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Lithium metal has shown a lot of promise for use as an anode material in rechargeable batteries owing to its high theoretical capacity. However, it does not meet the cycle life and safety requirements of rechargeable batteries owing to electrolyte decomposition and dendrite formation on the surfaces of the lithium anodes during electrochemical cycling. Here, we propose a novel electrolyte system that is relatively stable against lithium metal and mitigates dendritic growth. Systematic design methods that combined simulations, model-based experiments, and in situ analyses were employed to design the system. The reduction potential of the solvent, the size of the salt anions, and the viscosity of the electrolyte were found to be critical parameters determining the rate of dendritic growth. A lithium metal anode in contact with the designed electrolyte exhibited remarkable cyclability (more than 100 cycles) at a high areal capacity of 12 mAh cm−2.

Securing the chemical and physical stabilities of electrode/solid‐electrolyte interfaces is crucial for the use of solid electrolytes in all‐solid‐state batteries. Directly probing these interfaces during electrochemical reactions would significantly enrich the mechanistic understanding and inspire potential solutions for their regulation. Herein, the electrochemistry of the lithium/Li7La3Zr2O12‐electrolyte interface is elucidated by probing lithium deposition through the electrolyte in an anode‐free solid‐state battery in real time. Lithium plating is strongly affected by the geometry of the garnet‐type Li7La3Zr2O12 (LLZO) surface, where nonuniform/filamentary growth is triggered particularly at morphological defects. More importantly, lithium‐growth behavior significantly changes when the LLZO surface is modified with an artificial interlayer to produce regulated lithium depositions. It is shown that lithium‐growth kinetics critically depend on the nature of the interlayer species, leading to distinct lithium‐deposition morphologies. Subsequently, the dynamic role of the interlayer in battery operation is discussed as a buffer and seed layer for lithium redistribution and precipitation, respectively, in tailoring lithium deposition. These findings broaden the understanding of the electrochemical lithium‐plating process at the solid‐electrolyte/lithium interface, highlight the importance of exploring various interlayers as a new avenue for regulating the lithium‐metal anode, and also offer insight into the nature of lithium growth in anode‐free solid‐state batteries.

Spherical Sn-carbon core-shell powder was synthesized through a resorcinol-formaldehyde ͑RF͒ microemulsion polymerization performed in the presence of hydrophobized Sn nanoparticles. The Sn-carbon core-shell structure was found to greatly enhance the cycle life compared to the mixture of Sn and spherical carbon when evaluated as the anode in lithium-ion batteries. A core-shell powder containing 20 wt % Sn showed 69% capacity retention at the 40th cycle when cycled between 0 and 2.0 V ͑vs Li/Li + ͒ at a constant current of 40 mA g −1. The mixture of 20 wt % Sn nanopowder and 80 wt % spherical carbon powder exhibited only 10% capacity retention in the same test condition. It is believed that the improved cyclability achieved with the core-shell powder is largely attributed to the inhibition of aggregation between Sn nanoparticles. The marginal polarization due to an intimate electrical contact made between Sn core and carbon shell is an additional advantageous feature achieved with this electrode.

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