EP-4741797-A1 - POLE PIECE TESTING METHOD

Abstract

The present application discloses a pole piece testing method. The method comprises: performing pre-processing of pole pieces to obtain a plurality of test samples; performing rolling on a test sample to obtain the compaction density of the test sample; obtaining the specific surface area of the test sample; calculating the specific surface area of an electrode active material; establishing, on the basis of the specific surface area and compaction density of the electrode active material, a compaction density-specific surface area curve; and obtaining, on the basis of an inflection point of the compaction density-specific surface area curve, a maximum available compaction density of the pole piece.

Inventors

• JIAN, Jiejie
• XU, CHANGSHENG
• CHENG, Xiaolin
• LIU, JING
• SHENG, Jie
• YANG, HONGXIN

Assignees

• SVOLT Energy Technology Co., Ltd.

Dates

Publication Date

20260513

Application Date

20240515

Claims (10)

1. A method for testing an electrode sheet, characterized by comprising following steps: preprocessing the electrode sheet to obtain several test samples; rolling the test samples to obtain compaction densities of the test samples; obtaining specific surface areas of the test samples; calculating a specific surface area S B of an electrode active material according to Formula (1): S B = S A * a + b / b where in Formula (1), S A is a specific surface area of the test sample, a is an areal density of a current collector of the electrode sheet, and b is an areal density of the electrode active material of the electrode sheet; establishing a compaction density-specific surface area curve according to specific surface areas of the electrode active material and the compaction densities; and obtaining a maximum usable compaction density of the electrode sheet according to an inflection point of the compaction density-specific surface area curve.
2. The method for testing the electrode sheet as claimed in claim 1, wherein the step of obtaining the compaction densities of the test samples comprises: measuring thickness values of the rolled test samples; and calculating a compaction density ρ of the test sample according to Formula (2): ρ = a + b / h where in Formula (2), h is the thickness of the test sample.
3. The method for testing the electrode sheet as claimed in claim 1, wherein a rolling load is in a range of 3 tons to 50 tons.
4. The method for testing the electrode sheet as claimed in claim 1, wherein the areal density a of the current collector of the electrode sheet satisfies: 3 mg/cm 2 ≤ a ≤ 6 mg/cm 2 .
5. The method for testing the electrode sheet as claimed in claim 1 or 4, wherein the areal density b of the electrode active material of the electrode sheet satisfies: 10 mg/cm 2 ≤ b ≤ 50 mg/cm 2 .
6. The method for testing the electrode sheet as claimed in claim 1, wherein the step of preprocessing the electrode sheet comprises: trimming off tabs and wrinkled edges of the electrode sheet; and cutting the electrode sheet into 5 to 15 test samples of approximately same size.
7. The method for testing the electrode sheet as claimed in claim 1, wherein the step of establishing the compaction density-specific surface area curve according to the specific surface areas of the electrode active material and the compaction densities comprises: setting an X-axis according to compaction density data of the test samples; setting a Y-axis according to specific surface area data of the electrode active material; and generating a Cartesian coordinate system, and generating the compaction density-specific surface area curve in the Cartesian coordinate system according to a correspondence between a compaction density value of the test sample and a specific surface area value of the electrode active material.
8. The method for testing the electrode sheet as claimed in claim 7, wherein the step of obtaining the maximum usable compaction density of the electrode sheet according to the inflection point of the compaction density-specific surface area curve comprises: identifying the inflection point of the compaction density-specific surface area curve; drawing tangent lines to curves on two sides of the inflection point respectively, so that the two tangent lines intersect to form an intersection point; and identifying an X-axis coordinate of the intersection point in the Cartesian coordinate system, so as to determine the maximum usable compaction density of the electrode sheet.
9. The method for testing the electrode sheet as claimed in claim 1, wherein a method for testing the specific surface area of the test sample is a nitrogen adsorption continuous flow method or a vacuum static volumetric method.
10. The method for testing the electrode sheet as claimed in claim 1, wherein in a case where the electrode sheet is a positive electrode sheet, the current collector of the electrode sheet is aluminum foil, and the electrode active material of the electrode sheet is at least one selected from the group consisting of LiMnO 2 , LiMn 2 O 4 , LiCoO 2 , LiFePO 4 , LiNi x Mn 1-x O 2 and LiNi x Co y Mn 1-x-y O 2 , where 0 < x < 1 and 0 < y < 1; and in a case where the electrode sheet is a negative electrode sheet, the current collector of the electrode sheet is copper foil, and the electrode active material of the electrode sheet is any one selected from the group consisting of graphite, soft carbon and hard carbon.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present application claims the priority to the Chinese Patent Application No. 202310810909.2 filed with the China National Intellectual Property Administration on July 3, 2023, and entitled "POLE PIECE TESTING METHOD", the contents of which are incorporated herein by reference in entirety. TECHNICAL FIELD The embodiments of the present application relate to, but are not limited to, a method for testing an electrode sheet (pole piece). BACKGROUND ART Positive and negative electrode sheets are key materials in lithium-ion batteries. During the manufacturing process of lithium batteries, the compaction density of the electrode sheet has a significant impact on the electrical performance. The compaction density is closely related to the specific capacity, efficiency, and internal resistance of the electrode sheet, as well as the cycle performance of the battery. A proper compaction density can increase the discharge capacity of the battery, reduce the internal resistance, decrease the polarization loss, and extend the cycle life of the battery. A proper compaction density of the electrode sheet can increase the discharge capacity of the battery, reduce the internal resistance, decrease the polarization loss, extend the cycle life of the battery, thereby improving the utilization rate of the lithium-ion battery. Excessively high or low compaction is detrimental to the battery performance. Therefore, it is very important to find the optimal compaction density for battery design. SUMMARY The present application provides a method for testing an electrode sheet. The method includes following steps: preprocessing the electrode sheets to obtain several test samples;rolling the test samples to obtain compaction densities of the test samples;obtaining specific surface areas of the test samples;calculating a specific surface area SB of an electrode active material according to Formula (1): SB=SA*a+b/bwhere in Formula (1), SA is a specific surface area of a test sample, a is an areal density of a current collector of the electrode sheet, and b is an areal density of the electrode active material of the electrode sheet;establishing a compaction density-specific surface area curve according to specific surface areas of the electrode active material and the compaction densities; andobtaining a maximum usable compaction density of the electrode sheet according to an inflection point of the compaction density-specific surface area curve. In some embodiments, the step of obtaining the compaction densities of the test samples includes: measuring thickness values of the rolled test samples; andcalculating a compaction density ρ of the test sample according to Formula (2): ρ=a+b/hwhere in Formula (2), h is a thickness of the test sample. In some embodiments, a rolling load is in a range of 3 tons to 50 tons. In some embodiments, the areal density a of the current collector of the electrode sheet satisfies: 3 mg/cm2 ≤ a ≤ 6 mg/cm2. The areal density b of the electrode active material of the electrode sheet satisfies: 10 mg/cm2 ≤ b ≤ 50 mg/cm2. In some embodiments, the step of preprocessing the electrode sheet includes: trimming off tabs and wrinkled edges of the electrode sheet; andcutting the electrode sheet into 5 to 15 test samples of approximately same size. In some embodiments, the step of establishing the compaction density-specific surface area curve according to the specific surface areas of the electrode active material and the compaction densities includes: setting an X-axis according to compaction density data of the test samples;setting a Y-axis according to specific surface area data of the electrode active material; andgenerating a Cartesian coordinate system, and generating the compaction density-specific surface area curve in the Cartesian coordinate system according to a correspondence between a compaction density value of the test sample and a specific surface area value of the electrode active material. In some embodiments, the step of obtaining the maximum usable compaction density of the electrode sheet according to the inflection point of the compaction density-specific surface area curve includes: identifying the inflection point of the compaction density-specific surface area curve;drawing tangent lines to curves respectively on two sides of the inflection point respectively, so that the two tangent lines intersect to form an intersection point; andidentifying an X-axis coordinate of the intersection point in the Cartesian coordinate system, so as to determine the maximum usable compaction density of the electrode sheet. In some embodiments, a method for testing the specific surface area of the test sample is a nitrogen adsorption continuous flow method or a vacuum static volumetric method. In some embodiments, the electrode sheet is a positive electrode sheet, the current collector of the electrode sheet is aluminum foil, and the electrode active material of the el