a family of carboxylic acid groups containing fluorene / fluorenon copolymers is disclosed as binders of silicon particles in the fabrication of negative electrodes for use with lithium ion batteries . triethyleneoxide side chains provide improved adhesion to materials such as , graphite , silicon , silicon alloy , tin , tin alloy . these binders enable the use of silicon as an electrode material as they significantly improve the cycle - ability of silicon by preventing electrode degradation over time . in particular , these polymers , which become conductive on first charge , bind to the silicon particles of the electrode , are flexible so as to better accommodate the expansion and contraction of the electrode during charge / discharge , and being conductive promote the flow battery current .