Homogeneous Intercalation Chemistry and Ultralow Strain of 1T’’’ MoS2 for Stable Potassium Storage

Abstract Intercalation anodes usually exhibit better cyclability than conversion and alloying anodes for lithium or sodium storage due to the robust layered structure. However, for larger‐sized potassium accommodation, these intercalation anodes usually undergo huge layer expansion and structural distortion, triggering severe capacity fading. Herein, the novel 1T’’’ MoS 2 is revealed the intercalation anode for stable K + storage, in which metallic Mo─Mo bonds and puckered S layers accelerate the charge transfer and homogeneous K + insertion. Moreover, the ultralow strain (3.5%) induced by the non‐detachable potassium ions pillar sustains the layered structure. Consequently, 1T’’’ MoS 2 achieves a reversible capacity of 125 mA h g −1 at 0.2 C and keeps nearly 100% capacity retention at 1 C over 500 cycles. In situ characterizations and density functional theory simulations reveal the in‐depth intercalation reaction accompanied by the MoS 2 phase transformation between 1T’’’ and 1T’ during cycling. Furthermore, a 1T’’’ MoS 2 //MCMB K‐dual ion battery displays a superior cycling lifespan with 98% capacity retention over 250 cycles. This study provides a new intercalation anode and contribute to the electrode design for stable potassium ion storage.