Uniform yolk−shell Fe7S8@C nanoboxes as a general host material for the efficient storage of alkali metal ions

Abstract

Iron sulfides are potential anode materials for the reversible electrochemical storage of alkali metal ions (Li+, Na+, or K+) from the perspective of high theoretical capacity and relatively low cost. Nevertheless, their real application is greatly hampered by the inferior conductivity and the huge volume variations in the reaction with alkali metal ions. Few studies have examined desirable candidates that can be used as current host materials for alkali metal ions. In this work, a mild etching approach coupled with further sulfidation has been proposed for the precise design and preparation of uniform yolk−shell Fe7S8@C nanoboxes. The as-prepared yolk−shell Fe7S8@C nanoboxes exhibit excellent storage performance for alkali metal ions in the aspects of high specific capacity, superior cyclic stability, and good rate performance. The excellent electrochemical behaviour is attributed to the rational design of yolk−shell nanostructure.