Improving electrochemical properties by Na+ doping for Co-Free Li-Rich Mn-Based layered oxide

Abstract

The capacity of Co-free Li-rich Mn-based layered oxide decreases rapidly due to the irreversible lattice oxygen lose and the crystal structure change. The sodium modified cathode materials are synthesized via the sol–gel method and the electrochemical properties are investigated. Specifically, the first discharge capacity of Li1.18Na0.02Mn0.54Ni0.26O2 is 150.5 mAh·g−1 at 2C, demonstrating a capacity preservation rate of 94.1 % after 100 cycles. And the diffusion coefficient of Li1.18Na0.02Mn0.54Ni0.26O2 is 1.2152 × 10-15, which is better than 1.3798 × 10-16 of the undoped material. This work demonstrates that appropriate Na+ doping can stabilize the crystal structure, increase the lithium layer spacing and reduce the irrevocable escape of lattice oxygen within material.