Quantifying Lithium Plating Signals in Isothermal Cell Cycling Tests
Quantify lithium plating signals by isolating post-charge open-circuit voltage plateaus and integrating dQ/dV stripping peaks under isothermal thermal control.
Open Circuit Overpotential
Meaning
Thermodynamic potential differences measured between an active battery cell under current load and its true equilibrium voltage state define internal electrochemical resistance. Quantifying open circuit overpotential reveals the sum of activation, ohmic, structural and mass transfer polarizations present within a cell during operation. The measured value reflects the extra voltage energy required to drive faradaic reactions at a given current rate relative to the zero-current resting state.
The concept stops applying once current stops flowing and the cell reaches complete thermodynamic relaxation.
Kinetic Origin
Internal charge transfer resistance and ion transport limitations shift operating voltages away from open circuit potential. Experiencing open circuit overpotential causes terminal voltage during discharge to sit below true equilibrium open circuit voltage, while charge voltage rises above equilibrium. Mass transfer limitations at high C-rates produce concentration gradients in the electrolyte, inflating polarization losses.
Measurement Method
Intermittent pulse testing protocols isolate kinetic polarizations from background thermodynamic potentials. Determining open circuit overpotential involves applying current pulses followed by resting periods, such as in galvanostatic intermittent titration techniques. Analyzing the voltage relaxation curve following current interruption allows researchers to separate ohmic resistance from charge transfer overpotentials.
Efficiency Loss
Voltage deviations away from equilibrium directly reduce round-trip energy efficiency in commercial battery systems. A high open circuit overpotential increases internal heat generation during heavy load periods, demanding additional thermal management cooling power. Minimizing these kinetic losses through cell design improves net system efficiency.