Metallic Copper Binders for Lithium-Ion Battery Silicon Electrodes

High capacity anode materials for lithium-ion batteries typically experience large crystallographic volume expansions due to formation of either alloy or Zintl LixM phases. This phenomena has been observed for several main group metals, including tin, silicon, and germanium, that are being considered for next generation anode materials. Solutions proposed include new morphologies, precursor phases, and organic binders but none have displaced previous binders because of higher costs or they introduce inactive or poorly conducting phases that hurt performance. In this report we have studied an alternative method of binding electrochemically active silicon to the current collector based on a method that utilizes copper as a replacement for both the binder and conductive additive in a standard electrode. For this system we have optimized conditions to maximize the adhesion of the silicon to the copper foil current collector while minimizing formation of binary intermetallic compounds. For compositions around Cu: 4 Si (64 wt% Si), the electrochemical cycle life is comparable to electrodes made using a PVDF polymer binder but with one-third the overall electrode resistance. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.107206jes] All rights reserved.