Reference electrodes for solid polymer electrolytes.

摘要

Electrochemical experiments were conducted on a binary metallic lithium-tin alloy that may be suitable as a reference electrode of the first kind in studies of lithium-polymer batteries. Two types of tin electrodes were tested: bulk tin foil and tin thin films deposited on a stainless steel substrate. Electrochemical test cells were fabricated, with tin, metallic lithium, poly(ethylene oxide), and lithium trifluoromethanesulfonate as electrodes and polymer electrolyte material. To form the alloy, the tin electrodes were galvanostatically loaded in situ with lithium. Each cell reached one or more steady-state voltage plateaus during the electrochemical reduction of lithium cations at the tin electrode surface. The lithiated tin foil electrode (1 C/cm(sup 2) of charge passed; area (approx) 5 cm(sup 2); thickness = 1.0 mm) demonstrated good voltage stability over months under open-circuit conditions. This electrode maintained an average open circuit voltage of 0.7336 V with only (plus minus)0.17 mV variance. Composition of phases in the thin film electrodes (x in Li(sub x)Sn) was coulometrically varied via reversible lithium loading and unloading reactions. Results show that three different, two-phase compositions may be formed that maintain flat voltage regions at approximately 0.53, 0.63, and 0.73 V vs lithium metal.