Optimizing the Structure and Electrochemical Properties of Benzoquinone-Embedded COF via Heat Treatment for a High-Energy Organic Cathode.

A benzoquinone-embedded aza-fused covalent organic framework (BQ COF) with the maximum loading of redox-active units per molecule was employed as a cathode for lithium-ion batteries (LIBs) to achieve high energy and power densities. The synthesis was optimized to obtain high crystallinity and improved electrochemical performance. Synthesis at moderate temperature followed by a solid-state reaction was found to be particularly useful for achieving good crystallinity and the activation of the COF. When used as a cathode for LIBs, very high discharge capacities of 513, 365, and 234 mAh g-1 were obtained at 0.1C, 1C, and 10C, respectively, showing a remarkable rate performance. More than 70% of the initial capacity was retained after 1000 cycles when the cathode was investigated for cyclic performance at 2.5C. We demonstrated that a straightforward heat treatment led to enhanced crystallinity, an optimized structure, and favorable morphology, resulting in enhanced electrode kinetics and an improved overall electrochemical behavior. A comparative study was conducted involving an aza-fused COF lacking carbonyl groups (TAB COF) and a small molecule containing phenazine and carbonyl (3BQ), providing useful insights into new material design. A full cell was assembled with graphite as the anode to assess the commercial feasibility of BQ COF, and a discharge capacity of 240 mAh g-1 was obtained at 0.5C. Furthermore, a pouch-type cell with a high discharge capacity and an excellent rate performance was assembled, demonstrating the practical applicability of our designed cathode. Considering the entire mass of the working electrode, a specific energy density of 492 Wh kg-1 and a power density of 492 W kg-1 were achieved at the high current density of 1C, which are comparable to those of commercially available cathodes. These results highlight the promise of organic electrode materials for next-generation lithium-ion batteries. Furthermore, this study provides a systematic approach for simultaneously designing organic materials with high power and energy densities.

Accelerated Skin Wound Healing Using Flexible Photovoltaic-Bioelectrode Electrical Stimulation.

Owing to the complex and long-term treatment of foot wounds due to diabetes and the limited mobility of patients, advanced clinical surgery often uses wearable flexible devices for auxiliary treatment. Therefore, there is an urgent need for self-powered biomedical devices to reduce the extra weight. We have prepared an electrically stimulated MEMS (Micro Electromechanical System) electrode integrated with wearable OPV (Organic photovoltaic). The wearable OPV is constructed of a bio-affinity PET-ITO substrate and a hundred-nanometer organic layer. Under sunlight and near-infrared light irradiation, a voltage and current are supplied to the MEMS electrode to generate an exogenous lateral electric field directed to the center of the wound. The results of in vitro cell experiments and diabetic skin-relieving biological experiments showed the proliferation of skin fibroblasts and the expression of transforming growth factors increased, and the skin wounds of diabetic mouse healed faster. Our research provides new insights for the clinical treatment of diabetes.

The first robotic transanal minimally invasive surgery in Ireland: a case-based review.

Transanal minimally invasive surgery (TAMIS) has gained worldwide acceptance as a means of local excision of early rectal cancers and benign rectal lesions. However, it is technically challenging due to the limitations of rigid laparoscopic instruments in the narrow rectal lumen. Robotic platforms offer improved ergonomics that are valuable in operative fields with limited space. Robotic TAMIS represents an exciting new development that may be more versatile than traditional TAMIS. In this review, we describe the first case of robotic TAMIS performed in our country and a review of current literature on the technique.

Sulfur Compensation: A Promising Strategy against Capacity Decay in Li-S Batteries.

Drastic capacity decay as a result of active sulfur loss caused by the severe shuttle effect of dissolved polysulfides is the main obstacle in the commercial application of Li-S batteries. Various methods have been developed to suppress the active sulfur loss, but the results are far from ideal. Herein, we propose a facile sulfur compensation strategy to improve the cyclic stability of Li-S batteries. The strategy is to compensate sulfur to the cathode by chemical reactions between additional sulfur and lithium polysulfides diffusing away from the cathode. The compensatory sulfur can effectively mitigate the loss of active sulfur in the cathode side caused by the shuttle effect and thus maintain the high capacity of the battery during charging and discharging for long life cycle assessments. Using this strategy, the specific capacity of the assembled Li-S batteries was maintained at >700 mA h g-1 for more than 500 cycles at 1 C and >1000 mA h g-1 for ∼100 cycles at 0.1 C, while the capacity of control batteries rapidly decreased to <200 mA h g-1 under the same conditions.

Investigating the Electrocatalysis of a Ti3C2/Carbon Hybrid in Polysulfide Conversion of Lithium-Sulfur Batteries.

Despite the fact that lithium-sulfur batteries are regarded as promising next-generation rechargeable battery systems owning to high theoretical specific capacity (1675 mA h g-1) and energy density (2600 W h kg-1), several issues such as poor electrical conductivity, sluggish redox kinetics, and severe "shuttle effect" in electrodes still hinder their practical application. MXenes, novel two-dimensional materials with high conductivity, regulable interlayer spacing, and abundant functional groups, are widely applied in energy storage and conversion fields. In this work, a Ti3C2/carbon hybrid with expanded interlayer spacing is synthesized by one-step heat treatment in molten potassium hydroxide. The subsequent experiments indicate that the as-prepared Ti3C2/carbon hybrid can effectively regulate polysulfide redox conversion and has strong chemisorption interaction to polysulfides. Consequently, the Ti3C2/carbon-based sulfur cathode boosts the performance in working lithium-sulfur batteries, in terms of an ultrahigh initial discharge capacity (1668 mA h g-1 at 0.1 C), an excellent rate performance (520 mA h g-1 at 5 C), and an outstanding capacity retention of 530 mA h g-1 after 500 cycles at 1 C with a low capacity fade rate of 0.05% per cycle and stable Coulombic efficiency (nearly 99%). The above results indicate that this composite with high catalytic activity is a potential host material for further high-performance lithium-sulfur batteries.

Nanowire Array-Coated Flexible Substrate to Accommodate Lithium Plating for Stable Lithium-Metal Anodes and Flexible Lithium-Organic Batteries.

Although lithium metal is an ideal anode with high theoretical capacity, Li dendrite formation and volume change have limited its application. We report a vertical polyaniline nanowire-coated carbon nanotube (CNT/PANI) composite flexible electrode on which Li could be homogeneously deposited to obtain a CNT/PANI@Li anode. In the composite, CNT/PANI acted as a host matrix with well-distributed Li ion flux attributed to high electroactive surface area, thereby effectively suppressing the Li dendrite. Compared with the pure CNT electrode, the CNT/PANI electrode presented low overpotential and stable long-term cycling with much less fluctuant stripping/plating profiles. The potential application of CNT/PANI@Li in all-flexible full cells was demonstrated by combining flexible organic poly(2,5-dihydroxyl-1,4-benzoquinonyl sulfide)/carbon nanotube (PDHBQS/CNT) composite films, in which the cathode achieves an eminent performance of 120 mA h g-1 at 50 mA g-1. Furthermore, pouch batteries with good flexibility were tested successfully, which demonstrated a promising future for all-flexible and high-performance Li-metal batteries.

Recent Progress in Polymeric Carbonyl-Based Electrode Materials for Lithium and Sodium Ion Batteries.

Advancement in mobile electronics is driving progress in lithium ion batteries. Recently, organic electrode materials have emerged as promising candidates for lithium ion batteries due to their high theoretical capacity, ease of synthesis, versatility of structure, and abundance. Polymerization is a strategy used to overcome the issues associated with small organic molecules for charge storage application. The focus of this review is on the most recent progress in the field of polymeric carbonyl materials for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). Advantages of organic electrode materials, device architecture, and charge storage mechanism are discussed. Challenges associated with carbonyl-based electrodes and some recent solutions are outlined. Later, a comparison of theoretical capacity, practical capacity, and cyclic life are presented for different carbonyl systems. Capacity-fading phenomena and structural degradation during charging are discussed where necessary. Some key parameters for the design of flexible batteries are highlighted and an overview of some recent contributions of our group in this field are reported. Finally, some future prospects for researchers in this field are outlined.

A carbon foam-supported high sulfur loading composite as a self-supported cathode for flexible lithium-sulfur batteries.

A binder-free, self-supported, flexible cathode is explored for application in flexible lithium-sulfur (Li-S) batteries. The cathode is constructed using nitrogen (N)-doped carbon foam/carbon nanotubes (CNTs) as the scaffold and filled with poly(3,4-ethylenedioxythiophene) (PEDOT)-encapsulated sulfur nanoparticles as the active material. The dense CNTs coated on the skeleton of the 3D N-doped foam enhance flexibility, and the highly conductive CNTs are crossed and twined together to create an interconnected skeleton for rapid electron transport. The conductive PEDOT shell of sulfur nanoparticles and the N-doping of the carbon foams restrain the dissolution of polysulfides through the enhanced chemisorption of lithium polysulfides. The best cathode with a sulfur loading of 2.6 mg cm-2 has an eminent capacity of 1395 mA h g-1 during the initial cycle at 0.1 C. Furthermore, freestanding cathodes are assembled into flexible Li-S batteries, which demonstrate significant achievement at various bending angles. The capacity fading rate is 0.16% per cycle at 30° after 120 cycles. Its high sulfur loading, high capacitance, and good flexibility make this cathode material a promising candidate for potential application in flexible electronics.

Macroscopic helical chirality and self-motion of hierarchical self-assemblies induced by enantiomeric small molecules.

Transfer of molecular chirality to supramolecular chirality at nanoscale and microscale by chemical self-assembly has been studied intensively for years. However, how such molecular chirality further transfers to the macroscale along the same path remains elusive. Here we reveal how the chirality from molecular level transfers to macroscopic level via self-assembly. We assemble a macrostripe using enantiomeric camphorsulfonic acid (CSA)-doped polyaniline with hierarchical order. The stripe can twist into a single-handed helical ribbon via helical self-motion. A multi-scale chemo-mechanical model is used to elucidate the mechanism underlying its chirality transfer and induction. The molecular origin of this macroscopic helical chirality is verified. Results provide a comprehensive understanding of hierarchical chirality transfer and helical motion in self-assembled materials and even their natural analogues. The stripe exhibits disparate actuation behaviour under stimuli of enantiomeric amines and integrating such chiral perception with helical self-motion may motivate chiral biomimetic studies of smart materials.

A Carbonyl Compound-Based Flexible Cathode with Superior Rate Performance and Cyclic Stability for Flexible Lithium-Ion Batteries.

A sulfur-linked carbonyl-based poly(2,5-dihydroxyl-1,4-benzoquinonyl sulfide) (PDHBQS) compound is synthesized and used as cathode material for lithium-ion batteries (LIBs). Flexible binder-free composite cathode with single-wall carbon nanotubes (PDHBQS-SWCNTs) is then fabricated through vacuum filtration method with SWCNTs. Electrochemical measurements show that PDHBQS-SWCNTs cathode can deliver a discharge capacity of 182 mA h g-1 (0.9 mA h cm-2 ) at a current rate of 50 mA g-1 and a potential window of 1.5 V-3.5 V. The cathode delivers a capacity of 75 mA h g-1 (0.47 mA h cm-2 ) at 5000 mA g-1 , which confirms its good rate performance at high current density. PDHBQS-SWCNTs flexible cathode retains 89% of its initial capacity at 250 mA g-1 after 500 charge-discharge cycles. Furthermore, large-area (28 cm2 ) flexible batteries based on PDHBQS-SWCNTs cathode and lithium foils anode are also assembled. The flexible battery shows good electrochemical activities with continuous bending, which retains 88% of its initial discharge capacity after 2000 bending cycles. The significant capacity, high rate performance, superior cyclic performance, and good flexibility make this material a promising candidate for a future application of flexible LIBs.