Freestanding needle-like polyaniline–coal based carbon nanofibers composites for flexible supercapacitor

Material Nanoarchitectonics of Functional Polymers and Inorganic Nanomaterials for Smart Supercapacitors

Smart supercapacitors are a promising energy storage solution due to their high power density, long cycle life, and low-maintenance requirements. Functional polymers (FPs) and inorganic nanomaterials are used in smart supercapacitors because of the favorable mechanical properties (flexibility and stretchability) of FPs and the energy storage properties of inorganic materials. The complementary properties of these materials facilitate commercial applications of smart supercapacitors in flexible smart wearables, displays, and self-generation, as well as energy storage. Here, an overview of strategies for the development of suitable materials for smart supercapacitors is presented, based on recent literature reports. A range of synthetic techniques are discussed and it is concluded that a combination of organic and inorganic hybrid materials is the best option for realizing smart supercapacitors. This perspective facilitates new strategies for the synthesis of hybrid materials, and the development of material technologies for smart energy storage applications.

Nickel nanoparticles embedded in porous carbon nanofibers and its electrochemical properties

Flexible porous carbon nanofibers containing nickel nanoparticles were synthesized by direct carbonization of electrospun Ni-MOFs/polyacrylonitrile fibers. The as-synthesized composite nanofibers were employed as binder-free electrodes, and exhibit high specific capacitance (up 672 F g^-1 at current density of 2 A g^-1) and superior rate capability (57% capacitance retention from current density of 2-10 A g^-1), which may be attributed to their binder-free nature, unique one-dimensional (1D) structure and highly dispersed electrochemically active nickel nanoparticles. Furthermore, a symmetric supercapacitor was assembled using the fiber electrodes in 6 M KOH, and the energy density of 17.8 Wh kg^-1 was achieved in a potential window of 1.5 V. This self-standing fiber with abundant mesopores and macropores is expected to become a promising electrode material for high-performance supercapacitors.

Coal-based 3D hierarchical porous carbon aerogels for high performance and super-long life supercapacitors

Coal-based 3D hierarchical porous carbon aerogels (3D HPCAs) has been successfully fabricated from a freeze-drying method and with subsequent of calcination process, using coal oxide as carbon precursors, and PVA as both cross-linking agent and sacrifice template. The 3D HPCAs, using as electrode materials for supercapacitors, display outstanding electrochemical performance. The optimal sample (HPCAs-0.4-800) presents a high specific capacitance of 260 F g-1 at 1 A g-1, and exhibits considerable rate capability with the retention of 81% at 10 A g-1. Notably, HPCAs-0.4-800 shows an excellent cycling stability with 105% of the capacitance retention after 50000 cycles at 10 A g-1, attributing to its unique hierarchical porosity, high surface area up to 1303 m2 g-1, and improved conductivity. This work offers a promising route to synthesize coal-based porous carbon aerogels electrode materials for supercapacitors.

NiS nanosheets with novel structure anchored on coal-based carbon fibers prepared by electrospinning for flexible supercapacitors

Elm seed-like NiS/coal-based carbon fibers were rationally designed and synthesized via a multistep transformation approach for flexible supercapacitors.

A Review of Supercapacitors Based on Graphene and Redox-Active Organic Materials

Supercapacitors are a highly promising class of energy storage devices due to their high power density and long life cycle. Conducting polymers (CPs) and organic molecules are potential candidates for improving supercapacitor electrodes due to their low cost, large specific pseudocapacitance and facile synthesis methods. Graphene, with its unique two-dimensional structure, shows high electrical conductivity, large specific surface area and outstanding mechanical properties, which makes it an excellent material for lithium ion batteries, fuel cells and supercapacitors. The combination of CPs and graphene as electrode material is expected to boost the properties of supercapacitors. In this review, we summarize recent reports on three different CP/graphene composites as electrode materials for supercapacitors, discussing synthesis and electrochemical performance. Novel flexible and wearable devices based on CP/graphene composites are introduced and discussed, with an eye to recent developments and challenges for future research directions.

A green approach to prepare hierarchical porous carbon nanofibers from coal for high-performance supercapacitors

A green method is designed to obtain hierarchical porous carbon nanofibers from coal. In the work, deionized water, coal, polyvinyl alcohol and Pluronic F127 are used as the aqueous solution, carbon source, spinning assistant and soft template for spinning, respectively. As electrode materials for supercapacitors, the obtained hierarchical porous carbon nanofibers exhibit a high specific capacitance of 265.2 F g⁻¹ at 1.0 A g⁻¹ in 6 M KOH, a good rate performance with a capacitance of 220.3 F g⁻¹ at 20.0 A g⁻¹ with the retention of 83.1% and a superior cycle stability without capacitance loss after 20 000 charge/discharge cycles at 10.0 A g⁻¹. Compared with the carbon nanofibers constructed without Pluronic F127, the enhanced electrochemical performance of the sample benefits from a larger contact surface area and the mesoporous structure formed by decomposition of Pluronic F127 and good structural stability. This work not only provides a green route for high-value utilization of coal in energy storage, but also paves a new way to make hierarchical porous carbon nanofibers from coal for supercapacitor electrodes with high specific capacitance and long cycle life.

A green method is designed to obtain hierarchical porous carbon nanofibers from coal for supercapacitor electrodes with high specific capacitance and long cycle life.

The facile synthesis of layered Ti2C MXene/carbon nanotube composite paper with enhanced electrochemical properties

Ti₂AlC has been investigated for several decades, but much less attention has been paid to its delamination and potential energy storage applications, mainly due to the difficulty of delamination and its oxidation features. Herein, a new path to enhance exfoliation and delamination of two-dimensional (2D) Ti₂CT_x MXene is used. By using an etchant of HCl + LiF, multilayer Ti₂CT_x is easy to obtain. With only the assistance of mild sonication for 1.5 h without any additional intercalation, two-dimensional (2D) Ti₂CT_x flake suspensions are produced. Subsequently, the as-fabricated stable suspensions of delaminated Ti₂CT_x flakes are combined with carbon nanotubes. After filtration, a two-dimensional layered Ti₂CT_x/carbon nanotube (CNT) nanocomposite "paper" is prepared. Owing to the larger specific area of MXene flakes, which is caused by the complete exfoliation of MXene, with carbon nanotubes assisting with structural support between layers to prevent restacking, this structure provides a rapid charge transfer path during electrochemical reactions. When the nanocomposite paper is used as a lithium ion battery anode, it exhibits a higher capacitance and better cycling stability (a reversible capacity of 155.5 mA h g^-1 at 100 mA g^-1 after 200 cycles). Moreover, the "paper" can be directly used for electrodes in supercapacitors; the calculated capacitances are 515.3 F g^-1 and 694 F cm^-3 at a scanning rate of 2 mV s^-1. The facile synthesis of layered Ti₂C MXene/carbon nanotube nanocomposite paper provides a more secure and easy way to fabricate promising energy storage materials, and creates wider opportunities for exploiting the potential of other MXenes.

Cost effective synthesis of a copper-1H-imidazole@activated carbon metal organic framework as an electrode material for supercapacitor applications

A simple and sonochemically synthesized Cu-IC MOF exhibits good supercapacitive behaviour.

Hierarchical porous carbon spheres constructed from coal as electrode materials for high performance supercapacitors

Hierarchical porous carbon spheres (PCS) were prepared by a simple one-pot spray pyrolysis of coal oxide solution for use as supercapacitor electrode materials.

Synthesis and characterization of free-standing activated carbon/reduced graphene oxide film electrodes for flexible supercapacitors

Free-standing, binder-free and flexible activated carbon/reduced graphene oxide (AC/rGO) composite films with various ratios were fabricated via a facile vacuum-filtration process.