Flexible Carbon Film Research Articles

Non-preoxidation synthesis of MXene integrated flexible carbon film for supercapacitors

Although the flexible carbon film integrated with MXene has been proven to be a new generation of supercapacitor material with good energy storage prospects, the MXene oxidation and the lack of active sites during the preparation of the carbon film can lead to irreversible capacity loss. Herein, a flexible carbon film constructed by MXene-integrated N-doped cavity-interconnected porous carbon nanofibers was prepared by a non-pre-oxidation synthesis strategy combining electrospinning and metal–organic framework derivatization. This flexible carbon film overcomes the oxidation problem of MXene during the stabilization of polyacrylonitrile, and the derived porous structure of cavity interconnection exposes more active sites. Due to its unique structural characteristics and ideal chemical composition, this independent flexible carbon film exhibits significantly enhanced electrochemical performance as an electrode material for supercapacitors. It exhibits an energy density of 26.2 Wh kg−1 at a power density of 500 W kg−1, and a capacitance retention rate of 96.3 % after 10,000 charge–discharge cycles. This study provides a unique strategy for the preparation of high-performance flexible carbon films, and this technology can also be extended to other integrated CNF composites for the design of high-performance supercapacitor electrodes.

Flexible carbon film with local enlarged interlayer spacing for ultrafast and highly durable potassium storage

Carbon materials have drawn much attention as a rigid electrode for the reversible intercalation of K+ along with a high surface adsorption capacity for potassium-ion batteries (KIBs). However, it is a challenge to prepare flexible carbon film for freestanding KIBs anodes, which could promote the free transfer of electrolyte and allow sufficient interlayer spacing to relieve the tension generated by K+-intercalation. Herein, a flexible carbon film constructed by honeycomb-like porous nanofibers with local enlarged interlayer spacing is synthesized by an electrospinning method together with a metal-organic frameworks (MOFs)-derived strategy. The flexible carbon film improves the electrical conductivity of freestanding electrode, and the interconnected porous structure with local enlarged interlayer spacing facilitates the transfer of electrolyte to active sites fluently and relieves the K+-intercalation induced tension, which synergistically boosts the reaction kinetics and K+-storage capacity. The freestanding flexible carbon film delivers excellent potassium storage performance of 386.1 mAh g−1 at 0.1 A g−1 after 500 cycles and 190.1 mAh g−1 at 5 A g−1 after 2400 cycles. Moreover, density functional theory (DFT) calculation confirms the advantage of edge-N atoms at graphene defect in adsorbing the K+ with limited volume expansion, which could provide extra capacity beyond K+-intercalated contribution for KIBs.

Porous carbon nanofibres with humidity sensing potential

Based on polyacrylonitrile (PAN)/poly(vinylpyrrolidone) (PVP) electrospun precursor fibres, this work developed an efficient and cost-effective pore generation approach to produce porous carbon nanofibres (PCNFs) with humidity sensing potential. PAN/PVP fibres were treated by a blend of N,N-dimethylmethanamide (DMF) and water (H2O) to generate a highly porous structure. Through the collective effects of crystallisation of PAN and dissolution of PVP, the solid PAN/PVP fibres were transformed to be porous ones with higher surface areas. Carbon nanofibres (CNFs) and PCNFs were manufactured from untreated and treated PAN/PVP fibres following air stabilisation at 260 °C and argon carbonisation at 1000 °C. Surface area and pore volume are both increased on PCNFs. To obtain a flexible carbon film for humidity sensing, the cellulose fibres were then combined with PCNFs and CNFs. After characterising the sensing performance of composite films in dynamic and static situations, experimental results demonstrated the PCNFs film's promising future as a stable and reactive humidity sensor.

Highly Flexible Carbon Film Implanted with Single‐Atomic Zn−N2 Moiety for Long‐Life Sodium‐Sulfur Batteries

AbstractRoom‐temperature sodium‐sulfur (RT Na–S) batteries are regarded as one of promising next‐generation energy storage systems owing to the high theoretical energy density (1274 Wh kg−1) and rich abundance of the raw materials. However, the sluggish redox kinetics and low electrical conductivity of sulfur (S) cathode significantly imped their practical application. Herein, a flexible carbon film implanted with single‐atomic Zn−N2 moiety (Zn‐N2/CF) is constructed as the efficient S host material to effectively improve the redox kinetics and electrical conductivity. The theoretical and experimental results show that, compared to Zn−N4 center, unsaturated Zn−N2 center with asymmetric electron distribution has significant advantages in anchoring and activating sodium polysulfides to accelerate the conversion from S8 to Na2S and reducing the reaction energy barrier of Na2S decomposition. Consequently, Zn‐N2/CF/S can retain a reversible capacity of 838.5 mAh g−1 at 0.1 A g−1 after 100 cycles, which is higher than that of Zn‐N4/CF/S (688.0 mAh g−1). Moreover, Zn‐N2/CF/S also maintains a long‐term cycling performance with a negligible capacity decay rate of 0.006% per cycle over 4000 cycles at 10 A g−1. This work provides an effective strategy to obtain the flexible carbon film implanted with unsaturated single‐atomic structure, thereby ultimately resulting in high‐performance RT Na–S batteries.

Boosting the Heat Dissipation Performance of Graphene/Polyimide Flexible Carbon Film via Enhanced Through-Plane Conductivity of 3D Hybridized Structure.

The development of materials with efficient heat dissipation capability has become essential for next-generation integrated electronics and flexible smart devices. Here, a 3D hybridized carbon film with graphene nanowrinkles and microhinge structures by a simple solution dip-coating technique using graphene oxide (GO) on polyimide (PI) skeletons, followed by high-temperature annealing, is constructed. Such a design provides this graphitized GO/PI (g-GO/PI) film with superflexibility and ultrahigh thermal conductivity in the through-plane (150 ± 7 W m-1 K-1 ) and in-plane (1428 ± 64 W m-1 K-1 ) directions. Its superior thermal management capability compared with aluminum foil is also revealed by proving its benefit as a thermal interface material. More importantly, by coupling the hypermetallic thermal conductivity in two directions, a novel type of carbon film origami heat sink is proposed and demonstrated, outperforming copper foil in terms of heat extraction and heat transfer for high-power devices. The hypermetallic heat dissipation performance of g-GO/PI carbon film not only shows its promising application as an emerging thermal management material, but also provides a facile and feasible route for the design of next-generation heat dissipation components for high-power flexible smart devices.

Graphene induced carbonization of polyimide films to prepared flexible carbon films with improving-thermal conductivity

Carbon films prepared by polyimide (PI) films treated under 1500°C exhibit favorable thermal conductivity. However, the bonds of carbon films will fracture and recombine which will cause shrinking and forming defects. The flexibility of the carbon films will be greatly reduced, and then affect the application of the carbon films in the field of thermal conduction. When the films prepared by the graphene oxide/polyimide (GO/PI) composite films and the reduced graphene oxide/polyimide (rGO/PI) composite films, respectively, rGO and GO can fill the defects, then increasing the flexibility of the carbon films and inducing the carbonation process. Because of the high thermal conductivity and the six-membered ring structure of rGO and GO, the carbonization temperature will decrease and save costs. When the composite films treated under 1500°C, the thermal conductivity increases with the content of rGO and GO. There are connections between PI and graphene. As the amount of rGO and GO increases, the strong interactions between the rGO or GO and PI lead to contact that enhances its thermal conductivity. However, the rGO and GO have different effects on the films flexibility and thermal conductivity and the differences will be described in the article.

Polyhedron carbon-scale stacking foldable fibrous film electrode with high capacitance performance from chitin fiber cloth for super flexible supercapacitors

This work is concerned with exploring high-performance flexible carbon electrode materials for supercapacitors derived from low-cost commercially-available fabrics. Herein, through direct carbonization without any additional pre-treated process and without any activators as well as any templates, we explored different carbonization temperatures to develop a super flexible carbon film derived from chitin fiber textile. The as-obtained carbon fibrous films are found to possess a novel unique microstructure and ultra-high specific surface areas (up to 382.2 m2 g−1), formed via irregular stacking and inter-connection of numerous polyhedron carbon-scales with much crevices and grooves. They present super high mechanical flexibility capable of being repeatedly folded and exhibited a very high capacitance performance with a maximum specific capacitance of up to 114.9 F g−1 at 1 A g−1 and an excellent cycling performance with about 94.0% of capacitance retention after 5000 charge-discharge cycles at 1 A g−1. The carbon fibrous film from biomass textiles shows great promise for applications as flexible electrode in energy storage.

Hydroxylated graphene-based flexible carbon film with ultrahigh electrical and thermal conductivity

Graphene-based films are widely used in the electronics industry. Here, surface hydroxylated graphene sheets (HGS) have been synthesized from natural graphite (NG) by a rapid and efficient molten hydroxide-assisted exfoliation technique. This method enables preparation of aqueous dispersible graphene sheets with a high dispersed concentration (∼10.0 mg ml−1) and an extraordinary production yield (∼100%). The HGS dispersion was processed into graphene flexible film (HGCF) through fast filtration, annealing treatment and mechanical compression. The HGS endows graphene flexible film with a high electrical conductivity of 11.5 × 104 S m−1 and a superior thermal conductivity of 1842 W m−1 K−1. Simultaneously, the superflexible HGCF could endure 3000 repeated cycles of bending or folding. As a result, this graphene flexible film is expected to be integrated into electronic packaging and high-power electronics applications.

Preparation of Graphene-Containing Composite Film and the Research on its Thermal Conductivity

A smooth and flexible carbon film was prepared via liquid exfoliation method followed by liquid evaporation using the natural flake graphite as the starting material. The XRD and Raman results demonstrated that the obtained film is composed of chemically reduced graphene, graphene oxide and graphite. The thermal transport property of the as-obtained film was investigated by light flash measurements. It is found that the as-obtained graphene-containing composite film has a high in-plane thermal diffusivity (2157 m2/s), and the corresponding thermal conductivity (754 W/m K) is higher than the other metal and normal graphite materials, which is very promising for applications requiring 2D heat conduction.