A Honeycomb-like Ammonium-Ion Fiber Battery with High and Stable Performance for Wearable Energy Storage.

Aqueous ammonium-ion batteries have attracted intense interest lately as promising energy storage systems due to the price advantage and fast charge/discharge capability of ammonium-ion redox reactions. However, the research on the strength and energy storage characteristics of ammonium-ion fiber batteries is still limited. In this study, an ammonium-ion fiber battery with excellent mechanical strength, flexibility, high specific capacity, and long cycle-life has been developed with a robust honeycomb-like ammonium vanadate@carbon nanotube (NH4V4O10@CNT) cathode. The fiber electrode delivers a steady specific capacity of 241.06 mAh cm-3 at a current of 0.2 mA. Moreover, a fiber full cell consisting of an NH4V4O10@CNT cathode and a PANI@CNT anode exhibits a specific capacity of 7.27 mAh cm-3 at a current of 0.3 mA and retains a high capacity retention of 72.1% after 1000 cycles. Meanwhile, it shows good flexibility and superior electrochemical performance after 500 times bending or at different deformation states. This work offers a reference for long-cycle, flexible fibrous ammonium-ion batteries.

Independent of direct interspecies electron transfer: Magnetite-mediated sulphur cycle for anaerobic degradation of benzoate under low-concentration sulphate conditions.

The aim of this study was to investigate the primary mechanism of magnetite promoting anaerobic degradation of aromatic compounds under the low-concentration sulphate conditions. Under influent conditions of benzoate at 50 mM-chemical oxygen demand (COD) and sulphate at 15 mM, magnetite promoted benzoate degradation (77.1% vs 56.3%), while the effluent sulphate concentration was slightly higher than that without magnetite (1.6 mM vs 0.7 mM), inconsistent with functional gene prediction that both sulphate respiration and sulphur compound respiration were relatively more active in the presence of magnetite. Remarkably, X-ray diffraction showed that, signal related to Fe3O4 faded away and finally was replaced by FeSO4 and FeS, indicating that magnetite participated in benzoate degradation coupled to sulphate reduction via dissimilatory Fe(III) reduction. Further X-ray photoelectron spectroscopy showed that, signal related to S0 was only detected with magnetite, suggesting the possibility of re-oxidation of sulphide to elemental sulphur coupled to Fe(III) reduction. This was further supported by the increase in abundance of Desulfuromonas acetexigens capable of growing on Fe(III). In addition, magnetite specially enriched the chemolithotrophic sulphur-disproportionating microbes, Desulfovibrio aminophilus, which might proceed the disproportionation of elemental sulphur to sulphate and sulphide to achieve a sulphur cycle for benzoate degradation.

Roll-to-roll layer-by-layer assembly bark-shaped carbon nanotube/Ti3C2Tx MXene textiles for wearable electronics.

Smart wearable electronics have drawn increasing attention for their potential applications in personal thermal management, human health monitoring, portable energy conversion/storage, electronic skin and so on. However, it is still a critical challenge to fabricate the multifunctional textiles with tunable morphology and performance while performing well in flexibility, air permeability, wearing comfortability. Herein, we develop a novel roll-to-roll layer-by-layer assembly strategy to construct bark-shaped carbon nanotube (CNT)/Ti3C2Tx MXene composite film on the fiber surface. The fabricated bark-shaped CNT/MXene decorated fabrics (CMFs) exhibit good flexibility, air permeability and electrical conductivity (sheet resistance, 6.6 Ω/□). In addition, the CMFs demonstrate good electrothermal performance (70.9 °C, 5 V), electromagnetic interference (EMI) shielding performance (EMI shielding effectiveness, 30.0 dB under X-Brand), and high sensitivity as the flexible piezoresistive sensors for monitoring the human motions. Importantly, our CMFs show distinctive EMI shielding mechanism, where a great proportion of incident electromagnetic microwaves are reflected by the bark-shaped CNT/MXene films owing to the multi-interface scattering effects. This work may provide a new strategy for the fabrication of multifunctional textile-based electronics and pave the way for smart wearable electronics.

Vapor phase polymerized conducting polymer/MXene textiles for wearable electronics.

Multifunctional electronic textiles hold great potential applications in the wearable electronics field. However, it remains challenging to seamlessly integrate the multiple functions on the textile substrates without sacrificing their intrinsic properties. Herein, we report a novel and facile vapor phase polymerization (VPP) and spray-coating strategy towards the construction of a laminated film containing a PEDOT film and Ti3C2Tx MXene sheets on the fiber surface. The fabricated PEDOT/MXene decorated cotton fabrics are integrated with excellent electrochemical performance, joule heating performance, good electromagnetic interference (EMI) shielding, and strain sensing performance. The resultant multifunctional textiles have a low sheet resistance of 3.6 Ω sq-1, and the assembled all-solid-state fabric supercapacitors exhibit an ultrahigh specific capacitance of 1000.2 mF cm-2, which exceeds the state-of-the-art MXene-based fabric supercapacitors. In addition, the PEDOT/MXene modified fabrics exhibit an exceptional joule heating performance of 193.1 °C at the applied voltage of 12 V, high EMI shielding effectiveness of 36.62 dB, and high sensitivity as strain sensors for human motion detection. This work provides a novel strategy for the structure design of multifunctional textiles and will lay the foundation for the development of multifunctional wearable electronics.

A wearable fiber-shaped supercapacitor based on a poly(lactic acid) filament and high loading polypyrrole.

There is a growing interest in fiber-shaped supercapacitors, which are likely to meet the demands of wearable electronics. However, the loading of active material is so small that the energy density of fiber supercapacitors is low. In this research, a graphene oxide/poly(pyrrole) (GO/PPy) hybrid was applied as the active material and a novel method to accomplish a high loading of the active material on poly(lactic acid) (PLA) filaments is proposed. Iron ions, as positive ions, are intercalated into GO sheets to form complexes which can be absorbed on the surface of the PLA. Furthermore, iron ions can be used as initiators to initiate pyrrole polymerization. Using complexes in which iron ions are intercalated into GO, instead of pure GO, then coated onto PLA and then polymerized using pyrrole, this method could effectively increase the loading of PPy. As a result, the active material loading is 0.121 mg cm-1, and the weight gain rate even reached 72.4%. A high areal specific capacitance of 158.8 mF cm-2 and energy density of 3.5 µW h cm-2 are achieved using the proposed fiber-shaped supercapacitor. Meanwhile, it shows great potential for textile shaped electronics because of its fiber format.

Enhancing Electrochemical Performance of Graphene Fiber-Based Supercapacitors by Plasma Treatment.

Graphene fiber-based supercapacitors (GFSCs) hold high power density, fast charge-discharge rate, ultralong cycling life, exceptional mechanical/electrical properties, and safe operation conditions, making them very promising to power small wearable electronics. However, the electrochemical performance is still limited by the severe stacking of graphene sheets, hydrophobicity of graphene fibers, and complex preparation process. In this work, we develop a facile but robust strategy to easily enhance electrochemical properties of all-solid-state GFSCs by simple plasma treatment. We find that 1 min plasma treatment under an ambient condition results in 33.1% enhancement of areal specific capacitance (36.25 mF/cm2) in comparison to the as-prepared GFSC. The energy density reaches 0.80 µW h/cm2 in polyvinyl alcohol/H2SO4 gel electrolyte and 18.12 µW h/cm2 in poly(vinylidene difluoride)/ethyl-3-methylimidazolium tetrafluoroborate electrolyte, which are 22 times of that of as-prepared ones. The plasma-treated GFSCs also exhibit ultrahigh rate capability (69.13% for 40 s plasma-treated ones) and superior cycle stability (96.14% capacitance retention after 20 000 cycles for 1 min plasma-treated ones). This plasma strategy can be extended to mass-manufacture high-performance carbonaceous fiber-based supercapacitors, such as graphene and carbon nanotube-based ones.