Fabrication of a necklace-like fiber separator by the electrospinning technique for high electrochemical performance and safe lithium metal batteries

Abstract

Lithium (Li) metal batteries, as the ultimate goal of high energy density storage devices, have been regarded as a suitable candidate for next-generation electrical energy storage. Nevertheless, uncontrolled lithium dendrites produced by cycling processes can trigger a series of safety issues and limit the large-scale practical application of Li metal batteries. Herein, inspired by the highly designable necklace-like structure of fibers, a high Young-modulus polyvinyl alcohol@silica composite separator with a necklace-like structure prepared by electrospinning has been advocated, which exhibits excellent electrolyte wettability, ionic conductivity and thermal shrinkage properties. Besides, the advanced separator employing the LiFePO₄//Li full cell also delivers excellent cycling and rate performance with superior discharge capacity and lower polarization. Significantly, the as-prepared separator shows extraordinary capability inhibiting notorious lithium dendrites through the “three lines of defense”, reflecting a satisfactory Coulombic efficiency of 91.77% after 100 cycles in an ester electrolyte without film-forming additives at 1.0 mA cm⁻² for 1 h. Moreover, the symmetric lithium cell with the advanced separator can stably run with low over-potential at 2.0 mA cm⁻² over 1900 h. Thus, this work indicates that the designed composite separator could be a potential candidate to promote the practical application of lithium metal batteries.