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1.
Nat Commun ; 10(1): 5810, 2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31862935

RESUMO

Inferior charge transport in insulating and bulk discharge products is one of the main factors resulting in poor cycling stability of lithium-oxygen batteries with high overpotential and large capacity decay. Here we report a two-step oxygen reduction approach by pre-depositing a potassium carbonate layer on the cathode surface in a potassium-oxygen battery to direct the growth of defective film-like discharge products in the successive cycling of lithium-oxygen batteries. The formation of defective film with improved charge transport and large contact area with a catalyst plays a critical role in the facile decomposition of discharge products and the sustained stability of the battery. Multistaged discharge constructing lithium peroxide-based heterostructure with band discontinuities and a relatively low lithium diffusion barrier may be responsible for the growth of defective film-like discharge products. This strategy offers a promising route for future development of cathode catalysts that can be used to extend the cycling life of lithium-oxygen batteries.

2.
Nanoscale ; 11(38): 17860-17868, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31553002

RESUMO

In this work, the impact of oxygen vacancies and nitrogen-doped carbon coating on the sodium-ion storage properties of anatase TiO2 has been demonstrated. Oxygen vacancies and nitrogen-doped carbon coating were introduced simultaneously by the calcination of core-shell structured TiO2 spheres in a reducing atmosphere. Compared to the anatase TiO2 with and without oxygen vacancies, TiO2-x@NC exhibits much better electrochemical performance in the storage of sodium ions. A high reversible capacity of 245.6 mA h g-1 is maintained at 0.1 A g-1 after 200 cycles, and a high specific capacity of 155.6 mA h g-1 is achieved at a high rate of 5.0 A g-1. The significantly improved electrochemical performance of the core-shell structured anatase TiO2 spheres is attributed to the synergistic effect of the oxygen vacancies in the anatase lattice and surface nitrogen-doped carbon coating. This work provides an efficient strategy for improving the electrochemical performance of metal-oxide-based electrode materials for sodium-ion batteries.

3.
Dalton Trans ; 47(45): 16155-16163, 2018 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-30378603

RESUMO

A top-down method was developed to synthesize hierarchical composites consisting of NiCo2O4 nanocubes and graphene nanosheets through the electrostatic interaction of negatively charged graphene oxide nanosheets and positively charged NiCo2O4 spheres. Employed as anode materials for lithium-ion batteries, the hierarchical composites exhibit remarkably high electrochemical performance, including large reversible capacity, superior rate capability, and excellent cycling performance. Large reversible capacities of 1024 and 648 mA h g-1 are maintained at a current density of 500 and 3000 mA g-1, respectively, for over 200 cycles. The excellent electrochemical performance of the composite is attributed to the synergistic effect of the hierarchical structure, the well dispersed NiCo2O4 nanocubes and the uniform graphene coating. This work provides an effective and promising strategy for the rational structural design of the metal oxide electrode material.

4.
ACS Nano ; 12(11): 11503-11510, 2018 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-30481967

RESUMO

Sodium-ion batteries (SIBs) are generally considered as promising cheap alternatives of lithium-ion batteries for stationary renewable energy storage and have received increasing attention in recent years. The exploration of anode materials with efficient electron transportation is essential for improving the performance of SIBs. Inspired by the signal transfer mode of a neuron, we designed a composite by stringing MoS2 nanoflower (soma) with multiwall carbon nanotubes (MWCNTs) (axons). High-resolution TEM observation reveals a lattice matching growth mechanism of MoS2 nanosheets on the interface of MWCNTs and the lattice expansion of the (002) plane of MoS2. The lattice matching among the MoS2 nanosheet and MWCNT could facilitate electron transfer and structure maintenance upon cycling. The expanded distance of the (002) plane of MoS2 would also promote the sodium-ion intercalation/deintercalation kinetics of the composite. Benefiting from the structural features, when used as an anode material for SIBs, the composite exhibits excellent electrochemical performance, including high specific capacity, excellent cycle stability, and superior rate capabilities. A stable capacity of 527.7 mAh g-1 can be achieved after 110 cycles at a current density of 100 mA g-1. The neuron-inspired design proposed is a promising and efficient strategy for the development of electrode materials for SIBs with high mass transport kinetics and structural stability.

5.
Angew Chem Int Ed Engl ; 57(29): 8865-8870, 2018 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-29859011

RESUMO

Classical organic anode materials for Na-ion batteries are mostly based on conjugated carboxylate compounds, which can stabilize added electrons by the double-bond reformation mechanism. Now, 1,4-cyclohexanedicarboxylic acid (C8 H12 O4 , CHDA) with a non-conjugated ring (-C6 H10 -) connected with carboxylates is shown to undergo electrochemical reactions with two Na ions, delivering a high charge specific capacity of 284 mA h g-1 (249 mA h g-1 after 100 cycles), and good rate performance. First-principles calculations indicate that hydrogen-transfer-mediated orbital conversion from antibonding π* to bonding σ stabilize two added electrons, and reactive intermediate with unpaired electron is suppressed by localization of σ-bonds and steric hindrance. An advantage of CHDA as an anode material is good reversibility and relatively constant voltage. A large variety of organic non-conjugated compounds are predicted to be promising anode materials for sodium-ion batteries.

6.
Small ; 14(27): e1800078, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29750439

RESUMO

Rechargeable aprotic lithium (Li)-O2 batteries with high theoretical energy densities are regarded as promising next-generation energy storage devices and have attracted considerable interest recently. However, these batteries still suffer from many critical issues, such as low capacity, poor cycle life, and low round-trip efficiency, rendering the practical application of these batteries rather sluggish. Cathode catalysts with high oxygen reduction reaction (ORR) and evolution reaction activities are of particular importance for addressing these issues and consequently promoting the application of Li-O2 batteries. Thus, the rational design and preparation of the catalysts with high ORR activity, good electronic conductivity, and decent chemical/electrochemical stability are still challenging. In this Review, the strategies are outlined including the rational selection of catalytic species, the introduction of a 3D porous structure, the formation of functional composites, and the heteroatom doping which succeeded in the design of high-performance cathode catalysts for stable Li-O2 batteries. Perspectives on enhancing the overall electrochemical performance of Li-O2 batteries based on the optimization of the properties and reliability of each part of the battery are also made. This Review sheds some new light on the design of highly active cathode catalysts and the development of high-performance lithium-O2 batteries.

7.
Angew Chem Int Ed Engl ; 57(23): 6825-6829, 2018 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-29654611

RESUMO

Free-standing macroporous air electrodes with enhanced interfacial contact, rapid mass transport, and tailored deposition space for large amounts of Li2 O2 are essential for improving the rate performance of Li-O2 batteries. An ordered mesoporous carbon membrane with continuous macroporous channels was prepared by inversely topological transformation from ZnO nanorod array. Utilized as a free-standing air cathode for Li-O2 battery, the hierarchically porous carbon membrane shows superior rate performance. However, the increased cross-sectional area of the continuous macropores on the cathode surface leads to a kinetic overpotential with large voltage hysteresis and linear voltage variation against Butler-Volmer behavior. The kinetics were investigated based on the rate-determining step of second electron transfer accompanied by migration of Li+ in solid or quasi-solid intermediates. These discoveries shed light on the design of the air cathode for Li-O2 batteries with high-rate performance.

8.
Dalton Trans ; 47(14): 4885-4892, 2018 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-29546260

RESUMO

The development of sustainable and low cost electrode materials for sodium-ion batteries has attracted considerable attention. In this work, a carbon composite material decorated with in situ generated ZnS nanoparticles has been prepared via a simple pyrolysis of the rubber powder from dumped tires. Upon being used as an anode material for sodium-ion batteries, the carbon composite shows a high reversible capacity and rate capability. A capacity as high as 267 mA h g-1 is still retained after 100 cycles at a current density of 50 mA g-1. The well dispersed ZnS nanoparticles in carbon significantly enhance the electrochemical performance. The carbon composites derived from the rubber powder are proposed as promising electrode materials for low-cost, large-scale energy storage devices. This work provides a new and effective method for the reuse of dumped tires, contributing to the recycling of valuable waste resources.

9.
ACS Appl Mater Interfaces ; 9(39): 33934-33940, 2017 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-28898044

RESUMO

Developing efficient sodium-ion-storage mechanisms to increase the energy capacity in organic electrodes is a critical issue even after this period of prolonged effort. Uric acid (UA), a simple organic compound with three carbonyl groups is demonstrated to be electrochemically active in the insertion/extraction of Na ions. Theoretical calculations and experimental characterizations reveal that the sodium-ion storage by UA is a result of the stepwise mechanisms of p-π conjugation and the carbon anion. Aside from C═O, the functional group C═C(NH-)2 also provides an efficient Na-storage activated site in which the lone-pair electrons is stabilized through the planar-to-tetrahedral structural transition and low-energy orbital hybridization of N atoms. For further improvement of the electrochemical performance, a uric acid and carbon nanotube (UA@CNT) composite is prepared via a vacuum solution impregnation method. When employed as an anode material for sodium-ion batteries, the UA@CNT composite exhibits high specific capacity, excellent rate capability, and long cycling life even at high current densities. A reversible capacity of over 163 mA h g-1 is maintained even after 150 cycles at a current density of 200 mA g-1. The present study paves a way to develop reversible high-capacity organic electrode materials for sodium-ion batteries by a carbon-anion stabilization mechanism.

10.
Dalton Trans ; 46(15): 5025-5032, 2017 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-28350408

RESUMO

Sodium-ion batteries have attracted considerable attention in recent years. In order to promote the practical application of sodium-ion batteries, the electrochemical performances, such as specific capacity, reversibility, and rate capability of the anode materials, should be further improved. In this work, a Fe2O3/C composite with a well-ordered mesoporous structure is prepared via a facile co-impregnation method by using mesoporous silica SBA-15 as a hard template. When used as an anode material for sodium-ion batteries, the well-ordered mesoporous structure ensures fast mass transport kinetics. The presence of nano-sized Fe2O3 particles confined within the carbon walls significantly enhances the specific capacity of the composite. The carbon walls in the composite act not only as an active material contributing to the specific capacity, but also as a conductive matrix improving the cycling stability of Fe2O3 nanoparticles. As a result, the well-ordered mesoporous Fe2O3/C composite exhibits high specific capacity, excellent cycleability, and high rate capability. It is proposed that this simple co-impregnation method is applicable for the preparation of well-ordered mesoporous transition oxide/carbon composite electrode materials for high performance sodium-ion and lithium-ion batteries.

11.
Nano Lett ; 16(9): 5902-8, 2016 09 14.
Artigo em Inglês | MEDLINE | ID: mdl-27504675

RESUMO

To lower the overpotential of a lithium-oxygen battery, electron transport at the solid-to-solid interface between the discharge product Li2O2 and the cathode catalyst is of great significance. Here we propose a strategy to enhance electron transport property of the cathode catalyst by the replace of oxygen atoms in the generally used metal oxide-based catalysts with nitrogen atoms to improve electron density at Fermi energy after nitridation. Hierarchically porous CoN nanorods were obtained by thermal treatment of Co3O4 nanorods under ammonia atmosphere at 350 °C. Compared with that of the pristine Co3O4 precursor before nitridation, the overpotential of the obtained CoN cathode was significantly decreased. Moreover, specific capacity and cycling stability of the CoN nanorods were enhanced. It is assumed that the discharged products with different morphologies for Co3O4 and CoN cathodes might be closely associated with the variation in the electronic density induced by occupancy of nitrogen atoms into interstitial sites of metal lattice after nitridation. The nitridation strategy for improved electron density proposed in this work is proved to be a simple but efficient way to improve the electrochemical performance of metal oxide based cathodes for lithium-oxygen batteries.

12.
ChemSusChem ; 9(19): 2759-2764, 2016 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-27561212

RESUMO

The preparation of photocatalysts with high activities under visible-light illumination is challenging. We report the rational design and construction of a zirconium-doped anatase catalyst (S-Zr-TiO2 ) with Brønsted acidity and photoactivity as an efficient catalyst for the degradation of phenol under visible light. Electron microscopy images demonstrate that the zirconium sites are uniformly distributed on the sub-10 nm anatase crystals. UV-visible spectrometry indicates that the S-Zr-TiO2 is a visible-light-responsive catalyst with narrower band gap than conventional anatase. Pyridine-adsorption infrared and acetone-adsorption 13 C NMR spectra confirm the presence of Brønsted acidic sites on the S-Zr-TiO2 sample. Interestingly, the S-Zr-TiO2 catalyst exhibits high catalytic activity in the degradation of phenol under visible-light illumination, owing to a synergistic effect of the Brønsted acidity and photoactivity. Importantly, the S-Zr-TiO2 shows good recyclability.


Assuntos
Titânio/química , Zircônio/química , Ácidos/química , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Catálise , Processos Fotoquímicos , Espectrofotometria Ultravioleta
13.
ACS Appl Mater Interfaces ; 8(6): 3868-73, 2016 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-26720145

RESUMO

In this work, hydroquinone resin was used to grow carbon nanotubes directly on Ni foam. The composites were obtained via a simple carbonization method, which avoids using the explosive gaseous carbon precursors that are usually applied in the chemical vapor deposition method. When evaluated as cathode for Li-O2 batteries, the binder-free structure showed enhanced ORR/OER activities, thus giving a high rate capability (12690 mAh g(-1) at 200 mA g(-1) and 3999 mAh g(-1) at 2000 mA g(-1)) and outstanding long-term cycling stability (capacity limited 2000 mAh g(-1), 110 cycles at 200 mA g(-1)). The excellent battery performance provides new insights into designing a low-cost and high-efficiency cathode for Li-O2 batteries.

14.
Chem Commun (Camb) ; 51(63): 12563-6, 2015 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-26152881

RESUMO

The Kirkendall effect was utilized to synthesize mesoporous silicalite-1 zeolite nanocrystals without the involvement of additional templates. The mesopore size as well as the particle size can be easily controlled by nanoscale Kirkendall growth via significantly reducing the amount of water or tetrapropylammonium hydroxide, which were used in large quantities in conventional methods. The Kirkendall growth method is thus suitable for large-scale synthesis of mesoporous MFI zeolites with very high yields but low cost for practical applications.

15.
Dalton Trans ; 44(18): 8678-84, 2015 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-25854214

RESUMO

A novel binder-free electrode for lithium-oxygen batteries has been prepared by electrodepositing a Co3O4 layer onto a pretreated TiO2 fiber mesh, formed on nickel foam by an electrospinning method. The Co3O4 depositing layer is composed of Co3O4 nanoflakes, forming a uniform flower-like porous structure. The Co3O4 nanoflakes within the depositing layer provide a large amount of catalytic active sites for oxygen evolution and reduction reactions. The three-dimensional porous network of the Co3O4 depositing layer can not only facilitate the transportation of ions and electrolyte within the electrode, but also provide plenty of space to accommodate Li2O2 species formed during the discharge process. The Co3O4 spheres embedded in the TiO2 fiber mesh, formed by the treatment of a suspension of cobaltammine precipitate, function as anchors to prevent the detachment of the Co3O4 layer from the current collector, resulting in excellent structural and cycling stability. Only a slight specific capacity decay is observed at full discharge/charge after 80 cycles. This work demonstrates the important factors in the preparation of binder-free cathodes for high performance lithium-oxygen batteries.

16.
Adv Mater ; 27(3): 527-45, 2015 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-25355133

RESUMO

Lithium-ion batteries are regarded as promising energy storage devices for next-generation electric and hybrid electric vehicles. In order to meet the demands of electric vehicles, considerable efforts have been devoted to the development of advanced electrode materials for lithium-ion batteries with high energy and power densities. Although significant progress has been recently made in the development of novel electrode materials, some critical issues comprising low electronic conductivity, low ionic diffusion efficiency, and large structural variation have to be addressed before the practical application of these materials. Surface and interface engineering is essential to improve the electrochemical performance of electrode materials for lithium-ion batteries. This article reviews the recent progress in surface and interface engineering of electrode materials including the increase in contact interface by decreasing the particle size or introducing porous or hierarchical structures and surface modification or functionalization by metal nanoparticles, metal oxides, carbon materials, polymers, and other ionic and electronic conductive species.

17.
ACS Appl Mater Interfaces ; 6(22): 19791-6, 2014 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-25333628

RESUMO

Li4Ti5O12/TiO2 hollow spheres composed of nanoflakes with preferentially exposed Li4Ti5O12 (011) facets have been successfully fabricated via a facile hydrothermal processing route and following calcination. These hollow spheres show good electrochemical performance in terms of high capacity (266 mAh g(-1) at 0.1 A g(-1)), and excellent rate capability (110 mAh g(-1) at 4.0 A g(-1) up to 100 cycles), attributed to unique morphology, preferred facet orientation of the nanoflakes and microscopic structure of the hollow spheres. The preferentially exposed Li4Ti5O12 (011) facets leads to fast lithium insertion/deinsertion processes in materials because of shorten lithium ion diffusion length, proved to be highly effective in improving the electrochemical properties of the hollow spheres. The excellent electrochemical performance makes these hollow spheres promising anode material for lithium ion batteries with high power and energy densities.

18.
Chemistry ; 20(50): 16732-7, 2014 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-25331634

RESUMO

A mild photochemical approach was applied to construct highly coupled metal-semiconductor dyads, which were found to efficiently facilitate the hydrogenation of nitrobenzene. Aniline was produced in excellent yield (>99 %, TOF: 1183) using formic acid as hydrogen source and water as solvent at room temperature. This general and green catalytic process is applicable to a wide range of nitroarenes without the involvement of high-pressure gases or sacrificial additives.

19.
Chem Commun (Camb) ; 50(69): 9961-4, 2014 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-25034037

RESUMO

Sn/SnO nanoparticles are incorporated in crumpled nitrogen-doped graphene nanosheets by a simple melting diffusion method. The resulting composite exhibits large specific capacity, excellent cycling stability and high rate capability as an anode for lithium-ion batteries.

20.
Adv Mater ; 26(35): 6145-50, 2014 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-25047876

RESUMO

Uniform porous silicon hollow nano-spheres are prepared without any sacrificial templates through a magnesio-thermic reduction of mesoporous silica hollow nanospheres and surface modified by the following in situ chemical polymerization of polypyrrole. The porous hollow structure and polypyrrole coating contribute significantly to the excellent structure stability and high electrochemical performance of the nanocomposite.

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