Solid-Solution Sulfides Derived from Tunable Layered Double Hydroxide Precursors/Graphene Aerogel for Pseudocapacitors and Sodium-Ion Batteries

Abstract

Transition-metal sulfides (TMSs) are suggested as promising electrode materials for electrochemical pseudocapacitors and lithium- and sodium-ion batteries; however, they typically involve mixed composites or conventionally stoichiometric TMSs (such as NiCo₂S₄ and Ni₂CoS₄). Herein we demonstrate a preparation of solid-solution sulfide (Ni_0.7Co_0.3)S₂ supported on three-dimensional graphene aerogel (3DGA) via a sulfuration of NiCo-layered double hydroxide (NiCo-LDH) precursor/3DGA. The electrochemical tests show that the (Ni_0.7Co_0.3)S₂/3DGA electrode exhibits a capacitance of 2165 F g^-1 at 1 A g^-1, 2055 F g^-1 at 2 A g^-1, and 1478 F g^-1 at 10 A g^-1; preserves 78.5% capacitance retention upon 1000 cycles for pseudocapacitors; and in particular, possesses a relatively high charge capacity of 388.7 mA h g^-1 after 50 cycles at 100 mA g^-1 as anode nanomaterials for sodium-ion batteries. Furthermore, the electrochemical performances are readily tuned by varying the cationic type of the tunable LDH precursors to prepare different solid-solution sulfides, such as (Ni_0.7Fe_0.3)S₂/3DGA and (Co_0.7Fe_0.3)S₂/3DGA. Our results show that engineering LDH precursors can offer an alternative for preparing diverse transition-metal sulfides for energy storage.

Keywords: graphene aerogel; layered double hydroxide precursor; pseudocapacitors; sodium-ion batteries; transition-metal sulfide.