Graphite film-based multi-point distributed lithium battery heat dissipation method

Abstract

The application provides a multi-point distribution lithium battery heat dissipation method based on a graphite film. According to the temperature distribution of a mounting surface, the method changes the heat transfer thermal resistance in different temperature regions through multi-point contact, compensates for the difference in heat transfer in different temperature regions caused by temperature non-uniformity, achieves the effect that the temperature distribution of the mounting surface is not changed and the heat transfer power density of the lithium battery in different regions is the same, and realizes the temperature uniformity of the lithium battery mounting bottom plate. Meanwhile, due to the reduction of the contact area and the heat conduction, the active compensation power consumption can be significantly reduced under low temperature working conditions.

Description

Technical Field

[0001] This invention relates to the field of spacecraft technology, and in particular to a heat dissipation method for lithium batteries based on a multi-point distributed graphite film. Background Technology

[0002] Lithium-ion batteries possess advantages such as small size, light weight, high energy density, high charging efficiency, and low self-discharge rate, making them the third generation of space energy storage devices after nickel-cadmium and nickel-metal hydride batteries. When the temperature of a lithium battery is below 0°C, the internal resistance increases, the charging voltage rises, and the discharging voltage decreases, leading to a reduction in battery capacity. When the temperature of a lithium battery is above 45°C, the chemical equilibrium is disrupted, resulting in byproducts. Significant temperature differences between individual cells within a lithium battery pack lead to variations in discharge rates between cells, shortening battery life. Current requirements for the operating temperature of lithium batteries in spacecraft are between 10°C and 30°C, with temperature differences between individual cells within 3°C.

[0003] To ensure stable lithium battery temperature throughout its entire lifespan, lower-power lithium batteries are typically installed with thermal insulation, using radiative heat dissipation through the battery base plate and mounting surface. For higher-power lithium batteries, radiative heat dissipation is less than their own heat dissipation, requiring thermal connection to a honeycomb panel for heat dissipation. Heat pipes are often pre-embedded in the battery mounting surface for temperature equalization, thus meeting the temperature difference requirements between individual cells in the lithium battery pack. Since the width of a lithium battery is often smaller than the bending radius of the pre-embedded heat pipes, two or more heat pipes are usually pre-embedded in the mounting surface, which increases the mass and cost of the spacecraft. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of uneven temperature on the mounting surface during the thermal conductive installation of lithium batteries in spacecraft, and proposes a multi-point distributed lithium battery heat dissipation method based on graphite film.

[0005] This invention is achieved through the following technical solution: This invention proposes a multi-point distributed lithium battery heat dissipation method based on graphite film. Specifically, the method involves: calculating the weighted average heat dissipation Q0 of the lithium battery under typical operating conditions; simulating the high-temperature operating conditions of the entire satellite to obtain the temperature distribution of the lithium battery mounting surface at the moment of maximum external heat flow; and delineating region S based on the temperature distribution. i and corresponding temperature T i The average temperature T0 of the mounting surface is obtained by weighted averaging; the installation method of the lithium battery is determined by the target temperatures T′0, Q0, and T0 of the lithium battery; if the lithium battery adopts thermally conductive installation, the required contact area A' with the heat dissipation surface is calculated by the heat transfer formula, and then the required number of point-distributed b×b plates N is obtained; further, T′0, T... i S iThe ratio of point distribution in different regions was obtained, and the specific number of point-pattern distributions in each region was obtained by combining the total number N. Finally, the designed point distribution was brought into the spacecraft for on-orbit high and low temperature operation simulation, and minor adjustments were made according to the specific situation.

[0006] Furthermore, the formula for calculating the average heat loss Q0 is as follows: t i This refers to the time corresponding to the work mode.

[0007] Furthermore, the formula for calculating the average temperature T0 is as follows:

[0008] Furthermore, when When the temperature reaches 0, it indicates that the radiation heat dissipation capacity is insufficient and heat conduction heat dissipation with the mounting surface is required; where A is the area of ​​the lithium battery base plate, ε is the infrared emissivity of the lithium battery mounting surface, σ is the Boltzmann constant, and T′0 is the target temperature for lithium battery temperature control.

[0009] Furthermore, the heat transfer formula is hA'(T′0-T0)=Q0, and the effective contact area A' is obtained from the heat transfer formula, where h is the heat transfer coefficient.

[0010] Further, calculate the required number N of b×b sheet-like graphite films: Round N up, where A" = b × b.

[0011] Furthermore, assuming the lithium battery mounting surface is divided into m regions based on temperature, the distribution of the number of sheet-like graphite films within each region is as follows:

[0012] After rounding, the following condition is satisfied: N1 + ... + N m ≥N;

[0013] Within their respective designated areas, the dot-shaped graphite films are evenly distributed.

[0014] Furthermore, during implementation, the heating tape is first attached to the lithium battery groove. After the heating tape is cured, the entire base plate is covered with a heat-conducting film according to its shape, and then the implementation is carried out according to the designed point distribution.

[0015] This invention proposes an electronic device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the aforementioned multi-point distributed lithium battery heat dissipation method based on graphite film.

[0016] This invention proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of the aforementioned multi-point distributed lithium battery heat dissipation method based on graphite film.

[0017] The beneficial effects of this invention are:

[0018] To address the issue of uneven temperature between individual cells caused by uneven temperature on the mounting surface of thermally conductive lithium batteries, this invention proposes a multi-point distributed lithium battery heat dissipation method based on a graphite film. By adjusting the thermal resistance of different temperature regions through multi-point contact according to the temperature distribution of the mounting surface, this method compensates for the differences in heat transfer caused by temperature inhomogeneity. This achieves the effect of maintaining the same heat transfer power density across different temperature regions of the lithium battery without altering the temperature distribution of the mounting surface, thus ensuring uniform temperature of the lithium battery substrate. Furthermore, because this method reduces the contact area and thermal conductivity, it can significantly reduce active compensation power consumption under low-temperature conditions. Attached Figure Description

[0019] 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.

[0020] Figure 1 This is a schematic diagram of the lithium battery structure according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the lithium battery base plate structure according to an embodiment of the present invention;

[0022] Figure 3 This is a flowchart of a multi-point distributed lithium battery heat dissipation method based on graphite film, as described in this invention.

[0023] Figure 4 This is a schematic diagram of the single-rail heat dissipation distribution of a lithium battery under typical operating conditions in an embodiment of the present invention.

[0024] Figure 5 This is a schematic diagram of the temperature distribution at the moment of maximum external heat flow on the lithium battery mounting surface and the multi-point distribution on the mounting surface under high-temperature conditions in an embodiment of the present invention.

[0025] Figure 6 This is a schematic diagram comparing the temperature non-uniformity of lithium batteries under high-temperature conditions in an embodiment of the present invention.

[0026] Figure 7 This is a schematic diagram comparing the temperature non-uniformity of lithium batteries under low-temperature conditions in an embodiment of the present invention. Detailed Implementation

[0027] 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.

[0028] Combination Figures 1-7 This invention proposes a multi-point distributed lithium battery heat dissipation method based on graphite film. Specifically, the method involves: calculating the weighted average heat dissipation Q0 of the lithium battery under typical operating conditions; simulating high-temperature conditions across the entire satellite to obtain the temperature distribution of the lithium battery mounting surface at the moment of maximum external heat flow; and defining a region S based on the temperature distribution. i and corresponding temperature T i The average temperature T0 of the mounting surface is obtained by weighted averaging; the installation method of the lithium battery is determined by the target temperatures T′0, Q0, and T0 of the lithium battery; if the lithium battery adopts thermally conductive installation, the required contact area A' with the heat dissipation surface is calculated by the heat transfer formula, and then the required number of point-distributed b×b plates N is obtained; further, T′0, T... i S i The ratio of point distribution in different regions was obtained, and the specific number of point-pattern distributions in each region was obtained by combining the total number N. Finally, the designed point distribution was brought into the spacecraft for on-orbit high and low temperature operation simulation, and minor adjustments were made according to the specific situation.

[0029] The formula for calculating the average heat loss Q0 is as follows: t i This refers to the time corresponding to the work mode.

[0030] The formula for calculating the average temperature T0 is as follows:

[0031] when When the temperature reaches 0, it indicates that the radiation heat dissipation capacity is insufficient and heat conduction heat dissipation with the mounting surface is required; where A is the area of ​​the lithium battery base plate, ε is the infrared emissivity of the lithium battery mounting surface, σ is the Boltzmann constant, and T′0 is the target temperature for lithium battery temperature control.

[0032] The heat transfer formula is hA′(T′0-T0)=Q0. The effective contact area A' is obtained from the heat transfer formula, where h is the heat transfer coefficient.

[0033] like Figure 2 As shown, the width of the groove portion of the lithium battery mounting surface is 'a', and the width of the contact edge between the groove and the mounting surface is 'b'. A point-distribution method uses graphite film material, and the graphite film is cut into b×b sheet-like shapes. Calculate the required number N of b×b sheet-like graphite film: Round N up, where A" = b × b.

[0034] The heat dissipation of a single lithium battery is the same, that is, the heat dissipation distribution of the lithium battery mounting surface is uniform. If the heat transfer power density of each temperature area is the same, the temperature uniformity of the lithium battery can be guaranteed. In order to ensure that the heat transfer power density of each temperature area is the same, the heat dissipation of each temperature area must be proportional to the area.

[0035] If the goal is to achieve the same heat flux density across the region, then... Then R i ∝(T′0-T i ), where R i To define the total contact thermal resistance of the region, T′0 is the target temperature;

[0036] The thermal resistance of each sheet of graphite film is There are N in the i-th region. i A sheet-like graphite film, with a total thermal resistance of Right now Therefore

[0037] Since the power density of lithium batteries is the same, the heat dissipation φ in the region is... i Should be with S i Positively correlated, i.e., φ i ∝S i , Therefore N i ∝S i .

[0038] Assume the lithium battery mounting surface is divided into m regions based on temperature, and the distribution of the number of sheet graphite films within each region is as follows:

[0039] After rounding, the following condition is satisfied: N1 + ... + N m ≥N;

[0040] Within their respective designated areas, the dot-shaped graphite films are evenly distributed.

[0041] Based on the above technical requirements, simulations were performed for low-temperature operating conditions, and the design power of the heating element needed to be obtained under these conditions. Additionally, if the lithium battery is installed with thermal insulation, a thermal insulation pad should be installed.

[0042] In practice, the heating tape is first attached to the groove of the lithium battery. While leaving a cable outlet, the heating tape should cover the groove as much as possible. The heating tape is attached to the groove of the base plate. After the heating tape is cured, the cable is routed. Then, a thermally conductive graphite film is covered on the entire base plate in a conformal manner. The graphite film has high thermal conductivity along the plane direction, thereby reducing the temperature gradient of the lithium battery fixing base plate. Then, according to the design, the b×b sheet graphite film is attached to the surface of the conformal graphite film according to the design scheme.

[0043] Example

[0044] The following further elaborates in detail on a method for cooling lithium batteries with multi-point distribution based on graphite film proposed by the present invention in conjunction with the attached drawings and specific embodiments.

[0045] The structure of a certain model spacecraft lithium battery is as Figure 1 shown, consisting of a fixed bottom plate, a lithium battery, a cover plate, a bus bar, a PCB board, and an insulating sleeve;

[0046] Figure 2 Figure shows the structure schematic diagram of the fixed bottom plate of the lithium battery. The front side has circular fixing holes for the lithium battery, and the back side has a rectangular groove. On the one hand, it is for weight reduction, and on the other hand, a heating tape is pasted for low-temperature compensation;

[0047] In the composition structure of the lithium battery, the cover plate and the insulating sleeve are made of PETP material with a thermal conductivity coefficient of 0.27 W / m·k, and the thermal conductivity performance is extremely poor. Moreover, the cover plate and the PCB have point contact, and the heat transfer path resistance from the lithium battery to the insulating sleeve is large, which is not conducive to heat dissipation at the upper part of the lithium battery;

[0048] Figure 4 Figure shows the change of the heat consumption of the lithium battery over time during the single-rail process under the typical working mode of a certain spacecraft in the embodiment. The average heat consumption can be obtained

[0049] Figure 5 Figure shows the temperature distribution of the installation surface of a certain spacecraft under high-temperature working conditions in the embodiment. The installation surface is divided into 3 regions, and the average value within the region is taken. Therefore, T1 is 4.3 °C, T2 is 12.4 °C, and T3 is 18.5 °C. By dividing the regions, it can be obtained

[0050] If radiation heat dissipation is adopted, under high-temperature working conditions, the radiation heat dissipation amount of the lithium battery installation surface In the formula, T′0 is 20 °C, ε is the infrared emissivity of the installation surface 0.85, σ is the Boltzmann constant, and A is the total radiation area of the contact edge and the groove of the installation surface 0.077 m 2 ;

[0051] Determine the installation form of the lithium battery: Compare the relationship between the radiation heat dissipation amount Q1 and the heat consumption Q2 of the lithium battery. Q1 < Q2, so the lithium battery should be installed with heat conduction;

[0052] Determine the contact area of the lithium battery: hA′(T′0 - T0) = Q0, and A' is obtained as 0.0022 m 2 ; The graphite film belongs to the interface material. In the formula, h is the heat transfer coefficient, taking 500 W / m 2 ·k;

[0053] Determine the number N of point contact graphite films: In the embodiment, the width b of the contact edge of the lithium battery mounting surface is 12mm, and the size of the point contact graphite film is 12mm×12mm. Therefore, the number of point contacts is N, which is at least 16 pieces.

[0054] Calculate the distribution of the graphite film: Therefore, N1:N2:N3 = 1:2:16, so N1 is 1 piece, N2 is 2 pieces, and N3 is 16 pieces;

[0055] Based on the specific conditions of the lithium battery mounting holes and mounting surface, the mounting surface is designed with a point-like distribution as follows: Figure 5 As shown;

[0056] On-orbit high-temperature operating condition simulation comparison: using a multi-point distributed lithium battery, the non-uniformity is 1.78℃, and the heating band power is 0.92W; using a uniform contact method on the mounting surface, the non-uniformity of the lithium battery is 4℃, and the heating band power is 3.36W.

[0057] On-orbit low-temperature operating condition simulation comparison: using a multi-point distributed lithium battery, the non-uniformity is 1.75℃, and the heating band power is 12.38W; using a uniform contact method on the mounting surface, the non-uniformity of the lithium battery is 5.3℃, and the heating band power is 21.38W.

[0058] Simulation results show that multi-point distributed systems can effectively reduce temperature unevenness and active power consumption in lithium batteries.

[0059] This invention provides a multi-point distributed heat dissipation method for lithium batteries based on graphite film. The method includes: calculating the weighted average heat dissipation Q0 of the lithium battery under typical operating conditions; simulating high-temperature conditions across the entire satellite to obtain the temperature distribution of the lithium battery mounting surface at the moment of maximum external heat flow; and defining a region S based on the temperature distribution. i and corresponding temperature T i The average temperature T0 of the mounting surface is obtained by weighted averaging. The lithium battery mounting method is determined by the target temperatures T′0, Q0, and T0 of the lithium battery. If the lithium battery adopts thermally conductive mounting, the required contact area A' with the heat dissipation surface is calculated using the heat transfer formula, thereby determining the required number N of point-distributed b×b plates. The installation method is determined by T′0, T... i S iThe ratio of the number of point-type distributions in different regions was obtained, and the specific number of point-type patches in each region was calculated based on the total number N. The designed point-type distribution was then applied to the spacecraft for on-orbit high and low temperature condition simulation, with minor adjustments made according to specific circumstances. In implementation, the heating tape was first adhered to the lithium battery recess. After the heating tape cured, the entire base plate was covered with a thermally conductive film, and then the design point-type distribution was implemented. The method described in this invention changes the contact thermal resistance of different temperature regions through point distribution, so that different temperature regions have the same heat dissipation power density, thereby achieving a uniform temperature effect. Compared with the method of pre-embedding heat pipes on the mounting surface base plate to achieve uniform temperature, this method reduces development and launch costs, lightens the overall weight, reduces active power consumption under low temperature conditions, and releases the coupling between various subsystems.

[0060] This invention proposes an electronic device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the aforementioned multi-point distributed lithium battery heat dissipation method based on graphite film.

[0061] This invention proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of the aforementioned multi-point distributed lithium battery heat dissipation method based on graphite film.

[0062] The memory in this application embodiment can be volatile memory or non-volatile memory, or it can include both volatile and non-volatile memory. The non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. The volatile memory can be random access memory (RAM), which is used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous linked dynamic random access memory (SLDRAM), and direct rambus RAM (DRRAM). It should be noted that the memory used in the methods described in this invention is intended to include, but is not limited to, these and any other suitable types of memory.

[0063] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available media may be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., high-density digital video discs (DVDs)), or semiconductor media (e.g., solid-state disks (SSDs)).

[0064] In implementation, each step of the above method can be completed by integrated logic circuits in the processor's hardware or by instructions in software. The steps of the method disclosed in the embodiments of this application can be directly implemented by a hardware processor, or by a combination of hardware and software modules in the processor. The software modules can reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. This storage medium is located in memory, and the processor reads information from the memory and, in conjunction with its hardware, completes the steps of the above method. To avoid repetition, detailed descriptions are omitted here.

[0065] It should be noted that the processor in the embodiments of this application can be an integrated circuit chip with signal processing capabilities. During implementation, each step of the above method embodiments can be completed by the integrated logic circuitry in the processor's hardware or by instructions in software form. The processor can be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this application can be directly embodied as being executed by a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. The software modules can be located in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. This storage medium is located in memory, and the processor reads the information in the memory and, in conjunction with its hardware, completes the steps of the above methods.

[0066] The above provides a detailed description of a multi-point distributed lithium battery heat dissipation method based on graphite film proposed in this invention. Specific examples have been used to illustrate the principle and implementation of this invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for heat dissipation of a lithium battery based on a multi-point distribution of graphite film, characterized in that, The method specifically involves calculating the weighted average heat dissipation of a lithium battery under typical operating conditions. Q 0; Simulate the high-temperature conditions of the entire satellite, obtain the temperature distribution of the lithium battery mounting surface at the moment of maximum external heat flow, and delineate the region based on the temperature distribution. S i and corresponding temperature T i The average temperature of the mounting surface is obtained by weighted averaging. T 0; Target temperature controlled by lithium battery , Q 0、 T 0. Determine the lithium battery installation method; when When the radiation heat dissipation capacity is insufficient, heat conduction heat dissipation with the mounting surface is required; where A This refers to the area of ​​the lithium battery base plate. ε For the infrared emissivity of the lithium battery mounting surface, Boltzmann's constant, The target temperature for lithium battery temperature control; when the lithium battery conducts heat to the mounting surface, the required contact area with the mounting surface is calculated using the heat transfer formula. A ’ This leads to the desired point distribution. b×b Number of sheet-like graphite films N Further through , T i , S i Point distribution in different regions was obtained b×b The ratio of sheet-like graphite films, combined with the total number N The point distribution of each region was obtained. b×b The number of sheet-like graphite films was determined; finally, the designed point distribution of graphite films was introduced into the spacecraft for on-orbit high and low temperature operating condition simulation, and minor adjustments were made based on the specific circumstances. The average heat loss Q The formula for calculating 0 is: , t i The time is for the corresponding work mode; Assume the lithium battery mounting surface is divided into m regions based on temperature, and the distribution of the number of sheet graphite films within each region is as follows: After rounding, the following conditions are met: Within their respective designated areas, the graphite films are evenly distributed.

2. The method according to claim 1, characterized in that, The average temperature T The formula for calculating 0 is: .

3. The method according to claim 2, characterized in that, The heat transfer formula is: The effective contact area is obtained based on the heat transfer formula. In the formula h The heat transfer coefficient is denoted as .

4. The method according to claim 3, characterized in that, Calculation required b×b Number of sheet-like graphite films N : , N Round up, where = b×b .

5. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1-4.

6. A computer-readable storage medium for storing computer instructions, characterized in that, When the computer instructions are executed by the processor, they implement the steps of the method according to any one of claims 1-4.

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