Electrochemical Energy Storage: Challenges and Opportunities
June 1, 2012
Dr. Ping Liu
Rechargeable batteries have enabled the mobile society and are starting to penetrate electric vehicle and smart grid applications, two technology sectors that are the center pieces of sustainable development. For these applications, long service lives of over ten years are required. In this talk, we first give an overview of the underlying principles that govern battery life, i.e, stable interfaces, minimal structural change, and lack of self-discharge. When these principles are followed, exceptionally long life can be obtained but often at the expense of energy density. On the other hand, the pursuit of high energy density often challenges these principles and leads to fast degradation. As an example, analysis of state of the art lithium ion batteries shows that a combined chemical and mechanical degradation mechanism is responsible for performance decay. Chemical degradation is due to unstable interfaces while mechanical degradation is attributed to material structural changes. We outline several approaches that effectively address life limiting mechanisms in order to extend the life of batteries. In particular, we discuss the potential of nanotechnology in batteries, i.e., how to mitigate mechanical degradation without enhancing chemical degradation.
Dr. Ping Liu is a Senior Research Scientist and Manager of the Energy Technology Department at HRL Laboratories LLC, an industrial research lab jointly owned by GM and Boeing. At HRL, Dr. Liu leads research activities in rechargeable batteries, fuel cells, and hydrogen storage for both owner companies and government agencies including DOE EERE, ARPA-E and DARPA. His research interests include novel battery chemistry and structure, aging mechanism diagnosis, online state estimation and control, and life modeling of rechargeable batteries. Prior to joining HRL in 2003, Dr. Liu was a technical staff member with the National Renewable Energy Laboratories (NREL), where he conducted research in thin film batteries, electrochromics, and optical hydrogen sensors. Dr. Liu has over sixty peer-reviewed publications and over forty issued and pending patent applications. He is a co-inventor of a solid state battery technology that was licensed to form Planar Energy Devices with which he received the 2009 R&D 100 Award. His inventions in fiber optic hydrogen sensors have been commercialized for corrosion detection. Dr. Liu received his PhD in physical chemistry from Fudan University in 1995.