Lignin-derived electrospun carbon fibres as lightweight current collectors for high-performance lithium metal batteries
File(s)
Author(s)
Southern, Samantha
Type
Thesis
Abstract
Zero-excess lithium metal batteries (zero-excess LMBs), in which the anode initially contains no Li and Li metal is plated during the first charge cycle, offer higher energy density and manufacturing advantages over conventional lithium metal batteries, but their practical deployment is limited by short cycle life and safety concerns. In this thesis, electrospun lignin-derived carbon fibres (CFs) are demonstrated as a replacement for conventional Cu foil current collectors, offering sustainability benefits and structural advantages. Lignin contains abundant oxygen functionalities and aromatic networks which, upon carbonisation, generate O-rich turbostratic carbon with microporosity and defect sites. By tuning the carbonisation temperature, the defect density and porosity of the fibres are modulated, directly governing solid electrolyte interphase (SEI) composition, Li nucleation behaviour and plating/stripping reversibility. X-ray photoelectron spectroscopy and titration studies reveal that defect-rich CFs form a stable, inorganic-rich SEI that effectively passivates the surface. Solid-state 7Li nuclear magnetic resonance spectroscopy shows that CFs carbonised at 1000 °C enable the formation of quasi-metallic Li clusters within pores prior to metallic Li plating. These clusters enhance nucleation kinetics, lower the nucleation overpotential, and enable reversible Li plating/stripping. Scanning electron microscopy shows that these optimised CF current collectors promote the formation of compact Li agglomerates (~100 µm), in contrast to the high-surface-area whisker-like deposits formed on Cu. The CF current collectors exhibit a first-cycle Li loss of only 4.8–8.9% relative to the typical Li inventory of commercial LIB cathodes and maintain a coulombic efficiency of 99.0% over 200 cycles. X-ray Raman scattering shows that Li initially plates at the front surface of the fibre mat and redistributes through the electrode during cycling, reducing short-circuit risk. Overall, this work demonstrates that rational control of defect landscapes and pore architecture in sustainable lignin-derived CFs provides a powerful strategy for directing Li nucleation and stabilising zero-excess LMBs.
Version
Open Access
Date Issued
2025-12-22
Date Awarded
2026-05-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Titirici, Magdalena
Au, Heather
Sponsor
The Faraday Institution
Grant Number
FITG041
Publisher Department
Department of Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)