaly occurs in the battery cell, improving the intrinsic safety performance of the battery cell and effectively reducing the risk of thermal propagation across the entire battery pack.

[0053] Furthermore, the elastic porous insulating outer layer 6 and the micropores 10 in the tube 4 of this embodiment enable the electrolyte to achieve dynamic self-balancing during the expansion and contraction of the electrode during charging and discharging. When the electrode expands, excess electrolyte is squeezed into the storage area within the cooling channel 7; when the electrode contracts, the electrolyte seeps back into the interlayer of the electrode assembly. This mechanism ensures sufficient wetting of the electrolyte inside the electrode assembly, which has a positive effect on improving the long-term cycle reliability and capacity retention of the cell, and is a technical point that has not been mentioned or effectively solved in the prior art.

[0054] In summary, the technical solution of this embodiment, by integrating the coaxial hollow core tube 4, the internal and external bidirectional heat exchange network, the thermal expansion blocking structure 8, and the electrolyte dynamic self-balancing mechanism, comprehensively improves the heat dissipation efficiency, thermal runaway safety, and cycle life of lithium-ion cells, providing an effective technical path for the development of high-rate fast charging and high-energy-density cells.

[0055] In some other embodiments, this application proposes a lithium-ion battery cell, which includes a metal casing 1, a sealing cover 2, and a coaxial wound electrode assembly 3 housed within the casing. It also includes an adaptive composite hollow core tube 4, which is arranged along the winding center axis of the electrode assembly. The core tube 4 includes an inner thermally conductive substrate 5 and an elastic porous insulating outer layer 6 covering the inner layer. An axially penetrating cooling channel 7 is provided inside the inner thermally conductive substrate 5. The core tube 4 has several micropores 10 on its wall to connect the cooling channel 7 with the electrode assembly layer. At least one set of thermosensitive expansion blocking structures 8 is axially arranged on the core tube 4. When the temperature reaches a trigger threshold, the thermosensitive expansion blocking structures 8 expand and partially or completely block the cooling channel 7. A thermally conductive interface layer 9 is provided between the outer wall of the electrode assembly and the metal casing 1. However, if the materials of the inner thermally conductive substrate 5 and the elastic porous insulating outer layer 6 are not properly selected or the structural parameters are not accurate, the overall thermal conductivity, mechanical strength and dynamic management capability of the core tube 4 may not reach the optimal state, thereby affecting the performance and safety of the cell.

[0056] In this regard, this application further proposes that the inner thermally conductive substrate 5 is a thin-walled tubular structure made of copper, aluminum, or copper-aluminum alloy, and the elastic porous insulating outer layer 6 is a porous material of polyurethane, polyolefin, or fluororubber with a thickness of 0.3~1.5mm and a porosity of 30%~70%.

[0057] The inner thermally conductive substrate 5 is the core thermally conductive part of the core tube 4, responsible for efficiently transferring heat from the central region of the electrode assembly to the cooling medium within the cooling channel 7, ensuring rapid heat transfer from the electrode assembly and maintaining a balanced internal temperature within the cell. Besides copper, aluminum, or copper-aluminum alloys, the inner thermally conductive substrate 5 can also be made into a thin-walled tubular structure using highly thermally conductive carbon fiber composites or graphene composites to further improve thermal conductivity and reduce weight. The thin-walled tubular structure can be fabricated using processes such as extrusion molding, stretch molding, or winding welding, and its wall thickness can be optimized according to the required thermal conductivity and mechanical strength. The elastic porous insulating outer layer 6 is the material covering the inner thermally conductive substrate 5, possessing insulation, elasticity, and porosity. Its function is to provide electrical insulation, buffer the expansion pressure of the electrode sheets, store and re-permeate the electrolyte, and maintain the interlayer pressure of the electrode sheets. Besides polyurethane, polyolefin, or fluororubber materials, silicone rubber-based porous materials or ceramic fiber porous materials can also be used, as these materials also possess good insulation, elasticity, and resistance to electrolyte corrosion. Porous materials can be prepared by methods such as foaming, electrospinning, or sintering to control their pore structure and porosity. A thickness of 0.3–1.5 mm and a porosity of 30%–70% are preferred ranges, but the thickness or porosity can be adjusted appropriately according to the specific design and application of the battery cell, such as high energy density or high power applications, to optimize its buffering, insulation, and liquid storage performance.

[0058] In one specific implementation, the inner thermally conductive substrate 5 of the core tube 4 can be made of high-purity aluminum alloy (e.g., 6061 aluminum alloy) through a precision extrusion molding process, forming a thin-walled tubular structure with a wall thickness of approximately 0.5 mm. This aluminum alloy tube has excellent thermal conductivity and good mechanical strength. The elastic porous insulating outer layer 6 covering it can be prepared from polyurethane material using microporous foaming technology, forming a porous structure with a thickness of 0.8 mm and a porosity of 50%. This polyurethane porous layer not only has good electrical insulation, but its microporous structure can also effectively adsorb and release electrolyte, and its elasticity can adapt to the expansion and contraction of the electrode.

[0059] Through the above technical solutions, the inner thermally conductive substrate 5 adopts a thin-walled tubular structure of copper, aluminum, or copper-aluminum alloy with high thermal conductivity, which significantly improves the thermal conductivity of the core tube 4, ensures the rapid removal of heat from the inside of the cell, and effectively reduces the risk of local overheating of the cell. At the same time, the elastic porous insulating outer layer 6 is made of polyurethane, polyolefin, or fluororubber porous materials, and its thickness and porosity are precisely controlled, so that this layer can provide excellent electrical insulation performance, effectively buffer the volume changes during the charging and discharging process of the electrode plates, maintain stable contact pressure between the electrode plates, and realize the dynamic storage and reabsorption of electrolyte, thereby optimizing the internal environment of the cell, extending the service life of the cell, and further improving the overall safety and reliability of the cell.

[0060] This application further proposes that the micropores 10 on the wall of the core tube 4 are distributed along the axial direction of the core tube 4, and the diameter of the micropores 10 on the side facing the bottom of the electrode group is smaller than the diameter of the micropores 10 on the side facing the top of the electrode group, with the diameter of the micropores 10 ranging from 20 to 100 μm.

[0061] Specifically, the micropores 10 on the wall of the core tube 4 are distributed along the axial direction of the core tube 4, meaning that holes for connecting the cooling channels 7 and the electrode assembly layers are uniformly or non-uniformly arranged along the length of the core tube 4. This distribution ensures that the cooling medium or electrolyte can interact with the electrode assembly along its entire axial length. This can be achieved by forming a series of tiny channels on the wall of the core tube 4 through processes such as laser drilling, mechanical drilling, or chemical etching. The diameter of the micropores 10 on the side facing the bottom of the electrode assembly is smaller than that on the side facing the top of the electrode assembly. This design aims to optimize the distribution of the cooling medium or electrolyte along the axial direction of the electrode assembly. When the cell is working, the temperature distribution or electrolyte requirements of the bottom and top regions may differ. By adjusting the diameter of the micropores 10, the fluid resistance in different regions can be controlled, thereby achieving a finer fluid distribution. For example, in some cases, the bottom may require a smaller flow rate to avoid overcooling or maintain a specific pressure, while the top may require a larger flow rate to enhance heat dissipation. This can be achieved by using a variable-diameter drill bit, segmented laser drilling, or mask etching during the manufacturing process to form micropores 10 of different diameters at different axial positions of the core tube 4. The pore size of the micropores 10 ranges from 20 to 100 μm. This range is set based on a comprehensive consideration of electrolyte viscosity, interlayer gaps between electrode groups, and fluid dynamics characteristics to ensure that the cooling medium or electrolyte can effectively penetrate into the interlayer gaps between electrode groups, while avoiding clogging of the micropores 10 by the electrode group material. In this embodiment, the top of the stage group is the positive electrode, and the bottom of the stage group is the negative electrode.

[0062] In one specific implementation, the micropores 10 on the wall of the core tube 4 can be processed using laser drilling technology. Multiple regions can be defined along the axial length of the core tube 4, for example, dividing the core tube 4 axially into a bottom region, a middle region, and a top region. In the bottom region, the pore diameter of the micropores 10 can be set to 20μm to 40μm; in the middle region, the pore diameter can be set to 40μm to 70μm; and in the top region, the pore diameter can be set to 70μm to 100μm. These micropores 10 are uniformly or non-uniformly distributed along the axial direction of the core tube 4, for example, a row of micropores 10 can be set at certain intervals (such as 1mm or 2mm), with each row of micropores 10 containing several circumferentially distributed holes. In this way, the pore diameter of the micropores 10 can gradually increase from the bottom to the top, thereby enabling precise distribution of the cooling medium or electrolyte according to the temperature gradient and electrolyte requirements inside the cell during actual operation.

[0063] Through the above technical solution, the micropores 10 on the wall of the core tube 4 are distributed axially, and the micropore diameter on the side facing the bottom of the electrode group is smaller than that on the side facing the top of the electrode group. This effectively solves the problem of uneven axial temperature distribution inside the cell and poor heat exchange and electrolyte balancing caused by differences in electrolyte flow characteristics. This differentiated micropore design allows the cooling medium or electrolyte to be precisely distributed according to the actual needs of different axial positions of the cell, avoiding local overcooling or overheating, as well as local enrichment or depletion of electrolyte. Therefore, this solution can significantly improve the overall heat exchange efficiency and electrolyte self-balancing ability of the cell, extend the cell's service life, and improve its safety performance.

[0064] In some other embodiments, this application proposes an adaptive coaxial hollow bidirectional heat exchange self-balancing lithium-ion battery cell, including a metal shell 1, a sealing cover 2, and a coaxial wound electrode assembly 3 housed within the shell. It also includes an adaptive composite hollow core tube 4, which is arranged along the winding center axis of the electrode assembly. The core tube 4 includes an inner thermally conductive substrate 5 and an elastic porous insulating outer layer 6 covering the inner layer. An axially penetrating cooling channel 7 is provided inside the inner thermally conductive substrate 5. The core tube 4 has several micropores 10 on its wall to connect the cooling channel 7 with the electrode assembly layer. At least one set of thermosensitive expansion blocking structures 8 is axially arranged on the core tube 4. When the temperature reaches a trigger threshold, the thermosensitive expansion blocking structures 8 expand and partially or completely block the cooling channel 7. A thermally conductive interface layer 9 is provided between the outer wall of the electrode assembly and the metal shell 1.

[0065] In some embodiments of this application, the lithium-ion cell undergoes forced internal heat exchange through the cooling channels 7 within the core tube 4, and communicates with the electrode layers through the micropores 10 in the tube wall of the core tube 4 to achieve heat exchange. However, during the long-term operation of the lithium-ion cell, especially under charge-discharge cycles, the electrodes expand and contract, which may lead to uneven distribution of electrolyte between the electrode layers, or even insufficient electrolyte in local areas, thereby affecting the performance and lifespan of the cell.

[0066] In this regard, this application further proposes that the elastic porous insulating outer layer 6 also has a liquid storage function, in which redundant electrolyte can be absorbed and stored in the pores, and then back into the electrode group through the micropores 10 under the negative pressure between the electrode groups.

[0067] The flexible porous insulating outer layer 6 not only provides electrical insulation and mechanical support, but is also designed to contain and store electrolyte. Its porous structure provides numerous microscopic spaces that can serve as temporary reservoirs for the electrolyte. This electrolyte storage function can be achieved by selecting materials with high porosity and good wettability, such as certain polymer foams or fiber felts. When excess electrolyte exists inside the cell, such as during electrolyte injection or when the electrode expands and compresses the electrolyte, this electrolyte can be absorbed and temporarily stored by the pore structure inside the flexible porous insulating outer layer 6 through capillary action or direct wetting. This absorption and storage mechanism ensures that the electrolyte does not flow freely inside the cell or accumulate in non-functional areas, thereby improving electrolyte utilization efficiency and cell safety. During cell discharge or electrode shrinkage, localized negative pressure areas may form between the electrode layers. Under this negative pressure, the electrolyte stored in the pores of the flexible porous insulating outer layer 6 can permeate back into the electrode layers against the pressure gradient through the micropores 10 on the wall of the core tube 4. This refluxing mechanism ensures that electrolyte can be replenished in a timely manner when electrolyte demand increases or when there is a local electrolyte shortage, maintaining the ion conduction pathway within the electrode assembly and thus achieving dynamic self-balancing of the electrolyte.

[0068] In one specific implementation, the elastic porous insulating outer layer 6 can be made of porous polymer materials such as polyvinylidene fluoride (PVDF) or polyethylene (PE). These materials have good chemical stability and mechanical strength, and can achieve high porosity and interconnected pore structures through specific preparation processes. For example, a porous membrane or coating with a micron-scale pore size distribution can be prepared using phase separation or template methods and then coated onto the inner thermally conductive substrate 5. During charging, the electrodes expand, squeezing the electrolyte between the electrode layers to the vicinity of the core tube 4. This electrolyte is then rapidly absorbed by the pores of the elastic porous insulating outer layer 6. These pores act like miniature sponges, efficiently adsorbing and storing the electrolyte. During discharging, the electrodes contract, creating a negative pressure between the electrode layers. At this time, the electrolyte stored in the elastic porous insulating outer layer 6 re-permeates back into the electrode layers through micropores 10 on the wall of the core tube 4, such as micropores with a diameter of 50 micrometers, ensuring that the electrodes are always immersed in sufficient electrolyte.

[0069] Through the above technical solution, the elastic porous insulating outer layer 6 not only provides insulation and support but also has a dynamic electrolyte management function. This design effectively solves the problems of uneven electrolyte distribution and localized drying caused by electrode expansion and contraction during long-term charge-discharge cycles in lithium-ion cells. Redundant electrolyte can be absorbed and stored in a timely manner and seep back into the interlayer of the electrode assembly when needed, thereby maintaining the dynamic self-balancing of the electrolyte within the electrode assembly. This significantly improves the ion conduction efficiency of the cell, reduces internal resistance, extends the cycle life of the cell, and enhances the performance stability and safety of the cell under different operating conditions.

[0070] In some other embodiments, this application proposes a lithium-ion battery cell that manages the internal temperature of the cell through a cooling channel 7 and a thermistor expansion blocking structure 8 within the cell tube 4. However, in practical applications, ensuring that the thermistor expansion blocking structure 8 does not unnecessarily obstruct the cooling channel 7 during normal cell operation, while simultaneously and rapidly and effectively sealing the channel when local temperature rises abnormally to prevent the spread of thermal runaway, is a critical issue requiring careful design and balance.

[0071] In this regard, this application further proposes that the above-mentioned thermal expansion blocking structure 8 includes thermal expansion particles or thermal expansion plugs disposed in the cooling channel 7, with a trigger threshold of 100~150℃, and does not block or partially blocks the cooling channel 7 at room temperature to retain the flow cross section of the cooling medium.

[0072] Thermosensitive expansion particles are tiny particles that expand in volume at specific temperatures, typically made of polymers or phase change materials. For example... Figure 1 In the illustrated embodiment, the thermosensitive expansion blocking structure 8 employs thermosensitive expansion particles, and filters are provided at both ends of the cooling channel 7 to confine the thermosensitive expansion particles within the cooling channel 7. When the internal temperature of the battery cell reaches its trigger threshold, these particles rapidly expand, thereby filling and sealing the cooling channel 7. A thermosensitive expansion plug refers to a block-shaped or columnar structure pre-placed within the cooling channel 7 that expands at a specific temperature. Similar to particles, its expansion aims to block the channel at high temperatures. Both types of blocking structures can physically seal the cooling channel 7, preventing the flow of the cooling medium or further heat transfer. The trigger threshold refers to the temperature at which the thermosensitive expansion blocking structure 8 begins to expand significantly and exert its sealing effect. Setting the trigger threshold in the range of 100~150℃ is based on the typical starting temperature of thermal runaway in lithium-ion batteries. Within this temperature range, localized overheating may have already occurred inside the battery cell, but it has not yet developed to the stage of complete runaway. The purpose of selecting this range is to intervene in the early stages of thermal runaway, providing an important safety barrier for the battery cell and preventing further deterioration and spread of thermal runaway. "Unblocked at room temperature" means that at the normal operating temperature of the battery cell, the thermistor expansion blocking structure 8 maintains its original size and does not obstruct the cooling channel 7, ensuring that the cooling medium can flow freely and thus maintaining the normal heat dissipation function of the battery cell. "Partially blocked" means that at room temperature, the thermistor expansion blocking structure 8 may occupy part of the space in the cooling channel 7, but still retains sufficient flow cross-section to allow the cooling medium to pass through. This design can preset the resistance to a certain extent while ensuring the cooling effect. The purpose of retaining the cooling medium flow cross-section is to ensure that the battery cell can continuously and effectively exchange heat during normal operation and avoid overheating of the battery cell due to improper blocking of the cooling channel 7.

[0073] The following is a specific example illustrating this: the thermosensitive expansion blocking structure 8 can employ microencapsulated paraffin particles as thermosensitive expansion particles. These particles are uniformly dispersed and fixed within a porous support material in the cooling channel 7. The melting point and expansion characteristics of paraffin can be precisely controlled, causing it to begin rapid expansion at, for example, 120°C. At room temperature, these paraffin particles are small in size and do not significantly affect the flow cross-section of the cooling channel 7, allowing the cooling medium to pass freely. When the local temperature inside the battery cell rises to 120°C, the paraffin particles rapidly melt and expand, increasing in volume several times, thereby effectively filling and sealing the cooling channel 7. As another implementation, the thermosensitive expansion blocking structure 8 can employ thermal expansion plugs made of shape memory polymers. These thermal expansion plugs are pre-processed into a shape that allows the cooling medium to flow at room temperature and are placed in specific locations within the cooling channel 7. When the battery cell temperature reaches a trigger threshold of, for example, 130°C, the shape memory polymer undergoes a phase transition and returns to its preset expansion shape, thereby completely sealing the cooling channel 7. At room temperature, the thermal expansion plug can be designed to partially block the cooling channel 7 to retain a certain flow cross-section and ensure the continuous flow of the cooling medium.

[0074] Through the above technical solution, by setting thermally sensitive expansion particles or thermal expansion plugs as thermally sensitive expansion blocking structures 8 within the cooling channel 7 and setting a trigger threshold of 100~150℃, the battery cell of this application can ensure the unobstructed flow of the cooling channel 7 at room temperature, maintaining the normal heat dissipation function of the battery cell. When local overheating occurs inside the battery cell and reaches the trigger threshold, this structure can rapidly expand and block the cooling channel 7, effectively blocking further heat transfer along the axial direction, thereby intervening in the early stage of thermal runaway and significantly reducing the risk of thermal runaway propagation. This design not only ensures the thermal management efficiency of the battery cell during normal operation but also provides critical safety protection in extreme cases, greatly improving the overall safety and reliability of lithium-ion battery cells.

[0075] In some of the embodiments described above in this application, although a cooling channel 7 is provided inside the battery cell for internal heat exchange, and a thermally conductive interface layer 9 is provided between the outer wall of the electrode assembly and the metal shell 1, how to effectively construct and coordinate the internal and external heat exchange paths to achieve efficient and balanced battery cell thermal management is still a technical problem that needs to be further clarified and optimized.

[0076] In this regard, this application further proposes that the thermal interface layer 9 is a highly thermally conductive flexible thermally conductive adhesive or thermally conductive pad, and the thermal interface layer 9 is filled between the outer wall of the electrode assembly and the inner wall of the metal shell 1 to construct an external heat exchange circuit; the cooling channel 7 constitutes an internal heat exchange circuit to form bidirectional heat exchange between the inside and outside of the battery cell.

[0077] Specifically, the thermally conductive interface layer 9 is a material used to fill the tiny gaps between two contact surfaces to reduce thermal resistance and improve heat transfer efficiency. As one implementation, the thermally conductive interface layer 9 can be a highly thermally conductive flexible adhesive with good flowability and adhesion, capable of forming a tightly bonded thermally conductive layer after curing, such as silicone thermally conductive adhesive or epoxy thermally conductive adhesive. Alternatively, the thermally conductive interface layer 9 can be a thermally conductive pad, typically made of composite materials such as silicone, graphite, or ceramic powder, possessing a certain degree of compressibility and flexibility, such as silicone thermally conductive pads or graphite thermally conductive pads. This thermally conductive interface layer 9 is disposed between the outer wall of the electrode assembly and the inner wall of the metal casing 1, its function being to ensure that the heat generated by the electrode assembly can be efficiently transferred to the metal casing 1. By filling the tiny gaps between them, the thermally conductive interface layer 9 significantly reduces contact thermal resistance, thereby constructing an external heat transfer path from the outer wall of the electrode assembly to the metal casing 1, i.e., an external heat exchange loop. Simultaneously, the cooling channel 7 is the main channel for heat dissipation from inside the battery cell. Its axially continuous structure allows the cooling medium to circulate within it, directly removing heat generated in the central region of the electrode assembly. Therefore, this cooling channel 7 constitutes the internal heat exchange loop of the battery cell, responsible for forced heat removal from the core area. Through the synergistic effect of the external and internal heat exchange loops, this solution aims to achieve bidirectional heat exchange within the battery cell. This means that the heat generated inside the battery cell can not only be dissipated inward through the central cooling channel 7, but also transferred outward to the metal casing 1 through the thermally conductive interface layer 9, thus forming a comprehensive and efficient thermal management system.

[0078] The following is a specific example. As a concrete implementation, the thermal interface layer 9 can be a silicon-based thermal pad with a thermal conductivity of 3.5 W / (m·K) and a thickness of 0.4 mm, precisely filled between the outer wall of the electrode assembly and the inner wall of the metal casing 1 to ensure tight contact and minimize thermal resistance. This thermal pad effectively conducts heat from the outer region of the electrode assembly to the metal casing 1, thus constructing an external heat exchange loop. Simultaneously, insulating cooling oil, such as synthetic ester coolant, can be circulated within the cooling channel 7 at a controllable flow rate (e.g., 120 ml / min) to directly remove heat from the central region of the electrode assembly, forming an internal heat exchange loop. During high-rate discharge of the battery cell, the internal cooling oil rapidly removes core heat, while the external thermal pad efficiently transfers peripheral heat to the casing. Together, they achieve overall temperature balance and efficient heat dissipation for the battery cell.

[0079] Through the above technical solution, the thermal interface layer 9 is defined as a highly thermally conductive flexible thermally conductive adhesive or thermally conductive pad, which is filled between the outer wall of the electrode assembly and the inner wall of the metal shell 1, thereby constructing an efficient external heat exchange circuit. Simultaneously, the cooling channel 7 is defined as an internal heat exchange circuit. This bidirectional heat exchange structure design allows the heat generated by the battery cell during operation to be dissipated simultaneously and efficiently through both internal and external paths, effectively avoiding heat accumulation inside the battery cell, especially the problem of excessive temperature difference between the central and peripheral areas. This not only significantly improves the overall heat dissipation efficiency and temperature uniformity of the battery cell, but also more effectively suppresses local overheating under extreme operating conditions, thereby enhancing the safety of the battery cell, extending its service life, and ensuring its performance stability.

[0080] In some other embodiments, this application proposes a lithium-ion battery cell, including a metal casing 1, a sealing cover 2, and a coaxially wound electrode assembly 3 housed within the casing. It also includes an adaptive composite hollow core tube 4, which is arranged along the winding center axis of the electrode assembly. The core tube 4 includes an inner thermally conductive substrate 5 and an elastic porous insulating outer layer 6 covering the inner thermally conductive substrate 5. An axially penetrating cooling channel 7 is provided inside the inner thermally conductive substrate 5. The core tube 4 has several micropores 10 on its wall to connect the cooling channel 7 with the electrode assembly layer. At least one set of thermosensitive expansion blocking structures 8 is axially arranged on the core tube 4. When the temperature reaches a trigger threshold, the thermosensitive expansion blocking structures 8 expand and partially or completely block the cooling channel 7. A thermally conductive interface layer 9 is provided between the outer wall of the electrode assembly and the metal casing 1. However, in practical applications, the electrodes of the lithium-ion battery cell undergo volume expansion and contraction during charging and discharging, which may lead to unstable contact pressure between the core tube 4 and the electrode assembly layer, thereby affecting heat transfer efficiency and the uniform distribution of the electrolyte.

[0081] In this regard, this application further proposes that the elastic porous insulating outer layer 6 of the composite hollow core tube 4 has a compressible rebound amount of 30% to 80%, and deforms synchronously with the expansion and contraction of the electrode during charging and discharging to maintain a constant pressure between the electrode layers.

[0082] The compressibility resilience of the elastic porous insulating outer layer 6 refers to its ability to recover its original shape after being deformed under external pressure, usually expressed as a percentage of deformation. This characteristic ensures that the elastic porous insulating outer layer 6 can be effectively compressed when subjected to electrode expansion and compression, and rebound when the electrode contracts, thus maintaining close contact with the electrode assembly layers at all times. This characteristic can be achieved by selecting polymer materials with high elastic modulus and good resilience, such as polyurethane foam or silicone rubber foam with specific formulations, and precisely controlling their pore structure and density; alternatively, it can be achieved by introducing highly elastic fiber or particulate reinforcement phases into the material to improve its overall compressibility resilience.

[0083] The elastic porous insulating outer layer 6 deforms synchronously with the expansion and contraction of the electrode during charging and discharging. This means that the outer layer can respond in real time to the volume changes generated by the electrode during charging and discharging, achieving synchronous deformation with the electrode. This ensures that a relatively constant contact pressure is maintained between the elastic porous insulating outer layer 6 and the electrode assembly layers throughout the entire cycle of electrode expansion and contraction. Synchronous deformation can be achieved by optimizing the material formulation and structural design of the elastic porous insulating outer layer 6 to give it low hysteresis and the ability to respond quickly to changes in external pressure; or by adjusting the thickness and porosity of the elastic porous insulating outer layer 6 so that it deforms in a manner matching the expansion and contraction rate of the electrode during pressure application and depressurization.

[0084] In one specific implementation, the elastic porous insulating outer layer 6 can be made of microporous polyurethane foam material, with its porosity and density precisely controlled to ensure a compressible resilience of approximately 40%. This polyurethane foam layer directly covers the outer side of the inner thermally conductive substrate 5. During the charging and discharging process of the battery cell, when the electrode expands, the polyurethane foam layer is elastically compressed by the electrode; when the electrode contracts, the foam layer recovers its deformation due to its inherent resilience, always maintaining close contact with the electrode. This continuous contact allows the electrode layers to maintain a constant pressure, for example, 0.15 MPa to 0.25 MPa, thereby ensuring that heat can be efficiently transferred from the electrode assembly to the cooling channel 7, while the electrolyte can also be uniformly distributed between the electrode layers.

[0085] Through the above technical solution, the contact pressure between the electrode and the core tube 4 is maintained stably during the charge-discharge cycle, effectively solving the problems of decreased heat transfer efficiency and uneven electrolyte distribution caused by changes in electrode volume. This significantly improves the heat dissipation efficiency and electrolyte utilization of the battery cell, thereby extending the battery cell's service life and enhancing its safety and reliability.

[0086] In other embodiments, this application proposes a heat exchange equalization method for lithium-ion battery cells, applicable to the aforementioned lithium-ion battery cells. The principle of this method is as follows: Figure 3 As shown, the method includes the following steps: A. Insulating cooling medium is introduced into the cooling channel 7 of the composite hollow core tube 4 to perform internal forced heat exchange in the central region of the electrode group; B. External heat exchange is performed on the outer wall region through the heat transfer interface layer of the outer wall of the electrode group, forming an internal and external bidirectional heat exchange network; C. During charging, the electrode expands and squeezes the elastic porous insulating outer layer 6, so that the interlayer redundant electrolyte enters the storage area of ​​the cooling channel 7 through the micropore 10; During discharging, the electrode contracts to form an interlayer negative pressure, and the electrolyte in the storage area seeps back to the interlayer of the electrode group through the micropore 10, realizing the dynamic self-balancing of the electrolyte; D. When the local temperature of the cell reaches the trigger threshold of the thermosensitive expansion blocking structure 8, the thermosensitive structure expands and blocks the cooling channel 7, blocking the axial propagation of thermal runaway.

[0087] The core innovation of this embodiment lies in the fact that by combining the thermal expansion blocking structure 8 with the electrolyte dynamic self-balancing mechanism in a synergistic manner, the cooling channel 7 is automatically blocked to prevent heat spread and maintain electrolyte balance under thermal runaway conditions.

[0088] This application further proposes that the cooling medium in the cooling channel 7 is insulating oil, deionized water or ethylene glycol aqueous solution, and the flow rate of the cooling medium is adjustable so that the radial temperature difference of the electrode group is ≤5℃ under fast charging conditions.

[0089] The cooling medium within cooling channel 7 can be insulating oil, deionized water, or an ethylene glycol aqueous solution. Insulating oil is a liquid with good electrical insulation and thermal conductivity. Its advantages include non-conductivity, preventing short circuits with the internal circuitry of the battery cell, and a high boiling point and thermal stability, making it suitable for high-temperature environments. Deionized water is specially treated water to remove ionic impurities. It has good thermal conductivity and low cost, and its advantages include being non-toxic, environmentally friendly, and having a high specific heat capacity, enabling efficient heat absorption. Ethylene glycol aqueous solution is a mixture of ethylene glycol and water, commonly used in cooling systems as an antifreeze and heat transfer medium. Its advantages include a low freezing point and a high boiling point, widening the operating temperature range of the cooling system while maintaining good thermal conductivity. The selection of these cooling media aims to ensure efficient heat removal during forced heat exchange within the battery cell, while also guaranteeing the battery cell's electrical safety and long-term stability. Adjustable cooling medium flow rate means that the flow velocity of the cooling medium within cooling channel 7 can be dynamically adjusted according to actual needs. Adjustable flow rate can be achieved through methods including, but not limited to: controlling the circulation flow rate of the cooling medium via a variable frequency pump, or adjusting the local resistance of the cooling channel 7 by regulating valves to control the flow rate. The purpose of adjustable flow rate is to precisely control the cooling intensity according to different operating states and heat generation of the battery cell, achieving optimal temperature management. "Fast charging mode" refers to the operating mode in which the battery cell charges at a high current for a short period, during which the internal heat generation of the battery cell is large and rapid. "Polar group radial temperature difference" refers to the temperature difference of the battery cell's pole group along the radial direction (from the center to the periphery). The goal of controlling the radial temperature difference to ≤5℃ aims to ensure that the internal temperature distribution of the battery cell is as uniform as possible under extreme conditions such as fast charging. A smaller radial temperature difference helps avoid localized overheating, thereby improving the charging efficiency of the battery cell, extending cycle life, and reducing the risk of thermal runaway.

[0090] This application's solution optimizes the thermal management of the battery cell under fast charging conditions by precisely selecting and controlling the flow rate of the cooling medium within the cooling channel 7. During fast charging, the high current density and rapid electrochemical reaction generate a large amount of heat inside the battery cell, with the heat generation in the central region typically exceeding that in the peripheral region, easily leading to a significant radial temperature difference. To effectively address this challenge, this solution first selects insulating oil, deionized water, or an aqueous ethylene glycol solution as the cooling medium. These media all possess excellent thermal conductivity and electrical insulation, ensuring efficient heat transfer without causing electrical safety issues during heat exchange with the electrode layers through the micropores 10. Furthermore, by dynamically adjusting the flow rate of the cooling medium, the cooling intensity can be adjusted in real time according to changes in the cell's heat generation rate and distribution during fast charging. For example, when a rapid temperature increase is detected in the central region of the battery cell, the flow rate of the cooling medium can be appropriately increased to enhance the heat exchange efficiency in the central region, thereby removing heat more quickly. This adjustable flow rate cooling mechanism is closely integrated with the internal forced heat exchange step A in the above method, which is carried out through the cooling channel 7 of the composite hollow core tube 4, forming a rapidly responding and precisely controlled internal thermal management system. In this way, the radial temperature difference inside the electrode assembly during fast charging can be effectively suppressed and kept within 5°C, thereby avoiding performance degradation and safety hazards caused by local overheating.

[0091] In one specific implementation, insulating oil can be circulated within the cooling channel 7 as a cooling medium. This insulating oil is transported through a circulation system driven by a variable frequency pump. During fast charging of the battery cell, the battery management system (BMS) monitors the temperature distribution inside the cell in real time, particularly the temperature of the central and peripheral regions of the electrode assembly. When the BMS detects a tendency for the radial temperature difference of the electrode assembly to exceed 5°C, it immediately sends a command to the variable frequency pump to increase the circulation rate of the insulating oil. For example, the flow rate can be increased from the initial 0.5 L / min to 1.0 L / min to enhance the cooling channel 7's ability to remove heat from the central region. Simultaneously, the micropores 10 on the wall of the cooling channel 7 continuously transfer heat from the cooling medium to the interlayer of the electrode assembly and absorb heat from the interlayer. Through this dynamic adjustment, even under continuous high-power fast charging conditions, the radial temperature difference of the electrode assembly can be stably controlled within 5°C, ensuring uniform temperature across all parts of the battery cell, thereby guaranteeing the performance and safety of the battery cell.

[0092] Through the above technical solution, this application effectively solves the problem of excessive radial temperature difference in the electrode assembly caused by large and uneven heat generation and distribution within the lithium-ion battery cell under fast charging conditions. By selecting a cooling medium with good thermal conductivity and insulation properties, combined with an adjustable flow rate cooling mechanism, the intensity of forced heat exchange can be precisely controlled according to the actual heat generation of the battery cell. This allows the radial temperature difference of the electrode assembly to be strictly controlled within 5°C during fast charging, significantly improving the temperature uniformity of the battery cell under extreme conditions. This precise temperature management not only helps improve fast charging efficiency and reduce charging time, but also effectively suppresses local overheating, thereby extending the cycle life of the battery cell, reducing the risk of thermal runaway, and improving the overall safety and reliability of the battery cell.

[0093] The above are merely embodiments of this application and are not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for equalizing heat exchange in a lithium-ion battery cell, characterized in that, A lithium-ion battery cell includes a metal casing, a sealing cover, and a coaxially wound electrode assembly housed within the casing. The lithium-ion battery cell also includes an adaptive composite hollow core tube, which is arranged along the winding center axis of the electrode assembly. The core tube includes an inner thermally conductive substrate and an elastic porous insulating outer layer covering the inner thermally conductive substrate. The inner thermally conductive substrate has an axially penetrating cooling channel. The core tube wall has several micropores to connect the cooling channel and the electrode assembly layer. At least one set of thermosensitive expansion blocking structures is axially arranged on the core tube. When the temperature reaches a trigger threshold, the thermosensitive expansion blocking structures expand and partially or completely block the cooling channel. A thermally conductive interface layer is provided between the outer wall of the electrode assembly and the metal casing. The specific process of heat exchange in the lithium-ion battery cell is as follows: A. Insulating cooling medium is introduced into the cooling channel of the composite hollow core tube to perform internal forced heat exchange in the central region of the electrode assembly; B. External heat exchange is carried out on the outer wall area through the heat transfer interface layer of the outer wall of the electrode group, forming a two-way heat exchange network inside and outside; C. During charging, the electrode expands and squeezes the elastic porous insulating outer layer, allowing the redundant electrolyte between the layers to enter the cooling channel storage area through the micropores; during discharging, the electrode contracts to form a negative pressure between the layers, and the electrolyte in the storage area seeps back into the electrode layer through the micropores, realizing the dynamic self-balancing of the electrolyte. D. When the local temperature of the battery cell reaches the trigger threshold of the thermal expansion blocking structure, the thermal structure expands and blocks the cooling channel, thus preventing the axial propagation of thermal runaway. The cooling medium in the cooling channel is insulating oil, deionized water, or an aqueous solution of ethylene glycol.

2. The heat exchange equalization method for lithium-ion cells according to claim 1, characterized in that, The inner thermally conductive substrate is a thin-walled tubular structure made of copper, aluminum, or copper-aluminum alloy, and the elastic porous insulating outer layer is a porous material made of polyurethane, polyolefin, or fluororubber, with a thickness of 0.3~1.5mm and a porosity of 30%~70%.

3. The heat exchange equalization method for lithium-ion cells according to claim 1, characterized in that, The micropores on the core tube wall are distributed along the core tube axis. The micropore diameter on the side facing the bottom of the electrode group is smaller than that on the side facing the top of the electrode group. The micropore diameter ranges from 20 to 100 μm.

4. The heat exchange equalization method for lithium-ion cells according to claim 1, characterized in that, The micropores of the elastic porous insulating outer layer can store excess electrolyte and, under negative pressure between electrode layers, seep back into the electrode group through the micropores.

5. The heat exchange equalization method for lithium-ion cells according to claim 1, characterized in that, The thermal expansion blocking structure includes thermal expansion particles or thermal expansion plugs disposed in the cooling channel, with a trigger threshold of 100~150℃, and does not block or partially blocks the cooling channel at room temperature to retain the flow cross section of the cooling medium.

6. The heat exchange equalization method for lithium-ion cells according to claim 1, characterized in that, The thermal interface layer is a highly thermally conductive flexible thermal adhesive or thermally conductive pad. The thermal interface layer is filled between the outer wall of the electrode assembly and the inner wall of the metal shell to form an external heat exchange circuit. The cooling channel forms an internal heat exchange circuit to form bidirectional heat exchange between the inside and outside of the battery cell.

7. The heat exchange equalization method for lithium-ion cells according to claim 1, characterized in that, The composite hollow core tube has an elastic porous insulating outer layer with a compressible resilience of 30% to 80%, and deforms synchronously with the expansion and contraction of the electrode during charging and discharging to maintain constant pressure between the electrode layers.

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