Lithium-Ion Battery Capacity Estimation via State-of-Lithiation Swing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion battery capacity fades over time due to electrode degradation, primarily caused by the formation of a solid-electrolyte interphase (SEI) and diffusion-induced stresses, which are not well understood, leading to inaccurate short-term empirical modeling of battery health in vehicles.
Innovation Solution
A method to estimate lithium-ion battery capacity loss by considering the state-of-lithiation swing and fracture of the SEI, using a mathematical model that incorporates the initial capacity ratio, number of charge-discharge cycles, and polynomial order derivatives, allowing for improved battery health management in vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If short-term empirical testing is used to model battery health, then the modeling process is simple and quick, but the accuracy and reliability of capacity estimation deteriorates over long periods
Solution Approach 1:
The patent transforms the battery health model from short-term empirical parameters to long-term analytical parameters by introducing state-of-lithiation swing (ΔSOL) as the key degradation parameter. The model uses analytical expressions relating capacity loss to ΔSOL, electrode capacity ratios, and cycle number, enabling accurate long-term prediction without relying on extended empirical data collection.
2Productivity
If the mechanical and electrochemical degradation mechanisms are not well understood, then the model development is faster, but the reliability and accuracy of battery health estimation deteriorates
Solution Approach 1:
The patent replaces complex mechanical and electrochemical degradation mechanisms with an analytical model based on lithiation-induced stress analysis. By substituting the need to directly model complex chemical reactions and mechanical failures with a stress-based analytical framework, the patent achieves reliable long-term predictions while maintaining model development efficiency.
Solution Approach 2:
The patent identifies and models the key parameter controlling degradation - the state-of-lithiation swing (ΔSOL) - which represents the mechanical stress experienced by the solid-electrolyte interphase. By focusing on this critical parameter rather than attempting to model all degradation mechanisms, the patent achieves both reliability and development speed.
3Device complexity
If capacity loss is not accurately estimated, then battery management is simpler, but vehicle operation and battery lifespan are adversely affected
Solution Approach 1:
The patent performs preliminary analytical modeling to establish capacity loss as a function of state-of-lithiation swing and cycle number before actual battery operation. This pre-established model enables accurate capacity estimation during vehicle operation without requiring complex real-time analysis, thus maintaining simple battery management while ensuring reliable vehicle operation.
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 accurate estimation and management of battery capacity loss, enhancing vehicle operations by predicting capacity fade based on lithiation-induced stresses and SEI fracture, thus improving battery health management.
Implementation Method 1
Lithium ions move from the negative electrode through the electrolyte to the positive electrode during discharging and from the positive electrode through the electrolyte to the negative electrode during charging
Implementation Method 2
capacity loss is a function that includes a state-of-lithiation swing with respect to a solid-electrolyte interphase of an electrode
Data Source
AI summary
A method includes controlling operation of a vehicle in response to an estimation of a capacity loss and capacity of a lithium-ion battery module of the vehicle. The estimation is a function that includes a state-of-lithiation swing and fracture of a solid-electrolyte interphase of an electrode of the lithium-ion battery module. The methodology can be implemented in a vehicle that includes a lithium-ion battery module and a controller that controls operation of the vehicle in response to such an estimation.