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The sluggish ion diffusion and electrolyte freezing with volumetric changes limit the low‐temperature performance of rechargeable batteries. Herein, a high‐rate aqueous proton battery (APB) operated at and below −78 °C via a 62 wt% (9.5 m) H3PO4 electrolyte is reported. The APB is a rocking‐chair battery that operates with protons commuting between a Prussian blue cathode and an MoO3 anode. At −78 °C, the APB full cells exhibit stable cycle life for 450 cycles, high round‐trip efficiency of 85%, and appreciable power performance. The APB delivers 30% of its room‐temperature capacity even at −88 °C. The proton storage mechanism is investigated by ex situ synchrotron XRD, XAS, and XPS. The APB pouch cells demonstrate no capacity fading at −78 °C, and thus offers a safe and reliable candidate for high‐latitude applications. [ABSTRACT FROM AUTHOR]

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 I2/[ZnIx(OH2)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 [ZnIx(OH2)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. [ABSTRACT FROM AUTHOR]

We report reversible electrochemical insertion of NO3− into manganese(II, III) oxide (Mn3O4) as a cathode for aqueous dual‐ion batteries. Characterization by TGA, FTIR, EDX, XANES, EXAFS, and EQCM collectively provides unequivocal evidence that reversible oxidative NO3− insertion takes place inside Mn3O4. Ex situ HRTEM and corresponding EDX mapping results suggest that NO3− insertion de‐crystallizes the structure of Mn3O4. Kinetic studies reveal fast migration of NO3− in the Mn3O4 structure. This finding may open a new direction for novel low‐cost aqueous dual‐ion batteries. The dual in the crown: Electrochemical quartz crystal microbalance measurement reveals the reversible insertion of nitrate into Mn3O4 which can be used as a cathode in aqueous dual‐ion batteries. Its capacity is one of the highest for anion‐storage cathode materials, higher than graphite and comparable to p‐type polymers. [ABSTRACT FROM AUTHOR]

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' NH4-ion battery of the full-cell configuration by employing an ammonium Prussian white analogue, (NH4)1.47Ni[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 (NH4)2SO4 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 NH4+ in these electrodes point to a new paradigm of NH4+-based energy storage. [ABSTRACT FROM AUTHOR]

Iron ion batteries using Fe 2+ as a charge carrier have yet to be widely explored, and they lack high-performing Fe 2+ hosting cathode materials to couple with the iron metal anode. Here, it is demonstrated that VOPO 4 ∙2H 2 O can reversibly host Fe 2+ with a high specific capacity of 100 mAh g -1 and stable cycling performance, where 68% of the initial capacity is retained over 800 cycles. In sharp contrast, VOPO 4 ∙2H 2 O's capacity of hosting Zn 2+ fades precipitously over tens of cycles. VOPO 4 ∙2H 2 O stores Fe 2+ with a unique mechanism, where upon contacting the electrolyte by the VOPO 4 ∙2H 2 O electrode, Fe 2+ ions from the electrolyte get oxidized to Fe 3+ ions that are inserted and trapped in the VOPO 4 ∙2H 2 O structure in an electroless redox reaction. The trapped Fe 3+ ions, thus, bolt the layered structure of VOPO 4 ∙2H 2 O, which prevents it from dissolution into the electrolyte during (de)insertion of Fe 2+ . The findings offer a new strategy to use a redox-active ion charge carrier to stabilize the layered electrode materials., (© 2021 Wiley-VCH GmbH.)

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.)