Electrochemical Performance of Lithium-Ion Hybrid Supercapacitors based on Activated Carbon and Nanoplatelet Li₄Ti₅O₁₂ Insertion Electrode Synthesized by Nanoscission Technique

Abstract

Electrochemical performance of hybrid supercapacitor (HSC) utilizing surface sculpted Li₄Ti₅O₁₂ (LTO) insertion electrode having nanoplatelet-like morphology and activated carbon (AC) electrode is investigated for energy storage application. Cyclic voltammetry (CV) at variable scan rates 0.5 to 60 mV.s⁻¹ in the 0-3.2 V range show pseusocapacitive behavior and fast rate of current change indicating rapid Faradaic kinetics. Nyquist impedance study show charge transfer resistance due to kinetic effects of electron transfer and Li⁺ de-intercalation process at the LTO anode. Low capacity (0.2 C-1C) charge-discharge (CD) curves show high Coulomb efficiency with marginal reduction at high 5-10 C rates due to irreversibility of adsorbed PF₆ anions at the electrolyte-AC interface. Galvanostatic CD cycling tests over 50 cycles at different C-rates show decline in storage capacity due to electrode polarization effects. Reduction, broadening and shift of the Raman line at 678 cm⁻¹ from Ti-O bonds in TiO₆ octahedra after cycling indicates Li insertion reactions in functioning of hybrid supercapacitor. The hybrid supercapacitor cells have shown energy density, 29 Wh.kg⁻¹ and power density, 350 W.kg⁻¹.