Dendritic growth is relevant to the enrichment of local space charge, which largely resulting from weak connection between the deposited potassium metal and substrate. Here we illustrate the original growth mechanism of K metal by combining the tested over potential, the calculation of Gibbs free energies of K metal nucleate-grow on different substrates and Simulation models of electric field values. This mechanism suggests NiO nanoparticles as induced nuclear sites are implanted in puffed millet (PM) and can form well-knit root structures for large volume potassium metal deposition. Depending on this novel design, the PM/NiO/K electrode exhibits tiny voltage hysteresis in symmetric cells and the full battery (Potassium Prussian blue as cathode) reveals improved electrochemical performance. This work proposes a fabrication to achieve stable high-energy density anodes and suggests that the initial nucleation process is a crucial factor of dendritic growth.