Solid Interhalogen Compounds with Effective Br0 Fixing for Stable High-energy Zinc Batteries.

Though massive efforts have been devoted to exploring Br-based batteries, the highly soluble Br2 /Br3 - species causing rigorous "shuttle effect", leads to severe self-discharge and low Coulombic efficiency. Conventionally, quaternary ammonium salts such as methyl ethyl morpholinium bromide (MEMBr) and tetrapropylammonium bromide (TPABr) are used to fix Br2 and Br3 - , but they occupy the mass and volume of battery without capacity contribution. Here, we report an all-active solid interhalogen compound, IBr, as a cathode to address the above challenges, in which the oxidized Br0 is fixed by iodine (I), thoroughly eliminating cross-diffusing Br2 /Br3 - species during the whole charging and discharging process. The Zn||IBr battery delivers remarkably high energy density of 385.8 Wh kg-1 , which is higher than those of I2 , MEMBr3 , and TPABr3 cathodes. Our work provides new approaches to achieve active solid interhalogen chemistry for high-energy electrochemical energy storage devices.

Manipulating Coulombic Efficiency of Cathodes in Aqueous Zinc Batteries by Anion Chemistry.

Electrolyte environments, including cations, anions, and solvents are critical for the performance delivery of cathodes of batteries. Most works focused on interactions between cations and cathode materials, in contrast, there is a lack of in-depth research on the correlation between anions and cathodes. Here, we systematically investigated how anions manipulate the coulombic efficiency (CE) of cathodes of zinc batteries. We take intercalation-type V2 O5 and conversion-type I2 cathodes as typical cases for profound studies. It was found that electronic properties of anions, including charge density and its distribution, can tune conversion or intercalation reactions, leading to significant CE differences. Using operando visual Raman microscopy and theoretical simulations, we confirm that competitive coordination between anions and I- can regulate CEs by modulating polyiodide diffusion rates in Zn-I2 cells. In Zn-V2 O5 cells, anion-tuned solvation structures vastly affect CEs through varying Zn2+ intercalation kinetics. Conversion I2 cathode achieves a 99 % CE with highly electron-donating anions, while anions with preferable charge structures that interact strongly with Zn2+ afford an intercalation V2 O5 a nearly 100 % CE. Understanding the mechanism of anion-governed CEs will help us evaluate compatibility of electrolytes with electrodes, thus providing a guideline for anion selection and electrolyte design for high-energy, long-cycling zinc batteries.

Fabrication and Characterization of MSQ Aerogel Coating on ePTFE Thin Films for Cable Sheaths.

With methylsilsesquioxane (MSQ) aerogels synthesized by the sol-gel method as a raw material and Si-Ti sol as a binder, an alcohol-based aerogel slurry consisting of only MSQ aerogel and Si-Ti sol was prepared and coated on expanded polytetrafluoroethylene (ePTFE) to form an MSQ aerogel coating layer, followed by low-temperature heat treatment. The effect of Si-Ti sol content on the microstructure of the MSQ aerogel coating layer was investigated, and the properties of a typical MSQ aerogel-layer-coated ePTFE film were evaluated. The results show that Si-Ti sol has an important role in terms of film-forming capability, surface smoothness, flexibility, and powder dropping of the MSQ aerogel coating layer. With a Si-Ti sol of 10.5 wt.% content as a binder and after heat treatment at 170 °C for 30 min, the coated ePTFE flexible thin film with a layer thickness of 30 µm shows high uniformity, integrity, and electrical insulation properties, with an elongation at break decrease over 130%, a thermal conductivity of 0.1753 W/(m·K) at 25 °C, a dielectric constant of 16.5674, and a dielectric loss of 0.06369, which can be promisingly applied in cable sheaths.

Electrolyte Additives for Stable Zn Anodes.

Zn-ion batteries are regarded as the most promising batteries for next-generation, large-scale energy storage because of their low cost, high safety, and eco-friendly nature. The use of aqueous electrolytes results in poor reversibility and leads to many challenges related to the Zn anode. Electrolyte additives can effectively address many such challenges, including dendrite growth and corrosion. This review provides a comprehensive introduction to the major challenges in and current strategies used for Zn anode protection. In particular, an in-depth and fundamental understanding is provided of the various functions of electrolyte additives, including electrostatic shielding, adsorption, in situ solid electrolyte interphase formation, enhancing water stability, and surface texture regulation. Potential future research directions for electrolyte additives used in aqueous Zn-ion batteries are also discussed.

Lean-water hydrogel electrolyte for zinc ion batteries.

Solid polymer electrolytes (SPEs) and hydrogel electrolytes were developed as electrolytes for zinc ion batteries (ZIBs). Hydrogels can retain water molecules and provide high ionic conductivities; however, they contain many free water molecules, inevitably causing side reactions on the zinc anode. SPEs can enhance the stability of anodes, but they typically possess low ionic conductivities and result in high impedance. Here, we develop a lean water hydrogel electrolyte, aiming to balance ion transfer, anode stability, electrochemical stability window and resistance. This hydrogel is equipped with a molecular lubrication mechanism to ensure fast ion transportation. Additionally, this design leads to a widened electrochemical stability window and highly reversible zinc plating/ stripping. The full cell shows excellent cycling stability and capacity retentions at high and low current rates, respectively. Moreover, superior adhesion ability can be achieved, meeting the needs of flexible devices.

Development of rechargeable high-energy hybrid zinc-iodine aqueous batteries exploiting reversible chlorine-based redox reaction.

The chlorine-based redox reaction (ClRR) could be exploited to produce secondary high-energy aqueous batteries. However, efficient and reversible ClRR is challenging, and it is affected by parasitic reactions such as Cl2 gas evolution and electrolyte decomposition. Here, to circumvent these issues, we use iodine as positive electrode active material in a battery system comprising a Zn metal negative electrode and a concentrated (e.g., 30 molal) ZnCl2 aqueous electrolyte solution. During cell discharge, the iodine at the positive electrode interacts with the chloride ions from the electrolyte to enable interhalogen coordinating chemistry and forming ICl3-. In this way, the redox-active halogen atoms allow a reversible three-electrons transfer reaction which, at the lab-scale cell level, translates into an initial specific discharge capacity of 612.5 mAh gI2-1 at 0.5 A gI2-1 and 25 °C (corresponding to a calculated specific energy of 905 Wh kgI2-1). We also report the assembly and testing of a Zn | |Cl-I pouch cell prototype demonstrating a discharge capacity retention of about 74% after 300 cycles at 200 mA and 25 °C (final discharge capacity of about 92 mAh).

Facile preparation of high conductive silver electrodes by dip-coating followed by quick sintering.

With polyol-synthesized silver nanoparticles (AgNPs) as raw materials, the silver electrodes with high conductivity were fabricated via a dip-coating method followed by sintering process, and the effects of the dip-coating and sintering process on the conductivity and surface roughness of silver electrodes were investigated in detail. The silver film with a thickness of 1.97 µm and a roughness of about 2 nm can be prepared after dip-coating at a pulling rate of 500 µm s-1 for 40 coating times. The non-conductive dip-coated silver films are transformed into conductive silver electrodes after conventional sintering in a muffle oven, infrared sintering and microwave sintering, respectively. Compared with high sintering temperature and long sintering time of conventional sintering and infrared sintering, microwave sintering can achieve quick sintering of silver films to fabricate high conductive silver electrodes. The silver electrodes with a sheet resistance of 0.75 Ω sq-1 and a surface roughness of less than 1 nm can be obtained after microwave sintering at 500 W for 50 s. The adjustable dip-coating method followed by quick microware sintering is an appropriate approach to prepare high conductive AgNPs-based electrodes for organic light-emitting diodes or other devices.

Fused silver nanowires with silica sol nanoparticles for smooth, flexible, electrically conductive and highly stable transparent electrodes.

Silver nanowires (AgNWs) thin films have emerged as promising next-generation transparent conductive electrodes (TCEs), and increasing the opto-electrical properties and long-term stability of AgNWs based TCEs is now a major research focus. In this work, a smooth, flexible, electrically conductive and highly stable transparent AgNWs-silica nanoparticles composite TCE has been successfully manufactured via coating an aqueous AgNWs-silica sol composite conductive ink on a PET substrate through the Mayer rod method. The effects of particle size and concentration of silica sol on the smoothness, opto-electrical properties and stability of AgNWs based TCEs were investigated in detail, and the mechanisms of the decoration of AgNWs by silica sol nanoparticles and welding of the network junction are discussed briefly. The TCE based on AgNWs reinforced with 50 nm silica nanoparticles (80 ppm concentration of silica sol) possesses a smooth surface with an RMS value of 9.45 nm, and superior opto-electrical properties with a sheet resistance of 28 Ω sq-1 and a transmittance of 97%. The resistance of the resultant AgNWs-silica composite TCE remains nearly constant after bending for 1000 cycles or exposure to Na2S solution for 300 s, indicating high stability. The newly designed AgNWs-silica composite TCE is a promising flexible and transparent electrode to be applied in next-generation flexible electronic devices.