Electrolyte design is critical for enabling next-generation batteries with higher energy densities. Hydrofluoroether (HFE) solvents have drawn a lot of attention as the electrolytes based on HFEs showed great promise to deliver highly desired properties, including high oxidative stability, ionic conductivity, as well as enhanced lithium metal compatibility. However, the structure-dynamics-properties relationships and design principles for high-performance HFE solvents are still poorly understood. Herein, we proposed four novel asymmetric HFE designs by systematically varying polyether and fluorocarbon structural building blocks. By leveraging molecular dynamics (MD) modeling to analyze the solvation structures and predict the properties of the corresponding 1 M lithium bis(fluorosulfonyl)imide (LiTFSI) solutions, we downselected the most promising candidate based on high conductivity, solvation species distribution, and oxidative stability for extensive electrochemical characterizations. The formulated electrolyte demonstrated properties consistent with the predictions from the simulations and showed muchimproved capacity retention as well as Coulombic efficiency compared to the baseline electrolytes when cycled in lithium metal cells. This work exemplifies the construction of candidate electrolytes from building block functional moieties to engineer fundamental solvation structures for desired electrolyte properties and guide the discovery and rational design of new solvent materials.

Solution-grown films of CsPbBr nanocrystals imbedded in Cs PbBr are incorporated as the recombination layer in light-emitting diode (LED) structures. The kinetics at high carrier density of pure (extended) CsPbBr and the nanoinclusion composite are measured and analyzed, indicating second-order kinetics in extended and mainly first-order kinetics in the confined CsPbBr , respectively. Analysis of absorption strength of this all-perovskite, all-inorganic imbedded nanocrystal composite relative to pure CsPbBr indicates enhanced oscillator strength consistent with earlier published attribution of the sub-nanosecond exciton radiative lifetime in nanoprecipitates of CsPbBr in melt-grown CsBr host crystals and CsPbBr evaporated films.

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In contrast to its significance for battery performance, many aspects of the cathode-electrolyte interphase (CEI) remain elusive to the battery community. With cryogenic electron microscopy and spectroscopy, we find that there does not exist an intimate coating layer as a CEI in commercial carbonate-based electrolyte. However, upon brief external electrical shorting, a stable, conformal CEI can form in situ to help improve cycling stability.

As a promising candidate for efficient, scalable, and inexpensive solar cells, hybrid organic-inorganic halide perovskites have attracted tremendous research attention. However, their structural degradation during environmental exposure (e.g., UV light, moisture), which limits the commercialization of hybrid perovskites, is poorly understood. Using cryoelectron microscopy, we stabilize these electron beam-sensitive materials for atomic-scale observation and reveal the nanoscale morphology and structure by freezing these materials during the degradation (e.g., UV illumination, moisture exposure) process.