High Energy Batteries for UAVs

Li-ion batteries have been a key enabler for unmanned aircraft over the past decade, but progress has stalled. When the Solar Impulse II aircraft flew around the world in 2016 using only solar cells and batteries, it used the highest performing Li-ion batteries on the market with a cell-level energy density of 261 whr/kg. Nearly 5 years later, the best Li-ion batteries on the market have experienced little improvement in energy density. In the phase I effort, the team determined that Lithium-Metal technology represented the next major leap for lithium-based batteries, but their short lifespan combined with their requirement for high mechanical compression and a thermally conductive interface results in mediocre module-level energy density that is not much better than Lithium-ion. The focus of the phase II effort is to overcome the challenges of packing factor and lifespan by developing a next-generation lithium-metal battery module that cuts packing factor from 30% down to 10% and cuts the loss of energy capacity at 90 cycles from 20% down to 10%. These improvements will have significant impact the performance and payload capacity of solar-electric aircraft.