Structure-rate performance relationship in Si nanoparticles-carbon nanofiber composite as flexible anode for lithium-ion batteries

Abstract

A flexible silicon-carbon nanofibre composite is reported as an anode material for lithium-ion batteries. Self-standing, binder-free and flexible anodes composed of Si nanoparticles embedded inside carbon nanofibers of different fibre diameter are fabricated via electrospinning. The silicon nanoparticles are effectively protected from direct exposure to the electrolyte by the carbon fibre encapsulation, leading to vastly improved capacity retention during galvanostatic half-cell cycling. Cycling results also showed that an electrode with 230 nm fibre diameter has enhanced cyclability and rate capability when compared to one with 620 nm diameter. SEM (scanning electron microscopy) and EIS (electrochemical impedance spectroscopy) post-cycling investigations of the electrodes reveals an appropriate structural stability and lower impedance during cycling for the electrode with thinner carbon fibres. This behaviour is associated with the low linear density of the Si nanoparticles along the thin carbon nanofibers, which prevents the fracture of the carbon fibres at the sites of Si clusters.