Yolk-shell-structured （Feo.sNio.s）9S8 solid-solution powders：Synthesis and application as anode materials for Na-ionbatteries

摘要

Multicomponent metal sulfide materials with a yolk-shell structure and a singlephase were studied for the first time as anode materials for sodium-ion batteries.Yolk-shell-structured Fe-Ni-O powders with a molar ratio of iron and nickelcomponents of 1/1 were prepared via one-pot spray pyrolysis. The preparedFe-Ni--O powders were transformed into yolk-shell-structured （Fe0.sNi0.s）9S8solid-solution powders via a sulfidation process. The initial discharge and chargecapacities of the （Fe0.sNi0.s）9S8 powders at a current density of I A.g-1 were 601 and504 mA-h.g-1, respectively. The discharge capacities of the （Fe0.sNi05）9S8 powdersfor the 2nd and 100~ cycle were 530 and 527 mA.h.g-1, respectively, and theircorresponding capacity retention measured from the 2nd cycle was 99%. The（Fe0.sNi0.5）9S8 powders had high initial discharge and charge capacities at a lowcurrent density of 0.1 A-g-1, and the reversible discharge capacity decreased slightlyfrom 568 to 465 mA.h.g-1 as the current density increased from 0,1 to 5.0 A.g^-1The synergetic effect of the novel yolk-shell structure and the multicomponentsulfide composition of the （Fe0.sNi0.s）9S8 powders resulted in excellent sodium-ionstorage performance.