Lithium-Ion Battery Charging Control via Negative-Electrode Potential Evaluation
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Solution Overview
Problem
Conventional lithium-ion battery charging methods, such as constant-current and constant-voltage charging, lead to rapid increases in positive-electrode potential, causing deterioration, gas generation, and lithium deposition issues, especially when using cathode active materials with an Olivine-type crystal structure.
Innovation Solution
A charging control method and apparatus that evaluates the negative-electrode potential change and adjusts the target voltage downward based on this evaluation, using methods like difference value, shift quantity, or differentiation coefficient evaluation to prevent excessive positive-electrode potential rise during charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If constant-current and constant-voltage charging method is used to quickly raise positive-electrode potential at final stage of charging, then charging speed is improved, but positive-electrode potential rises excessively causing battery deterioration, gas generation and lithium deposition
Solution Approach 1:
The patent implements feedback control by continuously monitoring the positive-electrode potential during charging and dynamically adjusting the charging current based on the measured potential. When the potential approaches a predetermined threshold, the charging current is automatically reduced or stopped, preventing excessive potential rise and associated damage while maintaining efficient charging during normal operation
Solution Approach 2:
The patent transitions from static charging methods (fixed constant-current and constant-voltage stages) to a dynamic charging approach where the charging parameters are continuously adjusted based on real-time positive-electrode potential measurements. This allows the charging process to adapt to the battery's actual state, optimizing both speed and safety
2Productivity
If positive-electrode potential rises quickly at final stage of charging, then charging efficiency is improved, but electrolyte solution generates decomposition gas and battery deteriorates
Solution Approach 1:
The system uses feedback control to monitor positive-electrode potential and adjust charging current accordingly. When potential reaches levels that risk electrolyte decomposition, the current is automatically reduced, preventing gas generation while maintaining high charging efficiency during the majority of the charging process
3Loss of time
If positive-electrode potential rises quickly at final stage of charging, then charging time is reduced, but lithium deposition occurs on the electrode
Solution Approach 1:
The patent employs feedback control to detect when positive-electrode potential approaches levels that cause lithium deposition. Upon detection, the charging current is automatically reduced or terminated, preventing deposition while minimizing additional charging time through efficient early-stage charging
Data Source
AI summary
A lithium-ion battery includes a cathode active material of the Olivine-type crystal structure. The lithium-ion battery is charged under control of a charging control apparatus, which performs a charging process for charging up to a target voltage according to a constant-current and constant-voltage charging method, a negative-electrode potential evaluation process for evaluating a potential change quantity at the negative-electrode, and a voltage setting process for setting the target voltage to a lower voltage based on the potential change quantity of the negative-electrode evaluated by the negative-electrode potential evaluation process. The charging voltage is changed from the target voltage to the set voltage even when the negative-electrode potential changes with an increase in the number of charging and aging deterioration. Thus a positive-electrode potential is suppressed from rising because of less susceptibility to the increase in number of charging and aging deterioration.