Silicon Anode Coating with Metal Fluoride for Volume Expansion

The patent applies composite materials by combining silicon-based material with carbon-based material and metal fluoride to form a composite anode active material. The carbon-based material forms a coating layer around the silicon-based material, while the metal fluoride is distributed within the composite structure. This composite structure allows the silicon-based material to maintain its high energy density while the carbon-based coating layer constrains volume expansion and prevents pulverization during charging/discharging cycles.

The patent uses metal fluoride as an intermediary component in the composite structure. The metal fluoride is distributed within the composite anode active material, forming intermediate structures that mediate between the silicon-based material and the electrolyte. This intermediary presence prevents direct and irreversible silicon-fluorine bonding with the electrolyte, thereby reducing capacity loss and extending battery lifespan while maintaining high lithium storage capacity.

The patent employs a carbon-based material coating layer that acts as a flexible shell around the silicon-based material. This thin film coating maintains stability during volume changes by flexibly accommodating expansion and contraction of the silicon-based core during charging/discharging cycles. The carbon-based coating layer provides a stable interface that prevents direct exposure of silicon to the electrolyte, thereby stabilizing the SEI layer and improving overall battery performance.