A Study of the Solid-Electrolyte-Interface (SEI) of ZnMn2O4: A Conversion-Type Anode Material for Li-Ion Batteries

The formation of a stable solid-electrolyte interface, SEI, is very crucial for the successful cycling of anode materials in Li-ion batteries. There is little known about the SEI layer formed at the surface of conversion-type anode materials in general and at the very high capacity ZnMn2O4 spinel anode material. In this work, Li-ion half-cells with ZnMn2O4 electrodes are assembled and tested at different conditions (cycling, temperature and the nature of the electrolyte) and the surface layer is examined by ex situ X-ray Photoelectron Spectroscopy (XPS) in the delithiated state. It is found that the SRI formed at ZnMn2O4 varies with composition but mostly composed of inorganic and organic components, similar to those observed for graphite. However, changes to the C 1s and 0 is spectra with cycling are not significant to correlate the extra reversible capacity to a polymer-like organic origin but rather to the presence of inorganic species such as LiF and LixPFyOz as evidenced by changes in the F 1s, P 2p and Li 1s spectra. (C) 2015 The Electrochemical Society. All rights reserved.