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

The integration of functionally complementary materials into a unified architecture is an effective strategy for the development of advanced electrodes. Therefore, this study synthesized a hierarchical porous carbon nanofiber composite (PWN/FeVO₄@CNF) that incorporates Ni-substituted Keggin-type phosphotungstate (PWN) and bimetal oxide FeVO₄ via electrospinning and controlled calcination. As an anode for lithium-ion batteries (LIBs), PWN/FeVO₄@CNF outperforms its individual components, thereby achieving a high discharge capacity of 1327.7 mA·h·g⁻¹ at 0.1 A·g⁻¹. Additionally, it exhibits exceptional durability, retaining 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. These properties are derived from an enhanced Li⁺ diffusion coefficient, reduced charge-transfer resistance, and an enlarged electrochemical surface. Kinetic analyses reveal a hybrid storage mechanism involving diffusion-controlled (i ∝ v^1/2) and pseudocapacitive (i ∝ v) processes, with the latter dominating at higher scan rates. The synergistic combination of PWN’s multielectron redox activity and FeVO₄’s high capacity, within a conductive and buffering carbon matrix, leads to outstanding LIB performance. This approach effectively addresses the poor conductivity and severe volume expansion associated with individual metal oxides while maximizing their high-capacity advantages.