The new CEI-XANES user facility allows one to obtain synchrotron-quality x-ray absorption near edge structure (XANES) in the University setting, without the inconveniences, expensive travel, and infrequent access of synchrotron beamlines. As this facility comes online, it will be important to gain deep expertise in the interpretation of XANES spectra, and especially of systematic changes upon electrochemical cycling. In my research, I will investigate two complementary aspects of this problem. First, from the theoretical perspective, I will use both my own expertise and collaboration with local and off-site theory teams to compare and contrast experiment for pouch cells and relevant reference phases with all contemporary theoretical methods used for XANES in batteries. Second, from a more pragmatic vantage, I will compare and contrast different methods for numerical inference of phase mixtures using XANES, including especially singular value decomposition and Bayesian methods.