The poor safety behavior of Li-ion batteries necessitates complex charge electronics, elaborate thermal management and suitable mechanical reinforcements.  These would result in reduced system-level energy densities, compared to the cell-level values, and also higher battery costs.  In contrast, the aqueous systems, especially the metal-air systems that can provide high specific energies and energy densities look more appealing due to their inherent safety. Under an ARPA-E sponsored program, we (JPL, Caltech and Liox) are developing low cost and safe rechargeable metal-hydride/air batteries with high energy densities (200 Wh/kg and 400 Wh/l at cell level) for electric vehicle applications.  Our effort is focused on developing: i) new metal hydride alloys with higher hydrogen absorption capacities, ii) stable low-cost electro-catalysts for air cathodes, iii) new cell and stack designs and iv) simpler water management schemes.

We have been developing metal hydride alloys of vanadium-based quaternary BCC alloys (Ti-V-Ni-Cr) as anode materials, low-cost perovskite-based and Ni-Fe-Co layered double hydroxide catalysts for oxygen electrodes, and cell and system designs that minimize thermal and concentration gradients.  In this paper, we will describe some of our recent results on this technology.