Electrochemical properties and interfacial reactions of LiNi0.5Mn1.5O4−δ nanorods

LiNi0.5Mn1.5O4−δ which possesses a high voltage of 4.7 V vs. Li+/Li and stable structure has been considered as a promising cathode material for high energy Li-ion batteries. In this study, well-crystallized LiNi0.5Mn1.5O4−δ nanorods with diameter of ∼50 nm and length of ∼500 nm were synthesized by a hydrothermal-solid state process followed by a lithiation reaction. It delivers ∼120 mA h g−1 discharge capacity under 30 mA g−1 at 3.5–4.9 V, and 90 mA h g−1 at 150 mA g−1. An unstable solid electrolyte interphase (SEI) film with thickness 2–10 nm was observed by transmission electron microscopy. The thick and unstable SEI layers are responsible for its low rate performance and low coulombic efficiency during cycling.