Battery Cell Parameter Estimation Using EIS and CC-CV Profiles
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Solution Overview
Problem
Existing methods for determining battery cell parameters, such as those used in Li-ion cells, are costly and time-consuming, often requiring destructive testing and are inaccurate due to the lack of supplier-provided data, and fail to account for cell aging and variations among cells from different suppliers.
Innovation Solution
A method using Electrochemical Impedance Spectroscopy (EIS) and Constant Current-Constant Voltage (CC-CV) charge-Constant Current (CC) discharge responses to estimate parameters like electrode impedance and state of charge (SOC) through an EIS model and Reduced Order Model (ROM), allowing for non-destructive and cost-effective parameter estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If destructive testing and electron microscopy techniques are used to determine cell parameters, then measurement precision is improved, but loss of time and manufacturing cost increase significantly
Solution Approach 1:
The patent replaces destructive mechanical testing and complex electron microscopy with electrical measurement techniques (EIS and voltage relaxation methods). This substitution allows parameter extraction through non-destructive electrical signals, dramatically reducing time and cost while maintaining measurement precision for cell parameters like resistance and capacitance.
Solution Approach 2:
The patent creates an equivalent electrical circuit model that replicates the complex electrochemical behavior of the battery cell. By measuring voltage responses and fitting them to the equivalent circuit model, the system extracts parameters without physically dissecting or destroying the cell, thus saving time and enabling repeated measurements.
2Measurement precision
If destructive testing techniques are used to determine cell parameters, then measurement precision is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent replaces expensive destructive testing equipment and electron microscopy facilities with simple electrical measurement setups. This substitution dramatically reduces manufacturing costs while maintaining the ability to accurately determine cell parameters through standard battery testing equipment.
Solution Approach 2:
The patent uses inexpensive electrical test signals and equivalent circuit models instead of expensive destructive testing procedures. The method employs low-cost voltage measurements and computational fitting to extract parameters, making the process economically viable for mass production and quality control.
3Device complexity
If traditional equivalent circuit models are used for battery state estimation, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent enhances the traditional equivalent circuit model by dynamically extracting and updating electrical parameters (resistance, capacitance, inductance) from EIS and voltage relaxation measurements. This allows the model to adapt to cell aging and state changes, improving estimation accuracy while maintaining the simplicity of the circuit model structure.
4Ease of operation
If cell parameters are not updated to account for aging, then ease of operation is maintained, but reliability deteriorates
Solution Approach 1:
The patent performs preliminary extraction of cell parameters from EIS and voltage relaxation measurements during normal operation. These parameters are stored and used to update the equivalent circuit model before state estimation is performed, ensuring that aging effects are accounted for without adding complexity to the real-time operation.
Solution Approach 2:
The patent implements a feedback mechanism where cell parameters are continuously extracted from measurements and used to update the state of charge estimation. This feedback loop ensures that the model remains accurate as the cell ages, improving reliability while maintaining ease of operation through automated parameter updates.
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
Accurately estimates cell parameters, including geometric, kinetic, and thermodynamic properties, enabling precise state prediction and update detection, thus improving battery management systems (BMS) efficiency and accuracy.
Implementation Method 1
obtaining, by a device, an Electrochemical Impedance Spectroscopy (EIS) spectrum and a Constant Current-Constant Voltage (CC-CV) charge-Constant Current (CC) discharge response of the cell
Implementation Method 2
Constant Current-Constant Voltage (CC-CV) charge-Constant Current (CC) discharge response of the cell
Data Source
AI summary
A method for estimating a plurality of parameters pertaining to an electrochemical model of a cell may include: obtaining, by a device, an Electrochemical Impedance Spectroscopy (EIS) spectrum and a Constant Current-Constant Voltage (CC-CV) charge-Constant Current (CC) discharge response of the cell; extracting, by the device, a plurality of features from the EIS spectrum and a plurality of features from the CC-CV charge-CC discharge response of the cell; and estimating, by the device, the plurality of parameters based on at least one of the plurality of features of the EIS spectrum and at least one of the plurality of features of the CC-CV charge-CC discharge response of the cell.