High‐Performance Mg–O2 Batteries Enabled by Electrospinning PVDF‐HFP‐Based Quasi‐Solid‐State Polymer Electrolyte

Abstract

This article reports a high‐performance rechargeable battery enabled by an electrospun quasi‐solid‐state electrolyte (E‐QSSE). The E‐QSSE, composed of Poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP), Mg(NO3)2 salt, and Pyr14TFSI ionic liquid (IL), exhibits high Mg2+ ion transport and interfacial stability. A unique sandwich structure coupling the E‐QSSE with a Ruthenium nanoparticles decorated multi‐walled carbon nanotubes (Ru/CNT) cathode catalyst on carbon paper significantly augments electrochemical reversibility. The optimized E‐QSSE with a 1:1 molar ratio of salt and IL achieves a high room temperature ionic conductivity of 6.39 mS cm−1. The E‐QSSE's electrochemical stability window extends up to 3.95 V, showcasing its potential for high‐energy‐density applications. The Mg‐O2 cell, with the optimized E‐QSSE, delivers 115 discharge/charge cycles at 100 mA g−1, one of the longest reported cycle‐lives for secondary Mg‐O2 batteries. The battery exhibits a maximum discharge capacity of 9305 mAh g−1 with 100% Coulombic efficiency. X‐ray photoelectron spectroscopy and absorption near‐edge structure analyses reveal MgO as the primary discharge product, with MgF2 contributing to stable solid electrolyte interphase. This E‐QSSE design promotes efficient Mg2+ ion migration and stable electrochemical reactions. This work advances the development of stable, high‐capacity Mg‐O2 batteries and can open up avenues for quasi‐solid‐state electrolytes in post‐lithium metal‐air battery technologies.