CN-117169739-B - Evaluation method for internal resistance performance of lithium ion battery

CN117169739BCN 117169739 BCN117169739 BCN 117169739BCN-117169739-B

Abstract

The invention provides an evaluation method for the internal resistance performance of a lithium ion battery. S1, performing charge-discharge cycle test on a lithium ion battery to be tested, wherein the charge process is constant-current constant-voltage charge, the discharge process is constant-current discharge, and the internal resistance performance of the button lithium ion battery to be tested is tested by using the increase rate of the constant-voltage charge capacity ratio in the xth cycle process as B x (B x ＝(A x -A1)/A 1 *100％,A x ＝C 2x /C 1x x 100 percent. The invention characterizes the internal resistance increasing rate of the material by the changing rate of the constant voltage charging capacity ratio in the charging process of the lithium ion battery, can continuously monitor the internal resistance change in the battery circulation process, can accurately judge the internal resistance increasing rate of different materials by the evaluation result, and has simple and convenient method. The method provided by the invention has the advantages of short period, low cost, simplicity and convenience, and is suitable for evaluating and screening various materials in the material research and development stage.

Inventors

LUO DIDI
ZHOU HONGBAO
LI YANWEI
LI WENQIANG
ZHANG HU
ZHOU QINGBAO
ZHU WEIQUAN

Assignees

天津国安盟固利新材料科技股份有限公司

Dates

Publication Date: 20260512
Application Date: 20220526

Claims (14)

1. The method for evaluating the internal resistance performance of the lithium ion battery is characterized by comprising the following steps of: S1, carrying out charge-discharge cycle test on a lithium ion battery to be tested, wherein the charge process is constant-current constant-voltage charge, the discharge process is constant-current discharge, the total charge capacity in the xth charge-discharge cycle process is C 1x , the constant-voltage charge capacity in the xth charge-discharge cycle process is C 2x , and the cycle number is at least 30; S2, recording that the capacity ratio of constant voltage charge in the x-th charge-discharge cycle is A x ,A x =C 2x /C 1x multiplied by 100 percent; and S3, taking the first charge and discharge process as a first cycle, taking A 1 as a comparison standard, wherein the increase rate of the constant voltage charge capacity ratio in the xth cycle process is B x ,B x =（A x -A 1 ）/A 1 multiplied by 100 percent, and finally, B x is used for evaluating the internal resistance performance of the button type lithium ion battery to be tested.
2. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 1, wherein the temperature in the charge-discharge cycle test is-20-60 ℃.
3. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 1 or 2, wherein the constant-current constant-voltage charging process comprises: Constant current charging is carried out to cut-off voltage, and then constant voltage charging is carried out at the cut-off voltage.
4. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 3, wherein the cutoff voltage in the constant current charging process is 4.3-4.6 v.
5. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 3, wherein the charging current in the constant current charging process is 0.1-2 ℃.
6. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 1, wherein the off-current in the constant voltage charging process is 0.005-0.1 ℃.
7. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 1, wherein the discharge current in the constant current discharge process is 0.1-2 ℃.
8. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 1, wherein the discharge cut-off voltage in the constant current discharge process is 2.5-3 v.
9. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 1, wherein the standing is performed after each constant-current constant-voltage charge.
10. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 9, wherein the standing time is not less than 60s.
11. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 1, wherein after each constant current discharge, standing is performed.
12. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 11, wherein the standing time is not less than 60s.
13. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 1, wherein the lithium ion battery is a lithium ion half-cell.
14. The method for evaluating the internal resistance performance of a lithium ion battery according to claim 1, characterized in that the evaluating method comprises the steps of: S1, carrying out charge-discharge cycle test on a lithium ion half battery to be tested at-20-60 ℃, wherein the charge process is constant-current constant-voltage charge, the discharge process is constant-current discharge, firstly, carrying out constant-current charge with a charge current of 0.1-2 ℃ until the cutoff voltage is 4.3-4.6V, then, carrying out constant-voltage charge with the cutoff voltage until the cutoff current is 0.005-0.1 ℃, standing for more than or equal to 60 seconds, then, carrying out constant-current discharge with a discharge current of 0.1-2 ℃ until the cutoff voltage is 2.5-3V, standing for more than or equal to 60 seconds, and carrying out the next charge-discharge cycle process; The total charge capacity in the x-th charge-discharge cycle is C 1x , the constant voltage charge capacity in the x-th charge-discharge cycle is C 2x , and the cycle times are more than or equal to 30 times; S2, recording that the capacity ratio of constant voltage charge in the x-th charge-discharge cycle is A x ,A x =C 2x /C 1x multiplied by 100 percent; And S3, taking the first charge and discharge process as a first cycle, taking A 1 as a comparison standard, wherein the increase rate of the constant voltage charge capacity ratio in the xth cycle process is B x ,B x =（A x -A1）/A 1 multiplied by 100 percent, and finally, B x is used for evaluating the internal resistance performance of the button type lithium ion battery to be tested.

Description

Evaluation method for internal resistance performance of lithium ion battery Technical Field The invention belongs to the technical field of lithium ion batteries, and relates to an evaluation method for the internal resistance performance of a lithium ion battery. Background The lithium ion battery has the advantages of small volume, high energy density, long cycle life, small self-discharge rate, no memory effect and the like, and is widely applied to the fields of portable electronic equipment, electric automobiles, energy storage systems and the like. Along with the continuous improvement of the requirements of the new energy automobile on the endurance mileage and the backslide of the national patch to the new energy automobile, the energy density of the power battery is improved and the cost is reduced. The positive electrode material is the most important component of the lithium ion battery, and the energy density and the cost of the battery are determined to a great extent, so that the positive electrode material is developed towards the cobalt reduction and the voltage increase. The internal resistance is a key index for evaluating the lithium ion battery, and directly affects the energy density, the power performance, the cycle performance and the safety characteristic of the lithium ion battery, particularly for a low cobalt material, the cobalt content can affect the conductivity of the material, when the cobalt content is reduced, the internal resistance of the material is increased, the internal resistance of the material in the cycle process is increased relatively quickly, and the battery performance is seriously affected, so that the internal resistance and the characteristic of the increase rate of the internal resistance in the cycle process are very important in the development process of the low cobalt material. In the current stage, the general test method of the internal resistance increasing rate in the circulation process comprises (1) stopping the test of the battery in the circulation process, taking down the battery, wherein the on-line measurement of the internal resistance has larger common error and is influenced by the temperature of the battery, the measurement pulse current duration and the pulse current size, the on-line estimation condition cannot reach the same condition as the off-line test method of the internal resistance of the new battery, so that the on-line estimation internal resistance cannot be compared with the internal resistance value of the new battery, the increasing rate of the internal resistance cannot be accurately measured, (2) adopting a specific device and condition to carry out DCR test on the battery, (3) continuously carrying out the charge-discharge circulation test on the battery, and carrying out the reciprocating circulation to obtain the internal resistance increasing rate of the battery, the method is complex, CN103018566a discloses a method for testing direct current internal resistance of a lithium ion battery, which comprises the first step of placing the lithium ion battery at room temperature, the second step of continuously discharging the battery with a first preset discharge current I1 in a first preset discharge time interval and measuring a first discharge cut-off voltage U1 of the battery in real time after the discharge is finished, the third step of continuously discharging the battery with a second preset discharge current I2 in a second preset discharge time interval and measuring a second discharge cut-off voltage U2 of the battery in real time after the discharge is finished, and the fourth step of calculating the direct current internal resistance of the battery in real time according to a preset direct current internal resistance calculation formula, wherein the direct current internal resistance of the battery is obtained through on-line direct measurement, the error is large, and therefore the internal resistance growth rate is difficult to evaluate accurately. CN111525202A discloses a monitoring method, a system, equipment and a medium of DCR in a lithium ion battery cycle, wherein the monitoring method comprises the steps of acquiring data in a lithium ion battery charge-discharge cycle, including time, and voltage values, temperature and charge-discharge current values of the lithium ion battery at corresponding time in the charge-discharge process, extracting test data of a plurality of charge-discharge cycles, including voltage values, current values in a period of time when charging starts and voltage values and current values in a period of time before discharging starts, and obtaining a discharge DCR and a charge DCR according to a DCR calculation formula. The technical scheme of the patent application can better know the variation trend of the charge DCR and the discharge DCR of the lithium ion battery in the circulation process, identify the risk of abnormal performance of the battery cell in advance, and sav