Rational Formulation of Ether‐Lactone Electrolytes for Safe and Sustainable Ni‐Rich Lithium‐Ion Batteries

This study reports the formulation of innovative electrolytes designed to improve safety, sustainability, and compatibility with LiNi0.92Mn0.04Co0.04O2 (NMC92) cathodes. The use of bio-based solvents (γ-valerolactone, GVL) and safe, stable, innovative co-solvents (diethylene glycol butyl ethyl ether, DEGBEE) is investigated in combination with imide- and borate-based salts, demonstrating reduced flammability and enhanced transport properties. Molecular dynamics simulations reveal their advantageous solvation characteristics, highlighting increased lithium-ion mobility in GVL-based electrolytes due to diminished ionic clustering. Overall, the investigated electrolytes exhibit outstanding electrochemical performance with NMC92 cathodes in a half-cell configuration, retaining above 80% of their initial capacity after 300 galvanostatic cycles at 1 C and an enhanced rate capability. This behavior is attributed to the inorganic nature of the resulting cathode-electrolyte interphase, as confirmed by ex situ x-ray photoelectron spectroscopy. Finally, the suitability of this novel formulation for real-scale application is evaluated at the pouch-cell level, demonstrating similar performance to benchmark formulations while enhancing overall device safety and sustainability.