Feel free to download and use the electro-thermal model for the A123 26650 LiFePO4 battery developed by Dr. Lin and colleagues.
Xinfan Lin, Hector E. Perez, Shankar Mohan, Jason B. Siegel, Anna G. Stefanopoulou, Yi Ding and Matthew P. Castanier. “A Lumped-Parameter Electro-thermal Model for Cylindrical Batteries”, Vol. 257, 1-11, Journal of Power Sources, 2014.
Check this cool video showing the principle of neutron imaging for in-situ measurement of lithium ion distribution inside the battery.