Single-ion-conducting electrolytes enable easy processingand canblock Li dendritic growth, showing potential for use in solid-statebatteries. We report solid electrolytes that combine a rigid-rod polyanion,poly(2,2 & PRIME;-disulfonyl-4,4 & PRIME;-benzidine terephthalamide)(PBDT), with Na+ or Li+ counterions, and poly(ethyleneglycol) (PEG, M (n) = 400 g mol(-1)). PBDT-PEG membranes show Young's modulus from 90 to 2110MPa that increases with the PBDT content and is >4x higherforLi-based vs Na-based electrolytes. We attribute this dramaticallyhigher modulus in LiPBDT-PEG to poorer ion dissociation betweenLi(+) and PBDT sulfonate groups and stronger interactionsbetween LiPBDT and PEG. These membranes show an increase in ionicconductivity with increasing PEG concentration (0.1-7 & mu;Scm(-1) at 30 & DEG;C), reaching 0.13 mS cm(-1) at 120 & DEG;C. These materials use highly rigid and charged PBDTdouble helices to "solidify" low-molecular-weight PEGinto mechanically strong and highly single-ion-conductive solid polymerelectrolytes with high thermal stability. Their combination of highcation conductivity and high modulus exceeds those of competing single-ionconductors at 30 & DEG;C.

Lithium batteries rely crucially on fast charge and mass transport of Li+ in the electrolyte. For liquid and polymer electrolytes with added lithium salts, Li+ couples to the counter-anion to form ionic clusters that produce inefficient Li+ transport and lead to Li dendrite formation. Quantification of Li+ transport in glycerol-salt electrolytes via NMR experiments and MD simulations reveals a surprising Li+-hopping mechanism. The Li+ transference number, measured by ion-specific electrophoretic NMR, can reach 0.7, and Li+ diffusion does not correlate with nearby ion motions, even at high salt concentration. Glycerol's high density of hydroxyl groups increases ion dissociation and slows anion diffusion, while the close proximity of hydroxyls and anions lowers local energy barriers, facilitating Li+ hopping. This system represents a bridge between liquid and inorganic solid electrolytes, thus motivating new molecular designs for liquid and polymer electrolytes to enable the uncorrelated Li+-hopping transport needed for fast-charging and all-solid-state batteries.

Six molecular ionic composite electrolyte films were produced by combining a rigid-rod polyelectrolyte and various ionic liquids. These electrolytes exhibit both higher modulus and room temperature ionic conductivity than other polymer-based electrolytes.

Molecular ionic composites (MICs), made from ionic liquids and a rigid‐rod polymer poly(2,2′‐disulfonyl‐4,4′‐benzidine terephthalamide) (PBDT), are a new type of rigid gel electrolyte that combine fast ion transport with high thermal stability and mechanical strength. In this work, a MIC electrolyte membrane is prepared that is composed of PBDT, lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyr 14 TFSI) in a mass ratio of 10:10:80. The ionic conductivity at 25 ° C is 0.56 mS cm −1 with no added flammable/volatile components. Although the polymer content is only 10 wt%, this MIC membrane is rigid with a tensile modulus of 410 MPa at room temperature. The MIC membrane remains stable and rigid at 200 ° C with the shear storage modulus ( G ′) only slightly decreasing by 35%. Li/MIC/LiFePO 4 cells demonstrate stable cycling performance over a wide temperature range from 23 to 150 ° C. The specific discharge capacity at 100 and 150 ° C at 1 C rate exceeds 160 mAh g −1 . The discharge capacity retention is 99% after 50 cycles at 150 ° C. This stable battery performance shows that this low polymer content MIC membrane qualifies for use as a solid electrolyte in lithium metal batteries operating over a wide temperature range.

Materials exhibiting high dielectric constants (ϵ_{s}) are critical for energy storage and actuators. A successful approach to increase ϵ_{s} is to incorporate polar additives (with high ϵ_{s}) but controlling the resulting dispersion state is difficult. Here, we show that significant ϵ_{s} increases are realized by adding zwitterions, which are small molecules with a cation and an anion separated by covalent bonds. The increase in ϵ_{s} with zwitterion addition is attributed to the large molecular dipole of zwitterions, ranging from 35 to 41 D, as experimentally quantified and confirmed using density functional theory. At elevated zwitterion concentration in an ethylene glycol medium, there is a nonlinear increase of ϵ_{s} that eventually saturates due to the strong Coulombic interactions between zwitterions. The presented work provides a fundamental molecular understanding of why zwitterions are effective additives in boosting ϵ_{s} in soft materials.

Polymer electrolytes show promise as alternatives to conventional electrolytes in energy storage and conversion devices but have been limited due to their inverse correlation between ionic conductivity and modulus. In this study, we examine surface morphology, linear viscoelastic, dielectric and diffusive properties of molecular ionic composites (MICs), materials produced through the combination of a rigid and charged double helical polymer, poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) (PBDT), and ionic liquids (ILs). To probe temperature extremes, we incorporate a non-crystallizable IL to allow measurements from -90 to 200 degrees C. As we increase the PBDT weight percentage, shear moduli increase and do not decay up to 200 degrees C while maintaining room temperature ionic conductivity within a factor of 2 of the neat IL. We connect diffusion coefficients of IL ions with ionic conductivity through the Haven ratio across a wide temperature range and analyze trends in ion transport based on a relatively high and composition-dependent static dielectric constant. This behavior may result from collective rearrangement of IL ions in these networks. We propose that these properties are driven by a two-phase system in MICs corresponding to IL-rich "puddles" and PBDT-IL associated "bundles" where IL ions form alternating sheaths of cations and anions around each PBDT rod. These polymer-based MIC electrolytes show great promise for use in electrochemical devices that require fast ion transport, high modulus, and a broad thermal window.

Polymer nanocomposites containing carbon nanomaterials such as carbon black, carbon nanotubes, and graphene exhibit exceptional mechanical, thermal, electrical, and gas-barrier properties. Although...