Abstract
Potassium-ion batteries (PIBs) hold great promise as alternatives to lithium ion batteries in post-lithium age, while face challenges of slow reaction kinetics induced by the inherent characteristics of large-size K+. We herein show that creating sufficient exposed edges in MoS2 via constructing ordered mesoporous architecture greatly favors for improved kinetics as well as increased reactive sites for K storage. The engineered MoS2 with edge-enriched planes (EE-MoS2) is featured by three-dimensional bicontinuous frameworks with ordered mesopores of ~ 5.0 nm surrounded by thin wall of ~9.0 nm. Importantly, EE-MoS2 permits exposure of enormous edge planes at pore walls, renders its intrinsic layer spacing more accessible for K+ and accelerates conversion kinetics, thus realizing enhanced capacity and high rate capability. Impressively, EE-MoS2 displays a high reversible charge capacity of 506 mAh·g−1 at 0.05 A·g−1, superior cycling capacities of 321 mAh·g−1 at 1.0 A·g−1 after 200 cycles and a capacity of 250 mAh·g−1 at 2.0 A·g−1, outperforming edge-deficient MoS2 with nonporous bulk structure. This work enlightens the nanoarchitecture design with abundant edges for improving electrochemical properties and provides a paradigm for exploring high-performance PIBs.
Highlights
As one of the most promising substitutes for commercial lithium-ion batteries (LIBs), potassium-ion batteries (PIBs) have captured increasing attention owning to natural abundance of potassium in contrast to lithium (17,000 vs. 20 ppm in the earth crust) [1]
transition metal dichalcogenides (TMDs) have been receiving extensive attention owing to their potential advantages of layered structures with large interlayer spacing, which is favorable for ions diffusion and conversion kinetics [17]
The reduction of layers cuts down ions migration distance and exposes more edges, facilitating conversion kinetics and increasing reactive sites
Summary
As one of the most promising substitutes for commercial lithium-ion batteries (LIBs), potassium-ion batteries (PIBs) have captured increasing attention owning to natural abundance of potassium in contrast to lithium (17,000 vs. 20 ppm in the earth crust) [1]. The concept of edge engineering has been demonstrated to play a great role in boosting electrochemical activities, such as constraining Li dendrites [22], improving performance of aluminum batteries [23], Na/Li batteries [24] and Li-S batteries [25]. It could be envisioned while not yet explored that designing structures with highly exposed edges could resolve the sluggish kinetics and limited capacity caused by large-size K+, considering that plenty of edge planes could offer more easy access of K+ to promote ions diffusion and increase reactive sites in MoS2. Our finding suggests that fabricating edge-enriched planes may open a new avenue to obtain advanced electrochemical energy storage materials
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