Electrochemical sintering of lithium metal constrained by buffer layer in anode-free all-solid-state batteries

Anode-free all-solid-state lithium-metal batteries hold promise in energy density. However, they often suffer from rapid capacity decay, and the underlying mechanisms remain unclear, especially at high current densities. Here, failure mechanism is studied systematically for garnet solid electrolyte in Li anode-free all-solid-state batteries. By combining morphology evolution analysis and quantitative assessments, the decreased Coulombic efficiency for solid electrolyte at high current densities is attributed to large amounts of lump-shaped lithium deposits via the electrochemical sintering. The lump-shaped lithium deposits encapsulate numerous voids and solid electrolyte interphase leading to irreversible capacities. Furthermore, serious pulverization of lithium deposits is observed after long cycles. An addition of polydimethylsiloxane membrane is attempted to constrain electrochemical sintering of lithium and compact lithium metal deposits, leading to prolonged cycling performance.