Vacancy engineering in WS2 nanosheets for enhanced potassium-ion storage

As a promising energy storage technology, potassium-ion batteries (PIBs) have received extensive attention because of the cheap and abundant potassium resources. To date, developing anodes for fast and reversible potassiation/depotassiation is in its infancy. This study reports WS2 nanosheets modified by abundant sulfur vacancies (denoted as Sv-WS2) as anode for PIBs for the first time. Benefiting from the synergistic effects of improved electronic conductivity and more active sites produced by sulfur vacancies, and rich interspace ac-quired by the connection of adjacent nanosheets, the Sv-WS2 anode displays a high reversible capacity of 303.3 mAh g(-1) at 0.05 A g(-1) and a high rate performance of 136.6 mAh g(-1) at 2.0 A g(-1), as compared with that (216.5 and 45.5 mAh g(-1)) of pristine WS2 (P-WS2). Ex situ characterizations confirm that the Sv-WS2 anode undergoes an intercalation-conversion reaction mechanism. First principles calculations further reveal that the creation of sulfur vacancies can availably lower K-insertion energy barriers and increase the electrical conductivity. This study demonstrates a further direction to effectively enhance the potassium storage capability of transition metal dichalcogenides.