As the demand for high-energy-density energy storage systems continues to escalate, conventional graphite anodes face fundamental limitations in capacity and cycle life. Now, researchers from Xi'an University of Technology and Fuzhou University, led by Professor Xifei Li, Professor Jiujun Zhang, and their team, have presented a comprehensive review on atomic/molecular layer deposition (ALD/MLD) engineering of silicon interfaces—a breakthrough approach that bridges the gap between theoretical promise and practical application of silicon anodes.
Why This Interface Engineering Matters
Traditional silicon anodes, despite their ultra-high theoretical capacity (3579 mAh g-1), suffer from catastrophic volume expansion (300–400%), unstable solid-electrolyte interphase (SEI), and insufficient interfacial charge transfer. The novel ALD/MLD technology overcomes these limitations by enabling atomic/molecular-scale precision in constructing stable and functionalized interfaces. Unlike conventional coating techniques such as CVD, PVD, or wet chemical methods—which struggle with conformality on complex 3D nanostructures, elevated processing temperatures, or uneven coverage leading to local stress concentration—ALD/MLD offers unique self-limiting surface chemistry. The native oxide layer (SiOₓ) on silicon surfaces provides ideal reactive sites through abundant hydroxyl (−OH) groups, enabling uniform nucleation and layer-by-layer growth with unmatched conformality on high-aspect-ratio structures.
Innovative Design and Mechanism
The ALD/MLD approach constructs diverse functional interfaces including rigid inorganic coatings, flexible organic–inorganic hybrid "metalcone" films, and gradient composites combining rigidity and flexibility. DFT calculations reveal three synergistic mechanisms: First, mechanical confinement and stress dissipation—rigid inorganic coatings (Al2O3, TiO2, ZnO) physically constrain volume expansion, while flexible hybrid coatings (Alucone, Zincone, polyurea) absorb strain energy through molecular chain rotation, achieving uniform stress distribution. Second, ingenious interface chemical design—MLD hybrid coatings actively participate in SEI construction through in-situ transformation, such as Zincone forming conductive LiₓZn alloys and columnar LiF distributions, or fluorinated AlFHQ undergoing irreversible defluorination to seed LiF-rich hybrid SEI. Polar functional groups (C=O, N−H) in polymer coatings coordinate Li⁺, reduce desolvation barriers, and guide selective electrolyte decomposition toward beneficial inorganic species. Third, efficient charge transport—in-situ formed Li₃N acts as fast ionic conductor, Li−Al−O provides mechanical robustness, and LiF/Li2CO3 heterointerfaces introduce electron barriers suppressing side reactions while enhancing ion transport through space-charge effects.
Outstanding Performance
MLD-derived Alucone coatings increase elastic reversibility by over 150% and deliver 1490 mAh g-1 after 500 cycles, while removing native SiOₓ to establish hybrid conductive interfaces. The AlFHQ hybrid coating achieves 862 mAh g-1 at 2000 mA g-1 with LiF-rich SEI (20.6 at% F). Polyurea-coated silicon demonstrates 1010 mAh g-1
