Intrinsic glassy-metallic transport in an amorphous coordination polymer.

Conducting organic materials, such as doped organic polymers1, molecular conductors2,3 and emerging coordination polymers4, underpin technologies ranging from displays to flexible electronics5. Realizing high electrical conductivity in traditionally insulating organic materials necessitates tuning their electronic structure through chemical doping6. Furthermore, even organic materials that are intrinsically conductive, such as single-component molecular conductors7,8, require crystallinity for metallic behaviour. However, conducting polymers are often amorphous to aid durability and processability9. Using molecular design to produce high conductivity in undoped amorphous materials would enable tunable and robust conductivity in many applications10, but there are no intrinsically conducting organic materials that maintain high conductivity when disordered. Here we report an amorphous coordination polymer, Ni tetrathiafulvalene tetrathiolate, which displays markedly high electronic conductivity (up to 1,200 S cm-1) and intrinsic glassy-metallic behaviour. Theory shows that these properties are enabled by molecular overlap that is robust to structural perturbations. This unusual set of features results in high conductivity that is stable to humid air for weeks, pH 0-14 and temperatures up to 140 °C. These findings demonstrate that molecular design can enable metallic conductivity even in heavily disordered materials, raising fundamental questions about how metallic transport can exist without periodic structure and indicating exciting new applications for these materials.

Presynthetic Redox Gated Metal-to-Insulator Transition and Photothermoelectric Properties in Nickel Tetrathiafulvalene-Tetrathiolate Coordination Polymers.

Photothermoelectric (PTE) materials are promising candidates for solar energy harvesting and photodetection applications, especially for near-infrared (NIR) wavelengths. Although the processability and tunability of organic materials are highly advantageous, examples of organic PTE materials are comparatively rare and their PTE performance is typically limited by poor photothermal (PT) conversion. Here, we report the use of redox-active Sn complexes of tetrathiafulvalene-tetrathiolate (TTFtt) as transmetalating agents for the synthesis of presynthetically redox tuned NiTTFtt materials. Unlike the neutral material NiTTFtt, which exhibits n-type glassy-metallic conductivity, the reduced materials Li1.2Ni0.4[NiTTFtt] and [Li(THF)1.5]1.2Ni0.4[NiTTFtt] (THF = tetrahydrofuran) display physical characteristics more consistent with p-type semiconductors. The broad spectral absorption and electrically conducting nature of these TTFtt-based materials enable highly efficient NIR-thermal conversion and good PTE performance. Furthermore, in contrast to conventional PTE composites, these NiTTFtt coordination polymers are notable as single-component PTE materials. The presynthetically tuned metal-to-insulator transition in these NiTTFtt systems directly modulates their PT and PTE properties.

Linker Redox Mediated Control of Morphology and Properties in Semiconducting Iron-Semiquinoid Coordination Polymers.

The emergence of conductive 2D and less commonly 3D coordination polymers (CPs) and metal-organic frameworks (MOFs) promises novel applications in many fields. However, the synthetic parameters for these electronically complex materials are not thoroughly understood. Here we report a new 3D semiconducting CP Fe5 (C6 O6 )3 , which is a fusion of 2D Fe-semiquinoid materials and 3D cubic Fex (C6 O6 )y materials, by using a different initial redox-state of the C6 O6 linker. The material displays high electrical conductivity (0.02 S cm-1 ), broad electronic transitions, promising thermoelectric behavior (S2 σ=7.0×10-9  W m-1 K-2 ), and strong antiferromagnetic interactions at room temperature. This material illustrates how controlling the oxidation states of redox-active components in conducting CPs/MOFs can be a "pre-synthetic" strategy to carefully tune material topologies and properties in contrast to more commonly encountered post-synthetic modifications.

Dry-processed technology for flexible and high-performance FeS2-based all-solid-state lithium batteries at low stack pressure.

All-solid-state lithium batteries (ASSLBs) are considered promising energy storage systems due to their high energy density and inherent safety. However, scalable fabrication of ASSLBs based on transition metal sulfide cathodes through the conventional powder cold-pressing method with ultrahigh stacking pressure remains challenging. This article elucidates a dry process methodology for preparing flexible and high-performance FeS2-based ASSLBs under low stack pressure by utilizing polytetrafluoroethylene (PTFE) binder. In this design, fibrous PTFE interweaves Li6PS5Cl particles and FeS2 cathode components, forming flexible electrolyte and composite cathode membranes. Beneficial to the robust adhesion, the composite cathode and Li6PS5Cl membranes are tightly compacted under a low stacking pressure of 100 MPa which is a fifth of the conventional pressure. Moreover, the electrode/electrolyte interface can sustain adequate contact throughout electrochemical cycling. As expected, the FeS2-based ASSLBs exhibit outstanding rate performance and cyclic stability, contributing a reversible discharged capacity of 370.7 mAh g-1 at 0.3C after 200 cycles. More importantly, the meticulous dQ/dV analysis reveals that the three-dimensional PTFE binder effectively binds the discharge products with sluggish kinetics (Li2S and Fe) to the ion-electron conductive network in the composite cathode, thereby preventing the electrochemical inactivation of products and enhancing electrochemical performance. Furthermore, FeS2-based pouch-type cells are fabricated, demonstrating the potential of PTFE-based dry-process technology to scale up ASSLBs from laboratory-scale mold cells to factory-scale pouch cells. This feasible dry-processed technology provides valuable insights to advance the practical applications of ASSLBs.

In-situ cross-linked multifunctional polymer electrolyte buffer layers for high-performance garnet solid-state lithium metal batteries.

The garnet Li6.75La3Zr1.75Ta0.25O12 (LLZTO) is one of the most promising electrolytes for commercial application since of its high ionic conductivity and good stability to Li. Nevertheless, the poor electrolyte/electrode interface contact enlarges the interface impedance of all-solid-state battery (ASSB). Herein, a multifunctional polymer electrolyte (MPE) interface buffer layers are formed on both sides of LLZTO surface through an in-situ crosslinking strategy to improve the interface contact with electrodes, which can facilitate uniform Li+ deposition/exfoliation and inhibit the growth of lithium dendrites as evidenced by the reduced interface impedance (103.4 Ω cm2), the increased critical current density (CDD, 1.2 mA cm-2) and 950 h stable cycle of Li symmetric cells at 0.7 mA cm-2, 0.7 mA h cm-2. Besides, the MPE layer can reduce the magnitude of electric field at the interface and widen the electrochemical window (0∼5.2 V). The stable interface of the LLZTO@MPE/cathode enables the full cells matching with the LiFePO4 (LFP) and LiNi0.5Co0.2Mn0.3O2 (NCM523) cathodes to deliver superior electrochemical performances. Specifically, the Li/MPE@LLZTO@MPE/LFP delivers a capacity retention rate of 87% after 200 cycles at 1 C. When it's matched with the NCM523 cathode, a capacity retention rate of 98% is retained after 100 cycles at 1 C. This work provides an effective and simple way to build good-interface-contact and long-lifespan garnet solid-state lithium metal batteries (SSLMBs).

A novel magnetic metal-organic framework absorbent for rapid detection of aflatoxins B1B2G1G2 in rice by HPLC-MS/MS.

In this study, a core-shell-structured magnetic metal-organic framework (MMOF) composite material (Fe3O4@UiO-66-NH2) was synthesized by the solvothermal method. It was employed as a new absorbent in combination with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) for the simultaneous detection of four aflatoxins (AFs) in rice. This method could shorten the pre-processing time by exploiting the advantageous characteristics of magnetic cores. The impurity was removed quickly. The effects of extraction solution, extraction time, adsorbent types, and amount of adsorbent on the extraction rate of target compounds were optimized. Under optimized conditions, AFs were validated and showed a good linear relationship within the 0.375-20 µg kg-1 concentration range (r2 > 0.9992). The limit of detection (LOD) was 0.0188-0.1250 µg kg-1 and the limit of quantification (LOQ) was 0.0375-0.3750 µg kg-1. At three spiking levels (0.375, 2, and 10 µg kg-1), the average recovery values for the four AFs ranged from 85.1% to 111.0%. The relative standard deviation ranged from 3.4% to 7.7%. The new method proved to be simple, fast, efficient, and suitable for the determination of AFs in rice samples.