Electrochemical study of the SnO2 lithium-insertion anode using microperturbation techniques

A disk pressed from commercial SnO2 powder, sandwiched between two nickel screen current collectors, was used as a lithium-ion secondary anode. Its electrochemical lithium insertion–extraction behavior was investigated by galvanostatic charge–discharge and galvanostatic intermittent titration (GITT) using a microcurrent on one current collector. The trans-electrode voltage was measured to monitor the transmissive resistance across the SnO2 electrode during the discharge–charge process. Special electrochemical impedance spectroscopy (EIS) protocols were used to investigate the kinetic and transmissive impedances during initial lithium insertion. Protocol B or C EIS, described in the text, give the local transmissive impedance near the operating current collector, while Protocol B′ or C′ give the local transmissive impedance near the other current collector. The use of special EIS protocols showed that the inner transmissive impedance near the operating current collector side is higher than that near the other current collector.