Triggering highly conductive FePSe3 with Cu-based coordination towards all-climate ultrafast sodium ion storage

Abstract

Limited by the relative radii of sodium ions (0.102 nm), sodium ion batteries suffer from sluggish kinetics. Owing to the high conductivity of selenium, Se-rich samples have captured plenty of attention. Herein, FePSe₃ sheets were successfully prepared through vacuum tube sealing. Significantly, the as-resulted samples displayed considerable conductivity, further forming electrodes without conductive agents. Utilized as sodium ion storage anode with ether-based electrolytes, even at 20.0 A g⁻¹, the ultra-stable rate abilities could be retained at about 480 mA h g⁻¹ after 4000 cycles at room temperature (25 °C) and ∼210 mA h g⁻¹ after 10 000 loops at low temperature (−30 °C). Assisted by a series of Cu₂Se/Se samples, the strong coordination of Cu-atoms with DEGDME was noted, finally resulting in the formation of ultra-large coordination molecule Cu–(DEGDME)_n. From the detailed kinetic analysis, the coordination could offer rich shared electron pairs, inducing the quickening adsorption/desorption of ions, finally resulting in the remarkable pseudo-capacitive behavior Moreover, a detailed phase transformation (Cu⁰ → Cu¹⁺ → Cu²⁺) was carried out. Furthermore, the selection of glass fiber as separators was conducive to capturing NaPSes, improving the cycling stabilities. Given this, the work was anticipated to provide anion-rich materials for advanced SIBs anodes whilst shedding light on the in-depth reaction mechanism of metal-sulfide/selenides in ether-based electrolytes.