Potassium (K) metal anodes have attracted widespread attention in the realm of energy storage due to their cost-effectiveness, abundance, and high theoretical capacity. However, the undesirable K-dendrite growth accompanied by void formation upon prolonged cycling presents formidable obstacles to their real-world applications. Herein, phosphorus-based electrolytes are developed based on the electrolyte additive design criteria of steric hindrance, polar ability, and decomposition preference to enhance the anode/electrolyte interface stability. The additive triphenyl phosphate in the electrolyte could regulate the K+ solvation structure and promote the formation of an inorganic P-rich solid-electrolyte interphase layer, thus ultimately mitigating interfacial polarization, augmenting transport properties, and stabilizing the interphase. Therefore, we have successfully achieved a dense and dendrite-free K metal anode, exhibiting improved coulombic efficiency and prolonged lifespan. Our design tactic demonstrates the promising application of K metal batteries in achieving elevated safety, high energy densities, and extended operational longevity.