Scalable SPAN Membrane Cathode with High Conductivity and Hierarchically Porous Framework for Enhanced Ion Transfer and Cycling Stability in Li–S Batteries

Lithium sulfur batteries with a high energy density of 2600 Wh kg–1 and theoretical specific capacity of 1675 mAh g–1 have been regarded as the most promising candidate for the next generation of high-energy storage devices. However, their commercial application is hindered by the undesirable troubles of rapid capacity fading, insulation of the products (Li2S/Li2S2), volume expansion, and low mass loading. Herein, a three-dimensional holey CNT/sulfurized polyacrylonitrile (CNT@SPAN) freestanding cathode has been fabricated by a one-step phase inversion method, followed by sulfurization without any binders and current collectors. The unique porous framework design with SPAN in situ encapsulating CNT can effectively facilitate the transportation of ions and electrons, and endure the volume expansion of sulfur during the reaction process. Simultaneously, by combining electrochemical impedance analysis and frontier molecular orbit theory, the initial activation mechanism of the Li-SPAN battery was explored. In the initial state of cell activation, Li+ occupies the carbon skeleton continuously and irreversibly, which enhances the conductivity of the composites. This work refreshes the current performance of Li-SPAN batteries with a maximum areal capacity of 10.21 mAh cm–2 at an ultrahigh mass loading of 7.5 mg cm–2, and an excellent rate capacity of 761.7 mAh g–1 at 4 C, which provides a promising method to make Li–S batteries to meet the requirements of commercial application.