Diaphragm thermal shrinkage evaluation method

Abstract

The invention relates to a diaphragm thermal shrinkage evaluation method. The method comprises the steps of taking a diaphragm to be measured, making a cross mark on the diaphragm to be measured, the cross mark comprising a transverse line and a longitudinal line, and measuring the original lengths of the transverse line and the longitudinal line; winding the diaphragm with the cross mark, a positive plate and a negative plate into a battery cell, wherein the diaphragm is positioned between the positive plate and the negative plate; putting the battery cell at a specified test temperature, keeping the temperature constant for a certain time, taking out, disassembling and taking out the diaphragm for evaluation; measuring the lengths of a transverse line and a longitudinal line after the cross mark on the diaphragm is cooled to room temperature, calculating the transverse shrinkage rate and the longitudinal shrinkage rate of the diaphragm, measuring and calculating the approximate area of an arc-shaped shrinkage area at the edge of the diaphragm, and calculating the ratio of the approximate area to the winding single-fold area of the diaphragm; and evaluating the safety risk level of the measured diaphragm by taking the longitudinal shrinkage rate and the area ratio as evaluation indexes. Compared with the prior art, the evaluation method provided by the invention has the advantage that the accuracy and operability of diaphragm thermal shrinkage evaluation are improved.

Description

technical field [0001] The invention belongs to the technical field of diaphragms, and in particular relates to a method for evaluating thermal shrinkage of diaphragms. Background technique [0002] After entering the 21st century, lithium-ion batteries have made great progress in terms of energy density, rate, cycle life, etc., and are used in all areas of life, especially 3C products have become an indispensable tool in life. Lithium-ion batteries are the main power solution for 3C products, and their safety is always a key factor that consumers pay attention to. [0003] Diaphragm is one of the four main materials of lithium battery. Its main function is to separate the positive and negative poles of the battery, prevent the two poles from contacting and short circuit, and avoid the internal thermal runaway and fire of the battery. It can be said that the performance of the diaphragm has a great impact on the safety of the battery cell. has a very large impact. At prese...

AI Technical Summary

Problems solved by technology

Because of the complexity of the winding structure, when the winding core is heated, the heat accumulation in each part of the winding core is inconsistent, and the heating of the inner diaphragm is also inconsistent. Therefore, the thermal shrinkage of the diaphragm in this state is different from that of There will be differences in the natural stretch state of the diaphragm

However, the current thermodynamic testing methods for diaphragms usually only test the thermal shrinkage of the diaphragm under natural stretching conditions. of

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