High-capacity lithium insertion materials of lithium nickel manganese oxides for advanced lithium-ion batteries: toward rechargeable capacity more than 300 mA h g−1

Abstract

Lithium nickel manganese oxides Li[Ni_xLi_(1/3−2x/3)Mn_(2/3−x/3)]O₂ (x = 1/2, 2/7, and 1/5) are prepared and characterized by XRD and FT-IR, and the samples are examined in non-aqueous lithium cells at room temperature and 55 °C. Among these materials LiNi_1/2Mn_1/2O₂ (x = 1/2) shows the highest operating voltage and the smallest polarization with a rechargeable capacity of ca. 230 mA h g⁻¹ and Li[Li_1/5Ni_1/5Mn_3/5]O₂ (x = 1/5) shows the lowest operating voltage and the largest polarization with a rechargeable capacity more than 300 mA h g⁻¹. Extraordinarily large rechargeable capacity of Li[Li_1/5Ni_1/5Mn_3/5]O₂ together with an anomalously long voltage plateau at 4.5 V only observed at first charging process is examined by window-opening charge and discharge, continuous charge and discharge combined with differential chronopotentiometry at room temperature and at 55 °C, and possible mechanisms are discussed in terms of lithium insertion scheme.