Comparative Study of the Power and Cycling Performance for Advanced Lithium-Ion Capacitors with Various Carbon Anodes

In recent years, an increased attention has been focused on Li-ion capacitors (LICs) which are high power hybrid devices. Various carbon materials (hard carbon (HC), soft carbon (SC) and graphite) have been investigated for use as the negative electrodes for LICs. The rate capabilities are compared by half cells with carbon anode as working electrode and lithium foil as counter electrode, and by LIC full cells with test current density up to 20 mA cm−2. It is found that the LIC with HC and SC at 20 mA cm−2can be maintained up to 72.5% and 70%, compared to that at 0.5 mA cm−2, which is better power performance than the graphite materials. LICs with both HC and SC as anodes displayed better cycle lifes than graphite anode. After 100,000 high-rate charge-discharge cycles, the capacity retention of the LIC with HC anode maintained higher than 85%. The Scanning electron microscopy (SEM) images, surface area and the pore size distribution are also studied and compared for the various carbon anode materials.