Tailoring Weakly Coordinating Electrolytes via Orbital-Overlap-Enhanced Dipole-dipole Interactions for Low-Temperature Lithium-Ion Batteries.

Abstract

Lithium-ion batteries (LIBs) suffer rapid capacity fade at low temperatures. Weakly coordinating electrolytes via adding low-polarity or non-coordinating co-solvents (such as fluorinated ethers) have shown promise in rapid desolvation, yet these electrolytes often exhibit low ionic conductivity at low temperature, limiting the application of high-energy density LIBs. Here, we design a weakly coordinating electrolyte by incorporating the non-coordinating co-solvent (pentafluoroethyl)trimethylsilane (PFTMS) into the coordinating solvent diethyl carbonate (DEC) via orbital-overlap-enhanced dipole-dipole interactions. The slight Si─O orbital overlap drives strong dipole-dipole interactions between PFTMS and DEC. This interaction lowers the negative electrostatic potential at the carbonyl oxygen of DEC, thereby weakening Li⁺-DEC coordination. Thus, by leveraging enhanced dipole-dipole interactions, this strategy realizes a weak Li⁺-solvent coordination through a lower content of PFTMS (10 vol%) compared to traditional fluorinated solvents. Besides, the designed electrolyte delivers sufficient ionic conductivity of 1.56 mS cm^-1 at -40°C. Accordingly, the graphite || LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) coin cell shows reversible capacity of 156.5mAh g^-1 at -40°C. Notably, 4.7 Ah graphite || NCM811 pouch cell also demonstrates 219.8 Wh kg^-1 at -20°C. This work advances the design of traditional weakly coordinating electrolytes via an orbital overlap strategy, which paves the way for application in extreme environments.