Electrolyte-Electrocatalyst Interfacial Effects of Polymeric Materials for Tandem CO2 Capture and Conversion Elucidated Using In Situ Electrochemical AFM

Integrating CO2 capture and electrochemical conversion has been proposed as a strategy to reduce the net energy required for CO2 regeneration in traditional CO2 capture and conversion schemes and can be coupled with carbon-free renewable electricity. Polyethylenimine (PEI)-based materials have been previously studied as CO2 capture materials and can be integrated in these reactive capture processes. PEI-based electrolytes have been found to significantly increase the CO2 loading, and impact selectivity and rate of product formation when compared to the conventional aqueous electrolytes. However, the influence of these materials at the catalyst-electrode interface is currently not well understood. In this study, PEI-based electrolytes were prepared and their impact on the morphology of a silver electrode performing electrochemical CO2 reduction (CO2R) was studied using in situ electrochemical atomic force microscopy (EC-AFM). The presence of PEI on the electrode surface could be distinguished based on nanomechanical properties (DMT modulus), and changes were observed as negative polarization was applied, revealing a reorganization of the PEI chains due to electrostatic interactions. These changes were impacted by the electrolyte composition, including the addition of supporting electrolyte KHCO3 salt, as well as CO2 captured by the PEI-based electrolyte, which minimized the change in surface mechanical properties and degree of PEI alignment on the electrode surface. The changes in surface mechanical properties were also dependent on the PEI polymer length, with higher molecular weight PEI showing different reconfiguration than the shorter polymer brushes. The study highlights that the choice of polymer material, the electrolyte composition, and CO2 captured impact the near-electrode environment, which has implications for CO2R, and presents EC-AFM as a new tool that can be used to probe the dynamic behavior of these interfaces during electrocatalysis.

Enthalpic Interactions and Solution Behaviors of Solvent-Free Polymer Brushes

We performed molecular dynamics simulations to characterize the role of enthalpic interaction in impacting the static and dynamic properties of solvent-free polymer brushes. The intrinsic enthalpic interaction in the simulation was introduced using different attraction strengths between distinct species. Two model systems were considered: one consisting of binary brushes of two different polymer types and the other containing a mixture of homopolymer brushes and free molecules. In the first system, we observed that, when two originally incompatible polymers were grafted to opposing surfaces, the miscibility between them was significantly enhanced. A less favorable intrinsic enthalpic interaction in the brushes resulted in a more stretched chain configuration, a lower degree of inter-brush penetration, and faster segmental relaxation. In the second system, we characterized the solvent capacity of the homopolymer brushes from variations in the energy components of the system as a function of the number of free molecules. We determined that molecular absorption was driven by the release of the entropic frustration for the grafted chains in conjunction with the chemical affinity between the solutes and polymers. The solute distribution function within the inter-wall space showed that solute-polymer mixing in the middle of the gap occurred preferentially when the enthalpic interaction was more favorable. When this was not the case, absorption was predominantly localized near the grafting surface. From the mean square displacement of the solute, we found that the brush profiles restrained the molecular diffusion perpendicular to the grafting wall; the weaker the attraction from the brush, the higher the solute mobility.

Single-Ion Conducting Polymer Nanoparticles as Functional Fillers for Solid Electrolytes in Lithium Metal Batteries

Composite solid electrolytes including inorganic nanoparticles or nanofibers which improve the performance of polymer electrolytes due to their superior mechanical, ionic conductivity, or lithium transference number are actively being researched for applications in lithium metal batteries. However, inorganic nanoparticles present limitations such as tedious surface functionalization and agglomeration issues and poor homogeneity at high concentrations in polymer matrixes. In this work, we report on polymer nanoparticles with a lithium sulfonamide surface functionality (LiPNP) for application as electrolytes in lithium metal batteries. The particles are prepared by semibatch emulsion polymerization, an easily up-scalable technique. LiPNPs are used to prepare two different families of particle-reinforced solid electrolytes. When mixed with poly(ethylene oxide) and lithium bis(trifluoromethane)sulfonimide (LiTFSI/PEO), the particles invoke a significant stiffening effect (E' > 10⁶ Pa vs 10⁵ Pa at 80 °C) while the membranes retain high ionic conductivity (σ = 6.6 × 10^-4 S cm^-1). Preliminary testing in LiFePO₄ lithium metal cells showed promising performance of the PEO nanocomposite electrolytes. By mixing the particles with propylene carbonate without any additional salt, we obtain true single-ion conducting gel electrolytes, as the lithium sulfonamide surface functionalities are the only sources of lithium ions in the system. The gel electrolytes are mechanically robust (up to G' = 10⁶ Pa) and show ionic conductivity up to 10^-4 S cm^-1. Finally, the PC nanocomposite electrolytes were tested in symmetrical lithium cells. Our findings suggest that all-polymer nanoparticles could represent a new building block material for solid-state lithium metal battery applications.

Non-flammable liquid electrolytes for safe batteries

With continual increments in energy density gradually boosting the performance of rechargeable alkali metal ion (e.g. Li⁺, Na⁺, K⁺) batteries, their safe operation is of growing importance and needs to be considered during their development. This is essential, given the high-profile incidents involving battery fires as portrayed by the media. Such hazardous events result from exothermic chemical reactions occurring between the flammable electrolyte and the electrode material under abusive operating conditions. Some classes of non-flammable organic liquid electrolytes have shown potential towards safer batteries with minimal detrimental effect on cycling and, in some cases, even enhanced performance. This article reviews the state-of-the-art in non-flammable liquid electrolytes for Li-, Na- and K-ion batteries. It provides the reader with an overview of carbonate, ether and phosphate-based organic electrolytes, co-solvated electrolytes and electrolytes with flame-retardant additives as well as highly concentrated and locally highly concentrated electrolytes, ionic liquids and inorganic electrolytes. Furthermore, the functionality and purpose of the components present in typical non-flammable mixtures are discussed. Moreover, many non-flammable liquid electrolytes are shown to offer improved cycling stability and rate capability compared to conventional flammable liquid electrolytes.

Dynamic Mixing Behaviors of Ionically Tethered Polymer Canopy of Nanoscale Hybrid Materials in Fluids of Varying Physical and Chemical Properties

An emerging area of sustainable energy and environmental research is focused on the development of novel electrolytes that can increase the solubility of target species and improve subsequent reaction performance. Electrolytes with chemical and structural tunability have allowed for significant advancements in flow batteries and CO₂ conversion integrated with CO₂ capture. Liquid-like nanoparticle organic hybrid materials (NOHMs) are nanoscale fluids that are composed of inorganic nanocores and an ionically tethered polymeric canopy. NOHMs have been shown to exhibit enhanced conductivity making them promising for electrolyte applications, though they are often challenged by high viscosity in the neat state. In this study, a series of binary mixtures of NOHM-I-HPE with five different secondary fluids, water, chloroform, toluene, acetonitrile, and ethyl acetate, were prepared to reduce the fluid viscosity and investigate the effects of secondary fluid properties (e.g., hydrogen bonding ability, polarity, and molar volume) on their transport behaviors, including viscosity and diffusivity. Our results revealed that the molecular ratio of secondary fluid to the ether groups of Jeffamine M2070 (λ_SF) was able to describe the effect that secondary fluid has on transport properties. Our findings also suggest that in solution, the Jeffamine M2070 molecules exist in different nanoscale environments, where some are more strongly associated with the nanoparticle surface than others, and the conformation of the polymer canopy was dependent on the secondary fluid. This understanding of the polymer conformation in NOHMs can allow for the better design of an electrolyte capable of capturing and releasing small gaseous or ionic species.

UV-Cured Cross-Linked Astounding Conductive Polymer Electrolyte for Safe and High-Performance Li-Ion Batteries

UV-cured cross-linked polymer electrolytes are promising electrolytes for safe Li-ion batteries (LIBs) application due to their excellent conduction ability, low glass-transition temperature (T_g), and high discharge capacity. Herein, we have prepared novel fluorosulfonylimide methacrylic-based cross-linked polymer electrolyte membranes for LIBs via UV-curing process, which is a well-known, easy, low-cost, fast, and reliable technique. The synthesized UV-reactive novel methacrylate monomer with directly attached fluorosulfonylimide functional group methacryloylcarbamoyl sulfamoyl fluoride (MACSF) was used as a precursor for UV curing along with poly(ethylene glycol) dimethacrylate (PEGDMA) and lithium bis(fluorosulfonyl)imide (LiFSI). The results demonstrated that the cross-linked membrane with an optimized amount (30 wt %) of MACSF monomer (noted as CPE-3) showed the best performance. The nonflammable fluorosulfonyl group (a hydrophilic group of MACSF monomer) in the polymer matrix formed a wide channel, as a result of which Li ion can migrate easily via forming an ionic linkage. The CPE-3 electrolyte exhibited a low T_g (-79 °C), excellent phase separation, high conductivity (σ) (ca. 3.5 × 10^-4 and 8.50 × 10^-3 S·cm^-1 at 30 and 80 °C, respectively), and high flame retardancy. The battery performance of half-cell (LiFePO₄/CPE-3/Li) and full cell (LiFePO₄/CPE-3/graphite) with CPE-3 electrolyte were attractive: discharge capacities (155 and 152 mAh/g) with the capacity retentions of 96.17 and 95.17% after 500 cycles at 0.1 C rate for half-cell and full-cell LIBs, respectively.

Interactions between Sterically Stabilized Nanoparticles: The Effects of Brush Bidispersity and Chain Stiffness

Density Functional Theory is employed to study structural properties and interactions between solvent-free polymer-grafted nanoparticles. Both monodisperse and bidisperse polymer brushes with variable chain stiffness are considered. The three major control parameters are the grafting density, the grafted chain length, and its stiffness. The effect of these parameters on the brush-brush overlap and attractive interaction strength is analyzed. The Density Functional Theory results are compared with the available simulation data, and good quantitative agreement is found.

Solid Polymer Electrolytes with High Conductivity and Transference Number of Li Ions for Li-Based Rechargeable Batteries

Smart electronics and wearable devices require batteries with increased energy density, enhanced safety, and improved mechanical flexibility. However, current state-of-the-art Li-based rechargeable batteries (LBRBs) use highly reactive and flowable liquid electrolytes, severely limiting their ability to meet the above requirements. Therefore, solid polymer electrolytes (SPEs) are introduced to tackle the issues of liquid electrolytes. Nevertheless, due to their low Li⁺ conductivity and Li⁺ transference number (LITN) (around 10^-5 S cm^-1 and 0.5, respectively), SPE-based room temperature LBRBs are still in their early stages of development. This paper reviews the principles of Li⁺ conduction inside SPEs and the corresponding strategies to improve the Li⁺ conductivity and LITN of SPEs. Some representative applications of SPEs in high-energy density, safe, and flexible LBRBs are then introduced and prospected.

Structural and Dynamical Coupling in Solvent-Free Polymer Brushes Elucidated by Molecular Dynamics Simulations

We investigate the chain configuration and segmental dynamics in interacting solvent-free polymer brushes using molecular dynamics simulations. The brush systems are designed to mimic the interstitial space between a pair of neighboring polymer-grafted nanoparticles in solvent-free nanoparticle-organic hybrid materials. Each brush consists of uniformly grafted chains formed by a given number of monomer beads. In monodisperse systems, two opposing brushes have the same chain length and grafting density. In mixed conditions, we consider binary systems with two surfaces being separately grafted with polymers of distinct chain lengths at different grafting densities as well as bidisperse systems with polymers of two different lengths being tethered to the surfaces at a fixed grafting density. We demonstrate that the brush configuration and interpenetration are both governed by the need that monomer beads have to uniformly fill the space. For systems with longer chain lengths and/or higher grafting densities, the larger interwall separation yields more stretched brush conformations and reduced extents of interbrush mixing. As a result, the polymer configurational entropy is generally decreased and the segment-to-segment relaxation dynamics is slowed down accordingly. The grafting of chains at a high density not only makes the relaxation dynamics deviate from the standard Rouse prediction but also leads to distinct relaxation times for the free and tethered segments. The more slowly relaxing tethered segments play a more important role in determining the overall end-to-end fluctuations. Moreover, the two distinct relaxation processes are consistent with the two-stage decay in the Rouse mode fluctuation autocorrelation function. In the presence of brush bidispersity, the collaboration between polymers of different lengths is evidently observed in the brush profiles. The variations of the chain configuration for the two polymers are complementary, and the associated relaxation dynamics of the two species are significantly coupled.

Multilayered PVDF-HFP Porous Separator via Phase Separation and Selective Solvent Etching for High Voltage Lithium-Ion Batteries

The development of highly porous and thin separator is a great challenge for lithium-ion batteries (LIBs). However, the inevitable safety issues always caused by poor mechanical integrity and internal short circuits of the thin separator must be addressed before this type of separator can be applied to lithium-ion batteries. Here, we developed a novel multilayer poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane with a highly porous and lamellar structure, through a combination of evaporation-induced phase separation and selective solvent etching methods. The developed membrane is capable of a greater amount of electrolyte uptake and excellent electrolyte retention resulting from its superior electrolyte wettability and highly porous structure, thereby offering better electrochemical performance compared to that of a commercial polyolefin separator (Celgard). Moreover, benefiting from the layered configuration, the tensile strength of the membrane can reach 13.5 MPa, which is close to the mechanical strength of the Celgard type along the transversal direction. The elaborate design of the multilayered structure allows the fabrication of a new class of thin separators with significant improvements in the mechanical and electrochemical performance. Given safer operation, the developed multilayer membrane may become a preferable separator required for high-power and high-energy storage devices.

Spectroscopic Investigation of Entropic Canopy-Canopy Interactions of Nanoparticle Organic Hybrid Materials

Nanoparticle organic hybrid materials (NOHMs) are self-suspended liquid-like nanoparticle-based functional materials consisting of a surface-functionalized inorganic nanocore and oligomeric or polymeric chains. They often exhibit complex intermolecular and intramolecular interactions among their constituents, resulting in versatile physicochemical characteristics that range from glassy solids to solvent-free nanoparticle fluids. A variety of applications involving NOHMs have been investigated thus far, including thermal management fluids, lubricants, magnetic fluids, nanocomposites, electrolytes, water treatment and biomass pretreatment chemicals, and CO₂ capture solvents. In particular, NOHMs have recently been recognized as a promising CO₂ capture and utilization medium. To capture CO₂ more effectively, a variety of specific functional groups of strong chemical affinity to CO₂ can be added to the polymeric canopy (enthalpic contribution), and various steric considerations induced by attractive/repulsive interactions among the nanocores and canopies can be introduced (entropic contribution). These occur while maintaining negligible vapor pressure and enhanced thermal stability. Here, we investigated the canopy dynamics of NOHMs with different-sized SiO₂ nanocores, aiming to reveal the hidden nature of the entropic interaction occurring in NOHMs. Pulse-field gradient nuclear magnetic resonance spectroscopy (with ¹H) was employed to investigate the canopy dynamics of the NOHMs synthesized using 7, 12, and 22 nm SiO₂ particles, and these results were compared with those from a ternary mix of all three sizes of SiO₂ nanocores. The self-diffusion coefficient and thermal diffusivity were also evaluated.

Designing All-Polymer Nanostructured Solid Electrolytes: Advances and Prospects

Multi-phase nanostructured polymer electrolytes, where the one phase conducts ions while the other imparts the desired mechanical properties, are currently the most promising candidates for solid-state electrolytes in high-density lithium metal batteries. In contrast to homogeneous polymer electrolytes, where ion transport is coupled with polymer segmental dynamics and any attempt to improve conductivity via faster polymer motions results in a decrease in stiffness, nanostructured materials efficiently decouple these two antagonistic parameters. Nevertheless, for reasons discussed herein the synthesis of a polymer electrolyte that simultaneously has a shear modulus of G' ≈ GPa and an ion conductivity of σ > 10-4 S/cm (in the case dual ion conductor) or of σ > 10-5 S/cm (in the case of single-ion conductor) remains a challenge. This review focuses on recent designing strategies for the synthesis of all-polymer nanostructured electrolytes, and protocols for introducing a single-ion character in such materials.

Entropic Effects in Solvent-Free Bidisperse Polymer Brushes Investigated Using Density Functional Theories

Solvent-free polymer-functionalized nanoparticles form a special type of colloid composed of inorganic cores self-suspended by their grafted coronas. In the absence of intervening solvent molecules, the fluidity of the system is provided by these tethered polymers as they fill the space. Here, we study the structure and interaction of neighboring polymer-grafted surfaces in the solvent-free condition using mean-field density functional theories. For opposing flat surfaces, the brush configuration and the associated energy landscape are semianalytically investigated given the incompressibility of the tethered entropic chains. The effect of brush polydispersity (including variations in both chain length and surface grafting density) is considered by two bidisperse models corresponding to different physical scenarios: one for opposing brushes uniformly mixed with two species at a fixed grafting density, and the other for opposing brushes with distinct chain lengths and grafting densities. The space-filling capabilities of the neighboring coronas differ not only by their ratio of radii of gyration for the composing polymers but also by their ratio of grafting densities. We show that the system energy depicts a steric repulsion as the brushes are compressed, which is typical for hairy particles in a solvent. However, as the interwall separation increases, the cooperative stretching of the chains leads to an entropic attraction between them, a unique characteristic of solventless systems. The corresponding brush profiles change from a bell-like shape to a more step-function-like feature as the interwall spacing increases significantly. The interwall separation associated with the overall free energy minimum therefore characterizes the favorable interparticle spacing for solvent-free polymer-functionalized particles. The limiting accessible parameter space of polymer sizes and grafting densities subjected to the space-filling constraint is comprehensively explored for representative interparticle spacing characterizing the compressed, relaxed, and stretched regimes for a given polymer species, respectively. Such information would be useful for guiding the design of experimental solvent-free polymer-functionalized nanoparticles.

Stabilizing polymer electrolytes in high-voltage lithium batteries

Electrochemical cells that utilize lithium and sodium anodes are under active study for their potential to enable high-energy batteries. Liquid and solid polymer electrolytes based on ether chemistry are among the most promising choices for rechargeable lithium and sodium batteries. However, uncontrolled anionic polymerization of these electrolytes at low anode potentials and oxidative degradation at working potentials of the most interesting cathode chemistries have led to a quite concession in the field that solid-state or flexible batteries based on polymer electrolytes can only be achieved in cells based on low- or moderate-voltage cathodes. Here, we show that cationic chain transfer agents can prevent degradation of ether electrolytes by arresting uncontrolled polymer growth at the anode. We also report that cathode electrolyte interphases composed of preformed anionic polymers and supramolecules provide a fundamental strategy for extending the high voltage stability of ether-based electrolytes to potentials well above conventionally accepted limits.

Confining electrodeposition of metals in structured electrolytes

Electrochemical cells based on alkali metal (Li, Na) anodes have attracted significant recent attention because of their promise for producing large increases in gravimetric energy density for energy storage in batteries. To facilitate stable, long-term operation of such cells a variety of structured electrolytes have been designed in different physical forms, ranging from soft polymer gels to hard ceramics, including nanoporous versions of these ceramics that host a liquid or molten polymer in their pores. In almost every case, the electrolytes are reported to be substantially more effective than anticipated by early theories in improving uniformity of deposition and lifetime of the metal anode. These observations have been speculated to reflect the effect of electrolyte structure in regulating ion transport to the metal electrolyte interface, thereby stabilizing metal electrodeposition processes at the anode. Here we create and study model structured electrolytes composed of covalently linked polymer grafted nanoparticles that host a liquid electrolyte in the pores. The electrolytes exist as freestanding membranes with effective pore size that can be systematically manipulated through straightforward control of the volume fraction of the nanoparticles. By means of physical analysis and direct visualization experiments we report that at current densities approaching the diffusion limit, there is a clear transition from unstable to stable electrodeposition at Li metal electrodes in membranes with average pore sizes below 500 nm. We show that this transition is consistent with expectations from a recent theoretical analysis that takes into account local coupling between stress and ion transport at metal-electrolyte interfaces.

Designing solid-liquid interphases for sodium batteries

Secondary batteries based on earth-abundant sodium metal anodes are desirable for both stationary and portable electrical energy storage. Room-temperature sodium metal batteries are impractical today because morphological instability during recharge drives rough, dendritic electrodeposition. Chemical instability of liquid electrolytes also leads to premature cell failure as a result of parasitic reactions with the anode. Here we use joint density-functional theoretical analysis to show that the surface diffusion barrier for sodium ion transport is a sensitive function of the chemistry of solid–electrolyte interphase. In particular, we find that a sodium bromide interphase presents an exceptionally low energy barrier to ion transport, comparable to that of metallic magnesium. We evaluate this prediction by means of electrochemical measurements and direct visualization studies. These experiments reveal an approximately three-fold reduction in activation energy for ion transport at a sodium bromide interphase. Direct visualization of sodium electrodeposition confirms large improvements in stability of sodium deposition at sodium bromide-rich interphases.

The chemistry at the interface between electrolyte and electrode plays a critical role in determining battery performance. Here, the authors show that a NaBr enriched solid–electrolyte interphase can lower the surface diffusion barrier for sodium ions, enabling stable electrodeposition.

Composite Polymer Electrolytes with Li7La3Zr2O12 Garnet-Type Nanowires as Ceramic Fillers: Mechanism of Conductivity Enhancement and Role of Doping and Morphology

Composite polymer solid electrolytes (CPEs) containing ceramic fillers embedded inside a polymer-salt matrix show great improvements in Li⁺ ionic conductivity compared to the polymer electrolyte alone. Lithium lanthanum zirconate (Li₇La₃Zr₂O₁₂, LLZO) with a garnet-type crystal structure is a promising solid Li⁺ conductor. We show that by incorporating only 5 wt % of the ceramic filler comprising undoped, cubic-phase LLZO nanowires prepared by electrospinning, the room temperature ionic conductivity of a polyacrylonitrile-LiClO₄-based composite is increased 3 orders of magnitude to 1.31 × 10^-4 S/cm. Al-doped and Ta-doped LLZO nanowires are also synthesized and utilized as fillers, but the conductivity enhancement is similar as for the undoped LLZO nanowires. Solid-state nuclear magnetic resonance (NMR) studies show that LLZO NWs partially modify the PAN polymer matrix and create preferential pathways for Li⁺ conduction through the modified polymer regions. CPEs with LLZO nanoparticles and Al₂O₃ nanowire fillers are also studied to elucidate the role of filler type (active vs passive), LLZO composition (undoped vs doped), and morphology (nanowire vs nanoparticle) on the CPE conductivity. It is demonstrated that both intrinsic Li⁺ conductivity and nanowire morphology are needed for optimal performance when using 5 wt % of the ceramic filler in the CPE.

Particle localization and hyperuniformity of polymer-grafted nanoparticle materials

The properties of materials largely reflect the degree and character of the localization of the molecules comprising them so that the study and characterization of particle localization has central significance in both fundamental science and material design. Soft materials are often comprised of deformable molecules and many of their unique properties derive from the distinct nature of particle localization. We study localization in a model material composed of soft particles, hard nanoparticles with grafted layers of polymers, where the molecular characteristics of the grafted layers allow us to "tune" the softness of their interactions. Soft particles are particular interesting because spatial localization can occur such that density fluctuations on large length scales are suppressed, while the material is disordered at intermediate length scales; such materials are called "disordered hyperuniform". We use molecular dynamics simulation to study a liquid composed of polymer-grafted nanoparticles (GNP), which exhibit a reversible self-assembly into dynamic polymeric GNP structures below a temperature threshold, suggesting a liquid-gel transition. We calculate a number of spatial and temporal correlations and we find a significant suppression of density fluctuations upon cooling at large length scales, making these materials promising for the practical fabrication of "hyperuniform" materials.

Designer interphases for the lithium-oxygen electrochemical cell

An electrochemical cell based on the reversible oxygen reduction reaction: 2Li⁺ + 2e ^- + O₂↔ Li₂O₂, provides among the most energy dense platforms for portable electrical energy storage. Such Lithium-Oxygen (Li-O₂) cells offer specific energies competitive with fossil fuels and are considered promising for electrified transportation. Multiple, fundamental challenges with the cathode, anode, and electrolyte have limited practical interest in Li-O₂ cells because these problems lead to as many practical shortcomings, including poor rechargeability, high overpotentials, and specific energies well below theoretical expectations. We create and study in-situ formation of solid-electrolyte interphases (SEIs) based on bromide ionomers tethered to a Li anode that take advantage of three powerful processes for overcoming the most stubborn of these challenges. The ionomer SEIs are shown to protect the Li anode against parasitic reactions and also stabilize Li electrodeposition during cell recharge. Bromine species liberated during the anchoring reaction also function as redox mediators at the cathode, reducing the charge overpotential. Finally, the ionomer SEI forms a stable interphase with Li, which protects the metal in high Gutmann donor number liquid electrolytes. Such electrolytes have been reported to exhibit rare stability against nucleophilic attack by Li₂O₂ and other cathode reaction intermediates, but also react spontaneously with Li metal anodes. We conclude that rationally designed SEIs able to regulate transport of matter and ions at the electrolyte/anode interface provide a promising platform for addressing three major technical barriers to practical Li-O₂ cells.

Solid polymer electrolyte based on ionic bond or covalent bond functionalized silica nanoparticles

This article reports a solid polymer electrolyte based on ionic bond or covalent bond functionalized silica nanoparticles for lithium ion batteries.

Self-assembly of polymer-grafted nanoparticles in solvent-free conditions

Grafting of polymer chains onto the surface of spherical nanoparticles leads to a hybrid type of fluid that exhibits properties of both particle suspensions and melts of star polymers-these properties being controlled by the relative dimensions of the grafted polymer chains to the nanoparticle diameter, D, and the number of the number of chains grafted on the nanoparticle surface, f. While polymer-grafted nanoparticles (GNP) of this kind typically have a spherical average shape after grafting even a moderate number of chains, their instantaneous molecular shape can fluctuate significantly due to the deformation of the grafted chains. Both simulations and measurements have previously revealed that these "conformationally polarizable" particles can exhibit self-assembly into large scale polymeric structures in both solution and in polymer melts, and we simulate polymer-grafted nanoparticles with D and temperature (T) variations without a dispersing solvent to better understand the nature of this self-assembly process. We observe a reversible self-assembly into linear and branched dynamic GNP structures, where the extent of the assembly and geometry depend on D and T, and we constructed a map capturing the GNP structural behavior with D and T variations. Since the shape of the GNPs appeared to be correlated with the occurrence of the GNP self-assembly, we quantified the average shape and a measure of shape fluctuations to better understand how molecular shape influences their propensity to self-assemble into different structural forms. Based on this framework, we describe the clustering process of the GNPs as an equilibrium polymerization phenomenon and we calculate the order parameter governing the dynamic clustering behavior of GNPs, the average mass of the clusters, size distribution, and the apparent fractal dimension of the clusters.

A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles

Rough electrodeposition, uncontrolled parasitic side-reactions with electrolytes and dendrite-induced short-circuits have hindered development of advanced energy storage technologies based on metallic lithium, sodium and aluminium electrodes. Solid polymer electrolytes and nanoparticle-polymer composites have shown promise as candidates to suppress lithium dendrite growth, but the challenge of simultaneously maintaining high mechanical strength and high ionic conductivity at room temperature has so far been unmet in these materials. Here we report a facile and scalable method of fabricating tough, freestanding membranes that combine the best attributes of solid polymers, nanocomposites and gel-polymer electrolytes. Hairy nanoparticles are employed as multifunctional nodes for polymer crosslinking, which produces mechanically robust membranes that are exceptionally effective in inhibiting dendrite growth in a lithium metal battery. The membranes are also reported to enable stable cycling of lithium batteries paired with conventional intercalating cathodes. Our findings appear to provide an important step towards room-temperature dendrite-free batteries.

There is intensive research effort in suppressing lithium dendrite growth in lithium batteries. Here, the authors report the use of a crosslinked nanoparticle-polymer composite membrane with high mechanical strength and ionic conductivity which enables stable cycling of lithium metal batteries.

Dynamics and yielding of binary self-suspended nanoparticle fluids

Yielding and flow transitions in bi-disperse suspensions of particles are studied using a model system comprised of self-suspended spherical nanoparticles. An important feature of the materials is that the nanoparticles are uniformly dispersed in the absence of a solvent. Addition of larger particles to a suspension of smaller ones is found to soften the suspensions, and in the limit of large size disparities, completely fluidizes the material. We show that these behaviors coincide with a speeding-up of de-correlation dynamics of all particles in the suspensions and are accompanied by a reduction in the energy dissipated at the yielding transition. We discuss our findings in terms of ligand-mediated jamming and un-jamming of hairy particle suspensions.

Self-suspended suspensions of covalently grafted hairy nanoparticles

Dispersions of small particles in liquids have been studied continuously for almost two centuries for their ability to simultaneously advance understanding of physical properties of fluids and their widespread use in applications. In both settings, the suspending (liquid) and suspended (solid) phases are normally distinct and uncoupled on long length and time scales. In this study, we report on the synthesis and physical properties of a novel family of covalently grafted nanoparticles that exist as self-suspended suspensions with high particle loadings. In such suspensions, we find that the grafted polymer chains exhibit unusual multiscale structural transitions and enhanced conformational stability on subnanometer and nanometer length scales. On mesoscopic length scales, the suspensions display exceptional homogeneity and colloidal stability. We attribute this feature to steric repulsions between grafted chains and the space-filling constraint on the tethered chains in the single-component self-suspended materials, which inhibits phase segregation. On macroscopic length scales, the suspensions exist as neat fluids that exhibit soft glassy rheology and, counterintuitively, enhanced elasticity with increasing temperature. This feature is discussed in terms of increased interpenetration of the grafted chains and jamming of the nanoparticles.