A Natural Casein-Based Separator with Brick-and-Mortar Structure for Stable, High-Rate Proton Batteries.

Rechargeable aqueous proton batteries with small organic molecule anodes are currently considered promising candidates for large-scale energy storage due to their low cost, stable safety, and environmental friendliness. However, the practical application is limited by the poor cycling stability caused by the shuttling of soluble organic molecules between electrodes. Herein, a cell separator is modified by a GO-casein-Cu2+ layer with a brick-and-mortar structure to inhibit the shuttling of small organic molecules. Experimental and calculation results indicate that, attributed to the synergistic effect of physical blocking of casein molecular chains and electrostatic and coordination interactions of Cu2+, bulk dissolution and shuttling of multiple small molecules can be inhibited simultaneously, while H+ transfer across the separators is not almost affected. With the protection of the GO-casein-Cu2+ separator, soluble small molecules, such as diquinoxalino[2,3-a:2',3'-c]phenazine,2,3,8,9,14,15-hexacyano (6CN-DQPZ) exhibit a high reversible capacity of 262.6 mA h g-1 and amazing stability (capacity retention of 92.9% after 1000 cycles at 1 A g-1). In addition, this strategy is also proved available to other active conjugated small molecules, such as indanthrone (IDT), providing a general green sustainable strategy for advancing the use of small organic molecule electrodes in proton cells.

Steric hindrance modulation of hexaazatribenzanthraquinone isomers for high-capacity and wide-temperature-range aqueous proton battery.

Organic materials with rich active sites are good candidates of high-capacity anodes in aqueous batteries, but commonly low utilization of active sites limits their capacity. Herein, two isomers, symmetric and asymmetric hexaazatribenzanthraquinone (s-HATBAQ and a-HATBAQ), with rich active sites have been synthesized in a controllable manner. It has been revealed for the first time that a sulfuric acid catalyst can facilitate the stereoselective formation of s-HATBAQ. Attributed to the reduced steric hindrance in favor of proton insertion as well as the amorphous structure conducive to electrochemical dynamics, s-HATBAQ exhibits 1.5 times larger specific capacity than a-HATBAQ. Consequently, the electrode of s-HATBAQ with 50% reduced graphene oxide (s-HATBAQ-50%rGO) delivers a record high specific capacity of 405 mAh g-1 in H2SO4 electrolyte. Moreover, the assembled MnO2//s-HATBAQ-50%rGO aqueous proton full batteries show an exceptional cycling stability at 25°C and can maintain ∼92% capacity after 1000 cycles at 0.5 A g-1 at -80°C. This work demonstrates the controllable synthesis of isomers, showcases a wide-temperature-range prototype proton battery and highlights the significance of precise molecular structure modulation in organic energy storage.

Fe Powder Catalytically Synthesized C3N3 toward High-Performance Anode Materials of Lithium-Ion Batteries.

Recently, carbon nitrides and their carbon-based derivatives have been widely studied as anode materials of lithium-ion batteries due to their graphite-like structure and abundant nitrogen active sites. In this paper, a layered carbon nitride material C3N3 consisting of triazine rings with an ultrahigh theoretical specific capacity was designed and synthesized by an innovative method based on Fe powder-catalyzed carbon-carbon coupling polymerization of cyanuric chloride at 260 °C, with reference to the Ullmann reaction. The structural characterizations indicated that the as-synthesized material had a C/N ratio close to 1:1 and a layered structure and only contained one type of nitrogen, suggesting the successful synthesis of C3N3. When used as a lithium-ion battery anode, the C3N3 material showed a high reversible specific capacity up to 842.39 mAh g-1 at 0.1 A g-1, good rate capability, and excellent cycling stability attributed to abundant pyridine nitrogen active sites, large specific surface area, and good structure stability. Ex situ XPS results indicated that Li+ storage relies on the reversible transformation of -C=N- and -C-N- groups as well as the formation of bridge-connected -C=C- bonds. To further optimize the performance, the reaction temperature was further increased to synthesize a series of C3N3 derivatives for the enhanced specific surface area and conductivity. The resulting derivative prepared at 550 °C showed the best electrochemical performance, with an initial specific capacity close to 900 mAh g-1 at 0.1 A g-1 and good cycling stability (94.3% capacity retention after 500 cycles at 1 A g-1). This work will undoubtedly inspire the further study of high-capacity carbon nitride-based electrode materials for energy storage.

Integrated Uniformly Microporous C4 N/Multi-Walled Carbon Nanotubes Composite Toward Ultra-Stable and Ultralow-Temperature Proton Batteries.

Benefiting from the proton's small size and ultrahigh mobility in water, aqueous proton batteries are regarded as an attractive candidate for high-power and ultralow-temperature energy storage devices. Herein, a new-type C4 N polymer with uniform micropores and a large specific surface area is prepared by sulfuric acid-catalyzed ketone amine condensation reaction and employed as the electrode of proton batteries. Multi-walled carbon nanotubes (MWCNT) are introduced to induce the in situ growth of C4 N, and reaped significantly enhanced porosity and conductivity, and thus better both room- and low-temperature performance. When coupled with MnO2 @Carbon fiber (MnO2 @CF) cathode, MnO2 @CF//C4 N-50% MWCNT full battery shows unprecedented cycle stability with a capacity retention of 98% after 11 000 cycles at 10 A g-1 and even 100% after 70 000 cycles at 20 A g-1 . Additionally, a novel anti-freezing electrolyte (5 m H2 SO4  + 0.5 m MnSO4 ) is developed and showed a high ionic conductivity of 123.2 mS cm-1 at -70 °C. The resultant MnO2 @CF//C4 N-50% MWCNT battery delivers a specific capacity of 110.5 mAh g-1 even at -70 °C at 1 A g-1 , the highest in all reported proton batteries under the same conditions. This work is expected to offer a package solution for constructing high-performance ultralow-temperature aqueous proton batteries.