High-performance hybrid supercapacitor based on pure and doped Li4Ti5O12 and graphene

Graphene nanosheets (G) and pure, as well as doped Mg-, Mn-, V-Li4Ti5O12, spinel structure have been synthesized. As-prepared materials were characterized by X-ray powder diffraction (XRD), FT-IR, scanning electron microscopy (SEM), cyclic voltammetry, and constant current discharge methods. The physical properties, as well as the possible role of the doped materials in supercapacitors, have been studied. The hybrid supercapacitor with pure or doped Li4Ti5O12 (LTO) anode was fabricated afterward to form the graphene/Li4Ti5O12. The specific energy, specific power, fast-charge capability, lifecycle, and self-discharge of the studied devices were compared. Metal doping did not change the phase structure while remarkably improved its capacitance at high charge/discharge rate. The hybrid supercapacitor utilizing pure or doped Li4Ti5O12 as an anode exhibits high capacitance compared to DLC because of the electrochemical process with intercalation/deintercalation of lithium into the spinel LTO. The capacitance of the hybrid supercapacitor decreases from 207 to 108 Fg−1 when discharged at several specific current densities ranging from 1 to 10 Ag−1. In contrast, the capacitance of the DLC is slightly decreased.