Thermodynamics and Electrochemistry of Thermally Regenerative Ammonia Batteries

Abstract

Deep cuts to global carbon emissions are only possible with a dramatic increase in energy storage capacity. However, the cost of the storage options available hinders the timely deployment of the necessary energy storage. Promising supplements to conventional storage are thermally regenerative ammonia batteries (TRABs), which have an additional advantage of being able to capture low-grade waste heat into dispatchable electricity for the grid. This new battery technology can potentially provide power on demand using low-cost chemistries and waste energy sources relative to their purely electric battery counterparts. Most of the research to date for TRABs has been proof-of-concept in nature. As such, little is known about how the electrolytes used in these devices impact their theoretical energy storage capacity. Here we present the general principles of TRABs from an electrochemical and aqueous chemistry perspective. Energy storage density values and Eh-pH diagrams are presented to highlight key factors that govern these complex but versatile energy storage devices. Ag-based and Cu-based TRABs are discussed, and some experimental data confirming the conclusions of the Eh-pH diagrams are presented.