Synthesis and Investigation of Nano LiMn2O4-rGO as a Positive Electrode in Energy Storage Systems

Supercapacitors (SCs) deliver high power density but low energy density [1]. One way for increasing the energy density of a SC is improving the efficiency of charge storage that is affected by the electrode materials [2]. Mn-based oxides such as LiMn2O4 (LMO), have economic and environmental advantages and excellent electrochemical performance as attractive positive electrode materials in aqueous-electrolyte supercapacitors [3,4]. The performance of SCs can be improved via shortening the ionic diffusion length and providing large surface areas for electrode reactions and the easiness of electron transfer. In this regard, the nanosize materials and composites of high conductive compounds such as reduced Graphene Oxide (rGO) [1,5,6] play the main role. In this work, we have synthesized nano LMO oxides and LMO-rGO composites by a simple, low temperature and fast hydrothermal method. Thus, these materials have been investigated as positive electrode materials by CV, chrono-potentiommetry, and EIS. After optimization of the ratio of the composite components, that is LMO: GO ratio of 40:60% as positive electrode material, the composite was characterized with different techniques including XRD, Raman, EDX, SEM and TEM as well as BET and TGA analyses. The LMO-rGO electrode shows a wide potential window of 1.1 V in Li2SO4 aqueous electrolyte. The specific capacitance of the composite electrode at 1 A/g is 215 F/g, which shows superiority over an LMO electrode, 130 F/g. The 65% increase in capacitance of the material shows a synergistic effect of rGO on electrochemical performance of the LMO electrode.