Buffering volume changes of Si nanocomposite anodes

The massive development of Li-ion technology has allowed for massive spreading of portable electronics, as well as for a progressive development of electrical vehicles (EV) with higher driving range. Despite this, the ever-increasing demand in energy density requests for a breakthrough in Li-storage materials. In this context, anode materials alternative to conventional graphite, with improved capacity, have been investigated for several years. Among these, Si plays a special role because of its extremely high theoretical capacity (4200 mAh g-1 corresponding to the formation of a Li22Si4 alloy). Nevertheless, the volume changes of about 300% associated with the alloying/dealloying processes represent a severe limitation to the electrode reversibility, so that actions aimed at counteracting this drawback are needed for the development of durable Si anodes. The electrochemical behaviour of nanocomposite materials, based on commercial Si powder of about 100 nm size in which the volume changes are buffered by dispersing matrixes such as reduced graphene oxide (RGO) or transition metal oxides, is here presented. The electrodes and cells performances, in terms of specific capacity and durability, are optimized by the use of tailored binders and electrolyte formulations. A rationale of the improved behaviour is explored by applying several morphological, structural and electrochemical investigation techniques, with a special focus on electrode/electrolyte interfacial properties. References: 1. M.N. Obrovac, L. Chistensen, Electrochem. Solid State Lett. 7 (2004) A93. 2. F. Maroni, R. Raccichini, A. Birrozzi, G. Carbonari, R. Tossici, F. Croce, R. Marassi, F. Nobili, J. Power Sources 269 (2014) 873.