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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

X-ray diffraction patterns and Raman spectra of as-prepared CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers:(a) XRD CNTs/MnOx and (b) XRD of CNTs/MnOx-Carbon hybrid nanofibers with different valences of manganese oxide (Mn3O4: Hausmannite structure, JCPDS 75–1560; Mn2O3: Bixbyite structure, JCPDS 71–0636; MnO: Manganosite structure, JCPDS 72–1533), as indexed in the patterns; (c) Raman spectra of the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers, respectively.
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f1: X-ray diffraction patterns and Raman spectra of as-prepared CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers:(a) XRD CNTs/MnOx and (b) XRD of CNTs/MnOx-Carbon hybrid nanofibers with different valences of manganese oxide (Mn3O4: Hausmannite structure, JCPDS 75–1560; Mn2O3: Bixbyite structure, JCPDS 71–0636; MnO: Manganosite structure, JCPDS 72–1533), as indexed in the patterns; (c) Raman spectra of the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers, respectively.

Mentions: As illustrated in Supporting Information Fig. S1 and Fig. 1(a), the X-ray diffraction patterns of the as-prepared MnO2, CNTs/MnOx, and CNTs/MnOx-Carbon hybrid nanofibers reveal that the precursors, the manganese oxide nanoparticles, are α-MnO2 with a tetragonal structure (JCPDS 72–1982) (see Fig. S1) and undergo a subsequent phase transition into different valences of manganese oxide, possibly owing to the reducing reaction due to contact with the carbon matrix and CNTs. The manganese oxide in the CNTs/MnOx hybrid nanofibers includes the main phase Mn3O4 with a hausmannite structure (JCPDS 75–1560) and the minor phase Mn2O3 with a bixbyite structure (JCPDS 71–0636) due to the reducing reaction from contact with the CNTs during the carbonization treatment at 500 °C, which is similar to the manganese oxide in CNTs/MnOx-Carbon hybrid nanofibers, except that there is some trace MnO phase in the CNTs/MnOx-Carbon hybrid nanofibers owing to more chances for the manganese oxide nanoparticles to come into contact with the carbon matrix in the composite, according to the intensity of their own X-ray diffraction (XRD) characteristic peaks. The Raman spectra of the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers in 100–1800 cm−1 region are acquired (see Fig. 1(b)). The obvious spectral feature in CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers, where there are the strongest peak around the 1585 cm−1, named as “G” peak, and a very weak peak around the 1345 cm−1, named as “D” peak, possibly originating from the CNTs core in the two composites, belongs to the Raman characteristic of the carbon composite38. Additionally, the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers also exhibit a common spectral feature for all the all manganese oxides, where a relatively stronger phonon band in the 640−660 cm−1 region and a few weak phonon bands in the range from 200 to 480 cm−1 were found3940. The phonon band with large scattering intensity in the range from 640−660 cm−1 were assigned to A1g spectroscopic species with symmetric vibrations ν2(Mn−O) while the weak bands at about 370−200 cm−1 to Mn−O bending vibrations. Most of the vibrations found in these spectra were related to the motion of the oxygen atoms within the MnO6 octahedral units in all kinds of manganese oxides39 including Mn3O4, Mn2O3, MnO and so on, which is in well agreement with the XRD result as described above. Here, the liquid chemical redox reaction (LCRR) at first result in the formation of the special architecture with the CNTs core and the MnO2 nanoparticles shell covered with a thin layer of PVP polymer around them. And the subsequent carbonization treatment processes finally facilitate the conversion from the parent pure α-MnO2 phase into the composite phases of manganese oxide, mainly owing to the reducing reaction between the MnO2 and the carbon matrix at the high temperature36414243, and simultaneously, the carbon shell formation outside of the MnOx nanoparticles originating from the PVP polymer layer covered outside before. These CNTs/MnOx-Carbon hybrid nanofibers, consisting of CNT cores and low-valence manganese oxide-carbon composite shells with excellent conductivity, effectively inherit the one-dimensional structure of the CNTs, which may enhance the conductivity of the hybrid nanofibers, mainly due to their particular architecture with one-dimensional structure, the CNT cores, and the highly conductive carbon matrix coated outside.


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)

X-ray diffraction patterns and Raman spectra of as-prepared CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers:(a) XRD CNTs/MnOx and (b) XRD of CNTs/MnOx-Carbon hybrid nanofibers with different valences of manganese oxide (Mn3O4: Hausmannite structure, JCPDS 75–1560; Mn2O3: Bixbyite structure, JCPDS 71–0636; MnO: Manganosite structure, JCPDS 72–1533), as indexed in the patterns; (c) Raman spectra of the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers, respectively.
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Related In: Results  -  Collection

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f1: X-ray diffraction patterns and Raman spectra of as-prepared CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers:(a) XRD CNTs/MnOx and (b) XRD of CNTs/MnOx-Carbon hybrid nanofibers with different valences of manganese oxide (Mn3O4: Hausmannite structure, JCPDS 75–1560; Mn2O3: Bixbyite structure, JCPDS 71–0636; MnO: Manganosite structure, JCPDS 72–1533), as indexed in the patterns; (c) Raman spectra of the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers, respectively.
Mentions: As illustrated in Supporting Information Fig. S1 and Fig. 1(a), the X-ray diffraction patterns of the as-prepared MnO2, CNTs/MnOx, and CNTs/MnOx-Carbon hybrid nanofibers reveal that the precursors, the manganese oxide nanoparticles, are α-MnO2 with a tetragonal structure (JCPDS 72–1982) (see Fig. S1) and undergo a subsequent phase transition into different valences of manganese oxide, possibly owing to the reducing reaction due to contact with the carbon matrix and CNTs. The manganese oxide in the CNTs/MnOx hybrid nanofibers includes the main phase Mn3O4 with a hausmannite structure (JCPDS 75–1560) and the minor phase Mn2O3 with a bixbyite structure (JCPDS 71–0636) due to the reducing reaction from contact with the CNTs during the carbonization treatment at 500 °C, which is similar to the manganese oxide in CNTs/MnOx-Carbon hybrid nanofibers, except that there is some trace MnO phase in the CNTs/MnOx-Carbon hybrid nanofibers owing to more chances for the manganese oxide nanoparticles to come into contact with the carbon matrix in the composite, according to the intensity of their own X-ray diffraction (XRD) characteristic peaks. The Raman spectra of the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers in 100–1800 cm−1 region are acquired (see Fig. 1(b)). The obvious spectral feature in CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers, where there are the strongest peak around the 1585 cm−1, named as “G” peak, and a very weak peak around the 1345 cm−1, named as “D” peak, possibly originating from the CNTs core in the two composites, belongs to the Raman characteristic of the carbon composite38. Additionally, the CNTs/MnOx and CNTs/MnOx-Carbon hybrid nanofibers also exhibit a common spectral feature for all the all manganese oxides, where a relatively stronger phonon band in the 640−660 cm−1 region and a few weak phonon bands in the range from 200 to 480 cm−1 were found3940. The phonon band with large scattering intensity in the range from 640−660 cm−1 were assigned to A1g spectroscopic species with symmetric vibrations ν2(Mn−O) while the weak bands at about 370−200 cm−1 to Mn−O bending vibrations. Most of the vibrations found in these spectra were related to the motion of the oxygen atoms within the MnO6 octahedral units in all kinds of manganese oxides39 including Mn3O4, Mn2O3, MnO and so on, which is in well agreement with the XRD result as described above. Here, the liquid chemical redox reaction (LCRR) at first result in the formation of the special architecture with the CNTs core and the MnO2 nanoparticles shell covered with a thin layer of PVP polymer around them. And the subsequent carbonization treatment processes finally facilitate the conversion from the parent pure α-MnO2 phase into the composite phases of manganese oxide, mainly owing to the reducing reaction between the MnO2 and the carbon matrix at the high temperature36414243, and simultaneously, the carbon shell formation outside of the MnOx nanoparticles originating from the PVP polymer layer covered outside before. These CNTs/MnOx-Carbon hybrid nanofibers, consisting of CNT cores and low-valence manganese oxide-carbon composite shells with excellent conductivity, effectively inherit the one-dimensional structure of the CNTs, which may enhance the conductivity of the hybrid nanofibers, mainly due to their particular architecture with one-dimensional structure, the CNT cores, and the highly conductive carbon matrix coated outside.

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