Secondary Battery Self-Discharge Inspection via Voltage Difference Accumulation
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Solution Overview
Problem
The existing self-discharge inspection methods for secondary batteries are inefficient due to unstable voltage periods, requiring longer times and varying inspection durations based on production lots and aging conditions, which affects productivity and accuracy.
Innovation Solution
An inspection method that includes a charging step, aging step, pre-inspection discharge step, voltage adjustment step, and self-discharge inspection step, where the discharge condition is set to achieve a voltage difference accumulation value within a predetermined range, allowing for precise control of potential unevenness in the negative-electrode active material layer, thereby shortening the unstable voltage period and improving inspection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the voltage of the secondary battery is allowed to stabilize naturally after SOC adjustment, then measurement accuracy is improved, but inspection time is excessively prolonged
Solution Approach 1:
The patent applies preliminary action by performing a pre-inspection discharge step before the actual self-discharge inspection. This preliminary discharge to a specific SOC range (10-30%) prepares the battery in advance, causing charge carriers to move from the non-facing portion to the facing portion of the negative electrode, thereby eliminating potential unevenness before the inspection begins. This allows the inspection to start immediately without waiting for natural voltage stabilization.
Solution Approach 2:
The patent changes the SOC parameter dynamically during the inspection process. By discharging the battery to a specific SOC range (10-30%) before inspection and maintaining it there, the patent optimizes the charge carrier distribution in the negative electrode. This parameter change ensures uniform potential distribution and eliminates the unstable voltage period, enabling both fast and accurate inspection.
2Productivity
If the inspection is performed immediately after charging without waiting for voltage stabilization, then productivity is improved, but measurement accuracy deteriorates due to unstable voltage
Solution Approach 1:
The pre-inspection discharge step serves as a preliminary action that quickly prepares the battery for accurate measurement. By discharging to SOC 10-30% before the inspection, the patent creates optimal conditions for voltage stability without requiring long waiting periods. This preliminary preparation enables both high productivity and high measurement accuracy.
Solution Approach 2:
The patent skips the traditional long waiting period for voltage stabilization by rushing through a quick discharge to the optimal SOC range (10-30%). This rapid preparation step eliminates the unstable voltage period caused by charge carrier unevenness, allowing the inspection to proceed immediately with high accuracy and efficiency.
3Ease of operation
If the negative-electrode active material layer has a larger surface area than the positive-electrode active material layer, then charge carrier receiving characteristic is improved, but voltage instability occurs during inspection
Solution Approach 1:
The patent changes the SOC parameter to a specific range (10-30%) that optimizes the charge carrier distribution in the negative electrode. At this SOC range, the charge carriers are uniformly distributed between the facing and non-facing portions, eliminating potential unevenness while maintaining the large surface area advantage for charge carrier reception. This parameter optimization resolves the contradiction between ease of operation and voltage stability.
Data Source
AI summary
An inspection method of a secondary battery includes a charging step, an aging step, a pre-inspection discharge step, a voltage adjustment step, a self-discharge inspection step, and a deficiency determination step. A discharge condition in the pre-inspection discharge step is determined so that a voltage difference accumulation value Vs satisfies a predetermined range. The voltage difference accumulation value Vs is calculated by accumulating a value obtained by subtracting an output voltage from a predetermined voltage over a duration from start of the pre-inspection discharge step to end thereof.