Ionic liquids have been widely used in lithium-sulfur battery electrolytes in recent years due to their excellent physicochemical properties and the ability to inhibit the dissolution of lithium polysulfides intermediates. Among those products during the battery cycling processes, insoluble Li2S and Li2S2 are inclined to aggregate and deposit on the electrode surface, affecting the battery performance. However, there are few studies on the microscopic mechanism of their clustering behaviors and electrolyte properties. In this work, the microstructure of Li2S/Li2S2 in ionic liquids and the formation of clusters were studied by DFT calculations and molecular dynamics simulations. From the optimized configurations using DFT methods, it can be seen that ionic liquids and Li2S/Li2S2 always tended to form a "cation-short chain polysulfide-anion" sandwich-like structures. By analyzing the microstructures of the molecular dynamics simulation systems, it can be found that the methyl group in side chain of cation mainly interacted with S in Li2S/Li2S2, and the Li-S interaction between short-chain polysulfides was much stronger than Li-O interaction in anions. The results of cluster size distribution showed that short-chain polysulfides were more likely to form large clusters in the [TFSI]-based ionic liquid, while the proportion of large clusters in Li2S2 system was higher than Li2S systems. Moreover, the tendency of forming large clusters increased with the concentration of Li2S/Li2S2. Additionally, stronger coordination ability of anions brought smaller proportion of large Li2S clusters. However, the configuration characteristics and interaction forms of anions-Li2S will also affected the sizes and structures of clusters. These understandings could provide theoretical guidance for future systematic studies on screening and designing ionic liquids electrolytes for lithium-sulfur batteries.
Dibutyl phthalate as a plasticizer is widely used in all walks of life. As an endocrine interferon, the pollution caused by it cannot be ignored, and it will harm the health of biology and human body. Because it is difficult to degrade effectively in common wastewater treatment processes, it is urgent to find effective treatment methods. As one of the advanced oxidation technologies, electro-Fenton has great advantages in treating refractory wastewater and has made many achievements. But the difficulty of electro-Fenton technology is to find an efficient and reusable catalyst. In this work, an efficient bimetal catalyst for the treatment of dibutyl phthalate in electro-Fenton system was studied. Aluminum modified bimetallic catalyst Fe-Ce/Al-MCM-41, was prepared by hydrothermal-calcination method using MCM-41 as template and characterized by XRD, BET and FT-IR. Taking dibutyl phthalate simulated wastewater as the treatment object, the effects of four different conditions, such as initial pH, catalyst dosage, current intensity and oxygen flux, on the degradation efficiency of Perth-carbon felt electro-Fenton system were discussed, and the best operation conditions were found. The characterization results showed that the loading of metal ions did not change the mesoporous structure of MCM-41, which provided sufficient active sites for the follow-up reaction. Under the best experimental conditions, the removal rate of 10 mg/L DBP was 97.1%, the removal rate under acidic and neutral conditions was more than 92.1%, and the removal rate of DBP was reduced under alkaline conditions. Through the comparative experimental analysis of the degradation mechanism, it was found that the iron and cerium bimetallic catalyst had good catalytic activity for the degradation of dibutyl phthalate in electric-Fenton system. Among them, iron ion and cerium ion participated in the catalytic reaction and had synergistic effect, while aluminum ion did not directly participate in the catalytic reaction, but the addition of aluminum ion can improve the catalytic performance of the catalyst. In addition, carbon felt as a cathode had a certain adsorption effect. The main active substance in the electro-Fenton system for the degradation of DBP was ·OH, degrades the target pollutants by the oxidation of ·OH.
