Lithium metal anodes (LMAs) are promising for next‐generation batteries but have poor compatibility with the widely used carbonate‐based electrolytes, which is a major reason for their severe dendrite growth and low Coulombic efficiency (CE). A nitrate additive to the electrolyte is an effective solution, but its low solubility in carbonates is a problem that can be solved using a crown ether, as reported. A rubidium nitrate additive coordinated with 18‐crown‐6 crown ether stabilizes the LMA in a carbonate electrolyte. The coordination promotes the dissolution of NO3− ions and helps form a dense solid electrolyte interface that is Li3N‐rich which guides uniform Li deposition. In addition, the Rb (18‐crown‐6)+ complexes are adsorbed on the dendrite tips, shielding them from Li deposition on the dendrite tips. A high CE of 97.1% is achieved with a capacity of 1 mAh cm−2 in a half cell, much higher than when using the additive‐free electrolyte (92.2%). Such an additive is very compatible with a nickel‐rich ternary cathode at a high voltage, and the assembled full battery with a cathode material loading up to 10 mg cm−2 shows an average CE of 99.8% over 200 cycles, indicating a potential for practical use. [ABSTRACT FROM AUTHOR]