Next-generation battery technologies have the potential to deliver much higher energy densities at lower cost than today's commercial batteries. As a contributor to the BMR and JCESR programs, the Srinivasan group couples continuum-scale simulation with experimental work in order to provide insight into the operation of novel lithium-ion, lithium-sulfur, and magnesium-ion systems.
Our group works to construct mathematical models of these systems in order to assist our coworkers in material development and battery prototyping groups. These models will be used to determine the ways in which improvements in materials can yield the greatest increases in energy density, as well as to understand the processes that decrease battery performance.
Our experimental work involves probing the thermodynamic properties, transport characteristics, and chemical kinetics of all three systems and their components: electrodes, electrolytes, and single-ion conductors. Results are incorporated into our simulations to improve their predictive capability.
Lithium-ion batteries offer the highest energy densities among the rechargeable battery technologies that are widely commercially available. Even higher energy densities may be achievable with the use of next-generation lithium-ion battery components, although widespread use of these proposed replacements frequently involves additional challenges. For example, silicon has been proposed as a high-capacity replacement for the graphite particles typically used in lithium-ion battery anodes. However, this high capacity for inserted lithium comes at the risk of mechanical damage to electrodes during battery operation, resulting in poor battery longevity. Our efforts in this area have included simulation of mechanical stress in electrode models, as well as materials testing of battery components, and are meant to guide design decisions in the construction of silicon-based electrodes.
Our current work on lithium-sulfur batteries is focused on using experiment and modeling in order to identify the causes of capacity limitation and capacity fade.
The two valence electrons of a magnesium atom help to make the magnesium-ion system a strong candidate for the next generation of high-capacity batteries. The volumetric capacity of a magnesium metal anode is even higher than that of lithium metal, and magnesium-ion battery cathodes may likewise offer a similar increase in capacity over those of lithium-ion batteries. However, limited by the difficulty of finding a suitable cathode material and electrolyte, the current baseline magnesium-ion battery exhibits low capacity and low voltage. Our present efforts in this area are focused on determining the most significant bottleneck in the performance of these systems.
Figures (from top): Stress in electrode particle with inserted lithium and attached binder; Porous electrode microstruture; Scanning electron microscope image of porous electrode.