Abstract:
Sodium layered oxide compounds (NaxM1-xO2) have drawn significant attention as cathode
materials for Na-ion batteries (NIB). Their Li analogues have already been
comprehensively understood. In this study, powder compositions of (NaxNi1-x)O2, (x = 0.1,
0.25, 0.5, 0.75) were prepared by the Pechini method. For that, metal nitrates of NaNO3
and Ni(NO3)2.6H2O were mixed according to stoichiometric formula of the nominal
compositions. The powder synthesis process was completed by calcining the ash product
at 800 °C for two hours in air. The synthesized powders were uni-axially pressed at 150
MPa and the green pellets were subsequently sintered at 800 °C for two hours in static air.
The electrical conductivity of these materials were determined by performing d.c. electrical
conductivity measurements on sintered pellets by the four-probe method. The conductivity
measurements were performed in a cyclic manner on heating and cooling in air, in the
temperature range 25 - 200 oC.
This study revealed the possibility of synthesizing NaxNi1-xO2, x = 0 - 0.75 compositions by
the Pechini wet chemical synthesis technique. All these prepared materials showed an
increase in conductivity in an exponential manner with increasing ambient temperature.
This is a good indication of the semiconducting nature, which is the main requirement for
an electrode material. In this NaxNi1-xO2 system, the x = 0.1 composition showed a
sufficiently high electrical conductivity of 3.5 x 10-3 S/cm at room temperature. These
achievements in electrical conductivity indicate the potential of NaxNi1-xO2 compositions for
NIB cathode application.
