Quantification of solvent-mediated host-ion interaction in graphite intercalation compounds for extreme-condition Li-ion batteries

Abstract

Achieving simultaneous fast-charging capabilities and low-temperature adaptability in graphite-based lithium-ion batteries (LIBs) with an acceptable cycle life remains challenging. Herein, an ether-based electrolyte with temperature-adaptive Li⁺ solvation structure is designed for graphite, and stable Li⁺/solvent co-intercalation has been achieved at subzero. As revealed by in-situ variable temperature (−20 °C) X-ray diffraction (XRD), the poor compatibility of graphite in ether-based electrolyte at 25 °C is mainly due to the continuous electrolyte decomposition and the in-plane rearrangement below 0.5 V. Former results in a significant irreversible capacity, while latter maintains graphite in a prolonged state of extreme expansion, ultimately leading to its exfoliation and failure. In contrast, low temperature triggers the rearrangement of Li⁺ solvation structure with stronger Li⁺/solvent binding energy and shorter Li⁺–O bond length, which is conducive for reversible Li⁺/solvent co-intercalation and reducing the time of graphite in an extreme expansion state. In addition, the co-intercalation of solvents minimizes the interaction between Li-ions and host graphite, endowing graphite with fast diffusion kinetics. As expected, the graphite anode delivers about 84% of the capacity at room temperature at −20 °C. Moreover, within 6 min, about 83%, 73%, and 43% of the capacity could be charged at 25, −20, and −40 °C, respectively.