TiO/MXene Hierarchical Bifunctional Catalyst Anchored on Graphene Aerogel toward Flexible and High-Energy Li-S Batteries.

The development of lithium-sulfur (Li-S) batteries with high-energy density, flexibility, and safety is very appealing for emerging implantable devices, biomonitoring, and roll-up displays. Nevertheless, the poor cycling stability and flexibility of the existing sulfur cathodes, flammable liquid electrolytes, and extremely reactive lithium anodes raise serious battery performance degradation and safety issues. Herein, a metallic 1T MoS and rich oxygen vacancies TiO/MXene hierarchical bifunctional catalyst (Mo-Ti/Mx) anchored on a reduced graphene oxide-cellulose nanofiber (GN) host (Mo-Ti/Mx-GN) was proposed to address the above challenges. By applying a directional freezing process, the hierarchical architecture of a flexible GN scaffold composed of waved multiarch morphology with long-range alignment is achieved. The synergetic effects of 1T MoS and TiO/MXene are beneficial to suppress the shuttling behavior of lithium polysulfides (LiPSs), expedite the redox kinetics of sulfur species, and promote the electrocatalytic reduction of LiPSs to LiS. The electrode demonstrates improved electrochemical properties with high sulfur-mass loading (8.4 mg cm) and lean electrolyte (7.6 μL mg) operation. We also explored the feasibility of producing pouch cells with such flexible electrodes, gel polymer electrolytes, and a robust lithium anode, which exhibited reversible energy storage and output, wide temperature adaptability, and good safety against rigorous strikes, implying the potential for practical applications.