Layer-by-Layer Assembly of Hierarchical Cotton-Derived C/Cu₂O/Na₂MoO₄ Composite Fibers as Anodes for Lithium-Ion...

Sodium molybdate (Na₂MoO₄) is attractive for lithium storage because of its multielectron conversion chemistry, but its low electrical conductivity and structural reconstruction during cycling limit active-material utilization and long-term reversibility. Here, hierarchical C/Cu₂O/Na₂MoO₄ composite fibers were constructed by combining a cotton-derived micro/nanofibrous carbon framework with Cu₂O interfacial modification and electrostatic layer-by-layer (LbL) assembly. The resulting architecture retains the interconnected fibrous structure of the original cotton fibers. A Na₂MoO₄-containing active layer is constructed on the Cu₂O-modified carbon fiber surface, and its loading can be regulated by changing the number of LbL assembly cycles. When evaluated as an anode for lithium-ion batteries, the C/Cu₂O/Na₂MoO₄-50 composite exhibits the best overall electrochemical performance, with an initial Coulombic efficiency of 65.2% and a reversible capacity of approximately 579.3 mAh g^-1 after 1000 cycles, whereas pristine Na₂MoO₄ retains only about 66.7 mAh g^-1. The hierarchical fibrous carbon network supplies long-range electron conduction, while the micro- and nanoscale fiber surface places the conversion-active phase close to the electrolyte and shortens the Li⁺ transport distance. The Cu₂O-modified surface provides the interface for subsequent LbL deposition, allowing Na₂MoO₄ to remain distributed along the conductive fiber rather than forming an isolated bulk active phase. This work shows that combining biomass-derived structural inheritance with controllable LbL assembly provides a viable route for regulating the integration and utilization of conversion-active phases in lithium storage electrodes.