Precursor concentration-driven structural evolution and phosphate distribution in electrospun zinc phosphate–carbon nanofibers for lithium-ion storage

Reduced zinc phosphate-based carbon composite (Zn₃P_<i>x</i>O_<i>y</i>@C) nanofibers are synthesized <i>via</i> electrospinning, followed by a two-step heat treatment. The effect of precursor concentration on structural evolution, phosphate distribution, and electrochemical performance is investigated. Solution viscosity influences fiber formation and component interactions, leading to distinct differences in phosphate confinement and porosity. Before annealing, phosphate species are predominant on the surface at low concentrations, balanced at optimal concentrations, and suppressed by polymer accumulation at high concentrations. After annealing, fiber diameters increase at low and optimal concentrations but shrink at high concentrations due to phase redistribution. The optimized nanofibers exhibit a specific surface area of 454 m² g^-1 and 45 wt% carbon, achieving high initial discharge and charge capacities of 1180.6 and 772.6 mAh g^-1 at 100 mA g^-1, respectively, as free-standing lithium-ion battery anodes. These results provide insights into composition-driven nanofiber design for energy storage applications.