Effects of Structure and Magnetism on the Electrochemistry of the Layered Li1+x(Ni0.5Mn0.5)1-xO2 Cathode Material.

We have synthesized a series of Li1+x(Ni0.5Mn0.5)1-xO2 (LNMO) materials to study the influence of excess lithium ions on the structure and electrochemical behaviors of nickel-manganese-based layered compounds. The increasing content of Li+ ions in the transition-metal (TM) layer leads to the departure of the follower-like clusters to Ni-rich and Mn-rich clusters. The Ni2+ ions in the Li layer couple with adjacent transition-metal ions via strong 180° exchange interactions and moderate the local structure, which leads to magnetic clusters with finite size. Electrochemical performance shows that appropriate Ni2+ ions could improve the cycle stability without decreasing the rate capability. Among them, Li1.1Ni0.45Mn0.45O2 shows a rate capability of 76 mAh g-1 at 1000 mA g-1 and a lifespan of 300 cycles at 200 mA g-1. This work shows that structure moderation has an essential impact on its electrochemical performance. Besides this, the crystal and magnetic combined methods we use could offer a better way of studying cathode materials.