Studies of FeSe2Cathode Materials for Mg-Li Hybrid Batteries

Rechargeable magnesium (Mg)-based energy storage has attracted extensive attention in electrochemical storage systems with high theoretical energy densities. The Mg metal is earth-abundant and dendrite-free for the anode. However, there is a strong Coulombic interaction between Mg(2+)and host materials that often inhibits solid-state diffusion, resulting in a large polarization and poor electrochemical performances. Herein, we develop a Mg-Li hybrid battery using a Mg-metal anode, an FeSe(2)powder with uniform size and a morphology utilizing a simple solution-phase method as the counter electrode and all-phenyl-complex/tetrahydrofuran (APC)-LiCl dual-ion electrolyte. In the Li+-containing electrolyte, at a current density of 15 mA g(-1), the Mg-Li hybrid battery (MLIB) delivered a satisfying initial discharge capacity of 525 mAh g(-1). Moreover, the capacity was absent in the FeSe2|APC|Mg cell. The working mechanism proposed is the Li+-only intercalation at the FeSe(2)and the Mg(2+)dissolved or deposited at the Mg foil in the FeSe2|Mg2+/Li+|Mg cell. Furthermore, ex situ XRD was used to investigate the structural evolution in different charging and discharging states.