Mismatched Parallel Battery Cells for High Current Pulse Applications
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Solution Overview
Problem
Solid-state and thin film batteries face limitations in high current applications due to low diffusion rates of charge-carrying species, particularly lithium ions, which restrict their ability to achieve high output current densities.
Innovation Solution
A mismatched battery configuration is introduced, where two battery cells with different internal resistances and charge capacities are connected in parallel, allowing the cell with lower resistance to power a device during the on period and the higher resistance cell to recharge during the off period, optimizing current output and recharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If solid-state batteries use thicker cathodes to provide higher specific energies, then energy density is improved, but lithium ion diffusion rate decreases due to longer diffusion path through metal lattice
Solution Approach 1:
The battery is divided into multiple cells with different internal resistances and charge capacities. The first battery cell has higher charge capacity and lower internal resistance, while the second battery cell has lower charge capacity and higher internal resistance. This segmentation allows each cell to specialize in different functions, resolving the contradiction between energy storage and power delivery.
Solution Approach 2:
The invention changes the parameters of the battery system by using mismatched cells with different internal resistances and charge capacities instead of identical cells. This parameter variation enables the system to achieve both high current output (through the low resistance cell) and high energy storage (through the high capacity cell).
2Power
If solid-state batteries are designed for high current density applications, then current output is improved, but the low diffusion rates of charge-carrying species through the cathode thickness limit performance
Solution Approach 1:
The battery system is segmented into two cells with different characteristics. The first cell is optimized for energy storage with higher charge capacity, while the second cell is optimized for power delivery with lower internal resistance. This segmentation allows the system to achieve high current density without being limited by the diffusion rates in a single thick cathode.
Solution Approach 2:
The parallel connection configuration acts as an intermediary mechanism that allows the two cells with different characteristics to work together. The low resistance cell mediates the high current demand while the high capacity cell provides the energy reservoir, effectively resolving the diffusion rate limitation.
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 configuration significantly enhances the battery's ability to provide high current output and efficient recharging, overcoming the limitations of diffusion rates and improving performance in high current applications.
Implementation Method 1
the second battery cell having a second internal resistance and second charge capacity, such that the second internal resistance is sufficiently lower than the first internal resistance
Implementation Method 2
the first battery cell is capable of recharging the second battery cell during the power-off time period
Data Source
AI summary
A pulse mode apparatus comprises a mismatched battery electrically connected to a pulse mode device having a pulse duty cycle with a power-on time period and a power-off time period. The mismatched battery comprises a first battery cell having a first internal resistance and first charge capacity, and a second battery cell having a second internal resistance and second charge capacity, and the battery comprises at least one of the following: (1) the second internal resistance is less than the first internal resistance, and (2) the second charge capacity is less than the first charge capacity. The battery also has a pair of electrical connectors electrically coupling the first and second battery cells in parallel, a pair of terminals connected to the first or second battery cells, and a casing around the first and second battery cells with the terminals extending out of the casing.