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

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.