Nitrate additives coordinated with crown ether stabilize lithium metal anodes in carbonate electrolyte

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 NO${}_3$${}^{-}$ ions and helps form a dense solid electrolyte interface that is Li${}_3$N-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. (© 2021 Wiley-VCH GmbH)