MOF-Based Solid-State Proton Conductors Obtained by Intertwining Protic Ionic Liquid Polymers with MIL-101

Solid-state proton conductors based on the use of metal–organic framework (MOF) materials as proton exchange membranes are being investigated as alternatives to the current state of the art. This study reports a new family of proton conductors based on MIL-101 and protic ionic liquid polymers (PILPs) containing different anions. By first installing protic ionic liquid (PIL) monomers inside the hierarchical pores of a highly stable MOF, MIL-101, then carrying out polymerization in situ, a series of PILP@MIL-101 composites was synthesized. The resulting PILP@MIL-101 composites not only maintain the nanoporous cavities and water stability of MIL-101, but the intertwined PILPs provide a number of opportunities for much-improved proton transport compared to MIL-101. The PILP@MIL-101 composite with HSO₄⁻ anions shows superprotonic conductivity (6.3 × 10⁻² S cm⁻¹) at 85 °C and 98% relative humidity. The mechanism of proton conduction is proposed. In addition, the structures of the PIL monomers were determined by single crystal X-ray analysis, which reveals many strong hydrogen bonding interactions with O/N H···O distances below 2.6 Å.     

Wide-Temperature,Long-Cycling,and High-Loading Pyrite All-Solid-State Batteries Enabled by Argyrodite Thioarsenate Superionic Conductor

Rechargeable FeS₂ battery has been regarded as a promising energy storage device, due to its potentially high energy density and ultralow cost. However, the short lifespan associated with the shuttle effect of polysulfides, large volume change, agglomeration of Fe⁰ nanoparticles, narrow operating temperature range, and sluggish reaction kinetics, greatly impede the application of rechargeable FeS₂ lithium-ion batteries. Herein, an all-solid-state battery (ASSB) coupling commercialized FeS₂ is proposed with a novel superionic conductor Li_6.8Si_0.8As_0.2S₅I (LASI-80Si) to overcome these challenges. The shuttle effect of polysulfides and volume change of FeS₂ are suppressed or completely eliminated in ASSB, due to solid-solid conversion of Li₂S/S and large stacking pressure, respectively. Furthermore, the operating temperature range (−60–60 °C) is significantly expanded by the ultra-high and temperature-insensitive ionic conductivity of LASI-80Si (E_a = 0.20 eV), along with the superior FeS₂/LASI-80Si interface stability. Thanks to the extra Li⁺ provided by Li₂S and LiI functional phases, the “bridge” effect of LiI on facile interfacial Li-ion conduction, and the enhanced reaction kinetics of LASI-80Si (${\sigma }_{L{i}^{+}}=$ 10.4 mS cm⁻¹), ASSBs with LASI-80Si deliver long cycle life (244 cycles at 0.1 C and 600 cycles at 1 C), superior rate capability (20 C), high areal mass loading (13.37 mg cm⁻²), and ultrahigh areal capacity (9.05 mAh cm⁻²). These inspiring results demonstrate the enormous potential of LASI-80Si and FeS₂ combination for practical application of wide-temperature and large-capacity ASSBs.     

Overcoming Obstacles in Zn-Ion Batteries Development: Application of Conductive Redox-Active Polypyrrole/Tiron Anolyte Interphase

This study is focused on overcoming obstacles in the implementation of metallic Zn for zinc-ion batteries. The major limiting factors of Zn anodes include dendrite growth, hydrogen evolution, and by-product formation. Herein, the challenges are addressed by the application of a redox-active electrode-electrolyte interphase. Cationic polypyrrole(PPy)/anionic Tiron anolyte is formulated as the mixed conducting interphase to push the limits of zinc-based energy storage. The doping/de-doping behavior of PPy stimulates the surface adsorption/desorption of Tiron attributed to the ion-induced nucleation. Testing results show that PPy as a passivating corrosive-resistant layer improves the interfacial stability of Zn metal; while releasing the redox-active anolyte boosts the charge transfer of cells by the phenol-quinone transformations. The Zn//Zn cells demonstrate an improved life from 50 to 2500 cycles with a reduced overpotential at 2 mA cm⁻² and 1 mAh cm⁻². In situ UV–vis spectroscopic measurements, combined with density functional theory calculations, address the redox mechanisms of PPy/Tiron anolyte. The testing of α-MnO₂//Zn cells shows that the PPy/Tiron anolyte exhibits enhanced capacity and rate performance due to the pseudocapacitive effects. This study unveils a conceptually new approach based on the modification of conducting polymer with redox-active dopants toward the fabrication of high-performance Zn-anolyte batteries.     

Integration of an Axially Continuous Graphene with Functional Metals for High-Temperature Electrical Conductors

Demands for effective high-temperature electrical conductors continue to increase with the rapid adoption of electric vehicles. However, the use of conventional copper-based conductors is limited to relatively low temperatures due to their poor oxidation resistance and microstructural instability. Here, a highly conductive and thermally stable nickel-graphene-copper (NiGCu) wire that combines the advantages of graphene and its metallic components is developed. The NiGCu wire consists of a conductive copper core, an oxidation-resistant nickel shell, and axially continuous graphene embedded between them. The experiments on 10–80 µm diameter NiGCu wires demonstrate substantial enhancements in electrical properties and thermal stability across a variety of metrics. For instance, the smallest NiGCu wires have a 61.2% higher current density limit, 307.6% higher conductivity, and an order of magnitude smaller change in resistivity compared to conventional Ni-coated Cu counterparts after annealing at 650 °C. By performing both innovative experiments and simulations using different sizes of NiGCu wires, the diffusion coefficients of metals are quantified, for the first time to the best knowledge, through continuous graphene. These results indicate that the dramatic improvement in thermo-electrical properties is enabled by the embedded graphene layer which reduces Ni Cu interdiffusion by ≈10⁴ times at 550 °C and 650 °C.     

High Cathode Loading and Low-Temperature Operating Garnet-Based All-Solid-State Lithium Batteries – Material/Process/Architecture Optimization and Understanding of Cell Failure

All-solid-state lithium batteries (ASSLBs) are prepared using garnet-type solid electrolytes by quick liquid phase sintering (Q-LPS) without applying high pressure during the sintering. The cathode layers are quickly sintered with a heating rate of 50–100 K min⁻¹ and a dwell time of 10 min. The battery performance is dramatically improved by simultaneously optimizing materials, processes, and architectures, and the initial discharge capacity of the cell with a LiCoO₂-loading of 8.1 mg reaches 1 mAh cm⁻² and 130 mAh g⁻¹ at 25 °C. The all-solid-state cell exhibits capacity at a reduced temperature (10 °C) or a relatively high rate (0.1 C) compared to the previous reports. The Q-LPS would be suitable for large-scale manufacturing of ASSLBs. The multiphysics analyses indicate that the internal stress reaches 1 GPa during charge/discharge, which would induce several mechanical failures of the cells: broken electron networks, broken ion networks, separation of interfaces, and delamination of layers. The experimental results also support these failures.     

High Proton Conductivity in β-Ba2ScAlO5 Enabled by Octahedral and Intrinsically Oxygen-Deficient Layers

Proton conductors are promising materials for clean energy, but most available materials exhibit sufficient conductivity only when chemically substituted to create oxygen vacancies, which often leads to difficulty in sample preparation and chemical instability. Recently, proton conductors based on hexagonal perovskite-related oxides have been attracting attention as they exhibit high proton conductivity even without the chemical substitutions. However, their conduction mechanism has been elusive so far. Herein, taking three types of oxides with different stacking patterns of oxygen-deficient layers (β-Ba₂ScAlO₅, α-Ba₂Sc_0.83Al_1.17O₅, and BaAl₂O₄) as examples, the roles of close-packed double-octahedral layers and oxygen-deficient layers in proton conduction are shown. It is found that “undoped” β-Ba₂ScAlO₅, which adopts a structure having alternating double-octahedral layer and double-tetrahedral layer with intrinsically oxygen-deficient hexagonal BaO (h') layer, shows high proton conductivity (≈10⁻³ S cm⁻¹ above 300 °C), comparable to representative proton conductors. In contrast, the structurally related oxides α-Ba₂Sc_0.83Al_1.17O₅ and BaAl₂O₄ exhibit lower conductivity. Ab initio molecular dynamics simulations revealed that protons in β-Ba₂ScAlO₅ migrate through the double-octahedral layer, while the h′ layer plays the role of a “proton reservoir” that supplies proton carriers to the proton-conducting double-octahedral layers. The distinct roles of the two layers in proton conduction provide a strategy for developing high-performance proton conductors.