High-power lithium ion batteries have great potential for applications in electric vehicles or even electrical grid stabilization systems. Moreover, adopting plug-in hybrid electric vehicles for commuting in metropolitan areas can reduce CO2 emission by as much as 50%. While many conventional materials engineering techniques, such as carbon coating, doping, and particle size reduction, have been used to improve the performance of battery materials, meeting the grand challenges demands new transformative approaches. This project aims to develop an unconventional approach to use nanoscale 'surface phases' of self-regulating thickness to tailor battery materials to achieve superior properties that are not attainable by using the normal three-dimensional bulk materials or nanoparticles. This project also aims to bridge an important gap in the fundamental interfacial science by extending the well-established low-temperature surface science theories to high-temperature ceramic materials. Integrated research and education activities have impacts on high school, undergraduate, and graduate students, as well as the general public.
TECHNICAL DETAILS: The research objectives of this project are twofold. The first (technological) objective is to develop a new method of using nanoscale 'surface phases' to improve the rate capability of battery materials. Compared with the conventional coatings, these 'surface phases' have several advantages: (a) they form spontaneously upon annealing as the thermodynamic equilibrium configurations; (b) they exhibit a self-selecting or "equilibrium" thickness that is tunable by changing thermodynamic potentials; and (c) surface doping can be introduced to increase the ionic and electronic conductivity, improve the morphological stability during electrochemical cycling, and suppress the formation of the detrimental thick solid-electrolyte interface layers. This new approach is expected to be applicable for engineering a wide variety of oxide based cathode materials (including many emerging materials), as well as some anode materials. The second (scientific) objective is to use battery materials as model systems to investigate a potentially transformative concept of utilizing nanoscale 'surface phases' to achieve properties unattainable through bulk phases, and to advance to the fundamental interfacial science by establishing new theories of high-temperature surface adsorption and disordering in ceramic materials. Broad impact activities include involving high school students in summer research programs; assembling a multidisciplinary undergraduate team to develop free-access online educational materials; and mentoring doctoral students in both cutting-edge energy-related research and outreach activities.
