Composite phase change material battery thermal management system with bidirectional temperature control function, method and battery pack

Abstract

The invention discloses a composite phase change material battery thermal management system with bidirectional temperature control, a method and a battery pack, and relates to the technical field of battery thermal management. The battery thermal management system comprises a battery module, a composite phase change temperature control module and a control module, the composite phase change temperature control module tightly wraps the surface of the battery module, and the control module monitors temperature data of the battery module, performs mode switching according to the temperature data and sends a temperature control signal; and the composite phase change temperature control module regulates the temperature of the battery module according to the temperature control signal. Bidirectional temperature control of the battery is achieved, the regulation and control precision of the battery operation temperature is improved, the service life of the battery is effectively prolonged, and stable and safe operation of the battery is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of battery thermal management technology, and in particular to a thermal management system, method and battery pack for composite phase change material batteries that also have bidirectional temperature control. Background Technology

[0002] With the continuous improvement of battery energy density and power density, the heat generation problem during operation has become increasingly prominent. Battery performance, lifespan, and safety are highly sensitive to temperature, and optimal efficiency is achieved when operating within the suitable temperature range of 20-40℃. Phase change materials (PCMs) are widely used in battery thermal management due to their advantages such as high latent heat of phase change and passive temperature control requiring no additional energy consumption. However, current technologies still have many shortcomings: Traditional PCMs have low thermal conductivity (typically ≤0.5W / (m·K)). Even with the addition of thermally conductive fillers, it is difficult to balance heat transfer efficiency and thermal energy density, leading to easy heat dissipation saturation under high-temperature conditions and an inability to effectively suppress local hot spots. Secondly, existing PCM thermal management systems mostly focus on a single heat dissipation function, requiring external heating devices in low-temperature environments, resulting in uneven heating and high energy consumption. Furthermore, the phase change hysteresis of PCMs themselves further affects heating efficiency. In addition, phase change materials undergo a 10%–15% volume expansion during the solid-liquid transition. If the encapsulation design is not reasonable, leakage can easily occur. At the same time, traditional encapsulation structures increase contact thermal resistance, affecting temperature control performance.

[0003] Therefore, there is an urgent need for a device or system that can achieve both efficient and uniform heat dissipation and uniform battery heating, in order to solve the problems existing in the prior art, extend battery life, and reduce energy consumption. Summary of the Invention

[0004] In view of this, the present invention provides a composite phase change material battery thermal management system, method and battery pack with bidirectional temperature control, which realizes the integration of battery heat dissipation and cooling functions, improves the control accuracy of battery operating temperature, controls the battery to work in a suitable temperature range, effectively extends battery life and ensures stable and safe battery operation.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A thermal management system for a composite phase change material battery with bidirectional temperature control includes: a battery module, a composite phase change temperature control module, and a control module; The control module is connected to the battery module and the composite phase change temperature control module respectively, and the composite phase change temperature control module is tightly wrapped around the surface of the battery module. The control module is used to monitor the temperature data during the operation of the battery module, switch modes according to the temperature data, and send temperature control signals. The composite phase change temperature control module is used to regulate the temperature of the battery module according to the temperature control signal.

[0006] The above-mentioned system, optionally, includes a composite phase change temperature control module comprising a thermally conductive contact layer, a gradient phase change energy storage layer, an intelligent electrothermal conversion layer, and a thermal insulation and protection layer stacked in sequence.

[0007] Optionally, the thermally conductive contact layer of the above system is made of silicone-based composite material, and the surface has a microgroove structure distributed in a spiral pattern.

[0008] Optionally, the gradient phase change energy storage layer is characterized by adopting a two-stage phase change structure; the inner layer of the gradient phase change energy storage layer is a low-melting-point phase change matrix composed of paraffin wax and polyethylene glycol according to a first preset mass ratio, and the outer layer is a high-melting-point phase change matrix composed of stearic acid and pentaerythritol according to a second preset mass ratio; both layers are filled with graphene-carbon nanotube composite thermally conductive filler.

[0009] The above-described system may optionally include a smart electrothermal conversion layer comprising a flexible polyimide heating film and a porous aerogel, wherein the flexible polyimide heating film is embedded in a porous aerogel carrier in a combined structure.

[0010] Optionally, the thermal insulation layer of the above system may be made of flame-retardant polyurethane foam and coated with a hydrophobic coating.

[0011] Optionally, the battery thermal management system described above may further include: an auxiliary heat dissipation / heating module; The auxiliary heat dissipation / heating module includes: a graded air duct, a micro fan, and a pulse heating trigger submodule; the graded air duct is formed on the surface of the thermal insulation layer, the micro fan is connected to the control module, and the pulse heating trigger submodule is connected to the control module and the intelligent electrothermal conversion layer; The control module is also used to: when switching to heat dissipation mode, control the micro fan to start, accelerate the temperature dissipation of the composite phase change temperature control module surface through the graded air duct, and dissipate heat for the battery module; when switching to heating mode, control the pulse heating trigger submodule to emit pulse signals, and the intelligent electrothermal conversion layer triggers the sliding enhanced heat transfer mechanism according to the pulse signals to heat the battery module.

[0012] The above system may optionally include a control module comprising a temperature sensor array, a main control chip, and a drive circuit. The battery module includes multiple battery cells of the same specifications. The composite phase change temperature control module includes the same number of composite phase change temperature control units. The composite phase change temperature control units are connected by snap-fit. The surface of each battery cell is tightly covered with a composite phase change temperature control unit. The temperature sensor array has a sampling point every 2-4 battery cells.

[0013] A thermal management method for a composite phase change material battery with bidirectional temperature control, applied to a thermal management system for a composite phase change material battery with bidirectional temperature control as described in any one of the above claims, comprising: S1. Data monitoring steps: Monitor the temperature data during the operation of the battery module; S2, Mode Switching Steps: Switch modes based on temperature data. When the temperature data is less than the first threshold, switch to heating mode and execute S3; when the temperature data is greater than the first threshold but less than the second threshold, switch to heat preservation mode and execute S4; when the temperature data is greater than the second threshold, switch to heat dissipation mode and execute S5. S3. Heating and temperature rise step: Send a temperature rise control signal, and the composite phase change temperature control module triggers the sliding enhanced heat transfer mechanism to heat the battery module according to the temperature rise control signal; S4. Insulation Step: The composite phase change temperature control module controls the temperature of the battery module to maintain balance according to the gradient phase change control. S5. Heat dissipation and cooling steps: Send a cooling control signal, and the composite phase change temperature control unit cools the battery module according to the cooling control signal.

[0014] A battery pack includes: at least one battery module; and a composite phase change material battery thermal management system with bidirectional temperature control as described in any of the preceding claims, wherein the composite phase change temperature control module covers the surface of the battery cells in the battery module; the battery modules in the battery pack are arranged in accordance with the direction of the graded air duct.

[0015] As can be seen from the above technical solution, compared with the prior art, the present invention provides a composite phase change material battery thermal management system, method, and battery pack with bidirectional temperature control, which has the following beneficial effects: (1) Bidirectional precise temperature control: Through the synergistic design of gradient phase change and intelligent electrothermal conversion layer, the temperature control coverage in the environment of -30℃~60℃ is achieved, so that the battery working temperature is stable at 20-40℃ and the temperature difference of a single cell is ≤3℃, which meets the temperature control requirements of high energy density batteries. (2) Significantly improved heat transfer efficiency: By adopting composite thermally conductive filler modification and slip-enhanced heat transfer mechanism, the phase thermal conductivity is increased by more than 5 times, the low temperature heating rate is increased by 40%, and the high temperature heat dissipation saturation time is extended by 2 times, effectively suppressing the occurrence of local hot spots during battery operation; (3) Low energy consumption and compact structure: In the heat preservation mode, the composite phase change temperature control module controls the battery temperature according to the gradient phase change to maintain the basic temperature control, without the need for additional power. The auxiliary components are only activated under extreme conditions, reducing the system energy consumption by 35%. The integrated composite structure is only 3-8mm thick, which does not affect the energy density of the battery pack. (4) High reliability and adaptability: The flame-retardant and heat-insulating design of the composite phase change temperature control module improves the safety of system operation, and expansion space is reserved between each sub-unit to avoid leakage risk. The hydrophobic coating enhances the system's environmental adaptability and can be applied to battery systems in different scenarios such as power batteries and energy storage power station batteries. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 This is a physical structural diagram of a composite phase change material battery thermal management system with bidirectional temperature control disclosed in an embodiment of the present invention; Figure 2 This is a physical structural diagram of the composite phase change temperature control module disclosed in an embodiment of the present invention; Figure 3 This is a schematic diagram of a thermal management method for a composite phase change material battery with bidirectional temperature control disclosed in this invention. Among them, 1-micro fan, 2-graded air duct, 3-thermal insulation layer, 4-intelligent electrothermal conversion layer, 5-gradient phase change energy storage layer, 6-thermal conductive contact layer, 7-upper shell, 8-control module, 9-control module bracket, 10-composite phase change temperature control module, 11-battery module, 12-bottom shell. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0020] Reference Figure 1 The present invention discloses a thermal management system for a composite phase change material battery with bidirectional temperature control, comprising: a battery module 11, a composite phase change temperature control module 10, and a control module 8.

[0021] The control module 8 is connected to the battery module 11 and the composite phase change temperature control module 10 respectively, and the composite phase change temperature control module 10 is tightly wrapped around the surface of the battery module 11.

[0022] Control module 8 is used to monitor the temperature data during the operation of the battery module, switch modes according to the temperature data, and send temperature control signals.

[0023] The composite phase change temperature control module 10 is used to regulate the temperature of the battery module 11 according to the temperature control signal.

[0024] Optionally, the temperature control signal includes a heating control signal and a cooling control signal.

[0025] Depend on Figure 1 The present invention discloses a specific structure for a composite phase change material battery thermal management system with bidirectional temperature control. The battery thermal management system's housing is composed of an upper shell 7 and a bottom shell 12. Inside the housing, from top to bottom, are arranged a control module 8, a control module support 9, a composite phase change temperature control module 10, and a battery module 11. The composite phase change temperature control module 10 tightly covers the surfaces of each individual cell of the battery module 11. The above-described specific structure and arrangement are specific implementations of the disclosed solution. It is readily apparent that the present invention, through a simple integrated housing, can obtain a power supply battery with built-in temperature regulation. Furthermore, this power supply management system not only has high integration but also strong environmental adaptability, making it suitable for battery systems in different scenarios such as power batteries and energy storage power station batteries.

[0026] Reference Figure 2The composite phase change temperature control module 10 includes a thermally conductive contact layer 6, a gradient phase change energy storage layer 5, an intelligent electrothermal conversion layer 4, and a thermal insulation and protection layer 3, which are stacked in sequence. The layers are combined into one piece by a co-extrusion molding process, with a total thickness of 3-8mm.

[0027] This invention creatively proposes an integrated structure of a composite phase change temperature control module 10, which consists of a thermally conductive contact layer 6, a gradient phase change energy storage layer 5, an intelligent electrothermal conversion layer 4, and a thermal insulation and protection layer 3, from the inside out. Each layer works together to achieve bidirectional temperature control.

[0028] Optionally, the thermally conductive contact layer 6 is made of silicone-based composite material, with a spirally distributed microgroove structure on the surface, the groove depth being 0.2-0.5 mm and the width being 0.5-1 mm.

[0029] The thermally conductive contact layer 6 is made of silicone-based composite material with 3wt% boron nitride micro powder added, which improves the thermal conductivity of the thermally conductive layer to ≥3.0W / (m·K) and the compression resilience to ≥85%, thus enhancing the performance of the thermally conductive contact layer 6. At the same time, the spiral microgroove structure on the surface of the thermally conductive contact layer 6 can reduce the contact gap, lower the contact thermal resistance, and accommodate the volume expansion of the phase change material.

[0030] Optionally, the gradient phase change energy storage layer 5 adopts a two-stage phase change structure. The inner layer of the gradient phase change energy storage layer 5 is a low-melting-point phase change matrix composed of paraffin wax and polyethylene glycol according to a first preset mass ratio, and the outer layer is a high-melting-point phase change matrix composed of stearic acid and pentaerythritol according to a second preset mass ratio. Both layers are filled with 5-10 wt% graphene-carbon nanotube composite thermally conductive filler with a thermal conductivity ≥2.5 W / (m·K). The melting point temperature of the inner phase change matrix is ​​28-32℃, and the melting point temperature of the outer phase change matrix is ​​38-42℃.

[0031] The gradient phase change energy storage layer 5 adopts a two-stage phase change system. The inner low-melting-point PCM (Phase Change Material) quickly absorbs the heat generated by the battery operation, while the outer high-melting-point PCM further expands the heat dissipation capacity under high-temperature conditions. Combined with graphene-carbon nanotube composite thermally conductive filler, the thermal conductivity is increased to 2.5-5.0 W / (m·K), which can solve the problem of poor thermal conductivity of traditional PCM and ensure that the battery module 11 can quickly dissipate heat and cool down during operation, keeping the battery module 11 at a constant temperature within a safe temperature range.

[0032] Optionally, the intelligent electrothermal conversion layer 4 comprises a flexible polyimide heating film and a porous aerogel, forming a combined structure in which the flexible polyimide heating film is embedded within a porous aerogel carrier. The aerogel has a pore size of 10-100 nm and a thermal conductivity of 0.01-0.05 W / (m·K); the heating film power density is infinitely adjustable within the range of 0.3-1.0 W / cm², and it possesses self-limiting temperature characteristics, with a maximum operating temperature ≤60℃.

[0033] The intelligent electrothermal conversion layer 4 embeds a flexible heating film into a porous aerogel. The ultra-low thermal conductivity of the aerogel can reduce heat loss and improve heating efficiency. At the same time, the self-limiting temperature characteristics of the heating film prevent local overheating of the battery module 11, enabling rapid and uniform heating of the battery module 11 in low-temperature environments and keeping the battery operating at a constant temperature within a safe temperature range.

[0034] Optionally, the thermal insulation layer 3 is made of flame-retardant polyurethane foam and coated with a hydrophobic coating. Specifically, the thermal insulation layer 3 is made of flame-retardant polyurethane foam with an oxygen index ≥32% and a hydrophobic coating with a water contact angle ≥120°.

[0035] The thermal insulation layer 3 uses flame-retardant polyurethane foam combined with a hydrophobic coating to prevent PCM leakage and reduce the impact of ambient temperature on the battery. At the same time, it reserves space for volume expansion, improving the stability of the integrated structure of the composite phase change temperature control module 10.

[0036] Optionally, the battery thermal management system may further include an auxiliary heat dissipation / heating module.

[0037] Combination Figure 2 The auxiliary heat dissipation / heating module includes: a graded air duct 2, a micro fan 1, and a pulse heating trigger submodule (not shown in the figure); the graded air duct 2 is formed on the surface of the thermal insulation layer 3, the micro fan 1 is connected to the control module 8, and the pulse heating trigger submodule is connected to the control module 8 and the intelligent electrothermal conversion layer 4.

[0038] The control module 8 is also used to: when switching to the heat dissipation mode, control the micro fan 1 to start, accelerate the dissipation of surface temperature of the composite phase change temperature control module 10 through the graded air duct 2, and dissipate heat for the battery module 11; when switching to the heating mode, control the pulse heating trigger submodule to emit a pulse signal, and the intelligent electrothermal conversion layer 4 triggers the sliding enhanced heat transfer mechanism according to the pulse signal to heat the battery module 11.

[0039] Combination Figure 2 As can be seen, the auxiliary structure of the present invention is a specific implementation scheme that combines the sliding enhanced heat transfer mechanism with the graded air duct, which is further disclosed in the present invention, and provides theoretical support and implementation basis for temperature control of battery operation.

[0040] To further improve the heat transfer efficiency of the battery module 11 during the heating and cooling process, this invention introduces a slip-enhanced intimate contact melting (SCCM) mechanism. A short pulse voltage of 5-12V and a pulse width of 0.5-2s are applied to the intelligent electrothermal conversion layer 4 through a pulse heating trigger submodule, forming a thin liquid film between the PCM and the thermally conductive contact layer 6. This reduces solid-liquid interface friction, promotes the free sinking of the solid PCM, and maintains a close contact melting state, resulting in an effective thermal resistance reduction of more than 50%. At the same time, a graded air duct 2 with a width of 5-10mm is designed on the surface of the thermal insulation layer 3, consistent with the module layout. The air duct has parabolic guide protrusions inside, which, together with the micro fan 1, form forced convection. When the PCM reaches phase change saturation, the heat is quickly discharged, extending the heat dissipation time.

[0041] Optionally, the micro fan 1 is a stepless speed-regulating centrifugal fan with an air volume range of 50-200 m³ / h. It only starts when the composite phase change material reaches the phase change saturation state, and its energy consumption is ≤5W.

[0042] Optionally, the control module 8 includes a temperature sensor array, a main control chip, and a drive circuit; the battery module 11 includes multiple battery cells of the same specifications; the composite phase change temperature control module 10 includes the same number of composite phase change temperature control units, and the composite phase change temperature control units are connected by a snap-fit ​​mechanism; the surface of each battery cell is tightly covered with a composite phase change temperature control unit; the temperature sensor array has a sampling point every 2-4 battery cells.

[0043] The control module 8 collects the battery temperature and PCM temperature status in real time through a temperature sensor array, and automatically switches between three modes: heat dissipation, heating, and heat preservation based on a PID algorithm. In low-temperature environments, pulse heating triggers the SCCM mechanism to quickly raise the battery temperature to a suitable range. Under normal operating conditions, the control module 8 monitors the temperature data of the battery module 11 and is in standby mode. The battery thermal management system passively controls the temperature only through the gradient PCM, without requiring additional energy consumption. Under high-temperature conditions, the graded air duct and PCM work together to dissipate heat and ensure that the temperature does not exceed the standard.

[0044] The main control chip is based on a PID algorithm and automatically switches between three operating modes according to the temperature data collected by the temperature sensor array: Heat dissipation mode: When the temperature of the battery module 11 is >38℃, the micro fan 1 is activated, and the heat dissipation of the composite phase change temperature control module 10, which is made of composite phase change material and tightly wrapped around the battery module 11, is accelerated through the graded air duct 2, so as to reduce the temperature of the battery module 11.

[0045] Heating mode: When the temperature of battery module 11 is <10℃, the main control chip activates the intelligent electrothermal conversion layer 4 and adopts a pulse heating trigger sliding enhanced heat transfer mechanism to make the solid phase change material melt quickly and come into close contact with the surface of battery module 11, thereby increasing the battery temperature through the current thermal effect.

[0046] Insulation mode: When the temperature of the battery module 11 is between 10-38℃, the main control chip is in standby mode. In this embodiment of the invention, the temperature is passively controlled only by the composite phase change temperature control module 10, without the need to start auxiliary components.

[0047] In the above embodiments, the composite phase change temperature control units are connected by a snap-fit ​​mechanism, with space reserved for volume expansion. The embodiments disclosed in this invention, by reserving 10%-15% volume expansion space, accommodate the volume changes during the solid-liquid transition of the phase change material, avoiding leakage risks and improving the stability and safety of system operation.

[0048] To achieve the integration of battery heat dissipation and cooling functions and improve the control accuracy of battery operating temperature, refer to Figure 3 This invention also discloses a thermal management method for composite phase change material batteries with bidirectional temperature control, applicable to, for example... Figure 1 The thermal management system for a composite phase change material battery, which also features bidirectional temperature control, includes: S1. Data monitoring steps: Monitor the temperature data of battery module 11 during operation.

[0049] S2. Mode switching steps: Switch modes according to temperature data. When the temperature data is less than the first threshold, switch to heating mode and execute S3; when the temperature data is greater than the first threshold and less than the second threshold, switch to heat preservation mode and execute S4; when the temperature data is greater than the second threshold, switch to heat dissipation mode and execute S5.

[0050] S3. Heating and temperature rise step: Sending a temperature rise control signal, the composite phase change temperature control module 10 triggers the sliding enhanced heat transfer mechanism to heat the battery module 11 according to the temperature rise control signal.

[0051] S4. Insulation Step: The composite phase change temperature control module 10 controls the temperature of the battery module 11 to maintain balance according to the gradient phase change control.

[0052] S5. Heat dissipation and cooling steps: Send a cooling control signal, and the composite phase change temperature control module 10 cools the battery module 11 according to the cooling control signal.

[0053] Optionally, the first threshold is 10℃ and the second threshold is 38℃.

[0054] Combination Figure 3As can be seen, after the battery thermal management system starts running, the control module 8 monitors the temperature data of the battery in real time. When the temperature data changes, the control module 8 can react in time, and the battery thermal management system takes corresponding measures to ensure that the battery operates stably in the range of 20-40℃. This prevents the risk of fire due to excessively high temperature, and also prevents the battery from being affected by excessively low temperature.

[0055] A battery pack includes: at least one battery module; and a composite phase change material battery thermal management system with bidirectional temperature control as described in any of the above embodiments, wherein the composite phase change temperature control module covers the surface of the battery cells in the battery module; the battery modules in the battery pack are arranged in the same direction as the graded air duct, forming an "upward inlet and downward outlet" airflow channel.

[0056] This application proposes a composite phase change material battery thermal management system, method, and battery pack with bidirectional temperature control. Through an integrated design of a gradient phase change energy storage layer, an intelligent electrothermal conversion layer, and a porous thermal conductivity enhancement structure, it solves the technical pain points of traditional PCM thermal management technology, such as low thermal conductivity, inability to actively heat at low temperatures, and heat dissipation saturation at high temperatures. In this embodiment, the composite phase change material adopts an organic-inorganic composite system. The thermal conductivity is improved to 2.5-5.0 W / (m·K) through modification with nano-thermal conductive fillers, while the latent heat of phase change is maintained at 180-220 J / g. Combined with a pulse heating-triggered slip-enhanced heat transfer mechanism and a graded airflow design, precise temperature control of the battery pack is achieved in environments ranging from -30℃ to 60℃. Experimental verification shows that the battery thermal system disclosed in this embodiment can stabilize the battery operating temperature at 20-40℃, with a single-cell temperature difference ≤3℃, a low-temperature heating rate increased by more than 40%, and a high-temperature heat dissipation saturation time extended by 2 times. Furthermore, no additional power is required to maintain basic temperature control, resulting in a 35% reduction in energy consumption. This system is suitable for high-energy-density power batteries and energy storage battery systems.

[0057] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A thermal management system for a composite phase change material battery with bidirectional temperature control, characterized in that, include: Battery module, composite phase change temperature control module and control module; The control module is connected to the battery module and the composite phase change temperature control module respectively, and the composite phase change temperature control module is tightly wrapped around the surface of the battery module. The control module is used to monitor the temperature data during the operation of the battery module, switch modes according to the temperature data, and send temperature control signals. The composite phase change temperature control module is used to regulate the temperature of the battery module according to the temperature control signal.

2. The thermal management system for a composite phase change material battery with bidirectional temperature control according to claim 1, characterized in that, The composite phase change temperature control module includes a thermally conductive contact layer, a gradient phase change energy storage layer, an intelligent electrothermal conversion layer, and a thermal insulation and protection layer stacked in sequence.

3. A thermal management system for a composite phase change material battery with bidirectional temperature control as described in claim 2, characterized in that, The thermally conductive contact layer is made of silicone-based composite material, and the surface has a spirally distributed microgroove structure.

4. A thermal management system for a composite phase change material battery with bidirectional temperature control as described in claim 2, characterized in that, The gradient phase change energy storage layer adopts a two-stage phase change structure; the inner layer of the gradient phase change energy storage layer is a low-melting-point phase change matrix, which is composed of paraffin and polyethylene glycol according to a first preset mass ratio, and the outer layer is a high-melting-point phase change matrix, which is composed of stearic acid and pentaerythritol according to a second preset mass ratio; both layers are filled with graphene-carbon nanotube composite thermally conductive filler.

5. A thermal management system for a composite phase change material battery with bidirectional temperature control as described in claim 2, characterized in that, The intelligent electrothermal conversion layer comprises a flexible polyimide heating film and a porous aerogel, which is a combined structure in which the flexible polyimide heating film is embedded in a porous aerogel carrier.

6. A thermal management system for a composite phase change material battery with bidirectional temperature control as described in claim 2, characterized in that, The thermal insulation layer is made of flame-retardant polyurethane foam and has a hydrophobic coating on the surface.

7. A thermal management system for a composite phase change material battery with bidirectional temperature control as described in claim 2, characterized in that, The battery thermal management system also includes an auxiliary heat dissipation / heating module; The auxiliary heat dissipation / heating module includes: a graded air duct, a micro fan, and a pulse heating trigger submodule; the graded air duct is formed on the surface of the thermal insulation layer, the micro fan is connected to the control module, and the pulse heating trigger submodule is connected to the control module and the intelligent electrothermal conversion layer; The control module is also used to: when switching to heat dissipation mode, control the micro fan to start, accelerate the temperature dissipation of the composite phase change temperature control module surface through the graded air duct, and dissipate heat for the battery module; when switching to heating mode, control the pulse heating trigger submodule to emit pulse signals, and the intelligent electrothermal conversion layer triggers the sliding enhanced heat transfer mechanism according to the pulse signals to heat the battery module.

8. A thermal management system for a composite phase change material battery with bidirectional temperature control as described in claim 1, characterized in that, The control module includes a temperature sensor array, a main control chip, and a drive circuit. The battery module includes multiple battery cells of the same specifications. The composite phase change temperature control module includes the same number of composite phase change temperature control units. The composite phase change temperature control units are connected by snap-fit. The surface of each battery cell is tightly covered with a composite phase change temperature control unit. The temperature sensor array has a sampling point every 2-4 battery cells.

9. A thermal management method for composite phase change material batteries with both bidirectional temperature control, characterized in that, A thermal management system for a composite phase change material battery with bidirectional temperature control as described in any one of claims 1-8, comprising: S1. Data monitoring steps: Monitor the temperature data during the operation of the battery module; S2, Mode Switching Steps: Switch modes based on temperature data. When the temperature data is less than the first threshold, switch to heating mode and execute S3; when the temperature data is greater than the first threshold but less than the second threshold, switch to heat preservation mode and execute S4; when the temperature data is greater than the second threshold, switch to heat dissipation mode and execute S5. S3. Heating and temperature rise step: Send a temperature rise control signal, and the composite phase change temperature control module triggers the sliding enhanced heat transfer mechanism to heat the battery module according to the temperature rise control signal; S4. Insulation Step: The composite phase change temperature control module controls the temperature of the battery module to maintain balance according to the gradient phase change control. S5. Heat dissipation and cooling steps: Send a cooling control signal, and the composite phase change temperature control unit cools the battery module according to the cooling control signal.

10. A battery pack, characterized in that, include: At least one battery module; And a composite phase change material battery thermal management system with bidirectional temperature control as described in any one of claims 1-8, wherein the composite phase change temperature control module is wrapped around the surface of the battery cell in the battery module; the battery module arrangement in the battery pack is consistent with the direction of the graded air duct.

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