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

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 (Ni0.7Co0.3)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 (Ni0.7Co0.3)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 (Ni0.7Fe0.3)S2/3DGA and (Co0.7Fe0.3)S2/3DGA. Our results show that engineering LDH precursors can offer an alternative for preparing diverse transition-metal sulfides for energy storage.