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Lattice‐oxygen redox in layered metal oxide cathodes offers a promising way to exploit high‐energy density sodium‐ion batteries. However, oxidation and reduction of lattice‐oxygen are always asymmetric, showing poor reversibility upon charging and discharging due to the activated oxygen loss and subsequent structural rearrangement. Here, a layered Na0.7[Li0.2Mn0.7Co0.1]O2 (NLMCO) is developed by balancing lattice‐oxygen activity and reversibility, which can deliver a record energy density of 729.7 Wh kg−1, further exceeding the state‐of‐the‐art Na0.75[Li0.25Mn0.75]O2 (NLMO, 638.4 Wh kg−1). In light of electron paramagnetic resonance spectroscopy, in situ differential electrochemical mass spectroscopy, and electrochemical testing results, the highly activated lattice‐oxygen is effectively stabilized in NLMCO without oxygen molecule release while obvious oxygen release is detected in the highly activated NLMO. Benefiting from the enhanced transition metal‐oxygen covalency and reduced band energy gap, the NLMCO electrode demonstrates simultaneously high lattice‐oxygen activity and reversibility, thus resulting in excellent rate and cycling performance, as well as ultra‐high energy density. The findings highlight the critical association of energy density and lattice‐oxygen redox reversibility, which will inspire more interest in anionic redox‐based high‐energy batteries. [ABSTRACT FROM AUTHOR]

The search for viable carbon‐neutral sources of renewable energy is one of the most critical challenges in science today. The chemical community is committed to seeking efficient, inexpensive, and sustainable electrocatalysts that can exploit the energy produced by sustainable energy resources. Here, an ethanol organocatalyst, which is green and cheap, that can efficiently catalyze the oxidation of Li2S in the electrochemical reactions of Li2S cathodes is identified. This study demonstrates that a multitude of small molecular organocatalysts will offer electrochemists an elegant tool for accelerating electrochemical reactions with otherwise unattainable efficiency and precision. This concept refashions electrochemical domains and has broad implications for the design of "green" and sustainable chemistry cycles. [ABSTRACT FROM AUTHOR]

The development of new insertion electrodes in sodium-ion batteries requires an in-depth understanding of the relationship between electrochemical performance and the structural evolution during cycling. To date in situ synchrotron X-ray and neutron diffraction methods appear to be the only probes of in situ electrode evolution at high rates, a critical condition for battery development. Here, the structural evolution of the recently synthesized O3-phase of Na2/3Fe2/3Mn1/3O2 is reported under relatively high current rates. The evolution of the phases, their lattice parameters, and phase fractions, and the sodium content in the crystal structure as a function of the charge/discharge process are shown. It is found that the O3-phase persists throughout the charge/discharge cycle but undergoes a series of two-phase and solid-solution transitions subtly modifying the sodium content and atomic positions but keeping the overall space-group symmetry (structural motif). In addition, for the first time, evidence of a structurally characterized region is shown that undergoes two-phase and solid-solution phase transitions simultaneously. The Mn/Fe-O bond lengths, c lattice parameter evolution, and the distance between the Mn/FeO6 layers are shown to concertedly change in a favorable manner for Na+ insertion/extraction. The exceptional electrochemical performance of this electrode can be related in part to the electrode maintaining the O3-phase throughout the charge/discharge process. [ABSTRACT FROM AUTHOR]

Solid Electrolytes: A New Lithium-Ion Conductor LiTaSiO5: Theoretical Prediction, Materials Synthesis, and Ionic Conductivity (Adv. Funct. In article number 1904232, Francesco Ciucci, Wei Kong Pang, Xin Guo, and co-workers design and synthesize a novel lithium-ion conductor LiTaSiO SB 5 sb , in which additional lithium ions are introduced into lattice sites of high energy through Zr-doping, thereby favoring the concerted motion of lithium ions and lowering the energy barrier for the ion transport. Concerted ion migration, ionic conductivity, LiTaSiO5, solid electrolytes. [Extracted from the article]