Nano‐Sized AlPO4 Coating Layer on Graphite Powder to Improve the Electrochemical Properties of High‐Voltage Graphite/LiNi0.5Mn1.5O4 Li‐Ion Cells

A high‐voltage graphite/LiNi 0.5 Mn 1.5 O 4 (LNMO) system is a promising candidate for next‐generation Li‐ion batteries with a high energy density. However, it has the drawback of severe capacity fading caused by the consumption of active Li + ions due to the reduction of the products of electrolyte oxidation and LNMO dissolution from the LNMO cathode on the graphite anode. Herein, graphite coated with different amounts of AlPO 4 (0.5, 1, and 2.5 wt%) is prepared by an electrostatic attraction combined with a precipitation conversion method, and used as an anode for the LNMO/graphite full cell. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and elemental mapping images show that AlPO 4 disperses homogeneously on the surface of graphite, and its thickness is between 10 and 30 nm. Electrochemical measurement results show that LNMO/AlPO 4 @graphite cells show better cycling stability and higher coulombic efficiency than the LNMO/graphite cell. Among them, the LNMO/0.5 wt% AlPO 4 @graphite cell shows the best cycling stability. By combining all the analytical results, the improvement mechanism of LNMO/AlPO 4 @graphite cells is mainly that the side reactions that consume the active Li + ions are greatly reduced because the AlPO 4 coating can block the migration of the products of electrolyte oxidation and LNMO dissolution to the graphite.