Lithium dendrite (filament) propagation through ceramic electrolytes, leading to short-circuits at high rates of charge, is one of the greatest barriers to realising high energy density all-solidstate lithium anode batteries. Utilising in-situ X-ray computed tomography coupled with spatially mapped X-ray diffraction, the propagation of cracks and the propagation of lithium dendrites through the solid electrolyte have been tracked in a Li/Li6PS5Cl/Li cell as a function of the charge passed. On plating, cracking initiates with spallation, conical "pothole"-like cracks that form in the ceramic electrolyte near the surface with the plated electrode. The spallations form predominantly at the lithium electrode edges where local fields are high. Transverse cracks then propagate from the spallations across the electrolyte from the plated to the stripped electrode. Lithium ingress drives the propagation of the spallation and transverse cracks by widening the crack from the rear, i.e. the crack front propagates ahead of the Li. As a result, cracks traverse the entire electrolyte before the Li arrives at the other electrode and therefore before a short-circuit occurs.

attractive for future grid-level energy storage applications. Metallic Zn, as the ideal anode for AZBs, has the highest theoretical capacity (5851 mAh mL −1 ). It is also non-toxic, non-flammable, abundant, and has good electrical conductivity and water stability. [1][2][3][4][5] However, conventional metallic Zn anodes suffer from severe dendrite formation during cycling, causing serious problems like poor reversibility, voltage hysteresis, increased parasitic reactions, shorting-induced battery failures, and other issues. [1,3,6] These dendritic structures, either rarefied needle, or non-planar platelet deposits, preferentially form at irregular or defective areas of the electrode where the localized current density is highest and the initial nucleation event is most likely, [7] and is exacerbated by cycling at high current densities and capacities. [8,9] Strategies for controlling and suppressing dendritic growth have revolved around manipulating the electrolyte, typically by inclusion of additives, [10][11][12][13][14][15] or by engineering the electrode into a high-surface-area sponge, [16][17][18] or with a protective surface coating, [19] in order to suppress dendrite formation.Despite being one of the most promising candidates for grid-level energy storage, practical aqueous zinc batteries are limited by dendrite formation, which leads to significantly compromised safety and cycling performance. In this study, by using single-crystal Zn-metal anodes, reversible electrodeposition of planar Zn with a high capacity of 8 mAh cm −2 can be achieved at an unprecedentedly high current density of 200 mA cm −2 . This dendrite-free electrode is well maintained even after prolonged cycling (>1200 cycles at 50 mA cm −2 ). Such excellent electrochemical performance is due to single-crystal Zn suppressing the major sources of defect generation during electroplating and heavily favoring planar deposition morphologies. As so few defect sites form, including those that would normally be found along grain boundaries or to accommodate lattice mismatch, there is little opportunity for dendritic structures to nucleate, even under extreme plating rates. This scarcity of defects is in part due to perfect atomic-stitching between merging Zn islands, ensuring no defective shallow-angle grain boundaries are formed and thus removing a significant source of non-planar Zn nucleation. It is demonstrated that an ideal high-rate Zn anode should offer perfect lattice matching as this facilitates planar epitaxial Zn growth and minimizes the formation of any defective regions.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202202552.

All-solid-state batteries with a Li anode and ceramic electrolyte have the potential to deliver a step change in performance compared with today's Li-ion batteries 1,2 . However, Li dendrites (filaments) form on charging at practical rates, penetrate across the ceramic electrolyte leading to short-circuit and cell failure 3,4 . Previous models of dendrite penetration have generally focused on a single process for dendrite initiation and propagation, with Li driving the crack at its tip [5][6][7][8][9] . Here we show that initiation and propagation are separate processes.

Void formation at the Li/ceramic electrolyte interface of an all-solid-state battery on discharge results in high local current densities, dendrites on charge, and cell failure. Here, we show that such voiding is reduced at the Li/Li6PS5Cl interface at elevated temperatures, sufficient to increase the critical current before voiding and cell failure from <0.25 mA cm–2 at 25 °C to 0.25 mA cm–2 at 60 °C and 0.5 mA cm–2 at 80 °C under a relatively low stack-pressure of 1 MPa. Increasing the stack-pressure to 5 MPa and temperature to 80 °C permits stable cycling at 2.5 mA cm–2. It is also shown that the charge-transfer resistance at the Li/Li6PS5Cl interface depends on pressure and temperature, with relatively high pressures required to maintain low charge-transfer resistance at −20 °C. These results are consistent with the plastic deformation of Li metal dominating the performance of the Li anode, posing challenges for the implementation of solid-state cells with Li anodes.