Battery Aging Estimation Under Fast-Charge Lithium Imbalance
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Solution Overview
Problem
Existing battery aging determination methods struggle to accurately estimate internal states, particularly when lithium ion batteries are rapidly charged, as lithium concentration becomes non-uniform, leading to unsteady distributions in electrodes, which affects impedance measurements and aging assessment.
Innovation Solution
A method that involves estimating a correction coefficient to account for the difference in lithium concentration distributions between low and high charging rates by comparing electric potentials and impedances during charging with different current waveforms, allowing for accurate internal state estimation and aging determination despite non-uniform lithium distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If rapid charging at high charging rate is performed to reduce charging time, then charging speed is improved, but lithium concentration becomes non-uniform and distribution becomes unsteady in electrodes
Solution Approach 1:
The patent applies parameter changes by measuring impedance at multiple frequencies to capture the dynamic behavior of lithium concentration distribution under different charging rates. By analyzing frequency-dependent impedance parameters, the system can determine aging characteristics even when lithium distribution is non-uniform due to rapid charging.
Solution Approach 2:
The patent replaces direct measurement of lithium concentration (which would require complex intrusive methods) with electrical impedance measurements. By substituting the mechanical/chemical measurement approach with an electrical measurement approach, the system can non-invasively assess lithium distribution uniformity and determine battery aging without disrupting the charging process.
2Loss of time
If impedance measurement is performed during rapid charging to enable real-time aging determination, then measurement timeliness is improved, but measurement precision deteriorates due to non-uniform lithium concentration
Solution Approach 1:
The patent introduces frequency-dependent impedance parameters as intermediary measurements that indirectly reflect lithium concentration distribution characteristics. Instead of directly measuring lithium concentration during rapid charging, the system uses impedance at multiple frequencies as an intermediary to infer aging characteristics, thereby maintaining measurement precision without sacrificing timeliness.
Solution Approach 2:
The patent performs impedance measurements at multiple frequencies (excessive action) to compensate for the non-uniform lithium distribution caused by rapid charging. By measuring at more frequencies than a single frequency would provide, the system can distinguish between impedance changes due to aging versus those due to transient lithium distribution effects, thereby maintaining measurement precision during rapid charging.
3Measurement precision
If correction for lithium concentration non-uniformity is applied to improve aging determination accuracy, then aging assessment precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the impedance measurement into multiple frequency components, analyzing each frequency range to extract specific aging-related parameters. By dividing the complex impedance spectrum into manageable frequency segments, the system can identify aging characteristics without requiring complex correction calculations for lithium distribution non-uniformity.
Solution Approach 2:
The patent creates a frequency-dependent impedance model that copies the essential aging characteristics from multi-frequency measurements. Instead of performing complex real-time correction calculations, the system uses pre-established relationships between frequency-dependent impedance parameters and aging states, thereby improving aging determination accuracy while minimizing device complexity.
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 precise estimation of battery internal states and aging even during rapid charging, effectively correcting for lithium concentration non-uniformity, thereby improving safety and preventing overcharging or over-discharge, and reducing the risk of accelerated battery aging.
Implementation Method 1
an impedance of the battery at each of a plurality of frequencies can be measured by supplying an electric current to the battery in a current waveform in which an alternate current is superposed on a charge current
Implementation Method 2
diffusion of lithium ions will be a rate-limiting factor in at least one of the positive electrode and the negative electrode
Data Source
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AI summary
In an approach, an aging determination method of a battery (5) as a target of determination is provided. With regard to a target electrode which is at least one of a positive electrode and a negative electrode of the battery (5), the method estimates a correction coefficient (ΔCc;ΔCa) to correct a difference between lithium concentration distributions in the target electrode at a time of charging with a first electric current (I1) and at a time of charging with a second electric current (I2) greater than the first electric current (I1) based on a difference between electric potentials of a target electrode at the time of charging with the first electric current (I1) and at the time of charging with the second electric current (I2), and an impedance (Rc2;Ra2) of the target electrode at the time of charging with the second electric current (I2).