Fabrication and characterization of a SnO2?RuO2 composite anode for a hybrid thin film battery

A SnO₂−RuO₂ composite (SnRuO) thin film possesses unique electrochemical properties for a hybrid between batteries and supercapacitors due to the fact that the SnRuO system shows battery and supercapacitor characteristics simultaneously. SnRuO thin films were prepared through the magnetron co-sputtering method in order to investigate the feasibility of a monolithic thin film hybrid battery. The SnRuO thin film as an anode film for a secondary battery demonstrated a first discharge capacity of 1557 μAh/cm²·μm; the second discharge capacity was 52% of the first discharge capacity. The degree of capacity fade of the SnRuO thin film was almost the same as that of the SnO₂ thin film, even though the capacity of the SnRuO thin film was larger than that of the pure SnO₂. In addition, the SnRuO thin film showed a supercapacitor behavior and exhibited a specific capacitance of 14 mF/cm² μm during 1000 cycles. These results suggest that SnRuO thin film could be used as a thin film supercapacitor as well as a thin film battery. Furthermore, this composite thin film holds promise for the fabrication of a monolithic thin film high power hybrid battery based on micro-processes.