Room‐temperature Na‐ion batteries (NIBs) have recently attracted attention as potential alternatives to current Li‐ion batteries (LIBs). The natural abundance of sodium and the similarity between the electrochemical properties of NIBs and LIBs make NIBs well suited for applications requiring low cost and long‐term reliability. Here, the first successful synthesis of a series of Na3(VO1−x PO4)2F1+2x (0 ≤ x ≤ 1) compounds as a new family of high‐performance cathode materials for NIBs is reported. The Na3(VO1−x PO4)2F1+2x series can function as high‐performance cathodes for NIBs with high energy density and good cycle life, although the redox mechanism varies depending on the composition. The combined first‐principles calculations and experimental analysis reveal the detailed structural and electrochemical mechanisms of the various compositions in solid solutions of Na3(VOPO4)2F and Na3V2(PO4)2F3. The comparative data for the Na y (VO1−x PO4)2F1+2x electrodes show a clear relationship among V3+/V4+/V5+ redox reactions, Na+−Na+ interactions, and Na+ intercalation mechanisms in NIBs. The new family of high‐energy cathode materials reported here is expected to spur the development of low‐cost, high‐performance NIBs.

Large-scale electric energy storage is a key enabler for the use of renewable energy. Recently, the room-temperature Na-ion battery has been rehighlighted as an alternative low-cost technology for this application. However, significant challenges such as energy density and long-term stability must be addressed. Herein, we introduce a novel cathode material, Na1.5VPO4.8F0.7, for Na-ion batteries. This new material provides an energy density of ~600 Wh kg(-1), the highest value among cathodes, originating from both the multielectron redox reaction (1.2 e(-) per formula unit) and the high potential (~3.8 V vs Na(+)/Na) of the tailored vanadium redox couple (V(3.8+)/V(5+)). Furthermore, an outstanding cycle life (~95% capacity retention for 100 cycles and ~84% for extended 500 cycles) could be achieved, which we attribute to the small volume change (2.9%) upon cycling, the smallest volume change among known Na intercalation cathodes. The open crystal framework with two-dimensional Na diffusional pathways leads to low activation barriers for Na diffusion, enabling excellent rate capability. We believe that this new material can bring the low-cost room-temperature Na-ion battery a step closer to a sustainable large-scale energy storage system.

Lithium-ion batteries, which have been widely used to power portable electronic devices, are on the verge of being applied to new automobile applications. To expand this emerging market, however, an electrode that combines fast charging capability, long-term cycle stability, and high energy density is needed. Herein, we report a novel layered lithium vanadium fluorophosphate, Li1.1Na0.4VPO4.8F0.7, as a promising positive electrode contender. This new material has two-dimensional lithium pathways and is capable of reversibly releasing and reinserting ~1.1 Li+ ions at an ideal 4 V (versus Li+/Li) to give a capacity of ~156 mAh g−1 (energy density of 624 Wh kg−1). Moreover, outstanding capacity retentions of 98% and 96% after 100 cycles were achieved at 60°C and room temperature, respectively. Unexpectedly high rate capability was delivered for both charge and discharge despite the large particle size (a few microns), which promises further enhancement of power density with proper nano-engineering.

Yavuz and colleagues introduced a highly active catalyst for non-redox fixation of CO 2 into cyclic carbonates, a versatile product family with potential use in green polymers and solvents. The metal-free, heterogeneous imidazolinium network structure is easily made, scaled up, recycled, and inexpensive and provides quantitative selectivity and conversion yields over a wide substrate scope of epoxides.

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