# US 2024/0201283 A1 · Method of testing lithium-ion secondary battery, and method of producing lithium-ion secondary battery using the same

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- Number: US 2024/0201283 A1
- Document ID: US20240201283A1
- Status: Published application
- Kind: A1
- Application number: 18/463,722
- Filed: 2023-09-08
- Published: 2024-06-20
- Earliest claimed: 2022-12-20
- Assignees: Toyota Jidosha Kabushiki Kaisha
- Applicants: Toyota Jidosha Kabushiki Kaisha
- Inventors: Ruri HARA; Yamato SAITO; Toshiya ARAKAWA
- Web page: https://patentgrep.com/patent/US20240201283A1

## CPC

- G01R 31/52: Testing for short-circuits, leakage current or ground faults
- G01R 19/16542: {for batteries (charge condition monitoring in G01R31/36)}
- G01R 31/36: Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R 31/382: Arrangements for monitoring battery or accumulator variables, e.g. SoC
- G01R 31/3842: combining voltage and current measurements
- G01R 31/386: {using test-loads}
- G01R 31/3865: {related to manufacture, e.g. testing after manufacture}
- H01M 10/48: Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte (constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569)
- Y02E 60/10: Energy storage using batteries
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

Provide is a method of testing a lithium-ion secondary battery which enables whether the battery is good or bad to be determined with high accuracy in a short time even when lithium iron phosphate is used as a cathode active material. The method of testing the battery includes: adjusting a charging rate of the battery to be in a plateau region and to be in the range from 25 to 35% or 70 to 90%; setting voltage of a test power supply to a voltage equal to or higher than voltage of the battery; building a circuit by connecting the battery and the test power supply; measuring a leakage current that flows through the circuit until the increase of the leakage current converges; and determining whether the battery is good or bad based on the leakage current after the leakage current has converged.

## Claims

### Claim 1

A method of testing a lithium-ion secondary battery, the battery comprising a cathode containing lithium iron phosphate as a cathode active material, an anode containing a carbon material as an anode active material, and an electrolyte layer arranged between the cathode and the anode, the method comprising:
adjusting a charging rate of the lithium-ion secondary battery to be in a plateau region and to be in the range from 25 to 35% or 70 to 90%;
setting voltage of a test power supply to a voltage equal to or higher than voltage of the lithium-ion secondary battery;
building a circuit by connecting the lithium-ion secondary battery and the test power supply;
measuring a leakage current that flows through the circuit until the leakage current converges; and
determining whether the lithium-ion secondary battery is good or bad based on the leakage current after the leakage current has converged.

### Claim 2 (depends on 1)

The method according to claim 1, wherein in said measuring a leakage current, the voltage of the test power supply is raised over time.

### Claim 3 (depends on 1)

The method according to claim 1, wherein
in said adjusting a charging rate, the charging rate of the lithium-ion secondary battery is adjusted, so that dV/dT is −0.05 mV/° C. to 0.05 mV/° C. where V is the voltage of the lithium-ion secondary battery, and T is temperature of the lithium-ion secondary battery.

### Claim 4 (depends on 1)

A method of producing a lithium-ion secondary battery, the method comprising:
making the lithium-ion secondary battery comprising a cathode containing lithium iron phosphate as a cathode active material, an anode containing a carbon material as an anode active material, and an electrolyte layer arranged between the cathode and the anode; and
performing the testing method according to claim 1.