High Capacity Silicon Electrodes with Nafion As Binders

Silicon is capable of delivering a high theoretical specific capacity of 3600 mAh/g which is much higher than that of the state-of-the-art graphite based negative electrodes for lithium ion batteries. However, the poor cycle life of silicon electrodes, caused by the large volumetric strain during cycling, limits the commercialization of silicon electrodes. As one of the essential components, the polymeric binder is critical to the performance and durability of lithium ion batteries as it keeps the integrity of electrodes. The binder must be stable as it interacts with the active material and the electrolyte during the life of the battery. In this work, we demonstrate that electrodes consisting of silicon nano particles mixed with commercially available and ion-exchanged Nafion can deliver a high capacity over 2000 mAh/g for 50 cycles. For comparison, the capacity of electrodes made of the same Si nanoparticles mixed with traditional polyvinylidene fluoride (PVDF) faded rapidly. The mechanisms responsible for Nafion’s superior performance as a binder, such as ionic conductivity and stability of the resulting solid-electrolyte interphase, will be reported.