Investigating Cathode Dissolution By Homogeneous Sol-Gel Coating on Manganese Dioxide Nanofibers to Extend Battery Performance

Abstract

The cathode dissolution is a known phenomenon for manganese dioxide (MnO2) based cathode materials in both aqueous and non-aqueous batteries. Upon battery discharge, reduced Mn3+ species disproportionate (2Mn3+→ Mn4+ + Mn2+) and Mn2+ dissolves into the electrolyte causing the loss of active material. While MnO2 is a promising cathode for rechargeable aqueous zinc ion batteries (ZIB) due to its availability and low toxicity, the electrochemical performance is limited during battery cycling due to the dissolution of the cathode. In this work, a homogeneous sol-gel SiO2 coatings with various thicknesses (0.5-5nm) on hydrothermally synthesized α-MnO2 nanorods are reported. In-depth characterization of SiO2 coated α-MnO2 are done by XRD, BET, XPS, TGA and SEM/TEM to analyze the surface of the silica coated α-MnO2 cathodes. The electrochemical performance of the SiO2 coated α-MnO2 cathodes are studied in two electrode zinc batteries at room temperatures using Zn metal anode and in 1 M ZnSO4 and 1 M TFSI electrolytes. The cathode dissolution is investigated by determining the total dissolved Mn content and characterization of the used electrodes. Electrochemical performances of SiO2 coated α-MnO2 are evaluated using Cyclic Voltammetry, EIS, and Galvanostatic Cycling tests. This study will further benefit all different battery types that have the same cathode dissolution problem.