A High Energy and Power Li‐Ion Capacitor Based on a TiO2 Nanobelt Array Anode and a Graphene Hydrogel Cathode

Abstract

A novel hybrid Li‐ion capacitor (LIC) with high energy and power densities is constructed by combining an electrochemical double layer capacitor type cathode (graphene hydrogels) with a Li‐ion battery type anode (TiO 2 nanobelt arrays). The high power source is provided by the graphene hydrogel cathode, which has a 3D porous network structure and high electrical conductivity, and the counter anode is made of free‐standing TiO 2 nanobelt arrays (NBA) grown directly on Ti foil without any ancillary materials. Such a subtle designed hybrid Li‐ion capacitor allows rapid electron and ion transport in the non‐aqueous electrolyte. Within a voltage range of 0.0−3.8 V, a high energy of 82 Wh kg−1 is achieved at a power density of 570 W kg−1. Even at an 8.4 s charge/discharge rate, an energy density as high as 21 Wh kg−1 can be retained. These results demonstrate that the TiO 2 NBA//graphene hydrogel LIC exhibits higher energy density than supercapacitors and better power density than Li‐ion batteries, which makes it a promising electrochemical power source.