Isotropous Sulfurized Polyacrylonitrile Interlayer with Homogeneous Na~+ Flux Dynamics for Solid-State Na Metal Batteries

摘要

Inorganic solid-state electrolyte (SSE) based Na-metal batteries have received extensive attention in next-generation lithium-free energy storage systems with both high-security and superior electrochemical performance. Herein, in contrast to the conventionally used polymer/ceramic/polymer sandwich electrolyte, an efficient green and scalable powder-polishing synthetic method is developed to fabricate a pyrolyzed-polyacrylonitrile modified Na super ionic conductor (NASICON) electrolyte to relieve polarization of integrated composite SSE and ameliorate interfacial contact between the electrolyte and the Na anode. Furthermore, introducing S in the preferable isotropous sulfurized polyacrylonitrile (SPAN) interlayer can trigger dehydrogenation and cyclization of polyacrylonitrile with chemically-bonded short-chain S-S segments, which can bond with Na+ to redistribute the interfacial electric field and homogenize transported Na+ flux, leading to transition of Na deposition behavior from dendrite growth mode to lateral flat-shape growth tendency. The conjugated polymer backbones possess delocalized radicals that can activate formed short-chain sulfides to reconnect to the backbones, thus maintaining superior structural stability. Benefiting from the rational interfacial design, a record-high value of 1.4 mA cm(-2) for critical current density of Na/SPAN-NASICON/Na cells is obtained. Moreover, SPAN is used as a cathode to assemble solid-state Na/SPAN-NASICON/SPAN Na-organosulfur batteries, demonstrating superior capacity and cycling-stability. The rational SPAN-based structural design strategy may provide an avenue for potential application of solid-state alkali metal batteries.