Wide-angle X-ray scattering (WAXS) was used to study the distribution of salt in short-chain disordered block copolymer electrolytes with concentration fluctuations on the length scale of 1 nm. The electrolytes were binary mixtures of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt and a short block copolymer comprising perfluoroether (PFE) segments covalently bonded to ethylene oxide (EO) segments. We develop a method to analyze scattering data from mixtures of block copolymers and salt where salt distribution is not known beforehand, using a minimal number of adjustable parameters. The WAXS peak due to scattering from disordered concentration fluctuations is fit to a random phase approximation (RPA) model that includes a parameter to describe the partitioning of salt between the perfluoropolyether (PFPE)-rich and poly(ethylene oxide) (PEO)-rich concentration fluctuations. This method enables quantification of the salt distribution and the effective Flory-Huggins interaction parameter between polymer segments. We posit that attractive interactions between the TFSI- anion and PFPE (fluorous effect) drive some of the salt into the PFPE-rich fluctuations. On the other hand, the attractive interactions between Li+ and EO segments drive the remaining salt molecules into the PEO-rich fluctuations. We use WAXS to quantify LiTFSI partitioning between the PFE and EO segments in the block copolymer. The segregation between blocks, quantified by an effective Flory-Huggins interaction parameter between polymer segments, decreases with increasing salt concentration, behavior that is atypical for block copolymer electrolytes.