Surface Modification Driven Initial Coulombic Efficiency and Rate Performance Enhancement of Li1.2 Mn0.54 Ni0.13 Co0.13 O2 Cathode.

Abstract

Due to its high energy density and low cost, Li-rich Mn-based layered oxides are considered potential cathode materials for next generation Li-ion batteries. However, they still suffer from the serious obstacle of low initial Coulombic efficiency, which is detrimental to their practical application. Here, an efficient surface modification method via NH4 H2 PO4 assisted pyrolysis is performed to improve the Coulombic efficiency of Li1.2 Mn0.54 Ni0.13 Co0.13 O2 , where appropriate oxygen vacancies, Li3 PO4 and spinel phase are synchronously generated in the surface layer of LMR microspheres. Under the synergistic effect of the oxygen vacancies and spinel phase, the unavoidable oxygen release in the cycling process was effectively suppressed. Moreover, the induced Li3 PO4 nanolayer could boost the lithium-ion diffusion and mitigate the dissolution of transition metal ions, especially manganese ions, in the material. The optimally modified sample yielded an impressive initial Coulombic efficiency and outstanding rate performance.