SCALABLE DESIGN AND SYNTHESIS OF SILICON ANODES WITH ENGINEERED STRUCTURE AND INTERFACES FOR HIGH-ENERGY LI-ION BATTERIES

Muqiao Su

The transition from fossil fuels to sustainable energy system has significantly increased the demand for high-energy lithium-ion (Li-ion) batteries. Silicon (Si) is a promising anode material due to its exceptionally high theoretical capacity (3579 mAh g-1), which is nearly an order of magnitude greater than that of conventional graphite. However, the practical application of Si anodes is severely limited by poor cycling stability caused by large volume expansion (~300%) during lithiation/delithiation. This volume change leads to particle pulverization, unstable solid-electrolyte-interphase (SEI) formation, loss of electrical contact, and eventual electrode failure. Therefore, the development of structurally robust Si anodes that can accommodate volume change is critical.This dissertation presents scalable design and synthesis strategies for Si anodes with engineered structures and interfaces to achieve long-term electrochemical stability. First, a bulk-core porous-shell silicon (BPSi) architecture was developed via controlled Mg–Si reaction, air oxidation, and acid leaching, demonstrating the importance of hierarchical structural design in mitigating mechanical degradation. Second, interfacial engineering was achieved through polydopamine (PDA)-derived carbon coating, where a “Goldilocks” regime of carbon content and coating thickness was identified to balance conductivity, surface stability, and lithium-ion transport. Third, a scalable synthesis route for carbon-coated book-like silicon nanosheets was established through controlled oxidation of CaSi2 in CO2, enabling simultaneous formation of a two-dimensional (2D) nanosheet structure and in-situ carbon incorporation. Systematic investigation of synthesis parameters revealed strong correlations between processing conditions, phase evolution, morphology, and electrochemical performance. The synthesized materials were characterized using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM), nano X-ray computed tomography (Nano-CT), Raman spectroscopy, and thermogravimetric analysis (TGA). Electrochemical performance was evaluated through long-term cycling, rate capability testing, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The optimized materials demonstrated significantly improved cycling stability, including BPSi retaining 932 mAh g−1 after 200 cycles, carbon-coated porous Si retaining 831 mAh g−1 after 550 cycles, and carbon-coated nanosheet Si maintaining stable capacity over extended cycling. Overall, this work establishes an integrated design framework that combines structural engineering, interfacial control, and scalable synthesis to enable durable, high-capacity silicon anodes. The findings provide fundamental insights and practical strategies for advancing next-generation Li-ion battery technologies.

SCALABLE DESIGN AND SYNTHESIS OF SILICON ANODES WITH ENGINEERED STRUCTURE AND INTERFACES FOR HIGH-ENERGY LI-ION BATTERIES

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