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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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Calculated differential capacity plots. (a) the first cycle; (b) the tenth cycle of the CoOxTF and CuNFs@CoOx. The discharge process represents oxidation, while the charge process represents reduction processes.
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Figure 4: Calculated differential capacity plots. (a) the first cycle; (b) the tenth cycle of the CoOxTF and CuNFs@CoOx. The discharge process represents oxidation, while the charge process represents reduction processes.

Mentions: To elucidate reason of the enhanced performance, the differential capacity was examined. Figure 4a, b was obtained from the first and tenth cycles, respectively. At the first cycle (Figure 4a), the intensity of the CuNFs@CoOxwas larger than that of the CoOxTF, showing higher capacity and faster kinetics of the phase transformation. In Figure 4b, the decreased peak intensity and integral areas could be caused from the irreversible capacity due to the incomplete electrochemical reaction. Herein, it is interesting to find that some amount of previously formed Li2O phase would contribute to the capacity at tenth cycle. The formed Li2O has been generally reported to be electrochemically inactive. However, it was also reported that Li2O below 10 nm could be activated [1]. The activated Li2O can take place in the cyclic voltammetry results [18-20]. Two cathodic peaks at 0.82 and 1.15 V were observed in the first cycle in Figure 4a, but they were shifted to 0.95 and 1.18 V, respectively, in the subsequent cycles as shown in Figure 4b, indicating that the electrochemical reactions might be different from the first cycle. Thus, the electrochemical reactions in the CuNFs@CoOxcomposite with Li ions can involve the following steps [21-23]:


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)

Calculated differential capacity plots. (a) the first cycle; (b) the tenth cycle of the CoOxTF and CuNFs@CoOx. The discharge process represents oxidation, while the charge process represents reduction processes.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Calculated differential capacity plots. (a) the first cycle; (b) the tenth cycle of the CoOxTF and CuNFs@CoOx. The discharge process represents oxidation, while the charge process represents reduction processes.
Mentions: To elucidate reason of the enhanced performance, the differential capacity was examined. Figure 4a, b was obtained from the first and tenth cycles, respectively. At the first cycle (Figure 4a), the intensity of the CuNFs@CoOxwas larger than that of the CoOxTF, showing higher capacity and faster kinetics of the phase transformation. In Figure 4b, the decreased peak intensity and integral areas could be caused from the irreversible capacity due to the incomplete electrochemical reaction. Herein, it is interesting to find that some amount of previously formed Li2O phase would contribute to the capacity at tenth cycle. The formed Li2O has been generally reported to be electrochemically inactive. However, it was also reported that Li2O below 10 nm could be activated [1]. The activated Li2O can take place in the cyclic voltammetry results [18-20]. Two cathodic peaks at 0.82 and 1.15 V were observed in the first cycle in Figure 4a, but they were shifted to 0.95 and 1.18 V, respectively, in the subsequent cycles as shown in Figure 4b, indicating that the electrochemical reactions might be different from the first cycle. Thus, the electrochemical reactions in the CuNFs@CoOxcomposite with Li ions can involve the following steps [21-23]:

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