Energetic Hypervalent Organoiodine Electrochemistry for Aqueous Zinc Batteries.

Hypervalent organoiodine compounds have been extensively utilized in organic synthesis, yet their electrochemical properties remain unexplored despite their theoretically high redox potential compared with inorganic iodine, which primarily relies on the I-/I0 redox couple in battery applications. Here, the fundamental redox mechanism of hypervalent organoiodine in a ZnCl2 aqueous electrolyte is established for the first time using the simplest iodobenzene (PhI) as a model compound. We validated that the PhI to PhICl2 transition is a single-step and reversible reaction, enabling two-electron transfer of I+/I3+ redox chemistry (1.9 V vs Zn2+/Zn) with high capacity (422 mAh giodine-1, and 262.6 mAh g-1 based on PhI) and high theoretical energy density (801.8 Wh kg-1). It was also elucidated that such organoiodine electrochemistry exhibits rich tunability in terms of the global reactivity of various PhI derivatives, including multiple iodine-substituted isomers and functional substituents. Additionally, the stabilizing anion ligands affect the reversibility and stability of trivalent organoiodine compounds. By limiting side reactions and improving the stability of trivalent organoiodine at low temperatures, the zinc-PhI battery demonstrated the feasibility of I+/I3+ conversion and sustained stable performance over 400 cycles. This work bridges the gap between hypervalent organoiodine chemistry and battery technology, highlighting the potential for future high-performance battery applications.

Molecule Engineering of Sugar Derivatives as Electrolyte Additives for Deep-Reversible Zn Metal Anode.

The cycling performance of zinc-ion batteries is greatly affected by dendrite formation and side reactions on zinc anode, particularly in scenarios involving high depth of discharge (DOD) and low negative/positive capacity (N/P) ratios in full cells. Herein, drawing upon principles of host-guest interaction chemistry, we investigate the impact of molecular structure of electrolyte additives, specifically the -COOH and -OH groups, on the zinc negative electrode through molecular design. Our findings reveal that molecules containing these groups exhibit strong adsorption onto zinc anode surfaces and chelate with Zn2+, forming a H2O-poor inner Helmholtz plane. This effectively suppresses side reactions and promotes dendrite-free zinc deposition of exposed (002) facets, enhancing stability and reversibility of an average coulombic efficiency of 99.89 % with the introduction of Lactobionic acid (LA) additive. Under harsh conditions of 92 % DOD, Zn//Zn cells exhibit stable cycling at challenging current densities of 15 mA ⋅ cm-2. Even at a low N/P ratio of 1.3, Zn//NH4V4O10 full cells with LA electrolyte exhibit high-capacity retention of 73 % after 300 cycles, significantly surpassing that of the blank electrolyte. Moreover, in a conversion type Zn//Br static battery with a high areal capacity (~5 mAh ⋅ cm-2), LA electrolyte sustains an improved cycling stability of 700 cycles.

Recycling Coal Fly Ash for Super-Thermal-Insulating Aerogel Fiber Preparation with Simultaneous Al2O3 Extraction.

A large quantity of coal fly ash is generated worldwide from thermal power plants, causing a serious environmental threat owing to disposal and storage problems. In this work, for the first time, coal fly ash is converted into advanced and novel aerogel fibers and high-purity α-Al2O3. Silica-bacterial cellulose composite aerogel fibers (CAFs) were synthesized using an in situ sol-gel process under ambient pressure drying. Due to the unique "nanoscale interpenetrating network" (IPN) structure, the CAFs showed wonderful mechanical properties with an optimum tensile strength of 5.0 MPa at an ultimate elongation of 5.8%. Furthermore, CAFs with a high porosity (91.8%) and high specific surface area (588.75 m2/g) can inherit advanced features, including excellent thermal insulation, stability over a wide temperature range, and hydrophobicity (contact angle of approximately 144°). Additionally, Al2O3 was simultaneously extracted from the coal fly ash to ensure that the coal fly ash was fully exploited. Overall, low-cost woven CAFs fabrics are suitable for wearable applications and offer a great approach to comprehensively use coal fly ash to address environmental threats.

An in situ electrospinning route to fabricate NiO-SnO2 based detectors for fast H2S sensing.

Hydrogen sulfide (H2S) is a toxic and flammable chemical, even in low concentration. In this study, an in situ electrospinning strategy was developed to directly deposit the sensitive materials of nickel oxide (NiO)-doped SnO2 nanofiber on alumina substrates, resulting in the fast H2S detection. The electrospun fiber could be deposited on to the alumina tube directly, and remain there during calcination. Using this method, the NiO-doped SnO2 nanofibers fabricated and manifested a fast response, fast recovery, and high selectivity at a low temperature (150 °C). A 15% atom NiO-doped SnO2 nanofiber-containing H2S detector presented a high response (1352), low response time (23 s), and low recovery time (38 s) while detecting a concentration of 50 ppm H2S at 150 °C. Compared to conventional methods, the H2S detector based on the in situ electrospinning method showed a higher sensitivity, faster response, and faster recovery. Furthermore, the superior performance of the detector can be ascribed to the thinner film and non-interrupted fiber structure. Additionally, the transformation of NiO to Ni3S2, confirmed by the x-ray photoelectron spectroscopy under a H2S atmosphere, suggested the main reason for the detector's high performance. The high performance of the NiO-doped SnO2 suggests a strategy for gas detectors, biodetectors, and semiconductor devices.

Aqueous Electrolyte With Weak Hydrogen Bonds for Four-Electron Zinc-Iodine Battery Operates in a Wide Temperature Range.

In the pursuit of high-performance energy storage systems, four-electron zinc-iodine aqueous batteries (4eZIBs) with successive I-/I2/I+ redox couples are appealing for their potential to deliver high energy density and resource abundance. However, susceptibility of positive valence I+ to hydrolysis and instability of Zn plating/stripping in conventional aqueous electrolyte pose significant challenges. In response, polyethylene glycol (PEG 200) is introduced as co-solvent in 2 m ZnCl2 aqueous solution to design a wide temperature electrolyte. Through a comprehensive investigation combining spectroscopic characterizations and theoretical simulations, it is elucidated that PEG disrupts the intrinsic strong H-bonds of water by global weak PEG-H2O interaction, which strengthens the O─H covalent bond of water and intensifies the coordination with Zn2+. This synergistic effect substantially reduces water activity to restrain the I+ hydrolysis, facilitating I-/I2/I+ redox kinetics, mitigating I3 - formation and smoothening Zn deposition. The 4eZIBs in the optimized hybrid electrolyte not only deliver superior cyclability with a low fading rate of 0.0009% per cycle over 20 000 cycles and a close-to-unit coulombic efficiency but also exhibit stable performance in a wide temperature range from 40 °C to -40 °C. This study offers valuable insights into the rational design of electrolytes for 4eZIBs.

Stabilized four-electron aqueous zinc-iodine batteries by quaternary ammonium complexation.

Four-electron aqueous zinc-iodine batteries (4eZIBs) leveraging the I-/I0/I+ redox couple have garnered attention for their potential high voltage, capacity, and energy density. However, the electrophilic I+ species is highly susceptible to hydrolysis due to the nucleophilic attack by water. Previous endeavors to develop 4eZIBs primarily relied on highly concentrated aqueous electrolytes to mitigate the hydrolysis issue, nonetheless, it introduced challenges associated with dissolution, high electrolyte viscosity, and sluggish electrode kinetics. In this work, we present a novel complexation strategy that capitalizes on quaternary ammonium salts to form solidified compounds with I+ species, rendering them impervious to solubilization and hydrolysis in aqueous environments. The robust interaction in this complexation chemistry facilitates a highly reversible I-/I0/I+ redox process, significantly improving reaction kinetics within a conventional ZnSO4 aqueous electrolyte. The proposed 4eZIB exhibits a superior rate capability and an extended lifespan of up to 2000 cycles. This complexation chemistry offers a promising pathway for the development of advanced 4eZIBs.

Hydrophobic Silk Fibroin-Agarose Composite Aerogel Fibers with Elasticity for Thermal Insulation Applications.

Aerogel fibers, characterized by their ultra-low density and ultra-low thermal conductivity, are an ideal candidate for personal thermal management as they hold the potential to effectively reduce the energy consumption of room heating and significantly contribute to energy conservation. However, most aerogel fibers have weak mechanical properties or require complex manufacturing processes. In this study, simple continuous silk fibroin-agarose composite aerogel fibers (SCAFs) were prepared by mixing agarose with silk fibroin through wet spinning and rapid gelation, followed by solvent replacement and supercritical carbon dioxide treatment. Among them, the rapid gelation of the SCAFs was achieved using agarose physical methods with heat-reversible gel properties, simplifying the preparation process. Hydrophobic silk fibroin-agarose composite aerogel fibers (HSCAFs) were prepared using a simple chemical vapor deposition (CVD) method. After CVD, the HSCAFs' gel skeletons were uniformly coated with a silica layer containing methyl groups, endowing them with outstanding radial elasticity. Moreover, the HSCAFs exhibited low density (≤0.153 g/cm3), a large specific surface area (≥254.0 m2/g), high porosity (91.1-94.7%), and excellent hydrophobicity (a water contact angle of 136.8°). More importantly, they showed excellent thermal insulation performance in low-temperature (-60 °C) or high-temperature (140 °C) environments. The designed HSCAFs may provide a new approach for the preparation of high-performance aerogel fibers for personal thermal management.

Woven Agarose-Cellulose Composite Aerogel Fibers with Outstanding Radial Elasticity for Personal Thermal Management.

Aerogel fibers are good thermal insulators, suitable for weaving, and show potential as the next generation of intelligent textiles that can effectively reduce heat consumption for personal thermal management. However, the production of continuous aerogel fibers from biomass with sufficient strength and radial elasticity remains a significant challenge. Herein, continuous gel fibers were produced via wet spinning using agarose (AG) as the matrix, 2,2,2,6,6-tetramethylpiperidine-1-oxyl radical-oxidized cellulose nanofibers (TOCNs) as the reinforcing agent, and no other chemical additives by utilizing the gelling properties of AG. Supercritical drying and chemical vapor deposition (CVD) were then used to produce hydrophobic AG-TOCN aerogel fibers (HATAFs). During CVD, the HATAF gel skeleton was covered with an isostructural silica coating. Consequently, the HATAFs can recover from radial compression under 60% strain. Moreover, the HATAFs have low densities (≤0.14 g cm-3), high porosities (≥91.8%), high specific surface areas (≥188 m2 g-1), moderate tensile strengths (≤1.75 MPa), excellent hydrophobicity (water contact angles of >130°), and good thermal insulating properties at different temperatures. Thus, HATAFs are expected to become a new generation of materials for efficient personal thermal management.

Stabilizing Zinc Anodes by a Uniform Nucleation Process with Cysteine Additive.

Zinc anodes in aqueous batteries face challenges such as dendrite growth and interfacial instability. This study investigates the use of cysteine as an electrolyte additive to address these issues. By establishing the correlation between the size of zinc nuclei and the surface tensions/contact angle at the electrolyte-anode interface, it is demonstrated that the addition of cysteine in the electrolyte alters the surface tensions/contact angle at the electrolyte-anode interface and the nucleation process of zinc. This alteration results in the formation of smaller and more dispersed nuclei, as opposed to the formation of larger island grains. This has a profound impact on the subsequent deposition growth process, enabling smooth and uniform zinc electrodeposition without the formation of dendrites. Additionally, cysteine molecules create a stable interface during zinc plating and stripping, effectively preventing corrosion from side reactions. The incorporation of cysteine in the electrolyte significantly enhances cycling stability and extends the lifespan of zinc anodes in aqueous batteries.

A twelve-electron conversion iodine cathode enabled by interhalogen chemistry in aqueous solution.

The battery chemistry aiming for high energy density calls for the redox couples that embrace multi-electron transfer with high redox potential. Here we report a twelve-electron transfer iodine electrode based on the conversion between iodide and iodate in aqueous electrolyte, which is six times than that of the conventional iodide/iodine redox couple. This is enabled by interhalogen chemistry between iodine (in the electrode) and bromide (in the acidic electrolyte), which provides an electrochemical-chemical loop (the bromide-iodate loop) that accelerates the kinetics and reversibility of the iodide/iodate electrode reaction. In the deliberately designed aqueous electrolyte, the twelve-electron iodine electrode delivers a high specific capacity of 1200 mAh g-1 with good reversibility, corresponding to a high energy density of 1357 Wh kg-1. The proposed iodine electrode is substantially promising for the design of future high energy density aqueous batteries, as validated by the zinc-iodine full battery and the acid-alkaline decoupling battery.

Unravelling rechargeable zinc-copper batteries by a chloride shuttle in a biphasic electrolyte.

The zinc-copper redox couple exhibits several merits, which motivated us to reconstruct the rechargeable Daniell cell by combining chloride shuttle chemistry in a zinc chloride-based aqueous/organic biphasic electrolyte. An ion-selective interface was established to restrict the copper ions in the aqueous phase while ensuring chloride transfer. We demonstrated that the copper-water-chloro solvation complexes are the descriptors, which are predominant in aqueous solutions with optimized concentrations of zinc chloride; thus, copper crossover is prevented. Without this prevention, the copper ions are mostly in the hydration state and exhibit high spontaneity to be solvated in the organic phase. The zinc-copper cell delivers a highly reversible capacity of 395 mAh g-1 with nearly 100% coulombic efficiency, affording a high energy density of 380 Wh kg-1 based on the copper chloride mass. The proposed battery chemistry is expandable to other metal chlorides, which widens the cathode materials available for aqueous chloride ion batteries.

Robust Silica-Agarose Composite Aerogels with Interpenetrating Network Structure by In Situ Sol-Gel Process.

Aerogels are three-dimensional nanoporous materials with outstanding properties, especially great thermal insulation. Nevertheless, their extremely high brittleness restricts their practical application. Recently, although the mechanical properties of silica aerogels have been improved by regulating the precursor or introducing a polymer reinforcer, these preparation processes are usually tedious and time-consuming. The purpose of this study was to simplify the preparation process of these composite aerogels. A silicic acid solution treated with cation exchange resin was mixed with agarose (AG) to gel in situ, and then composite aerogels (CAs) with an interpenetrating network (IPN) structure were obtained by aging and supercritical CO2 fluid (SCF) drying. Compared to previous works, the presented CAs preparation process is briefer and more environmentally friendly. Moreover, the CAs exhibit a high specific surface area (420.5 m2/g), low thermal conductivity (28.9 mW m-1 K-1), excellent thermal insulation properties, and thermal stability. These results show that these CAs can be better used in thermal insulation.

Silica-Bacterial Cellulose Composite Aerogel Fibers with Excellent Mechanical Properties from Sodium Silicate Precursor.

Forming fibers for fabric insulation is difficult using aerogels, which have excellent thermal insulation performance but poor mechanical properties. A previous study proposed a novel method that could effectively improve the mechanical properties of aerogels and make them into fibers for use in fabric insulation. In this study, composite aerogel fibers (CAFs) with excellent mechanical properties and thermal insulation performance were prepared using a streamlined method. The wet bacterial cellulose (BC) matrix without freeze-drying directly was immersed in an inorganic precursor (silicate) solution, followed by initiating in situ sol-gel reaction under the action of acidic catalyst after secondary shaping. Finally, after surface modification and ambient drying of the wet composite gel, CAFs were obtained. The CAFs prepared by the simplified method still had favorable mechanical properties (tensile strength of 4.5 MPa) and excellent thermal insulation properties under extreme conditions (220 °C and -60 °C). In particular, compared with previous work, the presented CAFs preparation process is simpler and more environmentally friendly. In addition, the experimental costs were reduced. Furthermore, the obtained CAFs had high specific surface area (671.3 m²/g), excellent hydrophobicity, and low density (≤0.154 g/cm3). This streamlined method was proposed to prepare aerogel fibers with excellent performance to meet the requirements of wearable applications.

Encapsulation of MoSe2 in carbon fibers as anodes for potassium ion batteries and nonaqueous battery-supercapacitor hybrid devices.

Potassium ion batteries (PIBs) are considered as promising alternatives to sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs), which can be ascribed to the rich abundance of potassium resources, low cost and high safety. Currently, the development of anode materials for PIBs is still confronted with many serious problems, such as low capacity and poor cycling performance. In this work, sheet-like MoSe2 implanted on the surfaces of carbon nanofibers is successfully synthesized through a simple electrospinning and selenization route. MoSe2/C-700 (selenization at 700 °C) maintains high structural stability and facilitates the intercalation/deintercalation of K+, which benefits from one-dimensional nanofibers with good structural stability and MoSe2 with an expanded interlayer spacing. As a whole, MoSe2/C-700 as an anode for PIBs shows a high reversible capacity of 316 mA h g-1 at 100 mA g-1 over 100 cycles. It also displays a specific capacity of 81 mA h g-1 at 100 mA g-1 over 100 cycles when it first serves as an electrode material for nonaqueous potassium-based battery-supercapacitor hybrid (BSH) devices.