All-solid-state and flexible supercapacitors have attracted tremendous attention due to the rapid development of modern smart and wearable electronics. In this study, copper and nickel co-coated ...cotton textile was developed as the substrate, on which tremella-like Ni–Co–S nanoflakes were electrochemically deposited. The obtained electrode exhibits high specific capacity with good rate capability, flexibility and bendability. An asymmetric supercapacitor cell containing Ni–Co–S as cathode, active carbon as anode and PVA/KOH as the solid-state electrolyte, demonstrate superior electrochemical properties for wearable energy storage applications. The obtained supercapacitor cell delivers a high energy density of 48.9 Wh kg−1 at 390 W kg−1. When four cells were connected in series, the connected cells can be safely operated at a wide voltage window of 0.0–6.4 V due to the good electrochemical stability and consistency of the assembled cells. These results demonstrated the flexible textile electrode developed by this work hold great potential for practical application in wearable energy storage devices.
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•Cu-sputtered textile with electroplated Ni layer was firstly used as collector fluid.•A flexible electrode was fabricated by electroplating Ni–Co–S onto conductive textile.•Obtained wearable supercapacitor delivers an energy density of 48.9 Wh kg−1 at 390 W kg−1.•A high voltage window of 0.0–6.4 V is safely achieved by connecting four cells in series.
As the drive to improve the cost, performance characteristics and safety of lithium-ion batteries increases with adoption, one area where significant value could be added is that of battery ...diagnostics. This paper documents an investigation into the use of plasmonic-based optical fibre sensors, inserted internally into 1.4 Ah lithium-ion pouch cells, as a real time and in-situ diagnostic technique. The successful implementation of the fibres inside pouch cells is detailed and promising correlation with battery state is reported, while having negligible impact on cell performance in terms of capacity and columbic efficiency. The testing carried out includes standard cycling and galvanostatic intermittent titration technique (GITT) tests, and the use of a reference electrode to correlate with the anode and cathode readings separately. Further observations are made around the sensor and analyte interaction mechanisms, robustness of sensors and suggested further developments. These finding show that a plasmonic-based optical fibre sensor may have potential as an opto-electrochemical diagnostic technique for lithium-ion batteries, offering an unprecedented view into internal cell phenomena.
Accurate modelling of particle shrinkage during biomass pyrolysis is key to the production of biochars with specific morphologies. Such biochars represent sustainable solutions to a variety of ...adsorption-dependent environmental remediation challenges. Modelling of particle shrinkage during biomass pyrolysis has heretofore been based solely on theory and ex-situ experimental data. Here we present the first in-situ phase-contrast X-ray imaging study of biomass pyrolysis. A novel reactor was developed to enable operando synchrotron radiography of fixed beds of pyrolysing biomass. Almond shell particles experienced more bulk shrinkage and less change in porosity than did walnut shell particles during pyrolysis, despite their similar composition. Alkaline pretreatment was found to reduce this difference in feedstock behaviour. Ex-situ synchrotron X-ray microtomography was performed to study the effects of pyrolysis on pore morphology. Pyrolysis led to a redistribution of pores away from particle surfaces, meaning newly formed surface area may be less accessible to adsorbates.
The next generation of automotive lithium‐ion batteries may employ NMC811 materials; however, defective particles are of significant interest due to their links to performance loss. Here, it is ...demonstrated that even before operation, on average, one‐third of NMC811 particles experience some form of defect, increasing in severity near the separator interface. It is determined that defective particles can be detected and quantified using low resolution imaging, presenting a significant improvement for material statistics. Fluorescence and diffraction data reveal that the variation of Mn content within the NMC particles may correlate to crystallographic disordering, indicating that the mobility and dissolution of Mn may be a key aspect of degradation during initial cycling. This, however, does not appear to correlate with the severity of particle cracking, which when analyzed at high spatial resolutions, reveals cracking structures similar to lower Ni content NMC, suggesting that the disconnection and separation of neighboring primary particles may be due to electrochemical expansion/contraction, exacerbated by other factors such as grain orientation that are inherent in such polycrystalline materials. These findings can guide research directions toward mitigating degradation at each respective length‐scale: electrode sheets, secondary and primary particles, and individual crystals, ultimately leading to improved automotive ranges and lifetimes.
High voltage operation of Ni‐rich cathodes can meet the rate and capacity demands of electric vehicles; however, degradation impedes practical application. This work reports that fabrication cracking is more severe at the cathode‐separator interface; variously sized secondary particles can experience operational cracking; even low cycle numbers can induce inter‐primary particle splitting; and crystal disorder may be linked to Mn mobility.
Nickel selenide and nickel nanoparticles integrated into a three-dimensional N-doped porous carbon matrix (NiSe/Ni/NC) have been developed as bi-functional electrocatalysts for highly efficient and ...stable water splitting. The structure of as-prepared NiSe/Ni/NC are characterized by scanning electron microscopy, transmission electron micrographs, X-ray photoelectron spectroscopy, N2 adsorption-desorption isotherms. In 1 M KOH electrolyte, as-prepared NiSe/Ni/NC delivers an overpotential of 77 mV for the hydrogen evolution reaction (HER) and 321 mV for the oxygen evolution reaction (OER) at the current density of 10 mA cm−2. During the OER, NiSe/Ni/NC exhibits a better electrocatalytic performance compared to the state-of-the-art RuO2. Furthermore, when NiSe/Ni/NC is used as the water splitting, the potential can reach 1.6 V at 10 mA cm−2. The high HER and OER catalytic activity of NiSe/Ni/NC originates from the mesoporous carbon matrix and synergetic effect between Ni, NiSe and the carbon matrix. In addition, when NiSe/Ni/NC is used as a bi-functional catalyst for HER and OER in alkaline media, it shows superior electrochemical performance to many other nickel selenide-based catalysts reported in the literature.
3D porous nickel selenide N-doped carbon as a robust electrocatalyst for overall water splitting was prepared via one-pot method using NaCl as template to form porous structure. Display omitted
•N-doped porous NiSe/carbon networks are developed as bifunctional catalysts for HER and OER.•NaCl is used to form the porous structure at high temperature.•The obtained NiSe/Ni/NC is used as bifunctional catalysts for water splitting.•NiSe/Ni/NC can produce a cell voltage of 1.60 V at 10 mA cm−2 in water electrolyzer with remarkable 25 h durability.
Optimizing the chemical and morphological parameters of lithium-ion (Li-ion) electrodes is extremely challenging, due in part to the absence of techniques to construct spatial and temporal ...descriptions of chemical and morphological heterogeneities. We present the first demonstration of combined high-speed X-ray diffraction (XRD) and XRD computed tomography (XRD-CT) to probe, in 3D, crystallographic heterogeneities within Li-ion electrodes with a spatial resolution of 1 μm. The local charge-transfer mechanism within and between individual particles was investigated in a silicon(Si)−graphite composite electrode. High-speed XRD revealed charge balancing kinetics between the graphite and Si during the minutes following the transition from operation to open circuit. Subparticle lithiation heterogeneities in both Si and graphite were observed using XRD-CT, where the core and shell structures were segmented, and their respective diffraction patterns were characterized.
•Review of fuel cell micro-CHP heat sources and dwelling heat demands.•Options for fuel cell heat recovery and integration with building services.•Multi-objective optimisation identified as ...recommended approach.
Fuel cells offer many benefits for residential micro-cogeneration because of their high electrical efficiency, low emissions, and low heat-to-power ratio. However, the current design of fuel cell micro combined heat and power (CHP) systems for dwellings can be improved by better matching of the heat generated by the plant with the dwelling’s load profile and heat emitters.
This paper explores the design options in building services using fuel cell micro-CHP and aims to bring the two research fields together in order to design superior integrated systems. Therefore a review of current literature on the field is performed and current available options for heat recovery from fuel cells, including the grades of heat available from different fuel cell process units are discussed. This is discussed in relation to the heat demand in a dwelling and the required temperature of the most suitable heat emitters for building services design. The paper motivates a methodology that considers all possible interconnections of plant in the design of fuel cell micro-CHP in dwellings and provides an example of how multi-objective optimisation can be used to identify promising system designs.
NiS1.23Se0.77 nanosheets closely attached to the internal surface of hollow mesoporous carbon sphere (HMCS) to form a NiS1.23Se0.77 nanosheets embedded in HMCS (NSSNs@HMCS) composite as the anode of ...sodium ion batteries (SIBs) is reported by a facile synthesis route. The anode exhibits a superior reversible capacity (520 mAh g−1 at 0.1 A g−1), impressive coulombic efficiency (CE) of up to 95.3%, a high rate capacity (353 mAh g−1 at 5.0 A g−1), excellent capacity retention at high current density (95.6%), and high initial coulombic efficiency (ICE) (95.1%). Firstly, the highest ICE for NiS2/NiSe2‐based anode can be ascribed to ultrathin layered structure of NiS1.23Se0.77 nanosheet and highly efficient electron transfer between the active material and HMCS. Secondly, the optimized NiS2/NiSe2 heterostructure at the nanoscale of the inside HMCS is formed after the first discharge/charge cycles, which can provide rich heterojunction interfaces/boundaries of sulfide/selenides to offer faster Na+ pathways, decrease the Na+ diffusion barriers, increase electronic conductivity, and limit the dissolution of polysulfides or polyselenides in the electrolyte. Finally, the hollow structure of the HMCS accommodates the volume expansion, prevents the pulverization and aggregation issues of composite materials, which can also promote outstanding electrochemical performance.
The optimized NiS2/NiSe2 heterostructure at the nanoscale on the inner surface of a hollow mesoporous carbon sphere is formed after the first discharge/charge cycles, which can provide rich heterojunction interfaces/boundaries of sulfide/selenides to offer faster Na+ pathways, decrease the Na+ diffusion barriers, increase electronic conductivity, and limit the dissolution of polysulfides or polyselenides in the electrolyte.
Sodium super‐ionic conductor (NASICON)‐structured phosphates are emerging as rising stars as cathodes for sodium‐ion batteries. However, they usually suffer from a relatively low capacity due to the ...limited activated redox couples and low intrinsic electronic conductivity. Herein, a reduced graphene oxide supported NASICON Na3Cr0.5V1.5(PO4)3 cathode (VC/C‐G) is designed, which displays ultrafast (up to 50 C) and ultrastable (1 000 cycles at 20 C) Na+ storage properties. The VC/C‐G can reach a high energy density of ≈470 W h kg−1 at 0.2 C with a specific capacity of 176 mAh g−1 (equivalent to the theoretical value); this corresponds to a three‐electron transfer reaction based on fully activated V5+/V4+, V4+/V3+, V3+/V2+ couples. In situ X‐ray diffraction (XRD) results disclose a combination of solid‐solution reaction and biphasic reaction mechanisms upon cycling. Density functional theory calculations reveal a narrow forbidden‐band gap of 1.41 eV and a low Na+ diffusion energy barrier of 0.194 eV. Furthermore, VC/C‐G shows excellent fast‐charging performance by only taking ≈11 min to reach 80% state of charge. The work provides a widely applicable strategy for realizing multi‐electron cathode design for high‐performance SIBs.
Na super‐ionic conductor (NASICON)‐structured materials are promising cathode candidates for Na‐ion batteries. Nevertheless, multi‐electron reaction and fast‐charging performance are still difficult to achieve. Herein, the authors design a reduced graphene oxide supported Na3Cr0.5V1.5(PO4)3 with the fully activated redox reactions of V5+/V4+, V4+/V3+, and V3+/V2+. The as‐developed materials display high capacity, stability, and fast‐charging capability.
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