Neutron Imaging of Lithium Concentration in Battery Pouch Cells

Abstract — This paper shows how the principle of neutron radiography can be used to quantify the critical physical state of lithium concentration across battery electrodes at steady-state conditions (after a long relaxation time or small load) as a first step in this important effort to measure in-situ battery physical states and validate electrochemical battery models. A model of the expected loss in beam intensity after passing through the different layers of a battery pouch cell is constructed based on the material densities and dimensions. This model is aug-mented with simulation of the neutron transmission behavior, including optical effects due to the geometric unsharpness and the detector response. The resulting model provides the basis for a comprehensive simulation of the in-situ metrology of lithium concentration in Li-ion batteries, and comparison with experimental results. This work was also presented as a poster at the 27th Annual Army Science Conference [1]. I