Deterioration behavior of a multi-phase vanadium-based solid solution alloy electrode

Deterioration behavior of an electrode made of V 4 TiNi 0.65 Co 0.05 Nb 0.047 Cr 0.058 was studied by means of impedance spectroscopy, scanning electron microscopy (SEM) and impedance spectroscopy. The reaction resistance related to the lowest frequency semi-circle increased considerably and dischargeability became worse with cycling. The double layer capacitance for the same semi-circle became smaller after 50 cycles. The SEM observation of the cross-section of the cycled electrodes indicated that voids were formed around alloy particles embedded in a matrix of Cu powder, and crack formation and dissolution of the TiNi second phase proceeded with cycling. These phenomena indicate that dissolution of the second phase caused loss of reaction sites and TiNi networks as a current collector.