Asymmetric Battery Pack Current Collector Tuning for C-Rate Balance
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Solution Overview
Problem
Asymmetric battery packs with differing capacities and designs connected in parallel experience imbalances in charging and discharging currents due to variations in impedance, leading to premature failure of lower impedance cells.
Innovation Solution
The solution involves adjusting the thickness of active layers and current collectors in battery cells to balance the C-Rate by reducing impedance, ensuring equal voltage drops and proportional current distribution across cells, thereby maintaining balanced charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If jelly rolls with differing capacities are connected in parallel, then the battery pack can provide higher total capacity, but the charging and discharging current becomes imbalanced due to different impedances
Solution Approach 1:
The patent applies local quality by varying the current collector thickness specifically in higher capacity jelly rolls to adjust their impedance locally. This targeted modification ensures that each jelly roll's impedance is proportional to its capacity, enabling balanced current distribution across parallel-connected cells with different capacities.
Solution Approach 2:
The patent changes the physical parameter of current collector thickness to modify the electrical impedance of battery cells. By increasing the current collector thickness in higher capacity cells, the impedance is reduced proportionally, which balances the C-Rate across parallel-connected cells with different capacities.
2Adaptability or versatility
If jelly rolls with same capacity but different electrode shapes are connected in parallel, then design flexibility is improved, but current imbalance occurs due to different impedances
Solution Approach 1:
The patent applies local quality by selectively modifying the current collector thickness in specific jelly rolls based on their electrode configuration. This targeted adjustment compensates for impedance differences arising from varying electrode shapes while maintaining the same capacity, ensuring balanced current distribution.
Solution Approach 2:
The patent introduces asymmetry by using different current collector thicknesses in jelly rolls with different electrode shapes, even when capacities are equal. This asymmetric design approach balances the overall impedance characteristics, enabling reliable parallel operation of cells with diverse geometries.
3Reliability
If current collector thickness is increased to reduce impedance, then C-Rate balancing is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by implementing varied current collector thicknesses only where needed - specifically in higher capacity or differently shaped jelly rolls. This selective approach achieves C-Rate balancing while minimizing the scope of manufacturing complexity, as standard thicknesses can be used in conventional cells.
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 enables balanced C-Rate charging and discharging across cells, preventing premature failure by ensuring equal impedance and proportional current distribution, thus extending the lifespan of battery packs.
Implementation Method 1
The second current collector having a second thickness that is greater than the first thickness to reduce an impedance of the second battery cell and balance a C-rate of the second battery cell with a C-rate of the first battery cell
Data Source
AI summary
Battery packs having jelly roll battery cells of different designs or capacities may have an imbalance in the charging and/or discharging current supplied to and provided by each jelly roll due to differences in capacity specific impedance between the battery cells of the battery pack. A C-rate (i.e., current relative to rated capacity) of a first and second battery cell connected in parallel may be balanced by altering properties of an active layer and/or a thickness of a current collector of the second battery cell to reduce an impedance of the second battery cell.