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The three-dimensional framework structure makes the ZnMn2O4 spinel an excellent host material for zinc ion intercalation and deintercalation processes. However, the high migration energy barrier of zinc ions from the tetrahedron 8a site to the octahedron 16c site in the ZnMn2O4 spinel framework limits its practical application for zinc-ion batteries. The focus of this work is to reduce the migration resistance of zinc ions by constructing cationic zinc vacancies in ZnMn2O4 (named Zn1−x□xMn2O4). The reasonable structure adjusted by alkaline etching is conducive to the diffusion of zinc ions. Combining the electrochemical tests and theoretical investigations, it was found that the introduction of zinc vacancies in the Zn1−x□xMn2O4 spinel framework caused the diffusion barrier of zinc ions to be reduced by approximately 0.4 eV compared to ZnMn2O4. In addition, the optimal Zn0.65□0.35Mn2O4 with 35% zinc vacancies was cross-linked by conductive carbon nanotubes (CNTs) to establish an excellent conducting network. The as-prepared Zn0.65□0.35Mn2O4/CNT composite exhibits a high reversible capacity of 479.3 mA h g−1 at 0.05 A g−1 with a good energy density of 640 W h kg−1 at 28 W kg−1. Our work is to convert the electrochemically poorly active traditional ZnMn2O4 spinel into a functionally active electrode for zinc-ion batteries. [ABSTRACT FROM AUTHOR]

Zinc-ion batteries are one of the promising energy storage devices, which have the advantages of environmental friendliness, high safety and low price and are expected to be used in large-scale battery application fields. However, four prominent water-induced adverse reactions, including zinc dendrite formation, zinc corrosion, passivation and the hydrogen evolution reaction in aqueous systems, seriously shorten the cycling life of zinc-ion batteries and greatly hinder their development. Based on this, polymer gel electrolytes have been developed to alleviate these issues due to their unique network structure, which can reduce water activity and suppress water-induced side reactions. Based on the challenges of polymer gel electrolytes, this review systematically summarizes the latest research progress in the use of additives in them and explores new perspectives in response to the existing problems with polymer electrolytes. In order to expand the performance of polymer gel electrolytes in zinc-ion batteries, a range of different types of additives are added via physical/chemical crosslinking, such as organic or inorganic substances, natural plants, etc. In addition, different types of additives and polymerization crosslinking from different angles essentially improve the ionic conductivity of the gel electrolyte, inhibit the growth of zinc dendrites, and reduce hydrogen evolution and oxygen-absorbed corrosion. After these modifications of polymer gel electrolytes, a more stable and superior electrochemical performance of zinc-ion batteries can be obtained, which provides some strategies for solid-state zinc-ion batteries. [ABSTRACT FROM AUTHOR]

The electrochemical performance of hybrid capacitors is seriously affected by the slow charging and discharging of the bulk phase. Here, Co-doped amorphous NiMoS4 modified with reduced graphene oxide (rGO) was prepared by a simple one-step hydrothermal method, and the obtained Co-doped NiMoS4/rGO nanocomposite (Ni1−xCoxMoS4/rGO) exhibits a high specific surface area, realizing the redox reaction from the bulk to the surface. Owing to the doping of Co with abundant redox active sites and the support of rGO sheets with high conductivity and a stable structure, the Ni1−xCoxMoS4/rGO anode assembled with an oxidized needle coke (NCO) cathode shows an excellent energy density of 28.9 W h kg−1 at a power density of 968.3 W kg−1. In addition, the hybrid supercapacitor displays a superior cycling performance with a capacity retention of 92.4% after 10 000 cycles. The construction of the Co-doped NiMoS4/rGO nanocomposite provides an effective strategy to boost the activity and stability of amorphous NiMoS4 for high-performance hybrid supercapacitors. [ABSTRACT FROM AUTHOR]

Silk fibroins (SFs) have many attractive properties; however, the practical applications of pure fibroin materials are severely restricted by their low elasticity. To improve flexibility of regenerated SF membranes, carboxyl-terminated polyethylene glycol (cPEG) was introduced into fibroin chains using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Subsequently, laccase-mediated graft polymerization of polypyrrole (PPy) onto the SF-g-cPEG membrane was performed to achieve electrical conductivity. The results implied that cPEG was successfully grafted onto the SF chains; the elongation at break of the SF-g-cPEG membrane increased by three times compared to that of the untreated one. Meanwhile, the introduced cPEG promoted the binding of pyrrole radical cations onto fibroin membrane, resulting in an efficient deposition of a PPy conductive layer during the laccase treatment. Conductivity of the membrane of SF-g-cPEG/PPy meets the standard of conductive materials even after 48 cycles of bending testing. In addition, the composite membrane has acceptable in vitro biocompatibility. The present work provides a novel alternative for fabrication of flexible and conductive SF biomaterials, which would expand the applications of fibroin materials in wearable electronics. [ABSTRACT FROM AUTHOR]

Spherical Ni2SnO4 nanoparticles were uniformly loaded on reduced graphene oxide (RGO) sheets via a hydrothermal process. The obtained nickel stannate–reduced graphene oxide (Ni2SnO4–RGO) composite was used as a catalyst for activating persulfate (PS). The heterostructure composed of Ni2SnO4 and RGO prevents both the agglomeration of Ni2SnO4 nanoparticles and the restacking of RGO sheets. The synergy between the two components affords enhanced Ni2SnO4–RGO catalytic activity. Using Ni2SnO4–RGO to activate PS can degrade bisphenol A (BPA) at a faster rate with less PS, in comparison with the most recently reported catalysts. BPA solution (50 mL, 0.10 mM) can be 100% degraded by PS (0.02 g) within 30 min at pH 8 using Ni2SnO4–RGO (0.02 g) as the catalyst. Moreover, the preparation of Ni2SnO4–RGO is simple, inexpensive and environment-friendly. The radical scavenging study indicates that sulfate radicals () and hydroxyl radicals (˙OH) are involved in the oxidation, in which plays a leading role. In addition, Ni2SnO4–RGO retains high catalytic activity after four consecutive cycles, exhibiting greatly enhanced stability in comparison with Ni2SnO4. Besides, the effect of different inorganic anions on the degradation was also explored. [ABSTRACT FROM AUTHOR]

Constructing a 3D hierarchical structure of electrode materials is a fast-developing technology to meet the increasing demand of high-rate electrochemical capacitors. Here, hierarchical CoNi2S4 nanofibers with pompom-like morphology are successfully synthesized via a two-step anion exchange reaction. The obtained CoNi2S4 nanofibers interweave densely with each other from inner core to external surface, constructing a stable 3D nanostructure. The pompom-like CoNi2S4 nanofibers have a high specific surface area of 169.7 m2 g−1 and a uniform nanopore size distribution in the range of 1–10 nm. Benefiting from these structural features, the pompom-like CoNi2S4 nanofibers provide more effective charge transport during electrochemical reactions compared with other 3D hierarchical structured CoNi2S4, such as flower-like nanosheets and urchin-like nanoneedles prepared by conventional methods. When evaluated as electrode materials in electrochemical tests, CoNi2S4 nanofibers with pompom-like hierarchical structure deliver a high specific capacitance of 2078.9 F g−1 at 0.5 A g−1 and an excellent rate capability of 844.4 F g−1 at 50 A g−1. The assembled CoNi2S4 nanofibers//activated carbon asymmetric electrochemical capacitor exhibits a good energy density of 48.2 W h kg−1 at a power density of 850 W kg−1, and a good cycling stability with 92.6% of its capacitance retained after 1000 cycles, suggesting that the pompom-like CoNi2S4 nanofibers can be applied as promising electrode materials for high-rate electrochemical capacitors. [ABSTRACT FROM AUTHOR]

Nickel phosphate (Ni3(PO4)2) is a promising electrode material for electrochemical capacitors, but the low intrinsic electrical conductivity and poor rate capability of Ni3(PO4)2 are the main challenges. To tackle these problems, amorphous mesoporous Ni3(PO4)2 with a pore diameter of 2–10 nm is grown on reduced graphene oxide (rGO), and a Ni3(PO4)2/rGO composite is obtained via a facile hydrothermal-calcination method in this work. The Ni3(PO4)2/rGO composite calcined at 300 °C (Ni3(PO4)2/rGO-300) possesses a uniform particle size and a high specific surface area of 198.72 m2 g−1. Benefiting from the structural characteristics, the synergistic effect of components and the high specific surface area, the Ni3(PO4)2/rGO-300 composite exhibits an extremely high specific capacitance of 1726 F g−1 at 0.5 A g−1 and an excellent rate capability of 850 F g−1 at 25 A g−1. In addition, the assembled Ni3(PO4)2/rGO-300//activated carbon asymmetric electrochemical capacitor delivers a good energy density of 57.42 W h kg−1 at a power density of 160 W kg−1. Compared with Ni3(PO4)2/rGO composites calcined at other temperatures and other nickel–phosphorus compounds reported in the literature, the Ni3(PO4)2/rGO-300 composite containing amorphous mesoporous Ni3(PO4)2 exhibits superior electrochemical performance, representing a new kind of electrode material for electrochemical capacitors. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) graphene-based composite materials have attracted increasing attention, owing to their specific surface area, high conductivity and electronic interactions. Here, we report a convenient route to fabricate a 3D Co3O4/Graphene Hydrogel (CGH) composite as an electrode material for supercapacitors. Utilizing the gelation of a graphene oxide dispersion enables the anchoring of Co3O4 nanoparticles on the graphene sheet surfaces and formation of the hydrogel simultaneously. Remarkably, the spherical Co3O4 particles can serve as spacers to keep the neighboring graphene sheets separated. The CGH exhibits a high specific capacitance (Cs) of 757.5 F g−1 at a current density of 0.5 A g−1, indicating its potential application as an electrode material for supercapacitors. [ABSTRACT FROM AUTHOR]

The electrochemical performance of hybrid capacitors is seriously affected by the slow charging and discharging of the bulk phase. Here, Co-doped amorphous NiMoS 4 modified with reduced graphene oxide (rGO) was prepared by a simple one-step hydrothermal method, and the obtained Co-doped NiMoS 4 /rGO nanocomposite (Ni 1- x Co x MoS 4 /rGO) exhibits a high specific surface area, realizing the redox reaction from the bulk to the surface. Owing to the doping of Co with abundant redox active sites and the support of rGO sheets with high conductivity and a stable structure, the Ni 1- x Co x MoS 4 /rGO anode assembled with an oxidized needle coke (NCO) cathode shows an excellent energy density of 28.9 W h kg -1 at a power density of 968.3 W kg -1 . In addition, the hybrid supercapacitor displays a superior cycling performance with a capacity retention of 92.4% after 10 000 cycles. The construction of the Co-doped NiMoS 4 /rGO nanocomposite provides an effective strategy to boost the activity and stability of amorphous NiMoS 4 for high-performance hybrid supercapacitors.

Three-dimensional (3D) graphene-based composite materials have attracted increasing attention, owing to their specific surface area, high conductivity and electronic interactions. Here, we report a convenient route to fabricate a 3D Co3O4/Graphene Hydrogel (CGH) composite as an electrode material for supercapacitors. Utilizing the gelation of a graphene oxide dispersion enables the anchoring of Co3O4 nanoparticles on the graphene sheet surfaces and formation of the hydrogel simultaneously. Remarkably, the spherical Co3O4 particles can serve as spacers to keep the neighboring graphene sheets separated. The CGH exhibits a high specific capacitance (Cs) of 757.5 F g(-1) at a current density of 0.5 A g(-1), indicating its potential application as an electrode material for supercapacitors.