Dehydration-Triggered Ionic Channel Engineering in Potassium Niobate for Li/K-Ion Storage

Boosting charge transfer in materials is critical for applications involving charge carriers. Engineering ionic channels in electrode materials can create a skeleton to manipulate their ion and electron behaviors with favorable parameters to promote their capacity and stability. Here, tailoring of the atomic structure in layered potassium niobate (K₄ Nb₆ O₁₇ ) nanosheets and facilitating their application in lithium and potassium storage by dehydration-triggered lattice rearrangement is reported. The spectroscopy results reveal that the interatomic distances of the NbO coordination in the engineered K₄ Nb₆ O₁₇ are slightly elongated with increased degrees of disorder. Specifically, the engineered K₄ Nb₆ O₁₇ shows enhanced electrical and ionic conductivity, which can be attributed to the enlarged interlamellar spacing and subtle distortions in the fine atomic arrangements. Moreover, subsequent experimental results and calculations demonstrate that the energy barrier for Li⁺ /K⁺ diffusion is significantly lower than that in pristine K₄ Nb₆ O₁₇ . Interestingly, the diffusion coefficient of K⁺ is one order of magnitude higher than that of Li⁺ , and the engineered K₄ Nb₆ O₁₇ presents superior electrochemical performance for K⁺ to Li⁺ . This work offers an ionic engineering strategy to enable fast and durable charge transfer in materials, holding great promise for providing guidance for the material design of related energy storage systems.