Research areas within Structural Chemistry
Currently, most state-of-the-art battery electrodes are processed using organic solvents such as the highly toxic N-methyl-2-pyrrolidone (NMP), which poses health hazards and environmental concerns. This is a direct consequence of using electrode binders, such as polyvinylidene fluoride (PVDF), which are not soluble in water. Some examples of binders that are soluble or insoluble in water are shown in the figure below. This project investigates a promising new family of binders, thought to offer excellent structural stability, high water solubility, high lithium-ion conductivity, facile extraction from natural resources and are environmentally-friendly. Extensive electrochemical testing and advanced characterisation techniques will result in a detailed understanding of how the binders can be used to further the performance of next-generation battery electrodes.
Ion-conducting polymers may be used in place of traditional liquid electrolytes to make solid-state batteries. The solid-state construct effectively eliminates the safety hazard posed by the flammable organic solvents used in liquid-electrolyte cells and offers better high-temperature stability. The biggest challenge with polymer electrolytes is to improve the ionic conductivity of the materials while retaining a high mechanical stability.New host materialsWe work with developing new materials based on ion coordination by carbonyl groups, such as polycarbonates, polyesters and polyethers, to use as host materials in polymer electrolytes. The carbonyl groups offer weaker coordination that, e.g., the commonly utilized oxyethylene coordinating motif, leading to faster Li+movement in the material.
The current commercial Li-ion battery technology is largely reliant on the utilization of graphite as an intercalation material to store Li ions on the negative (anode) side of the battery. While this material has enabled a large-scale and wide-spread implementation of Li-ion batteries, its storage capacity is limited to 372 mAh/g. To reach higher energy densities, new materials with higher capacity for lithium storage are needed.
According to the two-volume "Modern Electrochemistry" written by Bockris and Reddy, there are two kinds of electrochemistry. The first one is "The physical chemistry of ionically conducting solutions" and the second one is "The physical chemistry of electrically charged interfaces". We are working on the fundamental sides of these problems in energy storage/conversion with a focus on method developments.
We work broadly with computational techniques such as ab initio calculations, Density Functional Theory, Molecular Dynamics simulations and Finite Element Methods to study relevant questions for molecules, materials, interfaces and cell chemistry in batteries. We also link these methods in a multi-scale fashion, and implement machine-learning tools for prediction of behavior of different chemistries in batteries. Computational simulations helps us to study stability at the electrode/electrolyte interface, ion transport, the structural evolution of electrodes during cycling, current distribution in the battery cell, and several other issues.
The rechargeable lithium-sulfur (Li-S) battery is one of the most promising "post-Li-ion" energy storage systems. The battery has the potential for very high gravimetric energy density - that is, a Li-S battery could store two to three times as much energy for a given weight compared to current Li-ion batteries. Other advantages of the system include relatively good safety, the potential for operation at very low temperatures, and lower cost: as a byproduct of the oil industry, sulfur is very inexpensive and highly abundant. However, short cycle life and high self-discharge remain barriers to wider commercialization, and very complex chemistry makes this system challenging to study.
Quasicrystals (QCs) are intermetallic compounds that possess long-range aperiodic order with diffraction symmetries forbidden to conventional crystals. Their discovery in 1982 in a rapidly solidified Al-Mn alloy was highly controversial since long-range order and three-dimensional (3D) periodicity were thought to be synonymous. Although QCs can be described mathematically as periodic crystals in a virtual space of higher dimensions, envisioning long-range order beyond 3D periodicity posed a great perceptual challenge. A true milestone represented the atomic structure solution of the icosahedral YbCd5.7 quasicrystal in 2007, which for the first time completely revealed the extreme structural complexity of QCs.