title: Direct Mapping of Charge Distribution during Lithiation of Ge Nanowires Using Off-Axis Electron Holography.
abstract: The successful operation of rechargeable batteries relies on reliable insertion/extraction of ions into/from the electrodes. The battery performance and the response of the electrodes to such ion insertion and extraction are directly related to the spatial distribution of the charge and its dynamic evolution. However, it remains unclear how charge is distributed in the electrodes during normal battery operation. In this work, we have used off-axis electron holography to measure charge distribution during lithium ion insertion into a Ge nanowire (NW) under dynamic operating conditions. We discovered that the surface region of the Ge core is negatively charged during the core-shell lithiation of the Ge NW, which is counterbalanced by positive charge on the inner surface of the lithiated LixGe shell. The remainder of the lithiated LixGe shell is free from net charge, consistent with its metallic characteristics. The present work provides a vivid picture of charge distribution and dynamic evolution during Ge NW lithiation and should form the basis for tackling the response of these and related materials under real electrochemical conditions.
authors.affiliation: Department of Physics, Arizona State University , Tempe, Arizona 85287, United States.
authors.forename: Zhaofeng
authors.initials: Z
authors.lastname: Gan
authors.affiliation: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
authors.forename: Meng
authors.initials: M
authors.lastname: Gu
authors.affiliation: Device Research Laboratory, Department of Electrical Engineering, University of California , Los Angeles, California 90095, United States.
authors.forename: Jianshi
authors.initials: J
authors.lastname: Tang
authors.affiliation: Device Research Laboratory, Department of Electrical Engineering, University of California , Los Angeles, California 90095, United States.|Department of Materials Science and Engineering, National Taiwan University of Science and Technology , Taipei City, Taiwan 10607, Republic of China.
authors.forename: Chiu-Yen
authors.initials: CY
authors.lastname: Wang
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Yang
authors.initials: Y
authors.lastname: He
authors.affiliation: Device Research Laboratory, Department of Electrical Engineering, University of California , Los Angeles, California 90095, United States.
authors.forename: Kang L
authors.initials: KL
authors.lastname: Wang
authors.affiliation: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
authors.forename: Chongmin
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of Physics, Arizona State University , Tempe, Arizona 85287, United States.
authors.forename: David J
authors.initials: DJ
authors.lastname: Smith
authors.affiliation: Department of Physics, Arizona State University , Tempe, Arizona 85287, United States.
authors.forename: Martha R
authors.initials: MR
authors.lastname: McCartney
keywords: Lithium ion battery; charge distribution; electron holography; in situ TEM