Electron delocalization–driven pseudocapacitive energy storage

Efficient Li + and electron transport are important for intercalation pseudocapacitive energy storage. Here, one-dimensional Magnéli-phase W 18 O 49 nanorods are synthesized at 1350–1550 °C by hot-filament metal oxide vapor deposition (HFMOVD) method and investigated as intercalation pseudocapacitive electrodes. Increasing the synthesis temperature modifies the oxygen-defect characteristics, accompanied by enhanced Li⁺ diffusion kinetics and pseudocapacitive charge storage. The optimized W 18 O 49 nanorod-based pseudocapacitor@1550 °C delivers specific capacitances of ∼118.94 F g −1 from cyclic voltammetry and ∼41.32 F g −1 from galvanostatic charge–discharge, while retaining ∼98.37% of its initial capacitance after 5000 cycles. Spin-polarized DFT + U calculations for representative Li x W 18 O 49 configurations (x = 0, 1, 2) reveal progressive Li + -induced electronic reconstruction, including extended spin-density distribution, changes in W–5d/O–2p hybridization, and increased density of states near the Fermi level. With increasing Li + content, the Fermi-level band velocity increases from ∼8.6 × 10 5 to ∼10.1 × 10 5 m s −1 , while the magnitude of the corresponding effective mass decreases from ∼1.56 to ∼0.58 m 0 , indicating more dispersive electronic states and enhanced electron delocalization. These results connect synthesis-temperature-dependent oxygen-defect evolution and Li + transport kinetics with Li + -induced electron delocalization, providing an electronic basis for the enhanced pseudocapacitive energy storage of W 18 O 49 nanorods.