Enhanced electrochemical performance of Li-rich cathode Li[Li0.2Mn0.54Ni0.13Co0.13]O2 by surface modification with lithium ion conductor Li3PO4

Li-rich layered cathode Li[Li0.2Mn0.54Ni0.13Co0.13]O-2 is prepared via a co-precipitation followed with high-temperature calcination, and then successfully modified with nano-Li3PO4 by ball milling and annealing. The TEM and EDS reveal that Li3PO4 is homogeneously coated on the particle surface of Li[Li0.2Mn0.54Ni0.13Co0.13]O-2. And the electrochemical performance of Li[Li0.2Mn0.54Ni0.13Co0.13]O-2 is significantly improved by coating with lithium ion conductor Li3PO4. The Li3PO4-coated sample delivers a high initial discharge capacity of 284.7 mAhg(-1) at 0.05 C, and retains 192.6 mAhg(-1) after 100 cycles at 0.5 C, which is higher than that of the pristine sample (244 mAhg(-1) at 0.05 C and 168.2 mAhg(-1) after 100 cycles at 0.5 C). The electrochemical impedance spectroscopy (EIS) demonstrates that the resistance for Li/Li3PO4-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O-2 cell was reduced compared to Li/Li[Li0.2Mn0.54Ni0.13Co0.13]O-2, which indicates the Li3PO4 coating layer with high ionic conductivity (6.6 x 10(-8) S cm(-1)) facilitates the diffusion of lithium ions through the interface between electrode and electrolyte and accelerates the charge transfer process. What is more, the Li3PO4 coating layer can also act as a protection layer to protect the cathode material from encroachment of electrolyte. The two aspects account for the enhanced electrochemical performance of Li3PO4-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O-2. (C) 2016 Elsevier B.V. All rights reserved.