The comparison of electrochemical properties of ZnMn2O4 and ZnCr0.15Mn1.85O4 in an aqueous solution of ZnCl2

Abstract

As commercial Li-ion batteries are chiefly composed of a toxic and flammable electrolyte, as well as that Li itself is also toxic and not economical for widespread use due to its rare metal nature, the aim of this work is to create an aqueous Zn-ion battery that contains the same cathode material as used in Li-ion batteries. The materials ZnMn2O4 and ZnCr0.15Mn1.85O4 were synthesized through glycine nitrate combustion. The initial material ZnMn2O4 was doped with Cr3+ in order to diminish Jan-Teller distortion which prevents of Zn2+ ions to fully intercalate into their original sites of crystal lattice. The materials were characterized by X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM), while the electrochemical properties were examined through cyclic voltammetry in aqueous solutions of ZnCl2. The capacities obtained for the cyclic voltamogrammes recorded at 10 mVs-1 and 50 mVs-1 showed that cathode capacities for ZnMn2O4 amounted to be 12.4 mAhg-1 for 10 mVs-1, as well as 4.8 mAhg-1 for 50 mVs-1. The ZnCr0.15Mn1.85O4 demonstrated 45.3 mAhg-1 for 10 mVs-1, as well as 12.6 mAhg-1 for 50 mVs-1. The results obtained for the capacities of the original and doped material indicate that doping with Cr2+ partly diminishes the Jan Teller effect and facilitates the intercalation of Zn2+ ions.