Half-Cell ECM Parameterization from Full-Cell Battery Measurements
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Solution Overview
Problem
Existing methods for parameterizing half-cell equivalent circuit models of lithium-ion batteries require invasive measurements, such as introducing a lithium reference electrode, which is time-consuming and compromises the integrity of the battery cell.
Innovation Solution
A method for parameterizing half-cell equivalent circuit models using non-invasive full-cell measurements, including frequency- and time-domain measurements to determine impedance values and threshold SOC values for lithium plating onset, followed by an optimization process with electrode-specific constraints to set RC element parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If invasive measurements with lithium reference electrode are used to parameterize half-cell ECM, then electrode-specific potential measurement accuracy is improved, but battery cell integrity deteriorates and preparation time increases
Solution Approach 1:
The patent uses a lithium metal electrode as an intermediary reference electrode that can be temporarily connected to the battery cell during measurement without permanently opening or modifying the cell structure. This intermediary approach enables precise electrode-specific potential measurements while maintaining cell integrity after measurement completion.
Solution Approach 2:
The patent performs preliminary calibration measurements to determine the open-circuit voltage characteristics of the battery cell before actual operation. This preliminary characterization data is stored and used later to calculate electrode-specific potentials during normal operation, eliminating the need for repeated invasive measurements.
2Ease of manufacture
If full-cell measurements are used to parameterize half-cell ECM, then battery cell integrity is maintained, but measurement precision for electrode-specific parameters deteriorates
Solution Approach 1:
The patent segments the full-cell measurements into electrode-specific contributions by measuring the open-circuit voltage at different state-of-charge levels and attributing voltage changes to specific electrodes based on their electrochemical characteristics. This segmentation enables extraction of electrode-specific parameters from overall cell measurements.
Solution Approach 2:
The patent replaces direct mechanical/electrical connection to electrode-specific reference electrodes with a computational approach that uses full-cell voltage measurements combined with electrochemical models to infer electrode-specific potentials, eliminating the need for physical intrusion into the cell structure.
3Manufacturing precision
If calibration measurements are performed to measure frequency-resolved impedance values, then ECM parameter accuracy is improved, but the battery cell cannot be used after measurements
Solution Approach 1:
The patent performs impedance measurements at multiple state-of-charge levels and frequencies to obtain sufficient data for accurate ECM parameterization, but uses only the minimum necessary measurement intensity that preserves cell functionality. The measurements are designed to be non-destructive, avoiding excessive current or voltage stress that would damage the cell.
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
Enables reliable and efficient parameterization of half-cell models without opening the battery cell, maintaining its integrity and reducing preparation time, while allowing for accurate prediction of electrode-specific aging mechanisms.
Implementation Method 1
performing, for multiple state-of-charge (SOC) values of the LIB cell, first full-cell measurements to determine, for each of the multiple SOC values, a respective representation of frequency-resolved impedance values of the LIB cell
Implementation Method 2
performing an optimization of parameter values of the ECM to fit the frequency-resolved impedance values
Data Source
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AI summary
The present disclosure relates to techniques for determining multiple parameterized values of an equivalent circuit model (ECM) that represents a Lithium-ion battery cell, enabling accurate simulation of various electrochemical processes occurring within the cell. A half-cell ECM is considered. The ECM can parameterized optimized by considering one or more constraints related to the electric potential of the negative electrode, breaking symmetry between parameter values associated with positive and negative electrodes. This results in improved accuracy of the ECM for simulating Lithium plating onset thresholds at different SOC values, enabling determination of optimized charging profiles or load constraints that avoid increased aging of the battery.