No abstract

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 -ion battery of the full-cell configuration by employing an ammonium Prussian white analogue, (NH ) Ni[Fe(CN) ] , as the cathode, an organic solid, 3,4,9,10-perylenetetracarboxylic diimide (PTCDI), as the anode, and 1.0 m aqueous (NH ) SO 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 based on both electrodes' active mass, and excellent cycle life over 1000 cycles with 67 % capacity retention. Importantly, the topochemistry results of NH in these electrodes point to a new paradigm of NH -based energy storage.

The sluggish ion diffusion and electrolyte freezing with volumetric changes limit the low-T performance of rechargeable batteries. Herein, we report a high-rate aqueous proton battery (APB) operated at and below -78 o C via a 62 wt% (9.5 m) H 3 PO 4 electrolyte. The APB is a rocking-chair battery that operates with protons commuting between a Prussian blue cathode and a MoO 3 anode. At -78 o 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 o C. The proton storage mechanism is investigated by ex situ synchrotron XRD, XAS, and XPS. The APB pouch cells demonstrate nil capacity fading at -78 o C, which offers a safe and reliable candidate for high-latitude applications.

This study reveals the transport behavior of lattice water during proton (de)insertion in the structure of the hexagonal WO·0.6HO electrode. By monitoring the mass evolution of this electrode material via electrochemical quartz crystal microbalance, we discovered (1) WO·0.6HO incorporates additional lattice water when immersing in the electrolyte at open circuit voltage and during initial cycling; (2) The reductive proton insertion in the WO hydrate is a three-tier process, where in the first stage 0.25 H is inserted per formula unit of WO while simultaneously 0.25 lattice water is expelled; then in the second stage 0.30 naked H is inserted, followed by the third stage with 0.17 HO inserted per formula unit. Ex situ XRD reveals that protonation of the WO hydrate causes consecutive anisotropic structural changes: it first contracts along the c-axis but later expands along the ab planes. Furthermore, WO·0.6HO exhibits impressive cycle life over 20 000 cycles, together with appreciable capacity and promising rate performance.

Aqueous batteries represent promising solutions for large-scale energy storage considering the cost, safety, and performance. Despite the tremendous efforts devoted to the metal cations as charge carriers for batteries, scarce attention has been paid to the non-metal cations such as proton or ammonium. In this study, we report that a Berlin green framework exhibits much greater structural compatibility for NH4 + (de)­insertion than Na+ and K+. Ex situ structural studies reveal that the topochemistry of NH4 + in Berlin green is of nearly zero strain. The NH4 + topotactic performance gives rise to a higher operation potential and an ultralong cycling performance of 50,000 cycles with 78% capacity retention, far superior to Na+ and K+ (de)­insertion. Furthermore, we propose a double-ion battery, where the Berlin green cathode hosts NH4 + and sodium titanium phosphate NaTi2(PO4)3 accommodates Na+ during operation. Such a new system exhibits promising results in capacity and cycling life. Our results point to a new direction of expanding the battery chemistry with NH4 + as a charge carrier.

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.

No abstract

Aqueous rechargeable batteries are promising solutions for large-scale energy storage.S uchb atteries have the merit of lowc ost, innate safety,a nd environmental friendliness.T od ate,m ost knowna queous ion batteries employm etal cation charge carriers.H ere,w er eport 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 ,a st he cathode,a no rganic solid, 3,4,9,10-perylenetetracarboxylic diimide (PTCDI), as the anode,a nd 1.0 m aqueous (NH 4 ) 2 SO 4 as the electrolyte.T his novel aqueous ammonium-ion battery demonstrates encouraging electrochemical performance:a na verage operation voltage of ca. 1.0 V, an attractive energy density of ca. 43 Wh kg À1 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 anew paradigm of NH 4 + -based energy storage.