A novel synthetic route of micrometer-sized LiCoMnO4 as 5 V cathode material for advanced lithium ion batteries

Abstract

We synthesized micrometer-sized LiCoMnO4 with spinel structure by heating ion-exchanged LixCo0.5Mn0.5O2 with O6-type layered rocksalt structure at 600 °C. In this synthetic route, we first synthesized micrometer-sized NaxCo0.5Mn0.5O2 with P2-type layered rocksalt structure at 900 °C. Then, we prepared O6-LixCo0.5Mn0.5O2 by ion-exchange of Na+ for Li+ using LiNO3 at 280 °C. The structural transformation from layered rocksalt to spinel structure was confirmed at about 600 °C by the DTA curve. The average particle size of about 5 μm was almost the same as that of the starting P2-NaxCo0.5Mn0.5O2. The discharge capacity–voltage curves of the present LiCoMnO4 showed a maximum discharge capacity of about 105 mA h g−1 between 3.0 and 5.2 V vs. Li/Li+ at 25 °C, in spite of large micrometer-sized particles. We believe that micrometer-sized LiCoMnO4 would be important as one of 5 V cathode materials to achieve its higher compressed density of the electrode for advanced lithium ion batteries (LIBs), such as all solid-state LIB application.