Dramatic change in the crystal structure was observed upon electrochemical delithiation. As a result Rh atoms migrate cooperatively and the structure transforms from layered to that, containing small rutile and bigger ramsdelite channels. Published in ACS Inorganic Chemistry. DOI: 10.1021/acs.inorgchem.6b01008

1. Reversible cation migration in LiRhO2
upon Li-extraction and insertion
The layered Li(M,Li)O2 oxides containing 3d transition metals are one of the best cathode material family for rechargeable Li-ion batteries. For the
further improvement of their performance (energy density) the cathode materials should operate at higher voltage. However, it results in the
irreversible oxidation of oxygen sublattice with the oxygen release, which hampers their application. The use of 4d transition metal oxides can
overcome this obstacle. Since 4d metals have higher electronegativity in comparison with 3d ones, their M-O bonds are more covalent. It allows to
reversibly oxidize oxo- O2- to peroxo-like species O2
n- (2<n<4) without O2 release [1].
Published as D. Mikhailova et al. Inorg. Chem., 2016, 55 (14), 7079
References:
[1] M. Saubanere, E. McCalla, J.-M. Tarascon, M.-L. Doublet, Energy Environ. Sci., 2016, 984.
[2] Palatinus, L.: PETS - program for analysis of electron diffraction data. Prague: Institute of Physics of the AS CR, 2011
O. Karakulina1, D. Mikhailova2, D. Batuk1, A. Abakumov1,3, J. Hadermann1
1 Electron Microscopy for Materials Research (EMAT), University of Antwerp, Antwerp, Belgium;
2 IFW Dresden, Institute for Complex Materials, Dresden, Germany;
3 Skoltech Center for Electrochemical Energy Storage, Skolkovo Institute of Science and Technology, Moscow, Russia.
Method
Introduction
LiRhO2
Conclusions
2D  3D structural transformation
At high voltage, the layered structure transforms in a 3D framework structure by cooperative migration
of Rh cations towards Li vacancies. Since both rutile and ramsdellite channels accept Li upon
discharge, extra 20% Li can be inserted.
In-situ synchrotron powder diffraction from LiRhO2 cathode upon
charge-discharge and the corresponding voltage profile.
• Rh – 4d transition metal ion
• LiRhO2 – isostructural and isoelectronic to
commercialized LiCoO2
Electron diffraction tomography
Galvanostatic cycling with potential
limitation curve of LiRhO2.
Process
1. Tilt a crystal with 1 degree step and
take diffraction (ED) pattern.
2. Combine ED patterns in 3D
reconstruction of reciprocal space
(PETS software [2].)
The ED patterns are taken mainly out of
zone that reduces the dynamical effect
caused by strong interaction of electron
beam with the crystal. Therefore, ED are
considered as quasi-kinematical.
– ab-initio crystal structure determination
method of nano-sized (~200 nm) single
crystals.
HAADF-STEM image
Authors acknowledge support from FWO under grant G040116N.
Fact 2. +20% more Li is
accepted upon discharge.
Fact 1. New phase only partially
transforms back to the layered phase.
Selected area electron diffraction patterns
S.G. C2/m,
a=14.188(2) Å,
b=3.0740(2) Å,
c=4.5050(7) Å,
β=92.087(8)°,
Rf = 0.268
Angular range: ±51°
Refined from
332 reflections
LiyRh3O6 – 3D framework structure with:
• Rutile-type [1x1] channels
• Ramsdellite-type [2x1] channels
Results
HAADF-STEM image
• Cooperative rotation of 2Rh-2O chains
• Formation of short 2.26 Å O-O bond in rutile channel