Elevated electrochemical performance of (NH4)3AlF6-coated 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2 cathode material via a novel wet coating method

A novel wet method of (NH4)3AlF6 coating was explored to enhance the electrochemical performance of Mn-based solid-solution cathode material 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2. The X-ray powder diffraction patterns show that the coating material is pure-phase (NH4)3AlF6 and both pristine and coated samples can be indexed to hexagonal α-NaFeO2 layered structure with space group of R-3 m. The field-emission scanning electron microscope images and the energy dispersive X-ray spectroscopy show that (NH4)3AlF6 is successfully coated on the surface of active particle. The (NH4)3AlF6 coated electrodes exhibit improved electrochemical performance, for instance, the initial charge-discharge efficiency was promoted by 5% (NH4)3AlF6 coating, the 1 wt.% and 3 wt.% coated electrodes deliver elevated cycling ability which is ascribed to the lower resistance between electrode and electrolyte as indicated by AC impedance measurement at different cycles. In addition, the coated-electrodes also give enhanced rate capability particularly for 1 wt.% NAF-coated electrode performing surprising capacity of 143.4 mAh g−1 at 5 C higher than that of 109.4 mAh g−1 for pristine electrode. Furthermore, the 1 wt.% NAF-coated electrode also shows improved cycle and rate performance at 55°C.