Electrochemical behavior of lithium ion capacitor under low temperature

Lithium-ion capacitor (LIC) is a novel electrochemical energy storage device that bridges the performance gap between the electrical double-layer capacitor and lithium ion battery. In this work, we fabricated lithium-ion capacitors (LICs) with activated carbon (AC) positive electrode and pre-lithiated hard carbon (HC) negative electrode. The effect of low temperature on the electrochemical performance of LIC is investigated by the galvanostatic charging-discharging, electrochemical impedance tests, rate performance and cycle performance testing. The electrolyte viscosity increases, the ionic conductivity decreases and ionic migration becomes slow in the charge-discharge process with the decrease of temperature, causing the increase of resistance and the electrochemical polarization, which is responsible for the attenuation of LIC electrochemical performance. LIC at the temperature of −20 °C exhibits the optimal low temperature electrochemical performance, high energy density up to 76.6 Wh kg−1 and power density as high as 5.8 kW kg−1 (based on active material mass of two electrodes), excellent capacity retention of 80.1% after 5000 cycles.