An Organic Redox Flow Cell-Inspired Paper-Based Primary Battery.

A portable paper-based organic redox flow primary battery using sustainable quinone chemistry is presented. The compact prototype relies on the capillary forces of the paper matrix to develop a quasi-steady flow of the reactants through a pair of porous carbon electrodes without the need of external pumps. Co-laminar capillary flow allows operation Under mixed-media conditions, in which an alkaline anolyte and an acidic catholyte are employed. This feature enables higher electrochemical cell voltages during discharge operation and the utilization of a wider range of available species and electrolytes and provides the advantage to form a neutral or near-neutral pH as the electrolytes neutralize at the absorbent pad, which allows a safe disposal after use. The effects of the device design parameters have been studied to enhance battery features such as power output, operational time, and fuel utilization. The device achieves a faradaic efficiency of up to 98 %, which is the highest reported in a capillary-based electrochemical power source, as well as a cell capacity of up to 11.4 Ah L-1  cm-2 , comparable to state-of-the-art large-scale redox flow cells.