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Nano Research

Article Title

Unexpected intercalation-dominated potassium storage in WS2 as a potassium-ion battery anode

Keywords

potassium-ion battery, anode, WS2, intercalation

Abstract

Unexpected intercalation-dominated process is observed during K+ insertion in WS2 in a voltage range of 0.01–3.0 V. This is different from the previously reported two-dimensional (2D) transition metal dichalcogenides that undergo a conversion reaction in a low voltage range when used as anodes in potassium-ion batteries. Charge/discharge processes in the K and Na cells are studied in parallel to demonstrate the different ion storage mechanisms. The Na+ storage proceeds through intercalation and conversion reactions while the K+ storage is governed by an intercalation reaction. Owing to the reversible K+ intercalation in the van der Waals gaps, the WS2 anode exhibits a low decay rate of 0.07% per cycle, delivering a capacity of 103 mAh·g−1 after 100 cycles at 100 mA·g−1. It maintains 57% capacity at 800 mA·g−1 and shows stable cyclability up to 400 cycles at 500 mA·g−1. Kinetics study proves the facilitation of K+ transport is derived from the intercalation-dominated mechanism. Furthermore, the mechanism is verified by the density functional theory (DFT) calculations, showing that the progressive expansion of the interlayer space can account for the observed results.

Graphical Abstract

Publisher

Tsinghua University Press

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