Title: The Generation of Stress and Fracture in the Storage Particles of Lithium-Ion Batteries
Models are developed for the transport of Li ions in the electrolyte of lithium ion batteries, their diffusion through storage electrode particles, and their kinetics through the surface of the particles between the electrolyte and the particles. As a consequence of the Li ion intercalating in the storage particles, their lattices swell, leading to elastic stress when the concentration of Li ions in the particles is not uniform. The models of transport are based on standard concepts for multi-component diffusion in liquids and solids, but are not restricted to dilute solutions, or to small changes in the concentration of the diffusing species. In addition, phase changes are permitted during mass transport as the concentration of lithium varies from the almost depleted state of the storage particle to one where the material is saturated with its ions. The elastic swelling and shrinkage may involve very large dilatations, which can be allowed for in the formulation of the model. Thus, the models can be suitable for storage particle, where the amount of Li can vary by large amounts depending on the state of charge, for staging as observed in the storage process in graphite, for the enormous swelling that takes place when silicon is used for storage, and for electrolytes in which the concentration of Li ions is high. The model is used to compute the processes of charging and discharging the battery to assess the parameters that influence the development of stress in the storage particles, and to deduce the likelihood of fracture of the storage particle material. Phase-field methods are also utilized to predict the process of cracking in the storage particles. The objective is to assess designs of porous electrode microstructures that permit rapid charging and discharging, but obviate the likelihood of fracture and other mechanical damage that limit the performance and reliability of the battery.
Robert M. McMeeking is Tony Evans Professor of Structural Materials and Professor of Mechanical Engineering at the University of California, Santa Barbara, Sixth Century Professor of Engineering Materials at the University of Aberdeen, Scotland (part time) and is an External Member of the Leibniz Institute for New Materials, Saarbruecken, Germany. He earned a B.Sc. (with 1st Class Honours) at the University of Glasgow, Scotland in 1972, and in 1976 he completed his Ph.D. in solid mechanics at Brown University under the supervision of Professor James R. Rice. He spent 2 years at Stanford University as Acting Assistant Professor, and then was appointed Assistant Professor, and subsequently Associate Professor, at the University of Illinois at Urbana-Champaign, in the Theoretical and Applied Mechanics Department. McMeeking moved to the University of California, Santa Barbara (UCSB) in 1985 as Professor of Materials and of Mechanical Engineering. He was Chair of the Department of Mechanical Engineering 1992-1995 and again during 1999-2003. He has published over 250 scientific papers on such subjects as plasticity, fracture mechanics, computational methods, glaciology, tough ceramics, composite materials, materials processing, powder consolidation and sintering, ferroelectrics, microstructural evolution, nanotribology, actuating structures, blast and fragment protection of structures, fluid structure interactions arising from underwater blast waves, the mechanics of the cell and its cytoskeleton, lithium-ion batteries and fuel-cells. In 1998 he was advanced to Fellow grade in the American Society of Mechanical Engineers and in 2002 was recognized by the Institute for Scientific Information as a Highly Cited Researcher in the fields of Materials Science and Engineering. McMeeking was elected to the U.S. National Academy of Engineering in 2005, and held a Humboldt Award for Senior Scientists in 2006 and again in 2013. He was given the Brown Engineering Alumni Medal by Brown University in 2007, and elected Fellow of the U.K. Royal Academy of Engineering in 2012. In 2014 he was also elected Fellow of the Royal Society of Edinburgh and received both the 2014 William Prager Medal of the Society of Engineering Science and the 2014 Timoshenko Medal of the American Society of Mechanical Engineers. McMeeking was Editor of the Journal of Applied Mechanics for the term 2002-2012.