Lithium metal batteries have obtained increasing interest due to their high specific capacity. Nonetheless, the growth of lithium dendrites brings safety risks to batteries and further deteriorates the performance. Herein, we explore diethyl phenylphosphonite (DEPP) as the electrolyte additive to alleviate this problem. DEPP can be preferentially decomposed than carbonate solvents to form the stable interface between electrolyte and lithium anode for inhibiting the dendrite growth. As expected, the symmetrical LiIILi cells could achieve a stable cycling performance with 200 h at 1 mA cm^-2. Moreover, DEPP can be preferentially oxidized on the surface of lithium cobalt oxides (LiCoO₂) to form a dense cathode electrolyte interphase (CEI) film for suppressing the continuous oxidative decomposition of the electrolyte and eliminating the adverse effects of HF on the battery. This endows LiCoO₂IILi full battery with the enhanced cycling and rate performance.