Scalable and controllable fabrication of CNTs improved yolk-shelled Si anodes with advanced in operando mechanical quantification

Abstract

Yolk-shelled silicon/carbon materials (YS-Si/C) are the most promising anode candidates to further improve the energy density of commercial lithium-ion batteries. Yet, limited conductive promotion and low tap density resulting from hollow spaces, and complex fabrication processes caused by employing various templating methods, are still critical issues for practical applications of YS-Si/C. In this work, a suite of YS-Si/C anode materials with confined Si-yolks by the C-shell without and with carbon nanotubes (each confines a Co3O4 nanoparticle on its tip) on the outer, inner and both sides of the C-shell were facilely and controllably synthesised. The best YS-Si/C anode with carbon nanotubes on both sides of the C-shell can achieve an excellent reversible capacity of 220 mAh g-1 under 40.0 A g-1 with 100% reversible capacity retention after 1200 cycles. Importantly, an electrochemical transmission electron microscope measurement system was assembled and applied for the concurrent in operando quantification of the exerted mechanical force and real-time structural responses of YS-Si/C during lithiation/delithiation and Li dendrite formation/dissolution processes, which can be used to gain new insights into the phenomenological structural changes, providing valuable guidance for the rational structural design of high-performance electrode materials.