All-solid-state electrochemical capacitors using MnO2/carbon nanotube composite electrode

MnO2/carbon nanotube (CNT) composite was prepared by a solution process. In the obtained MnO2-CNT composite, MnO2 particles were well-dispersed on CNTs. The specific capacitance of the MnO2-CNT composite in an aqueous electrolyte was higher than that of MnO2 and CNT. All-solid-state electrochemical capacitors (ECs) were fabricated using the MnO2-CNT composite as a positive electrode, activated carbon powder as a negative electrode, and phosphosilicate gel as an electrolyte. The obtained all-solid-state ECs operated at the temperature range between −30 °C and 100 °C. The specific discharge capacitance and the rate ability of the capacitors were improved by elevating temperature. In addition, the fabricated all-solid-state ECs exhibited excellent cycle performance at the temperature range between −30 °C and 100 °C for 20,000 cycles. These results indicate that all-solid-state ECs using MnO2 are promising energy storage devices with excellent stability and high reliability at the wide range of temperatures.