Bi-functions of titanium and lanthanum co-doping to enhance the electrochemical performance of spinel LiNi0.5Mn1.5O4 cathode

Abstract

Spinel LiNi0.5Mn1.5O4 (LNMO) cathode material doped with Ti and La co-doping were synthesized through a solid-state method. The bi-functions of the Ti and La co-doping is realized. On the one hand, the stability of the LiNi0.5Mn1.5O4 crystal structure is enhanced and the Mn3+ interference inside the material is reduced by the Ti doping. On the other hand, the co-doped La contributes to the formation of Li0.5La0.5TiO3 (LLTO) superionic conductor incorporated in the bulk LiNi0.5Mn1.5O4 phase, thereby enhancing the Li diffusion. With the help of XRD, FTIR, SEM and STEM techniques, La and Ti in the crystallographic structure and the dispersion of the LLTO superionic conductor in the bulk LNMO spinel are discussed. At the optimized molar ratio of 20:1 between LNMO and LLTO, the composite exhibits the best electrochemical performances in terms of the reversible capacity, rate capability and cycling stability. The lithium ion diffusion coefficient in the bulk LNMO phase is tripled by the LLTO superionic conductor incorporation. Keywords: Lithium ion batteries, Spinel LiNi0.5Mn1.5O4, Li0.5La0.5TiO3, Co-doping, Superionic-conductor