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Laser Pyrolysis : a method of interest for the synthesis of amorphous or crystalline Si-core C-shell nanoparticles - application as anode material in Li-Ion batteries

Abstract : Although the Li-ion battery (LIB) currently offers the most suitable balance between power and autonomy for consumer electronics and electric vehicle applications, there continues to be a demand for increased energy capacity. One strategy to increase LiB’s energy density is to replace graphite (372 mAh.g-1) as the anode active material by higher specific capacity materials. Silicon appears as an attractive alternative material thanks to its high theoretical specific capacity (3579 mAh.g-1 for the Li3,75Si phase) and its low discharge potential. Despite being the focus of scientific activity for over 10 years, the use of silicon based anodes have not yet been realized because the performance of these materials degrades rapidly during cycling. Silicon nanostructuration together with association of carbon to Si greatly enhance the performances in terms of both cyclability and capacity. In particular, core-shell silicon-carbon Si@C nanoparticles are attractive candidates as active material to increase the capacity of Li-ion batteries while mitigating the detrimental effects of volume expansion upon lithiation processes. The innovative solution proposed here is to use at the anode nanoparticles of Si@C synthesized in a single step by a scalable continuous gas phase method particularly interesting for industrial production, i.e. the laser pyrolysis method. Moreover, thanks to the control of experimental parameters, this method allows producing an amorphous core of silicon (a-Si) as well as a crystalline one (c-Si); Indeed using a-Si as core material, instead of c-Si, is an considered option not often considered but it appears promising to enhance cyclability because a-Si is not subject to the drastic crystalline state alteration upon its first lithiation. In order to cumulate all the benefits cited above, active material should be a composite of an a-Si core covered with a carbon shell We report the synthesis, in a single-step process, of amorphous silicon nanoparticles coated with a carbon shell (a-Si@C), via a two-stage laser pyrolysis where decomposition of silane and ethylene are conducted in two successive reaction zones. Auger electron spectroscopy and scanning transmission electron microscopy show a carbon shell about 1 nm in thickness which prevents detrimental oxidation of the a-Si cores. The advantages of the a-Si@C material will be emphasized by comparison with c-Si@C material used as active materials. In particular, cyclic voltammetry demonstrates that the amorphous core-shell composite reaches its maximal lithiation during the first sweep, which is attributed to the amorphous core. After 500 charge/discharge cycles, it retains a capacity of 1250 mAh.g-1 at a C/5 rate and 800 mAh.g-1 at 2C, with an outstanding coulombic efficiency of 99.95 %. Moreover, postmortem observations show an electrode expansion of less than 20% in volume where the nanostructuration is preserved
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Conference papers
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https://hal-cea.archives-ouvertes.fr/cea-02351616
Contributor : Serge Palacin <>
Submitted on : Wednesday, November 6, 2019 - 2:49:21 PM
Last modification on : Monday, February 10, 2020 - 6:14:05 PM

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  • HAL Id : cea-02351616, version 1

Citation

John P. Alper, Julien Sourice, Florent Boismain, Adrien Boulineau, Cécile Reynaud, et al.. Laser Pyrolysis : a method of interest for the synthesis of amorphous or crystalline Si-core C-shell nanoparticles - application as anode material in Li-Ion batteries. MRS Fall Meeting, Nov 2016, Boston, United States. ⟨cea-02351616⟩

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