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1.
ACS Appl Mater Interfaces ; 9(14): 12445-12452, 2017 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-28338316

RESUMO

Many factors have been brought forward to explain the capacity degradation mechanisms of LiNixCoyMnzO2 (NCM)/graphite cells at extreme conditions such as under high temperature or with high cutoff voltage. However, the main factors dominating the long-term cycling performance under normal operations remain elusive. Quantitative analyses of the electrode surface evolution for a commercial 18650 LiNi0.5Co0.2Mn0.3O2 (NCM523)/graphite cell during ca. 3000 cycles under normal operation are presented. Electrochemical analyses and inductively coupled plasma-optical emission spectroscopy (ICP-OES) confirm lithium inventory loss makes up for ca. 60% of the cell's capacity loss. Electrochemical deterioration of the NCM523 cathode is identified to be another important factor, which accounts for more than 30% of the capacity decay. Irregular primary particle cracking due to the mechanical stress and the phase change aroused from Li-Ni mixing during repetitive cycles are identified to be the main contributors for the NCM cathode deterioration. The amount of transition metal dissolved into electrolyte is determined to be quite low, and the resulting impedance rise after about 3000 cycles is obtained to be twice that of the reference cell, which are not very significant affecting the long-term cycling performance under normal operations.

2.
Small ; 12(43): 6033-6041, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27594675

RESUMO

Currently, the specific capacity and cycling performance of various MoS2 /carbon-based anode materials for Na-ion storage are far from satisfactory due to the insufficient structural stability of the electrode, incomplete protection of MoS2 by carbon, difficult access of electrolyte to the electrode interior, as well as inactivity of the adopted carbon matrix. To address these issues, this work presents the rational design and synthesis of 3D interconnected and hollow nanocables composed of multiwalled carbon@MoS2 @carbon. In this architecture, (i) the 3D nanoweb-like structure brings about excellent mechanical property of the electrode, (ii) the ultrathin MoS2 nanosheets are sandwiched between and doubly protected by two layers of porous carbon, (iii) the hollow structure of the primary nanofibers facilitates the access of electrolyte to the electrode interior, (iv) the porous and nitrogen-doping properties of the two carbon materials lead to synergistic Na-storage of carbon and MoS2 . As a result, this hybrid material as the anode material of Na-ion battery exhibits fast charge-transfer reaction, high utilization efficiency, and ultrastability. Outstanding reversible capacity (1045 mAh g-1 ), excellent rate behavior (817 mAh g-1 at 7000 mA g-1 ), and good cycling performance (747 mAh g-1 after 200 cycles at 700 mA g-1 ) are obtained.

3.
ACS Appl Mater Interfaces ; 8(2): 1398-405, 2016 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-26709711

RESUMO

Transitional metal sulfide/carbon hybrids with well-defined structures could not only maximize the functional properties of each constituent but engender some unique synergistic effects, holding great promise for applications in Li-ion batteries and supercapacitors and for catalysis. Herein, a facile and versatile approach is developed to controllably grow 2D ultrathin MoS2 nanosheets with a large quantity of exposed edges onto various 1D carbons, including carbon nanotubes (CNTs), electrospun carbon nanofibers, and Te-nanowire-templated carbon nanofibers. The typical approach involves the employment of layer-by-layer (LBL) self-assembled polyelectrolyte, which controls spatially the uniform growth and orientation of ultrathin MoS2 nanosheets on these 1D carbons irrespective of their surface properties. Such unique structures of the as-prepared CNTs@MoS2 hybrid are significantly favorable for the fast diffusions of both Li-ions and electrons, satisfying the kinetic requirements of high-power lithium ion batteries. As a result, CNTs@MoS2 hybrids exhibit excellent electrochemical performances for lithium storage, including a high reversible capacity (1027 mAh g(-1)), high-rate capability (610 mAh g(-1) at 5 C), and excellent cycling stability (negligible capacity loss after 200 continuous cycles).

4.
ACS Appl Mater Interfaces ; 7(41): 22927-34, 2015 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-26426361

RESUMO

Hierarchical structured carbon@MoS2 (C@MoS2) microspheres and nanospheres composed of carbon-sandwiched monolayered MoS2 building blocks are synthesized through a facile one-pot polyvinylpyrrolidone (PVP) micelle-assisted hydrothermal route. The dimension and carbon content of C@MoS2 spheres are effectively controlled by singly adjusting the concentration of PVP, which plays the dual functions of soft-template and carbon source. As the anode materials of Li-ion batteries, C@MoS2 nanospheres present considerably higher capacity, better rate behavior and cycling stability than C@MoS2 microspheres. The reasons are attributed to the unique interconnected nanospherical morphology and the internal hierarchical construction of C@MoS2 nanospheres with expanded MoS2/carbon interlayer spacing.

5.
Chem Commun (Camb) ; 51(62): 12459-62, 2015 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-26145722

RESUMO

How to restrain the dissolution of polysulfides from the sulfur cathode is the current research focus of Li-S batteries. Here, we find that moderate dissolution of polysulfides is of great importance for high-efficiency and stable discharge/charge cycling. Both overprotection and inadequate protection of the sulfur cathode are unfavorable for the cycling of Li-S batteries.

6.
Small ; 10(23): 4975-81, 2014 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-25045113

RESUMO

Monodisperse sulfonated polystyrene (SPS) microspheres are employed as both the template and carbon source to prepare MoS2 quasi-hollow microspheres-encapsulated porous carbon. The synthesis procedure involves the hydrothermal growth of MoS2 ultrathin nanosheets on the surface of SPS microspheres and subsequent annealing to remove SPS core. Incomplete decomposition of SPS during annealing due to the confining effect of MoS2 shells leaves residual porous carbon in the interior. When being evaluated as the anode materials of Li-ion batteries, the as-prepared C@MoS2 microspheres exhibit excellent cycling stability (95% of capacity retained after 100 cycles) and high rate behavior (560 mAh g(-1) at 5 A g(-1)).

7.
ACS Appl Mater Interfaces ; 5(16): 7671-5, 2013 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-23915302

RESUMO

Hierarchical V2O5 microspheres composed of stacked platelets are fabricated through a facile, low-cost, and energy-saving approach. The preparation procedure involves a room-temperature precipitation of precursor microspheres in aqueous solution and subsequent calcination. Because of this unique structure, V2O5 microspheres manifest a high capacity (266 mA h g(-1)), excellent rate capability (223 mA h g(-1) at a current density 2400 mA g(-1)), and good cycling stability (200 mA h g(-1) after 100 cycles) as cathode materials for lithium-ion batteries.


Assuntos
Fontes de Energia Elétrica , Íons/química , Lítio/química , Eletroquímica , Eletrodos , Microesferas , Compostos de Vanádio/química
8.
Nanoscale ; 5(15): 6923-7, 2013 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-23787809

RESUMO

We report the synthesis of carbon nanotube/TiC hybrid fibers using a polymer-assisted chemical solution approach. Ti metal ions are bound to aqueous polyethyleneimine (PEI) to form precursor solution. Amphiphilic PEI with Ti easily permeates the CNT fibers. Upon annealing in a controlled atmosphere, a homogeneous TiC network is formed in the CNT fibers. The obtained CNT/TiC hybrid fibers show prominent enhancement in mechanical strength and electrical conductivity. The tensile strength and conductivity of CNT/TiC fibers can be improved to 0.67 GPa and 1650 S cm(-1) at room temperature, respectively. More importantly, a tensile modulus as high as 420 GPa has been achieved for the CNT/TiC fibers. Analysis shows that the cross-linking matrix of hard TiC plays a significant role in the improvement of mechanical strength. Furthermore, the electrons are transported in the CNT/TiC fiber by a three dimensional hopping mechanism.

9.
Nanoscale ; 5(4): 1460-4, 2013 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-23314835

RESUMO

In order to explore the potential application of sulfur in aqueous rechargeable batteries, core-shell sulfur-polypyrrole (S@PPy) composites were prepared through a novel one-pot and surfactant-free method. Sulfur exhibits a very high capacity of 473 mA h g(-1) and good cycling stability in an aqueous Li(2)SO(4) electrolyte due to the polypyrrole coating.


Assuntos
Fontes de Energia Elétrica , Reutilização de Equipamento , Polímeros/química , Pirróis/química , Enxofre/fisiologia , Água/química , Transferência de Energia , Desenho de Equipamento , Análise de Falha de Equipamento
10.
Nanoscale ; 5(2): 503-7, 2013 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-23128833

RESUMO

Cobalt phosphite (Co(11)(HPO(3))(8)(OH)(6)) microarchitectures assembled by ultralong nanoribbons are successfully synthesized by a mild hydrothermal condition without any additives. The uniform ultralong nanoribbon has a width of 100 nm and length of 20-30 µm. More importantly, Co(11)(HPO(3))(8)(OH)(6) microarchitectures are also successfully applied as an electrochemical supercapacitor with a good specific capacitance (312 F g(-1) at 1.25 A g(-1)), good rate capability and excellent cycling property (maintaining about 89.4% at 1.25 A g(-1) after 3000 cycles).

11.
Dalton Trans ; 41(43): 13284-91, 2012 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-23023820

RESUMO

Porous ZnO-NiO composite micropolyhedrons have been successfully synthesized by calcination of mixed oxalate (Zn(0.9)Ni(0.1)(C(2)O(4))(2)·nH(2)O) precursors in air. The oxalate precursor micropolyhedrons were synthesized by a mild chemical precipitation method without any template or surfactant, and found to have a relatively low decomposition temperature. We have successfully explored the application of the resulting porous ZnO-NiO composite micropolyhedrons as electrochemical capacitors. Electrochemical study shows that the obtained ZnO-NiO composites under different conditions have different electrochemical supercapacitor properties in 3.0 or 1.0 M KOH solutions. The porous ZnO-NiO micropolyhedron material (P1) obtained by calcination of the oxalate precursor at 400 °C has a large specific capacitance 649.0 F g(-1) in 3.0 M KOH solution and could maintain 99.1% of this value after 400 cycles at 5.8 A g(-1). Even at a high current density of 58.0 A g(-1), the specific capacitance of P1 is 395.2 F g(-1).

12.
Nanoscale ; 4(19): 5946-53, 2012 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-22833216

RESUMO

Various NH(4)CoPO(4)·H(2)O nano/microstructures (oblong plate, microplate, microflower, hierarchical architectures) have been synthesized through a facile chemical precipitation method without surfactants and templates. More importantly, the supercapacitive performances of NH(4)CoPO(4)·H(2)O nano/microstructures were firstly studied using cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy methods in 3.0 M KOH solution. These results indicated that NH(4)CoPO(4)·H(2)O hierarchical architectures electrodes exhibit effective supercapacitive characteristics in aqueous KOH electrolyte. The specific capacitance of NH(4)CoPO(4)·H(2)O electrode is up to 369.4 F g(-1) at a current density of 0.625 A g(-1) and the material has a long cycle life which can maintain 99.7% of initial specific capacitance after 400 cycles.

14.
J Phys Chem B ; 109(7): 2610-6, 2005 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-16851265

RESUMO

The effect of nanosized Al2O3/ZnO fillers on the interactions in PEO-NaSCN polymer electrolytes has been studied by FT-IR, XRD, and DTA measurements. The experimental results are discussed according to the grain boundary effect, the principle of Lewis acid-base, and epitaxial effect. It is shown that the hard Lewis acid centers on the surface of Al2O3 exhibit strong interactions with ether oxygens in PEO, even with ether oxygens that coordinated to Na+. Therefore, the modes of the interaction of Al2O3 with PEO-NaSCN electrolytes are dependent on the salt content. Al2O3 cannot influence the ionic association in P(EO)8NaSCN electrolyte, but do reduce significantly the solvating ability of PEO toward NaSCN in P(EO)60NaSCN electrolyte. However, NaSCN in P(EO)20NaSCN-30%Al2O3 nanocomposite appears as a state that resembles the situation of NaSCN in PEO amorphous phase. In contrast with Al2O3, the epitaxial effect of ZnO is not found in the interested systems where only weaker interaction is observed between ZnO and ether oxygen, and the modes of interaction of ZnO with PEO-NaSCN electrolytes are hardly related to the salt content. In addition, the soft Lewis acid groups on ZnO surface exhibit stronger complexation with SCN- in PEO-NaSCN electrolytes, and both can form the complex anion ZnO...SCN-.

15.
J Phys Chem B ; 109(28): 13676-84, 2005 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-16852714

RESUMO

Temperature dependence of the physiochemical characteristics of a room-temperature ionic liquid consisting of trimethylhexylammonium (TMHA) cation and bis(trifluoromethane) sulfonylimide (TFSI) anion containing different concentrations of LiTFSI salt was examined. Electrochemical properties of a spinel LiMn(2)O(4) electrode in 1 M LiTFSI/TMHA-TFSI ionic electrolyte were investigated at different temperatures by using cyclic voltammetry, galvanostatic measurements, and electrochemical impedance spectroscopy. The Li/ionic electrolyte/LiMn(2)O(4) cell exhibited satisfactory electrochemical properties with a discharge capacity of 108.2 mA h/g and 91.4% coulombic efficiency in the first cycle under room temperature. At decreased temperature, reversible capacity of the cell could not attain a satisfactory value due to the high internal resistance of the cell and the large activation energy for lithium ion transfer through the electrode/electrolyte interface. Anodic electrolyte oxidation results in the decrease of coulombic efficiency with increasing temperature. Irreversible structural conversion of the spinel LiMn(2)O(4) in the ionic electrolyte, possibly associated with the formation of TMHA intercalated compounds and/or Jahn-Teller distortion, was considered to be responsible for the electrochemical decay with increasing cycles.

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