Single-ion conducting (SIC) polymer electrolytes with a high Li transference number (t Li + ) have shown the capability to enable enhanced battery performance and safety by avoiding liquid−electrolyte leakage and suppressing Li dendrite formation. However, issues of insufficient ionic conductivity, low electrochemical stability, and poor polymer/electrode interfacial contact have greatly hindered their commercial use. Here, a Li-containing boroncentered fluorinated SIC polymer gel electrolyte (LiBFSIE) was rationally designed to achieve a high t Li + and high electrochemical stability. Owing to the low dissociation energy of the boroncentered anion and Li + , the as-prepared LiBFSIE exhibited an ionic conductivity of 2 × 10 −4 S/ cm at 35 °C, which is exclusively contributed by Li ions owing to a high t Li + of 0.93. Both simulation and experimental approaches were applied to investigate the ion diffusion and concentration gradient in the LiBFSIE and non-cross-linked dual-ion systems. Typical rectangular Li stripping/plating voltage profiles demonstrated the uniform Li deposition assisted by LiBFSIE. The interfacial contact and electrolyte infiltration were further optimized with an in situ UV−vis-initiated polymerization method together with the electrode materials. By virtue of the high electrochemical stability of LiBFSIE, the cells achieved a promising average Coulombic efficiency of 99.95% over 200 cycles, which is higher than that of liquid−electrolyte-based cells. No obvious capacity fading was observed, indicating the long-term stability of LiBFSIE for lithium metal batteries.

Self-assembly of thiol-terminated polystyrene-tethered Au nanoparticles in microphase-separated diblock copolymers composed of poly(styrene-b-2vinylpyridine) (PS-PVP) as a function of particle concentration and composition of block copolymers was investigated using anomalous small-angle X-ray scattering (ASAXS) and transmission electron microscopy (TEM). Results reveal that the self-assembly of nanoparticles in the PS domain causes swelling and increases the interfacial curvature that, in turn, induces order-order transitions. At intermediate loading, the presence of nanoparticles amplifies the local compositional fluctuations, hence the roughness at the PS and PVP interface, which creates conditions to induce disorder in the polymer morphology. The system thus undergoes an order-disorder transition. At high particle loading, packing constraints prevent all particles from assembling in the PS domain, and the excess nanoparticles undergo macrophase separation. The present systematic study augments experimental data to the scarce literature on the phase behavior of bulk nanocomposites. We present a generalized phase map for the bulk composites as a function of effective volume fraction of PS (F PS ) for a given nanoparticle size. We believe that the results from this study will enable comparison of the phase maps from various studies and will serve to validate the simulation studies of inorganic particle/ block copolymer composites.

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We demonstrate the versatility of anomalous small-angle X-ray scattering (ASAXS) to investigate the morphology of bulk multicomponent composites comprising poly(stryrene-b-2-vinylpyridine) (PS-PVP) and Au nanoparticles. Contrast variation near the L 3 absorption edge of Au enables the separation of the partial scattering functions of the polymer and nanoparticle phases. Theoretical and experimental methodologies developed for our ASAXS analysis of the composites will be useful for the investigation of other such multicomponent systems with heavy elements. This study shows that at 8.8% Au loading the Au nanoparticles remain well dispersed in the lamellar polymer matrix, while at 27.0% Au loading the polymer morphology transforms to a hexagonal packed cylinder phase due to the change in the curvature caused by the higher concentration of the dispersed nanoparticles in the PS domain. In the case of 27.0% Au nanocomposite we also observe strong concentration fluctuations of nanoparticles in the polymer phase, with a hierarchical structure containing mass fractal aggregates and particle-particle correlation as evidenced by the Q -2.4 power law scattering in the low Q and a liquid-like peak at the high Q regions of the scattering signal from the nanoparticles.

Molecular engineering of electrolyte structures has led to the successful application of trifluoropropylene carbonate (TFPC), a fluorinated derivative of propylene carbonate (PC), in next-generation high-voltage high-energy lithium-ion cell. In contrast to a PC-based electrolyte which cointercalates in the form of Li + -solvated species into the graphene layer and exfoliates a graphite anode, a TFPC-based electrolyte is highly compatible with a graphite anode at low potential. Additionally, it shows exceptional oxidation stability on the charged cathode surface owing to the presence of the −CF 3 group. An allfluorinated electrolyte, that is, 1.0 M LiPF 6 TFPC/2,2,2-trifluoroethyl carbonate (FEMC) (1/1 volume ratio) + FEC additive, was formulated and demonstrated excellent cycling stability in a high-voltage LiNi 0.5 Mn 0.3 Co 0.2 O 2 /graphite cell cycled between 3.0 and 4.6 V.