Synthesis and Electrochemical Properties of the Li3PO4-Coated LiNi0.5Mn1.5O4 Cathode Materials for High-Voltage Lithium-Ion Batteries

High-voltage spinel (LiNi0.5Mn1.5O4; LNMO) has been a prospective cathode material that may exploit the maximal voltage of 5 V for lithium-ion batteries. However, the practical application has been hindered by the severe electrochemical instability of the Ni2+/Ni4+ redox couple at such a high voltage. Herein, we coated lithium phosphate (Li3PO4) on the surface of the LNMO by a wet-coating method to improve the electrochemical stability. The coating layer provided an effective cathode-electrolyte interphase, which prevented the excessive decomposition of the electrolyte on the surface of LNMO cathode. The Li3PO4-coated LNMO exhibited enhanced rate capability in accordance with the lowered solid-electrolyte interphase (SEI) and charge-transfer resistance values from electrochemical impedance spectroscopy.