Ether-Water Co-Solvent Electrolytes Enhanced Vanadium Oxide Cathode Cyclic Behaviors for Zinc Batteries

Vanadium-based compounds are fantastic cathodes for aqueous zinc metal batteries due to the high specific capacity and excellent rate capability. Nevertheless, the practical application has been hampered by the dissolution of vanadium in traditional aqueous electrolytes owing to the strong polarity of water molecules. Herein, we propose a hybrid electrolyte made of Zn(ClO4)2 salt in tetraethylene glycol dimethyl ether (G4) and H2O solvents to upgrade the cycle life of Zn//K0.486V2O5 battery. The G4 jointly solvates with Zn2+ ions and replaces a portion of the H2O molecules in the Zn2+ solvation sheath. It forms a strong bond with H2O, reducing its activity, and significantly inhibiting vanadium dissolution and water-induced parasitic reaction. Consequently, the optimized electrolyte with H2O and G4 volume ratio of 5 : 5 enhances the cycling stability of Zn//K0.486V2O5 battery, enabling it to reach up to 600 cycles. In addition, the battery demonstrates a satisfactory reversible capacity of 475.7 mAh g-1 and excellent rate performance attributed to the moderate ionic conductivity (28.8 mS cm-1) of the hybrid electrolyte. Last but not least, in the optimized electrolyte, the symmetric Zn//Zn cells deliver a long cycling performance of 400 h, while the asymmetric Zn//Cu cells shows a high average coulombic efficiency of 97.4 %.

Composite poly(ethylene oxide)-based solid electrolyte with consecutive and fast ion transport channels constructed by upper-dimensional MIL-53(Al) nanofibers

Novel structural designs for metal organic frameworks (MOFs) are expected to improve ion-transport behavior in composite solid electrolytes. Herein, upper-dimensional MIL-53(Al) nanofibers (MNFs, MIL-53 belongs to the MIL (Material Institute Lavoisier) group) with flower-like nanoflake structures have been designed and constructed via modified hydrothermal coordination. The optimized MNFs with high surface area and porosity can form abundant interfaces with poly(ethylene oxide) (PEO) matrix. The plasticization of MNFs to the PEO matrix will facilitate segmental movement of PEO chains to facilitate Li+ conduction. The unsaturated open metal centers of MNFs can effectively capture bis(trifluoromethanesulfonyl)imide anions (TFSI-) to deliver more free lithium ions for transfer. Moreover, the upper-dimensional nanofiber structure endows lithium ions with a long-range and consecutive transport pathway. The obtained composite solid electrolyte (MNFs@PEO) presents a high ionic conductivity of 4.1 × 10-4 S cm-1 and a great Li+ transference number of 0.4 at 60 °C. The electrolyte also exhibits a stable Li plating/stripping behavior over 1000 h at 0.1 mA cm-1 with inhibited Li dendrite growth. Furthermore, the Li/LiFePO4 and Li/LiNi0.8Mn0.1Co0.1O2 batteries with MNFs@PEO as electrolytes both display great cycling stabilities with high-capacity retention, indicating their potential applications in lithium metal batteries. The study will put forward new inspirations for designing advanced MOF-based composite solid electrolytes.

Engineering of heterointerface of ultrathin carbon nanosheet-supported CoN/MnO enhances oxygen electrocatalysis for rechargeable Zn-air batteries

Designing bifunctional electrocatalysts with outstanding reactivity and durability towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has remained a long-term aim for metal-air batteries. Achieving the high level of fusion between two distinct metal components to form bifunctional catalysts with optimized heterointerfaces and well-defined morphology holds noteworthy implications in the enhancement of electrocatalytic activity yet challenging. Herein, the fabrication of numerous heterointerfaces of CoN/MnO is successfully realized within ultrathin carbon nanosheets via a feasible self-templating synthesis strategy. Experimental results and theoretic calculations verify that the interfacial electron transfer from CoN to MnO at the heterointerface engenders an ameliorated charge transfer velocity, finely tuned energy barriers concerning reaction intermediates and ultimately accelerated reaction kinetics. The as-prepared CoN/MnO@NC demonstrates exceptional bifunctional catalytic performance, excelling in both OER and ORR showcasing a low reversible overpotential of 0.69 V. Furthermore, rechargeable liquid and quasi-solid-state flexible Zn-air batteries employing CoN/MnO@NC as the air-cathode deliver remarkable endurance and elevated power density, registering values of 153 and 116 mW cm-2 respectively and exceeding Pt/C + RuO2 counterparts and those reported in literature. Deeply exploring the effect of electron-accumulated heterointerfaces on catalytic activity would contribute wisdom to the development of bifunctional electrocatalysts for rechargeable metal-air batteries.

Cs2Mg(H2C3N3S3)4·8H2O: An Excellent Birefringent Material with Giant Optical Anisotropy in π-Conjugated Trithiocyanurate

The design of giant birefringence was performed by adjusting cations to make parallel and compact alignments of π-conjugated (H_xC₃N₃S₃)^x-3, where x = 1 and 2) groups with large polarizability anisotropy. Finally, the first mixed alkali/alkali-earth-metal trithiocyanurates, A₂B(H₂C₃N₃S₃)₄·nH₂O (A = K, Rb, Cs; B = Mg, Sr; n = 5-8, 12), were designed and synthesized successfully. Importantly, Cs₂Mg(H₂C₃N₃S₃)₄·8H₂O (III) and K₂Sr(H₂C₃N₃S₃)₄·5H₂O (IV) possess large birefringences of 0.580 and 0.194 at 800 nm, respectively, of III has the largest birefringence among all practical birefringent crystals, cyanurates, and hydroisocyanurates.

Recycling of Zinc-Carbon Batteries into MnO/ZnO/C to Fabricate Sustainable Cathodes for Rechargeable Zinc-Ion Batteries

Acidic zinc-carbon dry batteries have been widely used in life because of their low cost. However, a great quantity of used batteries is discarded as refuse, which not only wastes resources but also leads to environmental contamination. To reuse spent batteries on a large scale, this study concerns a simple, effective, and sustainable strategy to turn them into MnO/ZnO/C composites. After a conventional leaching treatment followed by pyrolysis, the rust cathode materials can be reduced to MnO/ZnO/C. When serving as a rechargeable zinc-ion battery cathode, this electrode provides a maximum reversible capacity of around 362 mAh g^-1 _MnO ) and a rate capability of 191 mAh g^-1 _MnO at a high current rate of 1.20 A g^-1 . Furthermore, ZnO gradually dissolves in the electrolyte with the increase of discharge cycles, replenishing the Zn²⁺ content in the electrolyte and further enhancing cycling stability (98.02 % after 500 cycles). The device also exhibits a remarkable energy density of 336.37 Wh kg^-1 , low self-discharge rate, and can efficiently power a LED panel. This strategy offers an economical and facile route to convert zinc-carbon battery waste into useful materials for aqueous rechargeable zinc ion batteries.

Lewis acid Mg2+-doped cobalt phosphate nanosheets for enhanced electrocatalytic oxygen evolution reaction

Cobalt-based materials are considered to be promising electrocatalysts for oxygen evolution reaction (OER). However, their catalytic efficiencies are still limited by sluggish surface adsorption and high activation overpotentials. Herein, Lewis...

Nitrogen-Doped Cobalt Pyrite Yolk-Shell Hollow Spheres for Long-Life Rechargeable Zn-Air Batteries

Limited by the sluggish four-electron transfer process, designing high-performance nonprecious electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is urgently desired for efficient rechargeable Zn-air batteries (ZABs). Herein, the successful synthesis of porous nitrogen-doped cobalt pyrite yolk-shell nanospheres (N-CoS2 YSSs) is reported. Benefiting from the abundant porosity of the porous yolk-shell structure and unique electronic properties by nitrogen doping, the as-prepared N-CoS2 YSSs possess more exposed active surface, thus giving rise to superior activity for reversible oxygen electrocatalysis and outstanding cycling stability (more than 165 h at 10 mA cm-2) in ZABs, exceeding the commercial Pt/C and RuO2 hybrid catalysts. Moreover, the assembled ZABs, delivering a specific capacity of 640 mAh gZn -1, can be used for practical devices. This work provides a novel tactic to engineer sulfides as high efficiency and promising bifunctional oxygen electrocatalysts for advanced metal-air batteries.

Powder exfoliated MoS2 nanosheets with highly monolayer-rich structures as high-performance lithium-/sodium-ion-battery electrodes

Due to their low yield and easy aggregation during the electrode preparation process, exfoliated MoS2 monolayers cannot fulfill the requirements of alkali-metal-ion battery tests. Hence, we have developed a facile process to fabricate powder exfoliated MoS2 nanosheets capable of large-scale production and having highly monolayer-rich structures. This process contains two steps: liquid-phase exfoliation of the edge-rich MoS2 precursor and a freeze-drying procedure. The proposed MoS2 precursors contain rich edge fractions that are easily exfoliated by this method, and the freeze-drying procedure can maintain the unique monolayer-rich structure of MoS2 in the powder phase. The electrochemical evaluations of both lithium- and sodium-ion batteries reveal that the proposed powder exfoliated monolayer-rich MoS2 electrode exhibits remarkable specific capacities and stable cyclic performances. In particular, the monolayer-rich MoS2 nanosheet electrode delivers a superior lithium-storage capacity of ∼1400 mA h g-1. The exfoliated MoS2 nanosheet electrode can withstand over 1000 cycles even at 1 A g-1. The mechanism reveals that these unique MoS2 nanosheets not only have a large surface area but also their inclusive monolayer structures exhibit much higher charge mobility than those of bulk MoS2.