Hierarchical structure composed of Cu2S nanosheets/rods wrapped with phosphorus-doped carbon as a freestanding electrode for advanced sodium-ion battery

Copper sulfide (Cu₂S) has emerged as a promising anode material for sodium-ion batteries (SIBs), owing to its cost-effectiveness, natural abundance, and environmental compatibility. However, its practical application is hindered by intrinsic limitations including poor electrical conductivity and severe volume expansion during cycling. To address these challenges, we developed a novel hybrid architecture composed of phosphorus-doped carbon wrapped Cu₂S nanosheet/rods with (P-Cu₂S@C NSRs) through an eco-friendly, solid ionic resin-assisted chemical vapor deposition (CVD)-like strategy, where the resin simultaneously serves as dual phosphorus and sulfur precursors. This hierarchical structure synergistically achieves three critical functions: 1) effective buffering of Cu₂S volume fluctuations, 2) prevention of aggregation, and 3) shortened Na⁺ diffusion pathways. When directly employed as a binder-free electrode (grow on copper foam), the P-Cu₂S@C NSRs demonstrate exceptional electrochemical performance without requiring additional conductive agents or post-synthesis treatments. The optimized electrode delivers a remarkable areal capacity of 3.69 mAh cm^–2 (93.3 % initial Coulombic efficiency) after 100 cycles at 0.5 mA cm^–2, maintaining 3.22 mAh cm^–2 after 500 cycles at an elevated current density of 1 mA cm^–2. This work establishes a sustainable synthesis paradigm for designing high-capacity metal sulfide anodes with superior structural stability for next-generation energy storage systems.