In‐situ growth of ultrathin sulfur microcrystal on MXene‐based 3D matrice for flexible lithium–sulfur batteries

Abstract

Abstract Lithium–sulfur batteries (Li‐S batteries) are promising next‐generation energy storage systems because of their high‐theoretical energy density. However, the commercialization of Li‐S batteries is still impeded by the aggregation of sulfur, low‐sulfur utilization, shuttling of dissolved polysulfides and sluggish reaction kinetics. Herein, we designed a hierarchically maple leaf‐like structured sulfur electrodes by in‐situ growth of ultrathin sulfur microcrystal on two‐dimensional MXene‐graphene‐cellulose nanofiber (MGN) matrice (denoted as IS‐MGN@S). The sulfur microcrystal as cathode can achieve improved kinetics than bulk sulfur due to its few layers of sulfur atoms, which is proved by the density functional theory calculations. The MXene not only confines polysulfides through strong chemisorption but also promotes the catalytic conversion of polysulfides. The introduction of graphene improves the conductivity and boosts the immobilization and conversion of polysulfides. As a result, the IS‐MGN@S cathode demonstrates remarkable electrochemical properties with a high‐initial capacity (1229 mAh g−1 at 0.2C), substantial improvement in rate capability (770 mAh g−1 at 2C), and stable long‐term cycling capacity. Moreover, the pouch cells with IS‐MGN@S cathode and gel electrolyte demonstrate excellent mechanical properties under mechanical damage (nail & cut tests, severe deformations), suggesting their promising applications for wearable electronic devices.

Keywords

• density functional theory
• flexible Li‐S batteries
• in‐situ optical microscopy
• real‐time observation
• sulfur crystal evolution