Abstract: Triaminoguanidinium chloride was transformed into 1,2,3-tris(benzylamino)guanidinium chloride
(3-Cl) in two steps. Anion exchange allowed the preparation of further salts 3-X. The crystal and
molecular structures of 3-Cl, 3-I, 3-CF3COO and 3-CF3SO3 were determined. It was found that
both the conformation of the cation and the nature of the anion determines the packing in the solid
state. Interestingly, three different conformations of the cation were observed in the crystals.
Abstract: We report on the electrochemical properties of
layered manganese oxides, with and without cobalt substituents,
as cathodes in sodium ion batteries. We fabricated
sub-micrometre-sized particles of Na0.7MnO2+z and
Na0.7Co0.11Mn0.89O2+z via combustion synthesis. X-ray diffraction
revealed the same layered hexagonal P2-type
bronze structure with high crystallinity for both materials.
Potentiostatic and galvanostatic charge/discharge cycles in
the range 1.5–3.8 V vs. Na | Na+ were performed to identify
potential-dependent phase transitions, capacity, and capacity
retention. After charging to 3.8 V, both materials had an
initial discharge capacity of 138 mAhg−1 at a rate of 0.3 C.
For the 20th cycle, those values reduced to 75 and 92 mAh
g−1 for Co-free and Co-doped samples, respectively. Our
findings indicate that earlier works probably underestimated
the potential of (doped) P2-type Na0.7MnO2+z as cathode
material for sodium ion batteries in terms of capacity and
cycle stability. Apart from doping, a simple optimization
parameter seems to be the particle size of the active material.
