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Plating battery electrodes typically deliver higher specific capacity values than insertion or conversion electrodes because the ion charge carriers represent the sole electrode active mass, and a host electrode is unnecessary. However, reversible plating electrodes are rare for electronically insulating nonmetals. Now, a highly reversible iodine plating cathode is presented that operates on the redox couples of I 2 /[ZnI x (OH 2 ) 4-x ] 2-x in a water-in-salt electrolyte. The iodine plating cathode with the theoretical capacity of 211 mAh g -1 plates on carbon fiber paper as the current collector, delivering a large areal capacity of 4 mAh cm -2 . Tunable femtosecond stimulated Raman spectroscopy coupled with DFT calculations elucidate a series of [ZnI x (OH 2 ) 4-x ] 2-x superhalide ions serving as iodide vehicles in the electrolyte, which eliminates most free iodide ions, thus preventing the consequent dissolution of the cathode-plated iodine as triiodides., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report reversible electrochemical insertion of NO 3 - into manganese(II, III) oxide (Mn 3 O 4 ) as a cathode for aqueous dual-ion batteries. Characterization by TGA, FTIR, EDX, XANES, EXAFS, and EQCM collectively provides unequivocal evidence that reversible oxidative NO 3 - insertion takes place inside Mn 3 O 4 . Ex situ HRTEM and corresponding EDX mapping results suggest that NO 3 - insertion de-crystallizes the structure of Mn 3 O 4 . Kinetic studies reveal fast migration of NO 3 - in the Mn 3 O 4 structure. This finding may open a new direction for novel low-cost aqueous dual-ion batteries., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Aqueous rechargeable batteries are promising solutions for large-scale energy storage. Such batteries have the merit of low cost, innate safety, and environmental friendliness. To date, most known aqueous ion batteries employ metal cation charge carriers. Here, we report the first "rocking-chair" NH 4 -ion battery of the full-cell configuration by employing an ammonium Prussian white analogue, (NH 4 ) 1.47 Ni[Fe(CN) 6 ] 0.88 , as the cathode, an organic solid, 3,4,9,10-perylenetetracarboxylic diimide (PTCDI), as the anode, and 1.0 m aqueous (NH 4 ) 2 SO 4 as the electrolyte. This novel aqueous ammonium-ion battery demonstrates encouraging electrochemical performance: an average operation voltage of ca. 1.0 V, an attractive energy density of ca. 43 Wh kg -1 based on both electrodes' active mass, and excellent cycle life over 1000 cycles with 67 % capacity retention. Importantly, the topochemistry results of NH 4 + in these electrodes point to a new paradigm of NH 4 + -based energy storage., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)