No abstract

No abstract

Despite the potential of large organic molecules for insoluble cathode materials in lithiumion batteries, they have attracted less attention owing to the penalty in the molecular weight. Herein, an advanced computational modeling approach is employed to comprehensively explore the electrochemical characteristics and theoretical charge/energy storage capability for a series of sumanene derivatives. It is highlighted from this investigation that the carbonyl moiety is generally beneficial to the improvement of the redox properties for the sumanenes. The sumanene with hexagon rings fully functionalized by six carbonyls particularly exhibits both the remarkably high redox potential (3.53 V vs Li/Li + ) and performance parameters (454 mAh/g and 1129 mWh/g), implying its candidacy as high-potential organic cathodes. It is further demonstrated from a universal relationship of redox potential-electronic propertysolvation property that a sumanene derivative would experience a two-stage discharging behavior. This indicates that the sumanene derivative would be cathodically inactive due to a sudden increase of solvation energy.

Despite the potential of organic cathodes in sodium‐ion batteries, their redox properties still need to be explored. In this study, a density functional theory modeling approach is employed to comprehensively investigate the redox properties and theoretical performance parameters for a selected set of fluoranil derivatives as cathode materials. The redox properties are further correlated with various characteristics including structural variations, electronic properties, and solvation. Three primary conclusions are drawn. First, the incorporation of bulky trifluoromethyl functional group(s) into fluoranil increases its redox potential but significantly decreases its gravimetric charge capacity. This suggests that the trifluoromethyl functional group(s) would be detrimental to the design of high‐performance batteries. Second, fluoranil exhibits significant enhancements in terms of redox properties and theoretical performance compared with its hydrogenated form, benzoquinone, suggesting a desired strategy for designing high‐performance batteries. Third, the redox properties of fluoranil derivatives would strongly rely not only on structural variations (e.g., bulkiness) and electronic properties (e.g., functionality) but also on solvation energy. It is further verified that cathodic deactivation could be completed by solvation energy. The new understanding will provide us with guidelines for an efficient design of promising organic cathode materials.

Despite the potential of incorporating electron-withdrawing cyano functional groups in organic cathode materials for sodium-ion batteries, a systematic understanding of the effect of the functionality on the redox properties and electrochemical performance is still limited to be explored. Herein, the electrochemical performance parameters as well as the Na-involved electrochemical redox characteristics for a series of chloranil derivatives with one to four cyano functional group(s) are explored using the computational modeling approach to assess their potential as organic cathode materials. It is highlighted from this study that the incorporation of cyano functional groups would improve both the redox potential and theoretical charge capacity, exhibiting the highest open-circuit redox potential (4.16 V vs Na/Na+) and theoretical charge capacity (386.5 mAh/g) for the chloranil derivative with four cyano functional groups. To be noted, the resulting values are comparable to those for top-ranking organic cathode materials in sodium-ion batteries. It is further verified that the beneficial effect of the cyano functional group on both the redox potential and theoretical charge capacity would lead to its positive impact on the theoretical energy density. These indicate that all the three parameters, namely, redox potential, charge capacity, and energy density, would be improved with the number of cyano functional groups. Further investigation reveals that the redox properties of chloranil derivatives would be strongly correlated with their electronic properties and solvation as well as their structural variations. Notably, the redox activity of a chloranil would be continuously weakened by the gradual change in electron affinity during the discharging process but a drastic increase in solvation would be a critical factor causing its cathodic deactivation. All the findings would assist us to establish a design approach for promising organic cathode materials in sodium-ion batteries.