PERFORMANCE OF LITHIUM ION CAPACITORS USING AQUEOUS ELECTROLYTE AT HIGH TEMPERATURES

摘要

Aqueous lithium ion capacitors (DCs) with LiFePO4 positive electrodes and activated carbon (AC) negative electrodes were developed and their electrochemical performances were investigated by cyclic voltammetry, galvanostatic charge/discharge and ac impedance spectroscopy at various temperatures. It is found that the stable voltage window for the aqueous LICs is 0-1.7 V. The rate capability of the LIC is much higher than that of the LiFePO4 electrodes. The Ohmic resistance and electrochemical impedance of the LiFePO4 and AC electrodes decreases with increasing the temperature, leading to the high rate capability of the LICs. The capacity of the LICs gradually drops in 25 cycles and then keeps constant at 30 °C. The LICs still exhibit good cyclability at 50 °C, but the capacity of the LICs keep constant during 50 cycles and then gradually decay during further cycling test at 70 °C.