Is LiNiO2 a mixed-valent system?

Speaker: Kateryna Foyevtsova
Date & Time: Monday April 10th, 2017 - 11:15 AM
Location: AMPEL 311
Local Contact: George Sawatzky
Intended Audience:

The layered nickel oxide LiNiO2 is well known as a promising cathode material for rechargeable Li-ion batteries.

Yet, despite the great technological appeal and the decades of intense research, some of its basic properties remain poorly understood.

One such puzzling property of LiNiO2 is the apparent absence of a cooperative Jahn-Teller distortion of the NiO6 octahedra, which is both expected from the low-spin Ni3+ ions and indeed observed in the iso-structural and iso-electronic compound NaNiO2.

In this talk, I will present a detailed ab initio study of LiNiO2 and propose a structural model that can reconcile seemingly conflicting results from different experimental probes.

From the analysis of theoretically simulated atomic pair distribution functions, I find that the system most likely exists in a mixed-valent state where the Ni3+ ion degeneracy is removed via both the Jahn-Teller and the charge-disproportionation mechanisms.