Silicon-containing liquid polymer electrolytes for application in lithium ion batteries

Since the initial discovery of poly(ethylene glycol) (PEG) as a good lithium ion conductor at elevated temperatures, efforts have been made to find ways of incorporating this biocompatible polymer into lithium ion batteries. In areas of research involving implantable medical devices, consumer electronics and automotive power sources, there is a need to develop a 'safe' alternative to the solvent-based, flammable and toxic electrolytes currently employed. However, PEG has been shown to be electrochemically unstable and crystalline at room temperature. In order to overcome these problems, polysiloxanes have been conjugated to PEG in order to improve its conductivity and physical properties. Over the last few years, the group at the University of Wisconsin-Madison has been involved in collaborations with scientists at Argonne National Laboratories, Grinnell College and Quallion LLC to develop commercially viable silicon-containing polymer electrolytes. This mini-review discusses the electrochemical, thermal and physical properties of these electrolytes, and highlights the progress from high molecular weight polysiloxane-based electrolytes to low-viscosity, highly conducting oligosiloxane and silane electrolytes. (C) 2009 Society of Chemical Industry