Regulating the PO₄ and TiO₆ Polyhedral Building Blocks in TiP₂O₇ Boosts the Potassium Ion Diffusion Kinetics

Abstract

Achieving fast and durable potassiation/depotassiation of anode materials for potassium ion batteries (PIB) still remains an elusive yet fascinating goal. Herein, we challenge the conventional wisdom in synthesizing the TiP2O7 superstructure and report a nanocarbon coating on TiP2O7 (TiP2O7/C) using layered MXene as a Ti source to realize an effective tuning in the TiO6 and PO4 building blocks for boosting the K+ diffusion kinetics in PIB. Experimental investigations coupled with systematic theoretical simulations indicate that the interface interaction between TiP2O7 and coated nanocarbon could induce internal adjustment in individual Ti–O bonding and relieve the local distortions of TiO6 octahedra, which endows the TiP2O7/C with favorable regulation in a K+ hopping manner and significantly reduces the K+ diffusion barrier via the diffusion propagation along PO4 blocks with dominant coordination between O/P and K+. Consequently, the TiP2O7/C anode could retain 230 mA h g–1 even after 2200 long-term cycles with an ultralow degradation rate of 0.005%.