Homogeneous intercalation chemistry and ultralow strain of 1T${}^{\prime \prime \prime }$ MoS${}_2$ for stable potassium storage

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${}^{\prime \prime \prime }$ 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${}^{\prime \prime \prime }$ 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${}^{\prime \prime \prime }$ and 1T${}^{\prime }$ during cycling. Furthermore, a 1T${}^{\prime \prime \prime }$ 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. (© 2023 Wiley‐VCH GmbH)