Method and system for testing heat conductivity coefficients of square laminated battery in all directions

Abstract

The invention provides a method and a system for testing each heat conduction coefficient of a square laminated battery, and belongs to the field of electric vehicle heat management. The method comprises the following steps: arranging a first heating film on an x-direction middle section of a roll core in the battery, insulating xy and xz surfaces, constructing a one-dimensional heat exchange condition of a yz surface, and calculating an x-direction heat conduction coefficient after measuring a steady-state temperature; a second heating film is arranged in the middle of a roll core in the battery in the y direction, xy and yz surfaces are subjected to heat insulation, and the one-dimensional heat exchange condition of the xz surface is constructed; measuring the steady-state temperature and then calculating a y-direction heat conduction coefficient; a third heating film is arranged in the center of the z-direction top of a roll core in the battery, xz and yz surfaces are subjected to heat insulation, and the xy surface one-dimensional heat exchange condition is constructed; and recording temperature data in the heating process, and determining a z-direction heat conduction coefficient through iterative optimization in combination with the x-direction heat conduction coefficient and the y-direction heat conduction coefficient. The method can accurately reflect the real heat conduction behavior in the battery, and solves the problem of test deviation caused by the heat conduction influence of a metal shell in a traditional external heating method.

Description

Technical Field

[0001] This invention belongs to the field of electric vehicle thermal management technology, and particularly relates to a method and system for testing the thermal conductivity of square stacked batteries in various directions. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Lithium-ion batteries have become the primary power source for new energy vehicles due to their high energy density, long cycle life, and lack of memory effect. Battery thermal management and safety are core technologies in battery system integration, and their performance directly affects the vehicle's power, range, and safety. For prismatic laminated batteries, the structures of the internal electrode sheets and separators are completely different in the stacking direction and in the plane of the electrode sheets, resulting in significant anisotropy in their thermal conductivity. Therefore, accurately measuring the thermal conductivity of the battery in the x, y, and z directions is crucial for achieving accurate thermal simulation.

[0004] Currently, one of the most classic and widely used methods for measuring the thermal conductivity of materials is the steady-state method. Its principle is based on Fourier's one-dimensional steady-state heat conduction law. When the test sample reaches thermal equilibrium, the thermal conductivity is calculated by measuring the heat flux density through the sample, the temperature difference between the two sides of the sample, and the thickness. However, this traditional testing method has a fundamental flaw, leading to test results that are seriously inconsistent with the actual thermal behavior of batteries during operation. Firstly, in actual operation, heat is generated in the battery's internal core (i.e., Joule heat and reaction heat generated by the electrochemical reaction), and then transferred from the inside out, passing through the core and insulating materials, and finally dissipating into the environment through the metal casing. The traditional method, however, directly heats the external metal casing. Most of the heat is rapidly conducted along the high thermal conductivity aluminum-plastic film or aluminum casing, with only a very small portion penetrating to the internal core, which has poor thermal conductivity. This results in the test process primarily reflecting the thermal conductivity characteristics of the outer casing, rather than the true thermal conductivity of the internal core.

[0005] Secondly, traditional methods treat the battery as a homogeneous body, providing only a single, general thermal conductivity value. This fails to distinguish and capture the significant differences in thermal conductivity between the stacked electrode direction and the in-plane direction of the electrode. Due to this unrealistic heat transfer path, the "overall" thermal conductivity measured by traditional methods is usually significantly inflated, failing to accurately reflect the actual ability of heat to be conducted from the battery's interior to the exterior. This results in a large discrepancy between simulation analysis results based on this data and actual conditions, severely impacting the design and optimization of the thermal management system. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a method and system for testing the thermal conductivity of square stacked batteries in different directions. By embedding heating films in different directions of the square stacked batteries, the heat transfer path during actual battery operation is simulated, thereby objectively testing the thermal conductivity of the batteries in different directions. This effectively solves the problem that the traditional steady-state method applies a heat source to the outside of the battery, resulting in test results that do not match the actual heat transfer path during battery operation and poor test accuracy.

[0007] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: The first aspect of this invention provides a method for testing the thermal conductivity of various components of a square stacked battery; A method for testing the thermal conductivity of square stacked solar cells in various directions includes: A first heating film is arranged on the middle section of the core inside the battery in the x direction to insulate the xy and xz planes, construct a one-dimensional heat transfer condition for the yz plane, and calculate the thermal conductivity of x after measuring the steady-state temperature. A second heating film is arranged at the middle position of the y-direction of the internal core of the battery to insulate the xy and yz surfaces, thereby constructing a one-dimensional heat transfer condition for the xz surface; the thermal conductivity of y is calculated after measuring the steady-state temperature. A third heating film is arranged at the top center of the Z-axis of the internal core of the battery to insulate the XZ and YZ planes and construct one-dimensional heat transfer conditions on the XY plane; the temperature data of the heating process is recorded, and the Z-axis thermal conductivity is determined by iterative optimization in combination with the X-axis thermal conductivity and the Y-axis thermal conductivity.

[0008] As a further technical solution, a first heating film is arranged on the mid-section of the internal core of the battery in the x-direction to insulate the xy and xz planes, constructing a one-dimensional heat transfer condition on the yz plane. After measuring the steady-state temperature, the x-direction thermal conductivity is calculated, including: The internal core of the battery is cut open along the x-direction to the middle position. A first heating film is arranged on the cut surface, and the two xy planes and two xz planes of the battery are insulated. Only the two yz planes are exposed to the environment to create a one-dimensional heat exchange condition. Thermocouples are arranged at the center of the first heating film and at the center of the two outer surfaces of the yz. The first heating film is heated by a constant power. When the temperature change rate of each thermocouple is less than a predetermined threshold, the steady-state temperature data is recorded, and the x-thermal conductivity is calculated according to the first formula.

[0009] As a further technical solution, a second heating film is arranged at the middle position of the y-axis of the internal core of the battery to insulate the xy and yz planes, thus constructing a one-dimensional heat transfer condition on the xz plane; after measuring the steady-state temperature, the y-axis thermal conductivity is calculated, including: A second heating film along the xz plane is arranged at the middle position of the y-direction of the inner core of the battery, and the two xy planes and two yz planes of the battery are heat-insulated, leaving only the two xz planes exposed to the environment to construct a one-dimensional heat exchange condition. Thermocouples are arranged at the center of the second heating film and at the center of the two xz outer surfaces, respectively. Constant power is applied to the second heating film for heating. When the temperature change rate of each thermocouple is less than the predetermined threshold, steady-state temperature data is recorded, and the y-thermal conductivity is calculated according to the second formula.

[0010] As a further technical solution, the first formula is:

[0011] in, The heat flux density of the first heating film in steady state. The reading difference is the temperature difference between the thermocouple at the center of the first heating film and the thermocouple on the yz surface in steady state. Let x be the width of the battery in the x-direction.

[0012] As a further technical solution, the second formula is:

[0013] in, The heat flux density of the first heating film in steady state. The reading difference between the thermocouple at the center of the first heating film and the thermocouple on the xz surface is the temperature difference under steady-state conditions. Let x be the width of the battery in the x-direction.

[0014] As a further technical solution, the step of determining the z-thermal conductivity through iterative optimization includes: Based on the wind speed in the test environment, calculate the convective heat transfer coefficient (h) of the two xy planes exposed in the environment. A CFD model is constructed that includes the battery geometry, the convective heat transfer coefficient (h), the density (ρ), the specific heat capacity (Cp), the heating power (P), the x-direction thermal conductivity, and the y-direction thermal conductivity. In the CFD model, several different candidate values ​​for the z-thermal conductivity were tried, and simulation calculations were performed to obtain the simulation temperature data corresponding to each candidate value. The simulated temperature data corresponding to each candidate value is compared with the measured temperature data, and the candidate value that minimizes the difference between the two is selected as the final z-thermal conductivity.

[0015] A second aspect of the present invention provides a system for testing the thermal conductivity of various components of a square stacked battery.

[0016] A system for testing the thermal conductivity of square stacked solar cells includes: Test stand for fixing the square stacked battery under test; The heating module includes: a first heating unit configured to be disposed at the middle cut section along the x-direction of the internal winding core of the battery; a second heating unit configured to be disposed at the middle position along the y-direction of the internal winding core of the battery and arranged along the xz plane; and a third heating unit configured to be disposed at the top center position along the z-direction of the internal winding core of the battery. The thermal insulation module, including removable thermal insulation material, is configured to selectively wrap the battery in the xy plane, xz plane, or yz plane to create one-dimensional heat transfer conditions. The temperature measurement module includes multiple thermocouples configured to measure the temperature at the center of the heating unit and a specific outer surface of the battery; The data acquisition and control module is electrically connected to the heating module and the temperature measuring module, and is configured to apply a constant power to the heating module and collect and record the temperature data of the temperature measuring module. The calculation and analysis module, which is communicatively connected to the data acquisition and control module, is configured to: calculate the x-axis thermal conductivity and y-axis thermal conductivity based on the steady-state temperature data obtained from tests in the x and y directions; construct a CFD model based on the x-axis and y-axis thermal conductivity, ambient wind speed, battery physical parameters, and z-axis heating power, and determine the z-axis thermal conductivity through an iterative optimization method.

[0017] A third aspect of the present invention provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the steps of a method for testing the thermal conductivity of various aspects of a square stacked battery as described in the first aspect of the present invention.

[0018] A fourth aspect of the present invention provides an electronic device, including a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of a method for testing the thermal conductivity of various aspects of a square stacked battery as described in the first aspect of the present invention.

[0019] The above one or more technical solutions have the following beneficial effects: This invention simulates the heat source during actual operation by embedding a heating film within key locations of the battery core (such as the mid-sections in the x and y directions, and the top center in the z direction). This ensures that the heat transfer path matches the actual operating conditions, meaning that heat must pass through the multi-layered structure composed of different materials within the core before reaching the outer casing and dissipating into the environment. This fundamentally avoids the shortcomings of traditional methods, where heating occurs on the external metal casing, causing heat to be primarily conducted along the highly thermally conductive outer casing and failing to accurately reflect the thermal conductivity of the internal core. Therefore, it obtains the thermal conductivity coefficients in each direction that truly reflect the internal thermal conductivity characteristics of the battery, significantly improving test accuracy.

[0020] This invention achieves independent and accurate measurement of thermal conductivity in three directions—width (x-axis), thickness (y-axis), and height (z-axis)—by designing unique heating, insulation, and temperature measurement schemes for each direction. Particularly for stacked batteries, the thermal conductivity differs significantly between the stacking direction (y-axis) and the in-plane directions (x and z-axis). This invention solves the technical challenge of traditional methods failing to distinguish anisotropy, providing crucial foundational data for refined thermal management and simulation analysis of batteries.

[0021] This invention directly measures the x and y directions using a steady-state method, with a clear principle and reliable operation. For the z direction, which is difficult to measure directly using a steady-state method due to structural complexity, it uses the already measured high-precision data in the x and y directions as input, constructs a CFD model for simulation and back-calculation, and determines the optimal z-direction thermal conductivity through iterative optimization. This approach ensures the accuracy of the basic data and cleverly solves the problem of direct measurement in complex directions, making the method scientific and highly innovative.

[0022] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0024] Figure 1 This is a flowchart of the method in the first embodiment.

[0025] Figure 2 This is a schematic diagram of the x-axis thermal conductivity test in the first embodiment.

[0026] Figure 3 This is a schematic diagram of the y-direction thermal conductivity test in the first embodiment.

[0027] Figure 4 This is a schematic diagram of the z-thermal conductivity test in the first embodiment.

[0028] Figure 5 This is a schematic diagram of the x-axis test data and data processing results for the first embodiment.

[0029] Figure 6 This is a schematic diagram of the y-axis test data and data processing results for the first embodiment.

[0030] Figure 7 This is a schematic diagram of the test data results in the z-direction of the first embodiment. Detailed Implementation

[0031] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0032] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0033] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0034] Example 1 This embodiment discloses a method for testing the thermal conductivity of various components of a square stacked battery. like Figure 1 As shown, a method for testing the thermal conductivity of square stacked solar cells includes: Step S1: Arrange the first heating film in the middle section of the x-direction of the internal core of the battery to insulate the xy and xz surfaces, construct the one-dimensional heat transfer conditions of the yz surface, and calculate the x-thermal conductivity after measuring the steady-state temperature. Step S2: Arrange a second heating film at the middle position of the y-direction of the internal core of the battery to insulate the xy and yz surfaces and construct a one-dimensional heat transfer condition for the xz surface; calculate the y-direction thermal conductivity after measuring the steady-state temperature. Step S3: Arrange a third heating film at the top center of the cell in the z-direction inside the battery to insulate the xz and yz surfaces and construct one-dimensional heat transfer conditions in the xy surface; record the temperature data during the heating process, and determine the z-direction thermal conductivity by iterative optimization in combination with the x-direction thermal conductivity and y-direction thermal conductivity.

[0035] Step S1: Arrange the first heating film in the middle section of the x-direction of the internal core of the battery to insulate the xy and xz planes, construct the one-dimensional heat transfer conditions of the yz plane, and calculate the x-thermal conductivity after measuring the steady-state temperature.

[0036] A square stacked battery to be tested was selected, its outer metal casing was removed, and the internal core was extracted. A precision cutting device was used to make a perpendicular cut along the geometric center of the core in the x-direction (width direction), ensuring a smooth, burr-free cut and that the cut surface was completely perpendicular to the x-direction to avoid uneven adhesion of the heating film due to a tilted cut. In this embodiment, the thermal conductivity of the solid skeleton structure of the internal core was measured. This is the source of heat generation and the main path of heat conduction during battery operation. After the cutting operation, although the battery's closed system was broken, the core solid structure of the core was preserved, and its inherent and decisive thermal conductivity physical properties remained unchanged. The test yielded the thermal conductivity performance of this solid skeleton under simulated real heat generation paths, data of paramount importance for thermal management simulation. After cutting, heat is emitted from the built-in heating film and conducted to the outer casing through the solid skeleton of the core. This core path is completely consistent with the main heat transfer path during actual battery operation, fundamentally ensuring the authenticity of the test.

[0037] A constant power heating film matching the cross-sectional dimensions of the core is selected, namely the first heating film. The first heating film is tightly attached to the cut core cross-section with a gap of ≤0.1mm. High-temperature resistant tape is used to fix the heating film to ensure no displacement during heating and full contact between the heating film and the core cross-section, avoiding uneven heat transfer caused by local gaps. like Figure 2 As shown, a first thermocouple is attached to the geometric center of the surface of the first heating film. The contact pressure between the thermocouple sensing end and the surface of the heating film is controlled at 0.5-1N to avoid temperature measurement delay due to excessive looseness or damage to the heating film due to excessive tightness. A second thermocouple and a third thermocouple are attached to the geometric center of the outer surface of the yz side of the core, respectively. Similarly, the sensing end is ensured to be in close contact with the yz surface, and the thermocouple wires are arranged along the heat insulation direction to avoid the wires conducting heat and affecting the temperature measurement accuracy. Select a material with a thermal conductivity ≤0.03. High-efficiency thermal insulation material is used. Based on the dimensions of the xy plane (xz plane) and xz plane (xy plane) of the core, thermal insulation sheets are cut to perfectly match the surface, ensuring a coverage area of ​​≥99%. The cut thermal insulation sheets are then attached to the two xy planes and two xz planes of the core, secured with high-temperature resistant straps or tape, ensuring no gaps between the insulation material and the core surface, and a heat loss rate of ≤1% for non-exposed surfaces. Only the two yz planes (the end faces at both ends in the x direction) of the core are fully exposed to the test environment, ensuring heat transfer only along the x direction, constructing strict one-dimensional heat transfer conditions, and eliminating interference from heat loss in other directions on the test results. Connect the heating film power supply to the thermocouple data acquisition device, and collect the temperature data of the first, second, and third thermocouples in real time after starting heating; when the temperature reading change rate of the three thermocouples is ≤0.5℃ / h, and this state is maintained for 30 minutes, the test system is judged to have reached thermal steady state. At this time, the heat transfer rate and heat dissipation rate along the x-direction are balanced, and the data can be used for subsequent calculations. Record the steady-state temperature data and calculate the thermal conductivity x using the first formula. The first formula is:

[0038] in, The heat flux density of the first heating film in steady state. The reading difference is the temperature difference between the thermocouple at the center of the first heating film and the thermocouple on the yz surface in steady state. Let x be the width of the battery in the x-direction.

[0039] Through the above steps, the true thermal conductivity of the square stacked battery core in the x-direction can be accurately measured, and the testing process closely follows the actual heat transfer path of the battery, with data accuracy significantly better than traditional external heating methods.

[0040] Step S2: Arrange a second heating film at the middle position of the y-direction of the inner core of the battery to insulate the xy and yz surfaces and construct a one-dimensional heat transfer condition for the xz surface; calculate the y-direction thermal conductivity after measuring the steady-state temperature.

[0041] like Figure 3 As shown, a square stacked battery to be tested is selected. After removing the outer metal casing, the inner core is taken out. The total thickness D of the core in the y-direction (thickness direction) is measured with calipers, and the geometric center plane in the y-direction is marked. A constant power heating film, i.e., the second heating film, is selected that perfectly matches the dimensions of the core's xz plane. Along the center-marked plane in the y-direction of the core, the second heating film is embedded inside the core and fixed with high-temperature resistant insulating adhesive to prevent displacement during heating that could lead to uneven heat transfer.

[0042] A fourth thermocouple (T-type or K-type, temperature measurement error ≤ ±0.1℃) is attached to the geometric center of the second heating film surface. The contact pressure of the sensing end is controlled at 0.5-1N to avoid temperature measurement delay due to excessive looseness or damage to the electrode and heating film due to excessive tightness. A fifth thermocouple and a sixth thermocouple are attached to the geometric center of the xz outer surface on both sides of the core, respectively, to ensure that the sensing end is in close contact with the xz surface. The thermocouple wires are arranged along the heat insulation direction to reduce the interference of wire heat conduction on temperature measurement accuracy.

[0043] Select a material with a thermal conductivity ≤0.03. High-efficiency thermal insulation material is used. Based on the dimensions of the xy and yz planes of the core, insulation sheets are cut to perfectly match the surface, ensuring that the edges of the insulation sheets extend at least 5mm beyond the core surface to prevent heat leakage. The insulation sheets are then attached to the two xy and two yz planes of the core and secured with high-temperature resistant straps, ensuring no gaps between the insulation material and the core surface, and that the heat loss rate of the non-exposed surfaces (xy and yz planes) is ≤1%. Only the two xz outer surfaces of the core are fully exposed to the test environment, forcing heat to be transferred only along the y direction, thus constructing strict one-dimensional heat transfer conditions and eliminating the interference of heat loss in the x and z directions on the test results.

[0044] The constant heating power is determined based on the xz surface area of ​​the core. The power supply of the second heating film is connected to the thermocouple data acquisition device. After heating is started, the temperature data of the fourth, fifth, and sixth thermocouples are collected in real time. When the rate of change of temperature readings of all three thermocouples is ≤0.5℃ / h, and this steady state is maintained for 30 minutes (excluding misjudgments caused by short-term temperature fluctuations), the system is considered to have reached thermal steady state. Record the steady-state temperature data, and calculate the thermal conductivity y using the second formula, which is:

[0045] in, The heat flux density of the first heating film in steady state. The reading difference between the thermocouple at the center of the first heating film and the thermocouple on the xz surface is the temperature difference under steady-state conditions. Let x be the width of the battery in the x-direction.

[0046] Step S3: Arrange a third heating film at the top center of the cell in the z-direction inside the battery to insulate the xz and yz surfaces and construct one-dimensional heat transfer conditions in the xy surface; record the temperature data during the heating process, and determine the z-direction thermal conductivity by iterative optimization in combination with the x-direction thermal conductivity and y-direction thermal conductivity.

[0047] like Figure 4 As shown, a square stacked battery to be tested is selected. After removing the outer metal casing, the inner core is taken out. The length (x-direction dimension) and width (y-direction dimension) of the core's z-direction projection surface are measured to determine the size of the third heating film. That is, the length is 1 / 2 of the core's z-direction projection length and the width is 1 / 2 of the core's z-direction projection width. This ensures that the heating film area is 1 / 4 of the core's z-direction projection area and can accurately cover the top geometric center area of ​​the core's z-direction.

[0048] A constant-power heating film, i.e., the third heating film, is selected and tightly adhered to the geometric center of the top z-axis of the roll core. It is fixed with high-temperature resistant insulating adhesive, ensuring the gap between the heating film and the roll core surface is ≤0.1mm to eliminate the risk of displacement. The heating power is set according to the roll core volume. A seventh thermocouple is attached to the geometric center of the third heating film surface, with the sensing end pressure controlled at 0.5-1N to prevent temperature measurement delay due to excessive looseness or damage to the roll core due to excessive tightness. An eighth thermocouple is attached to the geometric center of the xy-axis outer surface of the roll core bottom surface (z-axis bottom), again ensuring a tight fit between the sensing end and the xy-axis surface. The thermocouple wires are arranged along the insulation direction to reduce interference from wire heat conduction on temperature measurement accuracy.

[0049] Select a material with a thermal conductivity ≤0.03. High-efficiency thermal insulation material is used. Based on the dimensions of the xz and yz planes of the core, insulation sheets are cut to perfectly match the surface, ensuring the edges of the insulation sheets extend at least 5mm beyond the core surface to prevent heat leakage. The insulation sheets are then attached to the two xz and two yz planes of the core and secured with high-temperature resistant straps, ensuring no gaps between the insulation material and the core surface, and that the heat loss rate of the non-exposed surfaces is ≤1%. Only the two xy planes of the core are fully exposed to the test environment, forcing heat to be transferred only along the z direction, thus constructing strict one-dimensional heat transfer conditions and eliminating the interference of heat loss in the x and y directions on the test results.

[0050] Place the core with the heating film and thermocouple installed in the environmental chamber, connect the power supply of the third heating film to the data acquisition device (set the sampling interval to 1-5 min / time to ensure that the data density meets the requirements of subsequent simulation comparison); before starting the heating, use an anemometer to measure the real-time wind speed in the environmental chamber (record the data for subsequent heat transfer coefficient calculation), and keep the temperature of the environmental chamber stable (fluctuation ≤ ±1℃).

[0051] The constant power heating of the third heating film is started, and the data acquisition equipment is turned on simultaneously to record the temperature data of the seventh and eighth thermocouples throughout the process, forming a complete temperature-time curve. The stability of the heating power is monitored in real time during the heating process to ensure no power fluctuations and avoid affecting the validity of the temperature data.

[0052] Based on the actual dimensions of the roll core (width L in the x direction, thickness D in the y direction, and height H in the z direction), a three-dimensional simulation model is built using CFD simulation software. The model must include the internal structure of the roll core, the third heating film, and the exposed xy planes. During mesh generation, the mesh size for the internal region of the roll core should be ≤1mm, the mesh size for the heating film region should be ≤0.5mm, and the mesh size for the ambient air region should be ≤5mm to ensure the model accuracy meets the calculation requirements. The measured x-direction thermal conductivity kx, y-direction thermal conductivity ky, thermophysical parameters, boundary conditions, and initial conditions are entered into the simulation model, and the z-direction thermal conductivity is calculated through iterative optimization.

[0053] For each candidate kz value, CFD simulation is run to output the simulated temperature-time curves corresponding to the seventh and eighth thermocouples. The simulated curves are compared with the measured curves at time points to calculate the average temperature difference corresponding to each candidate kz value. The temperature difference data of all candidate kz values ​​are compared, and the candidate value that minimizes the temperature difference between TC7 and TC8 is selected as the final z-direction thermal conductivity.

[0054] To verify the effectiveness of the invention, a physical sample of a square stacked battery was selected, and tests were conducted in the width direction (x-direction), thickness direction (y-direction), and height direction (z-direction) as described above. The following are the test data for the three directions.

[0055] The test data for thermocouples TC1, TC2, and TC3 in the width direction (x-direction) are as follows: Figure 5 After approximately 10 hours, the thermocouple data showed a change of less than 0.5℃ / h, indicating that the test had reached equilibrium. The average value of the thermocouple data for the following hour was recorded, and the results were calculated. Value, according to the formula The calculated thermal conductivity in the x-direction is 13.68 W / m·℃.

[0056] The thickness direction (y-direction), the measured thermocouple data for TC4, TC5, and TC6 are as follows: Figure 6 After approximately 10 hours, the thermocouple data showed a change of less than 0.5℃ / h, indicating that the test had reached equilibrium. The average value of the thermocouple data for the following hour was recorded, and the results were calculated. Value, according to the formula The calculated thermal conductivity in the y-direction is 1.46 W / m·℃.

[0057] The test data for TC7 and TC8 thermocouples in the height direction (z-direction) are as follows: Figure 7 A constant power value was applied to the heating film to heat the battery. The entire test process lasted 2 hours, and the thermocouple data were recorded throughout the process.

[0058] Based on the above test data, and the already tested... =13.68 W / m·℃ =1.46 W / m·℃, density ρ=2202 kg / m3, heating power p=75W, input into the model, and tried. =10 W / m·℃ =12 W / m·℃ =14W / m·℃ =16 W / m·℃ =12.5 W / m·℃. By comparing with the test data, the following difference table was obtained.

[0059]

[0060] Through iterative attempts, it was found that when When the value is 12.5 W / m·℃, the difference between the measured and simulated values ​​is minimal; therefore, it is concluded that... =12.5 W / m·℃.

[0061] Example 2 This embodiment discloses a system for testing the thermal conductivity of various components of a square stacked battery. A system for testing the thermal conductivity of square stacked solar cells includes: Test stand for fixing the square stacked battery under test; The heating module includes: a first heating unit configured to be disposed at the middle cut section along the x-direction of the internal winding core of the battery; a second heating unit configured to be disposed at the middle position along the y-direction of the internal winding core of the battery and arranged along the xz plane; and a third heating unit configured to be disposed at the top center position along the z-direction of the internal winding core of the battery. The thermal insulation module, including removable thermal insulation material, is configured to selectively wrap the battery in the xy plane, xz plane, or yz plane to create one-dimensional heat transfer conditions. The temperature measurement module includes multiple thermocouples configured to measure the temperature at the center of the heating unit and a specific outer surface of the battery; The data acquisition and control module is electrically connected to the heating module and the temperature measuring module, and is configured to apply a constant power to the heating module and collect and record the temperature data of the temperature measuring module. The calculation and analysis module, which is communicatively connected to the data acquisition and control module, is configured to: calculate the x-axis thermal conductivity and y-axis thermal conductivity based on the steady-state temperature data obtained from tests in the x and y directions; construct a CFD model based on the x-axis and y-axis thermal conductivity, ambient wind speed, battery physical parameters, and z-axis heating power, and determine the z-axis thermal conductivity through an iterative optimization method.

[0062] Example 3 The purpose of this embodiment is to provide a computer-readable storage medium.

[0063] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a method for testing the thermal conductivity of various aspects of a square stacked battery as described in Example 1.

[0064] Example 4 The purpose of this embodiment is to provide an electronic device.

[0065] An electronic device includes a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in a method for testing the thermal conductivity of various components of a square stacked battery as described in Example 1.

[0066] The steps and methods involved in the apparatuses of Embodiments 2, 3, and 4 above correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood as including any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and enabling the processor to perform any of the methods in this invention.

[0067] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0068] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method of testing the coefficient of anisotropic thermal conductivity of a square- shaped stacked battery cell, characterized by, The method comprises the following steps: A first heating film is arranged at the middle cross section of the x direction of the internal winding core of the battery, the xy and xz planes are insulated, the one-dimensional heat exchange condition of the yz plane is constructed, the x direction thermal conductivity coefficient is calculated after the steady state temperature is measured; A second heating film is arranged at the middle position of the y direction of the internal winding core of the battery, the xy and yz planes are insulated, the one-dimensional heat exchange condition of the xz plane is constructed, and the y direction thermal conductivity coefficient is calculated after the steady state temperature is measured; A third heating film is arranged at the top center of the z direction of the internal winding core of the battery, the xz and yz planes are insulated, the one-dimensional heat exchange condition of the xy plane is constructed, the temperature data during the heating process is recorded, and the z direction thermal conductivity coefficient is determined through iterative optimization combined with the x direction thermal conductivity coefficient and the y direction thermal conductivity coefficient.

2. A method of testing the coefficient of anisotropic thermal conductivity of a square- shaped stacked battery cell according to claim 1, characterized in that, The method comprises the following steps: The internal winding core of the battery is cut along the middle position of the x direction, a first heating film is arranged at the cut cross section, and the two xy planes and the two xz planes of the battery are insulated, only the two yz planes are exposed to the environment, so as to construct a one-dimensional heat exchange condition; Thermocouples are arranged at the center position of the first heating film and the center positions of the two yz outer surfaces respectively, a constant power is applied to the first heating film for heating, when the temperature change rate of each thermocouple is less than a predetermined threshold, the steady state temperature data is recorded, and the x direction thermal conductivity coefficient is calculated according to a first formula.

3. A method of testing the coefficient of anisotropic thermal conductivity of a square- shaped laminated battery cell according to claim 1, characterized in that, The method comprises the following steps: A second heating film along the xz plane is arranged at the middle position of the y direction of the internal winding core of the battery, the two xy planes and the two yz planes of the battery are insulated, only the two xz planes are exposed to the environment, so as to construct a one-dimensional heat exchange condition; Thermocouples are arranged at the center position of the second heating film and the center positions of the two xz outer surfaces respectively, a constant power is applied to the second heating film for heating, when the temperature change rate of each thermocouple is less than the predetermined threshold, the steady state temperature data is recorded, and the y direction thermal conductivity coefficient is calculated according to a second formula.

4. A method of testing the coefficient of anisotropic thermal conductivity of a square- shaped stacked battery cell according to claim 2, wherein The first formula is: wherein, is the heat flux density of the first heating film at steady state, is the temperature difference between the center thermocouple and the yz surface thermocouple of the first heating film at steady state, is the width of the battery in the x direction.

5. A method of testing the coefficient of anisotropic thermal conductivity of a square- shaped stacked battery cell according to claim 3, wherein The second formula is: wherein, Q is the heat flux density of the first heating film at steady state, ΔT is the temperature difference between the center thermocouple and the xz surface thermocouple of the first heating film at steady state, W is the width of the battery in the x direction.

6. A method of testing the coefficient of anisotropic thermal conductivity of a square- shaped stacked battery cell according to claim 1, wherein, The method for determining the z direction thermal conductivity coefficient through iterative optimization comprises the following steps: According to the wind speed of the test environment, the convective heat exchange coefficient of the two xy planes exposed to the environment is calculated; A CFD model containing the geometric structure of the battery, the convective heat exchange coefficient, the density, the specific heat capacity, the heating power, the x direction thermal conductivity coefficient and the y direction thermal conductivity coefficient is constructed; In the CFD model, multiple different candidate values of the z direction thermal conductivity coefficient are tried, and simulation calculation is performed respectively to obtain the simulation temperature data corresponding to each candidate value; The simulation temperature data corresponding to each candidate value is compared with the measured temperature data, and the candidate value with the smallest difference between them is selected as the final z direction thermal conductivity coefficient.

7. A system for testing the coefficient of anisotropic thermal conductivity of a square- shaped stacked battery, characterized by, The test bench comprises a test bench body and a test fixture. ​ The heating module comprises: a first heating unit configured to be arranged in the middle of the cross section of the battery core along the x direction; a second heating unit configured to be arranged in the middle of the battery core along the y direction and arranged along the xz plane; and a third heating unit configured to be arranged in the top center of the battery core along the z direction. The heat insulation module comprises detachable heat insulation materials configured to selectively wrap the xy plane, the xz plane or the yz plane of the battery to build a one-dimensional heat exchange condition. The temperature measurement module comprises a plurality of thermocouples configured to measure the temperature of the center of the heating unit and the specific outer surface of the battery. The data acquisition and control module is electrically connected with the heating module and the temperature measurement module, configured to apply constant power to the heating module and collect and record the temperature data of the temperature measurement module. The calculation and analysis module is communicatively connected with the data acquisition and control module, configured to: calculate the x-direction thermal conductivity and the y-direction thermal conductivity according to the steady-state temperature data of the x-direction and the y-direction test; build a CFD model based on the x-direction and y-direction thermal conductivities, the environmental wind speed, the battery physical parameters and the z-direction heating power, and determine the z-direction thermal conductivity through an iterative optimization method.

8. A system for testing the coefficient of anisotropic thermal conductivity of square- shaped stacked batteries according to claim 7, characterized in that, The calculation and analysis module calculates the x-direction thermal conductivity through a first formula and calculates the y-direction thermal conductivity through a second formula. The first formula is: wherein, is the heat flux density of the first heating film at steady state, is the temperature difference between the center thermocouple and the yz surface thermocouple of the first heating film at steady state, is the width of the battery in the x direction; The second formula is: wherein, Q is the heat flux density of the first heating film at steady state, ΔT is the difference in temperature between the center thermocouple and the xz surface thermocouple of the first heating film at steady state, W is the width of the battery in the x direction.

9. A computer-readable storage medium having stored thereon a program, characterized in that, The program is executed by the processor to implement the steps in the method for testing the thermal conductivities of the square stacked battery according to any one of claims 1-6.

10. An electronic device comprising a memory, a processor, and a program stored on the memory and executable on the processor, characterized in that, The processor executes the program to implement the steps in the method for testing the thermal conductivities of the square stacked battery according to any one of claims 1-6.

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