Oscillation Charging Dynamics in Nanopore Supercapacitors with Organic Electrolyte.

Nanopore electrodes have the potential to enhance the energy density of supercapacitors but tend to reduce charging dynamics, consequently impacting power density. A comprehensive understanding of their charging mechanisms can provide insights into how to boost charging dynamics. In this work, we conducted constant-potential-based molecular dynamics simulations to explore the charging mechanism of nanopore supercapacitors with organic electrolytes. Contrary to the traditional understanding associating larger pore sizes with faster charging, our results found a complex oscillatory behavior of the charging rate, correlating with nanopore size in organic electrolytes. An anomalously increased charging dynamics was found in the 0.9 nm pore. This anomalous enhancement can be attributed to the improved in-pore ion diffusion and reduced desolvation energy, owing to the orientation transition of the solvate molecules. These results pave a new way for innovative designs of nanoporous electrode supercapacitors that can enlarge both power and energy densities.

Horn-like Pore Entrance Boosts Charging Dynamics and Charge Storage of Nanoporous Supercapacitors.

Optimizing the synergy between nanoporous carbons and ionic liquids can significantly enhance the energy density of supercapacitors. The highest energy density has been obtained as the size of porous carbon matches the size of ionic liquids, while it may result in slower charging dynamics and thus reduce the power density. Enhancing energy storage without retarding charging dynamics remains challenging. Herein, we designed porous electrodes by introducing an optimized horn-like entrance to the nanopore, which can concurrently improve supercapacitors' charging dynamics and energy storage. Our results revealed the mechanism of improved charging lies in the gradual desolvation process and optimized ion motion paths: the former expedites the adsorption of the counterion by reducing the transitional energy barrier for ions entering the pores, and the latter accelerates the co-ion desorption and eliminates ion overfilling. Meanwhile, the enhancement of energy density could be attributed to the multi-ion coordinated migration.

Molecular Understanding of Charging Dynamics in Supercapacitors with Porous Electrodes and Ionic Liquids.

Porous electrodes and ionic liquids could significantly enhance the energy storage of supercapacitors. However, they may reduce the charging dynamics and power density due to the nanoconfinement of porous electrodes and the high viscosity of ionic liquids. A comprehensive understanding of the charging mechanism in porous supercapacitors with ionic liquids provides a crucial theoretical foundation for their design optimization. Here, we review the progress of molecular simulations of the charging dynamics in supercapacitors consisting of porous electrodes and ionic liquids. We highlight and delve into the breakthroughs in the ion transport and charging mechanism for electrodes with subnanometer pores and realistic porous structures. We also discuss future directions for the charging dynamics of supercapacitors.

Energy Storage Mechanism in Supercapacitors with Porous Graphdiynes: Effects of Pore Topology and Electrode Metallicity.

Porous graphdiynes are a new class of porous 2D materials with tunable electronic structures and various pore structures. They have potential applications as well-defined nanostructured electrodes and can provide platforms for understanding energy storage mechanisms underlying supercapacitors. Herein, the effect of stacking structure and metallicity on energy storage with such electrodes is investigated. Simulations reveal that supercapacitors based on porous graphdiynes of AB stacking structure can achieve both higher double-layer capacitance and ionic conductivity than AA stacking. This phenomenon is ascribed to more intense image forces in AB stacking, leading to a breakdown of ionic ordering and the formation of effective "free ions". Macroscale analysis shows that doped porous graphdiynes can deliver outstanding gravimetric and volumetric energy and power densities due to their enhanced quantum capacitance. These findings pave the way for designing high-performance supercapacitors by regulating pore topology and metallicity of electrode materials.

Gastrin-17 Combined with CEA, CA12-5 and CA19-9 Improves the Sensitivity for the Diagnosis of Gastric Cancer.

BACKGROUND: Previous studies reported the utility of serum tumor markers (such as CEA, CA12-5 and CA19-9) and gastrin-17 in the diagnosis of gastric cancer (GC). However, the value of these serum markers for diagnosing GC is still under debate. In this study, we aimed to evaluate the effect of gastrin-17, CEA, CA12-5 and CA19-9 in the diagnosis of GC. METHODS: The level of CEA, CA12-5, CA19-9 and gastrin-17 was tested in 230 GC patients and 99 healthy people. The value of the four markers for diagnosing GC was analyzed. RESULTS: The positive rate of Gastrin-17, CEA, CA19-9 and CA12-5 was much higher in GC group (22.61%, 22.61%, 20.00% and 8.26%, respectively) than that of healthy control group (5.05%, 2.02%, 1.01% and 2.02%, respectively). The sensitivity of Gastrin-17, CEA, CA12-5 and CA19-9 in the diagnosis of GC was 22.61%, 22.61%, 6.96% and 20.00%, respectively, and the corresponding specificity was 94.95%, 97.98%, 98.99% and 98.99%, respectively. By using the optimal cut-off value derived from the area under curve (AUC) of receiver operating characteristic curve, the AUC of gastrin-17, CEA, CA12-5, CA19-9 increased to 0.72, 0.64, 0.61 and 0.65, respectively. After combining the four markers, the AUC increased to 0.79 (95% CI: 0.75-0.84), and the corresponding sensitivity and specificity were 65.22% (95% CI: 58.70-71.40%) and 84.85% (95% CI: 76.20-91.30%), respectively, which were significantly higher than those of separate markers (P < 0.05). CONCLUSION: CEA, CA12-5, CA19-9 and gastrin-17 were all valuable in the diagnosis of GC, and gastrin-17 had the best diagnostic value among the four markers. Gastrin-17 combined with CEA, CA12-5 and CA19-9 could improve the diagnostic value of GC significantly. Prospective, multi-center studies are needed to validate our findings.

Modeling galvanostatic charge-discharge of nanoporous supercapacitors.

Molecular modeling has been considered indispensable in studying the energy storage of supercapacitors at the atomistic level. The constant potential method (CPM) allows the electric potential to be kept uniform in the electrode, which is essential for a realistic description of the charge repartition and dynamics process in supercapacitors. However, previous CPM studies have been limited to the potentiostatic mode. Although widely adopted in experiments, the galvanostatic mode has rarely been investigated in CPM simulations because of a lack of effective methods. Here we develop a modeling approach to simulating the galvanostatic charge-discharge process of supercapacitors under constant potential. We show that, for nanoporous electrodes, this modeling approach can capture experimentally consistent dynamics in supercapacitors. It can also delineate, at the molecular scale, the hysteresis in ion adsorption-desorption dynamics during charging and discharging. This approach thus enables the further accurate modeling of the physics and electrochemistry in supercapacitor dynamics.

Ion Structure Transition Enhances Charging Dynamics in Subnanometer Pores.

Using electrodes with subnanometer pores and ionic liquid electrolytes can improve the charge storage capacity at the expense of the charging rate. The fundamental understanding of the charging dynamics of nanoporous electrodes can help to avoid compromising the power density. In this work, we performed molecular dynamics simulations to reveal the charging mechanism of subnanometer pores in ionic liquids. Different from the traditional view that a smaller pore results in slower charging, a non-monotonic relation is found between the charging rate and pore size, in which the charging process is accelerated in some subnanometer pores. Our analysis uncovers that the mechanism of the charging enhancement can be attributed to the transition of in-pore ion structure.