1. Acknowledgements
We acknowledge the University of St Andrews, the EPSRC (DTG), the Royal Society of Chemistry, the
International Union of Crystallography (IUCr) and the Energy Storage Research Network (ESRN) for
providing a studentship and funding to I.M. We thank Dr. Hajime Ishikawa for his work on Na2MoO2F4
and the Japan Society for the Promotion of Science for funding his research.
Irene Munaò 1, Robert Armstrong 2 and Philip Lightfoot 3
EaStCHEM School of Chemistry, University of St Andrews, Purdie Building, North Haugh, St Andrews, Fife, KY16 9ST, UK
email: 1im49@st-andrews.ac.uk, 2 ara@st-andrews.ac.uk, 3 pl@st-andrews.ac.uk
Introduction
 In the last few years, two concepts have become key issues in daily life: energy conversion and
energy storage. Recently the demand for large scale batteries to store the electricity in a
renewable and cleaner way has become important in the energy problem.
 Since they were discovered, the best candidates for this role have been Li-ion batteries, which
became the fundamental energy source for all portable electronic devices. However the
increasing cost of lithium, questions over its future availability, together with health and safety
problems mean that, in the last few years, research for new materials to substitute lithium has
started.
 The best candidate is found in sodium due to the low cost, the availability and the abundance of
sodium, the interest in the synthesis of electrodes based on sodium has increased, especially
using solvothermal methods. Hence, rechargeable sodium ion batteries could be the promising
candidates for a lot of applications.
 In this poster we present two aspects of our work. First, a novel perovskite, Na2MoO2F4, which
exhibits some unique structural features, and also has potential as an intercalation host. Second,
a novel iron phosphite, which shows promising electrochemical activity.
NaFe3(HPO3)2(H2PO3)6
 The synthesis was carried out at 140 °C for 72 hours, using 1 NaF, 1 Fe2O3, 12.2 H3PO3 in a dry reaction.
Crystal system Triclinic
Space group P -1
a 7.5302 (4) Å
b 9.1696 (3) Å
c 9.5965 (1) Å
α 60.586 (8)°
β 67.762 (10)°
γ 78.808 (12)°
R1 0.0272
Oxidation state of Fe III
c d
Techniques
 The syntheses were carried out in autoclaves using hydrothermal and solvothermal methods (Fig. 1).
 The Single Crystal X-ray diffraction was conducted using a Rigaku SCX mini diffractometer.
 The powder patterns were obtained using a Panalytical Powder diffractometer.
 Mix of active material, super S carbon and Kynar Flex 2801 as binder; ball mill for 3.5 hours (Fig. 2).
 Composite electrodes were cast on aluminium foil (Fig. 3).
 Electrodes were incorporated into coin cells with Na metal and NaClO4 as electrolyte solution (Fig.4).
Figure 12: Crystallographic data for NaFe3(HPO3)2(H2PO3)6
Figure 16: SEM pictures of NaFe3(HPO3)2(H2PO3)6
a
Na2MoO2F4
 The synthesis was carried out at 160 °C for 72 hours, using 1 NaF, 1 Guanidine Carbonate, 1 MoO2, 1 MoO3 and a mix of HF and water as solvent.
Crystal system Monoclinic
Space group P 21 / c
a 5.4800 (11) Å
b 5.7008 (7) Å
c 16.319 (3) Å
α 90°
β 91.316 (8)°
γ 90°
R1 0.015
Oxidation state of Mo VI
Figure 8: Polyhedral view of the octahedral tilt scheme
along the c-axis.
Figure 14: General polyhedral representation along the b axisFigure 13: General polyhedral along the a axis Figure 15: General polyhedral representation along the c axis
Figure 6: Asymmetric unit of Na2MoO2F4
Conclusions
Na2MoO2F4 and NaFe3(HPO3)2(H2PO3)6 are new interesting crystalline materials showing 3-D
framework structures with useful channels and holes for intercalation and de-intercalation of cations.
Na2MoO2F4 displays a unique variant of perovskite, exhibiting several unusual structural features,
including simultaneous atomic orderings at all three of the sites in the ABX3 scheme, together with a
very rare octahedral tilt system; the presence of an easily reducible cation, Mo6+, together with vacant
positions at the perovskite A-site suggest that intercalation chemistry will be possible to produce
Mo5+-containing perovskites. Future work will involve electrochemical studies of this material.
NaFe3(HPO3)2(H2PO3)6 is an interesting electrochemically active material, showing stable and linear
capacity and voltage around 2.8 V, comparable with similar compounds. Future work will involve
magnetic studies of this material.
Figure 7: General polyhedral view of the octahedral tilt
along the c axis.
Figure 5: Crystallographic data for Na2MoO2F4
Figure 10: General polyhedral view of the
octahedral tilt along the b axis.
Figure 9: Unit cell packing.
Figure 11: : (Left) General powder pattern and (right) zoom at low intensities of the of Na2MoO2F4; Teflon peaks are marked with an arrow
Figure 18: Na inserted during the charging process Figure 19: Relationship between capacity and number of cycle
Figure 1: Bomb autoclaves Figure 2: Ball Mill Figure 3: Tape Casting Figure 4: Coin Cell
 Na on both the A and B sites, with ordered (Na,vacancy) on the A-site, ordered (Na,Mo) on the B-site and
ordered (O,F) on the X-site (Fig. 6, 9).
 Octahedral tilting around the a-axis (Fig. 7, 8) and the b-axis (Fig. 9, 10) of the monoclinic unit cell; this
corresponds to simultaneous and equivalent ‘out-of-phase’ tilts around the a and b axes of the parent cubic
cell; Mo-centred octahedra blue, Na-centred octahedra yellow
 The ‘quadrupling’ of the unit cell along c is due to a more complex tilt around c, such that there are
successively ‘in-phase’, ‘out-of-phase’, ‘in-phase’ tilt relations along this direction or, alternatively, the tilt
sequence can be described as ‘AACC’, where ‘A’ represents anti-clockwise and ‘C’ clockwise rotation of a
single octahedron.
 FeO6 octhaedra (in red) bonded to each other by HPO3 tetrahedra (in pink) sharing with
them an oxygen atom; each Na atom is surrounded by four FeO6 octhaedra;
Na 6-coordinated (Fig. 13, 14, 15).
 Voltage around 2.8 V (Fig. 17); one atom of sodium inserted in the structure during the
electrochemical testing (Fig. 18).
 Stable and linear capacity (Fig. 19).
Figure 17: Capacity data
Solvothermal synthesis of some new 3-D
sodium–transition metal fluorine framework compounds
for solid–state batteries