Heat Treatment of Mechanochemically Prepared Amorphous LiNi_0.5Mn_1.5O₄–Li₂SO₄ as High-Voltage Positive-Electrode Material

LiNi 0.5 Mn 1.5 O 4 is a high-voltage positive electrode material for lithium-ion batteries. Amorphization of LiNi 0.5 Mn 1.5 O 4 with Li 2 SO 4 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 LiNi 0.5 Mn 1.5 O 4 . We heated amorphous LiNi 0.5 Mn 1.5 O 4 –Li 2 SO 4 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.