Meaning
Analytical method evaluates changes in the physical dimensions of a cell during cycling to identify mechanical phase transitions and degradation. Utilizing derivative strain slope analysis allows researchers to track electrode expansion and contraction with high resolution. The method is applicable primarily to pouch cells where external displacement sensors can measure thickness changes.
This non-destructive tool reveals structural shifts without requiring cell disassembly.
Thermodynamic Correlation
Phase transitions in graphite and silicon anodes produce specific volume changes during lithiation. The derivative of this expansion curve aligns with electrochemical voltage plateaus. This alignment helps identify when the anode enters highly stressed states.
It provides a window into the structural health of the active materials.
Measurement Process
The process uses high-resolution displacement transducers to record cell thickness while cycling at low current rates. Software then calculates the first derivative of the strain with respect to the state of charge. This calculation highlights subtle changes in the rate of expansion that would otherwise go unnoticed.
It connects mechanical stress directly to electrochemical state.
Engineering Application
Designers use these mechanical profiles to optimize the pressure applied by module constraints. Correct pressure extends cycle life by preventing electrode delamination and particle cracking. Sourcing teams use this evaluation to compare the mechanical stability of different chemistry formulations.
This feedback loop improves both pack safety and durability.
