Room-Temperature Flexible Quasi-Solid-State Rechargeable Na–O2 Batteries

Rechargeable Na-O 2 batteries have been regarded as promising energy storage devices because of their high energy density, ultralow overpotential, and abundant resources. Unfortunately, conventional Na-O 2 batteries with a liquid electrolyte often suffer from severe dendrite growth, electrolyte leakage, and potential H 2 O contamination toward the Na metal anode. Here, we report a quasi-solid-state polymer electrolyte (QPE) composed of poly(vinylidene fluoride- co -hexafluoropropylene)-4% SiO 2 -NaClO 4 -tetraethylene glycol dimethyl ether for rechargeable Na-O 2 batteries with high performance. Density functional theory calculations reveal that the fluorocarbon chains of QPE are beneficial for Na + transfer, resulting in a high ionic conductivity of 1.0 mS cm -1 . Finite element method simulations show that the unique nanopore structure and high dielectric constant of QPE can induce a uniform distribution of the electric field during charge/discharge processes, thus achieving a homogeneous deposition of Na without dendrites. Moreover, the nonthrough nanopore structure and hydrophobic behavior resulting from fluorocarbon chains of QPE could effectively protect Na anode from H 2 O erosion. Therefore, the fabricated quasi-solid-state Na-O 2 batteries exhibit an average Coulombic efficiency of up to 97% and negligible voltage decay during 80 cycles at a discharge capacity of 1000 mAh g -1 . As a proof of concept, flexible pouch-type Na-O 2 batteries were assembled, displaying stable electrochemical performance for ∼400 h after being bent from 0 to 360°. This work demonstrates the application of the quasi-solid-state electrolyte for high-performance flexible Na-O 2 batteries.