Unexpected intercalation-dominated process is observed duri ng K^+insertion in WS2 in a voltage range of 0.01-3.0 V.This is different fromthe previously reported two-dimensional(2D)transition metal dichalcogenides tha...Unexpected intercalation-dominated process is observed duri ng K^+insertion in WS2 in a voltage range of 0.01-3.0 V.This is different fromthe previously reported two-dimensional(2D)transition metal dichalcogenides that undergo a conversion reaction in a low voltage rangewhen used as anodes in potassium-ion batteries.Charge/discharge processes in the K and Na cells are studied in parallel to demonstrate thedifferention storage mechanisms.The Na^+storage proceeds through intercalation and conversion reactions while the K^+storage is governedby 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 stablecyclability up to 400 cycles at 500 mA·g^-1.Kinetics study proves the facilitation of K^+transport is derived from the intercalation-dominatedmecha nism.Furthermore,the mechanismis verified by the density functional theory(DFT)calculations,showing that the progressive expansion of the interlayer space can account for the observed results.展开更多
文摘Unexpected intercalation-dominated process is observed duri ng K^+insertion in WS2 in a voltage range of 0.01-3.0 V.This is different fromthe previously reported two-dimensional(2D)transition metal dichalcogenides that undergo a conversion reaction in a low voltage rangewhen used as anodes in potassium-ion batteries.Charge/discharge processes in the K and Na cells are studied in parallel to demonstrate thedifferention storage mechanisms.The Na^+storage proceeds through intercalation and conversion reactions while the K^+storage is governedby 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 stablecyclability up to 400 cycles at 500 mA·g^-1.Kinetics study proves the facilitation of K^+transport is derived from the intercalation-dominatedmecha nism.Furthermore,the mechanismis verified by the density functional theory(DFT)calculations,showing that the progressive expansion of the interlayer space can account for the observed results.
