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.

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c-LLZO) is a promising Li + ion conductor for applications as a ceramic solid electrolyte in next generation high safety lithium batteries. The sintering temperature of c-LLZO is usually higher than 1100 °C, where Li-loss is severe, especially in conventional air ambient sintering method. Covering the green body with "mother powder" is often adopted for compensating the Li-loss. The mother powder having the same composition as the green body cannot be repeatedly use, which raises the cost of the c-LLZO ceramics. A self-compensating Li-loss method without mother powder is proposed and investigated to prepare high-quality c-LLZO ceramics. In this method, excess lithium is added to c-LLZO green pellets to self-compensate Li-loss at high temperature. The impact of different amounts of excess Li and crucible material, such as Pt, MgO, Al 2 O 3 , and ZrO 2 is studied. With optimized such sintering method, Ta doped LLZO pellets with 10% excess Li can be well sintered inside low-cost MgO crucible without mother powder at 1250 °C for only 40 min and laboratory scale production is demonstrated. The ceramics have relative densities of ∼96%, conductivities of ∼6.47 × 10 −4 S cm −1 and critical current density of 1.15 mA cm −2 at 25 °C, which is fundamental for further researches on solid-state batteries.

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Lithium metal batteries using solid electrolytes are considered to be the next-generation lithium batteries due to their enhanced energy density and safety. However, interfacial instabilities between Li-metal and solid electrolytes limit their implementation in practical batteries. Herein, Li-metal batteries using tailored garnet-type Li7-xLa3-aZr2-bO12 (LLZO) solid electrolytes is reported, which shows remarkable stability and energy density, meeting the lifespan requirements of commercial applications. We demonstrate that the compatibility between LLZO and lithium metal is crucial for long-term stability, which is accomplished by bulk dopant regulating and dopant-specific interfacial treatment using protonation/etching. An all-solid-state with 5 mAh cm−2 cathode delivers a cumulative capacity of over 4000 mAh cm−2 at 3 mA cm−2, which to the best of our knowledge, is the highest cycling parameter reported for Li-metal batteries with LLZOs. These findings are expected to promote the development of solid-state Li-metal batteries by highlighting the efficacy of the coupled bulk and interface doping of solid electrolytes.