Rechargeable Li-ion batteries have a desirable combination of high energy and power density, making them prime candidates for powering portable electronics and electric vehicles. However, the performance of Li-ion batteries eventually decays with charging and discharging the battery due to chemo-mechanical instabilities in the battery electrodes. Two major factors for capacity fade are resistive surface layer formations and particle fracturing. The interaction between electrode and electrolyte species, and the chemical instability of organic electrolyte components under electrical field may lead to the formation of resistive surface layers on the electrodes, which diminish battery kinetics. Insertion and removal of Li ions into electrodes cause large volumetric changes in the electrode. In the constrained geometry of the battery packing, these volumetric changes inevitable generates stress formation, which eventually leads to particle fracturing and capacity loss. Our research group investigates the governing forces responsible for the formation of resistive surface layers and stress generation in the electrodes.
The ever-growing energy demand associated with the increasing human population, environmental concerns and technological developments put pressure on modern society to harvest electricity from renewable sources. Due to their intermittent nature, adoption of renewable energy depends on further developments in energy storage technology. Rechargeable Na-ion and K-ion batteries have attracted attention as “beyond Li-ion batteries” in search of cost-effective batteries. Although Li, Na and K belong to same alkali metal group with single charge in their cation form, reactivity and size of Na and K ions are intrinsically different than Li ions. Therefore, physical and electrochemical behavior of the electrode materials in response to Na-ion and K-ion insertion is expected to be fundamentally different than Li-ions. Our research group investigates the physical behavior of cathode materials in response to sodium and potassium chemistry.
Solid electrolytes have potential to dramatically improve battery performance for more demanding applications by eliminating problems associated with the flammable liquid electrolytes. However, the incorporation of solid electrolytes in Li-ion batteries is a challenging task due to large interfacial impedance, chemo-mechanical instabilities, lithium dendrites and their low ionic conductivity that limits charging rates. Due to the brittle nature of solid-electrolytes, these instabilities may initiate cracking in the electrode as well as in the electrolytes. The lack of insight into chemo-mechanical instabilities and interfacial resistance prevents further developments in solid electrolytes. Our research group focuses on understanding the chemo-mechanical instabilities in the electrode-solid electrolyte interface. Currently, we are working on developing a novel method to quantitively analyze electrochemical strains in the interface.
Li-Oxygen batteries have received much attention as a candidate for electric vehicle batteries, due to their high theoretical energy density and low cost. However, despite profound efforts over a decade on Li-Oxygen batteries, it is still far from realization due to its low round-trip efficiency, low power density and poor cycle life. Poor performance of these batteries originates from the interfacial instabilities associated with sluggish kinetics of the oxygen reduction/evolution reactions and the insulating nature of the reduced oxygen species on the cathode surface. Our research group investigates the surface reaction steps that dictate the performance of cathode electrodes by utilizing in situ stress measurements.
Oil and natural gas resources still play an important role in fulfilling today’s energy consumption needs. Pipelines are the most efficient and economical ways to transport these products to marketplaces. However, gas pipeline failures pose significant safety threats and will be of increasing concern due to aging infrastructure and expense of new construction. Stress Corrosion Cracking (SCC) from the external surface of a pipeline is one of the primary degradation modes in oil and gas pipelines. Our main purpose is to investigate the electrochemical driving force for stress generation and plasticity during SCC and develop valuable early indication of SCC susceptibility prior to the catastrophic failure of the material.