Superionic Bifunctional Polymer Electrolytes for Solid-State Energy Storage and Conversion

Piezoelectric Polymer Solid Electrolyte Integrating Electromechanical Coupling and Ferroelectric Polarization Effects

The unsatisfactory lithium-ion conductivity (σ) and limited mechanical strength of polymer solid electrolytes hinder their wide applications in solid-state lithium metal batteries (SSLMBs). Here, a thin piezoelectric polymer solid electrolyte integrating electromechanical coupling and ferroelectric polarization effects has been designed and prepared to achieve long-term stable cycling of SSLMBs. The ferroelectric Bi4Ti3O12 nanoparticle (BIT NPs) loaded poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) piezoelectric nanofibers (B-P NFs) membranes are introduced into the poly(ethylene oxide) (PEO) matrix, endowing the composite electrolyte with unique polarization and piezoelectric effects. The piezoelectric nanofiber membrane with a 3D network structure not only promotes the dissociation of lithium (Li) salts through the polarization effect but also cleverly utilizes the coupling effect of a mechanical stress-local electric field to achieve dynamic regulation of the Li electroplating process. Through the corresponding experimental tests and density functional theory calculations, the intrinsic mechanism of piezoelectric electrolytes improving σ and suppressing Li dendrites is fully revealed. The obtained piezoelectric electrolyte has achieved stable cycling of LiFePO4 batteries over 2000 cycles and has also shown good practical application potential in flexible pouch batteries.

Self-assembly of water-filled molecular saddles to generate diverse morphologies and high proton conductivity

The design of single-component organic compounds acting as efficient solid-state proton conduction (SSPC) materials has been gaining significant traction in recent times. Molecular design and controlled self-assembly are critical components in achieving highly efficient SSPC. In this work, we report the design, synthesis, and self-assembly of an organic macrocyclic aza-crown-type compound, P2Mac, which complements synthetic ease with efficient SSPC. P2Mac is derived from the pyridine-2,6-dicarboxamide (PDC) framework and contains polar amide and amine residues in its inner region, while aromatic residues occupy the periphery of the macrocycle. The crystal structure analysis revealed that P2Mac adopts a saddle-shaped geometry. Each P2Mac molecule interacts with one water molecule that is present in its central polar cavity, stabilized by a network of five hydrogen bonds. We could self-assemble P2Mac in a variety of unique, aesthetically pleasing morphologies such as micron-sized octahedra, hexapods, as well as hollow nanoparticles, and microrods. The water-filled polar channels formed through the stacking of P2Mac allow attaining a high proton conductivity value of 21.1 mS cm-1 at 27 °C under a relative humidity (RH) of 95% in the single crystals of P2Mac, while the as-prepared P2Mac pellet sample exhibited about three-orders of magnitude lower conduction under these conditions. The low activation energy of 0.39 eV, calculated from the Arrhenius plot, indicates the presence of the Grotthus proton hopping mechanism in the transport process. This report highlights the pivotal role of molecular design and self-assembly in creating high-performance SSPC organic materials.

A Fast Na-Ion Conduction Polymer Electrolyte via Triangular Synergy Strategy for Quasi-Solid-State Batteries

Polymer electrolytes provide a visible pathway for the construction of high-safety quasi-solid-state batteries due to their high interface compatibility and processability. Nevertheless, sluggish ion transfer at room temperature seriously limits their applications. Herein, a triangular synergy strategy is proposed to accelerate Na-ion conduction via the cooperation of polymer-salt, ionic liquid, and electron-rich additive. Especially, PVDF-HFP and NaTFSI salt acted as the framework to stably accommodate all the ingredients. An ionic liquid (Emim+ -FSI- ) softened the polymer chains through a weakening molecule force and offered additional liquid pathways for ion transport. Physicochemical characterizations and theoretical calculations demonstrated that electron-rich Nerolin with π-cation interaction facilitated the dissociation of NaTFSI and effectively restrained the competitive migration of large cations from EmimFSI, thus lowering the energy barrier for ion transport. The strategy resulted in a thin F-rich interphase dominated by NaTFSI salt's decomposition, enabling rapid Na+ transmission across the interface. These combined effects resulted in a polymer electrolyte with high ionic conductivity (1.37×10-3  S cm-1 ) and tNa+ (0.79) at 25 °C. The assembled cells delivered reliable rate capability and stability (200 cycles, 99.2 %, 0.5 C) with a good safety performance.

Enhanced ionic conductivity in block copolymer electrolytes through interfacial passivation using mixed ionic liquids

We present a strategic approach for enhancing the ionic conductivity of block copolymer electrolytes. This was achieved by introducing mixed ionic liquids (ILs) with varying molar ratios, wherein the imidazolium cation was paired with either tetrafluoroborate (BF4) anion or bis(trifluoromethylsulfonyl)imide (TFSI) anion. Two polymer matrices, poly(4-styrenesulfonate)-b-polymethylbutylene (SSMB) and poly(4-styrenesulfonyl (trifluoromethanesulfonyl)imide)-b-polymethylbutylene (STMB), were synthesized for this purpose. All the SSMB and STMB containing mixed ILs showed hexagonal cylindrical structures, but the type of tethered acid group significantly influenced the interfacial properties. STMB electrolytes demonstrated enhanced segregation strength, which was attributed to strengthened Coulomb and hydrogen bonding interactions in the ionic domains, where the ILs were uniformly distributed. In contrast, the SSMB electrolytes exhibited increased concentration fluctuations because the BF4 anions were selectively sequestered at the block interfaces. This resulted in the effective confinement of imidazolium TFSI along the ionic domains, thereby preventing ion trapping in dead zones and facilitating rapid ion diffusion. Consequently, the SSMB electrolytes with mixed ILs demonstrated significantly improved ionic conductivities, surpassing the expected values based on the arithmetic average of the conductivities of each IL, whereas the ionic conductivity of the STMB was aligned with the expected average. The methodology explored in this study holds great promise for the development of solid-state polymer electrolytes.

Ions-Silica Percolated Ionic Dielectric Elastomer Actuator for Soft Robots

Soft robotics systems are currently under development using ionic electroactive polymers (i-EAP) as soft actuators for the human-machine interface. However, this endeavor has been impeded by the dilemma of reconciling the competing demands of force and strain in i-EAP actuators. Here, the authors present a novel design called "ions-silica percolated ionic dielectric elastomer (i-SPIDER)", which exhibits ionic liquid-confined silica microstructures that effectively resolve the chronic issue of conventional i-EAP actuators. The i-SPIDER actuator demonstrates remarkable electromechanical conversion capacity at low voltage, thanks to improved ion accumulation facilitated by interpreting electrode polarization at the electrolyte-electrode interface. This approach concurrently enhances both strain (by approximately 1.52%) and force (by roughly 1.06 mN) even at low Young's modulus (merely 5.9 MPa). Additionally, by demonstrating arachnid-inspired soft robots endowed with user-desired tasks through control of various form factors, the development of soft robots using the i-SPIDER that can concomitantly enhance strain and force holds promise as a compelling avenue for ushering in the next generation of miniaturized, low-powered soft robotics.

Interfacial engineered superelastic metal-organic framework aerogels with van-der-Waals barrier channels for nerve agents decomposition

Chemical warfare agents (CWAs) significantly threaten human peace and global security. Most personal protective equipment (PPE) deployed to prevent exposure to CWAs is generally devoid of self-detoxifying activity. Here we report the spatial rearrangement of metal-organic frameworks (MOFs) into superelastic lamellar-structured aerogels based on a ceramic network-assisted interfacial engineering protocol. The optimized aerogels exhibit efficient adsorption and decomposition performance against CWAs either in liquid or aerosol forms (half-life of 5.29 min, dynamic breakthrough extent of 400 L g^-1) due to the preserved MOF structure, van-der-Waals barrier channels, minimized diffusion resistance (~41% reduction), and stability over a thousand compressions. The successful construction of the attractive materials offers fascinating perspectives on the development of field-deployable, real-time detoxifying, and structurally adaptable PPE that could be served as outdoor emergency life-saving devices against CWAs threats. This work also provides a guiding toolbox for incorporating other critical adsorbents into the accessible 3D matrix with enhanced gas transport properties.

Predictive Molecular Models for Charged Materials Systems: From Energy Materials to Biomacromolecules

Electrostatic interactions play a dominant role in charged materials systems. Understanding the complex correlation between macroscopic properties with microscopic structures is of critical importance to develop rational design strategies for advanced materials. But the complexity of this challenging task is augmented by interfaces present in the charged materials systems, such as electrode-electrolyte interfaces or biological membranes. Over the last decades, predictive molecular simulations that are founded in fundamental physics and optimized for charged interfacial systems have proven their value in providing molecular understanding of physicochemical properties and functional mechanisms for diverse materials. Novel design strategies utilizing predictive models have been suggested as promising route for the rational design of materials with tailored properties. Here, an overview of recent advances in the understanding of charged interfacial systems aided by predictive molecular simulations is presented. Focusing on three types of charged interfaces found in energy materials and biomacromolecules, how the molecular models characterize ion structure, charge transport, morphology relation to the environment, and the thermodynamics/kinetics of molecular binding at the interfaces is discussed. The critical analysis brings two prominent field of energy materials and biological science under common perspective, to stimulate crossover in both research field that have been largely separated.