Fast-Charging Li-Ion Cell Formation Method for SEI Stability
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Solution Overview
Problem
Fast-charging lithium ion batteries face reduced cycling lifetime due to instability in the solid-electrolyte interphase (SEI) layer, which is exacerbated by high charging and discharging rates, leading to premature capacity degradation.
Innovation Solution
A method involving controlled SEI formation through a series of charge-discharge cycles with adjusted currents and voltage ranges, starting with narrow voltage ranges and expanding as battery capacity deteriorates, along with initial low current charging to enhance electrolyte wetting and prevent parasitic processes at electrode-electrolyte interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high charging and discharging rates are used for fast-charging lithium ion batteries, then charging speed is improved, but cycling lifetime is reduced due to SEI layer instability
Solution Approach 1:
The patent applies preliminary action by conducting extended formation cycles with controlled voltage ranges and current rates before the battery enters normal operation. This preliminary treatment pre-stabilizes the SEI layer structure, creating a more robust interface that can withstand subsequent fast-charging stresses. The formation process includes initial cycles at limited voltage ranges (e.g., 3.0-4.2V) followed by gradual expansion to full ranges, allowing the SEI to develop optimal properties before high-rate operation begins.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting voltage ranges, current rates, and cycle durations during the formation process based on battery state monitoring. The voltage window is progressively expanded from restricted ranges to full operating ranges, while current rates are modulated to optimize SEI formation kinetics. These parameter variations enable controlled SEI development that balances formation speed with structural stability, resolving the contradiction between fast charging capability and cycling lifetime.
2Reliability
If extended formation cycles with controlled voltage ranges are performed, then SEI layer stability is improved, but formation time is increased
Solution Approach 1:
The patent applies dynamics by making the formation process adaptive rather than static. The voltage range, current rate, and cycle duration are dynamically adjusted based on real-time monitoring of battery parameters such as impedance, voltage response, and temperature. The voltage window expands progressively from restricted ranges (e.g., 3.0-4.2V) to full ranges as the SEI matures, allowing the process to accelerate once stability is achieved. This dynamic approach optimizes the balance between thorough SEI formation and reasonable formation time.
Solution Approach 2:
The patent implements feedback mechanisms by continuously monitoring battery response during formation cycles and using this information to adjust subsequent cycle parameters. Electrical impedance spectroscopy, voltage relaxation analysis, and temperature monitoring provide feedback on SEI development progress. When the SEI reaches sufficient stability (indicated by impedance plateau or voltage response criteria), the system automatically adjusts the voltage range expansion rate or current profiles to prevent over-formation. This feedback control ensures optimal SEI stability while minimizing unnecessary formation time extension.
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 approach significantly extends the cycling lifetime of fast-charging lithium ion batteries by stabilizing the SEI layer and optimizing battery performance by managing voltage levels based on battery health, thereby minimizing capacity loss and enhancing overall battery longevity.
Implementation Method 1
operate by lithiation of lithium ions from the electrolyte into the anode material (intercalation in case of graphite anodes)
Implementation Method 2
lithiation of lithium ions from the electrolyte into the anode material (intercalation in case of graphite anodes)
Implementation Method 3
a SEI (solid-electrolyte interphase) layer is formed by interaction between electrolyte components and Li ions on the anode surface
Data Source
AI summary
Methods, systems and battery modules are provided, which increase the cycling lifetime of fast charging lithium ion batteries. During the formation process, the charging currents are adjusted to optimize the cell formation, possibly according to the characteristics of the formation process itself, and discharge extents are partial and optimized as well, as is the overall structure of the formation process. During operation, voltage ranges are initially set to be narrow, and are broadened upon battery deterioration to maximize the overall lifetime. Current adjustments are applied in operation as well, with respect to the deteriorating capacity of the battery. Various formation and operation strategies are disclosed, as basis for specific optimizations.