Strongly Coupled NbSe₂ Ultrathin Nanosheets/Graphene Heterostructure Facilitates Potassium Ion Storage

Layered transition metal dichalcogenides are of intensive interest for potassium‐ion batteries (PIBs) due to their high theoretical capacity, relatively low working potential, and layered structures. However, the limited interlayer spacing poses challenges in accommodating large‐radius potassium ions, significantly affecting their rate and cycling performances, particularly for selenide counterparts. Herein, a class of the strongly coupled NbSe 2 nanosheets (NSs)/graphene (G) heterostructure with expanded interlayer spacings and high electron conductivity for boosting the performance of potassium storage is reported. NbSe 2 NSs/G delivers a reversible capacity of 348.4 mAh g −1 at 0.05 A g −1 , exceptional rate performance (117.5 mAh g −1 at an ultrahigh current density of 10.0 A g −1 ), and excellent cycle stability (capacity retention of 167.8 mAh g −1 after 2350 cycles under 2.0 A g −1 ), placing it among the top performers in reported TMD‐based PIB anodes. In situ XRD and Raman measurements reveal the intercalation‐based mechanism in NbSe 2 NSs/G and the introduction of graphene can alleviate the severe volume change, making it possess superior rate performance and cycle stability Prominently, full‐cell PIBs employing NbSe 2 NSs/G anodes demonstrate remarkable rate capability, and achieve a high energy density of 103.0 Wh kg −1 and a high power density of 1140.6 W kg −1 .