High-Rate Discharges of Lithium-Ion Batteries for eVTOL Applications

Abstract

Electrical vertical takeoff and landing (eVTOL) aircraft require batteries that deliver both high energy density and high specific power, a combination that current lithium-ion systems do not fully achieve. We evaluated Li-ion cells under high-rate discharge conditions using two electrolyte systems: a conventional Gen-2 (LiPF₆-based) formulation and a LiFSI (LiN(SO₂F)₂)-based electrolyte. Galvanostatic cycling shows that LiFSI significantly improves power delivery, reversibility, and cathode stability under extreme fast charging (XFC) compared to Gen-2.Reduced electrode loading further enhances power capability but shortens cycle life. Extended cycling reveals previously unreported current collector corrosion in LiFSI-based cells, indicating new degradation pathways critical for high-power operation. Post-mortem analyses using scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), two-dimensional X-ray absorption near-edge spectroscopy (2D-XANES), X-ray diffraction (XRD), and transmission X-ray microscopy (TXM) confirm structural and chemical changes at the cathode-electrolyte interface.These results demonstrate the key role of electrolyte formulation in enabling Li-ion batteries for eVTOL applications and define degradation mechanisms that must be mitigated for high-power and long-life operation. Despite the improvements achieved with LiFSI-based electrolytes, the newly identified corrosion underscores the remaining challenges that must be resolved before practical deployment.