Co-Construction of Solid Solution Phase and Void Space in Yolk-Shell Fe 0.4 Co 0.6 S@N-Doped Carbon to Enhance Cycling Capacity and Rate Capability for Aluminum-Ion Batteries.

Rechargeable aluminum-ion batteries (AIBs), using low-cost and inherent safety Al metal anodes, are regarded as promising energy storage devices next to lithium-ion batteries. Currently, one of the greatest challenges for AIBs is to explore cathodes suitable for feasible Al 3+ insertion/extraction with high structure stability. Herein, a facile co-engineering on solid solution phase and cavity structure is developed via Prussian blue analogues by a simple and facile sulfidation strategy. The obtained uniform yolk-shell Fe 0.4 Co 0.6 S@N-doped carbon nanocages (y-s Fe 0.4 Co 0.6 S@NC) display a high reversible capacity of 141.3 mA h g -1 at 500 mA g -1 after 100 cycles and a good rate capability of 100.9 mA h g -1 at 1000 mA g -1 . The improved performance can be mainly ascribed to the dual merits of the composite; that is, more negative Al 3+ formation energy and improved Al 3+ diffusion kinetics favored by the solid solution phase and Al 3+ insertion/extraction accommodable space stemmed from the yolk-shell structure. Moreover, the reaction mechanism study discloses that the reaction involves the intercalation of Al 3+ ions into Fe 0.4 Co 0.6 S to generate Al l Fe m Co n S and elemental Fe and Co.