阅读说明：本技术 一种电池隔膜热收缩率的测试方法 (method for testing thermal shrinkage rate of battery diaphragm ) 是由 田震 赵敏 王景伟 于 2019-10-14 设计创作，主要内容包括：本发明公开了一种电池隔膜热收缩率的测试方法。本发明采用摄像装置,通过直接测试隔膜在不同温度下的面积变化,得到隔膜的热收缩率。本发明方法使用的设备简单、操作方便,测试精度高。整个测试过程中都可连续自动进行,减少了人为的影响因素,通过图像处理方法得到隔膜的面积,可对任意形状的隔膜进行热收缩率的测试,并更精确地得到隔膜在不同温度下的热收缩率和不同温度下的图像信息。(The invention discloses a method for testing the thermal shrinkage rate of a battery diaphragm. The thermal shrinkage rate of the diaphragm is obtained by directly testing the area change of the diaphragm at different temperatures by adopting the camera device. The method has the advantages of simple equipment, convenient operation and high test precision. The whole testing process can be continuously and automatically carried out, artificial influence factors are reduced, the area of the diaphragm is obtained by an image processing method, the thermal shrinkage rate of the diaphragm in any shape can be tested, and the thermal shrinkage rate of the diaphragm at different temperatures and image information at different temperatures can be more accurately obtained.)

1. a method for testing the thermal shrinkage rate of a battery diaphragm is characterized by comprising the following specific steps:

(1) Flatly laying a battery diaphragm on a sample table in an oven;

(2) heating the battery diaphragm by using an oven by adopting a temperature programming method, wherein the temperature rising speed is between 0.3 ~ 10 ℃, ~ the temperature is between 30 ~ 200 ℃;

(3) shooting a battery diaphragm through a camera device, and synchronously obtaining image information of the battery diaphragm at different temperatures;

(4) Processing the obtained battery diaphragm image by an image processing method to obtain the areas of the battery diaphragm at different temperatures, wherein the area of the sample at the initial temperature is used as the initial area of the sample for calculating the thermal shrinkage rate;

(5) and calculating the thermal shrinkage rate S% of the diaphragm, wherein the formula is S% = the area of the diaphragm at different temperatures/the initial area of the diaphragm.

2. The testing method of claim 1, wherein in step (1), the sample stage is uniformly coated with a layer of talc.

3. the testing method according to claim 1, wherein in step (1), the battery separator is placed on a sample stage, and the electrolyte is placed in the sample stage.

Technical Field

The invention belongs to the technical field of energy materials, and particularly relates to a method for testing the thermal shrinkage rate of a battery diaphragm.

Background

Secondary batteries are one of the hot spots of research in the energy field today. The separator serves as an important component of a secondary battery, in which the main function is to isolate positive and negative electrodes of the battery to prevent short-circuiting of the battery and to provide a path through which lithium ions can normally pass.

during the use of the secondary battery, the overall temperature of the battery rises due to the alternation of charge and discharge processes. In the process of temperature rise, the diaphragm can shrink to different degrees and generate certain shrinkage stress, and when the shrinkage stress is large to a certain degree, the diaphragm can crack, so that the short circuit of the battery is caused and the battery is damaged. The smaller the shrinkage rate of the separator, the higher the safety of the battery.

the current method for testing shrinkage is to calculate the thermal shrinkage by measuring the change in length and width of the membrane having a regular shape at different temperatures. In both published articles and the current national standards, the shape after heat shrinkage is calculated by using a ruler-measure length method, and the method increases the error of the measurement result due to the irregularity of the shape of the diaphragm after heat shrinkage. Meanwhile, the method can only discontinuously measure the thermal shrinkage rate at one temperature at one time, and the thermal shrinkage rate of the diaphragm in the continuous heating process cannot be continuously obtained.

Disclosure of Invention

In order to overcome the disadvantages of the prior art methods, it is an object of the present invention to provide a method for more accurately measuring a battery separator. The invention obtains the areas of the diaphragms at different temperatures by an image processing method, obtains the image information of the diaphragms at different temperatures, can effectively eliminate errors caused by irregular shapes of the samples when the measurement length changes, and can obtain the image information of the samples while obtaining the heat shrinkage rate of the samples.

The technical scheme of the invention is specifically introduced as follows.

A method for testing the thermal shrinkage rate of a battery diaphragm comprises the following specific steps:

(1) flatly laying a battery diaphragm on a sample table in an oven;

(2) heating the battery diaphragm by using an oven by adopting a temperature programming method, wherein the temperature rising speed is between 0.3 ~ 10 ℃, ~ the temperature is between 30 ~ 200 ℃;

(3) Shooting the change of the battery diaphragm through a camera device, and synchronously obtaining image information of the battery diaphragm at different temperatures;

(4) Processing the obtained battery diaphragm image by an image processing method to obtain the areas of the battery diaphragm at different temperatures, wherein the area of the sample at the initial temperature is used as the initial area of the sample for calculating the thermal shrinkage rate;

(5) and calculating the thermal shrinkage rate S% of the diaphragm, wherein the formula is S% = the area of the diaphragm at different temperatures/the initial area of the diaphragm.

In the invention, in the step (1), a layer of talcum powder is uniformly coated on the sample table.

in the invention, in the step (1), the battery diaphragm is placed in a sample stage, and the electrolyte is added into the sample stage. The shrinkage behavior of the sample in the presence of the electrolyte can be obtained by placing different electrolytes in the sample stage.

Compared with the prior art, the invention has the beneficial effects that:

(1) The method has the advantages of simple equipment, convenient operation and high test precision. The whole testing process can be continuously and automatically carried out, artificial influence factors are reduced, the area of the sample is obtained by an image processing method, and the heat shrinkage rate of the sample at different temperatures can be more accurately obtained;

(2) The area of the sample is obtained by processing the image obtained by the camera device, is not directly obtained by testing the size of the sample, and can be used for testing the heat shrinkage rate of the sample in any shape;

(3) because the area direct measurement method is adopted for testing the shrinkage rate, the error generated when the length tool is used for measuring the size of the diaphragm due to the irregularity of the sample after the shrinkage by heat treatment can be effectively reduced;

(4) because the area change of the diaphragm is tested by adopting an image method, the thermal shrinkage rate of the diaphragm at different temperatures can be continuously measured;

(5) The area change is obtained by image information directly acquired by a test camera device under different real temperatures, and a sample which is subjected to heat treatment and generates shrinkage is not taken into a room temperature environment, so that the measurement deviation caused by the shape change of the sample due to the temperature change of the environment where the sample is positioned during measurement is avoided, and the reliability of the result is ensured;

(6) when the diaphragm image is processed, besides the area of the diaphragm, other image information such as the perimeter, the side length, the maximum width and the minimum width of the diaphragm can be obtained;

(7) the shrinkage behavior of the sample under the condition of the existence of the electrolyte can be obtained by adding different electrolytes into the sample stage;

(8) and image information of the diaphragm at different temperatures can be synchronously obtained in the process.

Drawings

FIG. 1 is a schematic view of a device for measuring shrinkage of a battery separator according to the present invention.

Detailed Description

the technical solution of the present invention will be described in detail with reference to the accompanying drawings and embodiments.

FIG. 1 is a device for testing the shrinkage rate of a battery diaphragm, which comprises a sample bin, an oven, a sample stage and a camera device, wherein the oven is arranged in the sample bin, the sample stage is arranged in the oven, the oven adopts an electric heating mode, the oven has a temperature programming control function, and the camera device is arranged right above the sample stage; the area of the acquired image is obtained by an image area processing method.