The Lunar Flow Battery (LFB) is a scalable, long-duration energy storage solution featuring minimum capacity fade over many cycles that uses electrolytes derived from lunar regolith to minimize launch mass. The LFB operates by storing two separate solutions of redox-active species which are pumped past the cathode and anode respectively to produce a current. By pumping the redox-active fluids across the electrodes, the energy and power can be scaled independently. What makes the LFB distinct from other flow batteries is its use of locally available resources to produce the electrolyte solutions, thereby reducing the launch mass. Lunar-sourced iron, titanium, sulfur, oxygen, and water provide the bulk electrolyte solutions while the more sophisticated components such as membranes, pumps, and electrodes are transported from Earth. Compared to alternatives such as Li-ion batteries, the LFB has vastly superior cycle life and the energy storage is readily scalable, making it an ideal solution for long-term, stationary storage over the lunar day/night cycle. By using locally available materials to produce the redox-active species and with no need for replacement cells for dozens of years, the energy storage capacity is high relative to the total launched mass. The Phase I program will investigate the selective dissolution of ilmenite (FeTiO3), an ore available in high concentrations in lunar mare basalts, using sulfuric acid to produce iron and titanium sulfate electrolyte solutions and incorporate these solutions into a functional redox flow cell. This cell will be cycle tested to quantify its performance with regards to capacity fade and specific energy while any operational issues or degradation pathways will be addressed.
The principal future application of the LFB is to provide long-duration energy storage for a permanent lunar base. The LFB is ideally suited for such a remote outpost with long day/night cycles where locally available resources can provide the basic materials to produce a large-scale energy storage system with a lower launch mass than alternatives. This system could be scaled up or multiplied to provide power to any number of long-duration scientific platforms, human habitats, and ISRU processing systems.
The LFB technology could provide an alternative solution for large-scale remote storage where access to resources is limited. Alternatively, the development of sulfuric acid processing of mixed metal oxides could provide an improved method for the production and recycling of titanium dioxide as a pigment for the coatings industry, opening up ilmenite deposits for cheaper TiO2 production.