Effects of Ti-Substitution on Electrochemical Properties of KVPO₄F for K-Ion Batteries

For large-scale energy storage applications, the potassium (K)-ion battery system consisting of electrodes that reversibly intercalate potassium (K) ions have received recent research interest due to the earth-abundance of K resources.^1-3 To design K-ion cathodes, materials with open and rigid frameworks are considered desirable due to the large ionic radius of potassium.^1，2，4-8 Particularly, KVPO₄F with a tetrahedral phosphate framework has the potential to achieve effective K storage.^1，2，5 In this presentation, we will demonstrate the impact of partial titanium (Ti) substitution for vanadium (V) on the structure and electrochemical properties of KVPO₄F. We found that kinetics and reversibility of K intercalation and the associated physicochemical properties of Ti-substituted KVPO₄F are strongly coupled with local coordination of K. Ti-substituted KVPO₄F delivers a reversible discharge capacity of ~ 97 mAh/g at an average working voltage at 4 V over the extended number of cycles. Our results suggest that understanding the K environment can be an effective approach to designing K-ion cathode materials.<br/><br/>Reference:<br/>1. H. Kim, J.C. Kim, M. Bianchini, D.H. Seo, J. Rodriguez-Garcia and G.J.A.E.M. Ceder: Recent progress and perspective in electrode materials for K-ion batteries. 8, 1702384 (2018).<br/>2. H. Kim, D.H. Seo, M. Bianchini, R.J. Clément, H. Kim, J.C. Kim, Y. Tian, T. Shi, W.S. Yoon and G.J.A.E.M. Ceder: A New Strategy for High-Voltage Cathodes for K-Ion Batteries: Stoichiometric KVPO4F. 8, 1801591 (2018).<br/>3. J. Ma, Y. Li, N.S. Grundish, J.B. Goodenough, Y. Chen, L. Guo, Z. Peng, X. Qi, F. Yang and L.J.J.o.P.D.A.P. Qie: The 2021 battery technology roadmap. 54, 183001 (2021).<br/>4. H. Kim, J.C. Kim, S.H. Bo, T. Shi, D.H. Kwon and G.J.A.E.M. Ceder: K-ion batteries based on a P2-type K_0.6CoO₂ cathode. 7, 1700098 (2017).<br/>5. H. Kim, Y. Tian and G.J.J.o.T.E.S. Ceder: Origin of capacity degradation of high-voltage KVPO₄F cathode. 167, 110555 (2020).<br/>6. T. Hosaka, T. Shimamura, K. Kubota and S.J.T.C.R. Komaba: Polyanionic Compounds for potassium-ion batteries. 19, 735 (2019).<br/>7. L. Sharma and A.J.J.o.M.C.A. Manthiram: Polyanionic insertion hosts for aqueous rechargeable batteries. 10, 6376 (2022).<br/>8. K.-Y. Zhang, Z.-Y. Gu, E.H. Ang, J.-Z. Guo, X.-T. Wang, Y. Wang and X.-L.J.M.T. Wu: Advanced polyanionic electrode materials for potassium-ion batteries: Progresses, challenges and application prospects. (2022).