cm0c02880_si_001.pdf (1.23 MB)
From LiNiO2 to Li2NiO3: Synthesis, Structures and Electrochemical Mechanisms in Li-Rich Nickel Oxides
journal contribution
posted on 2020-10-23, 03:15 authored by Matteo Bianchini, Alexander Schiele, Simon Schweidler, Sabrina Sicolo, François Fauth, Emmanuelle Suard, Sylvio Indris, Andrey Mazilkin, Peter Nagel, Stefan Schuppler, Michael Merz, Pascal Hartmann, Torsten Brezesinski, Jürgen JanekThe
Li–Ni–O phase diagram contains a variety of compounds,
most of which are electrochemically active in Li-ion batteries. Other
than the well-known LiNiO2, here we report a facile solid-state
method to prepare Li2NiO3 and other Li-rich
Ni oxides of composition Li1+xNi1–xO2 (0 ≤ x ≤
0.33). We characterize their crystal and electronic structure, exhibiting
a highly oxidized Ni state and defects of various nature (Li–Ni
disorder, stacking faults, oxygen vacancies). We then investigate
the use of Li2NiO3 as a cathode active material
and show its remarkably high specific capacity, which however fades
quickly. While we demonstrate that the initial capacity is due to
irreversible O2 release, such process stops quickly in
favor of more classical reversible redox mechanisms that allow cycling
the material for >100 cycles. After the severe oxygen loss (∼15–20%)
and prolonged cycling, the Bragg reflections of Li2NiO3 disappear. Analysis of the diffracted intensities suggests
the resulting phase is a disordered rock salt-type material with high
Li content, close to Li0.5Ni0.5O, never reported
to date and capable of Li diffusion. Our findings demonstrate that
the Li–Ni–O phase diagram has not been fully investigated
yet, especially concerning the preparation of new promising materials
by out-of-equilibrium methods.