Flexible solid-state supercapacitors (FSSCs) are frontrunners in energy storage device technology and have attracted extensive attention owing to recent significant breakthroughs in modern wearable electronics In this study, we review the state-of-the-art advancements in FSSCs to provide new insights on mechanisms, emerging electrode materials, flexible gel electrolytes and novel cell designs The review begins with a brief introduction on the fundamental understanding of charge storage mechanisms based on the structural properties of electrode materials The next sections briefly summarise the latest progress in flexible electrodes (ie, freestanding and substrate-supported, including textile, paper, metal foil/wire and polymer-based substrates) and flexible gel electrolytes (ie, aqueous, organic, ionic liquids and redox-active gels) Subsequently, a comprehensive summary of FSSC cell designs introduces some emerging electrode materials, including MXenes, metal nitrides, metal–organic frameworks (MOFs), polyoxometalates (POMs) and black phosphorus Some potential practical applications, such as the development of piezoelectric, photo-, shape-memory, self-healing, electrochromic and integrated sensor-supercapacitors are also discussed The final section highlights current challenges and future perspectives on research in this thriving field

Towards flexible solid-state supercapacitors for smart and wearable electronics

Inorganic semiconductor nanostructures are ideal systems for exploring a large number of novel phenomena at the nanoscale and investigating the size and dimensionality dependence of their properties for potential applications. The use of such nanostructures with tailored geometries as building blocks is also expected to play crucial roles in future nanodevices. Since the discovery of carbon nanotubes much attention has been paid to exploring the usage of inorganic semiconductor nanostructures as field-emitters due to their low work functions, high aspect ratios and mechanical stabilities, and high electrical and thermal conductivities. This article provides a comprehensive review of the state-of-the-art research activities in the field. It mainly focuses on the most widely studied inorganic nanostructures, such as ZnO, ZnS, Si, WO3, AlN, SiC, and their field-emission properties. We begin with a survey of inorganic semiconductor nanostructures and the field-emission principle, and then discuss the recent progresses on several kinds of important nanostructures and their field-emission characteristics in detail and overview some additional inorganic semiconducting nanomaterials in short. Finally, we conclude this review with some perspectives and outlook on the future developments in this area.

Inorganic semiconductor nanostructures and their field-emission applications

Recent progress in synthesis, properties and potential applications of SiC nanomaterials

A High-Energy Density Asymmetric Supercapacitor Based on Fe2O3 Nanoneedle Arrays and NiCo2O4/Ni(OH)2 Hybrid Nanosheet Arrays Grown on SiC Nanowire Networks as Free-Standing Advanced Electrodes

Aqueous Ni/Fe batteries have great potential as flexible energy storage devices, owing to their low cost, low toxicity, high safety, and high energy density. However, the poor cycling stability has limited the widely expected application of Ni/Fe batteries, while the use of heavy metal substrates cannot meet the basic requirement for flexible devices. In this work, a flexible type of solid-state Ni/Fe batteries with high energy and power densities is rationally developed using needle-like Fe3O4 and flake-like NiO directly grown on carbon cloth/carbon nanofiber (CC–CF) matrix as the anode and cathode, respectively. The hierarchical CC–CF substrate with high electric conductivity and good flexibility serves as an ideal support for guest active materials of nanocrystalline Fe3O4 and NiO, which can effectively buffer the volume change giving rise to good cycling ability. By utilizing a gel electrolyte, a robust and mechanically flexible quasi-solid-state Ni/Fe full cell can be assembled. It demonstrates optimal electrochemical performance, such as high energy density (5.2 mWh cm−3 and 94.5 Wh Kg−1), high power density (0.64 W cm−3 and 11.8 KW Kg−1), together with excellent cycling ability. This work provides an example of solid-state alkaline battery with high electrochemical performance and mechanical flexibility, holding great potential for future flexible electronic devices.

High‐Performance Flexible Solid‐State Ni/Fe Battery Consisting of Metal Oxides Coated Carbon Cloth/Carbon Nanofiber Electrodes

The current trend with integrated energy-storage units in portable electronics lies in continuous advancements in nanostructured materials, thin-film manufacture technologies, and device architectures with enhanced functionality and reliability of existing components. Despite this, it is still challenging to provide cost-efficient solution to further improve the energy and power densities and cyclability of supercapacitors (SCs), especially at ultrafast rates while maintaining their environmentally friendly and even well-run at arbitrary harsh environments character. In this contribution, we report the fabrication of quasi-aligned single crystalline 3C-SiC nanowire (3C-SiCNW) array with tailored shapes and nitrogen-doping (N-doping). The resultant large-scale SiCNWs were directly grown on the surface of a flexible carbon fabric via a simple chemical vapor deposition method. We found that the SC performance of SiCNW arrays can be substantially enhanced by nitrogen doping, which could favor a more localized...

Flexible Nitrogen Doped SiC Nanoarray for Ultrafast Capacitive Energy Storage.

P-type 3C-SiC nanowires and their optical and electrical transport properties

Flexible field emission (FE) arrays have a wide range of applications in next generation low-cost, lightweight and wearable electronics, roll-up displays, and large-area circuits on curved objects, yet the growth of tapered, high-quality single-crystalline nanostructure-based emitters on flexible substrates with superior FE properties remains challenging and related work is limited. On the other hand, our recent studies have shown that silicon carbide (SiC) 1D nanostructures could meet nearly any stringent requirement for an ideal FE emitter. In this contribution, we report the growth of quasi-aligned, single-crystalline n-type doped (N-doped) 3C-SiC nanoneedles (3C-SiCNNs) on highly flexible carbon fabric via the catalyst assisted pyrolysis of polysilazane. The as-synthesized SiCNNs possess a tapered structure with tiny clear tips with sizes of several to tens of nanometers. The fabricated 3C-SiCNNs have extremely low emission turn-on fields (Eon) in the range of 0.5–1.6 V μm−1 with an average of 1.1 V μm−1, which is comparable to the lowest value ever reported for 1D nanostructure emitters that, however, are grown on rigid substrates. Specifically, our SiCNN arrays on carbon fabric are mechanically and electrically robust, and can withstand mechanical bending up to 500 times and still retain excellent FE performance with Eon of ∼1.1 V μm−1. The field-enhancement factor has been calculated to be 6.5 × 103. The superior FE properties can be attributed to the significant enhancements of the tapered unique morphology and N-doping of the SiCNNs. Calculations based on local density functional theory suggest that nitrogen dopants in the 3C-SiC nanostructure could favor a more localized impurity state near the conduction band edge, which improves the electron field emission. We strongly believe that the present work will provide a new insight into the fabrication of flexible field emission arrays with ultralow turn-on fields enhanced by both shape and doping.

Growth of n-type 3C-SiC nanoneedles on carbon fabric: toward extremely flexible field emission devices

Multi-component self-assembled anti-tumor nano-vaccines based on MUC1 glycopeptides

https://www.rsc.org/suppdata/cc/c2/c2cc30583f/c2cc30583f.pdf

Youqiang Chen

Papers

Flexible Nitrogen Doped SiC Nanoarray for Ultrafast Capacitive Energy Storage.

P-type 3C-SiC nanowires and their optical and electrical transport properties

Growth of n-type 3C-SiC nanoneedles on carbon fabric: toward extremely flexible field emission devices

Multi-component self-assembled anti-tumor nano-vaccines based on MUC1 glycopeptides

High on/off ratio p-type field-effect transistor enabled by a single heavily Al-doped α-Si3N4 nanowire