Regulating Ion Transfer Dynamics and Potassium Polyselenide Dissolution in Dual‐Defect MoSe_2‐x@NC for Ultrafast and Stable Potassium‐Ion Storage

Abstract Molybdenum diselenide (MoSe₂), a promising anode material for potassium‐ion batteries (KIBs), often suffers from sluggish kinetics, substantial volumetric expansion, and dissolution and shuttling of intermediate phases, resulting in unsatisfactory cycle stability and rate performance. In this work, a dual‐defect MoSe₂ (equipped with interlayer defects and Se vacancies) is introduced by a novel plasma‐induced etching process, encapsulated in nitrogen‐doped porous carbon nanofibers (denoted as dd‐MoSe_2‐x@NC). These modifications create multidimensional potassium‐ion insertion channels, improve ion transfer dynamics, enhance intrinsic conductivity, and expose more reactive sites. Moreover, the nitrogen‐doped porous carbon matrix mitigates volumetric expansion and suppresses potassium‐polyselenide (K‐pSe_x) dissolution and shuttling through a physicochemical dual‐anchoring strategy. The dd‐MoSe_2‐x@NC electrode demonstrates remarkable electrochemical performance, achieving a high specific capacity of 418.5 mAh g⁻¹ at 0.05 A g⁻¹, reliable cycling stability over 1400 cycles at 2.0 A g⁻¹, and superior rate performance with 125.0 mAh g⁻¹ at 10.0 A g⁻¹. The findings elucidate the “intercalation‐conversion” reaction mechanism and show that the dd‐MoSe_2‐x@NC//PTCDA full cell attains high energy density (115.8 W h kg⁻¹) and high power density (1057.2 W kg⁻¹). This work highlights the enhanced potassium storage kinetics and cycling stability of layered transition metal chalcogenides, demonstrating the potential of MoSe₂ in high‐performance KIBs.