Speaker
Description
Sodium-metal chloride (ZEBRA) batteries apply ceramic Na-β”-alumina electrolytes with molten sodium metal anode. As electrolyte and anode support extreme current densities of above 1 A/cm2 [1], it is the cathode which limits cycling rates and power capability in these batteries.
We have designed planar sodium-metal chloride battery cells capable of cycling (partially) molten electrodes at up to 350 °C [2]. Here we investigate cycling of sodium-metal chloride cells with a mixed Ni/NiCl2 and Fe/FeCl2 cathode. Cells are assembled in the discharged state, comprising nickel and iron as active cathode materials. Molten NaAlCl4 as secondary electrolyte enables fast transport of ions through the thickness of the cathode. Based on the voltage drop upon cycling, we can show that an ohmic behavior of the internal cell resistance is maintained over a wide range of current densities (up to 80 mA/cm2). We identify separate Ni/NiCl2 and Fe/FeCl2 reaction fronts progressing through the thickness of the cathode as a function of state-of-charge. The mixed Ni/NiCl2 and Fe/FeCl2 cathode can be cycled at 1.6C over a total of 50 cycles (cathode loading 50 mAh/cm2, 10-90% SOC, cumulative capacity 2.1 Ah/cm2). Our study further indicates that combination of a reaction-front mechanism with mixed cathode materials enhances the power capability in high-current pulses.
[1] D. Landmann, G. Graeber, M. V. F. Heinz, S. Haussener, C. Battaglia, Mater.Today Energy, 2020, 18, 100515.
[2] G. Graeber, D. Landmann, M. V. F. Heinz, C. Battaglia, in preparation.
| Speaker Country | Switzerland |
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