Moderate Solvation Structure Design Endows Long Cycling of 5 V-Class Fast-Charging Lithium-Ion Batteries

LiNi0.5Mn1.5O4 (LNMO) cathode attracts great attention due to its low cost, good air stability, and three-dimensional lithium-diffusion channels. However, the operation voltage of LNMO (∼5 V vs Li+/Li) exceeds the oxidative limitation of most electrolytes, hindering the application of LNMO batteries. Fluorinated carbonate-based electrolytes can partially solve the oxidation challenge, but excessive viscosity and poor solvation ability cause the sluggish transport of Li+. Here we report a moderate solvation electrolyte design using 2,2,2-trifluoroethyl acetate (EA3F) as the main solvent to stabilize LNMO cathodes under fast charging conditions. EA3F not only shows moderate Li+ coordination that can promote fast desolvation, but also facilitates the formation of thin and robust interphases at cathode/anode electrodes. Consequently, the 1.4 Ah graphite||LNMO pouch cells with this electrolyte can achieve 80% capacity retention over 1200 cycles at 1 C and release ∼90% capacity retention at a rate of 4 C (9.4 mA cm–2).