Superior Electrochemical Performance of Core-Shell Si@Sioc Particles Synthesized Using Supercritical Carbon Dioxide Fluid for Li-Ion Batteries

Résumé fourni par la source

To overcome the long-existing cycle life problems of Si-based anodes of Li-ion batteries (LIBs), a unique supercritical carbon dioxide (SCCO2) method, characterized by gas-like diffusivity, near-zero surface tension, and excellent mass transfer properties, is developed in this work to create core-shell Si@SiOC composite particles (with a specific capacity of ≈2250 mAh g−1) for high-cyclability LIBs. This is a pioneer work to produce an SiOC compound using SCCO2. The formation mechanism of SiOC is examined using high-resolution transmission electron microscopy and its auxiliary energy-dispersive X-ray line-scan spectroscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy. The conducting SiOC layer makes the Si@SiOC particles connected, benefiting electron and Li+ transport. In addition, the buffering SiOC layer can accommodate the Si volume change during lithiation/delithiation. Of note, the protective SiOC layer provides high corrosion resistance to HF. Our operando X-ray diffraction data indicate that the crystal size and orientation of the lithiated Li15Si4 phase are altered by the presence of SiOC, which promotes phase transition reversibility during cycling. The proposed Si@SiOC||LiNi0.8Co0.1Mn0.1O2 full cell shows a promising energy density of ≈600 Wh kg−1 (based on anode and cathode active materials) with satisfactory cyclability. The SCCO2 synthesis process is eco-friendly, cost-effective, and scalable. The obtained Si@SiOC anode material has great potential for high-energy-density and high-reliability LIB applications.

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