Low-temperature direct synthesis of layered m-LiMnO2 for lithium-ion battery applications

Layered monoclinic LiMnO2 is a potential low-cost alternative to LiCoO2 cathode for lithium-ion batteries. However, its application is limited partly because it cannot be synthesized easily. In this work, we successfully synthesized phase-pure layered LiMnO2 in a one-step low-temperature process using electrolytic manganese dioxide (EMD) as the manganese precursor at 450 °C in Ar atmosphere by a carbothermal reduction method. The initial carbon to manganese ratio has to be optimized to remove impurities. The particle size of the material is between 40 and 60 nm. The synthesized sample shows an initial reversible capacity of about 180 mAh g−1. The synthesis method is further applied to make boron-doped samples, which significantly enhanced the stability of the material, especially at high temperature. The boron-doped samples maintain a capacity of 150 mAh g−1 for 100 cycles and give a capacity of about 100 mAh g−1 at a current of 1000 mA g−1 (equivalent to 10C rate). The ability to directly synthesize the material at low temperature is crucial because it allows further improvement of material performances through methods such as surface coating and the use of electrolyte additives to reduce surface reaction and Mn-dissolution.