Nonaqueous Battery Aging and Forced Discharge for Voltage Stability
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Solution Overview
Problem
The existing methods for producing nonaqueous secondary batteries face challenges in shortening the voltage instability period during self-discharge tests, which prolongs the production time and affects productivity, work efficiency, and costs, especially in batteries requiring high output power in low SOC regions like plug-in hybrid vehicles.
Innovation Solution
The method involves preparing an electrode body with a larger negative electrode active material layer surface area, adjusting the residual capacity percentage to 11.5% to 14%, and performing forced discharging at elevated temperatures to alleviate electric potential irregularities in the negative electrode active material layer, thereby reducing the voltage instability period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery assembly is kept in a high SOC state for aging, then the self-discharge test can be conducted, but the voltage instability period becomes longer
Solution Approach 1:
The patent applies preliminary action by performing forced discharging before the self-discharge test to pre-stabilize the voltage. This preliminary step removes the voltage instability that would otherwise persist for days, allowing the test to begin with a stable baseline and significantly reducing the waiting period.
Solution Approach 2:
The patent changes the parameter of SOC (state of charge) dynamically during the process. It involves charging to high SOC for aging, then forced discharging to a specific SOC range (10-30%), and finally conducting the self-discharge test. This parameter manipulation optimizes both test accuracy and time efficiency.
2Reliability
If the negative electrode active material layer surface area is increased, then charge carrier precipitation is suppressed, but electric potential irregularity occurs in the layer
Solution Approach 1:
The patent applies local quality by addressing different regions of the negative electrode active material layer differently. The forced discharging process specifically targets the non-opposite portion where charge carriers accumulate, creating localized electric potential changes that restore overall uniformity without affecting the opposite portion's function.
Solution Approach 2:
The patent uses forced discharging to rapidly skip through the slow natural diffusion process of charge carriers. Instead of waiting days for charge carriers to naturally redistribute, the forced discharging quickly equalizes the electric potential across the layer, accelerating the stabilization process.
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
This approach effectively shortens the self-discharge test period to nearly zero, enhancing productivity and work efficiency while maintaining test accuracy, and ensures the production of highly reliable batteries.
Implementation Method 1
the concentration relaxation of the charge carriers occurs in the negative electrode active material layer during the aging performed thereafter. Then, the charge carriers gradually move toward the non-opposite portion having a relatively high electric potential
Implementation Method 2
performing forced discharging at elevated temperatures to alleviate electric potential irregularities in the negative electrode active material layer
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
A method of producing a nonaqueous secondary battery includes: preparing an electrode body (S10); constructing a battery assembly with the electrode body and a nonaqueous electrolyte (S20); initially charging the battery assembly (S30); aging the battery assembly at 40 °C or higher (S40); adjusting an SOC of the battery assembly (S60), wherein, the adjusting the SOC is performed such that a residual capacity percentage of the battery assembly is 11.5 % or more and 14 % or less; self-discharging the battery assembly and measuring a voltage drop amount (S70); and determining a quality of the battery assembly based on the voltage drop amount (S80).