M-N-C single-atom catalysts (SACs) have emerged as a potential substitute for the costly platinum-group catalysts in oxygen reduction reaction (ORR). However, several critical aspects of M-N-C SACs in ORR remain poorly understood, including their pH-dependent activity, selectivity for 2- or 4-electron transfer pathways, and the identification of the rate-determining steps. Herein, analyzing >100 M-N-C structures and >2000 sets of energetics, we unveil a pH-dependent evolution in ORR activity volcanos from a single-peak in alkaline media to a double-peak in acids. We found that this pH-dependent behavior in M-N-C catalysts fundamentally stems from their moderate dipole moments and polarizability for O* and HOO* adsorbates, as well as unique scaling relations among ORR adsorbates. To validate our theoretical discovery, we synthesized a series of molecular M-N-C catalysts, each characterized by well-defined atomic coordination environments. Impressively, the experiments matched our theoretical predictions on kinetic current, Tafel slope, and turnover frequency in both acidic and alkaline environments. These new insights also refine the famous Sabatier principle by emphasizing the need to avoid an "acid trap" while designing M-N-C catalysts for ORR or any other pH-dependent electrochemical applications.
Ternary high-nickel oxide exhibits a relatively high working voltage compared with traditional lithium battery cathodes (LiFePO4, etc.). Consequently, it has been widely studied in recent years and is at the forefront of research on positive electrodes for power batteries. To achieve higher reversible capacity, it is often necessary to increase the battery operating voltage. However, there are many drawbacks to this method, such as surface cracking of the working electrode and serious side reactions with the electrolyte. The novel dual-additive combination in this work has the potential to significantly address the aforementioned issues. A composite polymer cathode–electrolyte interface (CEI) film is formed on the surface of the cathode due to two aromatic compound additives preoxidation. The stable CEI film not only improves the stability of the electrode but also suppresses solvent and hydrofluoric acid (HF) to effectively inhibit the side reaction on the cathode surface. Furthermore, these two additives can be readily reduced at the anode to form a solid electrolyte interface (SEI) membrane containing rich LiN&LiF, which effectively suppresses the formation of lithium dendrites. The battery capacity retention could be up to nearly 83% on the dual-additive electrolyte compared to the baseline electrolyte after 300 cycles. This work may provide more possibilities for future research on high-voltage lithium batteries.
To evaluate the cyclic fatigue resistance and the force generated by OneShape files during preparation of simulated curved canals.Six OneShape files (the test) and six ProTaper F2 files (the control) were subject to the bending ability test. Another thirty files of each type were used to prepare artificial canals (n = 60), which were divided into 3 groups according to respective curvatures of the canals (30°, 60°, and 90°). The numbers of cycles to fatigue (NCF) as well as the positive and negative forces that were generated by files during canal preparation were recorded. The scanning electron microscopy was applied to detect the fracture surfaces.Compared with ProTaper F2 files, the bending loads of OneShape files were significantly lower at deflections of 45°(P < .05), 60° (P < .05) and 75° (P < .01). No significant difference was found at 30°. OneShape files presented a higher NCF in both 60° and 90° canals than the control (P < .01). No significant difference of NCF was found between OneShape and ProTaper files in 30° canals. During the preparation of 30° canals by both files, the negative forces were dominant. With the increase of the curvature, more positive forces were observed. When the OneShape Files were compared with the control, significant different forces were found at D3 and D2 (P < .05) in 30° canals, at D2 (P < .05), D1 (P < .01) and D0 (P < .01) in 60° canals, and at D4 and D3 (P < .01) in 90° canals.OneShape files possessed a reliable flexibility and cyclic fatigue resistance. According to the assessments of the forces generated by files, OneShape instruments performed in a more fatigue-resistant way during curved canal preparation, compared with the ProTaper F2 files.
Abstract Covalent‐organic frameworks (COFs) are emerging organic crystalline materials with a porous framework that extends into two or three dimensions. Originating from their versatile and rigorous synthesis conditions, COFs have abundant and tunable pores, large and easily accessible surfaces, and plenty of redox‐active sites, making them promising material candidates for various energy storage applications. One important area is to serve as capacitive electrode materials in supercapacitors. This review provides a timely and comprehensive summary of the recent progress in the design and synthesis of COF‐based or COF‐derived materials for capacitive energy storage applications. The review starts with a brief introduction to COFs’ structural features and synthesis methods. Next, recently reported literature is categorized and introduced following their different energy storage mechanisms and material assembly or treatment approaches. Finally, the existing challenges and future directions for realizing practical COF‐based supercapacitors are discussed.
Cathodes containing Ni, Co, and Mn frequently undergo side reactions with the electrolyte during the long cycles of the battery in traditional electrolytes under high voltage. In this work, an efficient composite cathode–electrolyte interface (CEI) film is constructed in situ with two additives; that is, 2-[(trimethylsilyl)ethynyl]thiophene (TET) is oxidized and polymerized in advance to form a film attached to the cathode surface, while oxidation products of bis(pinacolato)diboron (BDB) as a high ion conductor are doped into the TET polymer film. The combination of the oxidation products of the two additives not only effectively isolates solvent molecules and hydrofluoric acid erosion, preventing the occurrence of side reactions, but also does not affect the transfer of lithium ions. The crystal structure stability of LiNi0.8Mn0.1Co0.1O2 (NCM811) could be effectively regulated by the composite CEI film through in situ X-ray diffraction characterization during the charge–discharge process. The dynamic performance of the battery has also been improved by comparing the discrepancy of pseudocapacitance across the battery with different electrolytes. Furthermore, the solid–electrolyte interface film formed by TET and BDB could provide effective protection for lithium metal from electrolyte corrosion and inhibit the formation of lithium dendrites. Therefore, the battery capacity retention rate could reach 91.12% after 300 cycles. In addition, the battery with a high-load cathode (2.52 mAh cm–2) has a capacity retention rate of up to 90.19% after 50 cycles, which may make the future application of pouch batteries more feasible.
The productivity of the Machine of Link-plate Selecting( MLS) is restricted mainly by feedrate of link-plate in a slideway. The overall structure and working principle of the MLS is introduced in this paper. According to motion analysies of link-plate, movement differential equation of the link-plate is deduced. And then, computer emulation technique is used to analyses relationship between moving time of link-plate and kinds of system parameters.
Abstract Sulfone liquids can be used as solvents for high‐voltage electrolytes and have been extensively studied for their strong oxidation resistance. However, the problem of high viscosity and susceptibility to side reactions with metallic lithium has been the subject of criticism. To solve the issue of incompatibility with lithium, researchers adopted a high‐concentration electrolyte, namely solvent‐in‐salt, which allows the anions in the lithium salt to preferentially contact the surface of the lithium metal and react to form an SEI film to block the reaction between sulfone solvents and lithium. However, the issue of high viscosity is particularly severe. This work proposes a new solvent model called “solvent‐in‐diluent” electrolyte to address both of these issues simultaneously, different from previous models of salt‐in‐solvent, the model not only effectively prevents sulfone contact with lithium metal surfaces, but also maintains a capacity retention rate of 82% after 500 cycles in the voltage range of 2.8–4.6 V, additionally, the temperature range in which the battery can operate using this electrolyte model has been extended (−20–60°C). This work proposes a new solvent model and challenges the minimum concentration of high‐voltage electrolytes (0.04 m ), providing a new approach and possibility for studying high‐voltage electrolytes.
Metal-nitrogen-carbon (M-N-C) single-atom catalysts (SACs) have emerged as a potential substitute for the costly platinum-group catalysts in oxygen reduction reaction (ORR). However, several critical aspects of M-N-C SACs in ORR remain poorly understood, including their pH-dependent activity, selectivity for 2- or 4-electron transfer pathways, and the identification of the rate-determining steps. Herein, by analyzing >100 M-N-C structures and >2000 sets of energetics, we unveil a pH-dependent evolution in ORR activity volcanos─from a single peak in alkaline media to a double peak in acids. We found that this pH-dependent behavior in M-N-C catalysts fundamentally stems from their moderate dipole moments and polarizability for O* and HOO* adsorbates, as well as unique scaling relations among ORR adsorbates. To validate our theoretical discovery, we synthesized a series of molecular M-N-C catalysts, each characterized by well-defined atomic coordination environments. Impressively, the experiments matched our theoretical predictions on kinetic current, Tafel slope, and turnover frequency in both acidic and alkaline environments. These new insights also refine the famous
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