Li2NiTiO4: A New Insertion type Pseudocapacitive Electrode for Aqueous Lithium-Ion Capacitors

Abstract

Prabaharan et al first reported on the possibility of using a rocksalt type Li2NiTiO4 as a positive electrode for Li-Ion batteries and proven that the redox energy for the reaction Ni2+/4+ and Ti4+/3+ would favour facile redox reactions. We present here our first report on the possibility of using Li2NiTiO4 as pseudocapacitive electrode in Li based aqueous electrolyte and demonstrate the electrochemical properties of Li-Ion hybrid capacitor. Nanoparticles of Li2NiTiO4 have been synthesized by adopting a modified solvothermal process. The prepared Li2NiTiO4 nanoparticles were used as electrode material against a pure porous carbon electrode (AC) as Li-Ion capacitor couple, Li2NiTiO4//AC with a potential window of ∼1.6 V in aqueous electrolyte. Specific capacitance of Li2NiTiO4 was measured using a three electrode cell in Li+ alkaline electrolytes against Ag reference electrode. Electrochemical performance of the asymmetric capacitive couple was evaluated through constant current charge/discharge, cyclic voltammetry and ac impedance measurements. A hybrid Li-Ion capacitor Li2NiTiO4//AC was fabricated and studied for its capacitive performance. The electrochemical limitation of the potential window in aqueous medium < 1V is extended up to 1.6V by combining two different materials which predominantly enhances the energy density of the device. More specifically the asymmetric cell exhibits good cycling stability and high rate capability even at high scan rates.