Rechargeable aqueous Zn-ion batteries are attractive cheap, safe and green energy storage technologies but are bottlenecked by limitation in high-capacity cathode and compatible electrolyte to achieve satisfactory cyclability. Here we report the application of nonstoichiometric ZnMnO/carbon composite as a new Zn-insertion cathode material in aqueous Zn(CFSO) electrolyte. In 3 M Zn(CFSO) solution that enables ∼100% Zn plating/stripping efficiency with long-term stability and suppresses Mn dissolution, the spinel/carbon hybrid exhibits a reversible capacity of 150 mAh g and a capacity retention of 94% over 500 cycles at a high rate of 500 mA g. The remarkable electrode performance results from the facile charge transfer and Zn insertion in the structurally robust spinel featuring small particle size and abundant cation vacancies, as evidenced by combined electrochemical measurements, XRD, Raman, synchrotron X-ray absorption spectroscopy, FTIR, and NMR analysis. The results would enlighten and promote the use of cation-defective spinel compounds and trifluoromethanesulfonic electrolyte to develop high-performance rechargeable zinc batteries.

Electrochemical water splitting is a promising technology for sustainable conversion, storage, and transport of hydrogen energy. Searching for earth‐abundant hydrogen/oxygen evolution reaction (HER/OER) electrocatalysts with high activity and durability to replace noble‐metal‐based catalysts plays paramount importance in the scalable application of water electrolysis. A freestanding electrode architecture is highly attractive as compared to the conventional coated powdery form because of enhanced kinetics and stability. Herein, recent progress in developing transition‐metal‐based HER/OER electrocatalytic materials is reviewed with selected examples of chalcogenides, phosphides, carbides, nitrides, alloys, phosphates, oxides, hydroxides, and oxyhydroxides. Focusing on self‐supported electrodes, the latest advances in their structural design, controllable synthesis, mechanistic understanding, and strategies for performance enhancement are presented. Remaining challenges and future perspectives for the further development of self‐supported electrocatalysts are also discussed.

We report an aqueous Zn−V 2 O 5 battery chemistry employing commercial V 2 O 5 cathode, Zn anode, and 3 M Zn(CF 3 SO 3 ) 2 electrolyte. We elucidate the Zn-storage mechanism in the V 2 O 5 cathode to be that hydrated Zn 2+ can reversibly (de)intercalate through the layered structure. The function of the cointercalated H 2 O is revealed to be shielding the electrostatic interactions between Zn 2+ and the host framework, accounting for the enhanced kinetics. In addition, the pristine bulk V 2 O 5 gradually evolves into porous nanosheets upon cycling, providing more active sites for Zn 2+ storage and thus rendering an initial capacity increase. As a consequence, a reversible capacity of 470 mAh g −1 at 0.2 A g −1 and a long-term cyclability with 91.1% capacity rentention over 4000 cycles at 5 A g −1 are achieved. The combination of the good battery performance, safety, scalable materials synthesis, and facile cell assembly indicates this aqueous Zn−V 2 O 5 system is promising for stationary grid storage applications.

High-performance rechargeable Na/FeS2batteries showing only the intercalation reaction are obtained by selecting a NaSO3CF3/diglyme electrolyte and tuning the cut-off voltage to 0.8 V.