Wu, Y; Xu, Y; Li, Y; Lyu, P; Wen, J; Zhang, C; Zhou, M; ... Lei, Y; + view all Wu, Y; Xu, Y; Li, Y; Lyu, P; Wen, J; Zhang, C; Zhou, M; Fang, Y; Zhao, H; Kaiser, U; Lei, Y; - view fewer (2019) Unexpected intercalation-dominated potassium storage in WS₂ as a potassium-ion battery anode. Nano Research , 12 pp. 2997-3002. 10.1007/s12274-019-2543-0.

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Abstract

Unexpected intercalation-dominated process is observed during K^{+} insertion in WS_{2} 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 WS_{2} 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.

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