Battery Cell Screening for Nonuniform Degradation Elimination
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Solution Overview
Problem
Existing lithium-ion battery degradation technologies fail to adequately address degradation due to nonuniformity of potentials in the electrode plane, leading to inaccurate degradation assessment and reduced battery life when batteries are reused.
Innovation Solution
A battery processing system and method that includes a control device to monitor degradation indicators, executing first and second elimination processes to address nonuniformity of lithium ion concentration and potential distributions, respectively, through controlled charging and discharging to mitigate and eliminate these issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If elimination processing is executed only when the state of charge is out of the allowable range, then the battery pack durability is improved, but the productivity is worsened due to increased rework and time consumption
Solution Approach 1:
The control device executes elimination processing in advance based on degradation indicator values before final assembly, identifying and eliminating degraded cells proactively. This preliminary action prevents later failures and rework, improving battery pack durability while maintaining assembly throughput by filtering out problematic cells before they cause issues during operation or final testing.
2Measurement precision
If multiple types of degradation are monitored separately, then the measurement precision is improved, but the device complexity is worsened
Solution Approach 1:
The control device combines multiple degradation monitoring functions into a single integrated system. It simultaneously monitors voltage deviation, temperature deviation, and charge-discharge rate, calculating composite degradation indicator values that reflect multiple degradation modes. This merging approach maintains high measurement precision for detecting various degradation types while reducing device complexity by consolidating monitoring functions into one control device rather than separate systems for each degradation type.
Data Source
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AI summary
A control device executes processing including: executing first elimination processing (S106) when there is a history of addition of degradation indicator values ΣD (YES in S102) and also when degradation indicator value ΣD is larger than a first threshold value TH1 (YES in S 104); measuring a characteristic value of a cell (S 108); executing second elimination processing (S 110); determining reusability (S 1 14) when the characteristic value is within an allowable range (YES in S 1 12); determining unreusability (S 116) when the characteristic value is out of the allowable range (NO in S 112); and executing the second elimination processing (S 118) when degradation indicator value ΣD is first threshold value TH1 or less (NO in S 104).