Hierarchically Porous and Interconnected Ti3c2t X Mxene Networks Via Interface-Directed Functionalization for Lithium-Sulfur Batteries

Abstract

2D transition metal carbides/nitrides, MXenes, have emerged as promising materials for energy storage but significant technological challenge still remains in designing optimal composite electrodes for redox-type batteries for efficient electron and ion transport, buffered volume changes, and polar surface characteristics. We present 3D-interconnected, hierarchically porous Ti3C2Tx MXene networks, enabled by solution-phase interface-directed functionalization and the self-organization of water droplets. Rational control of MXene flakes wettability through solution phase functionalization unfolds large tunability of MXene assembled structure, successfully addressing key design requirements for lithium-sulfur batteries. Electrically interconnected hierarchical porosity not only facilitates ion transport and polysulfide confinement but also accommodates substantial volume expansion, collectively contributing to high sulfur utilization, superior catalytic conversion, and excellent rate capability. In-depth microstructural characterization along with density functional theory simulation reveals that local lattice strain in MXene plane enforced by nonplanar interfacial geometry, boosts polysulfide adsorption. The proposed interface-directed functionalization strategy and the resulting hierarchical network structure offer a versatile framework for judicious microstructural tuning of MXene-based electrodes beyond typical energy storage applications.

Keywords: Interfacial functionalization, Hierarchical structure, Self-assembly, MXenes, Li-S batteries