Search

Rechargeable Zn-MnO2 batteries with mild and nearly neutral aqueous electrolytes have shown great potential for large-scale energy storage because of their high safety, low cost, environmental friendliness and high energy density. However, MnO2 cathode materials usually have disadvantages such as low capacity and poor cycling stability, which limit the development of Zn-MnO2 batteries. In this study, mesoporous MnO2 nanospheres were prepared by in situ Mg ion pre-intercalation via a simple chemical method. The prepared MnO2 shows a high reversible capacity (247 mA h g−1 at 0.3 A g−1), excellent cycling stability (a capacity retention of 93% over 800 cycles at 0.8 A g−1) and good rate performance. The GITT, in situ EIS, ex situ XRD, ex situ XPS and ex situ SEM show that the zinc storage mechanism of MnO2 should be H+/Zn2+ co-intercalation/de-intercalation. This research could provide specific inspiration and promotion for the development and mechanism research of high-performance rechargeable Zn-MnO2 batteries. [ABSTRACT FROM AUTHOR]

The charged-state NiCl 2 -rGO aerogel cathode shows superior cycle performance in Na-NiCl 2 batteries. [Display omitted] • Charged-state NiCl 2 -rGO aerogels are prepared by freeze-drying methods. • Conductive rGO aerogels effectively improve the performance of NiCl 2. • The molar ratio of Ni/NaCl can be reduced to the stoichiometric ratio (0.5). • The NiCl 2 -rGO aerogel cathode shows excellent electrochemical performance. The hierarchical nickel chloride/reduced graphene oxide (NiCl 2 -rGO) aerogels are synthesized via a facile hydrothermal and freeze-drying methods using low-cost nickel chloride hexahydrate (NiCl 2 ·6H 2 O) as raw material. The NiCl 2 -rGO hybrid aerogel structure enables the uniform distribution of lamellar NiCl 2 on the three-dimensional (3D) cross-linked conductive graphene sheets. When employed as cathode for sodium-nickel chloride (Na-NiCl 2) batteries, the as-obtained NiCl 2 -rGO aerogels exhibit excellent electrochemical performance with high reversible capacities (116 mAh g−1 after 50 cycles, 128 mAh g−1 in a fixed capacity window (20%–80% state of charge (SOC)) after 50 cycles), and a ultra-low polarization (0.05 V in the fixed capacity window). The outstanding performance of NiCl 2 -rGO aerogels can be attributed to the excellent conductivity of graphene. Moreover, the strong contact between NiCl 2 and graphene sheets can effectively promote the transfer of electrons. Compared with traditional tubular Na-NiCl 2 batteries, the molar ratio of Ni/NaCl of NiCl 2 -rGO aerogels can be decreased from 1.8 to the stoichiometric ratio (0.5). To the best of our knowledge, this work paves a perspective way for the first time to develop charged-state NiCl 2 -based cathodes with splendid performance for Na-NiCl 2 batteries. [ABSTRACT FROM AUTHOR]