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.

Spinels with the formula of ABO (where A and B are metal ions) and the properties of magnetism, optics, electricity, and catalysis have taken significant roles in applications of data storage, biotechnology, electronics, laser, sensor, conversion reaction, and energy storage/conversion, which largely depend on their precise structures and compositions. In this review, various spinels with controlled preparations and their applications in oxygen reduction/evolution reaction (ORR/OER) and beyond are summarized. First, the composition and structure of spinels are introduced. Then, recent advances in the preparation of spinels with solid-, solution-, and vapor-phase methods are summarized, and new methods are particularly highlighted. The physicochemical characteristics of spinels such as their compositions, structures, morphologies, defects, and substrates have been rationally regulated through various approaches. This regulation can yield spinels with improved ORR/OER catalytic activities, which can further accelerate the speed, prolong the life, and narrow the polarization of fuel cells, metal-air batteries, and water splitting devices. Finally, the magnetic, optical, electrical, and catalytic applications beyond the OER/ORR are also discussed. The future applications of spinels are considered to be closely related to environmental and energy issues, which will be aided by the development of new species with precise preparations and advanced characterizations.

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.