Synergistic polyoxometalate–bimetal oxide in hierarchical porous nanofibers for high-rate and long-life lithium-ion anodes

The integration of functionally complementary materials into a unified architecture is a powerful strategy for developing advanced electrodes. Herein, a hierarchical porous carbon nanofiber composite (PWN/FeVO₄@CNF) embedding Ni-substituted Keggin-type phosphotungstate (PWN) and bimetal oxide FeVO₄ were synthesized via electrospinning and controlled calcination. As an anode for lithium-ion-battery (LIBs), the PWN/FeVO₄@CNF composite surpasses its individual components, delivering a high discharge capacity of 1327.7 mA h g^-1 at 0.1 A g^-1. It exhibits exceptional durability with a capacity of 1280.0 mA h g^-1 after 500 cycles, and maintains 715.4 mA h g^-1 at a high current density of 2 A g^-1. This brilliant property stems from its enhanced Li⁺ diffusion coefficient, reduced charge-transfer resistance, and enlarged electrochemical surface. Kinetic analyses reveal a hybrid storage mechanism involving both diffusion-controlled (i∝v^1/2) and pseudocapacitive (i∝v) processes, with the latter dominating at increased scan rates. The synergistic combination of the multi-electron redox activity of PWN and the high capacity of FeVO₄, within a conductive and buffering carbon matrix, yields outstanding performance in LIBs. This strategy effectively overcomes the poor conductivity and severe volume expansion of individual metal oxides while maximizing their high-capacity advantages.