Heat Treatment of Mechanochemically Prepared Amorphous LiNi0.5Mn1.5O4–Li2SO4 as High-Voltage Positive-Electrode Material

LiNi0.5Mn1.5O4 is a high-voltage positive electrode material for lithium-ion batteries. Amorphization of LiNi0.5Mn1.5O4 with Li2SO4 is known to result in high ionic conductivity and reversible capacity in a liquid-type cell. However, the operating voltage of the amorphous material is lower than that of the crystalline LiNi0.5Mn1.5O4. We heated amorphous LiNi0.5Mn1.5O4–Li2SO4 at 300–600 °C to partially crystallize the material and optimized the temperature. The resulting electrode materials exhibited a high reversible capacity of 200 mAh g–1 in both liquid-type and all-solid-state batteries. The heat treatment also increased the operating voltage, and a charge–discharge of 4.7 V vs the Li+/Li plateau was achieved.