Secondary Battery Formation Cycles for Stable SEI Layers
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Solution Overview
Problem
Existing secondary battery formation processes are lengthy and costly, often taking several weeks, and result in unstable or non-uniform solid electrolyte interface (SEI) layers, leading to capacity loss and reduced cycle life.
Innovation Solution
A multi-step formation method involving controlled charging and discharging cycles with resting periods, utilizing graphene in the electrodes to stabilize the SEI layer, allowing for faster and more efficient formation of stable SEI layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional formation processes are used, then stable SEI layer is formed, but formation time is excessively long (several weeks)
Solution Approach 1:
The formation process is divided into multiple discrete cycles, each consisting of charge, rest, and discharge phases. This segmentation allows for systematic optimization of each phase to achieve stable SEI formation while reducing total time. The patent implements at least two formation cycles with specific parameters for each phase.
Solution Approach 2:
The patent employs periodic charge-discharge-rest cycles rather than continuous formation processes. Each cycle includes charging at a first rate, resting for a specified duration, and discharging at a second rate, repeating this periodic pattern to progressively build stable SEI layers more efficiently than conventional continuous processes.
2Reliability
If conventional formation processes are used, then SEI layer is formed, but the SEI layer is unstable or non-uniform
Solution Approach 1:
The patent incorporates preliminary rest periods between charging and discharging phases to allow uniform distribution of lithium ions and homogeneous SEI layer formation. This preliminary action before the next phase ensures that each cycle builds upon a uniform foundation, improving overall SEI uniformity.
Solution Approach 2:
The patent systematically varies key parameters including charge rate, discharge rate, and rest duration across multiple formation cycles. By changing these parameters in a controlled manner, the process achieves both stable and uniform SEI layers that would not be possible with fixed conventional parameters.
3Reliability
If longer formation time is used, then SEI layer stability improves, but productivity decreases
Solution Approach 1:
The patent maintains continuous useful action through optimized rest periods that are sufficient for lithium ion redistribution but not excessively long to cause production delays. The rest periods are precisely controlled to provide just enough time for uniform SEI formation while keeping the overall process efficient and productive.
Solution Approach 2:
The formation process uses dynamic adjustment of charge and discharge rates across multiple cycles, starting with more conservative parameters and progressively optimizing for both stability and speed. This dynamic approach allows the process to adapt to the evolving battery state, achieving high capacity retention without sacrificing productivity.
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
The method significantly reduces formation time while maintaining high capacity retention and cycle life, achieving similar performance to conventional methods in a fraction of the time without increasing costs.
Implementation Method 1
Batteries undergo a formation process to controllably create a stable solid electrolyte interface (SEI) layer within the electrodes of the battery
Implementation Method 2
Batteries undergo a formation process to controllably create a stable solid electrolyte interface (SEI) layer within the electrodes of the battery
Data Source
AI summary
In some aspects, a method can include applying a charge to a battery at an initial charge rate, the battery including an anode with silicon particles and graphene particles, a cathode, and a separator disposed between the anode and the cathode, the battery having a maximum voltage of Vmax, allowing the battery to rest for a first resting period, applying a charge to the battery at a first formation charge rate, discharging the battery at a first formation discharge rate, applying a charge to the battery at a second formation charge rate, the second formation charge rate greater than the first formation charge rate, discharging the battery at a second formation discharge rate, and applying a charge to the battery at a third formation charge rate to form the secondary battery, the third formation charge rate greater than or equal to the second formation charge rate.