LIQUID PHASE EXFOLIATION OF GRAPHENE AND GRAPHENE- BASED HETEROSTRUCTURES FOR HIGH-RATE LI-ION BATTERY ANODES
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The surging global energy demand, expected to grow by over 50% by 2050, calls for efficient energy storage solutions, with Lithium-ion Batteries (LIBs) leading the charge due to their high energy density and reliability. However, conventional LIBs rely on graphite-based anodes with limited capacities (~372 mAh/g). Silicon emerges as a promising alternative with a much higher capacity (~3579 mAh/g) and abundance, but it suffers from over 300% volume expansion during lithiation, leading to structural degradation, poor conductivity, and rapid capacity fading. To harness silicon’s high capacity, it is often combined with Graphene(Gr), known for its exceptional electrical, and mechanical properties. In this work, we developed a cost- effective, environmentally friendly method for synthesizing few-layer graphene via shear-assisted exfoliation in a Taylor-Couette Reactor (TCR), converting recycled graphitic precursors into high-quality graphene. Given that ~4 million tonnes of graphite are used annually—with only 29% being recycled—utilizing minimally processed graphitic precursors in TCR can reduce graphene production costs by >40%. After successfully exfoliating graphene, we extended our work to synthesize hexagonal boron nitride (hBN), or "white graphene," and its van der Waals heterostructures with graphene (hBN/Gr) using the TCR, further expanding its usefulness in facile 2D material synthesis. These layered heterostructures leverage the strengths of both materials showcasing tremendous potential in LIBs and beyond. Finally, we fabricated Si/Gr and Si/hBN/Gr hybrid anodes using low-cost recycled silicon to further reduce battery costs. Electrochemical tests revealed Si/Gr anodes made from recycled precursors are on par with those using pristine commercial graphite in terms of cell performance. Furthermore, while Si/Gr anodes show solid performance, they face challenges like layer restacking, leading to capacity fading and high internal resistance. The addition of hBN in Si/hBN/graphene composite anodes effectively addressed these issues by stabilizing the layered structure and enhancing Li-ion transport pathways. This resulted in improved structural integrity, higher ICE, better cycling stability, and increased rate capability—crucial for developing efficient, faster- charging LIBs in the future.