Optimized K⁺ Deposition Dynamics via Potassiphilic Porous Interconnected Mediators Coordinated by Single-Atom Iron for Dendrite-Free Potassium Metal Batteries

Potassium metal batteries are emerging as a promising high-energy density storage solution, valued for their cost-effectiveness and low electrochemical potential. However, understanding the role of potassiphilic sites in nucleation and growth remains challenging. This study introduces a single-atom iron, coordinated by nitrogen atoms in a 3D hierarchical porous carbon fiber (Fe─N-PCF), which enhances ion and electron transport, improves nucleation and diffusion kinetics, and reduces energy barriers for potassium deposition. Molten potassium infusion experiments confirm the Fe─N-PCF's strong potassiphilic properties, accelerating adsorption kinetics and improving potassium deposition performance. According to the Scharifker-Hills model, traditional carbon fiber substrates without potassiphilic sites cause 3D instantaneous nucleation, leading to dendritic growth. In contrast, the integration of single-atom and hierarchical porosity promotes uniform 3D progressive nucleation, leading to dense metal deposition, as confirmed by dimensionless i²/i_max ² versus t/t_max plots and real-time in situ optical microscopy. Consequently, in situ X-ray diffraction demonstrated stable potassium cycling for over 1900 h, while the Fe─N-PCF@K||PTCDA full cell retained 69.7% of its capacity after 2000 cycles (72 mAh g^-1), with a low voltage hysteresis of 0.876 V, confirming its strong potential for high energy density and extended cycle life, paving the way for future advancements in energy storage technology.