Li₂CO₃ was introduced into LiPF₆-based electrolytes and the electrolytes were stored at 40 °C. Nuclear magnetic analysis of electrolytes and X-ray diffraction characterization of reaction residues demonstrate the formation of LiPO₂F₂ and LiF during storage. This reformulated electrolyte boosts lifespan and Coulombic efficiency (CE) in Li||Li and Li||Cu cells, with Li||Li cells stably cycling for >800 h and 300 h at 0.5 mA/cm² and 1.0 mA/cm², respectively. Moreover, with the optimal content of Li₂CO₃, the CE of the reformulated electrolyte (91.56%) is greatly improved compared to that of the standard electrolyte (81.99%). The compatibility and enhanced rate performance of the reformulated electrolyte are also exhibited in Li||NCM full cells with a moderately high mass loading of 9.6 mg/cm².