Structure and interfaces of compositionally graded Li(Ni, Mn) x O y cathodes on (111) Nb-doped SrTiO3

Abstract

ABSTRACT Core–shell Li(Ni, Mn) x O y thin film has been deposited onto a (111) single-crystal Nb-doped SrTiO3 substrate by pulsed laser deposition. The thin film is ∼350–400 nm thick with a ∼60 nm-thick Ni-rich interface. The orientation relationship between the cubic Li(Ni, Mn)2 O4 spinel and distorted rhombohedral-layered Li(Ni, Mn)O2 phases and the substrates are [112] STO ||[112]Spinel and (1) STO ||(1) Spinel; [112] STO ||[210] LiNiO2 and (1) STO ||(00) LiNiO2; and [112] Spinel ||[210] LiNiO2 and (1) Spinel ||(00) LiNiO2. The film–substrate interface is sharp, non-reactive and free of planar defects. The interfaces between spinel, rhombohedral-layered Li(Ni, Mn)O2 and the order–disorder domains are coherent and diffused. As the spacing between octahedral cations in the spinel phase and in the Li(Ni, Mn)O2 phase is different; these two phases could be distinguished by quantifying the spacings between two octahedrally located cations. The electro-chemical behaviour of the film is not likely to be optimum even with the intended phase composition and chemistry due to disordering in Li (Ni, Mn)O2 and unsuitable orientation of the phases. Understanding such structural details is a precursor to tailor the electro-chemical activity in Li(Ni, Mn) x O y .