Regulating Cation-Solvent Coordination in Carbonate Electrolytes for Low-Temperature and Acid-Resistant Sodium-Ion Batteries

Abstract

Hard carbon (HC) anodes in sodium-ion batteries (SIBs) suffer interfacial instability in conventional carbonate electrolytes. Vinyltrimethylsilane (VTMS) is introduced as a multifunctional additive to stabilize both electrolyte phase and electrode-electrolyte interface layers (EEILs). VTMS scavenges HF and disrupts solvent ordering through dipole-dipole and dipole-ion interactions, lowering Na+ desolvation barriers. Preferential VTMS decomposition affords a robust silicon-rich passivation layer with enhanced interfacial ionic conductivity. Consequently, HC anodes exhibit improved rate capability and cycling stability with Na3V2(PO4)3 (NVP) or NaNi1/3Fe1/3Mn1/3O2 (NFM) cathodes. The HC∥NFM full cell retains 70.7 mAh g–1 after 200 cycles (28 mA g–1) at –20 °C, and a monolayer pouch cell delivers 115.7 mAh g–1 after 200 cycles at room temperature, with 73.4% retention and an energy density of 175 Wh kg–1. This work highlights weak intermolecular interactions in electrolyte engineering and provides a practical strategy for developing SIBs.