Britain’s OXIS Energy is teamed up with the American-Brazilian aircraft manufacturer Texas Aircraft to develop a sleek and stylish, high-wing, all-metal, fully electric aircraft. The eColt should be able to fly for 2 hours on a single charge and reach an approximate range of 200NM (230-mile), figures that stand out for such an early phase of use for the sulfur ion. The aircraft will have a comfortable two-seat cabin.
The two-seater will be particularly dedicated to filling a growing demand for ecologically-friendly flight training, as well as regional transportation in Brazil and throughout the world. The 90 kWh battery pack that OXIS Energy has developed for the eColt is 40% lighter than current Li-Ion technology and will be powered by its “High Power” cell at 400Wh/kg.
OXIS Energy is one of the most promising battery development companies. The company has been developing promising lithium-sulfur batteries since 2004 that is a possible alternative to current lithium-ion batteries thanks to their high energy density. In addition, sulfur is very abundant in nature, environmentally friendly, and is also very inexpensive, so the production cost will be cheaper than lithium batteries.
With lithium-sulfur cells, degradation of the lithium-metal anode is a problem. In an article published in IEEE Spectrum, Mark Crittenden, the head of battery development and integration at OXIS Energy, details that their technology involves coating the lithium-metal anode with thin layers of ceramic materials to prevent degradation. Such ceramic materials need to have high ionic conductivity and be electrically insulating, as well as mechanically and chemically robust.
One more challenging thing is the energy density, which doesn’t translate directly from the cell to the battery because cells require packaging – the case. If the packaging is done right, the energy density of the battery can be held to 80% of that of the cells. This means if a cell rated at 450 Wh/kg can be packaged at more than 360 Wh/kg in the final battery. However, the OXIS team expects to do better by integrating the battery into the aircraft, for instance, by making the wing space do double duty as the battery housing. It can maintain 90% of the cell density.
“Typical lithium-ion designs can hold from 100 to 265 Wh/kg, depending on the other performance characteristics for which it has been optimized, such as peak power or long life,” he writes. The latest OXIS Li-S battery cell prototypes have managed to reach 450 Wh/kg, and they expect to reach 500 Wh/kg within a year. “And as the technology is still new and has room for improvement, it’s not unreasonable to anticipate 600 Wh/kg by 2025.”
The use of Sulfur as a non-conductive material provides enhanced safety and is superior to current Lithium-Ion technology. Free from the high polluting effects of the lead-based fuel used in aircraft today, the all-electric Texas Aircraft eColt will provide an efficient, clean mechanism for new pilots whilst decreasing training costs substantially.
Not everything is so beautiful in the Li-S battery cells, since the problem that continues to arise as the most important is the useful life of the battery itself, and OXIS Energy would be working so that its lithium-sulfur batteries could reach the 500 charge and discharge cycles, and although we are dealing with batteries that thanks to a greater autonomy should be recharged proportionally less during their useful life, it is still a challenge for OXIS Energy.