Experimental and analytical investigation of the potential of carbon fibres for use in multifunctional batteries

Carbon fibres have been extensively investigated for their promising potential as anodes or current collectors in next-generation integrated batteries. However, the exact reasons for the distinct lithium-ion battery (LIB) performance of different carbon fibres remain largely unknown. In this work, we explored the morphology-/microstructure-mediated lithiation mechanism in carbon fibre anodes and found that a pitch-based carbon fibre with the highest crystal-ordering degree exhibited higher cycling stability but lower reversible capacity and rate capability than a polyacrylonitrile-based carbon fibre (PAN) with the lowest crystal-ordering degree; a modified PAN carbon fibre with a slightly higher crystal ordering degree than PAN showed the highest cycling stability and rate capability. Such carbon-fibre-dependent lithiation is attributable to the distinct lithiation kinetics intrinsic to carbon fibres with different microstructures. This study reveals the morphology-/microstructure-dependent lithiation mechanism of carbon fibres and provides important insights into the interplay between their lithiation kinetics, microstructure and lithium storage performance. Carbon fibres’ adequate crystal degree, small diameter and high structural integrity collectively account for their superior electrochemical properties. This provides guidelines for the design of carbon fibre electrodes and other carbonaceous electrodes for use in next-generation LIBs.