Crystal Structures and Phase Behavior of the Cyclic\nCarbonates Fluoroethylene Carbonate, Ethylene Carbonate, and Vinylene Carbonate down to 86 K Using Powder Diffraction Data

Understanding the\nbehavior of organic electrolytes of lithium-ion\nbatteries is ubiquitous to help overcome the adverse impact of their\nfreezing in cold conditions on impacting the reversibility and durability\nof lithium-ion batteries. Fundamental studies of the popular, yet\ncorrosive solvent/additive fluoroethylene carbonate (FEC) appear to\nbe few in number outside electrochemical characterization. This powder\ndiffraction study forms what we believe to be the first to specifically\nprobe the nature of its crystalline solid state. The crystal structure\nwas determined ab initio with simulated annealing of powder diffraction\ndata supported by Density Functional Theory calculations. Phase and\nthermal expansion behavior between 90 and 275 K were studied. Comparison\npowder diffraction data were obtained from the related ethylene carbonate\n(EC) and vinylene carbonate (VC). No solid–solid phase transitions\nwere observed in the temperature range studied for any of the samples.\nFEC was found to form a three-dimensional network structure comprising\nhydrogen-bonded dimers as opposed to the more layered nature of the\nEC and VC crystal structures. The weak attractive and repulsive intermolecular\ninteractions in the final crystal structures were examined using the\nNon-Covalent Interaction method and Bader partial charges.