Method and apparatus for measuring battery heat generation rate

Abstract

This invention relates to a method and apparatus for measuring the heat generation rate of a battery. The method includes: arranging temperature and heat measurement units on two relatively large surfaces of the battery, wherein the units are arranged along a first diagonal direction on the first large surface and along a second diagonal direction intersecting the first diagonal direction on the second large surface. Each temperature and heat measurement unit includes multiple thin-film heat flow meters and thermocouples corresponding to each thin-film heat flow meter; covering the battery surface with an insulating layer; placing the battery in a temperature-controlled environment and connecting it to a charging and discharging device to make the battery temperature consistent with the initial temperature of the temperature-controlled environment; applying a charging and discharging current to the battery and simultaneously acquiring the temperature signals measured by each thermocouple and the voltage signals output by each thin-film heat flow meter; and calculating the instantaneous heat generation rate of the battery based on the temperature and voltage signals. This invention features fast response, high testing efficiency, and the ability to reflect the spatial distribution characteristics of heat generation.

Description

Technical Field

[0001] This invention relates to the field of battery thermal characteristic measurement technology, and in particular to a method and apparatus for measuring battery heat generation rate. Background Technology

[0002] With the large-scale application of lithium-ion batteries in new energy electric vehicles and energy storage systems, battery thermal safety and thermal management technology have become key factors restricting their performance and lifespan assessment. Battery heat generation rate, as a core thermophysical parameter characterizing the battery's heat generation properties, directly determines the rate of temperature rise and heat accumulation during charging and discharging, and is an important basis for optimizing battery thermal management system design, preventing thermal runaway, and assessing battery cycle life. Currently, the main methods for measuring battery heat generation rate include adiabatic accelerated calorimetry (ARC) and calibration calorimetry. ARC calculates the heat generation rate based on the adiabatic temperature rise rate by real-time tracking of the battery temperature and adjusting the calorimetric chamber temperature to create a near-adiabatic environment. However, due to the large thermal inertial mass of the calorimetric chamber, ARC equipment exhibits a significant lag in temperature response, making it difficult to accurately capture the transient heat generation characteristics corresponding to second-level current fluctuations under actual driving conditions (such as the WLTC cycle, the World Light Vehicle Test Cycle). Furthermore, ARC equipment has inherent drawbacks such as large size, high procurement costs, and high operating energy consumption. While calibration calorimetry can reduce equipment costs to some extent, it relies on a long natural cooling process to obtain the thermal loss calibration curve. A single test cycle usually takes several hours, making it impossible to achieve large-scale rapid testing of battery heat generation rate and difficult to adapt to the continuous measurement needs under dynamic operating conditions.

[0003] For battery cells with high aspect ratios, such as blade batteries, the internal structure often exhibits significant non-uniform heat generation characteristics due to factors such as uneven distribution of electrode materials, differences in tab structure, and uneven current density distribution. The local heat generation rate varies significantly in different regions. Currently, it is difficult to effectively analyze the spatial distribution characteristics of local heat generation rate in different regions of such batteries while ensuring testing efficiency and measurement accuracy. Summary of the Invention

[0004] Therefore, it is necessary to provide a method and apparatus for measuring battery heat generation rate that combines fast response, high testing efficiency, and the ability to reflect the spatial distribution characteristics of heat generation, in order to address the above-mentioned technical problems.

[0005] This invention provides a method for determining the heat generation rate of a battery, comprising:

[0006] Temperature and heat measurement units are arranged on two relatively large surfaces of the battery. The units are arranged along a first diagonal direction on the first large surface and along a second diagonal direction that intersects the first diagonal direction on the second large surface. Each temperature and heat measurement unit includes multiple thin-film heat flow meters and thermocouples corresponding to each thin-film heat flow meter.

[0007] An insulating layer is applied to the outer surface of the battery in which the temperature and heat measurement unit is arranged.

[0008] The battery is placed in a temperature-controlled environment and connected to a charging and discharging device so that the battery temperature is consistent with the initial temperature of the temperature-controlled environment.

[0009] A charging and discharging current is applied to the battery, and the temperature signals measured by each thermocouple and the voltage signals output by each thin-film heat flow meter based on the Seebeck effect are collected simultaneously.

[0010] Based on the collected temperature and voltage signals, the instantaneous heat generation rate of the battery is directly calculated according to the principle of energy conservation.

[0011] In one embodiment, the thin-film heat flow meter is composed of pairs of P-type and N-type BiTe material particles, and the whole is covered by a polyimide film or a ceramic film. The thickness of the thin-film heat flow meter is 0.05-0.5 mm. The thermal conductivity specific thermal resistance of the thin-film heat flow meter is less than one-tenth of the sum of the thermal conductivity specific thermal resistance of the insulation layer and the external convection specific thermal resistance.

[0012] In one embodiment, on each of the large surfaces, the temperature and heat measurement unit includes a central temperature measurement unit located at the geometric center of the battery, an edge temperature measurement unit located at a distance of one-tenth of the length and one-tenth of the height from the battery apex, and a mid-temperature point temperature measurement unit located at the midpoint of the line connecting the central temperature measurement unit and the edge temperature measurement unit; wherein, on the first large surface, the edge temperature measurement unit, the mid-temperature point temperature measurement unit, and the central temperature measurement unit are arranged sequentially along a first diagonal direction, and on the second large surface, corresponding temperature and heat measurement units are arranged sequentially along a second diagonal direction intersecting the first diagonal direction.

[0013] In one embodiment, the insulation layer is made of aerogel or foamed nitrile rubber and is wrapped around the outer surface of the battery on which the temperature and heat measurement unit is arranged. The thin-film heat flow meter is located between the battery and the insulation layer. The thermal conductivity of the insulation layer is not higher than 0.06 W / mK, the specific gravity is less than 0.5, and its thermal resistance is greater than ten times the sum of the thermal resistance from the center to the outer shell inside the battery and the external convective thermal resistance.

[0014] In one embodiment, the step of directly calculating the instantaneous heat generation rate of the battery based on the acquired temperature signal and voltage signal according to the principle of energy conservation includes:

[0015] Based on the temperature signals measured by each of the thermocouples and the voltage signal output by each of the aforementioned thin-film heat flow meters Calculate the heat flux density at each measuring point according to the following formula. :

[0016] ,

[0017] in, The calibration coefficient for the thin-film heat flow meter is given by V (W / m²), and T is the temperature (°C).

[0018] Calculate the average heat flux density at all measuring points. :

[0019] ,

[0020] in, This represents the total number of thin-film heat flow meters;

[0021] The instantaneous heat generation rate of the battery is calculated according to the following formula. :

[0022] ,

[0023] in, For the specific heat capacity of the battery, For battery quality, For the battery temperature rise rate, This represents the surface area of ​​the battery.

[0024] In one embodiment, the method further includes:

[0025] Based on local temperature signals and local heat flux density Calculate the battery's first charge according to the following formula. Instantaneous heat generation rate of a local area To detect uneven heat generation in the battery:

[0026] ,

[0027] in, For the first The quality of a local region For the first A large area of ​​a local region.

[0028] In one embodiment, on each of the large surfaces, the thin-film heat flow meter and thermocouple are arranged only at the mid-temperature point temperature measurement unit to calculate the average heat loss rate of the battery based on the heat flux density and temperature measured at the mid-temperature point.

[0029] In one embodiment, applying a charging and discharging current to the battery specifically involves applying a charging and discharging current based on WLTC dynamic operating conditions and exhibiting second-level current fluctuations; the synchronous acquisition acquires the temperature signal and voltage signal in real time at a sampling frequency corresponding to the current fluctuations.

[0030] In one embodiment, the thin-film heat flow meter is attached to the outer surface of the battery with thermally conductive silicone grease and fixed with high-temperature resistant tape; the thermocouple is fixed to the battery casing by adhesive aluminum film or welding.

[0031] The present invention also provides a battery heat generation rate measuring device, comprising:

[0032] A temperature and heat measurement unit is used to attach to two relatively large surfaces of the battery, wherein it is arranged along a first diagonal direction on the first large surface and along a second diagonal direction intersecting the first diagonal direction on the second large surface. The temperature and heat measurement unit array includes multiple thin-film heat flow meters and thermocouples corresponding to each thin-film heat flow meter.

[0033] A thermal insulation coating layer is used to tightly wrap the outside of the battery on which the temperature and heat measurement unit is arranged;

[0034] An ambient temperature control unit is used to house the battery and provide a constant initial temperature environment;

[0035] The data acquisition unit is electrically connected to each of the thermocouples and each of the thin-film heat flow meters, and is used to synchronously acquire temperature signals and voltage signals;

[0036] A charging / discharging unit is electrically connected to the battery to provide charging / discharging current;

[0037] The device directly calculates the instantaneous heat generation rate of the battery based on the temperature signal and voltage signal acquired by the data acquisition unit, according to the principle of energy conservation.

[0038] The aforementioned method and apparatus for measuring battery heat generation rate utilizes a temperature and heat measurement unit composed of a thin-film heat flow meter and thermocouples arranged along a diagonal direction intersecting the two large surfaces of the battery. This unit is then covered with an insulating layer to construct a controllable insulating boundary, enabling direct, in-situ measurement of heat flow lost from the battery surface. Based on the directly measured heat flow data and simultaneously measured temperature data, and according to the principle of energy conservation, the instantaneous heat generation rate of the battery can be directly calculated. This method eliminates the need for a long natural cooling process, as required by calibration calorimetry, to calibrate the heat loss coefficient, significantly shortening the testing cycle and enabling rapid measurement of the heat generation rate. Furthermore, because the thin-film heat flow meter is thin and has a fast thermal response, and the entire measurement system does not rely on adjusting the temperature of the ambient cavity with high thermal inertia to track the battery temperature, it can accurately capture the instantaneous heat generation characteristics that change on a second-by-second basis under dynamic charge and discharge conditions. This overcomes the response lag problem caused by the thermal inertia of the calorimetric cavity in traditional adiabatic accelerated calorimetry (ARC). In addition, multiple measuring points arranged in a specific direction on the two large surfaces can cover the key temperature and heat flow distribution areas of the battery surface, providing the necessary test data basis for subsequent evaluation of the spatial distribution of heat generation caused by structural or material inhomogeneity, such as blade batteries. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in this 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 This is a flowchart of a battery heat generation rate measurement method according to one embodiment;

[0041] Figure 2 This is a schematic diagram of the battery sensor installation method;

[0042] Figure 3 A schematic diagram illustrating another mounting method for the battery sensor;

[0043] Figure 4 The graph shows the temperature change of various parts of the battery over time.

[0044] Figure 5 A graph showing the change in heat flux density of various parts of the battery over time.

[0045] Figure 6 A graph showing the weighted heat generation rate of the battery over time.

[0046] Figure 7 This is a time-varying curve of battery current versus vehicle speed based on WLTC dynamic operating conditions.

[0047] Figure 8 The graph shows the changes in instantaneous current and temperature of the battery over time.

[0048] Figure 9 This is a graph showing the change in the instantaneous heat generation rate of the battery.

[0049] Figure label:

[0050] 210. Temperature and heat measurement unit; 212. Center temperature measurement unit; 214. Edge temperature measurement unit; 216. Mid-temperature point temperature measurement unit; 50. Battery. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0052] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or there may be an intermediate component. When a component is considered to be "connected to" another component, it can be directly connected to the other component or there may be an intermediate component present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this specification are for illustrative purposes only and do not represent the only possible implementation.

[0053] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0054] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature and the second feature are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0055] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0056] The following is combined Figures 1-9 The present invention describes a method and apparatus for measuring the heat generation rate of a battery.

[0057] like Figure 1 As shown, in one embodiment, a method for determining battery heat generation rate includes the following steps:

[0058] Step S110: Temperature and heat measurement units are arranged on two relatively large surfaces of the battery. The units are arranged along the first diagonal direction on the first large surface and along the second diagonal direction intersecting the first diagonal direction on the second large surface. Each temperature and heat measurement unit includes multiple thin-film heat flow meters and thermocouples corresponding to each thin-film heat flow meter.

[0059] The direction of the second diagonal (e.g., diagonal CD) is preferably opposite to that of the first diagonal (e.g., diagonal AB), so that the temperature and heat measurement units 210 on the two large surfaces are staggered and overlapped. The thin-film heat flow meter and thermocouple of each temperature and heat measurement unit 210 are arranged adjacent to each other. See [reference needed]. Figure 2 and Figure 3 The thin-film heat flow meter is composed of pairs of P-type and N-type BiTe material particles, and is entirely covered by a polyimide or ceramic film with a thickness of 0.05~0.5mm. Based on the Seebeck effect, the hot side of the heat flow meter is attached to the outer surface of the battery, and the cold side faces the insulation layer. Multiple pairs of series-connected P-type and N-type BiTe material particles generate a voltage signal under the influence of temperature difference, and its time constant is matched to or lower than the time step of heat flow acquisition to ensure rapid response to transient heat flow. The thermal resistance of the thin-film heat flow meter itself is much smaller than the sum of the thermal resistance of the insulation layer and the external convective thermal resistance, typically less than one-fifth to one-tenth of the sum. Considering a 0.3mm thick heat flow meter composed of a polyimide film and BiTe material particles, its thermal resistance is 0.001Km. 2 / W, significantly less than the thermal conductivity and specific thermal resistance of 0.5 Km for a 10mm aerogel insulation layer. 2 / W has a thermal resistance of 0.1 km compared to external convection. 2 / W sum.

[0060] On each large surface, the temperature and heat measurement unit 210 includes a central temperature measurement unit 212 located at the geometric center of the battery, an edge temperature measurement unit 214 located at a distance of one-tenth of the battery's length and one-tenth of its height from the apex, and a mid-temperature point temperature measurement unit 216 located at the midpoint of the line connecting the central temperature measurement unit 212 and the edge temperature measurement unit 214. The central temperature measurement unit 212 monitors the battery's highest temperature, the edge temperature measurement unit 214 reflects the temperature characteristics at the battery's edge due to material inhomogeneity and the gap between the electrode active material and the terminals, and the mid-temperature point temperature measurement unit 216 represents the average temperature between the battery's highest and lowest temperatures. The edge temperature measurement unit 214, the mid-temperature point temperature measurement unit 216, and the central temperature measurement unit 212 are arranged sequentially along the first diagonal direction on the first large surface. Corresponding temperature and heat measurement units 210 are arranged sequentially along the second diagonal direction intersecting the first diagonal direction on the second large surface, thus forming an interleaved temperature measurement array.

[0061] Step S120: Cover the outer surface of the battery with the temperature and heat measurement unit with a heat insulation layer.

[0062] The insulation layer, composed of aerogel or foamed nitrile rubber, wraps around the outer surface of the battery, where temperature and heat measurement units are located. A thin-film heat flow meter is positioned between the battery and the insulation layer. This insulation layer is 5-20 mm thick and is tightly sealed with high-temperature tape to prevent air leakage. Its thermal conductivity is no higher than 0.06 W / mK, its specific gravity is less than 0.5, and its specific thermal resistance is much greater than the internal thermal resistance from the center to the outer shell of the battery, exceeding it by five to ten times the sum of the internal thermal resistance from the center to the outer shell and the external convective thermal resistance. Aerogel is heat-resistant to temperatures above 600 degrees Celsius, while foamed nitrile rubber is heat-resistant to 150 degrees Celsius. For example, with a 10 mm aerogel insulation layer, the specific thermal resistance is 0.01 m / (0.02 W / mK) = 0.5 km. 2 / W, while for a battery with a thickness of 15mm and a normal thermal conductivity of 1.2W / mK, the specific thermal resistance from the center to the large surface area is 0.0075m / 1.2 = 0.0063Km. 2 / W, the thermal conductivity specific thermal resistance of the aerogel insulation layer is much smaller than the specific thermal resistance of the battery and the external convection specific thermal resistance by 0.1 km. 2 The sum of / W ensures a uniform temperature inside and on the surface of the battery. This also means that heat loss between the battery and the outside environment is mainly determined by the heat conduction of the insulation layer rather than by the convection of the outside air, thereby reducing the sources of error caused by fluctuations in heat transfer due to external air convection (which can fluctuate by up to 20%).

[0063] Step S130: Place the battery in a temperature-controlled environment and connect it to a charging / discharging device to make the battery temperature match the initial temperature of the temperature-controlled environment.

[0064] In step S140, a charging and discharging current is applied to the battery, and the temperature signals measured by each thermocouple and the voltage signals output by each thin-film heat flow meter based on the Seebeck effect are collected simultaneously.

[0065] Applying a charge / discharge current to the battery specifically involves applying a charge / discharge current with second-level current fluctuations based on WLTC dynamic operating conditions (see reference). Figure 7 Simultaneously, temperature and voltage signals are acquired in real time at a sampling frequency corresponding to current fluctuations.

[0066] Step S150: Based on the collected temperature and voltage signals, the instantaneous heat generation rate of the battery is directly calculated according to the principle of energy conservation.

[0067] Specifically, the calculation process for the instantaneous heat generation rate of a battery includes:

[0068] Based on the temperature signals measured by each thermocouple and the voltage signals output by each thin-film heat flux meter According to the formula Calculate the heat flux density at each measuring point. (Reference Figure 5 ),in, The calibration coefficient for the thin-film heat flow meter (unit: V / (W / m²)); calculate the average heat flux density at all measuring points. ,in, The total number of thin-film heat flow meters; according to the formula Calculate the instantaneous heat generation rate of the battery (Reference Figure 9 ),in For the specific heat capacity of the battery, For battery quality, For based on Figure 4 The battery temperature rise rate obtained from the temperature curve shown. The surface area of ​​the battery and the average heat flux density. Multiply by the battery surface area And in the time interval The total heat loss can be obtained by integrating. The method also includes using local temperature signals. and local heat flux density According to the formula Calculate the battery number Instantaneous heat generation rate of a local area To detect uneven battery heat generation caused by inconsistencies in materials, processes, and current distribution (refer to...) Figure 6 ),in For the first The quality of a local region For the first The large area of ​​a local region can be expressed by the formula The weighted heat production rate is calculated to reflect the differences in heat production at the top left average, center, bottom right average, top middle average, and bottom middle average of the battery.

[0069] In one embodiment, see Figure 3 On each large surface, a thin-film heat flow meter and thermocouple are arranged only at the mid-temperature measurement unit. The average heat loss rate of the battery is calculated based on the heat flux density and temperature measured at this mid-temperature point. This simplified arrangement has been experimentally verified to be consistent with the average heat generation rate obtained using all sensors. See [link to documentation]. Figure 6 The weighted heat generation rate curves of the upper and lower 1 / 4 and the average heat generation curve of the battery show that the heat generation rate at the mid-temperature point basically reflects the average heat generation rate of the battery. Thus, without affecting the measurement accuracy, the number of sensors is reduced, and the instantaneous heat generation rate of the battery can still be accurately obtained.

[0070] In terms of installation structure, the thin-film heat flow meter is bonded to the outer surface of the battery with thermally conductive silicone grease to reduce contact thermal resistance and is fixed with high-temperature resistant tape; the thermocouple is fixed to the battery casing by adhesive aluminum film or welding. To further accurately measure battery temperature and heat flow, the blue film on the battery surface can be removed before placing the heat flow meter and thermocouple.

[0071] When conducting WLTC dynamic operating condition testing (refer to...) Figure 7 (Vehicle speed and current curves), preset the initial temperature of the temperature control box to 25℃, charge and discharge the battery according to the current obtained from the WLTC operating condition conversion, continuously record until the battery reaches the cutoff voltage, and simultaneously obtain the battery average temperature and current curves (refer to...). Figure 8 And the instantaneous heat production rate curve was calculated (refer to...). Figure 9 ).

[0072] In addition, the present invention also provides a battery heat generation rate measuring device.

[0073] In one embodiment, a battery heat generation rate measuring device includes a temperature and heat measurement unit, an insulation coating layer, an ambient temperature control unit, a data acquisition unit, and a charge and discharge unit.

[0074] A temperature and heat measurement unit is attached to two relatively large surfaces of the battery. It is arranged along a first diagonal on the first large surface and along a second diagonal intersecting the first diagonal on the second large surface. Each unit includes multiple thin-film heat flow meters and thermocouples corresponding to each meter. An insulating coating layer tightly covers the outside of the battery with the temperature and heat measurement units. An environmental temperature control unit houses the battery and provides a constant initial temperature environment. A data acquisition unit is electrically connected to each thermocouple and thin-film heat flow meter to synchronously acquire temperature and voltage signals. This data acquisition unit is controlled by a computer program and is responsible for switch control, parameter and data setting, and data storage. A charge / discharge unit is electrically connected to the battery to provide charge / discharge current. Based on the temperature and voltage signals acquired by the data acquisition unit, the device directly calculates the instantaneous heat generation rate of the battery according to the principle of energy conservation.

[0075] The aforementioned method and apparatus for determining battery heat generation rate are applicable to various battery types, including prismatic batteries, blade batteries, pouch batteries, and cylindrical batteries. The heat generation rate is directly obtained through instantaneous and continuous measurement of temperature using a heat flow meter, without the need for other calibration processes. This achieves accurate and in-situ direct measurement, overcoming the shortcomings of the ARC method, such as reaction lag due to the large thermal inertia of the calorimetric chamber under second-level current changes, expensive and bulky equipment, and excessively long natural cooling time required for calibration calorimetry. It can meet the needs of the battery thermal testing and thermal management field for rapid and accurate measurement of transient heat generation rate.

[0076] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0077] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for determining the heat generation rate of a battery, characterized in that, include: Temperature and heat measurement units are arranged on two relatively large surfaces of the battery. The units are arranged along a first diagonal direction on the first large surface and along a second diagonal direction that intersects the first diagonal direction on the second large surface. Each temperature and heat measurement unit includes multiple thin-film heat flow meters and thermocouples corresponding to each thin-film heat flow meter. An insulating layer is applied to the outer surface of the battery in which the temperature and heat measurement unit is arranged. The battery is placed in a temperature-controlled environment and connected to a charging and discharging device so that the battery temperature is consistent with the initial temperature of the temperature-controlled environment. A charging and discharging current is applied to the battery, and the temperature signals measured by each thermocouple and the voltage signals output by each thin-film heat flow meter based on the Seebeck effect are collected simultaneously. Based on the collected temperature and voltage signals, the instantaneous heat generation rate of the battery is directly calculated according to the principle of energy conservation.

2. The method for determining battery heat generation rate according to claim 1, characterized in that, The thin-film heat flow meter is composed of pairs of P-type and N-type BiTe material particles, and the whole is covered by a polyimide film or a ceramic film; the thickness of the thin-film heat flow meter is 0.05-0.5mm; the thermal conductivity specific thermal resistance of the thin-film heat flow meter is less than one-tenth of the sum of the thermal conductivity specific thermal resistance of the insulation layer and the external convection specific thermal resistance.

3. The method for determining battery heat generation rate according to claim 1, characterized in that, On each of the large surfaces, the temperature and heat measurement unit includes a central temperature measurement unit located at the geometric center of the battery, an edge temperature measurement unit located at a distance of one-tenth of the length and one-tenth of the height from the battery apex, and a mid-temperature point temperature measurement unit located at the midpoint of the line connecting the central temperature measurement unit and the edge temperature measurement unit; wherein, on the first large surface, the edge temperature measurement unit, the mid-temperature point temperature measurement unit, and the central temperature measurement unit are arranged sequentially along the first diagonal direction, and on the second large surface, the corresponding temperature and heat measurement units are arranged sequentially along the second diagonal direction intersecting the first diagonal direction.

4. The method for determining battery heat generation rate according to claim 1, characterized in that, The insulation layer is made of aerogel or foamed nitrile rubber and is wrapped around the outer surface of the battery on which the temperature and heat measurement unit is arranged. The thin-film heat flow meter is located between the battery and the insulation layer. The thermal conductivity of the insulation layer is not higher than 0.06 W / mK, the specific gravity is less than 0.5, and its thermal resistance is greater than ten times the sum of the thermal resistance from the center to the outer shell inside the battery and the external convective thermal resistance.

5. The method for determining the heat generation rate of a battery according to claim 1, characterized in that, The instantaneous heat generation rate of the battery is directly calculated based on the collected temperature and voltage signals according to the principle of energy conservation, including: Based on the temperature signals measured by each of the thermocouples and the voltage signal output by each of the aforementioned thin-film heat flow meters Calculate the heat flux density at each measuring point according to the following formula. : ， in, Here is the calibration coefficient for the thin-film heat flow meter, and T is the temperature; Calculate the average heat flux density at all measuring points. : ， in, This represents the total number of thin-film heat flow meters; The instantaneous heat generation rate of the battery is calculated according to the following formula. : ， in, For the specific heat capacity of the battery, For battery quality, For the battery temperature rise rate, This represents the surface area of ​​the battery.

6. The method for determining battery heat generation rate according to claim 5, characterized in that, The method further includes: Based on local temperature signals and local heat flux density Calculate the battery's first charge according to the following formula. Instantaneous heat generation rate of a local area To detect uneven heat generation in the battery: ， in, For the first The quality of a local region For the first A large area of ​​a local region.

7. The method for determining battery heat generation rate according to claim 1, characterized in that, On each of the large surfaces, the thin-film heat flow meter and thermocouple are arranged only at the intermediate temperature point temperature measurement unit to calculate the average heat loss rate of the battery based on the heat flow density and temperature measured at that intermediate temperature point.

8. The method for determining battery heat generation rate according to claim 1, characterized in that, The application of actual operating condition charging and discharging current to the battery specifically refers to the application of charging and discharging current based on WLTC dynamic operating conditions and having second-level current fluctuations; the synchronous acquisition acquires the temperature signal and voltage signal in real time at a sampling frequency corresponding to the current fluctuations.

9. The method for determining the heat generation rate of a battery according to claim 1, characterized in that, The thin-film heat flow meter is attached to the outer surface of the battery with thermally conductive silicone grease and fixed with high-temperature resistant tape; the thermocouple is fixed to the battery casing with adhesive aluminum film or by welding.

10. A device for measuring the heat generation rate of a battery, characterized in that, include: A temperature and heat measurement unit is used to attach to two relatively large surfaces of the battery, wherein it is arranged along a first diagonal direction on the first large surface and along a second diagonal direction intersecting the first diagonal direction on the second large surface. The temperature and heat measurement unit array includes multiple thin-film heat flow meters and thermocouples corresponding to each thin-film heat flow meter. A thermal insulation coating layer is used to tightly wrap the outside of the battery on which the temperature and heat measurement unit is arranged; An ambient temperature control unit is used to house the battery and provide a constant initial temperature environment; The data acquisition unit is electrically connected to each of the thermocouples and each of the thin-film heat flow meters, and is used to synchronously acquire temperature signals and voltage signals; A charging / discharging unit is electrically connected to the battery to provide charging / discharging current; The device directly calculates the instantaneous heat generation rate of the battery based on the temperature signal and voltage signal acquired by the data acquisition unit, according to the principle of energy conservation.

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