Search

Ce-UiO-66 was firstly used as a supercapacitor electrode material and exhibited a high capacitance of 6.9 Fcm−2 in a redox electrolyte. A novel self-supported structure of Ce-UiO-66/TNF was firstly synthesized by growing Ce-UiO-66 on a TNF substrate. This novel Ce-UiO-66/TNF material was proved to possess a high supercapacitive performance in the redox electrolyte of Fe(CN) 6 3−/4−, and it was also the first study for Ce-UiO-66 material on the supercapacitor application. High specific capacitances of 6.9 and 2.5 Fcm−2 can be achieved at large current densities of 20 and 80 mAcm−2, respectively. After 10,000 charge-discharge cycles, the capacitance retention can be kept at 95% and the coulomb efficiency can be maintained over 98%. Such outstanding electrochemical performance may be related to the redox property of the electrolyte, high specific surface area of the Ce-UiO-66 material, porous characteristic of the TNF substrate and self-supported structure of the whole electrode. [ABSTRACT FROM AUTHOR]

Abstract Graphene paper is a promising electrode material for use in flexible supercapacitors due to its good electronic conductivity and excellent mechanical characteristics. However, layers of graphene paper have a strong tendency to restack, resulting in a seriously reduced specific surface area and limited electrochemical performance. In this paper, restacked layers of graphene paper are reopened by a vacuum-assisted method, and carbon nanotubes (CNTs) are directly deposited on the enlarged space between the opened graphene layers. Consequently, an ordered carbon composite structure with alternately arranged graphene sheets and CNTs is constructed and exhibits increased specific surface area and a 3D conductive network. The structure and morphology of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and N 2 adsorption/desorption measurements. The electrochemical performance was tested by galvanostatic charge-discharge test (GDC), electrochemical impedance spectroscopy (EIS) and cyclic voltammograms (CV). The obtained graphene/CNT paper exhibits a remarkably improved capacity of 170.8 F g−1, which is nearly two times higher than that obtained for a regular graphene paper. Highlights • A unique carbonaceous structure with CNTs depositing between the opened layers of graphene is established. • The reopening of the graphene layers can enlarge the layer distance and increase the SSA. • The deposited CNTs can further inhibit the restacking of graphene layers and form a 3D conductive framework. • The prepared MGCP exhibits significantly enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

Graphene aerogel is one of the most promising candidates for supercapacitors electrode material because of its high specific surface area and good electronic conductivity. However, the extremely low gravimetric density seriously limits its further practical applications. In this paper, a compression strategy was utilized to increase the gravimetric density by forming a unique highly-curved carbon nanotubes supported graphene porous 3D layer structure. The structure and morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectrum and N 2 adsorption/desorption measurement. Results demonstrate that the highly-curved carbon nanotubes between the graphene layers can prevent the restacking of the graphene layers. The newly formed structure retains the merits of graphene aerogel such as high specific surface area, good electronic conductivity, and porous structure. The electrochemical performance was investigated by a galvanostatic charge-discharge test (GDC) and a specific capacitance of 246.3 F g −1 was achieved, endowing it with great application potential as an supercapacitors electrode material. [ABSTRACT FROM AUTHOR]

• Compact porous Si@graphene layered structure with improved contact interface and adequate interconnected pores were prepared by a facile hydrothermal method. • The improved Si/graphene contact interface can promote the positive effect of graphene on restraining the volume change and thus enhance the structural stability during repetitive cycling. • The closely wrapping graphene and interconnected pores simultaneously provide adequate paths for fast transfer of electrons and ions, resulting in greatly improved dynamic performance. Si/carbon composites are attractive anode materials for rechargeable Li-ion batteries (RLIBs), which combine the advantages of Si and graphene. Designing special Si/carbon structure with intimate contact interface and abundant void space for fast ion transmission is an effective strategy for enhancing cyclability and rate performance of the electrode materials. Inspired by the structure of fishnet, here we fabricate a binder-free and self-standing Si@porous-graphene (Si@PGN 60) composite with nano silicon particles encapsulated in porous graphene sheets. The obtained Si@PGN 60 sample exhibits many favourable features for high performance Si/carbon anodes, including improved Si/graphene contact interface, and abundant void space for fast ion transmission. Tanks to the unique structure, the resultant Si@PGN 60 anode presents remarkably improved capacity reaching 1839.9 mA h g−1 at 300 mA g−1, and excellent cycling performance (734 mA h g−1 at a high current density of 3000 mA g−1). Here we fabricate a binder-free and self-standing Si@graphene (Si@PGN 60) composite with silicon encapsulated in porous graphene sheets. The obtained Si@PGN exhibits many favourable features for high performance Si/carbon anodes, including improved contact interface between Si and graphene, and abundant void space for fast ion transmission. Tanks to the unique structure, the resultant Si@PGN presents not only remarkably improved capacity reaching 1839.9 mA h g−1 at 300 mA g−1, but also superior rate performance of 734 mA h g−1 at a relatively high current density of 3000 mA g−1. [Display omitted] [ABSTRACT FROM AUTHOR]

Closely wrapped Si@graphene structure with improved contacting interface were synthesized by a facile compression method. The improved contacting interface have greatly enhanced the positive effect of graphene sheets on restraining the volume change of Si nanoparticles and improving the electronic conductivity. The obtained composite sample shows significantly improved electrochemical performance as anode material for Li-ion batteries. [Display omitted] • Closely wrapped Si@graphene structure with improved contact interface was synthesized by a facile compression method. • The improved contact interface has enhanced the effect of graphene on restraining the volume change of Si nanoparticles. • The composite sample shows significantly improved cycling stability and rate performance. Despite their extremely high capacity (4200 mA h g−1), the practical application of silicon anodes is still frustrated by their poor cycling performance, resulting from severe volume changes and pulverization of the electrode material. Introducing graphene in silicon is an ideal approach for addressing these issues. Nevertheless, the large size difference between Si and graphene makes high-quality contact difficult to realize, which severely harms the electrochemical performance of Si/graphene composites. Herein, a unique Si@graphene layer structure (p-Si@GN) with an improved contact interface is fabricated by a facile high-pressure method, in which the surfaces of silicon particles are closely covered by graphene layers, restraining the volume changes from multiple angles. The superior structure of the layered p-Si@GN composite exhibits multiple desired features for high-performance Si-based anodes, such as high Li+ storage capacity resulting from high-capacity Si nanoparticles, outstanding electron conductivity due to the formation of a continuous graphene conductive network, and excellent structural stability due to the enhanced protective function of graphene layers with an improved contact interface. Due to these advantages, the p-Si@GN 40 anode, prepared under 40 MPa pressure, exhibits a significantly improved capacity of 2096.9 mA h g−1 at a current density of 300 mA g−1, an enhanced rate capability of 706.4 mA h g−1 at 3000 mA g−1, and superior cycling performance with a high capacity retention of 82.6 % after 150 cycles. [ABSTRACT FROM AUTHOR]