Lithium Ion Battery Formation Protocol for Cycling Stability
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Solution Overview
Problem
Secondary lithium ion batteries with high capacity lithium rich metal oxides experience performance degradation over multiple cycles, leading to significant irreversible capacity loss and reduced stability, especially due to the dissolution of transition metals into the electrolyte.
Innovation Solution
A formation protocol involving an initial charge to 4.125V-4.225V, followed by a rest period, and a subsequent charge to 4.275V-4.4V, which stabilizes the positive electrode active material and reduces irreversible changes, thereby maintaining battery performance over extended cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high capacity lithium rich metal oxides are used as positive electrode active materials, then battery capacity is improved, but cycling stability deteriorates due to transition metal dissolution
Solution Approach 1:
The patent applies preliminary action by performing a specific formation protocol before the battery enters normal cycling. This includes charging to 4.125V-4.225V, resting for 6+ hours, then charging to 4.275V-4.39V. This preliminary treatment stabilizes the positive electrode active material structure and reduces transition metal dissolution before cycling begins, thereby maintaining both high capacity and cycling stability.
Solution Approach 2:
The patent utilizes parameter changes by modifying the charging voltage parameters during formation. The two-stage charging process with specific voltage ranges (4.125V-4.225V followed by 4.275V-4.39V) and extended rest periods creates optimal conditions for stabilizing the lithium rich metal oxide structure, reducing harmful dissolution while preserving capacity.
2Ease of manufacture
If conventional formation protocols are used, then manufacturing process is simple, but irreversible capacity loss increases
Solution Approach 1:
The patent applies segmentation by dividing the formation process into distinct stages: first charge to 4.125V-4.225V, extended rest period of at least 6 hours, then second charge to 4.275V-4.39V. This segmented approach allows each stage to perform its specific function optimally, reducing overall irreversible capacity loss while maintaining manufacturing feasibility.
Solution Approach 2:
The patent employs periodic action through the extended rest period (at least 6 hours) between charging stages. This periodic interruption allows chemical reactions to stabilize, reduces polarization effects, and minimizes irreversible changes in the positive electrode active material, thereby reducing capacity loss.
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 protocol significantly improves the cycling stability and rate capability of lithium ion batteries, reducing transition metal dissolution and maintaining at least 92% capacity after 2500 cycles, with improved shelf life and reduced DC resistance.
Implementation Method 1
performing a first charge of the battery to a voltage from about 2.1 V to about 4.225V; after completing the first charge, holding the battery at an open circuit for a rest period of at least about 6 hours; and performing a second charge after the completion of the rest period to a voltage from about 4.275V to about 4.39V
Data Source
AI summary
Battery formation protocols are used to perform initial charging of batteries with lithium rich high capacity positive electrode to result a more stable battery structure. The formation protocol generally comprises three steps, an initial charge step, a rest period under an open circuit and a subsequent charge step to a selected partial activation voltage. The subsequent or second charge voltage is selected to provide for a desired degree of partial activation of the positive electrode active material to achieve a desired specific capacity while providing for excellent stability with cycling. The formation protocol is particularly effective to stabilize cycling for compositions with moderate lithium enrichment.