Three-Electrode Reference Setup for Anode Overpotential Measurement
Three-electrode anode overpotential testing isolates uncompensated potential thresholds to prevent lithium plating during fast charge algorithm design
Ir Drop
Meaning
Electrical potential losses occurring within an electrochemical system arise from the flow of current through the resistive components of the cell. This ir drop represents the voltage penalty associated with the internal resistances of the electrolyte, active materials, current collectors and terminal tabs. Minimizing this reduction is essential to maximizing the energy efficiency of the device under high discharge rates.
Ohmic Component
Electronic and ionic paths both contribute to the overall resistance that drives the voltage loss. While metal foils provide electronic resistance, the electrolyte creates ionic resistance. This combination generates a linear voltage reduction directly proportional to the current.
Operational Limit
High charge rates exacerbate these losses, which raises the temperature of the cell and limits the usable capacity. The ir drop causes the cell to reach its upper or lower cutoff voltage prematurely, which truncates the charging or discharging cycle. This truncation reduces the actual energy delivered to the load.
Measurement Method
Characterization of these losses typically involves electrochemical impedance spectroscopy or current interruption techniques to isolate the resistive contribution. Sourcing engineers use the resulting data to evaluate the quality of foil coatings and the efficiency of the internal cell geometry. This evaluation helps guide decisions during the procurement of high-power cells.
It also allows developers to compare the performance of different cell tab configurations under various thermal and electrical loads, ensuring the selected design meets the power requirements of the application.