Heat Treatment of Mechanochemically Prepared Amorphous LiNi_0.5Mn_1.5O₄-Li₂SO_{4 as High-Voltage Positive-Electrode Material}

LiNi0.5Mn1.5O4-Li2SO4 is a high-voltage positive electrode material for lithium-ion batteries. Amorphization of LiNi(0.5)Mn(1.5)O(4)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 degrees 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.