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Lithium insertion into carbon-rich SiOC ceramics: Influence of pyrolysis temperature on electrochemical properties

Kaspar, Jan and Graczyk-Zajac, Magdalena and Riedel, Ralf (2013):
Lithium insertion into carbon-rich SiOC ceramics: Influence of pyrolysis temperature on electrochemical properties.
In: Journal of Power Sources, 244Elsevier Science Publishing, pp. 450-455, ISSN 03787753,
[Online-Edition: http://dx.doi.org/10.1016/j.jpowsour.2012.11.086],
[Article]

Abstract

Carbon-rich silicon oxycarbide ceramics (SiOC) prepared via thermal conversion of polyorganosiloxane demonstrate high lithiation capacity and reliable rate capability when used as anode material in Li-ion batteries. The electrochemical properties of carbon-rich SiOC are strongly related to microstructure and phase composition, dependent on final pyrolysis temperature. Both, the increasing organization of free carbon segregated within the microstructure and the gradual degradation of the amorphous Si–O–C network with increasing pyrolysis temperature (Tpyr) lead to reduced capacities and changing voltage profiles. Within our study, the highest registered capacity of 660 mAh g−1 for Tpyr = 900 °C dropped below 80 mAh g−1 for SiOC pyrolyzed at 2000 °C. A continuous decrease in capacity is observed, when increasing Tpyr stepwise by 100 °C, which can be explained by major microstructural changes. First, the free carbon within the ceramic microstructure organizes toward higher ordered configurations, as determined by Raman spectroscopy. Second, X-ray powder diffraction demonstrates a decomposition of the amorphous Si–O–C network resulting in SiC crystallization and growth of SiC domains. Simultaneously, FTIR spectroscopy shows a strong increase of Si–C vibration with Tpyr, while Si–O vibration diminishes and almost disappears after annealing at 1700–2000 °C. According to our study we find, that i) increasing carbon organization provides less Li-ion storing sites, ii) gradual Si–O–C network decomposition reduces the structural stability of the free carbon phase and iii) formation of electrochemically inactive SiC account for reduced capacities and changing voltage profiles with increasing Tpyr.

Item Type: Article
Erschienen: 2013
Creators: Kaspar, Jan and Graczyk-Zajac, Magdalena and Riedel, Ralf
Title: Lithium insertion into carbon-rich SiOC ceramics: Influence of pyrolysis temperature on electrochemical properties
Language: English
Abstract:

Carbon-rich silicon oxycarbide ceramics (SiOC) prepared via thermal conversion of polyorganosiloxane demonstrate high lithiation capacity and reliable rate capability when used as anode material in Li-ion batteries. The electrochemical properties of carbon-rich SiOC are strongly related to microstructure and phase composition, dependent on final pyrolysis temperature. Both, the increasing organization of free carbon segregated within the microstructure and the gradual degradation of the amorphous Si–O–C network with increasing pyrolysis temperature (Tpyr) lead to reduced capacities and changing voltage profiles. Within our study, the highest registered capacity of 660 mAh g−1 for Tpyr = 900 °C dropped below 80 mAh g−1 for SiOC pyrolyzed at 2000 °C. A continuous decrease in capacity is observed, when increasing Tpyr stepwise by 100 °C, which can be explained by major microstructural changes. First, the free carbon within the ceramic microstructure organizes toward higher ordered configurations, as determined by Raman spectroscopy. Second, X-ray powder diffraction demonstrates a decomposition of the amorphous Si–O–C network resulting in SiC crystallization and growth of SiC domains. Simultaneously, FTIR spectroscopy shows a strong increase of Si–C vibration with Tpyr, while Si–O vibration diminishes and almost disappears after annealing at 1700–2000 °C. According to our study we find, that i) increasing carbon organization provides less Li-ion storing sites, ii) gradual Si–O–C network decomposition reduces the structural stability of the free carbon phase and iii) formation of electrochemically inactive SiC account for reduced capacities and changing voltage profiles with increasing Tpyr.

Journal or Publication Title: Journal of Power Sources
Volume: 244
Publisher: Elsevier Science Publishing
Uncontrolled Keywords: Li-ion battery; Anode; Carbon-rich SiOC; Influence of pyrolysis; Temperature; High capacity
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
Zentrale Einrichtungen
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 595: Electrical fatigue
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 595: Electrical fatigue > A - Synthesis
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 595: Electrical fatigue > A - Synthesis > Subproject A4: Novel functional ceramics using anionic substitution in oxidic systems
11 Department of Materials and Earth Sciences > Material Science
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres
DFG-Collaborative Research Centres (incl. Transregio)
Date Deposited: 07 Jan 2013 14:16
Official URL: http://dx.doi.org/10.1016/j.jpowsour.2012.11.086
Additional Information:

SFB 595 A4 16th International Meeting on Lithium Batteries (IMLB)

Identification Number: doi:10.1016/j.jpowsour.2012.11.086
Funders: The authors acknowledge the financial support by the Deutsche Forschungsgemeinschaft (DFG), Bonn, Germany within SPP1473/JP8 and SFB 595/A4 program.
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