Construction of core-shell Li3PO4@LiNi0·5Co0·2Mn0·3O2 cathode with improved cycling stability for lithium ion batteries

Residual Li on surface of spherical particles of LiNi 0·5 Co 0·2 Mn 0·3 O 2 (NCM523) was used to synthesise the core-shell structure of Li 3 PO 4 @ NCM523 for enhancing structural stability and long-cycle life. The optimal mass ratio (Li 3 PO 4 :NCM523) was found to be 0.5 wt% (LPO-0.5), and the thickness of Li 3 PO 4 on the surface of LPO-0.5 was approximately 12 nm. Compared with the pristine NCM523, the Li 3 PO 4 @ NCM523 cathode material not only has a longer cycle life, but also exhibits better structural stability. The Li 3 PO 4 layer inhibits the electrolyte from eroding the NCM523 cathode material and prevents the volume loss of the active microsphere during cycling. Furthermore, the core-shell structure of material observed via scanning electron microscopy was well maintained after 200 cycles. These results verify that the core-shell structure of material contributes to the improvement of Ni-based cathode structural stability and that the simple process favours the industrial application.