Nanocellulose-Derived Hierarchical Carbon Framework-Supported P-Doped MoO₂ Nanoparticles for Optimizing Redox Kinetics in Lithium-Sulfur Batteries.

Abstract

The integration of nanocatalysts into the separators of lithium-sulfur batteries (LSBs) boosts the polysulfide conversion efficiency. However, the aggregation of catalyst nanoparticles diminishes the active surface area. Moreover, densely packed catalyst-modified layers often hinder ion transport rates and impede access to the catalytic sites. To overcome these challenges, a strategy is reported for modifying commercial separators, using wood nanocellulose as a building block to construct hierarchical P-doped MoO_2-x nanoparticles anchored on N, P co-doped porous carbon (P-MoO_2-x/NPC). The web-like entangled nanocellulose forms a framework for the in situ polymerization of polyaniline, providing abundant anchoring sites for MoO₂ nanoparticles. The addition of P atoms optimizes the d-band center of MoO₂ and enhances the catalytic activity of polysulfide conversion. The LSBs assembled using a P-MoO_2-x/NPC coated polypropylene separator display an initial discharge capacity of 1621 mAh g^-1 and rate performance of 774 mAh g^-1 at 5 C. Even with a sulfur loading of 8.1 mg cm^-2 and lean electrolyte conditions, the cell achieves an initial areal capacity of 11.3 mAh cm^-2 at 0.1 C. This work provides a biopolymer nanofiber solution for constructing LSB separators with advanced electrochemical reactivity.