Building core-shell FeSe₂@C anode electrode for delivering superior potassium-ion batteries

Inferior electrical conductivity and large volume variation are two disadvantages of metal selenides. In this work, we have designed a core-shell structure of FeSe₂@C composite with low cost using facile hydrothermal method. The FeSe₂particles as the 'core' and the carbon layer as the 'shell' displayed good synergistic effect that attributed to alleviate volume expansion of electrode and improving the electrical conductivity, which achieved the fast potassium storage. The core-shell structural FeSe₂@C electrode achieved 286 mA h g^-1at 1 A g^-1over 1000 cycles with 99.8% coulombic efficiency and delivered excellent rate capacity with 273 mA h g^-1at 2 A g^-1, which was ascribed to dispersed FeSe₂particles and the strong carbon shell coating. This work will provide the basis for the further development of the application of metal selenides in the field of flexible electrodes.