Quantification of Charge Transport and Mass Deprivation in Solid Electrolyte Interphase for Kinetically-Stable...

Graphite (Gr)-based lithium-ion batteries with admirable electrochemical performance below -20 °C are desired but are hindered by sluggish interfacial charge transport and desolvation process. Li salt dissociation via Li⁺-solvent interaction enables mobile Li⁺ liberation and contributes to bulk ion transport, while is contradictory to fast interfacial desolvation. Designing kinetically-stable solid electrolyte interphase (SEI) without compromising strong Li⁺-solvent interaction is expected to compatibly improve interfacial charge transport and desolvation kinetics. However, the relationship between physicochemical features and temperature-dependent kinetics properties of SEI remains vague. Herein, we propose four key thermodynamics parameters of SEI potentially influencing low-temperature electrochemistry, including electron work function, Li⁺ transfer barrier, surface energy, and desolvation energy. Based on the above parameters, we further define a novel descriptor, separation factor of SEI (S_SEI), to quantitatively depict charge (Li⁺/e^-) transport and solvent deprivation processes at Gr/electrolyte interface. A Li₃PO₄-based, inorganics-enriched SEI derived by Li difluorophosphate (LiDFP) additive exhibits the highest S_SEI (4.89×10³) to enable efficient Li⁺ conduction, e^- blocking and rapid desolvation, and as a result, much suppressed Li-metal precipitation, electrolyte decomposition and Gr sheets exfoliation, thus improving low-temperature battery performances. Overall, our work originally provides visualized guides to improve low-temperature reaction kinetics/thermodynamics by constructing desirable SEI chemistry.