Comparative analysis of electrochemical performances and capacity degrading behaviors in lithium-ion capacitors based on different anodic materials

摘要

Lithium-ion capacitors (LICs) are an optimal candidate to bridge the gap between lithium-ion battery and conventional supercapacitors as the promising electrochemical energy storage devices with fast charging-discharging capability and long cycle life. A three-electrode LIC pouch cell is fabricated employing an electrochemically driven lithium pre-doping method. Active materials of cathode and anode of LIC cells are activated carbon and pre-lithiated carbon, respectively. The electrochemical performances and capacity fading behaviors of LICs in an operating potential range of 2.2-3.8V have been analyzed. The most direct influencing factor to LIC cycle performance is pointed at the developed capacity originated from the effective application of cathode material during the charge storage process. It was deeply discovered that the determined key to properties in a LIC system refers to the type of anode material and anode potential swing. Capacity fading of LICs upon cycling is proposed to be caused by the lapse of lithium stored in anode by dV/dQ analysis and an increase of internal resistance mainly emphasized on the structure difference through EIS characterization. As the energy density is increased to reach 63.05Whkg(-1) based on the weight of both cathode and anode active materials and concurrently the initial capacitance is retained up to 96.33% after 5000cycles at 8C, HC as an anode material shows the prominent electrochemical performance.