Comparison of the Ionic Conductivity Properties of Microporous and Mesoporous MOFs Infiltrated with a Na-Ion Containing IL Mixture

IL@MOF (IL: ionic liquid; MOF: metal-organic framework) materials have been proposed as a candidate for solid-state electrolytes, combining the inherent non-flammability and high thermal and chemical stability of the ionic liquid with the host-guest interactions of the MOF. In this work, we compare the structure and ionic conductivity of a sodium ion containing IL@MOF composite formed from a microcrystalline powder of the zeolitic imidazolate framework (ZIF), ZIF-8 with a hierarchically porous sample of ZIF-8 containing both micro- and mesopores from a sol-gel synthesis. Although the crystallographic structures were shown to be the same by X-ray diffraction, significant differences in particle size, packing and morphology were identified by electron microscopy techniques which highlight the origins of the hierarchical porosity. After incorporation of Na0.1EMIM0.9TFSI (abbreviated to NaIL; EMIM = 1-ethyl-3-methylimidazolium; TFSI = bis(trifluoromethylsulfonyl)imide), the hierarchically porous composite exhibited a 40 % greater filling capacity than the purely microporous sample which was confirmed by elemental analysis and digestive proton NMR. Finally, the ionic conductivity properties of the composite materials were probed by electrochemical impedance spectroscopy. The results showed that despite the 40 % increased loading of NaIL in the NaIL@ZIF-8micro sample, the ionic conductivities at 25 °C were 8.4x10-6 and 1.6x10-5 S cm-1 for NaIL@ZIF-8meso and NaIL@ZIF-8micro respectively. These results exemplify the importance of the long range, continuous ion pathways contributed by the microcrystalline pores, as well as the detrimental effect of discontinuous and tortuous mesoporous pathways which show a limited contribution to the overall ionic conductivity. <br /

Short-Range Ordering in Battery Electrode, the ‘Cation-Disordered’ Rocksalt Li1.25Nb0.25Mn0.5O2

We show the occurrence of local cation ordering in Li-ion battery material Li1.25Nb0.25Mn0.5O2, previously thought to be disordered. We deduce this ordering from X-ray diffraction, and test it against neutron diffraction & PDF, magnetic susceptibility and solid state NMR evidence. We identify the nature of the ordering as having a local structure related to that of gamma-LiFeO2, determine the correlation length of such ordering, and demonstrate its significant consequences for the material\u27s electrochemistry

Sodium Ion Conductivity in Superionic IL-Impregnated Metal-Organic Frameworks: Enhancing Stability Through Structural Disorder

Metal—organic frameworks (MOFs) are intriguing host materials in composite electrolytes due to their ability for tailoring host-guest interactions by chemical tuning of the MOF backbone. Here, we introduce particularly high sodium ion conductivity into the zeolitic imidazolate framework ZIF-8 by impregnation with the sodium-salt-containing ionic liquid (IL) (Na0.1¬EMIM0.9)TFSI. We demonstrate an ionic conductivity exceeding 2×10-4 S ⋅cm-1 at room temperature, with an activation energy as low as 0.26 eV, i.e., the highest reported performance for room temperature Na+-related ion conduction in MOF-based composite electrolytes to date. Partial amorphization of the ZIF-backbone by ball-milling results in significant enhancement of the composite stability, reflecting in persistent and stable ionic conductivity during exposure to ambient air over up to 20 days. While the introduction of network disorder decelerates IL exudation and interactions with ambient contaminants, the ion conductivity is only marginally affected, decreasing linearly with decreasing crystallinity but still maintaining superionic behavior. This highlights the general importance of 3D networks of interconnected pores for efficient ion conduction in MOF/IL blends, whereas pore symmetry is a presumably less stringent condition.</p

Magnetic and Magnetocaloric Properties of the A 2 LnSbO 6 Lanthanide Oxides on the Frustrated fcc Lattice

Frustrated lanthanide oxides are promising candidates for cryogen-free magnetic refrigeration due to their suppressed ordering temperatures and high magnetic moments. While much attention has been paid to the garnet and pyrochlore lattices, the magnetocaloric effect in frustrated face-centered cubic (fcc) lattices remains relatively unexplored. We previously showed that the frustrated fcc double perovskite Ba2GdSbO6 is a top-performing magnetocaloric material (per mol Gd) because of its small nearest-neighbor interaction between spins. Here we investigate different tuning parameters to maximize the magnetocaloric effect in the family of fcc lanthanide oxides, A2LnSbO6 (A = {Ba2+, Sr2+} and Ln = {Nd3+, Tb3+, Gd3+, Ho3+, Dy3+, Er3+}), including chemical pressure via the A site cation and the magnetic ground state via the lanthanide ion. Bulk magnetic measurements indicate a possible trend between magnetic short-range fluctuations and the field-temperature phase space of the magnetocaloric effect, determined by whether an ion is a Kramers or a non-Kramers ion. We report for the first time on the synthesis and magnetic characterization of the Ca2LnSbO6 series with tunable site disorder that can be used to control the deviations from Curie–Weiss behavior. Taken together, these results suggest fcc lanthanide oxides as tunable systems for magnetocaloric design

Tunable Near-Infrared Luminescence in Tin Halide Perovskite Devices

Infrared emitters are reasonably rare in solution-processed materials. Recently, research into hybrid organo-lead halide perovskite, originally popular in photovoltaics,− has gained traction in light-emitting diodes (LED) due to their low-cost solution processing and good performance.− The lead-based electroluminescent materials show strong colorful emission in the visible region, but lack emissive variants further in the infrared. The concerns with the toxicity of lead may, additionally, limit their wide-scale applications. Here, we demonstrate tunable near-infrared electroluminescence from a lead-free organo-tin halide perovskite, using an ITO/PEDOT:PSS/CH₃NH₃Sn­(Br_1–<i>x</i>I_<i>x</i>)₃/F8/Ca/Ag device architecture. In our tin iodide (CH₃NH₃SnI₃) LEDs, we achieved a 945 nm near-infrared emission with a radiance of 3.4 W sr^–1 m^–2 and a maximum external quantum efficiency of 0.72%, comparable with earlier lead-based devices. Increasing the bromide content in these tin perovskite devices widens the semiconductor bandgap and leads to shorter wavelength emissions, tunable down to 667 nm. These near-infrared LEDs could find useful applications in a range of optical communication, sensing and medical device applications

Low Temperature Epitaxial LiMn₂O₄ Cathodes Enabled by NiCo₂O₄ Current Collector for High-Performance Microbatteries

Epitaxial cathodes in lithium-ion microbatteries are ideal model systems to understand mass and charge transfer across interfaces, plus interphase degradation processes during cycling. Importantly, if grown at <450 °C, they also offer potential for complementary metal–oxide–semiconductor (CMOS) compatible microbatteries for the Internet of Things, flexible electronics, and MedTech devices. Currently, prominent epitaxial cathodes are grown at high temperatures (>600 °C), which imposes both manufacturing and scale-up challenges. Herein, we report structural and electrochemical studies of epitaxial LiMn2O4 (LMO) thin films grown on a new current collector material, NiCo2O4 (NCO). We achieve this at the low temperature of 360 °C, ∼200 °C lower than existing current collectors SrRuO3 and LaNiO3. Our films achieve a discharge capacity of >100 mAh g–1 for ∼6000 cycles with distinct LMO redox signatures, demonstrating long-term electrochemical stability of our NCO current collector. Hence, we show a route toward high-performance microbatteries for a range of miniaturized electronic devices

Research data supporting "Synthesis and Optical Properties of Lead-Free Cesium Tin Halide Perovskite Nanocrystals"

The uploaded data is the basis for all figures presented in the manuscript and the Supporting InformationThis research data supports “Synthesis and Optical Properties of Lead-Free Cesium Tin Halide Perovskite Nanocrystals” which has been published in “Journal of the American Chemical Soceity”.This work was supported by the EPSRC [grant numbers EP/261 M005143/1, EP/G060738/1 and EP/G037221/1], Royal Society, Winton Program for the Physics of Sustainability and Gates Cambridge Trust

Mg_<i>x</i>Mn_2–<i>x</i>B₂O₅ Pyroborates (2/3 ≤ <i>x</i> ≤ 4/3): High Capacity and High Rate Cathodes for Li-Ion Batteries

MgMnB₂O₅, Mg_2/3Mn_4/3B₂O₅, and Mg_4/3Mn_2/3B₂O₅ pyroborates have been prepared via a ceramic method. When charging MgMnB₂O₅ vs Li, all of the Mg²⁺ can be removed, and with subsequent cycles, 1.4 Li ions, corresponding to a capacity of 250 mAhg^–1, can be reversibly intercalated. This is achieved at a C/25 rate with 99.6% Coulombic efficiency. Significant capacity is retained at high rates with 97 mAhg^–1 at a rate of 2C. Continuous cycling at moderate rates gradually improves performance leading to insertion of 1.8 Li, 314 mAhg^–1 with a specific energy of 802 Whkg^–1, after 1000 cycles at C/5. Ex situ X-ray and neutron diffraction demonstrate the retention of the pyroborate structure on cycling vs Li and a small volume change (1%) between the fully lithiated and delithiated structures. Mg_2/3Mn_4/3B₂O₅ and Mg_4/3Mn_2/3B₂O₅ are also shown to reversibly intercalate Li at 17.8 and 188.6 mAhg^–1, respectively, with Mn ions likely blocking Mg/Li transport in the Mg_2/3Mn_4/3B₂O₅ material. The electrochemical ion-exchange of polyanion materials with labile Mg ions could prove to be a route to high energy density Li-ion cathodes

CSD 2128596 - 2128600: Experimental Crystal Structure Determination

Related Article: Charlotte Pughe, Otto H. J. Mustonen, Alexandra S. Gibbs, Martin Etter, Cheng Liu, Siân E. Dutton, Aidan Friskney, Neil C. Hyatt, Gavin B. G. Stenning, Heather M. Mutch, Fiona C. Coomer, Edmund J. Cussen|2022|Inorg.Chem.|||doi:10.1021/acs.inorgchem.1c0365