Investigating the energy storage performance of the ZnMn2O4 anode for its potential application in lithium-ion batteries

Abstract

ZnMn2O4 has been intensively researched over the past two decades as a potential alternative to graphite anode material in the lithium-ion battery (LIB). The positive impact of the ZnMn2O4 anodes on high capacity and rate capability has been consistently proven in lithium half-batteries. However, there are currently insufficient studies to support these effects in Li-ion full cell configuration by pairing with a state-of-the-art cathode. Herein, we report ball-in-ball hollow structured ZnMn2O4, which was synthesized by a facile solvothermal method. The synthesized ZnMn2O4 showed high capacity, good cycling stability, and excellent rate capability as an anode material for LIBs in a half cell. The reaction mechanism was followed through a combination of in situ X-ray diffraction (XRD) and ex situ synchrotron X-ray absorption spectroscopy (sXAS) techniques. In situ XRD analysis reveals the ZnO and MnO phase formation with no evidence of Mn3O4 upon delithiation. The sXAS study shows that the reduction of ZnO to metallic Zn proceeds efficiently, whereas the reduction of MnO to metallic Mn is nominal during lithiation. The expected formation of the LiZn alloy is the first to be reported under the tested conditions. Overall, the results indicate that the Li-driven conversion reaction of the ZnMn2O4 anode is only partially reversible. However, the ZnMn2O4 anode displayed its sustainability in a full cell by pairing with a commercial LiNi0.5Mn1.5O4 cathode. The battery energy density reached 561.5 Wh Kg(-1), which was calculated based on the cathode mass, and exhibited a total specific capacity of 113 mAhg(-1). Thus, this study presents a comparison between the half and full cell data demonstrating that the half-cell predicts the overrated capacity value of a conversion-type anode in LIBs. Furthermore, it highlights the reporting practices in a Li-ion full cell for properly resolving its advantages.