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.

No abstract

The solid electrolyte interphase (SEI), a complex layer that forms over the surface of electrodes exposed to battery electrolyte, has a central influence on the structural evolution of the electrode during battery operation. For lithium metallic anodes, tailoring this SEI is regarded as one of the most effective avenues for ensuring consistent cycling behavior, and thus practical efficiencies. While fluoride‐rich interphases in particular seem beneficial, how they alter the structural dynamics of lithium plating and stripping to promote efficiency remains only partly understood. Here, operando liquid‐cell transmission electron microscopy is used to investigate the nanoscale structural evolution of lithium electrodeposition and dissolution at the electrode surface across fluoride‐poor and fluoride‐rich interphases. The in situ imaging of lithium cycling reveals that a fluoride‐rich SEI yields a denser Li structure that is particularly amenable to uniform stripping, thus suppressing lithium detachment and isolation. By combination with quantitative composition analysis via mass spectrometry, it is identified that the fluoride‐rich SEI suppresses overall lithium loss through drastically reducing the quantity of dead Li formation and preventing electrolyte decomposition. These findings highlight the importance of appropriately tailoring the SEI for facilitating consistent and uniform lithium dissolution, and its potent role in governing the plated lithium's structure.

Lithium-rich disordered rocksalts such as Li 1.3 Nb 0.3 Mn 0.4 O 2 and Li 2 MnO 2 F are being investigated as high energy density cathodes for next generation Li-ion batteries. They can support the (de) lithiation of lithium ions over large compositional ranges while preserving the same overall structure. Here, we present a new Ni-rich oxyfluoride cathode, Li 2 NiO 2 F, with a disordered rocksalt structure. Li 2 NiO 2 F and can deliver a discharge capacity of 200 mAh g −1 at an average voltage of 3.2 V.