We have studied ion transport in electrolytes created by blending two different polymers and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The polymers covered in this study are poly(ethylene oxide) (PEO), poly(1,3,6-trioxocane) (P(2EO-MO)), and poly(1,3-dioxolane) (P(EO-MO)). Ion transport is quantified by the product κρ+which is defined as the efficacy of the electrolytes, where κ is conductivity and ρ+is the current fraction determined by the Bruce-Vincent method. Polymer blends can be either one-phase or macrophase-separated. We used small-angle neutron scattering (SANS) to distinguish between these two possibilities. The random phase approximation (RPA) was used to interpret SANS data from one-phase blends. The effect of added salt on polymer blend thermodynamics is quantified by an effective Flory-Huggins interaction parameter. All polymer blends were one-phase in the absence of salt. Adding salt in small concentrations results in macrophase separation in all cases. One-phase systems were observed in the PEO/P(EO-MO)/LiTFSI blends at high salt concentrations. In most of the polymer blend electrolytes, the measured κρ+was either lower than or comparable to that of the homopolymer electrolytes. An exception to this was one-phase PEO/P(EO-MO)/LiTFSI blends electrolytes at high salt concentrations.

This study shows that it is possible to obtain homogeneous mixtures of two chemically distinct polymers with a lithium salt for electrolytic applications. This approach is motivated by the success of using mixtures of organic solvents in modern lithium-ion batteries. The properties of mixtures of a polyether, poly(ethylene oxide) (PEO), a poly(ether-acetal), poly(1,3,6-trioxocane) (P(2EO-MO)), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt were studied by small-angle neutron scattering (SANS) and electrochemical characterization in symmetric cells. The SANS data are used to determine the miscibility window and quantify the effect of added salt on the thermodynamic interactions between the polymers. In the absence of salt, PEO/P(2EO-MO) blends are homogeneous and characterized by attractive interactions, i.e., a negative Flory-Huggins interaction parameter, χ. The addition of small amounts of salt results in a positive effective Flory-Huggins interaction parameter, χeff, and macrophase separation. Surprisingly, miscible blends and negative χeff parameters are obtained when the salt concentration is increased beyond a critical value. The electrochemical properties of PEO/P(2EO-MO)/LiTFSI blends at a given salt concentration were close to those obtained in PEO/LiTFSI electrolytes at the same salt concentration. This suggests that in the presence of PEO the electrochemical properties exhibited by P(2EO-MO) chains are similar to those of PEO chains. This work opens the door to a new direction for creating new and improved polymer electrolytes either by combining existing polymers and salt or by synthesizing new polymers with the specific aim of including them in miscible polymer blend electrolytes.

Through an expansive international effort that involved data collection on 12 small-angle X-ray scattering (SAXS) and four small-angle neutron scattering (SANS) instruments, 171 SAXS and 76 SANS measurements for five proteins (ribonuclease A, lysozyme, xylanase, urate oxidase and xylose isomerase) were acquired. From these data, the solvent-subtracted protein scattering profiles were shown to be reproducible, with the caveat that an additive constant adjustment was required to account for small errors in solvent subtraction. Further, the major features of the obtained consensus SAXS data over the q measurement range 0-1 Å^-1 are consistent with theoretical prediction. The inherently lower statistical precision for SANS limited the reliably measured q-range to <0.5 Å^-1, but within the limits of experimental uncertainties the major features of the consensus SANS data were also consistent with prediction for all five proteins measured in H₂O and in D₂O. Thus, a foundation set of consensus SAS profiles has been obtained for benchmarking scattering-profile prediction from atomic coordinates. Additionally, two sets of SAXS data measured at different facilities to q > 2.2 Å^-1 showed good mutual agreement, affirming that this region has interpretable features for structural modelling. SAS measurements with inline size-exclusion chromatography (SEC) proved to be generally superior for eliminating sample heterogeneity, but with unavoidable sample dilution during column elution, while batch SAS data collected at higher concentrations and for longer times provided superior statistical precision. Careful merging of data measured using inline SEC and batch modes, or low- and high-concentration data from batch measurements, was successful in eliminating small amounts of aggregate or interparticle interference from the scattering while providing improved statistical precision overall for the benchmarking data set.