Gradient Heterogeneous Coatings for Silicon‐Carbon Anodes in Lithium‐Ion Batteries

Abstract Silicon sub‐oxides (SiO _x ) are promising high‐capacity anodes for advanced lithium‐ion batteries but suffer from rapid capacity fade, progressive voltage decay, and inferior rate capability. While monolithic coating strategies (e.g., rigid CVD carbon encapsulation or flexible poly(acrylic acid) (PAA) chemical coupling) partially mitigate volumetric expansion and interfacial instability, their effectiveness is fundamentally constrained by inherent conductivity‐mechanical buffering trade‐offs. This study systematically compares these systems, establishing that carbon layers govern electron transport while PAA matrices reinforce interfacial stabilization. Consequently, this study developes an innovative gradient heterogeneous coating strategy (SiO _x @C/PAA and SiO _x /PAA@C architectures) that resolves the conductivity‐stability paradox through precise coating sequence modulation. Experimental results demonstrate that outer‐layer physicochemical properties dictate overall performance: SiO _x /PAA@C (carbon exterior) delivers superior rate capability (480 mAh g ⁻¹ at 6 A g ⁻¹ ; 120 mAh g ⁻¹ at 4.5 A g ⁻¹ in full cells), while SiO _x @C/PAA (PAA exterior) achieves exceptional cycling stability (89.3% retention after 150 cycles; 81.17% after 650 cycles in full cells). Inner coatings enhance active material stability via microstructural modulation. This approach successfully addresses the tripartite challenges of capacity preservation, rate performance optimization, and industrial scalability, establishing a theoretical framework for hierarchical interface engineering in silicon‐based anodes alongside scalable fabrication protocols for practical implementation.