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Abstract 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 i 2 /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.
Lin et al. (Thu,) studied this question.