Constructing tri-functional modification for spinel LiNi0.5Mn1.5O4via fast ion conductor

Abstract

Instable surface structure and low capacity retention hinder the further application of high voltage LiNi0.5Mn1.5O4 (LNMO) cathode in lithium-ion battery. In order to promote its electrochemical performances, Li6.4La3Al0.2Zr2O12 (LLAZO) with the intrinsic property of fast ion conductivity has been employed as a protective layer to modify surface of LNMO. By regulating the LLAZO contents, 1 wt % LLAZO coated LNMO (LLAZO-1) cathode shows a high capacity of 92.1 mAh g−1 over 600 cycles with a capacity retention of 72.6% at 1 C and a reversible capacity of 57.9 mAh g−1 at 20 C, much higher than those of pristine LNMO. Further investigation indicates that the greatly improved electrochemical performances of LLAZO-1 can be attributed to the LLAZO modification, which including the LLAZO surface coating and La3+ and Zr4+ gradient co-doping. In addition, the LLAZO precursor significantly restricts the growth of LNMO precursor particles during calcination process, shorting Li+ migration pathway. Thus, modification strategy effectively improves the structure stability of LNMO, accompanied with the enhancement in lithium-ion diffusion kinetics performances and confinement in particle growth. This optimization approach with tri-functions sheds light on novel electrode design and construction in rechargeable batteries.