Physics Colloquium: Penghao Xiao
Penghao Xiao of the Quantum Simulations Group at Lawrence Livermore National Laboratory will be the featured speaker at an upcoming Department of Physics and Astronomy colloquium. His talk is titled, "Atomistic simulation of kinetics in battery materials."
Kinetics plays an important role in both performance and durability of functional materials. For rechargeable batteries specifically, charge/discharge requires fast kinetics to meet application needs, and meanwhile side reactions have to be slow for safety and durability. To achieve the faster-charging and longer-lasting goal, it is essential to understand the related kinetic processes on the atomistic level.
In this talk, Xiao will discuss rate-limiting steps in cathode materials by combining density functional theory and transition state theory and demonstrate how these atomistic pictures help accelerate Li transport and suppress degradation. The first part will be on Li transport in LiFePO4. Two rate-limiting steps are identified for extracting Li from LiFePO4: one is the Li-poor phase nucleation in the bulk and the other is Li passing through the particle surface. Surface sulfur deposition is proposed and confirmed as a new approach to improve the rate capability. The second part will be on degradation in layered oxides. One degradation channel is the oxygen loss at the highly charged state. This process starts at particle surfaces, and thus can be kinetically hindered by stabilizing surface oxygen. Our computational results show that forming SO4 groups on oxide surfaces alleviates oxygen loss and electrolyte oxidation. Borrowing the same sulfur deposition procedure from the first part, we confirm experimentally that surface SO4 improves the cyclability of a Li-rich layered oxide. The above understandings on Li transport and degradation kinetics could help rational design of better rechargeable batteries.
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Department of Physics and Astronomy