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Copper nanofiber-networked cobalt oxide composites for high performance Li-ion batteries.

Nam SH, Kim YS, Shim HS, Kim JG, Bae Kim W - Nanoscale Res Lett (2011)

Bottom Line: We prepared a composite electrode structure consisting of copper nanofiber-networked cobalt oxide (CuNFs@CoOx).The copper nanofibers (CuNFs) were fabricated on a substrate with formation of a network structure, which may have potential for improving electron percolation and retarding film deformation during the discharging/charging process over the electroactive cobalt oxide.Such enhanced Li-ion storage performance may be associated with modified electrode structure at the nanoscale, improved charge transfer, and facile stress relaxation from the embedded CuNF network.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Chemdan-gwagiro, Buk-gu, Gwangju 500-712, South Korea. wbkim@gist.ac.kr.

ABSTRACT
We prepared a composite electrode structure consisting of copper nanofiber-networked cobalt oxide (CuNFs@CoOx). The copper nanofibers (CuNFs) were fabricated on a substrate with formation of a network structure, which may have potential for improving electron percolation and retarding film deformation during the discharging/charging process over the electroactive cobalt oxide. Compared to bare CoOxthin-film (CoOxTF) electrodes, the CuNFs@CoOxelectrodes exhibited a significant enhancement of rate performance by at least six-fold at an input current density of 3C-rate. Such enhanced Li-ion storage performance may be associated with modified electrode structure at the nanoscale, improved charge transfer, and facile stress relaxation from the embedded CuNF network. Consequently, the CuNFs@CoOxcomposite structure demonstrated here can be used as a promising high-performance electrode for Li-ion batteries.

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Microstructural properties. (a) x-ray diffraction patterns of the CuNFs, CoOxTF, and CuNFs@CoOxon a stainless steel disc. For the case of CuNFs, we loaded a large amount of CuNFs to acquire a significant signal. The asterisk mark can be indexed to the stainless steel substrate; (b) x-ray photoelectron spectrum for Co 2p3/2 and 2p1/2 of the sputtered CoOx.
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Figure 2: Microstructural properties. (a) x-ray diffraction patterns of the CuNFs, CoOxTF, and CuNFs@CoOxon a stainless steel disc. For the case of CuNFs, we loaded a large amount of CuNFs to acquire a significant signal. The asterisk mark can be indexed to the stainless steel substrate; (b) x-ray photoelectron spectrum for Co 2p3/2 and 2p1/2 of the sputtered CoOx.

Mentions: The crystalline information and chemical composition of deposited electrode materials have been elucidated by XRD and XPS. Figure 2a compares the XRD patterns of CuNFs, CoOxTF, and CuNFs@CoOx, respectively. The sputtered CoOxon the stainless steel substrate indicated an amorphous nature because the diffraction pattern did not show any crystalline peaks from cobalt oxides, except the well-defined peaks from the stainless steel disc. The amorphous phase typically exhibits a high capacity and good cycling performance due to the internal stress relaxation generated by discharge/charge process [10]. The characteristic peaks of the CuNFs were observed at the expected diffraction angles from the Cu(111) and Cu(200) planes [JCPDS 04-0836]. In order to confirm the chemical state of deposited CoOx, XPS analysis was employed. In Figure 2b, the deposited CoOxgives two main peaks at 779.8 and 795.1 eV due to the Co 2p3/2 and Co 2p1/2, respectively, together with two satellite peaks at 788.6 and 803.7 eV. The peak splitting between Co 2p3/2 and Co 2p1/2, corresponding to the spin-orbit doublet of the Co 2p, is ca. 15.3 eV, and the weak and broad satellite peak of the Co 2p3/2 appears at ca. 9 eV higher than the main peak. Such a low-intense satellite can be considered as an indication of the Co3O4 phase [11,12], while the satellite peak of the CoO phase is relatively more intense (ca. 30% of the total Co 2p3/2 signal) [13]. These results indicate that the sputtered CoOxis dominantly of Co3O4 phase, which is consistent with its electrochemical properties, as will be discussed later.


Copper nanofiber-networked cobalt oxide composites for high performance Li-ion batteries.

Nam SH, Kim YS, Shim HS, Kim JG, Bae Kim W - Nanoscale Res Lett (2011)

Microstructural properties. (a) x-ray diffraction patterns of the CuNFs, CoOxTF, and CuNFs@CoOxon a stainless steel disc. For the case of CuNFs, we loaded a large amount of CuNFs to acquire a significant signal. The asterisk mark can be indexed to the stainless steel substrate; (b) x-ray photoelectron spectrum for Co 2p3/2 and 2p1/2 of the sputtered CoOx.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211358&req=5

Figure 2: Microstructural properties. (a) x-ray diffraction patterns of the CuNFs, CoOxTF, and CuNFs@CoOxon a stainless steel disc. For the case of CuNFs, we loaded a large amount of CuNFs to acquire a significant signal. The asterisk mark can be indexed to the stainless steel substrate; (b) x-ray photoelectron spectrum for Co 2p3/2 and 2p1/2 of the sputtered CoOx.
Mentions: The crystalline information and chemical composition of deposited electrode materials have been elucidated by XRD and XPS. Figure 2a compares the XRD patterns of CuNFs, CoOxTF, and CuNFs@CoOx, respectively. The sputtered CoOxon the stainless steel substrate indicated an amorphous nature because the diffraction pattern did not show any crystalline peaks from cobalt oxides, except the well-defined peaks from the stainless steel disc. The amorphous phase typically exhibits a high capacity and good cycling performance due to the internal stress relaxation generated by discharge/charge process [10]. The characteristic peaks of the CuNFs were observed at the expected diffraction angles from the Cu(111) and Cu(200) planes [JCPDS 04-0836]. In order to confirm the chemical state of deposited CoOx, XPS analysis was employed. In Figure 2b, the deposited CoOxgives two main peaks at 779.8 and 795.1 eV due to the Co 2p3/2 and Co 2p1/2, respectively, together with two satellite peaks at 788.6 and 803.7 eV. The peak splitting between Co 2p3/2 and Co 2p1/2, corresponding to the spin-orbit doublet of the Co 2p, is ca. 15.3 eV, and the weak and broad satellite peak of the Co 2p3/2 appears at ca. 9 eV higher than the main peak. Such a low-intense satellite can be considered as an indication of the Co3O4 phase [11,12], while the satellite peak of the CoO phase is relatively more intense (ca. 30% of the total Co 2p3/2 signal) [13]. These results indicate that the sputtered CoOxis dominantly of Co3O4 phase, which is consistent with its electrochemical properties, as will be discussed later.

Bottom Line: We prepared a composite electrode structure consisting of copper nanofiber-networked cobalt oxide (CuNFs@CoOx).The copper nanofibers (CuNFs) were fabricated on a substrate with formation of a network structure, which may have potential for improving electron percolation and retarding film deformation during the discharging/charging process over the electroactive cobalt oxide.Such enhanced Li-ion storage performance may be associated with modified electrode structure at the nanoscale, improved charge transfer, and facile stress relaxation from the embedded CuNF network.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Chemdan-gwagiro, Buk-gu, Gwangju 500-712, South Korea. wbkim@gist.ac.kr.

ABSTRACT
We prepared a composite electrode structure consisting of copper nanofiber-networked cobalt oxide (CuNFs@CoOx). The copper nanofibers (CuNFs) were fabricated on a substrate with formation of a network structure, which may have potential for improving electron percolation and retarding film deformation during the discharging/charging process over the electroactive cobalt oxide. Compared to bare CoOxthin-film (CoOxTF) electrodes, the CuNFs@CoOxelectrodes exhibited a significant enhancement of rate performance by at least six-fold at an input current density of 3C-rate. Such enhanced Li-ion storage performance may be associated with modified electrode structure at the nanoscale, improved charge transfer, and facile stress relaxation from the embedded CuNF network. Consequently, the CuNFs@CoOxcomposite structure demonstrated here can be used as a promising high-performance electrode for Li-ion batteries.

No MeSH data available.


Related in: MedlinePlus