MoS₂ as a long-life host material for potassium ion intercalation

Electrochemical potassium ion intercalation into two-dimensional layered MoS₂ was studied for the first time for potential applications in the anode in potassium-based batteries. X-ray diffraction analysis indicated that an intercalated potassium compound, hexagonal K_0.4MoS₂, formed during the intercalation process. Despite the size of K⁺, MoS₂ was a long-life host for repetitive potassium ion intercalation and de-intercalation with a capacity retention of 97.5% after 200 cycles. The diffusion coefficient of the K⁺ ions in K_xMoS₂ was calculated based on the Randles-Sevcik equation. A higher K⁺ intercalation ratio not only encountered a much slower K⁺ diffusion rate in MoS₂, but also induced MoS₂ reduction. This study shows that metal dichalcogenides are promising potassium anode materials for emerging K-ion, K-O₂, and K-S batteries.