Double-temperature-zone phase-change flexible thermal management film and three-dimensional micro-channel system and all-weather application thereof

Abstract

The invention discloses a double-temperature-zone phase-change flexible thermal management film and a three-dimensional micro-channel system and all-weather application thereof, and belongs to the technical field of new energy automobile battery thermal management. The core of the system is a highly-integrated composite flexible film (105) which adopts a sandwich structure of a high-temperature phase change material layer (108a), a snakelike micro-channel (109) and a low-temperature phase change material layer (108b) and is communicated with a battery gap water cooling pipe (102) through a laser through hole (110) to form a three-dimensional heat dissipation network. The system is externally connected with an intelligent water sump (301) and an air cooling device (201), and self-adaptive switching of three modes of low-temperature preheating, daily temperature control and high-temperature heat dissipation is achieved through an intelligent control unit (306). Accurate thermal management in a wide temperature range from-20 DEG C to 75 DEG C is realized with the total thickness not greater than 5mm, the temperature difference of the battery pack is controlled within + / -3 DEG C, and the safety, cycle life and space utilization rate of the battery under extreme working conditions are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of battery thermal management technology for new energy vehicles and energy storage equipment, specifically relating to a dual-temperature zone phase change flexible thermal management film and its three-dimensional microfluidic system for all-weather applications. This technology is particularly suitable for thermal management of power battery packs such as lithium iron phosphate and ternary lithium batteries under high-rate charge and discharge conditions, effectively solving key technical challenges such as high-temperature heat dissipation, low-temperature preheating, and temperature uniformity control. Background Technology

[0002] As a core component of new energy vehicles and energy storage systems, the performance, safety, and lifespan of power batteries are highly dependent on the operating temperature environment. The ideal operating temperature range is typically 15℃ to 35℃, and the temperature difference within the battery pack needs to be less than 5℃. However, in practical applications, high-rate charging and discharging (such as 3C fast charging and 2C discharging) can cause the battery to generate a large amount of heat, with a single cell generating 30-40W of heat, resulting in a sharp increase in the temperature inside the battery pack.

[0003] Especially in narrow spaces such as battery gaps (typically only 2-3mm), heat can easily accumulate, forming localized hotspots. These hotspots can be 8-12°C higher than the battery surface temperature and can quickly exceed the 75°C critical value, triggering a chain reaction of electrolyte decomposition and oxygen evolution in the cathode material, ultimately leading to thermal runaway. On the other hand, in low-temperature environments (such as below -10°C), the rate of internal chemical reactions in the battery drops sharply, internal resistance increases significantly, resulting in capacity decay of up to 40%-50%, charging efficiency dropping to below 35% of that at room temperature, and exacerbating the risk of lithium dendrite growth, severely shortening battery cycle life.

[0004] Existing battery thermal management technologies mainly include air cooling, liquid cooling, phase change material cooling, and their combined solutions, but all have significant drawbacks: air cooling technology has a simple structure and low cost, but its heat dissipation power is low (usually only 25-35W / m²), which cannot meet the heat dissipation requirements of high-power heat generation scenarios; single liquid cooling technology mostly uses metal cold plates, which have higher heat dissipation power, but the cold plates themselves are thick (usually ≥4mm), resulting in poor space compatibility with compact battery packs; single phase change material technology utilizes the latent heat of phase change to absorb heat, resulting in good temperature uniformity, but the latent heat is limited (≤140J / g), and it reaches phase change saturation within about 20 minutes under high-rate conditions, losing its temperature control capability. Summary of the Invention

[0005] Technical problems to be solved

[0006] Based on the background art, the present invention aims to solve the following core defects in existing power battery thermal management technology:

[0007] Uneven heat dissipation and localized overheating: Traditional liquid cooling solutions can only cool the battery surface and have poor heat dissipation effect on the gaps between batteries that generate a lot of heat, forming "heat dissipation blind spots" and causing the temperature difference of the battery pack to exceed 10°C.

[0008] Insufficient adaptability to all climates: Existing solutions are difficult to handle extreme high and low temperature conditions. Preheating efficiency is low and power consumption is high (≥100W) at low temperatures; under high temperature conditions, single-phase change materials saturate rapidly, and the heat dissipation power cannot meet the continuous temperature control requirements.

[0009] Poor structural compatibility and reliability: Rigid cold plates and composite systems have large thicknesses (≥8mm) and large bending radii, making them unsuitable for compact and irregularly shaped battery pack spaces;

[0010] Bottlenecks in the application of phase change materials: The single phase change temperature cannot match the requirements of the entire operating temperature range of the battery, and the material is prone to leakage during cyclic use.

[0011] Technical solution

[0012] To address the aforementioned technical problems, this invention provides a dual-temperature-zone phase-change flexible thermal management film and its three-dimensional microfluidic system for all-weather applications. The system employs a core architecture of "integrated flexible film + three-dimensional active liquid cooling + intelligent collaborative control."

[0013] Integrated flexible film core structure

[0014] The thermal management film is a multi-layer flexible composite structure integrated through a vacuum hot-pressing process, with a total thickness of no more than 5mm, and includes the following components from the battery surface outwards:

[0015] Insulating adhesive layer (106): 0.2 mm thick, made of high-temperature resistant silicone material, with high volume resistivity (≥10¹). 4 (Ω·cm) and high peel strength (≥5N / cm)

[0016] Temperature sensing layer (107): 0.1 mm thick, with fiber optic temperature sensors (≥6 measuring points) integrated into the polyimide substrate to monitor the battery surface, phase change layer interface, and coolant temperature in real time.

[0017] High-temperature phase change material layer (108a): 1.5 mm thick, composed of microencapsulated paraffin / expanded graphite composite material, phase change temperature 75℃±2℃, latent heat ≥190 J / g

[0018] Serpentine microchannel layer (109): A three-dimensional flow channel processed in a polyimide substrate, with a rectangular cross-section (0.3 mm deep × 0.8 mm wide), and the inner wall of the flow channel is coated with a polytetrafluoroethylene coating with a low coefficient of friction (≤0.05).

[0019] Low-temperature phase change material layer (108b): 1.5 mm thick, composed of microencapsulated stearic acid-lauric acid / nano-alumina composite material, phase change temperature 48℃±2℃, latent heat ≥160J / g

[0020] Three-dimensional active liquid cooling system

[0021] The system includes a gap-shaped serpentine water-cooling tube (102) embedded in the battery gap. This water-cooling tube is fluidly connected to a serpentine microchannel (109) within the membrane through laser perforation (110), together forming a three-dimensional liquid cooling network covering the battery surface and gap. The system is externally connected to an intelligent water tank (301) and a forced air cooling device (201) to provide power for coolant circulation, a low-temperature heat source, and high-temperature heat dissipation.

[0022] Intelligent Collaborative Control System

[0023] The system is controlled by an intelligent control unit (306) based on an STM32 series microcontroller core, which is configured to execute the following all-weather temperature control strategy:

[0024] Low-temperature preheating mode (T<40℃): The heating module of the intelligent water tank (301) is activated to preheat the coolant. The pump speed is 800rpm, achieving rapid temperature rise from -20℃ to 10℃, with power consumption ≤30W.

[0025] Normal temperature control mode (40℃≤T<65℃): The water pump starts (1200rpm), and the heat buffer is mainly provided by the low-temperature phase change material layer (108b). The fan starts and stops as needed.

[0026] High-temperature heat dissipation mode (T≥65℃): Activates the high-temperature phase change material layer (108a) and starts the water pump (3000rpm) and fan (2500rpm) for powerful heat dissipation.

[0027] Beneficial effects

[0028] Compared with the prior art, the present invention has the following significant advantages:

[0029] Extremely uniform thermal management: Through a three-dimensional liquid cooling network of "surface microchannels + gap water cooling pipes", the maximum temperature difference of the battery pack is reduced from more than 10°C to less than 3°C.

[0030] High-efficiency application in all climates: The system covers a wide temperature range from -20℃ to 75℃, reducing power consumption for low-temperature preheating by more than 70% and increasing heat dissipation power for high-temperature applications by 130%.

[0031] Ultra-thin, flexible, and highly compatible: The integrated film has a total thickness of only about 5mm and a small bending radius, allowing it to adhere tightly to the surface of various batteries.

[0032] High safety and long lifespan: Phase change materials are fully microencapsulated, fundamentally eliminating leakage (leakage rate ≤0.3%).

[0033] Exceptional reliability: After 1000 thermal cycles, the latent heat of the phase change material decreases by ≤5%, and the overall lifespan is expected to be ≥8 years. Attached Figure Description

[0034] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] Figure 1 Schematic diagram of the overall system structure and coolant circulation principle

[0036] This schematic diagram fully illustrates the workflow of the coolant circulation system: the coolant starts from the intelligent water tank (301), is pressurized and transported by the water pump (305), flows through the serpentine microchannel (109) embedded in the composite flexible membrane (105) and the gap serpentine water-cooling pipe (102) in the battery gap, completes heat exchange, enters the forced air cooling device (201) for heat dissipation and cooling, and finally returns to the intelligent water tank (301) to form a complete closed loop. This diagram clearly reflects the core principle of the system's "liquid cooling-air cooling" coordinated operation.

[0037] Figure 2 Explosion diagram of composite flexible film and battery gap water-cooling structure

[0038] The multi-layer structure of the composite flexible film (105) is shown in an exploded view, including an insulating adhesive layer (106), a temperature measuring layer (107), a high-temperature phase change material layer (108a), a serpentine microchannel (109), and a low-temperature phase change material layer (108b). The spatial relationship and assembly structure with the adjacent battery (101) and the gap serpentine water cooling pipe (102) are also clearly shown.

[0039] Figure 3 Schematic diagram of the serpentine microchannel layer layout in the composite flexible film

[0040] Specifically, the planar layout design of the serpentine microchannel (109) at the film layer is shown, including the channel orientation, structural morphology, and the precise distribution of laser perforations (110) used to connect the gap water cooling tubes.

[0041] Figure 4 Cross-sectional view of the connection structure between the battery gap water cooling tube and the microchannel inside the membrane.

[0042] The cross-sectional view reveals in detail the sealing structure and connection mechanism of the gap serpentine water cooling tube (102) through laser perforation (110) and the serpentine microchannel (109) inside the composite flexible film (105) to achieve fluid communication.

[0043] To facilitate understanding of the accompanying drawings, the markings of the components shown are explained as follows: The battery system components include: 101 battery cell, 102 gap serpentine water-cooling pipe, 103 coolant inlet and 104 coolant outlet; the composite flexible film layer structure includes: 105 composite flexible film, 106 insulating adhesive layer, 107 temperature sensing layer, 108a high-temperature phase change material layer, 108b low-temperature phase change material layer, 109 serpentine microchannel and 110 laser perforation; the external device system includes: 201 forced air cooling device; the intelligent control and monitoring system integrates: 301 intelligent water tank, 302 temperature sensor, 303 conductivity sensor, 304 liquid level sensor, 305 water pump and 306 intelligent control unit.

[0044] The above marking system fully covers the four functional modules involved in this invention: ① The battery thermal management execution unit (101-104) is responsible for direct contact with the battery for heat exchange; ② The composite film core structure (105-110) adopts a multi-layer flexible design to realize temperature sensing, phase change heat storage, and liquid flow path functions; ③ The external heat dissipation device (201) provides forced air cooling auxiliary heat dissipation; ④ The intelligent control system (301-306) integrates sensing, execution, and decision-making functions, and achieves precise temperature control in all climates through multi-parameter monitoring and multi-mode control. All component numbers correspond completely to the attached drawings, which facilitates understanding the structural features, spatial layout, and functional relationships of each component in conjunction with the illustrations. Detailed Implementation

[0045] Example 1: Preparation of composite flexible film (105)

[0046] Insulating adhesive layer (106) coating: A 0.2 mm thick flexible polyimide film was selected as the substrate, and a high-temperature resistant silicone was uniformly coated on its surface to a thickness of 0.2 mm. The film was then cured in an oven at 120°C for 1 hour. Temperature sensing layer (107) arrangement: A 0.05 mm thick silver paste wire pattern was laid out using a screen printing process to integrate 6 FISOFOT-L type fiber optic temperature sensors. High-temperature phase change material layer (108a) coating: Paraffin wax and expanded graphite with a phase change temperature of approximately 75°C were weighed at a mass ratio of 7:3. 15% PMMA prepolymer was added as the microcapsule shell material, and the microcapsule phase change material was prepared by in-situ polymerization.

[0047] Example 2: Assembly and Testing of a Three-Dimensional Liquid Cooling Network

[0048] The prepared composite flexible film (105) is cut according to the size of the battery module. A laser perforation machine is used to process laser perforations (110) with a diameter of 1.0 mm at predetermined positions on the edge of the film. After coating the tapered interface of the pre-formed gap serpentine water cooling tube (102) with sealing silicone, it is pressed into the laser perforation by a pneumatic tool to form a mechanical and fluid seal.

[0049] Performance test results show that during a 3C rate discharge test at an ambient temperature of 25℃, the battery pack's highest temperature stabilized at 48.5℃, with a maximum temperature difference of 2.3℃, and the system's heat dissipation power reached 82W. When the preheating mode was activated at a low temperature of -20℃, the battery pack rose from -20℃ to 10.2℃ within 18 minutes, with an average power consumption of 28W during the preheating process.

[0050] Industrial applicability

[0051] The dual-temperature zone phase change flexible thermal management film system provided by this invention has significant industrial practical value and can be widely used in fields such as power battery packs for new energy vehicles and battery systems for energy storage power stations. This system effectively solves the thermal management challenges during high-rate charging and discharging, improves the safety performance and lifespan of battery packs, and also features a compact structure, convenient installation, and high reliability, making it suitable for large-scale industrial production and application.

Claims

1. A dual-temperature zone phase change flexible thermal management patch system, characterized in that, The system comprises: An integrated composite flexible film (105) which is sequentially stacked from the surface of the battery (101) outwardly with an insulating adhesive layer (106), a temperature measuring layer (107), a high-temperature phase change material layer (108a), a serpentine micro-channel (109) and a low-temperature phase change material layer (108b); the system further comprises a gap serpentine water cooling pipe (102) arranged in the gap of the battery, the gap serpentine water cooling pipe (102) is in fluid communication with the serpentine micro-channel (109) through a laser perforation (110); and an external intelligent water tank (301) and a forced air cooling device (201) connected with the serpentine micro-channel (109) through a pipeline; and further comprising an intelligent control unit (306) signal connected with the temperature measuring layer (107) and the intelligent water tank (301) respectively.

2. The system of claim 1, wherein, The phase change temperature of the high-temperature phase change material layer (108a) is 70-78℃, and the phase change temperature of the low-temperature phase change material layer (108b) is 45-50℃, and the high-temperature phase change material layer (108a) and the low-temperature phase change material layer (108b) are both composite phase change materials with microcapsule packaging structure.

3. The system of claim 2, wherein, The high-temperature phase change material layer (108a) is a composite material of microcapsule packaged paraffin and expanded graphite, with latent heat of phase change not less than 190J / g and thermal conductivity not less than 2.5W / (m·K); the low-temperature phase change material layer (108b) is a microcapsule packaged stearic acid-lauric acid compound with added nano-aluminum oxide.

4. The system of claim 1, wherein, The cross section of the serpentine micro-channel (109) is rectangular, with a depth of 0.2-0.5mm and a width of 0.5-1.0mm, and the inner wall of the flow channel is coated with a polytetrafluoroethylene coating.

5. The system of claim 1, wherein, The intelligent control unit (306) is configured to execute the following temperature control strategy: when the battery temperature T<40℃, start the low-temperature preheating mode; when the battery temperature 40℃≤T<65℃, start the daily temperature control mode; when the battery temperature T≥65℃, start the high-temperature heat dissipation mode.

6. The system of claim 1, wherein, The total thickness of the composite flexible film (105) of the system is not more than 5mm, wherein the total thickness of the high-temperature phase change material layer (108a) and the low-temperature phase change material layer (108b) is 2-4mm, and the thickness of the substrate layer integrated with the serpentine micro-channel (109) is 1-2mm, and each layer is compounded into an integrated flexible film structure by a hot pressing process.

7. The system of claim 1, wherein, The intelligent water tank (301) is integrated with a micro water pump, a liquid level sensor, an electrical conductivity sensor and a heating module, and the electrical conductivity sensor is used to monitor the insulation performance of the cooling liquid in real time.

8. A method for thermal management of a power battery, applied to the system of any one of claims 1-7, characterized in that, The method comprises: monitoring the battery temperature in real time through the temperature measuring layer (107), the intelligent control unit (306) dynamically selects and activates the low-temperature preheating, daily temperature control or high-temperature heat dissipation mode according to the temperature data, passively buffers heat through the latent heat of phase change of the high-temperature phase change material layer (108a) and the low-temperature phase change material layer (108b), and cooperates with the active circulation heat dissipation through the serpentine micro-channel (109) and the gap serpentine water cooling pipe (102) to realize the full-weather thermal management of the battery in the temperature range of-20℃ to 75℃.

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