Synchronous Dual Electrolyte Additive Sustains Zn Metal Anode with 5600†h Lifespan.

Despite conspicuous merits of Zn metal anodes, the commercialization is still handicapped by rampant dendrite formation and notorious side reaction. Manipulating the nucleation mode and deposition orientation of Zn is a key to rendering stabilized Zn anodes. Here, a dual electrolyte additive strategy is put forward via the direct cooperation of xylitol (XY) and graphene oxide (GO) species into typical zinc sulfate electrolyte. As verified by molecular dynamics simulations, the incorporated XY molecules could regulate the solvation structure of Zn2+ , thus inhibiting hydrogen evolution and side reactions. The self-assembled GO layer is in favor of facilitating the desolvation process to accelerate reaction kinetics. Progressive nucleation and orientational deposition can be realized under the synergistic modulation, enabling a dense and uniform Zn deposition. Consequently, symmetric cell based on dual additives harvests a highly reversible cycling of 5600 h at 1.0 mA cm-2 /1.0 mAh cm-2 .

Regulating the Inner Helmholtz Plane with a High Donor Additive for Efficient Anode Reversibility in Aqueous Zn-Ion Batteries.

The performance of aqueous Zn ion batteries (AZIBs) is highly dependent on inner Helmholtz plane (IHP) chemistry. Notorious parasitic reactions containing hydrogen evolution reactions (HER) and Zn dendrites both originate from abundant free H2 O and random Zn deposition inside active IHP. Here, we report a universal high donor number (DN) additive pyridine (Py) with only 1 vol. % addition (Py-to-H2 O volume ratio), for regulating molecule distribution inside IHP. Density functional theory (DFT) calculations and molecular dynamics (MD) simulation verify that incorporated Py additive could tailor Zn2+ solvation sheath and exclude H2 O molecules from IHP effectively, which is in favor of preventing H2 O decomposition. Consequently, even at extreme conditions such as high depth of discharge (DOD) of 80 %, the symmetric cell based on Py additive can sustain approximately 500 h long-term stability. This efficient strategy with high DN additives furnishes a promising direction for designing novel electrolytes and promoting the practical application of AZIBs, despite inevitably introducing trace organic additives.

Regulating Interfacial Ion Migration via Wool Keratin Mediated Biogel Electrolyte toward Robust Flexible Zn-Ion Batteries.

Aqueous Zn-ion batteries (ZIBs) have emerged as a promising energy supply for next-generation wearable electronics, yet they are still impeded by the notorious growth of zinc dendrite and uncontrollable side reaction. While the rational design of electrolyte composition or separator decoration can effectively restrain zinc dendrite growth, synchronously regulating the interfacial electrochemical performance by tackling the physical delamination venture between electrode and electrolyte remains a major obstacle for high-performance wearable aqueous ZIB. Herein, a category of hybrid biogel electrolyte containing carrageenan and wool keratin (CWK) is put forward to regulate the interfacial electrochemistry in aqueous ZIB. Systematic electrochemical kinetics analyses and ex situ scanning electrochemical microscopy (SECM) characterizations achieve comprehensive understanding of the keratin enhanced interfacial Zn2+ redox reaction. Thanks to the keratin triggered selective ion permeability, the as-designed CWK hybrid biogel electrolyte manifests a promoted Zn2+ transference number and excellent reversibility of Zn plating/stripping and outstanding Zn utilization (average Coulombic efficiency ≈98%). More impressively, the CWK hybrid biogel electrolyte also demonstrates cathode side-reaction depression and strengthened interfacial adhesion while assembled into a quasi-solid-state flexible ZIB. This work offers a strategy to synchronously solve concurrent challenges for both of Zn anode and cathode toward realistic wearable aqueous ZIB.

Precursor Customized Assembly of Wafer-Scale Polymerized Aniline Thin Films for Ultrasensitive NH3 Detection.

2D conducting polymer thin film recently has garnered numerous interests as a means of combining the molecular aggregate ordering and promoting in-plane charge transport for large-scale/flexible organic electronics. However, it remains far from satisfactory for conducting polymer chains to achieve desirable surface topography and crystallinity due to lack of control over the precursor-involved interfacial assembly. Herein, wafer-size polyaniline (PANI) and tetra-aniline thin films are developed via a controlled interfacial synthesis with customized surface morphology and crystallinity through two typical aniline precursors selective polymerization. Two crucial competing assembly mechanisms, a) direct interfacial polymerization, b) solution polymerization and subsequent interfacial assembly, are investigated to play a vital role in determining elemental chain length and aggregate architecture. The optimal PANI thin film manifests ultraflat surface topography and unambiguous crystalline domains, which also enabling fascinating ammonia sensing capability with 31.4% ppm-1 sensitivity, fast response time (88 s) with astonishing selectivity, repeatability, and recovery capability. The thus-demonstrated strategy with wafer-scale processing potential and flexible microdevice offers a promising route for large-scale manufacturing thin-film organic electronics.

ZIF-8@ZIF-67-Derived Nitrogen-Doped Porous Carbon Confined CoP Polyhedron Targeting Superior Potassium-Ion Storage.

Potassium ion batteries (KIB) have become a compelling energy-storage system owing to their cost effectiveness and the high abundance of potassium in comparison with lithium. However, its practical applications have been thwarted by a series of challenges, including marked volume expansion and sluggish reaction kinetics caused by the large radius of potassium ions. In line with this, the exploration of reliable anode materials affording high electrical conductivity, sufficient active sites, and structural robustness is the key. The synthesis of ZIF-8@ZIF-67 derived nitrogen-doped porous carbon confined CoP polyhedron architectures (NC@CoP/NC) to function as innovative KIB anode materials is reported. Such composites enable an outstanding rate performance to harvest a capacity of ≈200 mAh g-1 at 2000 mA g-1 . Additionally, a high cycling stability can be gained by maintaining a high capacity retention of 93% after 100 cycles at 100 mA g-1 . Furthermore, the potassium ion storage mechanism of the NC@CoP/NC anode is systematically probed through theoretical simulations and experimental characterization. This contribution may offer an innovative and feasible route of emerging anode design toward high performance KIBs.

Design and Mechanisms of Asymmetric Supercapacitors.

Ongoing technological advances in diverse fields including portable electronics, transportation, and green energy are often hindered by the insufficient capability of energy-storage devices. By taking advantage of two different electrode materials, asymmetric supercapacitors can extend their operating voltage window beyond the thermodynamic decomposition voltage of electrolytes while enabling a solution to the energy storage limitations of symmetric supercapacitors. This review provides comprehensive knowledge to this field. We first look at the essential energy-storage mechanisms and performance evaluation criteria for asymmetric supercapacitors to understand the wide-ranging research conducted in this area. Then we move to the recent progress made for the design and fabrication of electrode materials and the overall structure of asymmetric supercapacitors in different categories. We also highlight several key scientific challenges and present our perspectives on enhancing the electrochemical performance of future asymmetric supercapacitors.

The Effect of Water on Quinone Redox Mediators in Nonaqueous Li-O2 Batteries.

The parasitic reactions associated with reduced oxygen species and the difficulty in achieving the high theoretical capacity have been major issues plaguing development of practical nonaqueous Li-O2 batteries. We hereby address the above issues by exploring the synergistic effect of 2,5-di-tert-butyl-1,4-benzoquinone and H2O on the oxygen chemistry in a nonaqueous Li-O2 battery. Water stabilizes the quinone monoanion and dianion, shifting the reduction potentials of the quinone and monoanion to more positive values (vs Li/Li+). When water and the quinone are used together in a (largely) nonaqueous Li-O2 battery, the cell discharge operates via a two-electron oxygen reduction reaction to form Li2O2, with the battery discharge voltage, rate, and capacity all being considerably increased and fewer side reactions being detected. Li2O2 crystals can grow up to 30 µm, more than an order of magnitude larger than cases with the quinone alone or without any additives, suggesting that water is essential to promoting a solution dominated process with the quinone on discharging. The catalytic reduction of O2 by the quinone monoanion is predominantly responsible for the attractive features mentioned above. Water stabilizes the quinone monoanion via hydrogen-bond formation and by coordination of the Li+ ions, and it also helps increase the solvation, concentration, lifetime, and diffusion length of reduced oxygen species that dictate the discharge voltage, rate, and capacity of the battery. When a redox mediator is also used to aid the charging process, a high-power, high energy density, rechargeable Li-O2 battery is obtained.

Aluminum-Ion-Intercalation Supercapacitors with Ultrahigh Areal Capacitance and Highly Enhanced Cycling Stability: Power Supply for Flexible Electrochromic Devices.

Electrochemical capacitor systems based on Al ions can offer the possibilities of low cost and high safety, together with a three-electron redox-mechanism-based high capacity, and thus are expected to provide a feasible solution to meet ever-increasing energy demands. Here, highly efficient Al-ion intercalation into W18 O49 nanowires (W18 O49 NWs) with wide lattice spacing and layered single-crystal structure for electrochemical storage is demonstrated. Moreover, a freestanding composite film with a hierarchical porous structure is prepared through vacuum-assisted filtration of a mixed dispersion containing W18 O49 NWs and single-walled carbon nanotubes. The as-prepared composite electrode exhibits extremely high areal capacitances of 1.11-2.92 F cm-2 and 459 F cm-3 at 2 mA cm-2 , enhanced electrochemical stability in the Al3+ electrolyte, as well as excellent mechanical properties. An Al-ion-based, flexible, asymmetric electrochemical capacitor is assembled that displays a high volumetric energy density of 19.0 mWh cm-3 at a high power density of 295 mW cm-3 . Finally, the Al-ion-based asymmetric supercapacitor is used as the power source for poly(3-hexylthiophene)-based electrochromic devices, demonstrating their promising capability in flexible electronic devices.

Graphene-based materials for flexible supercapacitors.

The demand for flexible/wearable electronic devices that have aesthetic appeal and multi-functionality has stimulated the rapid development of flexible supercapacitors with enhanced electrochemical performance and mechanical flexibility. After a brief introduction to flexible supercapacitors, we summarize current progress made with graphene-based electrodes. Two recently proposed prototypes for flexible supercapacitors, known as micro-supercapacitors and fiber-type supercapacitors, are then discussed. We also present our perspective on the development of graphene-based electrodes for flexible supercapacitors.

Wet-spinning of carbon nanotube fibers: dispersion, processing and properties.

Owing to the intrinsic excellent mechanical, electrical, and thermal properties of carbon nanotubes (CNTs), carbon nanotube fibers (CNTFs) have been expected to become promising candidates for the next-generation of high-performance fibers. They have received considerable interest for cutting-edge applications, such as ultra-light electric wire, aerospace craft, military equipment, and space elevators. Wet-spinning is a broadly utilized commercial technique for high-performance fiber manufacturing. Thus, compared with array spinning from drawable CNTs vertical array and direct dry spinning from floating catalyst chemical vapor deposition (FCCVD), the wet-spinning technique is considered to be a promising strategy to realize the production of CNTFs on a large scale. In this tutorial review, we begin with a summative description of CNTFs wet-spinning process. Then, we discuss the high-concentration CNTs wet-spinning dope preparation strategies and corresponding non-covalent adsorption/charge transfer mechanisms. The filament solidification during the coagulation process is another critical procedure for determining the configurations and properties for derived CNTFs. Next, we discuss post-treatment, including continuous drafting and thermal annealing, to further optimize the CNTs orientation and compact configuration. Finally, we summarize the physical property-structure relationship to give insights for further performance promotion in order to satisfy the prerequisite for detailed application. Insights into propelling high-performance CNTFs production from lab-scale to industry-scale are proposed, in anticipation of this novel fiber having an impact on our lives in the near future.

Crystalline Texture Reengineering of Zinc Powder-Based Fibrous Anode for Remarkable Mechano-Electrochemical Stability.

The challenge of inadequate mechano-electrochemical stability in rechargeable fibrous Zn-ion batteries (FZIBs) has emerged as a critical challenge for their broad applications. Traditional rigid Zn wires struggle to maintain a stable electrochemical interface when subjected to external mechanical stress. To address this issue, a wet-spinning technique has been developed to fabricate Zn powder based fibrous anode, while carbon nanotubes (CNTs) introduced to enhance the spinnability of Zn powder dispersion. The followed annealing treatment has been conducted to reengineer the Zn crystalline texture with CNTs assisted surface tension regulation to redirect (002) crystallographic textural formation. The thus-derived annealed Zn@CNTs fiber demonstrates great mechano-electrochemical stability after a long-term bending and electrochemical process. The fabricated FZIB demonstrates a remarkable durability, surpassing 800 h at 1 mA cm-2 and 1 mAh cm-2, with a marginal voltage hysteresis increase of 21.7 mV even after 100 twisting cycles under 180 degree twisting angle. The assembled FZIB full cell displays an 88.6% capacity retention even after a long cycle of a series of bending, knotting, and straightening deformation. It has been also woven into a 200 cm2 size textile to demonstrate its capability to integrate into smart textiles.

Fabricating Ultrastrong Carbon Nanotube Fibers via a Microwave Welding Interface.

Liquid crystal wet-spun carbon nanotube fibers (CNTFs) offer notable advantages, such as precise alignment and scalability. However, these CNTFs usually suffer premature failure through intertube slippage due to the weak interfacial interactions between adjacent shells and bundles. Herein, we present a microwave (MW) welding strategy to enhance intertube interactions by partially carbonizing interstitial heterocyclic aramid polymers. The resulting CNTFs exhibit ultrahigh static tensile strength (6.74 ± 0.34 GPa) and dynamic tensile strength (9.52 ± 1.31 GPa), outperforming other traditional high-performance fibers. This work provides a straightforward yet effective approach to strengthening CNTFs for advanced engineering applications.

Carbon nanotube fibers with dynamic strength up to 14 GPa.

High dynamic strength is of fundamental importance for fibrous materials that are used in high-strain rate environments. Carbon nanotube fibers are one of the most promising candidates. Using a strategy to optimize hierarchical structures, we fabricated carbon nanotube fibers with a dynamic strength of 14 gigapascals (GPa) and excellent energy absorption. The dynamic performance of the fibers is attributed to the simultaneous breakage of individual nanotubes and delocalization of impact energy that occurs during the high-strain rate loading process; these behaviors are due to improvements in interfacial interactions, nanotube alignment, and densification therein. This work presents an effective strategy to utilize the strength of individual carbon nanotubes at the macroscale and provides fresh mechanism insights.

Stable zinc anode solid electrolyte interphase via inner Helmholtz plane engineering.

The inner Helmholtz plane and thus derived solid-electrolyte interphase (SEI) are crucial interfacial structure to determine the electrochemical stability of Zn-ion battery (ZIB). In this work, we demonstrate that introducing ß-cyclodextrins (CD) as anion-receptors into Zn(OTf)2 aqueous electrolyte could significantly optimize the Zn anode SEI structure for achieving stable ZIB. Specifically, ß-CD with macrocyclic structure holds appropriate cavity size and charge distribution to encase OTf- anions at the Zn metal surface to form ß-CD@OTf- dominated inner Helmholtz structure. Meanwhile, the electrochemically triggered ß-CD@OTf- decomposition could in situ convert to the organic-inorganic hybrid SEI (ZnF2/ZnCO3/ZnS‒(C-O-C/*CF/*CF3)), which could efficiently hinder the Zn dendrite growth with maintain the proper SEI mechanical strength stability to guarantee the long-term stability. The thus-derived Zn | |Zn pouch cell (21 cm2 size) with ß-CD-containing electrolyte exhibits a cumulative capacity of 6450 mAh-2 cm-2 at conditions of 10 mAh cm-2 high areal capacity. This work gives insights for reaching stable ZIB via electrolyte additive triggered SEI structure regulation.

Continuous production of ultratough semiconducting polymer fibers with high electronic performance.

Conjugated polymers have demonstrated promising optoelectronic properties, but their brittleness and poor mechanical characteristics have hindered their fabrication into durable fibers and textiles. Here, we report a universal approach to continuously producing highly strong, ultratough conjugated polymer fibers using a flow-enhanced crystallization (FLEX) method. These fibers exhibit one order of magnitude higher tensile strength (>200 megapascals) and toughness (>80 megajoules per cubic meter) than traditional semiconducting polymer fibers and films, outperforming many synthetic fibers, ready for scalable production. These fibers also exhibit unique strain-enhanced electronic properties and exceptional performance when used as stretchable conductors, thermoelectrics, transistors, and sensors. This work not only highlights the influence of fluid mechanical effects on the crystallization and mechanical properties of conjugated polymers but also opens up exciting possibilities for integrating these functional fibers into wearable electronics.

Manipulating Hierarchical Orientation of Wet-Spun Hybrid Fibers via Rheological Engineering for Zn-Ion Fiber Batteries.

Wet-spinning is a promising strategy to fabricate fiber electrodes for real commercial fiber battery applications, according to its great compatibility with large-scale fiber production. However, engineering the rheological properties of the electrochemical active materials to accommodate the viscoelasticity or liquid crystalline requirements for continuous wet-spinning remains a daunting challenge. Here, with entropy-driven volume-exclusion effects, the rheological behavior of vanadium pentoxide (V2 O5 ) nanowire dispersions is regulated through introducing 2D graphene oxide (GO) flakes in an optimal ratio. By optimizing the viscoelasticity and liquid-crystalline behavior of the spinning dope, the wet-spun hybrid fibers display controlled hierarchical orientation. The wet-spun V2 O5 /rGO hybrid fiber with the optimal 10:1 mass fraction (V2 O5 /rGO10:1 ) exhibits a highly oriented nanoblock arrangement, enabling efficient Zn-ion migration and an excellent Zn-ion storage capacity of 486.03 mAh g-1 at 0.1 A g-1 . A half-meter long quasi-solid-state fiber Zn-ion battery is assembled with a polyacrylamide gel electrolyte and biocompatible Ecoflex encapsulation. The thus-derived fiber Zn-ion battery is integrated into a wearable self-powered system, incorporating a highly efficient GaAs solar cell, which delivers a record-high overall efficiency (9.80%) for flexible solar charging systems.

Crystalline tetra-aniline with chloride interactions towards a biocompatible supercapacitor.

Recent advances in wearable and implantable electronics have increased the demand for biocompatible integrated energy storage systems. Conducting polymers, such as polyaniline (PANi), have been suggested as promising electrode materials for flexible biocompatible energy storage systems, based on their intrinsic structural flexibility and potential polymer chain compatibility with biological interfaces. However, due to structural disorder triggering insufficient electronic conductivity and moderate electrochemical stability, PANi still cannot fully satisfy the requirements for flexible and biocompatible energy storage systems. Herein, we report a biocompatible physiological electrolyte activated flexible supercapacitor encompassing crystalline tetra-aniline (c-TANi) as the active electrode material, which significantly enhances the specific capacitance and electrochemical cycling stability with chloride electrochemical interactions. The crystallization of TANi endows it with sufficient electronic conductivity (8.37 S cm-1) and a unique Cl- dominated redox charge storage mechanism. Notably, a fully self-healable and biocompatible supercapacitor has been assembled by incorporating polyethylene glycol (PEG) with c-TANi as a self-healable electrode and a ferric-ion cross-linked sodium polyacrylate (Fe3+-PANa)/0.9 wt% NaCl as a gel electrolyte. The as-prepared device exhibits a remarkable capacitance retention even after multiple cut/healing cycles. With these attractive features, the c-TANi electrode presents a promising approach to meeting the power requirements for wearable or implantable electronics.

Bcl-2 and Bax interact via the BH1-3 groove-BH3 motif interface and a novel interface involving the BH4 motif.

The interaction of Bcl-2 family proteins at the mitochondrial outer membrane controls membrane permeability and thereby the apoptotic program. The anti-apoptotic protein Bcl-2 binds to the pro-apoptotic protein Bax to prevent Bax homo-oligomerization required for membrane permeabilization. Here, we used site-specific photocross-linking to map the surfaces of Bax and Bcl-2 that interact in the hetero-complex formed in a Triton X-100 micelle as a membrane surrogate. Heterodimer-specific photoadducts were detected from multiple sites in Bax and Bcl-2. Many of the interaction sites are located in the Bcl-2 homology 3 (BH3) region of Bax and the BH1-3 groove of Bcl-2 that likely form the BH3-BH1-3 groove interface. However, other interaction sites form a second interface that includes helix 6 of Bax and the BH4 region of Bcl-2. Loss-of-function mutations in the BH3 region of Bax and the BH1 region of Bcl-2 disrupted the BH3-BH1-3 interface, as expected. Surprisingly the second interface was also disrupted by these mutations. Similarly, a loss-of-function mutation in the BH4 region of Bcl-2 that forms part of the second interface also disrupted both interfaces. As expected, both kinds of mutation abolished Bcl-2-mediated inhibition of Bax oligomerization in detergent micelles. Therefore, Bcl-2 binds Bax through two interdependent interfaces to inhibit the pro-apoptotic oligomerization of Bax.

Bax forms an oligomer via separate, yet interdependent, surfaces.

Interactions of Bcl-2 family proteins regulate permeability of the mitochondrial outer membrane and apoptosis. In particular, Bax forms an oligomer that permeabilizes the membrane. To map the interface of the Bax oligomer we used Triton X-100 as a membrane surrogate and performed site-specific photocross-linking. Bax-specific adducts were formed through photo-reactive probes at multiple sites that can be grouped into two surfaces. The first surface overlaps with the BH1-3 groove formed by Bcl-2 Homology motif 1, 2, and 3; the second surface is a rear pocket located on the opposite side of the protein from the BH1-3 groove. Further cross-linking experiments using Bax BH3 peptides and mutants demonstrated that the two surfaces interact with their counterparts in neighboring proteins to form two separated interfaces and that interaction at the BH1-3 groove primes the rear pocket for further interaction. Therefore, Bax oligomerization proceeds through a series of interactions that occur at separate, yet allosterically, coupled interfaces.

Niobium pentoxide based materials for high rate rechargeable electrochemical energy storage.

The demand for high rate energy storage systems is continuously increasing driven by portable electronics, hybrid/electric vehicles and the need for balancing the smart grid. Accordingly, Nb2O5 based materials have gained great attention because of their fast cation intercalation faradaic charge storage that endows them with high rate energy storage performance. In this review, we describe the crystalline features of the five main phases of Nb2O5 and analyze their specific electrochemical characteristics with an emphasis on the intrinsic ion intercalation pseudocapacitive behavior of T-Nb2O5. The charge storage mechanisms, electrochemical performance and state-of-the-art characterization techniques for Nb2O5 anodes are summarized. Next, we review recent progress in developing various types of Nb2O5 based fast charging electrode materials, including Nb2O5 based mixed metal oxides and composites. Finally, we highlight the major challenges for Nb2O5 based materials in the realm of high rate rechargeable energy storage and provide perspectives for future research.