Stabilized structural and electrochemical properties of LiNi0.5Mn1.5O4 via ZrF4 nanolayer modification for Li-ion batteries

Uniform and thin ZrF4 nanolayer with diverse contents are successfully coated on the surface of spinel-structured LiNi0.5Mn1.5O4 (LNMO) material with Fd3¯m space group via a simple co-precipitation process. The morphologies and structures of the as-prepared samples are studied by X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), energy dispersive spectrometric (EDS) analyses and high resolution transmission electron microscopy (HRTEM). Electrochemical measurements demonstrate that a desirable capacity retention of 95.5% could be obtained for 2 wt% ZrF4-surface modified LNMO after 120 cycles, much greater than that of 80.1% for the pure material. Meanwhile, 2 wt% ZrF4 modified sample shows superior rate performance, which delivers a high capacity of 106 mAh g−1 at 2C. Intensive electrochemical impedance spectroscopy (EIS) and Fourier transform infrared (FTIR) analyses indicate that ZrF4 surface modification is effective in stabilizing the electrode/electrolyte interface at high voltage, through averting the direct contact and depressing the undesirable side reactions between cathode and electrolyte. The ZrF4 surface modification on LNMO proposed herein, with a facile and repeatable strategy, provides a perspective in enhancing surface structural stability as well as electrochemical reversibility for electrode functionalization.