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1.
Food Chem ; 306: 125625, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31606635

RESUMO

A novel ultrasonic-assisted vacuum drying technique for dehydrating garlic slices to give high quality products was developed. Garlic slices were dried at 60 °C using four methods: ultrasonic-assisted vacuum drying (USVD), vacuum drying (VD), ultrasonic-assisted drying (USD), and convective drying (CD, the control with no vacuum or ultrasonic applied). Drying kinetics, water-content changes, and properties of the garlic slices were assessed. Univariate linear and partial-least-squares regression models were used to predict the properties from low-field nuclear magnetic resonance parameters. USVD gave the shortest drying time (180 min less than CD) and provided a better garlic color and texture, and allicin retention rate than the other methods. Higher correlations between low-field nuclear magnetic resonance parameters and quality properties were found by partial-least-squares regression (PLSR) than by univariate analysis, with the analysis results being credible. Overall, ultrasonic-assisted vacuum drying produced high-quality products with its properties predicted well by low-field nuclear magnetic resonance.


Assuntos
Dessecação/métodos , Alho/química , Ultrassom , Cor , Cinética , Espectroscopia de Ressonância Magnética , Vácuo
2.
J Chromatogr A ; : 460719, 2019 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-31767257

RESUMO

In general, the simultaneous separation and isolation of compounds with a broad polarity range from natural products is a challenge by ordinary high-speed counter-current chromatography (HSCCC). Indeed, the complex solvent system screening methods limit the broader application of HSCCC. We describe herein a rapid and efficient linear gradient CCC (LGCCC) method that enables the separation of flavonoid glycosides with a broad range of KD values from custard apple leaves. Inner-recycling CCC (IRCCC) mode has been further applied for the separation of compounds with similar KD values. Similarly to binary gradient HPLC, the LGCCC mode is achieved by adjustment of the proportion between ethyl acetate (pump A) and n-butanol (pump B) in an ethyl acetate/n-butanol/water solvent system. Various separation factors have been investigated, including separation mode, rotation speed, flow rate, and sample loading. The IRCCC mode has been used for the secondary separation of two epimers with a simple ethyl acetate/water (1:1, v/v) solvent system. Finally, five main flavonoid glycosides have been successfully separated, namely quercetin-3-O-robinobioside (1, 4.8 mg) and rutin (2, 12.1 mg), quercetin-3-O-ß-d-glucoside (3, 4.2 mg), kaempferol-3-O-robinobioside (4, 9.6 mg), and kaempferol-3-O-rutinoside (5, 24.6 mg). The purities of the separated flavonoid glycosides were over 98%, as determined by HPLC. Our study indicates that a suitable combination of LGCCC and IRCCC modes is an effective strategy for separating flavonoid glycosides from custard apple leaves. The mathematical expression of the LGCCC was deduced to illuminate the separation mechanism. It may also be applied to obtain component fractions for the further screening of active compounds from complex natural products.

3.
J Sep Sci ; 42(16): 2621-2627, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31166086

RESUMO

Toddalia asiatica (Linn.) Lam. is a medical plant traditionally used to treat coughs, fevers, and various diseases. Alkaloids are the main active ingredients in Toddalia asiatica (Linn.) Lam., but traditional methods for screening and separation are complex and labor-intensive. In this work, an efficient strategy was developed to rapidly screen, identify, and separate neuraminidase inhibitors from Toddalia asiatica (Linn.) Lam. Ultrafiltration, high performance liquid chromatography, and time-of-flight mass spectrometry were employed for rapid screening and identification of neuraminidase inhibitors. A two-phase solvent system comprising n-hexane/ethyl acetate/methanol/water (5:5:3:7, v/v) was then selected for separation by high-speed counter-current chromatography. A sample loading of 200 mg and a stepwise flow rate were achieved by increasing the flow rate from 2 to 4 mL/min after 4 h. Three main fluoroquinoline alkaloids (haplopine, skimmianine, and 5-methoxydictamnine) along with two coumarins were obtained via one-step separation and their structures were determined by mass spectrometry and nuclear magnetic resonance. In vitro assays revealed skimmianine with half-maximal inhibitory concentration of 16.2 ± 0.7 µmol/L was selected as the potential highest neuraminidase inhibitor. The results suggest that ultrafiltration high performance liquid chromatography-mass spectrometry combined with high-speed counter-current chromatography is efficient for the screening and isolation of neuraminidase inhibitors from complex natural products.

4.
Sci Total Environ ; 663: 38-44, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30708215

RESUMO

Different types of crop straw and their derived biochars and compost treatments have huge potential for carbon sequestration to sustain crop productivity. In this study, cotton straw (straw), cotton straw-derived compost (compost) and cotton straw-derived biochar (biochar) with equivalent carbon (C) content were added to soil and incubated for 30 and 180 days. The C sequestration potential of these organic materials was determined by 13C isotope trace method. The structural characteristic of soil organic carbon (SOC) was analyzed by solid-state 13C NMR spectroscopy. The SOC concentration was measured by wet oxidation and dry combustion methods. The results showed that 50.84%, 41.03% and 38.55% of native SOC were replaced by biochar, compost, and straw, respectively. The carbohydrate C and methoxyl C contents were significantly higher in straw and biochar amendments respectively, while phenolic C and alkyl C were high in compost amendment and a higher proportion of aryl C occurred in biochar treatment. These findings revealed that straw material was easier to be decomposed, but compost and biochar showing better stability.


Assuntos
Sequestro de Carbono , Carvão Vegetal/química , Gossypium/química , Solo/química , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Compostagem
5.
J Sep Sci ; 41(23): 4379-4386, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30302914

RESUMO

An efficient coordination high-speed counter-current chromatography method for the preparative separation of ginkgolic acids from the sarcotesta of Ginkgo biloba L was developed. The type, concentration, and mechanism of the coordination agent were investigated. Following the use of four types of metal salts including silver nitrate, copper chloride, ferric chloride, and aluminium nitrate, n-heptane/ethyl acetate/methanol/acetic acid 5:4:1:1, v/v with 0.20 mol/L silver nitrate as the coordination agent was chosen as the optimum two-phase solvent system. Five main ginkgolic acids including C13:0, C15:0, C15:1, C17:1, and C17:2 were successfully separated with purities greater than 98%. The sample loading was 500 mg, the flow-rate was 2.0 mL/min, rotation speed was 800 rpm and temperature was 20°C. The structures of the separated ginkgolic acids were identified by comparison with standard samples and electrospray ionization mass spectrometry. The introduction of coordination chemistry in high-speed counter-current chromatography is novel and effective for the preparative separation and isolation of ginkgolic acids from the sarcotesta of Ginkgo biloba L and could also be applied to separate compounds which form coordination bonds in other complex natural products.


Assuntos
Ginkgo biloba/química , Extratos Vegetais/isolamento & purificação , Salicilatos/isolamento & purificação , Distribuição Contracorrente , Estrutura Molecular , Extratos Vegetais/química , Salicilatos/química
6.
Molecules ; 23(10)2018 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-30304808

RESUMO

One new monoterpene glycoside (1), one new phenyl glycoside (2), one new caffeoyl derivative (3), were isolated from Scindapsus officinalis (Roxb.) Schott., along with four known compounds (4⁻7). Structures of the isolated compounds were elucidated by extensive analysis of spectroscopic data, especially 2D NMR data and comparison with literatures. All isolates were evaluated for anti-inflammatory activity against nitric oxide (NO) production in vitro. Compounds 3 and 7 exhibited moderate inhibitory effects on NO production with IC50 values of 12.2 ± 0.8 and 18.9 ± 0.3 µM, respectively.


Assuntos
Anti-Inflamatórios/química , Araceae/química , Extratos Vegetais/química , Animais , Anti-Inflamatórios/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Concentração Inibidora 50 , Espectroscopia de Ressonância Magnética , Camundongos , Estrutura Molecular , Óxido Nítrico/biossíntese , Extratos Vegetais/farmacologia , Células RAW 264.7
7.
Fitoterapia ; 129: 54-61, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29894739

RESUMO

Two new alkaloid glycosides (1-2), two new amide alkaloids (3 and 6), and two new amine alkaloids (4 and 5), were isolated from Scindapsus officinalis (Roxb.) Schott., along with four known alkaloids (7-10). Structural elucidation of the isolated compounds was established by spectroscopic analysis, especially 2D NMR techniques and comparison with literatures. The absolute configurations of compounds 1 and 2 were determined by the electronic circular dichroism calculations. Compound 1 represent the first example of alkaloid glycoside found to possess an unprecedented 2,5-methanocyclopenta[b]azepine core. All isolates were evaluated for cytotoxic activity against MCF-7 human breast cancer cell and anti-inflammatory activity against nitric oxide (NO) production in vitro. Compounds 4, 6 and 8 demonstrated moderate cytotoxic effects against MCF-7 cell (IC50 of 11.6, 25.3, and 20.5 µM, respectively), and 1, 7 and 9 exhibited moderate inhibitory effects on NO production (IC50 of 19.8, 30.3, and 11.8 µM, respectively).


Assuntos
Alcaloides/farmacologia , Anti-Inflamatórios/farmacologia , Antineoplásicos Fitogênicos/farmacologia , Araceae/química , Glicosídeos/farmacologia , Alcaloides/isolamento & purificação , Animais , Anti-Inflamatórios/isolamento & purificação , Antineoplásicos Fitogênicos/isolamento & purificação , Glicosídeos/isolamento & purificação , Humanos , Células MCF-7 , Camundongos , Estrutura Molecular , Óxido Nítrico/biossíntese , Caules de Planta/química , Células RAW 264.7
8.
Polymers (Basel) ; 10(6)2018 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-30966644

RESUMO

A highly graphitized carbon on a silicon monoxide (SiO) surface coating at low temperature, based on polymer precursor π⁻π stacking, was developed. A novel conductive and electrochemically stable carbon coating was rationally designed to modify the SiO anode materials by controlling the sintering of a conductive polymer, a pyrene-based homopolymer poly (1-pyrenemethyl methacrylate; PPy), which achieved high graphitization of the carbon layers at a low temperature and avoided silicon carbide formation and possible SiO material transformation. When evaluated as the anode of a lithium-ion battery (LIB), the carbon-coated SiO composite delivered a high discharge capacity of 2058.6 mAh/g at 0.05 C of the first formation cycle with an initial Coulombic efficiency (ICE) of 62.2%. After 50 cycles at 0.1 C, this electrode capacity was 1090.2 mAh/g (~82% capacity retention, relative to the capacity of the second cycle at 0.1 °C rate), and a specific capacity of 514.7 mAh/g was attained at 0.3 C after 500 cycles. Furthermore, the coin-type full cell composed of the carbon coated SiO composite anode and the Li[Ni0.5Co0.2Mn0.3O2] cathode attained excellent cycling performance. The results show the potential applications for using a π⁻π stacking polymer precursor to generate a highly graphitize coating for next-generation high-energy-density LIBs.

9.
Fitoterapia ; 122: 101-106, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28882671

RESUMO

Five new chromone glycosides, officinalisides A (1), B (2), C (3), D (4) and E (5) were isolated from Scindapsus officinalis (Roxb.) Schott., along with six known chromone derivatives, 7-O-α-l-rhamnosyl-nereugenin (6), undulatoside A (7), drynachromoside A (8), drynachromoside B (9), 5,7-dihydroxy-2-methyl chromone(10), 5,7-dihydroxy-2-hydroxymethyl chromone (11). Structural elucidation of the isolated compounds was established by spectroscopic analysis, especially 2D NMR techniques and comparison with literatures. The isolates were evaluated for anti-inflammatory activities in a LPS-stimulated RAW 264.7 model using inhibition of nitric oxide (NO) production as an indicator. Compounds 2, 4 and 10 demonstrated potential anti-inflammatory activity with IC50 values of 16.1, 19.1, and 13.4µM, respectively, compared to the positive control dexamethasone.


Assuntos
Anti-Inflamatórios/química , Araceae/química , Cromonas/química , Glicosídeos/química , Animais , Anti-Inflamatórios/isolamento & purificação , Cromonas/isolamento & purificação , Glicosídeos/isolamento & purificação , Camundongos , Estrutura Molecular , Óxido Nítrico/metabolismo , Caules de Planta/química , Células RAW 264.7
10.
J Sep Sci ; 40(13): 2732-2740, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28544633

RESUMO

Five terpenoids, including two new ones, 3,7-dioxo-tirucalla-8,24-dien-21-oic acid (2) and 3α-acetoxyl-7-oxo-tirucalla-8,24-dien-21-oic acid (3), and three known ones, boscartol A (1), 11-keto-ß-boswellic acid (4), and acetyl-11-keto-boswellic acid (5), have been extracted by the ultrapressure extraction and purified by pH-zone-refining countercurrent chromatography and high-speed countercurrent chromatography from olibanum. For ultrapressure extraction, the optimal condition including 200 MPa of extraction pressure, ethyl acetate of extraction solvent, 1:20 (g/mL) of solid/liquid ratio, and 2 min of extraction time were obtained. For the separation, from 1.5 g of the terpenoid extract, 220.1 mg of 4, 255.5 mg of 5, and 212.3 mg of the mixture of 1, 2, and 3 were obtained by pH-zone-refining countercurrent chromatography under the solvent system of chloroform/ethyl acetate/methanol/water (3:1:3:2, v/v/v/v) with aqueous ammonia and trifluoroacetic acid as retention and eluter agents. The enriched mixture (210 mg) was further separated by conventional high-speed countercurrent chromatography with petroleum ether/ethyl acetate/methanol/water (1:0.8:1.1:0.6, v/v/v/v), yielding 30.1 mg of 1, 35.5 mg of 2, 12.3 mg of 3. The structures of these five terpenoids were elucidated by extensive spectroscopic methods.


Assuntos
Cromatografia Líquida de Alta Pressão , Distribuição Contracorrente , Franquincenso/química , Terpenos/isolamento & purificação , Extratos Vegetais/química
11.
Biochem Pharmacol ; 135: 126-138, 2017 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-28336257

RESUMO

The nuclear factor-κB (NF-κB)-mediated activation of macrophages plays a key role in mucosal immune responses in Crohn's disease (CD). Moreover, increasing evidence shows that the activation of peroxisome proliferator-activated receptor-γ (PPAR-γ) exerts satisfactory anti-inflammatory effects in experimental colitis models, mostly by suppressing NF-κB-mediated macrophage activation. Therefore, exploring therapeutic strategies to activate PPAR-γ and inhibit the NF-κB pathway in colonic macrophages holds great promise for the treatment of CD. In this study, five novel pyrazole-containing indolizine derivatives (B1, B2, B3, B4 and B5) were successfully synthesized and characterized, and their anti-inflammatory activities for CD treatment were also investigated. Among the five compounds, compound B4 effectively decreased the NF-κB-mediated production of the pro-inflammatory cytokine TNF-α in LPS-stimulated peritoneal macrophages. Moreover, compound B4 significantly ameliorated 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced mouse colitis symptoms, including body weight loss, colonic pathological damage and inflammatory cell infiltration. The results of western blotting and luciferase reporter assays indicated that compound B4 activated PPAR-γ and subsequently suppressed NF-κB activation. Conversely, the addition of the PPAR-γ antagonist GW9662 abrogated the anti-inflammatory effects of compound B4 both in vitro and in vivo. In summary, compound B4 activated the PPAR-γ pathway to inhibit downstream NF-κB signaling, which alleviated experimental colitis. Thus, this compound may serve as a potential therapeutic agent for patients with CD.


Assuntos
Colite/metabolismo , Indolizinas/uso terapêutico , NF-kappa B/metabolismo , PPAR gama/metabolismo , Pirazóis/uso terapêutico , Ácido Trinitrobenzenossulfônico/toxicidade , Anilidas/farmacologia , Animais , Colite/induzido quimicamente , Colite/prevenção & controle , Feminino , Indolizinas/farmacologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos ICR , NF-kappa B/antagonistas & inibidores , PPAR gama/antagonistas & inibidores , Substâncias Protetoras/farmacologia , Substâncias Protetoras/uso terapêutico , Pirazóis/farmacologia , Ácido Trinitrobenzenossulfônico/antagonistas & inibidores
12.
ACS Omega ; 2(11): 8075-8085, 2017 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31457356

RESUMO

Polymer-derived silicon carbonitride (SiCN) materials have been synthesized via pyrolyzing from five poly(silylcarbondiimide)s with different contents of carbon (labeled as 1-5#). The morphological and structural measurements show that the SiCN materials are mixtures of nanocrystals of SiC, Si3N4, and graphite. The SiCN materials have been used as anodes for lithium-ion batteries. Among the five polymer-derived SiCN materials, 5#SiCN, derived from dichloromethylvinylsilane and di-n-octyldichlorosilane, has the best cycle stability and a high-rate performance at the low cutoff voltage of 0.01-1.0 V. In lithium-ion half-cells, the specific delithiation capacity of 5#SiCN anode still remains at 826.7 mA h g-1 after 100 charge/discharge cycles; it can even deliver the capacity above 550 mA h g-1 at high current densities of 1.6 and 2 A g-1. In lithium-ion full cells, 5#SiCN anode works well with LiNi0.6Co0.2Mn0.2O2 commercial cathode. The outstanding electrochemical performance of 5#SiCN anode is attributed to two factors: (1) the formation of a stable and compact solid electrolyte interface layer on the anode surface anode, which protects the electrode from cracking during the charge/discharge cycle; and (2) a large amount of carbon component and the less Si3N4 phase in the 5#SiCN structure, which provides an electrochemical reactive and conductive environment in the SiCN structure, benefit the lithiation/delithiation process. In addition, we explore the reason for the capacity fading of these SiCN anodes.

13.
Phys Chem Chem Phys ; 18(44): 30630-30642, 2016 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-27790651

RESUMO

A simple route for the preparation of ZnS nanocrystal/reduced graphene oxide (ZnS/RGO) by a hydrothermal synthesis process was achieved. The chemical composition, morphology, and structural characterization reveal that the ZnS/RGO composite is composed of sphalerite-phased ZnS nanocrystals uniformly dispersed on functional RGO sheets with a high specific surface area. The ZnS/RGO composite was utilized as an anode in the construction of a high-performance lithium-ion battery. The ZnS/RGO composite with appropriate RGO content exhibits a high reversible specific capacity (780 mA h g-1), excellent cycle stability over 100 cycles (71.3% retention), and good rate performance at 2C (51.2% of its capacity when measured at a 0.1C rate). To further investigate this ZnS/RGO anode for practical use in full Li-ion cells, we tested the electrochemical performance of the ZnS/RGO anode at different cut-off voltages for the first time. The presence of RGO plays an important role in providing high conductivity as well as a substrate with a high surface area. This helps alleviate the typically problems associated with volume expansion and shrinkage during prolonged cycling. Additionally, the RGO provides multiple nucleation points that result in a uniformly dispersed film of nanosized ZnS that covers its surface. Thus, the high surface area RGO enables high electronic conductivity and fast charge transfer kinetics for ZnS lithiation/delithiation.

14.
Nano Lett ; 16(9): 5365-72, 2016 09 14.
Artigo em Inglês | MEDLINE | ID: mdl-27501313

RESUMO

The lithium-sulfur (Li-S) rechargeable battery has the benefit of high gravimetric energy density and low cost. Significant research currently focuses on increasing the sulfur loading and sulfur/inactive-materials ratio, to improve life and capacity. Inspired by nature's ant-nest structure, this research results in a novel Li-S electrode that is designed to meet both goals. With only three simple manufacturing-friendly steps, which include slurry ball-milling, doctor-blade-based laminate casting, and the use of the sacrificial method with water to dissolve away table salt, the ant-nest design has been successfully recreated in an Li-S electrode. The efficient capabilities of the ant-nest structure are adopted to facilitate fast ion transportation, sustain polysulfide dissolution, and assist efficient precipitation. High cycling stability in the Li-S batteries, for practical applications, has been achieved with up to 3 mg·cm(-2) sulfur loading. Li-S electrodes with up to a 85% sulfur ratio have also been achieved for the efficient design of this novel ant-nest structure.

15.
ACS Appl Mater Interfaces ; 8(21): 13373-7, 2016 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-27160017

RESUMO

A SiOSnCoC composite anode is assembled using a conductive polymer binder for the application in next-generation high energy density lithium-ion batteries. A specific capacity of 700 mAh/g is achieved at a 1C (900 mA/g) rate. A high active material loading anode with an areal capacity of 3.5 mAh/cm(2) is demonstrated by mixing SiOSnCoC with graphite. To compensate for the lithium loss in the first cycle, stabilized lithium metal powder (SLMP) is used for prelithiation; when paired with a commercial cathode, a stable full cell cycling performance with a 86% first cycle efficiency is realized. By achieving these important metrics toward a practical application, this conductive polymer binder/SiOSnCoC anode system presents great promise to enable the next generation of high-energy lithium-ion batteries.

16.
Nano Lett ; 15(12): 7927-32, 2015 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-26599387

RESUMO

High-tap-density silicon nanomaterials are highly desirable as anodes for lithium ion batteries, due to their small surface area and minimum first-cycle loss. However, this material poses formidable challenges to polymeric binder design. Binders adhere on to the small surface area to sustain the drastic volume changes during cycling; also the low porosities and small pore size resulting from this material are detrimental to lithium ion transport. This study introduces a new binder, poly(1-pyrenemethyl methacrylate-co-methacrylic acid) (PPyMAA), for a high-tap-density nanosilicon electrode cycled in a stable manner with a first cycle efficiency of 82%-a value that is further improved to 87% when combined with graphite material. Incorporating the MAA acid functionalities does not change the lowest unoccupied molecular orbital (LUMO) features or lower the adhesion performance of the PPy homopolymer. Our single-molecule force microscopy measurement of PPyMAA reveals similar adhesion strength between polymer binder and anode surface when compared with conventional polymer such as homopolyacrylic acid (PAA), while being electronically conductive. The combined conductivity and adhesion afforded by the MAA and pyrene copolymer results in good cycling performance for the high-tap-density Si electrode.


Assuntos
Fontes de Energia Elétrica , Eletrodos , Lítio/química , Nanoestruturas , Polímeros/química , Silício/química , Microscopia de Força Atômica
17.
ACS Appl Mater Interfaces ; 7(29): 15726-34, 2015 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-26135049

RESUMO

Copper sulfide nanowires/reduced graphene oxide (CuSNWs/rGO) nanocompsites are successfully synthesized via a facile one-pot and template-free solution method in a dimethyl sulfoxide (DMSO)-ethyl glycol (EG) mixed solvent. It is noteworthy that the precursor plays a crucial role in the formation of the nanocomposites structure. SEM, TEM, XRD, IR and Raman spectroscopy are used to investigate the morphological and structural evolution of CuSNWs/rGO nanocomposites. The as-fabricated CuSNWs/rGO nanocompsites show remarkably improved Li-storage performance, excellent cycling stability as well as high-rate capability compared with pristine CuS nanowires. It obtains a reversible capacity of 620 mAh g(-1) at 0.5C (1C = 560 mA g(-1)) after 100 cycles and 320 mAh g(-1) at a high current rate of 4C even after 430 cycles. The excellent lithium storage performance is ascribed to the synergistic effect between CuS nanowires and rGO nanosheets. The as-formed CuSNWs/rGO nanocomposites can effectively accommodate large volume changes, supply a 2D conducting network and trap the polysulfides generated during the conversion reaction of CuS.

18.
J Am Chem Soc ; 137(7): 2565-71, 2015 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-25646659

RESUMO

Here we describe a class of electric-conducting polymers that conduct electrons via the side chain π-π stacking. These polymers can be designed and synthesized with different chemical moieties to perform different functions, extremely suitable as a conductive polymer binder for lithium battery electrodes. A class of methacrylate polymers based on a polycyclic aromatic hydrocarbon side moiety, pyrene, was synthesized and applied as an electrode binder to fabricate a silicon (Si) electrode. The electron mobilities for PPy and PPyE are characterized as 1.9 × 10(-4) and 8.5 × 10(-4) cm(2) V(-1) s(-1), respectively. These electric conductive polymeric binders can maintain the electrode mechanical integrity and Si interface stability over a thousand cycles of charge and discharge. The as-assembled batteries exhibit a high capacity and excellent rate performance due to the self-assembled solid-state nanostructures of the conductive polymer binders. These pyrene-based methacrylate binders also enhance the stability of the solid electrolyte interphase (SEI) of a Si electrode over long-term cycling. The physical properties of this polymer are further tailored by incorporating ethylene oxide moieties at the side chains to enhance the adhesion and adjust swelling to improve the stability of the high loading Si electrode.

19.
Nano Lett ; 14(11): 6704-10, 2014 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-25314674

RESUMO

Silicon alloys have the highest specific capacity when used as anode material for lithium-ion batteries; however, the drastic volume change inherent in their use causes formidable challenges toward achieving stable cycling performance. Large quantities of binders and conductive additives are typically necessary to maintain good cell performance. In this report, only 2% (by weight) functional conductive polymer binder without any conductive additives was successfully used with a micron-size silicon monoxide (SiO) anode material, demonstrating stable and high gravimetric capacity (>1000 mAh/g) for ∼500 cycles and more than 90% capacity retention. Prelithiation of this anode using stabilized lithium metal powder (SLMP) improves the first cycle Coulombic efficiency of a SiO/NMC full cell from ∼48% to ∼90%. The combination enables good capacity retention of more than 80% after 100 cycles at C/3 in a lithium-ion full cell.

20.
ACS Appl Mater Interfaces ; 6(19): 17111-8, 2014 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-25203598

RESUMO

The mechanical failure at the electrode interfaces (laminate/current collector and binder/particle interfaces) leads to particle isolation and delamination, which has been regarded as one of the main reasons for the capacity decay and cell failure of lithium-ion batteries (LIBs). Polymer binder provides the key function for a good interface property and for maintaining the electrode integrity of LIBs. Triethylene glycol monomethyl ether (TEG) moieties were incorporated into polymethacrylic acid (PMAA) to different extents at the molecular level. Microscratch tests of the graphite electrodes based on these binders indicate that the electrode is more flexible with 5 or 10% TEG in the polymer binders. Crack generation is inhibited by the flexible TEG-containing binder, compared to that of the unmodified PMAA-based electrode, leading to the better cycling performance of the flexible electrode. With a 10% TEG moiety in the binder, the graphite half-cell reaches a reversible capacity of >270 mAh/g at the 1C rate, compared to a value of ∼190 mAh/g for the unmodified PMAA binder.

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