Lithium silicate–lithium phosphate (xLi4SiO4 −(1 − x)Li3PO4) coating on lithium nickel manganese oxide (LiNi0.7Mn0.3O2) with a layered structure

Highlight
• Lithium silicate phosphate (LSP) is coated on LiNi0.7Mn0.3O2 by a sol-gel process.
• Residual lithium compounds on LiNi0.7Mn0.3O2 are used to form the coating layer.
• The coated sample shows higher Li+-diffusion coefficient than the bare sample.
• The coated sample shows low interfacial polarization as confirmed in CV analysis.
• Conclusively, the LSP-coating leads to better cycling stability and rate capability.

Solid solution of lithium silicate and lithium phosphate (xLi4SiO4 −(1 − x)Li3PO4, LSP) is coated on LiNi0.7Mn0.3O2 using the reaction between the residual lithium compounds (Li2CO3 and LiOH) on the surface of LiNi0.7Mn0.3O2 particles and the sol prepared from tetraethyl orthosilicate (TEOS) and anhydrous phosphoric acid. The physical properties of the samples are analyzed by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Electrochemical analyses, such as cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT) and galvanostatic cycling, are carried out for the samples. As a result, LSP-coating is found to be effective for improving the rate capability of LiNi0.7Mn0.3O2 as a cathode material for lithium-ion batteries. The specific capacity of the LSP-coated sample retains 58% at high current density of 7 C-rate (vs. 0.5 C-rate) while the bare sample shows only 44% capacity retention. Higher Li+-chemical diffusion coefficient and fast charge transfer process at the interface of the LSP-coated sample estimated by GITT and CV analyses are believed to be the reasons for the better rate capability.