Built-In Electric Field-Driven Ultrahigh-Rate K-Ion Storage via Heterostructure Engineering of Dual Tellurides Integrated with Ti3C2Tx MXene

Exploiting high-rate anode materials with fast K⁺ diffusion is intriguing for the development of advanced potassium-ion batteries (KIBs) but remains unrealized. Here, heterostructure engineering is proposed to construct the dual transition metal tellurides (CoTe₂/ZnTe), which are anchored onto two-dimensional (2D) Ti₃C₂T_x MXene nanosheets. Various theoretical modeling and experimental findings reveal that heterostructure engineering can regulate the electronic structures of CoTe₂/ZnTe interfaces, improving K⁺ diffusion and adsorption. In addition, the different work functions between CoTe₂/ZnTe induce a robust built-in electric field at the CoTe₂/ZnTe interface, providing a strong driving force to facilitate charge transport. Moreover, the conductive and elastic Ti₃C₂T_x can effectively promote electrode conductivity and alleviate the volume change of CoTe₂/ZnTe heterostructures upon cycling. Owing to these merits, the resulting CoTe₂/ZnTe/Ti₃C₂T_x (CZT) exhibit excellent rate capability (137.0 mAh g^-1 at 10 A g^-1) and cycling stability (175.3 mAh g^-1 after 4000 cycles at 3.0 A g^-1, with a high capacity retention of 89.4%). More impressively, the CZT-based full cells demonstrate high energy density (220.2 Wh kg^-1) and power density (837.2 W kg^-1). This work provides a general and effective strategy by integrating heterostructure engineering and 2D material nanocompositing for designing advanced high-rate anode materials for next-generation KIBs.