Enhanced electrochemical performances of LiNi0.5Mn1.5O4 spinel in half-cell and full-cell via yttrium doping

Pristine and yttrium-doped LiNi0.5-xYxMn1.5O4 spinel powders (x = 0, 0.005, 0.01, 0.02, 0.04) were synthesized by a facile solid-state method. The effect of yttrium doping content on the electrochemical properties of LiNi0.5-xYxMn1.5O4 was investigated by using half-cells paired with lithium metal and full-cells paired with graphite. XRD and FT-IR analysis shows that the cation disordering degree (Mn3+ content) first increase (x ≤ 0.02) and then decrease with Y doping content and the Y doping can effectively inhibit the formation of LixNi1-xO impurity phase. Electrochemical results show that in half-cells, the LiNi0.5-xYxMn1.5O4 cathode material with appropriate Y doping (x = 0.01) exhibits optimal rate capability and cycling stability, due to higher phase purity, enlarged lattice parameter, higher disordering degree, higher structural stability by introducing YO bond, lower charge transfer resistance and higher lithium ion diffusion coefficient, although the 0.2C discharge capacity is slightly lower than pristine LiNi0.5Mn1.5O4. Atomic Absorption Spectroscopy result shows that appropriate Y doping can effectively decrease the transition metal dissolution to certain extent, despite of higher Mn3+ content. All above factors lead to the improved cycling performance of Y-doped electrode in half-cells paired with metallic Li at elevated temperature (55 °C) and in full-cells paired with graphite at room temperature.