Core-Shell Fe_{1- x}S@Na_2.9PS_3.95Se_0.05 Nanorods for Room Temperature All-Solid-State Sodium Batteries with High Energy Density.

Abstract

High ionic conductivity electrolyte and intimate interfacial contact are crucial factors to realize high-performance all-solid-state sodium batteries. Na_2.9PS_3.95Se_0.05 electrolyte with reduced particle size of 500 nm is first synthesized by a simple liquid-phase method and exhibits a high ionic conductivity of 1.21 × 10^-4 S cm^-1, which is comparable with that synthesized with a solid-state reaction. Meanwhile, a general interfacial architecture, that is, Na_2.9PS_3.95Se_0.05 electrolyte uniformly anchored on Fe_{1- x}S nanorods, is designed and successfully prepared by an in situ liquid-phase coating approach, forming core-shell structured Fe_{1- x}S@Na_2.9PS_3.95Se_0.05 nanorods and thus realizing an intimate contact interface. The Fe_{1- x}S@Na_2.9PS_3.95Se_0.05/Na_2.9PS_3.95Se_0.05/Na all-solid-state sodium battery demonstrates high specific capacity and excellent rate capability at room temperature, showing reversible discharge capacities of 899.2, 795.5, 655.1, 437.9, and 300.4 mAh g^-1 at current densities of 20, 50, 100, 150, and 200 mA g^-1, respectively. The obtained all-solid-state sodium batteries show very high energy and power densities up to 910.6 Wh kg^-1 and 201.6 W kg^-1 based on the mass of Fe_{1- x}S at current densities of 20 and 200 mA g^-1, respectively. Moreover, the reaction mechanism of Fe_{1- x}S is confirmed by means of ex situ X-ray diffraction techniques, showing that partially reversible reaction occurs in the Fe_{1- x}S electrode after the second cycle, which gives the obtained all-solid-state sodium battery an exceptional cycling stability, exhibiting a high capacity of 494.3 mAh g^-1 after cycling at 100 mA g^-1 for 100 cycles. This contribution provides a strategy for designing high-performance room temperature all-solid-state sodium battery.