Si has attracted considerable interest as a promising anode material for next-generation Li-ion batteries owing to its outstanding specific capacity. However, the commercialization of Si anodes has been consistently limited by severe instabilities originating from their significant volume change (approximately 300%) during the charge-discharge process. Herein, we introduce an ultrafast processing strategy of controlled multipulse flash irradiation for stabilizing the Si anode by modifying its physical properties in a spatially stratified manner. We first provide a comprehensive characterization of the interactions between the anode materials and the flash irradiation, such as the condensation and carbonization of binders, sintering, and surface oxidation of the Si particles under various irradiation conditions (e.g., flash intensity and irradiation period). Then, we suggest an effective route for achieving superior physical properties for Si anodes, such as robust mechanical stability, high electrical conductivity, and fast electrolyte absorption, via precise adjustment of the flash irradiation. Finally, we demonstrate flash-irradiated Si anodes that exhibit improved cycling stability and rate capability without requiring costly synthetic functional binders or delicately designed nanomaterials. This work proposes a cost-effective technique for enhancing the performance of battery electrodes by substituting conventional long-term thermal treatment with ultrafast flash irradiation.