Toward silicon anodes for next-generation lithium ion batteries: a comparative performance study of various polymer binders and silicon nanopowders.

Silicon is widely regarded as one of the most promising anode materials for lithium ion and next-generation lithium batteries because of its high theoretical specific capacity. However, major issues arise from the large volume changes during alloying with lithium. In recent years, much effort has been spent on preparing nanostructured silicon and optimizing various aspects of material processing with the goal of preserving the electrode integrity upon lithiation/delithiation. The performance of silicon anodes is known to depend on a large number of parameters and, thus, the general definition of a "standard" is virtually impossible. In this work, we conduct a comparative performance study of silicon anode tapes prepared from commercially available materials while using both a well-defined electrode configuration and cycling method. Our results demonstrate that the polymer binder has a profound effect on the cell performance. Furthermore, we show that key parameters such as specific capacity, capacity retention, rate capability, and so forth can be strongly affected by the choice of silicon material, polymer binder and electrolyte system - even the formation of metastable crystalline Li15Si4 is found to depend on the electrode composition and low potential exposure time. Overall, the use of either poly(acrylic acid) with a viscosity-average molecular weight of 450.000 or poly(vinyl alcohol) Selvol 425 in combination with both silicon nanopowder containing a native oxide surface layer of ∼1 nm in diameter and with a monofluoroethylene carbonate-based electrolyte led to improved cycling stability at high loadings.