Neutron imaging of lithium concentration in battery pouch cells

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 augmented 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].