A high-performance hybrid supercapacitor with Li4Ti5O12-C nano-composite prepared by in situ and ex situ carbon modification

In this work, we report on the synthesis of in situ and ex situ carbon-modified Li4Ti5O12-C (LTO-C) nano-composite and its application in a hybrid supercapacitor constructed using activated carbon (AC) and LTO-C nano-composite as positive and negative electrodes, respectively. The hybrid capacitors are characterized by galvanostatic charge-discharge, cycle life testing, and electrochemical impedance spectroscopy. The results reveal that the AC/LTO-C hybrid capacitors exhibit high rate capability and long cycle life. In the potential range of 1.5-3.0 V, the AC/LTO-C hybrid system can deliver a specific capacitance of 83 F g(-1) based on the total mass of AC and LTO-C electrodes at a current density of 60 mA g(-1) (2 C rate). At a higher discharge rate of 980 mA g(-1) (32 C), the capacity is 68 F g(-1), about 82 % of that at 2 C rate. After 9,000 deep cycles at 32 C, the hybrid capacitor still maintains 84 % of its initial capacitance. The specific energy of such hybrid system is 20 Wh kg(-1), which is at least twice that of an AC/AC system. Combining the high energy density with power capability, the AC/LTO-C hybrid supercapacitor has demonstrated high performance for applications needing high power output.