High-Performance Lithium-Ion Capacitors Based on CoO-Graphene Composite Anode and Holey Carbon Nanolayer Cathode

Lithium-ion capacitors (LICs) are regarded as a promising next-generation energy storage system because of their superior energy density, high power output, and prolonged cyclic life. However, the imbalance in reaction kinetics between the rapid non-Faradaic capacitive cathode and sluggish Faradaic battery anode is the main obstacle to high-performance LICs. Herein, we designed a novel anode material based on CoO-rGO by a simple solution-based method for Li-ion capacitors, which consists of CoO nanocrystallites uniformly distributed on graphene. It has the advantages of good electrical conductivity, high specific capacity, enhanced rate capability, and outstanding cyclic stability. Moreover, holey carbon nanolayers (HCNs) with enlarged interlayer spacing, increased specific surface area, and improved electrode kinetics were used as the high-capacity cathode material. CoO-rGO//HCN LICs were fabricated with a high energy density of 132 Wh kg(-1) at a power density of 220 W kg(-1) (based on the mass of positive and negative active materials) and good cycle life (capacity retention of 84.7% after 5000 cycles), showing that the CoO-rGO//HCN system represents a good choice for high energy density LICs with both high cyclic and rate performances.