Shielding Si Armed with CoSi2 Nanoplates and Dual-Carbon Shells: 3D Porous Microspheres as High-Performance Anodes for Li-Ion Batteries

Abstract

In this study, a novel multi-core-dual-shell strategy is employed to synthesize 3D porous microspheres. These microspheres consist of Si armed with CoSi₂ nanoplates multi-cores encapsulated within dual protective shells of metallic-Co nanocrystals embedded nitrogen-doped graphitic carbon (NGC) and polydopamine-derived carbon (PDA-C), denoted as Si@CoSi₂-Co/NGC@PDA-C, through a multistep synthesis process involving facile spray pyrolysis and post-heat-treatment. The Si as an active material is surrounded by an inactive buffer material of CoSi₂ with intrinsic low bulk resistivity and high chemical stability, enhancing the electrical interconnectivity and mechanical integrity of the nanostructure. The metallic-Co embedded porous NGC shell facilitates rapid electron transfer by providing primary transport pathways due to its high conductivity, while improving structural robustness by partially restraining the volume expansion of Si. Finally, an additional PDA-derived C protective shell provides secondary transport pathways while mitigating volume expansion, preventing complete detachment from the current collector or pulverization. Correspondingly, the Si@CoSi₂-Co/NGC@PDA-C anode exhibits considerable rate capability (up to 10 A g^-1) and remarkable cycling stability (88% capacity retention after 600 cycles; average capacity loss of 0.02% per cycle at 1.0 A g^-1). Moreover, full-cells paired with a Li(Ni_0.8Co_0.1Mn_0.1)O₂ cathode are evaluated to confirm the practical viability of the nanostructures.

Keywords: full‐cell; lithium‐ion batteries; metal silicide; nitrogen‐doped graphitic carbon; polydopamine‐derived carbon shell; silicon anodes.