Effect of manganese salt type on the structure and zinc storage property of Mn2O3/Mn3O4 composites synthesized by sucrose-assisted thermal decomposition method

In this work, Mn2O3/Mn3O4 composites are prepared by a facile sucrose-assisted thermal decomposition method using MnCl2 & sdot;4H2O, Mn(CH3COO)2 & sdot;4H2O, and MnSO4 & sdot;H2O as manganese sources, respectively. The results demonstrate that manganese salt type has a significant influence on the morphology and phase composition of the final Mn2O3/Mn3O4 composites. The composites prepared from MnCl2 & sdot;4H2O or Mn(CH3COO)2 & sdot;4H2O possess a porous sheet-like morphology, while the Mn2O3/Mn3O4 composite prepared from MnSO4 & sdot;H2O has a much finer nanosheet morphology. The Mn2O3 contents in the composites prepared from MnCl2 & sdot;4H2O, Mn (CH3COO)2 & sdot;4H2O, and MnSO4 & sdot;H2O are about 57.8%, 95.0%, and 27.0%, respectively. Due to the differences in morphology and phase composition, the Mn2O3/Mn3O4 composites prepared from MnCl2 & sdot;4H2O and Mn (CH3COO)2 & sdot;4H2O exhibit better zinc storage properties than the composite prepared from MnSO4 & sdot;H2O. Among the three samples, the Mn2O3/Mn3O4 composite prepared from Mn(CH3COO)2 & sdot;4H2O shows superior zinc storage capability in short-term cycling and the best rate capability; the Mn2O3/Mn3O4 composite prepared from MnCl2 & sdot;4H2O presents the best long-term cycling performance and moderate rate capability; the Mn2O3/Mn3O4 composite prepared from MnSO4 & sdot;H2O displays the worst zinc storage capability and rate performance. EIS and CV analysis demonstrate that the Mn2O3/Mn3O4 composites prepared from MnCl2 & sdot;4H2O or Mn(CH3COO)2 & sdot;4H2O have a low charge transfer resistance and obvious pseudocapacitive behavior during the charge/discharge process. The charge/discharge mechanism of the Mn2O3/Mn3O4 composites is also explored by ex-situ XRD characterization. This work provides a reference for the simple preparation of high-performance Mn2O3/Mn3O4 composites utilizing different manganese salts.