Solid state sodium battery with ceramic electrolyte and thin film electrodes cycling at room temperatureWednesday (28.09.2016) 12:30 - 12:45 Part of:
The development of safe sodium ion batteries with high performance at low temperature is still a challenge for the scientific community. In this work, we report a new design of all-solid state Na-ion battery cycled at room temperature. The ceramic electrolyte was a thick, dense pellet of NASICON-type Na3.4Sc2Si0.4P2.6O12 with high ionic conductivity of 8 x 10-4 S cm-1  , both electrode materials were deposited on this electrolyte as thin films of approximately 500 nm via magnetron sputtering. As a cathode material the recently studied and promising NaV3O8 cathode  was successfully deposited on the surface of the electrolyte and a crystalline structure was obtained after annealing. The selected anode material was Cu2Sb forming a NaxSb alloy  during cycling. The microstructure of the anode film was satisfactory and made it possible to get rid of the less practicable sodium metal anode.
The cell was cycled between 0.2 and 3 V at 10 μA (corresponding to C/2.6). The CV showed the expected redox potentials at 1.2 V and 2.0 V as well as very little capacity loss during cycling. However, a high internal resistance and low specific capacity were observed. A post mortem analysis of the cell showed no damages in the anode layer but a gap between the solid state electrolyte and the cathode material.
Overall, the high resistance of the cell should be reduced by improving the microstructure, the thickness of the electrolyte and the contact between the cathode and the electrolyte. In addition, the electronic conductivity of the cathode should be enhanced as proposed in recent studies [4, 5]. Nevertheless, two very positive results can be concluded: the issue of poor contact with Na metal in the solid state battery was resolved by using Cu2Sb anode and its PVD preparation leads to satisfactory layers. For the first time, a solid-state Na battery based on inorganic materials was cycled at room temperature.
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