OXIS Energy, Bye Aerospace Develop Lithium-Sulfur Cells

Diane Simard, Senior Vice President and a member of the Board of Directors for Bye Aerospace, sends your editor occasional news from that company.  The latest involves a collaboration with OXIS Energy in England to develop new Lithium-Sulfur battery cell technology that shows great, and (even better) near-term promise.

Ready to start in September, the project will develop cells that will, ”Achieve the higher energy density required for such aircraft,” referring to Bye’s eFlyer 2 and eFlyer 4 light aircraft.  A big jump over currently available batteries, OXIS is now evaluating cells that produce 400 Watt-hours per kilogram, with a promised leap to 500 kW-hr by next year.  The best lithium-ion cells at the pack level available now manage 260 W-hr/kg.

Huw W. Hampson-Jones, CEO of OXIS Energy, discusses his company’s unique approach to battery development and what this portends for future flight and general electric mobility.  Explaining OXIS’s applications, he adds, “Aviation is one of OXIS’ target markets, and in the first instance, Regional Rapid Air Taxi Transportation. A key measure of OXIS’ suitability is to be able to consistently produce cells in excess of 400 Wh/kg, which are already undergoing evaluation. OXIS expects to achieve 500 Wh/kg by early 2020. Our Li-S cells and battery systems are ideally suited for aviation. They are over 50-percent lighter than the current Li-ion cell and battery systems, with the winning formula of a high energy cell at the power required. The use of the same cell format across batteries will also help our customers to minimize cost and improve serviceability.”

Consisting of a lithium metal anode, a sulfur-based cathode, a safe electrolyte protecting the lithium metal, and a “state of the art” separator, the cells have the advantage of allowing full depth of discharge (DOD).  This gives a 20-percent endurance advantage over Li-ion cells.

Structure of lithium-sulfur cell

An available and “already proven” pouch cell provides 2.1 nominal Volts at a typical capacity of 10 to 35 Amp-hours.  OXIS will make the pouches in two versions: One disadvantage might be the 100 charge-discharge cycles (full DOD?) available from the pouches.  That might make them a little pricey.  We might assume (always dangerous) that cell life will improve with further development.

  • High energy density cell (>500 Wh/kg) for small electric aircrafts (2 seater), UAV and High Altitude Pseudo Satellite (HAPS).
  • High power cell (>400 Wh/kg) for automotive applications and electric Vertical Take Off and Landing (eVTOL) aircraft.

George Bye, CEO of Bye Aerospace, said, “New Li-S battery cells from Oxis have the potential to greatly enhance the quality, cost and performance of eFlyer 4 and our other future aircraft projects. Our collaboration with OXIS is separate from the current eFlyer 2 agreements and intentions we have with confirmed and our future supply chain partners.  Bye Aerospace is working with Oxis on the Li-S battery cell characteristics to significantly improve our eFlyer 4 and future air taxi aircraft designs’ performance.  The average age of the global market for Turboprop fleet is 28 years. OXIS has the potential to provide a Li-S battery cell that is truly a game-changer.”

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