Linear Sweep Voltammetry

Operational Method

A potentiostat controls the voltage scan rate and records the flow of charge through the system. During the scan, the potential changes at a constant rate, typically between one millivolt and one hundred millivolts per second. The slower scan rates allow the system to remain close to equilibrium, which increases the resolution of closely spaced electrochemical processes.

In contrast, rapid scans highlight transient intermediate species or diffusion-controlled kinetics.

Phase Detection

Faradaic current increases when the potential approaches the reaction threshold of a species. This change produces a distinct rise in the recorded current, which stabilizes or peaks depending on the diffusion of the reactant to the electrode surface. For electrolyte evaluation, the scan continues until the current rises indefinitely, indicating the onset of bulk decomposition of the salt or solvent.

Identifying these peaks assists in formulating electrolytes that can withstand high-voltage operation. By correlating each current peak with specific chemical reactions, engineers can map out the degradation pathways of novel additives and select the most stable compounds.

Diagnostic Limit

Charging currents can interfere with the signal and skew the calculated reaction voltages. This double-layer charging current is proportional to the scan rate, which makes it more prominent at faster sweeps. To isolate the chemical reaction, engineers use slow sweeps or employ microelectrodes with minimal surface area.

This precaution ensures the measurement yields the true thermodynamic decomposition value rather than an artifact of electrode capacitance.