3D nickel electrodes for hybrid battery and electrolysis devices

Abstract

A renewable power-based energy system will require both short- and long-term electricity storage and conversion to hydrogen-based fuels. This study investigates 3D electrodes for an integrated alkaline Ni-Fe battery and electrolyzer. The dual system can sustain current densities similar to those in alkaline electrolyzers while simultaneously reaching efficient hour-duration battery-storage capacities. We demonstrate that the combination of microporosity and a conductive three-dimensional (3D) electrode design with macroscopic channels enables the required current densities during charge, electrolysis, and discharge. The ionic conduction in the 3D electrode enables higher utilization of the active electrode mass and lower overpotentials during both the (dis)charge reaction and electrolysis. The double function of these electrodes is understood from a general statistical model and a more detailed porous-electrode model perspective. The 3D structuring provides a pathway forward, accessible with industrially established techniques, to these higher-power and higher-energy-density electrodes.