Mono-faceted WO3−x nanorods in situ hybridized in carbon nanosheets for ultra-fast/stable sodium-ion storage

Abstract

The electrochemical properties of electrode materials have been markedly optimized by the introduction of geometric architectures and structural engineering. Nevertheless, the superior features of mono-faceted electrodes for anode properties in metal-ion batteries remain unexplored. Herein, facet-stacked WO_3−x nanorods (NRs) are hybridized in situ in N-doped carbon nanosheets (CNSs) (WO_3−x NRs/N-CNSs) via a facile self-polymerization and post-calcination approach. The N-CNSs create continuous conductive networks for rapid and stable ion/electron transport, and the WO_3−x NRs with mono facets (010) can provide open and short-range ordered ion-diffusion pathways, which contain abundant dangling bonds and unsaturated active sites derived from the oxygen vacancies of nonstoichiometric WO_3−x, thereby delivering superior reaction efficiency and robust structural stability for ultra-fast/stable sodium-ion storage. These findings are illustrated in detail using characterization techniques and density functional theory calculations. After 50 000 cycles, the WO_3−x NRs/N-CNSs show a gratifying reversible capacity of 184.6 mA h g⁻¹, with an average charge time of 34.8 s and a high capacity retention of ∼120% at 30.0 A g⁻¹. In particular, the WO_3−x NRs/N-CNSs//Na₃V₂(PO₄)₃ full-cells also display a high capacity of 112.5 mA h g⁻¹ after 300 cycles at 5.0 A g⁻¹. Therefore, combined with the in situ carbon compositing strategy, facet-stacked WO_3−x NRs can provide a valuable basis for developing high-rate and ultra-long-life metal-ion batteries.