Effect of the Heat Treatment on the Dimensional Stability of Si Electrodes with PVDF Binder

Dimensional stabilities of Si-Graphite-PVDF composite electrodes were investigated with respect to heat treatment temperature using in situ swelling measurement during cycling and direct observation of the cycled Si electrodes. In situ measurements of the electrode thickness revealed that volume expansion of Si composite electrodes using PVDF binder was suppressed by the simple annealing of the electrode at elevated temperature. Direct observations of the cycled Si composite electrodes after 50 cycles clearly showed that the adhesion of Si-graphite-PVDF composite layer to the current collector was highly dependent on the heat treatment temperature. These results showed that heat treatment of Si composite electrode with PVDF binder played an important role of enhancing the cohesion between Si and other components in the electrode as well as the adhesion of coated Si-graphite-PVDF composite layer to the current collector, thereby suppressing volume expansion of the electrode and improving the cycle performance of the Si composite electrode.