A high-power battery that stays strong for a long flight duration

Drawing inspiration from biology, a group of scientists and engineers has developed and trialed an electrolyte that sustains high battery power output over multiple cycles. A breakthrough in battery component design could ensure that electric aircraft can maintain high power output even when landing with low charge, as indicated in a recent study conducted by Lawrence Berkeley National Laboratory in collaboration with the University of Michigan.

This research presents a resolution to a problem that was first identified in a 2018 study led by Venkat Viswanathan, a professor of aerospace engineering at U-M and one of the co-authors of the new research published in Joule.

“Both takeoff and landing require high power, and landing is more challenging because you’re not fully charged,” Viswanathan said. “To get high power, you have to bring all the resistances down. Anything that affects the ability to deliver that power.”

The team made it clear that this differs from the requirements of EV batteries, which primarily focus on maintaining their ranges.

“In an electric vehicle, you focus on capacity fade over time,” said study lead author Youngmin Ko, a postdoctoral researcher at Berkeley Lab’s Molecular Foundry. “But for aircraft, it’s the power fade that’s critical – the ability to consistently achieve high power for takeoff and landing.”

Capacity fades, and power fades typically manifest when lithium ions encounter difficulty moving in and out of the electrodes.

Capacity fade is primarily influenced by the quantity of lithium ions capable of moving between the electrodes, while the key factor for power fade is the speed of ion movement. The issue arises from the accumulation of corrosion on the electrodes, which occupies space that could have been used by lithium ions, making it more challenging for lithium to access available spaces.

Led by Brett Helms, who is the corresponding author of the study and a senior staff scientist at Berkeley Lab’s Molecular Foundry, the team investigated the interactions between the electrodes and electrolyte by adopting an approach from biology.

In biological studies, “omics” is the field that seeks insights into the components of cells—such as which genes are being expressed and which proteins are being produced. The team delved into different electrolyte chemistries, observing subtle changes occurring within the electrolyte at various points in the battery during the charge and discharge processes.

Previous research has commonly linked power degradation to issues occurring at the negative end of the battery since lithium metal is highly reactive.

In this instance, the researchers noticed that harmful compounds were developing close to the positive terminal, specifically nickel-manganese-cobalt oxide. Interaction with these compounds led to the positive electrode particles deteriorating and breaking down over time, which impeded the lithium movement and decreased power output.

“It was a non-obvious outcome,” Ko said. “We found that mixing salts in the electrolyte could suppress the reactivity of typically reactive species, which formed a stabilizing, corrosion-resistant coating.”

The company 24M subsequently constructed a testing facility using this particular chemistry and dispatched it to And Battery Aero, a startup co-founded by Viswanathan with his former Ph.D. student Shashank Sripad, who is also a co-author of this study and the 2018 study.

Sripad conducted tests on the cell by repeatedly extracting power from it in a realistic series of takeoff, flight, and landing, simulating the cell as part of a complete battery module powering an electric aircraft. When compared to traditional batteries, the new cell maintained the necessary power-to-energy ratio for electric flight for four times longer.

“Heavy transport sectors, including aviation, have been underexplored in terms of electrification,” Helms said. “Our work redefines what’s possible, pushing the boundaries of battery technology to enable deeper decarbonization.”

The complete battery will be constructed by 24M, and it will be tested by Battery Aero on a propeller stand by repeatedly running the propeller through the flight sequence. The team aims to conduct an electric flight test using these batteries next year.

Scientists at the University of California, Berkeley, are also part of the team and plan to broaden the application of omics in battery research. They will investigate the interactions of different electrolyte components to gain a better understanding and customize battery performance for current and future applications in transportation and the grid.

Journal reference:

1. Youngmin Ko, Michael A. Baird, Xinxing Peng, Tofunmi Ogunfunmi, Young-Woon Byeon, Liana M. Klivansky, Haegyeom Kim, Mary C. Scott, John Chen, Anthony J. D’Angelo, Junzheng Chen, Shashank Sripad, Venkatasubramanian Viswanathan, Brett A. Helms. Omics-enabled understanding of electric aircraft battery electrolytes. Joule, 2024; DOI: 10.1016/j.joule.2024.05.013