Stabilizing intermediate phases via the efficient confinement effects of the SnS2-SPAN fibre composite for ultra-stable half/full sodium/potassium-ion batteries

Sodium/potassium-ion batteries (SIBs/PIBs) are expected to replace conventional lithium-ion batteries (LIBs) soon in view of their lower cost and the abundant reserves of sodium/potassium resources. However, it remains a challenge to explore suitable anode materials for SIBs/PIBs with high energy/power density and long lifespan due to the sluggish kinetics during the insertion/extraction of Na+/K+ ions with larger ionic sizes. Herein, ultra-small SnS2 nanocrystals encapsulated in sulphurized polyacrylonitrile (SPAN) fibres have been fabricated via electrospinning paired with sulphuration treatment. Density functional theory (DFT) calculations demonstrate that SPAN fibre can concentrate Na+ on the surface and offer additional storage sites with enhanced reaction kinetics. Consequently, this composite electrode manifests superb sodium/potassium-ion storage performance with high capacities (613 mA h g−1 after 50 cycles under 0.1 A g−1 for SIBs; 565 mA h g−1 at 0.05 A g−1 and 226 mA h g−1 at 5 A g−1 after 50 and 2000 cycles for PIBs) and superior long-life cycling capability (261 mA h g−1 after 30 000 cycles at 10 A g−1 for SIBs). Additionally, a sodium full cell assembled with Na3V2(PO4)3 as the cathode and SnS2-SPAN-470-1 as the anode displays excellent cycling performance. This work can provide new insights into the construction of novel transition metal dichalcogenide-based nanostructures and nanocomposites for high-performance electrochemical energy storage and conversion devices.