Engineered single-crystal metal-selenide for rapid K-ion diffusion and polyselenide convention

Abstract Metal selenides possess tremendous potentials due to their high specific capacity for potassium storage, however the sluggish K+ diffusion and polyselenide dissolution always result in inferior electrochemical performance. Herein, metal selenide (CoSe2) nanorods with engineered exposed plane incorporated in reduced graphene oxide nanosheet (sc-CoSe2@rGO) are fabricated. In the crystalline interior, such single-crystal structure can provide unhindered path for the fast K+ transfer. Besides, at the crystalline surface, the mainly exposed (011) facet with Co2+ rich state can induce the catalytic function with enormous reaction sites, which effectively transform the polyselenide to selenide with an enhanced selenium utilization. As expected, the as-prepared sc-CoSe2@rGO delivers satisfied specific capacity, prominent rate property, and superior cyclic stability (a reversible capacity of 157.7 mAh g−1 at high rate of 3.0 A g−1 after 600 cycles). This single-crystalline architecture design for intrinsic K-ion diffusion and surficial optimization is pioneeringly investigated, which provides a new insight into designing and fabricating metal-ion storage materials.