ACS Materials Letters最新文献

Self-healing polyurethane (SHPU) shows great potential in enhancing materials’ durability and sustainability, yet balancing robust mechanical properties with efficient self-healing under mild conditions remains challenging. Conventional approaches often sacrifice strength or healing ability. This Review focuses on the key role of biomass-derived materials, including lignin, cellulose, chitosan, and vegetable oils, in resolving this conflict. Acting as dynamic network modifiers, multifunctional enhancers, and microstructural regulators, they enable sacrificial bonding, microphase separation, and improved chain mobility. Biomass-based SHPUs can achieve over 90% self-healing efficiency at room temperature while maintaining strength and toughness and even incorporate additional functions like flame retardancy or conductivity. Moreover, biomass enhances sustainability by reducing fossil resource dependence and promoting recyclability. Despite challenges in performance consistency and raw material variability, molecular engineering offers a promising path toward high-performance, sustainable SHPUs for advanced manufacturing and a circular economy.

Doctor-blading is a promising alternative for the large-area printing of organic solar cells (OSCs). However, the power conversion efficiencies (PCEs) of doctor-bladed OSCs are still lower than those of their spin-cast counterparts. This is mainly caused by the prolonged molecular organization time during which excessive aggregation can be encouraged. In this work, a post-treatment using nitrogen gas to blow the backside of the photoactive layer, i.e., the ITO glass side, was utilized to modulate the aggregation growth after blade-coating from a nonhalogenated solvent. A range of morphological measurements reveal that gas-blowing suppresses excessive aggregation of nonfullerene acceptors. As a result, gas-blowing treated PM6:BTP-eC9 OSCs obtained a maximum PCE of 19.0%, which is among the highest values of blade-coated OSCs. Moreover, this morphology transformation also drives the photoactive layer toward the thermodynamic equilibrium state, reducing free volume in the photoactive layer and contributing to better device stabilities.

Metal hexacyanoferrates (MHCFs) have emerged as promising cathodes for sodium-ion batteries. However, conventional wet-chemistry-derived MHCFs inevitably contain substantial Fe(CN)₆ vacancies and crystal water, resulting in an undesirable Na-storage performance. Herein, a gel-confined crystallization strategy is developed to prepare highly crystalline MHCFs. In a typical polypyrrole (PPy) gel, the cross-linked network effectively restricts the movement of internal ions through steric hindrance and attractive/repulsive interactions, leading to slow crystal growth and formation of highly crystalline MHCFs. Specifically, iron hexacyanoferrate (FeHCF), with only 1% Fe(CN)₆ vacancy and 2.0 wt% crystal water, has been formed in situ within a PPy gel via this gel-confined crystallization process. The highly crystalline FeHCF coupled with an interconnected PPy framework enables the hybrid cathode to exhibit enhanced activity of low-spin Fe sites, long cycling life, and good rate capability.

Solvent-free (dry-processed) electrodes offer substantial economic and environmental benefits to Li-ion batteries and are manufactured in a way that requires them to withstand tensile loads during roll-to-roll processing. Electrode sheets comprising graphite particles embedded within a polytetrafluoroethylene (PTFE) polymer fibril network were investigated under tension and exhibited viscoelastic behavior: linear loading, plastic deformation, and sheet failure. The degree of PTFE fibrillation during manufacture impacted final sheet properties, and calendering induced fibril alignment and crystallographic texture and macroscopic mechanical anisotropy. Increasing the PTFE fraction by 3.5 wt % led to remarkable improvements in ultimate tensile strength (+900%) and failure strain (+30%). Increasing electrode temperature (>19 °C) delayed sheet failure as PTFE transformed from a triclinic to hexagonal phase, however, higher temperatures (>80 °C) accelerated failure by fibril elongation, pull-out and widespread fibril fracture.

Two-dimensional (2D) ferromagnetic materials integrating multiple functions are promising candidates for building magnetic and electronic nanodevices. Here, we predict a series of stable 2D multifunctional ferromagnetic monolayers VX (X = S, Se, Te) encompassing indirect semiconducting and half-metallic phases with sizable spin gaps. Due to the strong ferromagnetic coupling present in the VX monolayers, the magnetic transition temperatures (Tc) of VS, VSe, and VTe reach 369, 315, and 311 K, respectively. Furthermore, the magnetic and electronic properties of VX monolayers can be sensitively modulated via mechanical strain, while the VS and VSe monolayers further exhibit negative Poisson’s ratios. The VX monolayers thus represent an unusual family of 2D ferromagnetic materials with strong mechano-electromagnetic coupling that may serve as a building block for future multifunctional nanodevices.

Sodium-containing chalcogenides are attractive candidates for use as solid-state electrolytes; however, their ionic conductivities remain a challenge. Simultaneously applying isovalent and aliovalent substitution can enhance ionic conductivity by generating substantial site disorder and high vacancy concentrations. To elucidate the mechanism that facilitates sodium ion conduction, a series of mixed-pnicogen solid solutions were prepared from the parent ternary sulfides Na₃PnS₄ (Pn = P, As, Sb) by high-temperature reactions, including an entropy-driven W-substituted phase, Na_3−δP_0.32As_0.32Sb_0.32W_0.04S₄ (N-PASS-W). N-PASS-W exhibits a very high ionic conductivity of 10 mS cm^–1 and a low activation energy of 0.15 eV. Using PXRD and NMR spectroscopy, an atomic-level model for N-PASS-W was proposed, in which ion hopping occurs over two Na sites within a tetragonal structure (P4̅2₁c). Relationships were also established between the structure and ionic conductivities of the other members to evaluate the influence of crystalline phase, cation size, and site disorder.

LiNiO₂ is regarded as an ideal positive electrode material for Li-ion battery applications, offering a large reversible capacity, >200 mA h g^–1, with a lower cutoff voltage, 4.3 V. The fully charged state, Li_1–xNiO₂ (x ≈ 0.9), is a metastable phase obtained by electrochemical oxidation in Li cells. Due to its instability, atomic-scale imaging of this phase by using scanning transmission electron microscopy (STEM) is particularly challenging, as it readily decomposes under electron beam exposure. In this study, the effect of cryogenic conditions during STEM observation is examined. While as-prepared LiNiO₂ shows strong resistance to beam damage, Li_1–xNiO₂ (x ≈ 0.9) undergoes structural changes under room-temperature beam exposure. In contrast, beam-induced damage is substantially suppressed under cryogenic conditions (−150 °C), enabling successful acquisition of atomic-resolution STEM images. These findings underscore the importance of cryo-STEM techniques for imaging metastable battery materials.

High-performance solid-state electrolytes (SSEs) are crucial for next-generation lithium batteries. However, conventional methods like density functional theory and empirical force fields face challenges in computational cost, scalability, and transferability across diverse systems. Machine learning interatomic potentials (MLIPs) offer a promising alternative by balancing accuracy and efficiency. Nevertheless, their performance and applicability for SSEs remain poorly defined, limiting reliable model selection. In this study, we benchmark 12 MLIPs─including GRACE, DPA, MatterSim, MACE, SevenNet, CHGNet, TensorNet, M3GNet, and ORB─across energies, forces, phonons, electrochemical stability, thermodynamic properties, elastic moduli, and Li⁺ diffusivity. GRACE-2L-OAM, MACE-MPA, MatterSim, DPA-3.1-3M, and SevenNet-MF-ompa show superior accuracy. Using MatterSim, we study Li₃YCl₆ and Li₆PS₅Cl, revealing that ∼40–50% S/Cl anion disorder enhances Li⁺ migration connectivity in Li₆PS₅Cl, while higher Li⁺ content in Li₃Ycl₆ expands conduction channels and reduces energy barriers. These insights highlight the power of MLIP-driven simulations for mechanistic understanding and rational design of high-conductivity SSEs.

Due to the similar kinetic diameters and physicochemical properties of ethylene and ethane, developing highly efficient C₂H₄/C₂H₆ separation membranes remains a huge challenge. In this study, spatio-selective reconfiguration of a Ni-pca-pyz metal–organic framework (MOF) membrane was discovered upon vacuum heat treatment. The progressive migration of the low-boiling-point pyrazine ligands on the coordination unsaturated metal sites in the structure can result in the preferential exposure of the (001) crystal plane, thus the significant increase in C₂H₄ selectivity due to the optimized diffusion path. The Ni-pca-pyz membrane with preferential (001) crystal plane orientation shows highly competitive C₂H₄/C₂H₆ separation performance, with a C₂H₄ permeance of 351.2 GPU and a C₂H₄/C₂H₆ separation factor of 5.6 during mixed-gas permeation, highlighting the promising application of the vacuum heat treatment protocol in structure optimization and performance enhancement of versatile MOF membranes.

Engineering a polymer-based protective layer on a Zn metal surface can alleviate the side reactions for high Zn reversibility, yet the chain entanglement of the polymer may prolong the pathway and hinder the ion transport for poor battery performance. Here, the Debus-Radziszewski reaction was employed to form an imidazolium cation (IM⁺) structure in chitosan for high-performance protective layers. The protective layer for Zn metal with chitosan connected by IM⁺ (ZCIM) owns low entanglement characteristics to facilitate the ion transport channel construction, thus significantly promoting rapid Zn²⁺ migration kinetics. Moreover, the IM⁺ renders charge delocalization, thereby improving the electric field distribution on the Zn surface to accelerate stable Zn²⁺ deposition kinetics. Consequently, the symmetrical Zn battery with ZCIM remains stable at a high depth of discharge of 93.2%, and the Zn/I₂ battery with ZCIM demonstrates a high-capacity retention rate of over 89% at a low N/P ratio of 2.6.