Nitrogen ... - ACS Publications

Subscriber access provided by HKU Libraries

Article

Simple synthesis of nanostructured Sn/nitrogen-doped carbon composite using nitrilotriacetic acid as lithium ion battery anode Duck Hyun Youn, Adam Heller, and C. Buddie Mullins Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/acs.chemmater.5b04282 • Publication Date (Web): 08 Feb 2016 Downloaded from http://pubs.acs.org on February 9, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Chemistry of Materials is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 6

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Chemistry of Materials

Simple synthesis of nanostructured Sn/nitrogen-doped carbon composite using nitrilotriacetic acid as lithium ion battery anode Duck Hyun Youn,† Adam Heller,† C. Buddie Mullins†‡* †Department of Chemical Engineering and Department of Chemistry, Center for Electrochemistry, University of Texas at Austin, 78712-0231, United States. ‡Texas Materials Institute, University of Texas at Austin, United States. ABSTRACT: A composite of 3.5 nm Sn nanoparticles dispersed in nitrogen-doped carbon was prepared from low cost precursors, using simple equipment, by the simple process of hydrolyzing at 300°C SnCl4 mixed with nitrilotriacetic acid, then pyrolyzing the complexed SnO2 at 650 °C. The affordable anode made with the composite retained at 0.2 A g-1 specific current a specific capacity of 660 mAhg-1 at the 200th cycle and a 630 mAhg-1 capacity at 400th cycle. At 1 A g-1 specific current the capacity was as 435 mAhg-1.

Introduction The tin lithium ion battery (LIB) anode, cycling between Sn and Li4.4Sn, has an attractive theoretical Coulombic capacity of 994 mAhg-1. Tin also meets other requirements for replacing the presently used graphite anode of LIBs: it is abundant, its price is near 16 USD/kg and it is toxicologically and environmentally safe.1-3 Because the volume of Sn increases by 260 % upon its lithiation to Li4.4Sn and because the associated stress pulverizes the anode, its initially high Coulombic capacity fades.4 The fading has been extensively studied and has been overcome through use of nano-scaled Sn particles (SnNPs); in these, the stress relaxes rapidly and the Lidiffusion distance remains longer than the radius of the particles, even when the nanoparticles are rapidly lithiated.5,6 The SnNPs are, nevertheless, short-lived because they aggregate upon cycling.7 Addressing the aggregation problem, Scrosati and colleagues 8,15 then other teams 8-14 designed nonaggregating Sn-carbon (Sn/C) nanoparticle composite anodes (Table S1); these were made with porous carbons, carbon nanofibers and graphene.8-14 While meeting most or all of the LIB anode performance criteria, cheaper alternatives are probably still needed. Their starting materials or the equipment for their making or their processing was too expensive for utility.10,14 Here we address affordability, showing that a Sn nano-particle carbon composite can be made of inexpensive reactants, using commonly available inexpensive equipment, by a low-cost process. The synthesis might arguably be the simplest ever for fabricating a nano-particle composite. The new composite, Sn/NC, consists of 3.5 nm diameter Sn particles uniformly dispersed in nitrogen-doped carbon (NC). It is formed of SnCl4 and nitrilotriacetic acid (NTA), used to chelate the metal ions 16 and also serving as the source of both carbon and nitrogen. The composite is formed at the moderate temperature of 650 ºC where the initially formed SnO2 crystallites are reduced to the 3.5 nm Sn nanoparticles, which remain

uniformly dispersed. The reversible Coulombic capacity of the resultant Sn/NC anodes is 660 mAhg-1 after 200 cycles and 630 mAhg-1 after 400 cycles, largely matching the performance of the best cycling Sn/C nanoparticle-based LIB anodes (Table S1). Experimental Section Synthesis of Sn/NC (Sn in N-doped Carbon). The R2 Sn/NC was prepared by dissolving 1 g (3.85 millimoles) of anhydrous SnCl4 in 15 ml of deionized water, and adding to the vigorously stirred solution 1.47 g (7.70 millimoles) of nitrilotriacetic acid (NTA). Warning: SnCl4 reacts with humid air to form toxic HCl. After 3 h of stirring, the solution was heated at 300 ℃ for 1.5 h in a muffle furnace and then the resultant solid was calcined at 650 ℃ for 3 h under flowing argon. R1 Sn/NC and R4 Sn/NC were similarly prepared, except that 0.735 g (3.85 millimoles) or 2.94 g (15.4 millimoles) of NTA were added. Unless otherwise stated, Sn/NC refers to the Sn/NC (R2) composite. For comparison, Sn nanopowder (60 – 80 nm) was purchased from US Research Nanomaterials. Synthesis of Sn/C (Sn in Undoped Carbon). 1 g of SnCl4 was dissolved in 15 ml of deionized water, and mixed with 1.61 g of citric acid monohydrate under vigorous stirring. After 3 h of stirring, the solution was heated at 300 ℃ for 1.5 h in a muffle furnace then the resultant solid was calcined at 650 ℃ for 3 h under flowing argon. Material Characterization. A Quanta FEG 650 scanning electron microscope was used for the SEM and FEI imaging; a JEOL, JEM-2100F high resolution transmission electron mi-

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 6

croscope was used for the TEM and for the energy dispersive spectra (EDS). X-ray diffraction (XRD) patterns were obtained with a Rigaku, R-axis Spider. X-ray photoelectron spectra (XPS) were obtained with a Kranos, Axis Ultra DLD. Thermogravimetric analysis (TGA) was performed with air flowing over the samples heated at 10 ℃/min with a MettlerToledo TGA/DSC1. Surface areas were obtained from N2sorption isotherms at 77 °K measured with a Quantachrome Nova 2200e.

Figure 1. Scheme of the synthesis of Sn/NC.

Electrochemical Measurements. The Sn/NC composite was dispersed in water with 90 kDa CMC (carboxymethyl cellulose) binder (Aldrich) and Super P-Li carbon at a 6:2:2 weight ratio. The slurries were coated on a Cu foil using a notch bar and dried at 80 ℃ for 12 h in a vacuum oven. The mass loading of all electrodes was 0.8 - 1.0 mg cm-2. Coin cells were fabricated using a lithium foil as counter and reference electrode, a polypropylene membrane (Celgard 2400) as a separator, and 1.0 M LiPF6 in ethylene carbonate/diethyl carbonate (EC/DEC, 1:1 v/v) as an electrolyte. The cells were galvanostatically charged/ discharged in a potential range of 5 mV – 3 V using a battery tester (Arbin, BT 2143). Electrochemical impedance spectra (EIS) were measured in the 105 to 10-1 Hz range with a modulation amplitude of 5 mV using a potentiostat (CHI 608D, CH Instruments). The EIS spectra were fit by Z-view software.

RESULTS AND DISCUSSION Physicochemical Properties of the Prepared Sn/NC. The scheme of fabricating the Sn/NC nanoparticle composite is shown in Figure 1. SnCl4 and NTA at 1:2 molar ratio are mixed in deionized water with stirring; the mixture is heated to 300 ℃ in air for 1.5 h to hydrolyze the SnCl4 and to form nano-crystallites of SnO2 which are bound and dispersed in the nitrogen-doped carbon-precursor (XRD pattern of Figure S1). The dispersed SnO2 nano-crystallites are then carbothermally reduced to metallic Sn nanoparticles at 650 ℃ for 3 h under argon, while the N-doped carbon is simultaneously formed. Scanning electron micrographs (SEM) and energy dispersive spectral (EDS) mapping images of the Sn/NC composites are respectively shown in Figures 2a and S2. Carbon clusters of ~ 50 um are observed (Figure 2a); the elemental mapping image of carbon (Figure S2) is almost identical with that of nitrogen, consistent with the formation of the nitrogen-doped carbon. The uniformity of the Sn dispersion in the nitrogen-doped carbon is confirmed in Figure 2b, the transmission electron micrograph (TEM) showing uniformly distributed Sn nanoparticles (black spots) of ~ 3.5 nm diameter. Significantly, the Sn nanoparticles do not coalesce at their temperature of formation, 650 °C, even though Sn melts at 232 ℃. The absence of coalescence is attributed to its inhibition by the nitrogendoped carbon.12 The lattice spacings of 0.293 nm and 0.280 nm (Figure 2c) correspond to the reflections of the (200) and (101) planes of metallic Sn. The TEM-EDS mapping images (Figure 2d) are consistent with the SEM-EDS mapping images, the images of carbon, nitrogen and Sn overlapping, as expected for a uniform dispersion of the Sn-nanoparticles in uniformly nitrogen-doped carbon.

Figure 2. a) SEM images of Sn/NC; b) and c) TEM images of Sn/NC ; d) maps of Sn, C and N in the sample marked d).

Figure 3a shows that the XRD pattern of the Sn/NC composite matches the tetragonal Sn reference XRD pattern (01-0862265). The SnO2 associated reflections completely disappear after heating to 650 ℃. In contrast, when the carbon is derived of citric acid and consequently is not nitrogen- doped, the XRD patterns, intense SnO2 reflections persist even after heating to 750 ℃ (Figure S3). Evidently, and as reported in earlier studies, the nitrogen doped carbon or its precursor is a much better SnO2-reducing agent than carbon;18,19 another earlier study showed that the carbothermal reduction of SnO2 by activated charcoal 17 starts only near 750 ℃. Survey X-ray photoelectron spectra (XPS) of the Sn/NC samples show that their nitrogen content is as high as ~12.9 wt % (Figure 3b). They also show the expected presence of Sn, C and O, the dominant peaks being of Sn 3d3/2 at 494.5 eV and Sn 3d5/2 at 486.1 eV. The 486.1 eV binding energy is lower than the 487.3 eV binding energy for Sn4+ and the 487.0 eV binding energy for Sn2+ (Figure 3c); it is, however, higher than the 485.0 eV binding energy of Sn0. It appears that the Sn nanoparticles in Sn/NC comprise a tin-suboxide, possibly because the studied composite was air-exposed.3,20 Deconvolution of the high resolution XPS N 1s spectrum shows peaks at 400.2 and 397.9 eV, respectively corresponding to pyrrolic and pyridinic nitrogens (Figure 3d).21 Nitrogen-doping increases the electrical conductivity of carbon materials and the performance of batteries made with the more conductive carbon is, as expected superior.7 Also, the extended defect sites


Page 3 of 6

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and vacancies induced by nitrogen-doping facilitate more insertion of Li ions as the cycle number increases, resulting in good cycling stability.22 The Brunauer-Emmett-Teller (BET) specific surface area of the Sn/NC composite, derived of its type Ⅳ N2-sorption isotherm (Figure S4a) is 103 m2/g, the average pore diameter is 3.6 nm (Figure S4b). Thermogravimetric analysis (TGA, Figure S5) shows that the Sn/NC composite contains 41.8 wt % of Sn.

cial Sn nanoparticles (without carbon) exhibit rapid capacity fading, providing only 120 mAhg-1 at the 80th cycle, despite their high initially greater than 800 mAhg-1 capacity. The overall performance of the affordable Sn/NC nanocomposite anode closely matches that of the previously reported Sncarbon composite anodes listed in Table S1.3, 7-9, 11-14, 24-27.28-30 Sn/NC samples of different Sn:N-doped carbon ratios were prepared by varying the starting composition of the SnCl4 : NTA molar ratio, denoted as Rx, x being the numerical value of the ratio. Their Sn content was monitored by TGA (Figure S6).

Figure 3. a) XRD patterns of Sn/NC. XPS spectra of the Sn/NC b) survey; c) Sn 3d; and d) N 1s.

Electrochemical Properties of the Prepared Sn/NC. The Sn/NC composite electrodes were galvanostatically charged and discharged in the 0.01 – 3.0 V window at a current density of 200 mAg-1. The voltage profiles of the 1st, 2nd, 10th, 50th, 100th, 200th, and 400th cycles are shown in Figure 4a. The calculated specific capacity values are based on the total mass of the Sn/NC composites, not on the mass of Sn. The first cycle discharge and charge capacities were respectively, as expected for the initially partly electrochemically irreversible reactions high, 1490 and 713 mAhg-1, and correspondingly the initial Coulombic efficiency was low, 48 %.14,23 From the 10th to 400th cycle, the voltage profiles were largely unchanged, implying cycling stability. Figure S5 shows a cyclic voltammogram of the Sn/NC (R2) composite. The small broad and irreversible reduction peak seen in the first cathodic scan is attributed to the formation of the solid electrolyte interphase (SEI). The absence of irreversible peaks at 1.05 or 1.55 V, associated with Sn-catalyzed decomposition of the electrolyte, implies that Sn nanoparticles are well-encapsulated in the Ndoped carbon matrix.7,9 As seen in Figure 4b the Sn/NC anode maintains between the 10th and 200th cycle a stable capacity of 660 mAhg-1 and at the 400th cycle its capacity is still 630 mAhg-1, the capacity fading only by 0.08 mAhg-1 per cycle. The Coulombic efficiency remains greater than 99 %. Figure 4c shows the retained Coulombic capacity of the Sn/NC composite anode when it cycles at rates between 0.2 Ag-1 and 5.0 Ag-1. At the high rate of 1.0 Ag-1, the Coulombic capacity is still as high as 435 mAhg-1, well above the rate of the graphite anode. When the current density is returned to 0.2 Ag-1 the anode recovers its initial capacity of 660 mAhg-1. In sharp contrast, commer-

Figure 4. a) Potential dependence of the specific capacity of the Sn/NC anode; b) Dependences of the specific capacity and the coulombic efficiency on the cycle number at a current density of 0.2 Ag-1; c) Dependence of the specific capacity on the specific current (current per gram).

The samples were characterized by XRD (Figure S7), SEM (Figure S8), and TEM (Figure S9). The TEM images of the Sn/NC (R1) sample in Figure S9a-b show 3.62 (±0.83) nm Sn nanoparticles dispersed in the carbon matrix. Their size is almost identical with the 3.45 (±0.90) nm size in the Sn/NC (R2) nanocomposite and the 3.36 (±0.88) nm size in the Sn/NC (R4) nanocomposite (Figure S9c-f). The higher Snweight fraction in Sn/NC (R1) has more Sn particles than Sn/NC (R2) or Sn/NC (R4). Because that there is practically no difference between the sizes of the Sn particles in the three Sn/NC composites, a particle size difference cannot be the



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

cause of the difference in the performance of the three composites in lithium ion battery anodes seen in Figures 5a and 5b. The electrical conductivities of the three nanocomposites, measured with a four point probe, are listed in Table S2. The electrical conductivity increases with the Sn weight fraction in the composites, the conductivity of Sn/NC(R1) being two orders of magnitude less than the conductivity of either Sn/NC(R2) or Sn/NC(R4). When cycled at a current density of 200 mAg-1 (Figure 5a) the R2 and R4 anodes retained their capacity after 200 cycles, but the capacity of the R1 electrode decreased in the first 80 cycles,

Page 4 of 6

tra (EIS) of the Sn/NC composite electrodes cycled at 0.2 – 5.0 mAhg-1 are shown in Figure 5c. The data were fit to an equivalent circuit and the resultant fitting parameters are listed in Table S2. The diameter of the semicircle at high frequency for the R2 electrode was significantly smaller than that of R1 or R4; the respective charge transfer resistance (Rct) values of R2, R1 and R4 were 71.6 Ω, 175.9 Ω and 85.4 Ω, consistent with the order of the rate capabilities of the electrodes. The much lesser electrical conductivity of the Sn/NC(R1) sample results in a poorer high-rate performance. While Sn/NC(R4) is slightly more conductive than Sn/NC (R2) it contains less Sn (only 22 wt % by TGA, see Figure S6), resulting in a lesser capacity. For these reasons it is Sn/NC(R2) that performs best. CONCLUSIONS The Sn/NC nanocomposite, an affordable homogeneous dispersion of 3.5 nm Sn nanoparticles in a porous nitrogen-doped carbon is made of inexpensive precursors, with simple equipment by a low cost process. The process involves calcining of a mixture of SnCl4 and nitrilotriacetic acid at 2:1 molar ratio. The lithium battery anode made of the Sn/NC composite retains at 200 mAg-1 a specific Coulombic capacity of 660 mAhg-1 at the 200th cycle and a 630 mAhg-1 capacity at the 400th cycle. Its capacity at a 1.0 Ag-1 rate is 435 mAhg-1. The process appears scalable and should provide the sought after affordable, lighter and faster Sn anode of lithium ion batteries.

ASSOCIATED CONTENT Supporting Information. XRD, SEM, TEM, N2-sorption, TGA, CV, and EIS results of the samples. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author * [email protected]

Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

ACKNOWLEDGMENT This work was supported by the Welch Foundation through grants F-1131 (AH) and F-1436 (CBM). D.H.Y. thanks Dr. Byung Hyo Kim and Hunmin Park for experimental assistance and for helpful conversations. Figure 5. Performance of anodes made with 1:1 molar ratio SnCl4:NTA (R1); 1:2 molar ratio SnCl4:NTA (R2); and 1:4 molar ratio SnCl4:NTA (R4). a) Capacity retention upon cycling; b) Dependence of the specific capacities on the specific currents; c) Nyquist plots.

where it stabilized. After 200 cycles the R2 electrode had the highest reversible specific capacity (660 mAhg-1), the R4 and R1 electrodes having respective reversible capacities of 480 and 385 mAhg-1. The R2 anode had also the best rate performance (Figure 5b). At 5.0 Ag-1 the Coulombic capacity of the R2 electrode was 241 mAhg-1; the Coulombic capacities of the R4 and R1 anodes were only 140 mAhg-1 and 121 mAhg-1. Nyquist plots derived of the electrochemical impedance spec-

REFERENCES (1) Scrosati, B.; Garche, J. Lithium batteries: Status, prospects and future. J. Power Sources 2010, 195, 2419-2430. (2) Roy, P.; Srivastava, S. K. Nanostructured anode materials for lithium ion batteries. J. Mater. Chem. A 2015, 3, 2454-2484. (3) Huang, X.; Cui, S.; Chang, J.; Hallac, P. B.; Fell, C. R.; Luo, Y.; Metz, B.; Jiang, J.; Hurley, P. T.; Chen, J. A Hierarchical Tin/Carbon Composite as an Anode for Lithium-Ion Batteries with a Long Cycle Life. Angew. Chem. Int. Ed. 2015, 54, 1490-1493. (4) Wang, B.; Luo, B.; Li, X.; Zhi, L. The dimensionality of Sn anodes in Li-ion batteries. Mater. Today 2012, 15, 544-552. (5) Wang, Y.; Lee, J. Y.; Deivaraj, T. C. Tin Nanoparticle Loaded Graphite Anodes for Li-Ion Battery Applications. J. Electrochem. Soc. 2004, 151, A1804-A1809.


Page 5 of 6

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(6) Kravchyk, K.; Protesescu, L.; Bodnarchuk, M. I.; Krumeich, F.; Yarema, M.; Walter, M.; Guntlin, C.; Kovalenko, M. V. Monodisperse and Inorganically Capped Sn and Sn/SnO2 Nanocrystals for High-Performance Li-Ion Battery Anodes. J. Am. Chem. Soc. 2013, 135, 4199-4202. (7) Zhu, Z.; Wang, S.; Du, J.; Jin, Q.; Zhang, T.; Cheng, F.; Chen, J. Ultrasmall Sn Nanoparticles Embedded in Nitrogen-Doped Porous Carbon As High-Performance Anode for Lithium-Ion Batteries. Nano Lett. 2014, 14, 153-157. (8) Derrien, G.; Hassoun, J.; Panero, S.; Scrosati, B. Nanostructured Sn–C Composite as an Advanced Anode Material in HighPerformance Lithium-Ion Batteries. Adv. Mater. 2007, 19, 2336-2340. (9) Zhang, G.; Zhu, J.; Zeng, W.; Hou, S.; Gong, F.; Li, F.; Li, C. C.; Duan, H. Tin quantum dots embedded in nitrogen-doped carbon nanofibers as excellent anode for lithium-ion batteries. Nano Energy 2014, 9, 61-70. (10) Lee, K. T.; Jung, Y. S.; Oh, S. M. Synthesis of TinEncapsulated Spherical Hollow Carbon for Anode Material in Lithium Secondary Batteries. J. Am. Chem. Soc. 2003, 125, 5652-5653. (11) Xu, Y.; Liu, Q.; Zhu, Y.; Liu, Y.; Langrock, A.; Zachariah, M. R.; Wang, C. Uniform Nano-Sn/C Composite Anodes for Lithium Ion Batteries. Nano Lett. 2013, 13, 470-474. (12) Zhou, X.; Bao, J.; Dai, Z.; Guo, Y.-G. Tin Nanoparticles Impregnated in Nitrogen-Doped Graphene for Lithium-Ion Battery Anodes. J. Phys. Chem. C 2013, 117, 25367-25373. (13) Hwang, J.; Woo, S. H.; Shim, J.; Jo, C.; Lee, K. T.; Lee, J. OnePot Synthesis of Tin-Embedded Carbon/Silica Nanocomposites for Anode Materials in Lithium-Ion Batteries. ACS Nano 2013, 7, 10361044. (14) Li, X.; Dhanabalan, A.; Gu, L.; Wang, C. Three-Dimensional Porous Core-Shell Sn@Carbon Composite Anodes for HighPerformance Lithium-Ion Battery Applications. Adv. Energy Mater. 2012, 2, 238-244. (15) Hassoun, J.; Derrien, G.; Panero, S.; Scrosati, B. A Nanostructured Sn–C Composite Lithium Battery Electrode with Unique Stability and High Electrochemical Performance. Adv. Mater. 2008, 20, 3169-3175. (16) Egli, T. Biodegradation of metal-complexing aminopolycarboxylic acids. J Biosci. Bioeng. 2001, 92, 89-97. (17) Levêque, G.; Abanades, S. Thermodynamic and Kinetic Study of the Carbothermal Reduction of SnO2 for Solar Thermochemical Fuel Generation. Energy Fuels 2014, 28, 1396-1405. (18) Lu, J.; Yang, L.; Xu, B.; Wu, Q.; Zhang, D.; Yuan, S.; Zhai, Y.; Wang, X.; Fan, Y.; Hu, Z. Promotion Effects of Nitrogen Doping into Carbon Nanotubes on Supported Iron Fischer–Tropsch Catalysts for Lower Olefins. ACS Catal. 2014, 4, 613-621.

(19) Chew, L. M.; Kangvansura, P.; Ruland, H.; Schulte, H. J.; Somsen, C.; Xia, W.; Eggeler, G.; Worayingyong, A.; Muhler, M. Effect of nitrogen doping on the reducibility, activity and selectivity of carbon nanotube-supported iron catalysts applied in CO2 hydrogenation. Appl. Catal. A 2014, 482, 163-170. (20) Ding, L.; He, S.; Miao, S.; Jorgensen, M. R.; Leubner, S.; Yan, C.; Hickey, S. G.; Eychmüller, A.; Xu, J.; Schmidt, O. G. Ultrasmall SnO2 Nanocrystals: Hot-bubbling Synthesis, Encapsulation in Carbon Layers and Applications in High Capacity Li-Ion Storage. Sci. Rep. 2014, 4, 4647. (21) Matter, P. H.; Zhang, L.; Ozkan, U. S. The role of nanostructure in nitrogen-containing carbon catalysts for the oxygen reduction reaction. J. Catal. 2006, 239, 83-96. (22) Chang, K.; Geng, D.; Li, X.; Yang, J.; Tang, Y.; Cai, M.; Li, R.; Sun, X. Ultrathin MoS2/Nitrogen-Doped Graphene Nanosheets with Highly Reversible Lithium Storage. Adv. Energy Mater. 2013, 3, 839844. (23) Yu, S.-H.; Lee, D. J.; Park, M.; Kwon, S. G.; Lee, H. S.; Jin, A.; Lee, K.-S.; Lee, J. E.; Oh, M. H.; Kang, K.; Sung, Y.-E.; Hyeon, T. Hybrid Cellular Nanosheets for High-Performance Lithium-Ion Battery Anodes. J. Am. Chem. Soc. 2015, 137, 11954-11961. (24) Luo, B.; Wang, B.; Li, X.; Jia, Y.; Liang, M.; Zhi, L. GrapheneConfined Sn Nanosheets with Enhanced Lithium Storage Capability. Adv. Mater. 2012, 24, 3538-3543. (25) Luo, B.; Wang, B.; Liang, M.; Ning, J.; Li, X.; Zhi, L. Reduced Graphene Oxide-Mediated Growth of Uniform Tin-Core/CarbonSheath Coaxial Nanocables with Enhanced Lithium Ion Storage Properties. Adv. Mater. 2012, 24, 1405-1409. (26) Qin, J.; He, C.; Zhao, N.; Wang, Z.; Shi, C.; Liu, E.-Z.; Li, J. Graphene Networks Anchored with Sn@Graphene as Lithium Ion Battery Anode. ACS Nano 2014, 8, 1728-1738. (27) Grigoriants, I.; Sominski, L.; Li, H.; Ifargan, I.; Aurbach, D.; Gedanken, A. The use of tin-decorated mesoporous carbon as an anode material for rechargeable lithium batteries. Chem. Commun. 2005, 921-923. (28) Sun, J.; Xiao, L.; Jiang, S.; Li, G.; Huang, Y.; Geng, J. Fluorine-Doped SnO2@Graphene Porous Composite for High Capacity Lithium-Ion Batteries. Chem. Mater. 2015, 27, 4594-4603. (29) Zhang, L.; Zhang, G.; Wu, H. B.; Yu, L.; Lou, X. W. Hierarchical Tubular Structures Constructed by Carbon-Coated SnO2 Nanoplates for Highly Reversible Lithium Storage. Adv. Mater. 2013, 25, 2589-2593. (30) Lin, J.; Peng, Z.; Xiang, C.; Ruan, G.; Yan, Z.; Natelson, D.; Tour, J. M. Graphene Nanoribbon and Nanostructured SnO2 Composite Anodes for Lithium Ion Batteries. ACS Nano 2013, 7, 6001-6006.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Table of Contents artwork


Page 6 of 6

Nitrogen ... - ACS Publications

Recommend Documents