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CN-122016924-A - Method for measuring normal heat conductivity coefficient of soft package battery

CN122016924ACN 122016924 ACN122016924 ACN 122016924ACN-122016924-A

Abstract

The invention discloses a method for measuring normal heat conductivity coefficient of a soft package battery, and relates to the technical field of thermal physical parameter detection. The invention heats the battery in the approximate adiabatic environment with constant power through the flexible heater, respectively monitors heat flux and temperature data of the heating surface and the cooling surface of the battery by using the heat flow sensor and the thermocouple, and calculates the normal heat conductivity coefficient of the battery based on the established quasi-steady heat conductivity theoretical model after the temperature field of the battery reaches the quasi-steady state. The method is simple and convenient to operate, the normal heat conductivity coefficient can be represented by monitoring the heat flux and the temperature in the heating process of the battery, the measurement period is short, the completion is realized within 20 minutes, the precision is high, the cost is low, and key support can be provided for the design of a battery thermal management system.

Inventors

  • SHI WEIWEI
  • ZHOU YUETING
  • SHENG LEI
  • LV YING

Assignees

  • 仪征亚新科双环活塞环有限公司

Dates

Publication Date
20260512
Application Date
20260320

Claims (8)

  1. 1. The method for measuring the normal heat conductivity coefficient of the soft package battery is characterized by comprising the following steps of: S1, sample pretreatment, namely wrapping a soft package battery by adopting a heat preservation material, and then placing the soft package battery in a constant temperature environment, wherein the small side surface of the battery is taken as a heat insulation surface; S2, arranging a testing device, namely attaching a flexible heater to the main surface of the battery, and respectively arranging a heat flow sensor and a thermocouple at the central positions of the heating surface and the cooling surface, wherein the heat flow sensor is used for collecting heat flux, and the thermocouple is used for collecting temperature; s3, constructing a constant temperature environment, namely placing the arranged testing device in a cavity of the thermostat, and setting the initial temperature of the cavity to enable the temperature of the sample to be consistent with the temperature of the cavity; S4, heat excitation loading and data acquisition, namely, supplying power to the flexible heater through a stabilized voltage power supply, heating the main surface of the sample, namely the heating surface, with constant power, and simultaneously recording heating time, heat flux and temperature change of the heating surface and the cooling surface, and stopping heating until the set upper limit temperature threshold is reached; s5, judging the quasi-steady state, namely calculating the temperature difference between the heating surface and the cooling surface of the battery according to the acquired temperature data, and judging that the temperature field of the battery reaches the quasi-steady state when the temperature difference tends to be constant within the preset time; S6, calculating a normal heat conduction coefficient, namely deducing a theoretical model of the normal heat conduction coefficient of the battery based on a Fourier heat conduction law and an energy conservation law, substituting the temperature difference, the heat flux and the battery size under a quasi-steady state into the model, and calculating to obtain the normal heat conduction coefficient, wherein the normal heat conduction coefficient is calculated according to the following formula: wherein: For normal thermal conductivity, L is the cell thickness, For a constant heating power density of the heating surface, For the heat flux of the heating surface, For cooling surface heat flux, a is heating film surface area, For the temperature of the heating surface, Is the cooling surface temperature.
  2. 2. The method for measuring normal thermal conductivity of a soft package battery according to claim 1, wherein, The heat insulation material contacted with the battery in the S1 is an aerogel felt, the outside of the heat insulation material is coated with an expanded polystyrene heat insulation material, and the thickness of the aerogel felt is 20 mm.
  3. 3. The method for measuring normal thermal conductivity of a soft package battery according to claim 2, wherein, The sample in S1 is a soft package lithium ion battery, including ternary soft package lithium ion batteries, lithium iron phosphate soft package lithium ion batteries and other types of square soft package batteries.
  4. 4. The method for measuring normal thermal conductivity of a soft battery according to claim 3, wherein, And S2, the precision of the heat flow sensor is +/-2%, the thermocouple is a T-shaped thermocouple, the wire diameter is 0.26 mm, the precision is +/-0.4%, and the size of the flexible heater is matched with the main surface size of the sample.
  5. 5. The method for measuring normal thermal conductivity of a flexible battery according to claim 4, wherein, S4, the input power of the flexible heater meets the condition that the temperature difference between the heating surface and the cooling surface of the sample is 5-15 ℃, and the upper limit temperature threshold is 65 ℃; And S4, heating power is constant, and the actual output power of the flexible heater is monitored and recorded in real time through a direct-current power supply.
  6. 6. The method for measuring normal thermal conductivity of a flexible battery according to claim 5, wherein, And S5, when the preset time is 84 seconds and the temperature difference tends to be constant after 84 seconds, determining the current time node as a temperature field steady-state starting point, and calculating by adopting temperature and heat flux data after the current node.
  7. 7. The method for measuring normal thermal conductivity of a flexible battery according to claim 6, wherein, And S7, verifying the method, namely taking a quartz glass block with known thermal parameters as a standard sample, measuring according to S1-S6, and judging that the measuring method is effective when the measurement error of the thermal conductivity coefficient of the standard sample is less than or equal to 6.5%.
  8. 8. The method for measuring normal thermal conductivity of a soft battery according to any one of claims 1-7, The normal thermal conductivity of the sample in the temperature range of-20-60 ℃ can be measured, and the characterization of the normal thermal conductivity of the sample at different working temperatures is realized by changing the initial temperature.

Description

Method for measuring normal heat conductivity coefficient of soft package battery Technical Field The invention relates to the technical field of thermal physical parameter detection, in particular to a method for measuring normal heat conductivity coefficient of a soft package battery. Background The lithium ion battery is used as a core power source of the electric automobile, and the thermophysical parameters of the lithium ion battery are key bases for analyzing the thermal behavior of the battery and designing a thermal management system of the battery. The advantages of high energy density, no memory effect in charge and discharge and the like of the large soft-package lithium ion battery are widely applied, but the thermophysical parameters are rarely provided in the manufacturer data manual, the influence of the working temperature on the heat conductivity of the battery is not fully researched, and an accurate and efficient measuring method is needed to represent the normal heat conductivity of the battery. The existing lithium ion battery heat conductivity coefficient measurement method has the defects that instruments required by a Xenon Flash Technology (XFT) are expensive, large in size and not widely supplied, and a large amount of numerical simulation work is needed by a method based on a heat conduction principle, so that the workload is large, and the influence of working temperature on the heat conductivity coefficient is not considered. In addition, the existing method is more aimed at cylindrical and square hard-shell batteries, and a special measuring method for large soft-package lithium ion batteries is rarely reported, so that the actual requirements of battery thermal management system design are difficult to meet. Aiming at the problems, a method for measuring the normal heat conductivity coefficient of the soft package battery is provided to make up for the defects of the normal heat conductivity coefficient measuring technology of the battery. Disclosure of Invention In view of the above, the invention provides a method for measuring the normal thermal conductivity coefficient of a soft package battery, which is used for solving the problems of high measurement cost, long period and inapplicability to large-size samples in the prior art. In order to achieve the above purpose, the present invention adopts the following technical scheme: a method for measuring normal heat conductivity coefficient of a soft package battery comprises the following steps: S1, sample pretreatment, namely wrapping a soft package battery by adopting a heat preservation material, and then placing the soft package battery in a constant temperature environment, wherein the small side surface of the battery is taken as a heat insulation surface; S2, arranging a testing device, namely attaching a flexible heater to the main surface of the battery, and respectively arranging a heat flow sensor and a thermocouple at the central positions of the heating surface and the cooling surface, wherein the heat flow sensor is used for collecting heat flux, and the thermocouple is used for collecting temperature; s3, constructing a constant temperature environment, namely placing the arranged testing device in a cavity of the thermostat, and setting the initial temperature of the cavity to enable the temperature of the sample to be consistent with the temperature of the cavity; S4, heat excitation loading and data acquisition, namely, supplying power to the flexible heater through a stabilized voltage power supply, heating the main surface of the sample, namely the heating surface, with constant power, and simultaneously recording heating time, heat flux and temperature change of the heating surface and the cooling surface, and stopping heating until the set upper limit temperature threshold is reached; s5, judging the quasi-steady state, namely calculating the temperature difference between the heating surface and the cooling surface of the battery according to the acquired temperature data, and judging that the temperature field of the battery reaches the quasi-steady state when the temperature difference tends to be constant within the preset time; S6, calculating a normal heat conduction coefficient, namely deducing a theoretical model of the normal heat conduction coefficient of the battery based on a Fourier heat conduction law and an energy conservation law, substituting the temperature difference, the heat flux and the battery size under a quasi-steady state into the model, and calculating to obtain the normal heat conduction coefficient, wherein the normal heat conduction coefficient is calculated according to the following formula: wherein: For normal thermal conductivity, L is the cell thickness, For a constant heating power density of the heating surface,For the heat flux of the heating surface,For cooling surface heat flux, a is heating film surface area,For the temperature of the heating surface,Is the cool