Dynamic Current Charging for Non-Aqueous Electrolyte Battery Cycle Life
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Solution Overview
Problem
Conventional constant-current and constant-voltage charging methods for non-aqueous electrolyte secondary batteries do not have a theoretical basis for improving cycle characteristics, and may cause charge polarization, leading to deterioration in battery performance.
Innovation Solution
A charging method that detects the state of charge and adjusts the charging current accordingly, switching between constant-current and constant-voltage modes based on predetermined values, using a charger with a voltage detection unit, state-of-charge detection, and a control unit to manage the charging process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If constant-current and constant-voltage charging is performed with large charge current at the beginning to shorten charging time, then charging speed is improved, but charge polarization varies greatly and cycle characteristics deteriorate
Solution Approach 1:
The charging method dynamically adjusts the charge current based on the battery's state of charge. Instead of using a fixed large current, the system monitors the battery voltage and automatically reduces the charge current when the voltage reaches a predetermined threshold, then increases it again when voltage drops. This dynamic adjustment optimizes charging speed while preventing excessive charge polarization that would deteriorate cycle characteristics.
Solution Approach 2:
The charging system incorporates feedback control by continuously monitoring the battery voltage during charging. When the voltage reaches the predetermined threshold, the system provides feedback to reduce the charge current. This feedback mechanism ensures that charging is performed at large current only when safe, thereby shortening charging time without causing harmful variations in charge polarization that would damage the battery's cycle life.
2Reliability
If charge current is reduced stepwise after reaching charge cutoff voltage to maintain battery voltage, then battery safety is improved, but charging time increases
Solution Approach 1:
The charging method employs periodic action by alternating between large current charging and reduced current maintenance phases. When the battery voltage reaches the predetermined threshold, the charge current is reduced to maintain safety. When the voltage subsequently drops below the threshold, the current is increased again. This periodic cycling between high and low current states ensures battery safety is maintained while minimizing overall charging time compared to continuously using reduced current.
Data Source
AI summary
In a charging method for a non-aqueous electrolyte secondary battery which includes a positive electrode including a lithium-containing composite oxide as an active material, a negative electrode including an alloy-formable negative electrode active material, and a non-aqueous electrolyte, a voltage of the secondary battery is detected. When the detected value is smaller than a predetermined voltage x, charging is performed at a comparatively small current value B. When the detected value is equal to or greater than the predetermined voltage x and smaller than a predetermined voltage z, charging is performed at a comparatively great current value A. When the detected value is equal to or greater than the predetermined voltage z and smaller than a predetermined voltage y, charging is performed at a comparatively small current value C. When the detected value is greater than the predetermined voltage y, constant-voltage charging is performed or charging is terminated. Here, x<z<y.