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Facile Synthesis of Coaxial CNTs/MnOx-Carbon Hybrid Nanofibers and Their Greatly Enhanced Lithium Storage Performance.

Yang Z, Lv J, Pang H, Yan W, Qian K, Guo T, Guo Z - Sci Rep (2015)

Bottom Line: Carbon nanotubes (CNTs)/MnOx-Carbon hybrid nanofibers have been successfully synthesized by the combination of a liquid chemical redox reaction (LCRR) and a subsequent carbonization heat treatment.The nanostructures exhibit a unique one-dimensional core/shell architecture, with one-dimensional CNTs encapsulated inside and a MnOx-carbon composite nanoparticle layer on the outside.The particular porous characteristics with many meso/micro holes/pores, the highly conductive one-dimensional CNT core, as well as the encapsulating carbon matrix on the outside of the MnOx nanoparticles, lead to excellent electrochemical performance of the electrode.

View Article: PubMed Central - PubMed

Affiliation: National &Local United Engineering Laboratory of Flat Panel Display Technology, Fuzhou University, Fuzhou 350002, P. R. China.

ABSTRACT
Carbon nanotubes (CNTs)/MnOx-Carbon hybrid nanofibers have been successfully synthesized by the combination of a liquid chemical redox reaction (LCRR) and a subsequent carbonization heat treatment. The nanostructures exhibit a unique one-dimensional core/shell architecture, with one-dimensional CNTs encapsulated inside and a MnOx-carbon composite nanoparticle layer on the outside. The particular porous characteristics with many meso/micro holes/pores, the highly conductive one-dimensional CNT core, as well as the encapsulating carbon matrix on the outside of the MnOx nanoparticles, lead to excellent electrochemical performance of the electrode. The CNTs/MnOx-Carbon hybrid nanofibers exhibit a high initial reversible capacity of 762.9 mAhg(-1), a high reversible specific capacity of 560.5 mAhg(-1) after 100 cycles, and excellent cycling stability and rate capability, with specific capacity of 396.2 mAhg(-1) when cycled at the current density of 1000 mAg(-1), indicating that the CNTs/MnOx-Carbon hybrid nanofibers are a promising anode candidate for Li-ion batteries.

No MeSH data available.


Related in: MedlinePlus

XPS high-resolution spectra of the Mn 2p, O1s, and C1s regions of the as-prepared CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers.(a) Mn 2p region of CNTs/MnOx nanofibers; (b) Mn2p region of CNTs/MnOx-Carbon nanofibers; (c) O1s region of CNTs/MnOx nanofibers; (d) O1s region of CNTs/MnOx-Carbon nanofibers; (e) C1s region of CNTs/MnOx nanofibers; (f) C1s region of CNTs/MnOx-carbon nanofibers.
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f4: XPS high-resolution spectra of the Mn 2p, O1s, and C1s regions of the as-prepared CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers.(a) Mn 2p region of CNTs/MnOx nanofibers; (b) Mn2p region of CNTs/MnOx-Carbon nanofibers; (c) O1s region of CNTs/MnOx nanofibers; (d) O1s region of CNTs/MnOx-Carbon nanofibers; (e) C1s region of CNTs/MnOx nanofibers; (f) C1s region of CNTs/MnOx-carbon nanofibers.

Mentions: X-ray photoelectron spectroscopy (XPS) of the MnO2 powders, and the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers was conducted from 0 to 1100 eV. Obvious Mn 2p, O1s, and C1s peaks for the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers were detected, and their high-resolution spectra are shown in Fig. 4(a–f), respectively. The Mn 2p spectrum (Fig. 4(a)) for the CNTs/MnOx hybrid nanofibers comprises two symmetrical peaks with binding energies (BEs) at 642.53 eV and 654.10 eV, which are attributable to Mn 2p3/2 and Mn 2p1/2, respectively. The separation between these two peaks for the CNTs/MnOx hybrid nanofibers is 11.57 eV, which is approximately equal to that for the CNTs/MnOx-Carbon hybrid nanofibers (see Fig. 4(b)), consisting of two symmetrical peaks with binding energies (BEs) at 642.04 eV and 653.57 eV, but the peaks are obviously larger than those for the pure MnO2 nanoparticles (see Fig. S5(a)), which possess two symmetrical peaks with binding energies (BEs) at 642.43 eV and 653.85 eV. The cause is possibly that there is some low valence manganese oxide that is present in both the CNTs/MnOx and the CNTs/MnOx-Carbon hybrid nanofibers reduced by the carbonaceous materials at 500 °Cfor 2 h under argon atmosphere, which is in good accordance with previous reports364243. As for the O1s spectrum in the CNTs/MnOx composite (Fig. 4(c)), the CNTs/MnOx-Carbon composite (Fig. 4(d)), and the pure MnO2 nanoparticles (Fig. S5(b)), the main portion of the response could come from Mn-O bonds in the manganese oxide, as evidenced by the O1s binding energy (BE) peaks at ~529.81 eV (Fig. 4(c)), 529.98 eV (Fig. 4(d)), and 529.67 eV (Fig. S5(b)), while the peaks at 531.24 eV (Fig. 4(c)), 530.37 eV (Fig. 4(d)), and 531.13 eV (Fig. S5(b)) may be attributable to the OH− radical, adsorbed oxygen, or carbonyl groups44, partly arising from the incomplete pyrolysis of the carbon-containing polymer (PVP) during the encapsulation with the carbon matrix. As for the high BE peaks at 532.47 eV (Fig. 4(c)), 532.84 eV (Fig. 4(d)), and 532.73 eV (Fig. S5(b)), they possibly originate from a small amount of absorbed H2O on the outside44. In addition, the use of CNTs, together with the encapsulation in the carbon matrix of the composite nanofibers, possibly leads to the slight reduction in the three fitted O1s peaks compared to the pure α-MnO2 nanoparticles. In the case of the C1s spectrum for the CNTs/MnOx and CNTs/MnOx-Carbon composites (see Fig. 4(e,f)), the strongest peaks at 284.60 eV (Fig. 4(e)) and 284.58 eV (Fig. 4(e)) are attributed to the C-C bonds that exist in the CNTs or the encapsulating carbon matrix, while the following peaks at 286.05 eV (Fig. 4(e)) and 285.09 eV (Fig. 4(f)) are partly attributable to the presence of some oxygen-containing functional groups in the organic matrix after the heat treatment at relatively low temperature (500 °C), including some disordered carbon or oxidant carbon, such as carbon in alcohols44, which is in good accordance with the fitted O1s peaks mentioned above. The remaining two small peaks at 287.17 eV and 288.33 eV (Fig. 4(e)), and the corresponding peaks at 287.24 eV and 291.41 eV (Fig. 4(f)), possibly come from a trace amount of carboxyl in the hybrid samples434445. From a combination of the XRD, FE-SEM, and TEM results, together with the XPS results, it is concluded that the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers, inheriting their one-dimensional morphology from the parent CNT templates, are composed of CNT cores with MnOx or MnOx-Carbon shells, in the form of main phase Mn3O4 and some minor phases of Mn2O3 and MnO, with or without carbon. These one-dimensional CNTs/MnOx-Carbon hybrid nanofibers possess many unique advantages in lithium ion battery application36414243, such as high conductivity, owing to encapsulation of the manganese oxide nanoparticles in the highly conductive carbon matrix, improved Li+ and electrolyte transport in the hybrid nanomaterials because of the micron-size holes/voids/pores formed between the bound/attached CNTs/MnOx-Carbon nanofibers, etc., all of which would favor greatly enhanced electrochemical performance of the electrode as compared with the pure MnO2 nanoparticles and even the CNTs/MnOx hybrid nanofiber electrodes.


Facile Synthesis of Coaxial CNTs/MnOx-Carbon Hybrid Nanofibers and Their Greatly Enhanced Lithium Storage Performance.

Yang Z, Lv J, Pang H, Yan W, Qian K, Guo T, Guo Z - Sci Rep (2015)

XPS high-resolution spectra of the Mn 2p, O1s, and C1s regions of the as-prepared CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers.(a) Mn 2p region of CNTs/MnOx nanofibers; (b) Mn2p region of CNTs/MnOx-Carbon nanofibers; (c) O1s region of CNTs/MnOx nanofibers; (d) O1s region of CNTs/MnOx-Carbon nanofibers; (e) C1s region of CNTs/MnOx nanofibers; (f) C1s region of CNTs/MnOx-carbon nanofibers.
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f4: XPS high-resolution spectra of the Mn 2p, O1s, and C1s regions of the as-prepared CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers.(a) Mn 2p region of CNTs/MnOx nanofibers; (b) Mn2p region of CNTs/MnOx-Carbon nanofibers; (c) O1s region of CNTs/MnOx nanofibers; (d) O1s region of CNTs/MnOx-Carbon nanofibers; (e) C1s region of CNTs/MnOx nanofibers; (f) C1s region of CNTs/MnOx-carbon nanofibers.
Mentions: X-ray photoelectron spectroscopy (XPS) of the MnO2 powders, and the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers was conducted from 0 to 1100 eV. Obvious Mn 2p, O1s, and C1s peaks for the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers were detected, and their high-resolution spectra are shown in Fig. 4(a–f), respectively. The Mn 2p spectrum (Fig. 4(a)) for the CNTs/MnOx hybrid nanofibers comprises two symmetrical peaks with binding energies (BEs) at 642.53 eV and 654.10 eV, which are attributable to Mn 2p3/2 and Mn 2p1/2, respectively. The separation between these two peaks for the CNTs/MnOx hybrid nanofibers is 11.57 eV, which is approximately equal to that for the CNTs/MnOx-Carbon hybrid nanofibers (see Fig. 4(b)), consisting of two symmetrical peaks with binding energies (BEs) at 642.04 eV and 653.57 eV, but the peaks are obviously larger than those for the pure MnO2 nanoparticles (see Fig. S5(a)), which possess two symmetrical peaks with binding energies (BEs) at 642.43 eV and 653.85 eV. The cause is possibly that there is some low valence manganese oxide that is present in both the CNTs/MnOx and the CNTs/MnOx-Carbon hybrid nanofibers reduced by the carbonaceous materials at 500 °Cfor 2 h under argon atmosphere, which is in good accordance with previous reports364243. As for the O1s spectrum in the CNTs/MnOx composite (Fig. 4(c)), the CNTs/MnOx-Carbon composite (Fig. 4(d)), and the pure MnO2 nanoparticles (Fig. S5(b)), the main portion of the response could come from Mn-O bonds in the manganese oxide, as evidenced by the O1s binding energy (BE) peaks at ~529.81 eV (Fig. 4(c)), 529.98 eV (Fig. 4(d)), and 529.67 eV (Fig. S5(b)), while the peaks at 531.24 eV (Fig. 4(c)), 530.37 eV (Fig. 4(d)), and 531.13 eV (Fig. S5(b)) may be attributable to the OH− radical, adsorbed oxygen, or carbonyl groups44, partly arising from the incomplete pyrolysis of the carbon-containing polymer (PVP) during the encapsulation with the carbon matrix. As for the high BE peaks at 532.47 eV (Fig. 4(c)), 532.84 eV (Fig. 4(d)), and 532.73 eV (Fig. S5(b)), they possibly originate from a small amount of absorbed H2O on the outside44. In addition, the use of CNTs, together with the encapsulation in the carbon matrix of the composite nanofibers, possibly leads to the slight reduction in the three fitted O1s peaks compared to the pure α-MnO2 nanoparticles. In the case of the C1s spectrum for the CNTs/MnOx and CNTs/MnOx-Carbon composites (see Fig. 4(e,f)), the strongest peaks at 284.60 eV (Fig. 4(e)) and 284.58 eV (Fig. 4(e)) are attributed to the C-C bonds that exist in the CNTs or the encapsulating carbon matrix, while the following peaks at 286.05 eV (Fig. 4(e)) and 285.09 eV (Fig. 4(f)) are partly attributable to the presence of some oxygen-containing functional groups in the organic matrix after the heat treatment at relatively low temperature (500 °C), including some disordered carbon or oxidant carbon, such as carbon in alcohols44, which is in good accordance with the fitted O1s peaks mentioned above. The remaining two small peaks at 287.17 eV and 288.33 eV (Fig. 4(e)), and the corresponding peaks at 287.24 eV and 291.41 eV (Fig. 4(f)), possibly come from a trace amount of carboxyl in the hybrid samples434445. From a combination of the XRD, FE-SEM, and TEM results, together with the XPS results, it is concluded that the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers, inheriting their one-dimensional morphology from the parent CNT templates, are composed of CNT cores with MnOx or MnOx-Carbon shells, in the form of main phase Mn3O4 and some minor phases of Mn2O3 and MnO, with or without carbon. These one-dimensional CNTs/MnOx-Carbon hybrid nanofibers possess many unique advantages in lithium ion battery application36414243, such as high conductivity, owing to encapsulation of the manganese oxide nanoparticles in the highly conductive carbon matrix, improved Li+ and electrolyte transport in the hybrid nanomaterials because of the micron-size holes/voids/pores formed between the bound/attached CNTs/MnOx-Carbon nanofibers, etc., all of which would favor greatly enhanced electrochemical performance of the electrode as compared with the pure MnO2 nanoparticles and even the CNTs/MnOx hybrid nanofiber electrodes.

Bottom Line: Carbon nanotubes (CNTs)/MnOx-Carbon hybrid nanofibers have been successfully synthesized by the combination of a liquid chemical redox reaction (LCRR) and a subsequent carbonization heat treatment.The nanostructures exhibit a unique one-dimensional core/shell architecture, with one-dimensional CNTs encapsulated inside and a MnOx-carbon composite nanoparticle layer on the outside.The particular porous characteristics with many meso/micro holes/pores, the highly conductive one-dimensional CNT core, as well as the encapsulating carbon matrix on the outside of the MnOx nanoparticles, lead to excellent electrochemical performance of the electrode.

View Article: PubMed Central - PubMed

Affiliation: National &Local United Engineering Laboratory of Flat Panel Display Technology, Fuzhou University, Fuzhou 350002, P. R. China.

ABSTRACT
Carbon nanotubes (CNTs)/MnOx-Carbon hybrid nanofibers have been successfully synthesized by the combination of a liquid chemical redox reaction (LCRR) and a subsequent carbonization heat treatment. The nanostructures exhibit a unique one-dimensional core/shell architecture, with one-dimensional CNTs encapsulated inside and a MnOx-carbon composite nanoparticle layer on the outside. The particular porous characteristics with many meso/micro holes/pores, the highly conductive one-dimensional CNT core, as well as the encapsulating carbon matrix on the outside of the MnOx nanoparticles, lead to excellent electrochemical performance of the electrode. The CNTs/MnOx-Carbon hybrid nanofibers exhibit a high initial reversible capacity of 762.9 mAhg(-1), a high reversible specific capacity of 560.5 mAhg(-1) after 100 cycles, and excellent cycling stability and rate capability, with specific capacity of 396.2 mAhg(-1) when cycled at the current density of 1000 mAg(-1), indicating that the CNTs/MnOx-Carbon hybrid nanofibers are a promising anode candidate for Li-ion batteries.

No MeSH data available.


Related in: MedlinePlus