Trigger Na+-solvent co-intercalation to achieve high-performance sodium-ion batteries at subzero temperature

Abstract Due to the sluggish interfacial kinetics, the energy density and cycle life of sodium-ion batteries (SIBs) suffer severely at subzero temperatures. Herein, to accelerate the interfacial charge transfer process and improve the low-temperature SIBs performance, a strategy by triggering Na+-solvent co-intercalation is proposed. Using hydrogen titanate nanowires (HT-NW) as a model, we found that the layer structure regulation with oxygen defects could trigger HT-NW presents a unique Na+-solvent co-intercalation behavior in the ether-based electrolyte at -25℃ according to ex-situ FTIR and XRD. By eliminating the Na+ desolvation process, Na+-solvent co-intercalation could effectively accelerate the Na+ diffusion kinetics and reduce the activation energy to 66.0 meV. Benefit from these ameliorations, the defective HT-NW delivers a high capacity of 238 mAh g-1 at -25℃, which is equivalent to 89% of that at 25℃. Besides, the defective HT-NW shows great superiority in cycle stability, maintaining capacity retention of 80.6% after 4200 cycles at 1.0 A g-1 at -25℃. Moreover, at -25°C, the defective HT-NW//Na3V2(PO4)3 full cell exhibits high energy density (119.1 Wh kg-1) and outstanding stability (94.5% after 1000 cycles at 1.0 C). These findings reveal that the ion-solvent co-intercalation is highly feasible to improve the battery performance at low temperatures by accelerating charge transfer kinetics.