Annihilating the Formation of Silicon Carbide: Molten Salt Electrolysis of Carbon–Silica Composite to Prepare the Carbon–Silicon Hybrid for Lithium-Ion Battery Anode

[摘要] Silicon (Si) and carbon (C) composites hold the promise for replacing the commercial graphite anode, thus increasing the energy density of lithium-ion batteries (LIBs). To mitigate the formation of SiC, this paper reports a molten salt electrolysis approach to prepare C-Si composite by the electrolysis of C-SiO 2 composites. Unlike the conventional way of making a C coating on Si, C-SiO 2 composites were prepared by pyrolyzing the low-cost sucrose and silica. The electrochemical deoxidation of the C-SiO 2 composites not only produces nanostructured Si inside the C matrix but also introduces voids between the C and Si owing to the volume shrinkage from converting SiO 2 to Si. More importantly, the use of Mg ion-containing molten salts precludes the generation of SiC, and the electrolytic Si@C composite anode delivers a capacity of about 1500 mAh g −1 after 100 cycles at a current density of 500 mA g −1 . Further, the Si@C|| LiNi 0.6 Co 0.2 Mn 0.2 O 2 full cell delivers a high energy density of 608 Wh kg −1 . Overall, the molten salt approach provides a one-step electrochemical way to convert oxides@C to metals@C functional materials.

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