ChE Texas Distinguished Faculty Lectureship Seminar – “High-Capacity Concentration Gradient Cathodes for Next-generation Lithium Batteries” by Dr. Yang-Kook Sun (Hanyang University)
Host: Dr. C. Buddie Mullins; Texas Distinguished Faculty Lectureship
Lithium ion batteries (LIBs) have the highest gravimetric and volumetric energy densities among the commercialized batteries that can provide electric drives for plug-in hybrid (PHEVs) and fully electric vehicles (EVs). Despite the increasing utilization of the LIBs, the share of electric vehicles in the world’s automotive market has been growing at a slower rate than expected. The cost-to-range ratio can often be identified as one of the primary factors responsible for the slow growth. A driving range of at least 300 miles is typically considered to be the threshold to guarantee the success of future electric vehicles. Although clever cell design and improvements in cell subcomponents can bear potential for volume and weight reduction, major developments in high capacity cathode and anode active materials in particular, for the cathode are essential. Among the existing cathodes for LIBs, Ni-rich layered lithium transition-metal oxides, Li[Ni1-x-yCoxMy]O2 (M = Al (NCA) or M = Mn (NCM), 1-x-y≥0.6) are the most practical candidates for EVs and have been studied extensively in the past two decades because of their high reversible capacity, good rate capability, and relatively low cost. Despite the advantages, increasing the Ni fraction in the NCM cathodes negatively impacts the lifetime and safety of the battery, particularly when higher cut-off voltages and high electrode packing densities are pursued. A number of strategies have been explored to increase the stability of the Ni-enriched NCM cathode material by suppressing the parasitic side reactions with the electrolyte.
Among them, a compositionally graded cathode material in which concentrations of the transition metals continuously varied from the particle center to the surface appears to be the most promising since the graded cathodes have demonstrated remarkable improvements over cathodes with single uniform composition, not only in lifetime and safety, but also in battery power due to the superior Li+ diffusion kinetics. In this presentation, we review the most recent and promising results concerning NCA and NCM cathode materials. In addition, we introduce various compositionally graded cathodes and suggest the cathodes can enable production of batteries that meet the demanding performance and safety requirements of electric vehicles.
Professor Yang-Kook Sun is Head of BK 21+ program at Hanyang University at Seoul in Korea. He received his Ph.D degree in Chemical Engineering (1992) from the Seoul National University, Korea. Professor Sun serves as Chair, Vice-Chair, and advisory member of several leading international conferences. His achievements include the publication of more than 378 peer-reviewed papers in the scientific literature and 224 patents. In 2007 he was awarded the Energy Technology Division Research Award and in 2011 the Battery Division Research Award of the Electrochemical Society. His research interests are the development of new electrode materials (cathode and anode) for lithium-ion batteries, super-capacitors, and next-generation batteries of Na-ion batteries, Li-S batteries, and Li-air batteries.