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

© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 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 (K4Nb6O17) 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 K4Nb6O17 are slightly elongated with increased degrees of disorder. Specifically, the engineered K4Nb6O17 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 K4Nb6O17. Interestingly, the diffusion coefficient of K+ is one order of magnitude higher than that of Li+, and the engineered K4Nb6O17 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.