Secondary Battery Deterioration Estimation via Surface Stress Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing techniques for estimating the deterioration state of secondary batteries, particularly those with hysteresis in charging and discharging, do not accurately account for the influence of hysteresis, leading to inaccuracies in estimating the battery's condition.
Innovation Solution
A system and method that calculates surface stress on active materials within the battery, corrects the open circuit voltage curve using the calculated stress, and adjusts deterioration parameters to match the charging and discharging curves, thereby accurately estimating the battery's state by considering the hysteresis effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing techniques are used to estimate deterioration state without considering hysteresis, then the estimation process is simple, but the measurement precision of deterioration state is poor
Solution Approach 1:
The patent introduces surface stress as a new parameter to characterize hysteresis effects in the battery. By calculating surface stress from charge carrier amounts and incorporating it into the OCV curve correction, the system transforms the estimation approach from simple capacity tracking to a multi-parameter model that accounts for mechanical stress effects on electrochemical potential.
Solution Approach 2:
The patent uses surface stress as an intermediary variable that connects the charging-discharging history to the OCV curve. The surface stress calculation acts as a mediator between the charge carrier distribution and the electrochemical potential, allowing the system to account for hysteresis effects without directly measuring them.
2Measurement precision
If surface stress calculation and OCV curve correction are implemented, then the measurement precision of deterioration state is improved, but the device complexity increases
Solution Approach 1:
The patent performs preliminary calculation of surface stress based on charge carrier amounts before using it to correct the OCV curve. This preliminary action of calculating surface stress from known charge distributions allows the system to prepare correction factors in advance, reducing the complexity of real-time deterioration estimation.
Solution Approach 2:
The system uses feedback by comparing the corrected OCV curve with actual measurements to iteratively refine the deterioration parameters. The surface stress calculation feeds into the OCV correction, which then feeds back into the deterioration state estimation, creating a closed-loop system that improves accuracy through iterative refinement.
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
Enhances the accuracy of estimating the deterioration state of secondary batteries with hysteresis by accounting for surface stress and its impact on open circuit potential, leading to improved battery management and utilization.
Implementation Method 1
The controller calculates, based on a prescribed active material model, a surface stress of an object active material from a charge carrier amount inside the object active material
Implementation Method 2
The controller calculates, based on the calculated surface stress, an open circuit potential change amount in an electrode including the object active material
Implementation Method 3
Some systems of secondary batteries have a significant gap between the charging curve, which is a SOC-OCV curve obtained when the secondary battery is charged from the fully discharged state, and the discharging curve, which is a SOC-OCV curve obtained when the secondary battery is discharged from the fully charged state. Such a gap between the charging curve and the discharging curve is also referred to as existence of 'hysteresis' in the secondary battery.
Data Source
AI summary
An ECU calculates, based on a prescribed active material model, a surface stress of an anode active material from the lithium amount inside the anode active material, and calculates, based on the calculated surface stress, an open circuit potential change amount of the anode active material relative to an open circuit potential. The ECU corrects an anode open circuit potential calculated by a deterioration estimation process, using the open circuit potential change amount. The ECU calculates three deterioration parameters so that the measured OCV curve substantially matches the estimated OCV curve specified based on the corrected anode open circuit potential. The open circuit potential is an open circuit potential of the anode active material in the state in which a surface stress is not generated.