Image courtesy of Stanley Whittingham
Chemical Shift Magnetic Resonance Imaging (MRI) of a lithium battery after charging. The slice of the image at 270 ppm shows newly formed “moss” (irregular porous microstructures) and dendrites (particles with multi-branching tree-like shapes). The build-up of these microstructures between the electrodes could eventually short-circuit the battery.
Scientists have developed magnetic resonance imaging (MRI) methods to non-destructively and quantitatively image lithium (Li) metal microstructures in electrodes and electrolytes in lithium ion batteries. The technique can be used to understand and characterize the electrochemical conditions under which unwanted Li microstructures are formed as well as the effects of different electrolytes and additives.
The ability to non-destructively image the chemical changes that occur inside a battery enables an exploration for designs, materials, and operating conditions that result in improved performance and that that minimize, for example, dangerous Li dendrite formation, leading to higher capacity and higher power Li ion batteries for energy applications.
The most attractive, highest energy density anode material for a lithium (Li) ion battery is lithium metal itself. However, Li metal battery commercialization has been hampered by safety concerns about the formation of extended Li metal microstructures that can create a short circuit between electrodes. Two key questions emerge: (1) In what form is the Li metal deposited - bulk, porous (aka mossy), or dendritic? and (2) How can Li dendrites be prevented? As part of the Northeastern Center for Chemical Energy Storage EFRC, a research team from New York University, Stony Brook University, and Cambridge University has developed a suite of magnetic resonance imaging (MRI) techniques for characterizing deposited lithium inside a working battery cell. Because the radio frequency energy used in MRI has a limited penetration into bulk Li metal but much greater penetration into more porous microstructures, the amount of Li metal microstructure formed during cycling can be quantified by measuring the increase in signal strength. In 2-D and 3-D7LI MRI techniques, bulk magnetic susceptibility has different signals for the dendrites and the Li metal moss that grow on the Li metal anode, revealing both the location and nature of the microstructural lithium under the operating conditions of the battery.
Clare P. Grey
New York University
M. Stanley Whittingham
Director of the Northeastern Center for Chemical Energy Storage (NECCES) EFRC
DOE Office of Science, Office of Basic Energy Sciences, Energy Frontier Research Centers (EFRC) Program; National Science Foundation (A.J., data analysis)
Chandrashekar, S.; Trease, Nicole M.; Chang, Hee Jung; Du, Lin-Shu; Grey, Clare P.; and Jerschow, Alexej “7Li MRI of Li batteries reveals location of microstructural lithium” Nat. Mater., 11, 311-315 (2012). [DOI: 10.1038/nmat3246]
Northeastern Center for Chemical Energy Storage (NECCES) EFRC
Collaborations, Non-DOE Interagency Collaboration