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Amorphous silicon as a negative-electrode material for Li-ion batteries

par Rosso Michel - publié le , mis à jour le

Participants : F. Ozanam, M. Rosso, C. Henry de Villeneuve

PhD students : D. A. Dalla Corte (2013), B.-M. Koo (2017), Y. Feng
Post-Doc : M. Panagopoulou

The most efficient solutions for the high-density storage of electrical energy are currently offered by lithium-ion batteries. Charging and discharging of the battery is performed by transferring lithium ions from between a positive and a negative electrode. We are currently working on silicon-based negative electrodes in order to improve our understanding and the performance of the system. The current limitation of this type of high-capacity electrode is associated with the huge changes in volumes associated with the incorporation and /removing of lithium into and from the electrode.

In collaboration with Saft Company, we have considered the possibility of stabilizing the electrode by grafting an organic layer at the silicon surface (patent with Saft). We have performed a fundamental study of the passivation layer (SEI layer) which forms at the interface. Using in-situ infrared spectroscopy (Fig.1), the formation and evolution of the passivation layer and the lithiation of the amorphous silicon layer can be monitored. Formation and partial loss of the SEI layer is observed on neat amorphous-silicon electrodes ; by grafting a suitable organic layer, the thickness of the SEI layer is stabilized, which significantly improves the reversibility of the system.

Figure 1 : In-situ infrared study of a thin-film electrode. The electrode is an amorphous silicon film deposited on a crystalline silicon prism. During lithiation/delithiation cycles between 2 V and 0.125 V vs. Li/Li+, lithium is selectively incorporated/removed into/from amorphous silicon, and IR spectra can be continuously recorded.

In collaboration with Algerian colleagues (A. Cheriet and N. Gabouze), we discovered that methylated amorphous silicon (a silicon-carbon alloy obtained by PECVD in a low-power regime) was able to sustain volume variations much more efficiently than standard amorphous silicon, which significantly improves the electrode stability (Fig. 2). This result has also been patented. The origin of this improvement has been associated with the incorporation of methyl groups in the material, which introduces nano-voids and lowers the reticulation degree of the silicon network. The detailed behavior of the material is currently under study in collaboration with J. Światowska and P. Marcus (ChimieParisTech), and with Renault Company.

Figure 2 : Reversible capacity of a thin film of methylated amorphous silicon of composition a-Si_1_-_x(CH3)_x:H as a function of the number of lithiation/delithiation cycles. Each cycle lasts for two hours. The non-methylated material (x=0) has a slightly higher initial capacity, but which decreases much faster than that of the film containing 10% of carbon (x = 0.1).

Publications :

"Interphase chemistry of Si electrodes used as anodes in Li-ion batteries", C. Pereira-Nabais, J. Swiatowska, A. Chagnes, F.Ozanam, A. Gohier, P. Tran-Van, C.-S. Cojocaru, M.Cassir, P. Marcus, Appl. Surf. Sci. 266 (2013) 5-16.

"Methylated silicon : A longer cycle-life material for Li-ion batteries", L. Touahir, A. Cheriet, D. A. Dalla Corte, J.-N. Chazalviel, C. Henry de Villeneuve, F. Ozanam, I. Solomon, A. Keffous, N. Gabouze, M. Rosso, Journal of Power Sources 240 (2013) 551-557.

“Effect of lithiation potential and cycling on chemical and morphological evolution of Si thin film electrode studied by ToF-SIMS”, C. Pereira-Nabais, J. Swiatowska, M. Rosso, F. Ozanam, A. Seyeux, A. Gohier, P. Tran-Van, M.Cassir, P. Marcus, ACS Applied Materials & Interfaces 6 (2014) 13023-13033.

“Spectroscopic insight into Li-ion batteries during operation : an alternative infrared approach”, D. A. Dalla Corte, G. Caillon, C. Jordy, J.-N. Chazalviel, M. Rosso, F. Ozanam, Adv. Energy Mater. 6 (2016) 1501768.

“Molecular grafting on silicon anodes : artificial Solid-Electrolyte Interphase and surface stabilization”, D. A. Dalla Corte, A. C. Gouget-Laemmel, K. Lahlil, G. Caillon, C. Jordy, J.-N. Chazalviel, T. Gacoin, M. Rosso, F. Ozanam, Electrochim. Acta 201 (2016) 70-77.