Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 13 de 13
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
ACS Appl Mater Interfaces ; 14(1): 1478-1488, 2022 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-34928125

RESUMO

Transparent flexible supercapacitors (TFSCs) are a tantalizing power supplier for future transparent flexible electronics. However, their energy density is far behind a practical level while maintaining high transparency. We report here a transparent flexible potassium-ion microcapacitor, and its high energy density (15.5 µWh cm-2) roots in the battery-supercapacitor hybrid storage mechanism and much enlarged working voltage (3 V), outperforming the state-of-the-art TFSC, which is generally based on an aqueous electrolyte and an asymmetric pseudocapacitive mechanism. From an electrode material perspective, a multidimensional topotactic host composite anode is designed in which the component not only performs energy storage by synchronous and reversible uptake of potassium ions and electrons into its host structure, but also mutually compensates individual weakness in functional and structural aspects, efficiently constructing a three-dimensional potassium-ion diffusion and electron transport system. This conceptual exhibition provides design principles at material and device levels for high-performance TFSCs.

2.
ACS Appl Mater Interfaces ; 13(45): 54096-54105, 2021 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-34749501

RESUMO

Aqueous zinc-ion batteries (ZIBs) are regarded as a promising candidate for ultrafast charge storage owing to the high ionic conductivity of aqueous electrolytes and high theoretical capacity of zinc metal anodes. However, the strong electrostatic interaction between high-charge-density zinc ions and host materials generally leads to sluggish ion-transport kinetics and structural collapse of rigid cathode materials during the charge/discharge process, so searching for suitable cathode materials for ultrafast and long-term stable ZIBs remains a great challenge. Herein, flexible electron-rich ion channels enabling fast-charging and stable aqueous ZIBs have been demonstrated. Because of the nitrogen-rich conjugated structure of organic phenazine (PNZ) molecules, electron-rich ion channels are formed with the C═N redox centers situated on the channel surface, where zinc ions can transport rapidly and react with active moieties directly. Meanwhile, the π-conjugated systems and inherent flexibility of PNZ molecules can accommodate rapid strain changes and maintain their structural stability during zinc-ion intercalation/deintercalation. Consequently, they exhibit a high capacity of 94.2 mAh g-1 at an ultrahigh rate of 700C (208.6 A g-1) and an ultralong life over 100,000 cycles at 100C, which are superior to those of previously reported aqueous ZIBs. Our work presents a new way for developing ultrafast and ultrastable aqueous ZIBs.

3.
J Colloid Interface Sci ; 596: 130-138, 2021 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-33839347

RESUMO

Lithium-ion hybrid capacitors (LICs) have gained increasing focus owing to their high energy/power densities. The development of anodes with superior rate capability is an effective way to surmount the kinetic mismatch between anodes and cathodes, and thus, enhancing the energy/power densities. Herein, Co3O4 nanoparticles embedded in three-dimensionally (3D) ordered macro-/mesoporous TiO2 (Co3O4@TiO2) are synthesized through an in situ method from dual templates. Differing from the composite prepared by loading active nanoparticles on support, Co3O4 nanoparticles are embedded in TiO2 framework, which can improve the stability of the electrode. Furthermore, the hierarchically porous structure of TiO2 is in favor of the rapid diffusion of ions and electrolyte. As a result, The Co3O4@TiO2-2 composite with an optimized Co3O4 content (~25 wt%) delivers a high capacity of 944.1 mAh g-1 after 100 cycles at 0.1 A g-1 and high-rate capability (405.7 mAh g-1 after 1000 cycles at 5 A g-1). The LIC assembled with Co3O4@TiO2-2 anode and activated carbon (AC) cathode delivers high energy/power densities (maximum, 87.9 Wh kg-1/10208.9 W kg-1) and great cycle stability (88.1%, 6000 cycles, 0.5 A g-1).

4.
Small ; 16(48): e2004457, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33155379

RESUMO

Nano heterostructures relying on their versatile construction and the breadth of combined functionality have shown great potential in energy storage fields. Herein, 2D sandwiched MoSe2 /TiO2- x /graphene nano heterostructures are designed by integrating structural and functional effects of each component, aiming to address the rate capability and cyclic stability of MoSe2 for sodium ion capacitors (SICs). These 2D nano heterostructures based on graphene platform can facilitate the interfacial electron transport, giving rise to fast reaction kinetics. Meanwhile, the 2D open structure induces a large extent of surface capacitive contribution, eventually leading to a high rate capability (415.2 mAh g-1 @ 5 A g-1 ). An ultrathin oxygen deficient TiO2- x layer sandwiched in these nano heterostructures provides a strong chemical-anchoring regarding the products generated during the sodiation/desodiation process, securing the entire cyclic stability. The associated sodiation/desodiation mechanism is revealed by operando and ex situ characterizations, which exhibits a strong solid electrolyte interphase (SEI) dependence. The simulations verify the dependent sodiation products and enhanced heterostructural chemical-anchoring. Assembled SICs based on these nano heterostructures anode exhibit high initial Coulombic efficiency, energy/power densities, and long cycle life, shedding new light on the design of nano heterostructure electrodes for high performance energy storage application.

5.
ACS Appl Mater Interfaces ; 12(26): 29218-29227, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32490658

RESUMO

Performance degradation of lithium/sodium-ion capacitors (LICs/SICs) mainly originates from anode pulverization, particularly the alloying and conversion types, and has spurred research for alternatives with an insertion mechanism. Three-dimensional (3D) topotactic host materials remain much unexplored compared to two-dimensional (2D) ones (graphite, etc.). Herein, vanadium monophosphide (VP) is designed as a 3D topotactic host anode. Ex situ electrochemical characterizations reveal that there are no phase changes during (de)intercalation, which follows the topotactic intercalation mechanism. Computational simulations also confirm the metallic feature and topotactic structure of VP with a spacious interstitial position for the accommodation of guest species. To boost the electrochemical performance, carbon nano-onions (CNOs) are coupled with 3D VP. Superior specific capacity and rate capability of VP-CNOs vs lithium/sodium can be delivered due to the fast ion diffusion nature. An exceptional capacity retention of above 86% is maintained after 20 000 cycles, benefitting from the topotactic intercalation process. The optimized LICs/SICs exhibit high energy/power densities and an ultrastable lifespan of 20 000 cycles, which outperform most of the state-of-the-art LICs and SICs, demonstrating the potential of VP-CNOs as insertion anodes. This exploration would draw attention with regard to insertion anodes with 3D topotactic host topology and provide new insights into anode selection for LICs/SICs.

6.
J Colloid Interface Sci ; 554: 650-657, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31351335

RESUMO

Transparent and flexible supercapacitors (TFSCs) could diversify the future wearable electronics owing to the fascinating optoelectronic and electrochemical performances. Herein, we report symmetric TFSCs assembled by reduced graphene oxide (rGO)@Ag nanowire/poly (ethylene terephthalate) (PET) transparent electrodes for capacitive storage, in which the interfacial structure of rGO film can be tuned by a facile freeze drying technique. The enlarged interlayer spacing of rGO film deteriorated the electronic migration derived from the loose layer structure, whereas about 33-52% of the areal capacitance of TFSCs was boosted as compared with the ones without freeze drying at the same transmittance. It is concluded that the enlarged inter-distance of rGO film could facilitate diffusion and transport of ions in the electrolyte, furthermore, the expanded rGO film could provide more interface to accommodate more ions for storage. The simulation results also confirmed the lower diffusion barrier and larger band gap of rGO with larger interlayer distance. The mechanically robust TFSCs exhibit the maximum energy density of 89.2 nWh cm-2, and the maximum power density of 4.63 µW cm-2 with remaining energy density of 41.1 nWh cm-2, as well as 3000 cyclic stability, demonstrating an efficient strategy toward high performance TFSCs.

7.
Langmuir ; 34(50): 15245-15252, 2018 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-30428676

RESUMO

Transparent and flexible supercapacitors (TFSCs) are viable power sources for next-generation wearable electronics. The ingenious design of the transparent electrode determines the performance of TFSCs. A percolating film of a pillared graphene layer integrated with a silver nanowire network as the transparent electrode was prepared, by which TFSC devices exhibit a significantly improved performance contrastively. Under the condition of the same transmittance, about 27-72% improvement in the areal capacitance can be achieved. On the one hand, the pillars of carbon nanotube (CNT) were distributed in the graphene layer uniformly, enlarging the inner distance of adjacent graphene layers and providing an open structure for extra ion transport and storage of TFSCs. On the other hand, the introduced CNT could facilitate the electron transport at the direction perpendicular to the graphene basal plane, enhancing the electronic conductivity of the graphene layer. More importantly, the formed percolating film ensures an efficient transport of electron along with the silver nanowire when it encounters the obstacle within the graphene layer, resulting in a highly conductive electrode. The TFSC device with a good compatibility indicates a reliable practicability, which provides a facile route toward the design of high-performance TFSCs.

8.
Nanomaterials (Basel) ; 8(2)2018 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-29373525

RESUMO

A simple and effective method was developed to obtain the electrode for lithium/sulfur (Li/S) batteries with high specific capacity and cycling durability via adopting an interconnected sulfur/activated carbon/graphene (reduced graphene oxide) aerogel (S/AC/GA) cathode architecture. The AC/GA composite with a well-defined interconnected conductive network was prepared by a reduction-induced self-assembly process, which allows for obtaining compact and porous structures. During this process, reduced graphene oxide (RGO) was formed, and due to the presence of oxygen-containing functional groups on its surface, it not only improves the electronic conductivity of the cathode but also effectively inhibits the polysulfides dissolution and shuttle. The introduced activated carbon allowed for lateral and vertical connection between individual graphene sheets, completing the formation of a stable three-dimensionally (3D) interconnected graphene framework. Moreover, a high specific surface area and 3D interconnected porous structure efficiently hosts a higher amount of active sulfur material, about 65 wt %. The designed S/AC/GA composite electrodes deliver an initial capacity of 1159 mAh g-1 at 0.1 C and can retain a capacity of 765 mAh g-1 after 100 cycles in potential range from 1 V to 3 V.

9.
Science ; 349(6252): 1083-7, 2015 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-26339027

RESUMO

Graphene, a single layer of carbon atoms bonded in a hexagonal lattice, is the thinnest, strongest, and stiffest known material and an excellent conductor of heat and electricity. However, these superior properties have yet to be realized for graphene-derived macroscopic structures such as graphene fibers. We report the fabrication of graphene fibers with high thermal and electrical conductivity and enhanced mechanical strength. The inner fiber structure consists of large-sized graphene sheets forming a highly ordered arrangement intercalated with small-sized graphene sheets filling the space and microvoids. The graphene fibers exhibit a submicrometer crystallite domain size through high-temperature treatment, achieving an enhanced thermal conductivity up to 1290 watts per meter per kelvin. The tensile strength of the graphene fiber reaches 1080 megapascals.

10.
Chem Commun (Camb) ; 50(73): 10703-6, 2014 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-25079002

RESUMO

Uniform amorphous vanadium oxide films were coated on graphene via atomic layer deposition and the nano-composite displays an exceptional capacity of ~900 mA h g(-1) at 200 mAg(-1) with an excellent capacity retention at 1 A g(-1) after 200 cycles. The capacity contribution (1161 mA h g(-1)) from vanadium oxide only almost reaches its theoretical value.

11.
ACS Appl Mater Interfaces ; 6(17): 15262-71, 2014 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-25111062

RESUMO

Organic phase change materials (PCMs) have been utilized as latent heat energy storage and release media for effective thermal management. A major challenge exists for organic PCMs in which their low thermal conductivity leads to a slow transient temperature response and reduced heat transfer efficiency. In this work, 2D thermally annealed defect-free graphene sheets (GSs) can be obtained upon high temperature annealing in removing defects and oxygen functional groups. As a result of greatly reduced phonon scattering centers for thermal transport, the incorporation of ultralight weight and defect free graphene applied as nanoscale additives into a phase change composite (PCC) drastically improve thermal conductivity and meanwhile minimize the reduction of heat of fusion. A high thermal conductivity of the defect-free graphene-PCC can be achieved up to 3.55 W/(m K) at a 10 wt % graphene loading. This represents an enhancement of over 600% as compared to pristine graphene-PCC without annealing at a comparable loading, and a 16-fold enhancement than the pure PCM (1-octadecanol). The defect-free graphene-PCC displays rapid temperature response and superior heat transfer capability as compared to the pristine graphene-PCC or pure PCM, enabling transformational thermal energy storage and management.

12.
Nanotechnology ; 24(42): 424002, 2013 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-24067324

RESUMO

Atomic layer deposition (ALD) was used to deposit TiO2 anode material on high surface area graphene (reduced graphene oxide) sheets for Li-ion batteries. An Al2O3 ALD ultrathin layer was used as an adhesion layer for conformal deposition of the TiO2 ALD films at 120 ° C onto the conducting graphene sheets. The TiO2 ALD films on the Al2O3 ALD adhesion layer were nearly amorphous and conformal to the graphene sheets. These nanoscale TiO2 coatings minimized the effect of the low diffusion coefficient of lithium ions in bulk TiO2. The TiO2 ALD films exhibited stable capacities of ~120 mAh g(-1) and ~100 mAh g(-1) at high cycling rates of 1 A g(-1) and 2 A g(-1), respectively. The TiO2 ALD films also displayed excellent cycling stability with ~95% of the initial capacity remaining after 500 cycles. These results illustrate that ALD can provide a useful method to deposit electrode materials on high surface area substrates for Li-ion batteries.

13.
Small ; 8(3): 452-9, 2012 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-22162371

RESUMO

Flexible graphene paper (GP) pillared by carbon black (CB) nanoparticles using a simple vacuum filtration method is developed as a high-performance electrode material for supercapacitors. Through the introduction of CB nanoparticles as spacers, the self-restacking of graphene sheets during the filtration process is mitigated to a great extent. The pillared GP-based supercapacitors exhibit excellent electrochemical performances and cyclic stabilities compared with GP without the addition of CB nanoparticles. At a scan rate of 10 mV s(-1) , the specific capacitance of the pillared GP is 138 F g(-1) and 83.2 F g(-1) with negligible 3.85% and 4.35% capacitance degradation after 2000 cycles in aqueous and organic electrolytes, respectively. At an extremely fast scan rate of 500 mV s (-1) , the specific capacitance can reach 80 F g(-1) in aqueous electrolyte. No binder is needed for assembling the supercapacitor cells and the pillared GP itself may serve as a current collector due to its intrinsic high electrical conductivity. The pillared GP has great potential in the development of promising flexible and ultralight-weight supercapacitors for electrochemical energy storage.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...