Composite Li[Li0.11Mn0.57Ni0.32]O2: Two-step molten-salt synthesis, oxidation state stabilization, and uses as high-voltage cathode for lithium-ion batteries

Composite Li[Li0.11Mn0.57Ni0.32]O2 was initially prepared by a two-step molten-salt method for uses as high-voltage cathode of lithium-ion batteries. This new synthetic route involves a low-temperature melting process of sodium acetate and a second high-temperature melting process of sodium carbonate, which is proved to be advantageous in simplifying the preparation processes of stabilizing oxidation states of framework metal ions at Mn4+ and Ni2+. In particular, the melting temperature of 900 °C for the second process is found to be crucial for the formation of the composite. The resultant composite crystallized in a layered structure, and was constructed by particles with dimensions about 100–150 nm. As a consequence of the stabilization of oxidation state and the formation of layered structure, the composite, when acting as a high-voltage cathode for lithium-ion batteries, exhibited a reproducible electro-chemical performance as featured by an initial discharge capacity of 250.8 mAh g−1 between 4.6 V and 2.0 V and a high cycling ability with little capacity decay at a current density of 20 mAg−1.

► A novel two-step molten salt method was successfully used to synthesize the composites Li[Li0.11Mn0.57Ni0.32]O2. ► The chemical reaction in the molten salt process and effect of calcinations temperature on the formation of layered structure were investigated. ► Two-step molten salt method is an effectively way to control over the oxidation states of the framework metal ions. ► The composite synthesized by the two-step molten method shows excellent electrochemical performance with good cycling ability.