High tap density of Ni3(PO4)2 coated LiNi1/3Co1/3Mn1/3O2 with enhanced cycling performance at high cut-off voltage

The LiNi1/3Co1/3Mn1/3O2 is first obtained by the control ed crystallization method and then coated with Ni3(PO4)2 particles. The effects of the coating on rate capability and cycle life at high cut-off voltage are investigated by elec-trochemical impedance spectroscopy and galvanostatic measurements. The element ratio of Ni:Mn:Co is tested by inductively-coupled plasma spectrometer (ICP) analysis and it testified to be 1:1:1. It is indicated that Ni3(PO4)2-coated LiNi1/3Co1/3Mn1/3O2 has an outstanding capacity retention, where 99%capacity retention is maintained after 10 cycles at 5C discharge rate between 2.7 V and 4.6 V. The electrochemical impedance spectroscopy (EIS) results show that the current exchange density i0 of the coated sample is higher than that of LiNi1/3Co1/3Mn1/3O2, which is beneficial to its electrochemical performances. All the conclusions show that the Ni3(PO4)2 coating can prominently enhance the high rate performance of the LiNi1/3Co1/3Mn1/3O2, especially at high cut-off voltage.