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Abstract LiNO₃is a widely used salt‐additive that markedly improves the stability of ether‐based electrolytes at a Li metal anode but is generally regarded as incompatible with alkyl carbonates. Here we find that contrary to common wisdom, cyclic carbonate solvents such as ethylene carbonate can dissolve up to 0.7 M LiNO₃without any additives, largely improving the anode reversibility. We demonstrate the significance of our findings by upgrading various state‐of‐the‐art carbonate electrolytes with LiNO₃, which provides large improvements in batteries composed of thin lithium (50 μm) anode and high voltage cathodes. Capacity retentions of 90.5 % after 600 cycles and 92.5 % after 200 cycles are reported for LiNi_0.6Mn_0.2Co_0.2O₂(2 mAh cm⁻², 0.5 C) and LiNi_0.8Mn_0.1Co_0.1O₂cathode (4 mAh cm⁻², 0.2 C), respectively. 1 Ah pouch cells (≈300 Wh kg⁻¹) retain more than 87.9 % after 100 cycles at 0.5 C. This work illustrates that reforming traditional carbonate electrolytes provides a scalable, cost‐effective approach towards practical LMBs. 

Reactive metals are known to electrodeposit with irregular morphological features on planar substrates. A growing body of work suggest that multiple variables: composition, mechanics, structure, ion transport properties, reductive stability, and interfacial energy of interphases, formed either spontaneously or by design on the metal electrode play important but differentiated roles in regulating these morphologies. We examine the effect of fluorinated thermoset polymer coatings on Li deposition by means of experiment and theoretical linear stability analysis. By tuning the chemistry of the polymer backbone and side chains, we investigate how physical and mechanical properties of polymeric interphases influence Li electrodeposit morphology. It is found that an interplay between elasticity and diffusivity leads to an optimum interphase thickness and that higher interfacial energy augments elastic stresses at a metal electrode to prevent out-of-plane deposition. These findings are explained using linear stability analysis of electrodeposition and provide guidelines for designing polymer interphases to stabilize metal anodes in rechargeable batteries.