Heterophase Engineering Creates a Built‐in Highway to Achieve Local High‐Concentration Phosphorus Doping for Robust K‐Ion Storage

Doping is a promising strategy to enhance the K⁺ storage performance of transition metal chalcogenides (TMCs), which are attractive conversion-type anodes for K-ion batteries (KIBs) due to their low cost and natural abundance. However, conventional doping approaches are often limited by low doping content or structural degradation at high doping levels, making it highly challenging to achieve efficient doping without compromising structural integrity. Herein, a local high-concentration doping strategy enabled by heterophase engineering is proposed to overcome this limitation. The boundaries in the heterophase of CoSe₂/ZnSe act as built-in highways for dopant diffusion and doping formation, achieving a remarkably high P doping content of 34 at.%. Such local high-concentration P doping enhances the internal electric field and weakens bonding strength, thereby accelerating K⁺ storage kinetics. Benefiting from these effects, the optimized P-C/Z@C electrode delivers outstanding electrochemical performance, including 166 mAh g^-1 at 10.0 A g^-1 and 180 mAh g^-1 at 5.0 A g^-1 after 1400 cycles. Moreover, a full battery paired with a potassium Prussian blue cathode achieves a high energy density of 218 Wh kg^-1, highlighting its practical feasibility. This work provides a new pathway for enhancing doping efficiency in TMCs and offers valuable insights for designing high-performance anodes for KIBs.