Freestanding carbon fiber-confined yolk-shelled silicon-based anode for promoted lithium storage applications

Abstract

A flexible carbon fiber-confined yolk-shelled silicon-based composite is reported as an anode material for lithium storage applications. Silicon nanoparticles (Si NPs) are confined by the N-doped hollow carbon cages (Si-NHC) and these uniform dispersed yolk-shell-structured Si-NHC units were encapsulated by the carbon fibers within an interconnected three-dimensional (3D) framework (Si-NHC@CNFs). For the encapsulated yolk-shelled Si-NHC, the void space between the inner Si NPs and outer NHC can accommodate the structural changes of Si NPs during charging/discharging processes, leading to effectively improved structural stability and cycling life. More importantly, all the Si-NHC units were bridged together through a conductive CNFs “highway” to enhance the overall conductivity and tap density further. As observed, Si-NHC@CNFs exhibited an initial discharge capacity of 1364.1 mAh·g−1 at 1000 mA·g−1 and 678.9 mAh·g−1 at 2000 mA·g−1. Furthermore, the reversible capacity was well maintained at 752.2 mAh·g−1 at 500 mA·g−1 after 6000 ultra-long cycles.Graphical abstract