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.

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.

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.

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.

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 .

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.

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.

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.

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.

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.

Assembly of Nanofluidic MXene Fibers with Enhanced Ionic Transport and Capacitive Charge Storage by Flake Orientation.

MXenes are an emerging class of highly conductive two-dimensional (2D) materials with electrochemical storage features. Oriented macroscopic Ti3C2Tx fibers can be fabricated from a colloidal 2D nematic phase dispersion. The layered conductive Ti3C2Tx fibers are ideal candidates for constructing high-speed ionic transport channels to enhance the electrochemical capacitive charge storage performance. In this work, we assemble Ti3C2Tx fibers with a high degree of flake orientation by a wet spinning process with controlled spinning speeds and morphology of the spinneret. In addition to the effects of cross-linking of magnesium ions between Ti3C2Tx flakes, the electronic conductivity and mechanical strength of the as-prepared fibers have been improved to 7200 S cm-1 and 118 MPa, respectively. The oriented Ti3C2Tx fibers present a volumetric capacitive charge storage capability of up to 1360 F cm-3 even in a Mg-ion based neutral electrolyte, with contributions from both nanofluidic ion transport and Mg-ion intercalation pseudocapacitance. The oriented 2D Ti3C2Tx driven nanofluidic channels with great electronic conductivity and mechanical strength endows the MXene fibers with attributes for serving as conductive ionic cables and active materials for fiber-type capacitive electrochemical energy storage, biosensors, and potentially biocompatible fibrillar tissues.

3D-Printed Zn-Ion Hybrid Capacitor Enabled by Universal Divalent Cation-Gelated Additive-Free Ti3C2 MXene Ink.

The construction of aqueous Zn-ion hybrid capacitors (ZICs) reconciling high energy/power density is practically meaningful yet remains a grand challenge. Herein, a high-capacitance and long-life ZIC is demonstrated by 3D printing of a Ti3C2 MXene cathode, affording optimized carrier transport, facile electrolyte penetration, and ample porosity. The 3D-printable additive-free MXene ink with desirable rheological property is derived by a fast gelation process employing a trace amount of divalent cations, which overcomes the tedious post-treatments required for additive removal. The thus-fabricated 3D-printed (3DP) MXene cathode results in a dual-ion storage mechanism to synergize pseudocapacitive behavior of H+ and electrical double-layer capacitive behavior of Zn2+, which is systematically probed by a wide suite of in situ/ex situ electroanalytic characterizations. The 3DP MXene cathode accordingly exhibits a favorable areal capacitance of 1006.4 mF cm-2 at 0.38 mA cm-2 and excellent rate capability (184.4 F g-1 at 10 A g-1), outperforming the state-of-the-art ZICs. More impressively, ZIC full cells comprising a 3DP MXene cathode and a 3DP Zn anode deliver a competitive energy/power density of 0.10 mWh cm-2/5.90 mW cm-2 as well as an ultralong lifespan (86.5% capacity retention over 6000 cycles at 10 mA cm-2).

Directly Grown Vertical Graphene Carpets as Janus Separators toward Stabilized Zn Metal Anodes.

Zinc metal anode has garnered a great deal of scientific and technological interest. Nevertheless, major bottlenecks restricting its large-scale utilization lie in the poor electrochemical stability and unsatisfactory cycling life. Herein, a Janus separator is developed via directly growing vertical graphene (VG) carpet on one side of commercial glass fiber separator throughout chemical vapor deposition. A simple air plasma treatment further renders the successful incorporation of oxygen and nitrogen heteroatoms on bare graphene. Thus-derived 3D VG scaffold affording large surface area and porous structure can be viewed as a continuation of planar zinc anode. In turn, the Janus separator harvests homogenous electric field distribution and lowered local current density at the interface of the anode/electrolyte, as well as harnesses favorable zincophilic feature for building-up uniform Zn ionic flux. Such a separator engineering enables an impressive rate and cycle performance (93% over 5000 cycles at 5 A g-1 ) for Zn-ion hybrid capacitors and outstanding energy density (182 Wh kg-1 ) for V2 O5 //Zn batteries, respectively. This strategy with large scalability and cost-effectiveness represents a universal route to protect prevailing metal anodes (Zn, Na, K) in rechargeable batteries.

3D Crumpled Ultrathin 1T MoS2 for Inkjet Printing of Mg-Ion Asymmetric Micro-supercapacitors.

Metallic molybdenum disulfide (MoS2), e.g., 1T phase, is touted as a highly promising material for energy storage that already displays a great capacitive performance. However, due to its tendency to aggregate and restack, it remains a formidable challenge to assemble a high-performance electrode without scrambling the intrinsic structure. Here, we report an electrohydrodynamic-assisted fabrication of 3D crumpled MoS2 (c-MoS2) and its formation of an additive-free stable ink for scalable inkjet printing. The 3D c-MoS2 powders exhibited a high concentration of metallic 1T phase and an ultrathin structure. The aggregation-resistant properties of the 3D crumpled particles endow the electrodes with open space for electrolyte ion transport. Importantly, we experimentally discovered and theoretically validated that 3D 1T c-MoS2 enables an extended electrochemical stable working potential range and enhanced capacitive performance in a bivalent magnesium-ion aqueous electrolyte. With reduced graphene oxide (rGO) as the positive electrode material, we inkjet-printed 96 rigid asymmetric micro-supercapacitors (AMSCs) on a 4-in. Si/SiO2 wafer and 100 flexible AMSCs on photo paper. These AMSCs exhibited a wide stable working voltage of 1.75 V and excellent capacitance retention of 96% over 20 000 cycles for a single device. Our work highlights the promise of 3D layered materials as well-dispersed functional materials for large-scale printed flexible energy storage devices.

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.

3D Printing of NiCoP/Ti3C2 MXene Architectures for Energy Storage Devices with High Areal and Volumetric Energy Density.

Designing high-performance electrodes via 3D printing for advanced energy storage is appealing but remains challenging. In normal cases, light-weight carbonaceous materials harnessing excellent electrical conductivity have served as electrode candidates. However, they struggle with undermined areal and volumetric energy density of supercapacitor devices, thereby greatly impeding the practical applications. Herein, we demonstrate the in situ coupling of NiCoP bimetallic phosphide and Ti3C2 MXene to build up heavy NCPM electrodes affording tunable mass loading throughout 3D printing technology. The resolution of prints reaches 50 µm and the thickness of device electrodes is ca. 4 mm. Thus-printed electrode possessing robust open framework synergizes favorable capacitance of NiCoP and excellent conductivity of MXene, readily achieving a high areal and volumetric capacitance of 20 F cm-2 and 137 F cm-3 even at a high mass loading of ~ 46.3 mg cm-2. Accordingly, an asymmetric supercapacitor full cell assembled with 3D-printed NCPM as a positive electrode and 3D-printed activated carbon as a negative electrode harvests remarkable areal and volumetric energy density of 0.89 mWh cm-2 and 2.2 mWh cm-3, outperforming the most of state-of-the-art carbon-based supercapacitors. The present work is anticipated to offer a viable solution toward the customized construction of multifunctional architectures via 3D printing for high-energy-density energy storage systems.

Confining TiO2 Nanotubes in PECVD-Enabled Graphene Capsules Toward Ultrafast K-Ion Storage: In Situ TEM/XRD Study and DFT Analysis.

Titanium dioxide (TiO2) has gained burgeoning attention for potassium-ion storage because of its large theoretical capacity, wide availability, and environmental benignity. Nevertheless, the inherently poor conductivity gives rise to its sluggish reaction kinetics and inferior rate capability. Here, we report the direct graphene growth over TiO2 nanotubes by virtue of chemical vapor deposition. Such conformal graphene coatings effectively enhance the conductive environment and well accommodate the volume change of TiO2 upon potassiation/depotassiation. When paired with an activated carbon cathode, the graphene-armored TiO2 nanotubes allow the potassium-ion hybrid capacitor full cells to harvest an energy/power density of 81.2 Wh kg-1/3746.6 W kg-1. We further employ in situ transmission electron microscopy and operando X-ray diffraction to probe the potassium-ion storage behavior. This work offers a viable and versatile solution to the anode design and in situ probing of potassium storage technologies that is readily promising for practical applications.

Printable magnesium ion quasi-solid-state asymmetric supercapacitors for flexible solar-charging integrated units.

Wearable and portable self-powered units have stimulated considerable attention in both the scientific and technological realms. However, their innovative development is still limited by inefficient bulky connections between functional modules, incompatible energy storage systems with poor cycling stability, and real safety concerns. Herein, we demonstrate a flexible solar-charging integrated unit based on the design of printed magnesium ion aqueous asymmetric supercapacitors. This power unit exhibits excellent mechanical robustness, high photo-charging cycling stability (98.7% capacitance retention after 100 cycles), excellent overall energy conversion and storage efficiency (ηoverall = 17.57%), and outstanding input current tolerance. In addition, the Mg ion quasi-solid-state asymmetric supercapacitors show high energy density up to 13.1 mWh cm-3 via pseudocapacitive ion storage as investigated by an operando X-ray diffraction technique. The findings pave a practical route toward the design of future self-powered systems affording favorable safety, long life, and high energy.

Conductive and Catalytic VTe2@MgO Heterostructure as Effective Polysulfide Promotor for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are recognized as one of the most promising energy storage systems due to the high energy density and cost effectiveness. However, their practical implementation has still been handicapped due to notorious lithium polysulfide (LiPS) shuttle and depressed sulfur redox kinetics. It is therefore desirable to exploit key mediators synergizing electrical conductivity and electrocatalytic activity for the cathode. Herein, we report the employment of atmospheric pressure chemical vapor deposition to harness the efficient and controllable synthesis of metallic VTe2 over particulated MgO substrates, which has scarcely been demonstrated by conventional wet-chemical synthetic routes thus far. The thus-derived VTe2@MgO heterostructure as an efficient promotor enables effective regulation of LiPSs with respect to polysulfide capture/conversion and Li2S decomposition. As a result, a S/VTe2@MgO cathode with a sulfur loading of 1.6 mg cm-2 harvests long-term cyclability with a negligible capacity decay of 0.055% per cycle over 1000 cycles at 1.0 C. Even at a sulfur loading of 6.9 mg cm-2, the cathode still delivers electrochemical performances that can rival the state-of-the-art high-loading counterparts. Our work might offer a feasible solution for developing heterostructured promotors with multifunctionality and electrocatalytic activity for high-performance Li-S batteries.