[en] Highlights: • A high energy density lithium metal battery is operated at high cut-off voltage of 4.6 V. • A new sulfite-type additive, BDTD is suggested for high voltage operating lithium metal batteries. • BDTD forms SEI and CEI on the surface of lithium metal anode NMC622 cathode, respectively. -- Abstract: The combination of high specific-capacity lithium (Li) metal anode and high cut-off voltage in Li secondary batteries provides an innovative method to realize high energy-density rechargeable batteries that satisfy the needs of future applications. However, an upgrade of both the cathode and anode is vital to establish high-voltage lithium metal batteries (LMB) concepts. In this study, we fabricated an electrolyte additive, [4, 4′-bi(1,3,2-dioxathiolane)] 2,2′-dioxide (BDTD), based on a novel sulfite-type additive and applied in LMB. Suppression of the Li dendrite growth on the Li metal anode was ensured by homogeneous Li plating in Li/Li symmetric cells. Scanning electron microscopy images demonstrated anode stabilization due to the introduction of the BDTD additive. In addition, X-ray photoelectron spectroscopy results confirmed the stabilization of the LiNi_0.6Mn_0.2Co_0.2O₂ cathode by protective cathode-electrolyte interphase made from the BDTD additive. This single additive introduced in the electrolyte enhanced both electrodes synergistically, and thus it resulted in an extended cycle life with high capacity retention in the high-voltage operation (4.6 V). We believe that this study will open new avenues for fabricating batteries with high-energy-density from high-voltage LMBs via this dual-function additive.