A Dual-Layer Carbon Encapsulation Strategy for Stable Silicon Anodes: Inner Volume Expansion Buffer and Outer...

Silicon anodes represent a promising pathway for next-generation lithium-ion batteries (LIBs) technology, owing to their high theoretical capacity and natural abundance. However, their extensive volume expansion during lithiation and delithiation results in particle pulverization and unstable solid electrolyte interphase (SEI) formation, severely impeding practical deployment. To address these issues, we design a silicon-carbon composite anode (Si@NPC@NC) featuring a sequentially constructed dual-layer carbon architecture with functional differentiation. The inner ZIF-67-derived porous carbon accommodates volume variation and enables ion/electron transport, while the outer polydopamine (PDA)-derived dense carbon layer reinforces structural integrity and stabilizes the electrode/electrolyte interface. The synergistic interaction between the inner buffer layer and outer protective shield effectively mitigates mechanical stress and promotes the formation of a stable SEI. As a result, the Si@NPC@NC anode delivers an initial coulombic efficiency as high as 82%, a high specific capacity of 1183 mAh g^-1 after 200 cycles at 0.2 A g^-1, with 88.2% capacity retention, significantly outperforming unmodified silicon and single-layer carbon-coated anodes. This work provides a rational structural design strategy for stabilizing silicon anodes and may also offer guidance for other high-volume-change anode materials.