Li-Binding Thermodynamics and Redox Properties of BNOPS-Based Organic Compounds for Cathodes in Lithium-Ion Batteries

Abstract

Cyclic organic compounds with pentagon rings have been paid less attention for cathodes in lithium-ion batteries as compared with aromatic compounds. In this study, we investigate the Li-binding thermodynamics, redox properties, and theoretical performance for a selected set of heteroatom-containing, pentagon-shaped, organic compounds, namely borole, pyrrole, furan, phosphole, thiophene, and their derivatives to assess their potential for organic cathode materials. This investigation provides us with three important findings. First, the Li-binding thermodynamics and redox properties for the organic compounds would be systematically tailored by the type of the incorporated heteroatom and backbone length, exhibiting both the strongest Li-binding and the highest redox potential for borole. Second, it is highlighted that borole can store up to two Li atoms per molecule exhibiting the exceptionally high charge capacity (839 mA h/g) despite the absence of any well-known redox-active moieties (e.g., carbonyl). Third, dibenzothiophene exhibits weak and comparable Li-binding strengths at multiple feasible binding configurations with an indication of its low Li-storage capability, while the others dominantly bind with Li at their most stable binding configurations. All these findings will provide an insight into the guidelines for the systematic design of promising heterocyclic organic compounds (i.e., borole-based insoluble polymeric forms) for cathodes in secondary batteries.

Electrochemical Energy Storage Capability of Pyrenetetrone Derivatives Tailored by Nitrogen Dopants

“…First, the redox potential of pyrenetetrone continuously increases with the number of incorporated nitrogen dopants, exhibiting the significant change in the redox potential from 2.33 V vs. Na/Na + for the 0N-pyrenetetrone to 3.36 V vs. Na/Na + for the 4N-pyrenetetrone. This increase arises from the reductive nature of the main backbone improved by the inductive effect of the incorporated nitrogen dopants. − A similar observation was highlighted in our previous study associated with the assessment on the potential of the same compounds for cathodes in lithium-ion batteries . It needs to be highlighted that the redox potential of 4N-pyrenetetrone is relatively high as compared with those of other organic cathode materials for sodium-ion batteries .…”

Unexpected Electrochemical Behavior of Crown-Based Organic Compounds for Lithium-Ion Battery Cathodes

“…Essentially, the correlations indicate that a crown-based organic compound with more negative electron affinity and LUMO has higher redox potential. Similar observations have been reported previously for other organic compounds. ,,− ,− ,− The fitted linear correlations of the redox potential with electron affinity and LUMO are described by “ y = −22.5 x + 0.786 ( R -square = 0.97)” and “ y = −0.41 x – 0.57 ( R -square = 0.68)”, respectively. The strong linear correlations of the redox potential with electron affinity and LUMO are reasonable, considering that electron affinity is the amount of free energy required for the reduction of a compound and LUMO describes the lowest energy level for an electron added to a compound.…”

“…Our previous studies have highlighted that structure-derived variations in the redox properties would originate from two primary factors: (1) electronic characteristics and (2) solvation. [27][28][29][30]46 Figure 5 shows the correlations between the redox potentials and four main electronic characteristics (electron affinity, the lowest unoccupied molecular orbital (LUMO), the highest occupied molecular orbital (HOMO), and HOMO−LUMO gap).…”

“…As discussed above, the redox properties of the designed crown-based organic compounds show a strong structural dependence. Our previous studies have highlighted that structure-derived variations in the redox properties would originate from two primary factors: (1) electronic characteristics and (2) solvation. − , Figure shows the correlations between the redox potentials and four main electronic characteristics (electron affinity, the lowest unoccupied molecular orbital (LUMO), the highest occupied molecular orbital (HOMO), and HOMO–LUMO gap). Essentially, the correlations indicate that a crown-based organic compound with more negative electron affinity and LUMO has higher redox potential.…”

Insights on Redox Properties of Sumanene Derivatives for High-Performance Organic Cathodes

“…In the pursuit of high-performance organic cathode materials, considerable efforts have recently focused on the identification of promising organic compounds with favorable electrochemical characteristics and improved charge/energy storage capability. Triggered by the attractive redox activities of conducting polymers, such as polypyrroles , and polythiophenes, studies have been extended to the examination of various organic materials. ,,− For example, Chen and co-workers developed a two-dimensional covalent-organic framework, namely, poly­(imide-benzoquinone), via in situ polymerization on graphenes as cathodes in lithium-ion batteries . They highlighted that a favored charge transfer from graphene to poly­(imide-benzoquinone) improved the accessibility of charge carriers toward the high-density of redox-active carbonyl moieties, leading to the high charge capacity.…”