Lithium Ion Battery Charging Control via Intermittent Suspension
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Solution Overview
Problem
Lithium ion secondary batteries face issues with lithium deposition on the negative electrode during charging, leading to reduced battery capacity, internal resistance increase, gas generation, and potential short circuits, which are exacerbated by high electrode density.
Innovation Solution
A control apparatus that suspends charging of lithium ion secondary batteries for a predetermined time, calculated using the weight per unit area and density of the negative electrode, to disperse lithium ions and prevent deposition, thereby maintaining battery performance without reducing electrode density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrode density is reduced to prevent lithium deposition, then lithium deposition is suppressed, but the energy density of the battery decreases
Solution Approach 1:
The patent applies periodic action by implementing intermittent charging with suspension periods. The charging process is divided into charging periods and suspension periods, where charging is paused for a predetermined time (calculated using the formula t≥−A+B×x+C×y) to allow lithium ion distribution to equalize. This periodic interruption prevents continuous lithium deposition on the negative electrode while maintaining high electrode density for energy density, thus resolving the contradiction between reliability and quantity of substance.
2Productivity
If charging is performed continuously at high current, then charging speed is improved, but lithium deposition occurs on the negative electrode
Solution Approach 1:
The patent implements periodic action by alternating between charging periods and suspension periods. During charging periods, high current is applied to maintain fast charging speed. During suspension periods, charging is interrupted for a predetermined time to allow lithium ions to redistribute uniformly throughout the electrode. This periodic pattern enables high charging speed while preventing lithium deposition, resolving the contradiction between productivity and reliability.
Solution Approach 2:
The patent applies preliminary action by performing suspension before resuming charging. The suspension period is calculated in advance using the formula t≥−A+B×x+C×y, where x is the weight per unit area and y is the density of the negative electrode. This preliminary suspension ensures lithium ion distribution is equalized before the next charging phase begins, preventing deposition that would occur with continuous high-current charging, thus maintaining both high charging speed and reliability.
3Productivity
If the charging voltage is increased to improve charging efficiency, then charging efficiency is improved, but lithium deposition is exacerbated
Solution Approach 1:
The patent resolves the contradiction between charging efficiency and lithium deposition by implementing periodic suspension during high-voltage charging. The charging process alternates between charging periods (where high voltage improves charging efficiency) and suspension periods (where charging is paused to allow lithium ion redistribution). The suspension duration is calculated using the formula t≥−A+B×x+C×y, ensuring that lithium deposition is prevented even when high charging voltages are used, thus maintaining both high productivity and reliability.
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
Prevents lithium deposition on the negative electrode, maintaining battery capacity and reducing internal resistance, while avoiding the need for lower electrode density which would decrease energy density.
Implementation Method 1
suspend the charging of the lithium ion secondary battery, until a predetermined time t elapses, after the charging... to disperse lithium ions and prevent deposition
Data Source
AI summary
A control apparatus (2000) includes a control unit (2020). The control unit (2020) causes a charging apparatus (20) to perform charging of a lithium ion secondary battery (10), by controlling the charging apparatus (20). First, the control unit (2020) causes the charging apparatus (20) to perform the charging of the lithium ion secondary battery (10), until a voltage of the lithium ion secondary battery (10) becomes a predetermined voltage. Thereafter, the control unit (2020) causes the charging apparatus (2) to suspend the charging of the lithium ion secondary battery (10), until a predetermined time elapses. Therefore, the control unit (2020) causes the charging apparatus (20) to further perform the charging of the lithium ion secondary battery (10), after the suspending. The predetermined time is a time t [minute] that satisfies “t≥−A+B*x+C*y.” x[g/cm2] represents weight per unit area of a negative electrode of the lithium ion secondary battery (10). y [g/cm3] is density of the negative electrode. A is a constant that is equal to or more than 50 and equal to or less than 70. B is a constant that is equal to or more than 500 and equal to or less than 620. C is a constant that is equal to or more than 30 and equal to or less than 36.