Lithium-ion Battery Initial Charging via Differential Capacity Curves
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Solution Overview
Problem
Lithium-ion batteries often fail to achieve sufficient output performance due to insufficient film formation during the initial charging process, especially when using decomposition voltages as specified voltages, leading to inadequate film formation and battery performance.
Innovation Solution
An initial charging method for lithium-ion batteries that involves setting specified voltages based on the differential capacity curve, allowing for CCCV charging at peak voltages, and subsequent CV charging at reduced current rates to accurately form the film, thereby ensuring appropriate film formation and improved battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If decomposition voltage of positive electrode active material is used as specified voltage for initial charging, then charging can be completed, but film formation becomes insufficient and output performance is not achieved
Solution Approach 1:
The patent changes the voltage parameter from a fixed decomposition voltage to a dynamic voltage determined by the differential capacity curve (dQ/dV). By identifying peak voltages in the dQ/dV curve during initial charging, the method adapts the charging voltage to match the actual film formation requirements of the electrode materials, thereby achieving both complete charging and sufficient film formation for high output performance.
2Reliability
If charging and discharging are repeated in film-forming voltage region, then SEI film can be formed, but initial charging time increases
Solution Approach 1:
The patent extracts the essential film-forming voltage information from the differential capacity curve (dQ/dV) and uses this extracted information to guide the initial charging process. By identifying peak voltages in the dQ/dV curve, the method eliminates the need for time-consuming repeated charging and discharging cycles, achieving efficient film formation in a single charging process.
3Manufacturing precision
If CCCV charging is performed with highest voltage from differential capacity curve, then film formation accuracy improves, but charging process becomes more complex
Solution Approach 1:
The patent implements feedback control by using the differential capacity curve (dQ/dV) to determine the charging voltage. The dQ/dV curve provides real-time information about the charging state and film formation progress, allowing the system to automatically adjust the voltage to the optimal peak value. This feedback mechanism simplifies the control process while maintaining high film formation accuracy.
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 method enables accurate film formation and enhanced battery performance by using specified voltages derived from the differential capacity curve, allowing for both precise film formation and reduced initial charging time while maintaining high performance.
Implementation Method 1
a solid electrolyte interface (SEI) film is formed when a carbon-based material on a surface of a negative electrode mixture layer reacts with an electrolyte in a non-aqueous electrolyte-type lithium-ion battery
Data Source
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AI summary
An initial charging method for a lithium-ion battery according to this embodiment includes a process (S1) of preparing a cell having a positive electrode, a negative electrode, and an electrolyte and a process of charging the cell by using voltages based on the amount of change in a capacity of the cell per unit voltage as a specified voltage.