Secondary Battery Self-Discharge Testing with Li Diffusion Settling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for self-discharge testing in secondary batteries are inaccurate due to variations in battery voltage caused by Li diffusion and SEI coating formation, which require a waiting period of several days to weeks, leading to delayed and unreliable detection of short-circuits.
Innovation Solution
A self-discharge test method that adjusts the battery voltage to a first voltage within 17 hours or less to minimize voltage variations from Li diffusion, allowing immediate and accurate testing for short-circuits by measuring voltage changes within a short period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the battery is left to stand for a long period after voltage adjustment to allow Li diffusion to settle, then the measurement precision of self-discharge test is improved, but the productivity of battery manufacturing is deteriorated due to extended testing time
Solution Approach 1:
The patent changes the voltage adjustment parameters (target voltage value and adjustment method) to control the Li diffusion process. By adjusting the battery to a specific voltage within 17 hours, the Li concentration gap between opposing and non-opposing portions settles without requiring extended waiting periods, thus maintaining measurement precision while improving productivity
Solution Approach 2:
The patent performs preliminary voltage adjustment to a specific value before conducting the self-discharge test. This preliminary action of adjusting voltage within 17 hours ensures that Li diffusion-related voltage variations are minimized in advance, allowing immediate testing without long waiting periods and thereby resolving the contradiction between measurement precision and productivity
2Ease of operation
If the battery voltage is adjusted by CCCV charging to target voltage, then the ease of operation is improved, but the measurement precision is deteriorated due to residual battery current causing voltage drop
Solution Approach 1:
The patent performs a preliminary voltage adjustment step after CCCV charging to eliminate the effect of residual battery current. By measuring the open-circuit voltage and comparing it with the target voltage, and adjusting if necessary, the system ensures accurate voltage measurement before self-discharge testing, thus resolving the contradiction between ease of operation and measurement precision
Solution Approach 2:
The patent implements a feedback mechanism where the battery voltage is measured after CCCV charging, compared with the target voltage, and adjusted if the difference exceeds a predetermined threshold. This feedback loop ensures that the voltage measurement is accurate and free from residual current effects, while maintaining the simplicity of CCCV charging method
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables early and precise detection of short-circuits by minimizing voltage variations, ensuring accurate self-discharge testing and efficient battery manufacturing by excluding defective batteries.
Implementation Method 1
diffusion of charge carrier atoms that are diffused to equalize a concentration gap between an opposing-portion concentration and a non-opposing-portion concentration
Data Source
AI summary
A method of self-discharge test for a battery including an electrode body provided with a positive electrode plate including a positive active material layer and a negative electrode plate including a negative active material layer. The method includes a process of voltage adjusting to adjust a battery voltage to a first battery voltage and a process of self-discharge testing to keep the battery in a terminal open state for a predetermined term and to inspect a state of self-discharge of the battery from variations in the battery voltage occurred during the predetermined term. The voltage adjusting is to adjust the battery voltage to the first battery voltage having magnitude, for which a variation settled time of settling a variation amount of the battery voltage varied by Li diffusion to lessen a concentration gap of an opposing-portion concentration and a non-opposing portion concentration, is set as 17 hours or less.