Multifunctional
Sustainable
Materials
Research
Lithium-sulfur batteries
Lithium-sulfur batteries have a number of benefits over traditional lithium-ion technology and have the potential to offer cheaper, lighter-weight batteries that can store more energy.
Li-S batteries replace critical minerals, such as Co and Ni, at the cathode with cheap and abundant elemental sulfur, to reduce environmental, social and cost burdens. Pairing a sulfur cathode with a lithium metal anode could allow huge improvements in the amount of energy stored for the same weight, compared to materials used in standard Li-ion batteries.
However, improved safety, long-term performance and practical energy density remain challenging. In the MSM group, we work on different aspects of the lithium-sulfur battery to improve performance.
Understanding and stabilising lithium deposition in zero-excess lithium-metal batteries
Uneven metal plating and stripping on lithium anodes can lead to rapid inventory loss, capacity fade, and short circuits. We use light-weight carbon fibres with regulated surface chemistry and pore structure as 3D current collectors, to enable stable, homogeneous deposition to improve cycle life and safety.
Developing free-standing electrode supports for sulfur cathodes
A typical lithium-sulfur battery contains many inactive components, which can negatively impact the battery’s practical energy density. Lignin-derived electrospun carbon fibres can act as effective free-standing sulfur cathode supports, allowing us to dispense with inactive components and increase the amount of energy stored for the same weight. We are investigating how fibre properties affect the sulfur conversion reactions and long-term cycling behaviour.
Lithium sulfide cathodes for zero-excess lithium-sulfur batteries
Starting with a fully lithiated cathode could allow us to eliminate all excess lithium from the cell, improving cost, sustainability and safety. We explore different methods of lithium sulfide deposition and formation to overcome the large activation energy barrier when charging the battery.
Porous carbon hosts for lithium-sulfur battery cathodes
Porous carbons are effective hosts for sulfur cathodes, providing voids for effective encapsulation, a conductive network, and functional groups to enable redox reactions. This work explores how key properties of C/S composites from sustainable sources, such as pore structure, surface chemistry, catalytic sites, graphitisation, and loading, collectively influence electrochemical performance.
Functional membranes for stable lithium-sulfur battery performance
Dissolution and uncontrolled diffusion of sulfur species, known as polysulfide shuttling, during battery cycling can cause premature performance fading. We are developing sustainable functional membranes for species-selective diffusion to improve the physical and chemical stability of our batteries.
Structural battery composites
Structural batteries are multifunctional composites that serve simultaneously as mechanical load-bearing components and high-performance energy storage. This means that the rigid structure of a vehicle could also store the energy needed to power it, with no additional weight penalty.
Producing a structural battery based on lithium-sulfur chemistry could therefore allow electrification of difficult-to-decarbonise industries such as aerospace. To produce a structural lithium-sulfur battery, our work focuses on optimising the mechanical properties of our electrodes and developing suitable structural polymer electrolyte systems.
Lignin-derived carbon fibres for high-performance structural batteries
Conventional carbon fibres used for structural applications are usually expensive, derived from fossil fuels, and their materials chemistry is not suitable for lithium-sulfur batteries. Carbon fibres from lignin are cheaper, more sustainable and tuneable, but the main challenge is their poor mechanical properties. This project aims to produce lightweight, strong and stiff carbon fibres from lignin that are also effective for energy storage.
Development of structural lithium-sulfur battery electrolytes
Electrolytes for structural batteries must be capable of both ion conduction and mechanical load transfer. Replacing traditional liquid with solid-polymer electrolytes has multiple benefits including superior mechanical properties and reduced fire risk, but can adversely affect ion conductivity. We are developing structural polymer electrolytes that are mechanically robust and ionically conductive to enable effect multifunctional performance.
Sustainable alternatives for structural applications
Carbon fibre-reinforced composites are increasingly used where high specific strength and stiffness are required, but they are expensive to produce and generally limited to high-end or niche applications. However, their light weight means they hold the potential to systemically reduce carbon emissions from transportation, a key lever in reaching net-zero.
Commercial carbon fibres are usually made from non-renewable precursors and their production involves hazardous solvents and toxic by-products. Producing sustainable lightweight carbon fibres with high strength and stiffness at low cost would represent a significant step towards their wider implementation, as well as open up new avenues for use.
Sustainable electrospun carbon yarns from upcycled waste
We aim to develop a scalable, sustainable alternative to high-value commercial carbon fibres used for structural composites, by electrospinning yarns from waste derivatives such as lignin. Using renewable precursors, green solvents and less energy-intensive processes will decrease the cost and environmental impact of carbon fibre and composite manufacture, allowing wider uptake in many industries (e.g. automotive).
Current grants
Our research is funded by a Royal Society University Research Fellowship, a Royal Society International Exchanges grant, the Faraday Institution LiSTAR project, and a private donation at Imperial.
