Enhanced high-rate capability and cycling stability of Na-stabilized layered Li1.2[Co0.13Ni0.13Mn0.54]O2 cathode material

Abstract

Na-stabilized Li_1.2−xNa_x[Co_0.13Ni_0.13Mn_0.54]O₂ is synthesized by introducing larger Na ions into the Li slabs of the layered material through a simple polymer-pyrolysis method. The structural and morphological characterization reveals that the Na doping leads to a more ordered structure with regular cubic morphology and enlarged Li layer spacing. Electrochemical experiments show that the Na-doped Li_1.17Na_0.03[Co_0.13Ni_0.13Mn_0.54]O₂ electrode can deliver larger reversible discharge capacity (307 mA h g⁻¹), higher initial coulombic efficiency (87%), greatly improved rate capability (139 mA h g⁻¹ at 8 C) and cycling stability (89% capacity retention after 100 cycles) in comparison with the undoped Li_1.2[Co_0.13Ni_0.13Mn_0.54]O₂ electrode. The superior electrochemical performance of the Na-doped material is due to the enhancement of the structural stability and the enlargement of the Li slab space of the layered material, which facilitate the stabilization of the host lattice and allow rapid diffusion of Li ions in the bulk lattice.