PVDF–HFP@Nafion-based quasisolid polymer electrolyte for high migration number in working rechargeable Na–O2 batteries

Rechargeable sodium-oxygen (Na–O2) battery is deemed as a promising high-energy storage device due to the abundant sodium resources and high theoretical energy density (1,108 Wh kg–1). A series of quasisolid electrolytes are constantly being designed to restrain the dendrites growth, the volatile and leaking risks of liquid electrolytes due to the open system of Na–O2 batteries. However, the ticklish problem about low operating current density for quasisolid electrolytes still hasn’t been conquered. Herein, we report a rechargeable Na–O2 battery with polyvinylidene fluoride-hexafluoropropylene recombination Nafion (PVDF–HFP@Nafion) based quasisolid polymer electrolyte (QPE) and MXene-based Na anode with gradient sodiophilic structure (M-GSS/Na). QPE displays good flame resistance, locking liquid and hydrophobic properties. The introduction of Nafion can lead to a high Na+ migration number (tNa+ = 0.68) by blocking the motion of anion and promote the formation of NaF-rich solid electrolyte interphase, resulting in excellent cycling stability at relatively high current density under quasisolid environment. In the meantime, the M-GSS/Na anode exhibits excellent dendrite inhibition ability and cycling stability. Therefore, with the synergistic effect of QPE and M-GSS/Na, constructed Na–O2 batteries run more stably and exhibit a low potential gap (0.166 V) after an initial 80 cycles at 1,000 mA g–1 and 1,000 mAh g–1. This work provides the reference basis for building quasisolid state Na–O2 batteries with long-term cycling stability.