Unraveling Electrode Surface Chemistry in Determining Interphase Stability and Deposition Homogeneity for Anode‐Free Potassium Metal Batteries

Potassium metal batteries with an anode-less/-free configuration could realize competitive energy density, which requires exceptional potassium plating/stripping reversibility via guiding smooth potassium growth and building mechanically stable solid electrolyte interphase (SEI). Electrolyte engineering has been the most widely adopted strategy, but there is less understanding of the electrode effect. We demonstrate that the extent of electrolyte decomposition could also be regulated through electrode surface modification. Elevating the work function of an Al current collector by coating a thin layer of Ni-decorated carbon nanofiber could greatly suppress the copious solvent reduction, leading to the formation of inorganic-rich SEIs. Such SEIs possess a large elastic deformation energy to accommodate the volume change and a high ionic conductivity to boost the reaction kinetics. Moreover, the potassiophilic nickel species offer abundant active sites to induce homogeneous potassium deposition. Benefiting from the synergy of stable interphases and promoted nucleation, the modified Al enables a 4.4 V anode-free cell in a normal-concentration electrolyte without anode precycling.