Are Liquid Batteries the Solution for Electric Aircraft?

As aircraft technology continues to improve throughout the years, obtaining the realization of fully electric aircraft seems to be closer than ever. As compared to standard fuel powering, electricity poses a much more economically feasible method of producing aircraft propulsion. Electric aircraft also present the capabilities of creating air taxis, silent airliners, and other technologies that would greatly improve our aviation capabilities. To move closer to the goal of electric aircraft, one major obstacle that must first be overcome is our limitation in battery technology. Typically, current batteries are unable to meet needed power to weight ratios and costs that would make them a feasible choice.

In the present, companies such as Tesla are constantly working to improve automobile batteries, and they are constantly pushing the limits ever further with each subsequent technological release. Despite this, the provided power of these batteries are still not enough for aircraft. Furthermore, many automobile batteries are designed to be as compact as possible, which is not a problem for aircraft. In general, the main concern for aircraft powering is weight, which makes energy density the prime characteristic that would need to be improved upon. According to research, a liquid battery that could provide 1,000 Wh/kg would be optimal for smaller aircraft, though this technology seems to be out of reach currently.

One solution to the electric aircraft battery problem may come from research being conducted by NASA for the nanoelectrofuel flow (NEF) battery. NEF batteries may serve as efficient aircraft rechargeable batteries, providing rim-driven electric motors which would aid in clean and quiet thrust generation to provide for flight. The NEF battery may be useful for aircraft that are smaller in size and unmanned, but results conducted by researchers have not been as promising as is desired currently.

Nevertheless, other types of rechargeable batteries are under research and could prove useful. Researchers at the Argonne National Laboratory and Illinois Institute of Technology, Influit Energy have produced aircraft rechargeable batteries that have active energy-storing materials that are in a liquid form. This type of liquid battery would allow operators to use them similarly to gasoline powered engines. According to Influit Energy, their NEF battery would be capable of producing energy with one and a half times the energy density of a conventional lithium-ion battery, all while operating at half of the cost. Such aircraft rechargeable batteries would also prove to be very versatile, allowing for a variety of shapes that may fit different aircraft needs. To recharge the battery, liquids would be pumped into storage tanks and could allow for recharging of the grid to achieve load balance.

Across many types of rechargeable batteries that are currently used for aircraft, the amount of active materials within the cell is typically around 35%. The remaining materials are then materials such as casings, binders, separators, and more. The NEF battery that is proposed and researched by Influit has 60% of the cell materials as active materials. The NEF battery from Influit would have positively and negatively charged fluids that are water based. Infused within the fluids, nanoparticles of active materials create an electrolyte that can be recharged many times as needed after energy is spent.

In 2018, a presentation at the American Institute of Aeronautics and Astronautics Aviation conference in Atlanta was conducted by NASA electrical engineer Kurt Papathakis in which a NEF battery technology roadmap was proposed. In this presentation, NEF batteries were stated to be able to surpass the pack-level energy density of lithium-ion by over two times in the foreseeable future. Beyond this, NASA claimed that with funding, they would be able to produce first generation NEF batteries that are capable of a current density of 100 mA/cm2. This first generation NEF battery would be set to surpass lithium-ion in performance.

The NASA electrical engineer further explained that through industry cost sharing, batteries could be improved upon to the point of reaching aircraft rechargeable batteries with 750 Wh/kg by 2023. To discharge active materials within such batteries, fluids may be pumped throughout the flow cell numerous times. Greenhouse gases could even be eliminated with battery charging using solar and wind power. The last major consideration for NEF battery technology that was suggested was the fact that such batteries would be able to be recharged through multiple cycles without degradation. As compared to Lithium-ion batteries, the NEF battery would not have cycle life penalties if it was over charged or discharged too greatly.

Beyond the NEF battery, there is also a feasible option that may come in the form of a lithium-metal battery. These types of rechargeable batteries are proposed to be the next step in aircraft battery technology, and it is suggested that they would open the doors to other materials, such as oxygen and sulfur. A battery proposal called a “lithium-air battery” may be capable of featuring an energy density equating to 400 Wh/kg, opening up many opportunities of long distance flight.

Across all aircraft electric battery proposals, the main concern remains weight. Other voiced concerns also bring up a desired community effort, as some believe that syncing market forces will make it much easier to achieve breakthroughs in technology. Luckily, the realization of such battery technology seems to be ever closer, and current research continues to be a promising step forward.

When it comes time to begin sourcing the aircraft rechargeable batteries and other aerospace hardware that you need for your next project or operation, Aviation Orbit has you covered with everything you are searching for. Aviation Orbit is owned and operated by ASAP Semiconductor, and we can help you find the aircraft, marine, and IT parts that you are searching for, new or obsolete. As a premier supplier of parts for the aerospace, civil aviation, and defense industries, we're always available and ready to help you find all the parts and equipment you need, 24/7x365. ASAP Semiconductor is an AS9120B, ISO 9001:2015, and FAA AC 0056B Accredited enterprise. For a quick and competitive quote, email us at or call us at +1-509-449-7700.


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