Li15Si4 As Potential Charged Anode Material:Cycling Stability and Reactivity Towards Carbonate Electrolyte

In the development of high energy density Li-ion batteries, two elements have drawn the interest of the scientific community due to their low cost and high specific capacity: silicon and sulfur. These two elements are considered next generation’s active materials for anode and cathode, respectively. In order to exploit the advantages given by both materials in terms of specific capacity (and thus specific energy), lithium has to be introduced at the time of manufacturing either on the cathode side (as Li₂S/Si cell) or on the anode side (as Li_xSi_y/S cell). The Li-Si system has been recently investigated as potential source of lithiated anode materials ^1,2, however up to date little is known about their highly exothermal reaction with alkyl carbonate based electrolytes. In this work we address the latter point via in-situ Online Electrochemical Mass Spectrometry (OEMS)³. By monitoring the gas evolution (mainly ethylene) resulting from contacting the metastable phase Li₁₅Si₄ and the non-aqueous electrolyte during a simulated electrolyte filling experiment of a Li-ion cell (Fig. 1), it was possible to get fundamental understanding of the challenges that cell manufacturers will have to face when using lithiated anode materials. The cycling stability of Li₁₅Si₄ as well as the role played by the total electrode surface area were as well thoroughly investigated.

References: 1) Zeilinger M et al., Chem. Mater. 25 (2013), 4623-4632. 2) Ma R. et al., J. Phys. Chem. Lett. 3 (2012), 3555-3558. 3) Tsiouvaras et al., J. Electrochem. Soc. 160(3) (2013), A471-A477