Tailored Design of Electrochemically Degradable Anthraquinone Functionality toward Organic Cathodes

Abstract

In efforts to design organic cathode materials for rechargeable batteries, a fundamental understanding of the redox properties of diverse non-carbon-based functionalities incorporated into 9,10-anthraquinone is lacking despite their potential impact. Herein, a preliminary investigation of the potential of anthraquinones with halogenated nitrogen-based functionalities reveals that the Li-triggered structural collapse observed in the early stage of discharging can be ascribed to the preference toward the strong Lewis acid–base interaction of N–Li–X (X = F or Cl) over the repulsive interaction of the electron-rich N–X bond. A further study of three solutions (i.e., substitution of NX2 with (i) BX2, (ii) NH2, and (iii) BH2) to the structural decomposition issue highlights four conclusive remarks. First, the replacement of N and/or X with electron-deficient atom(s), such as B and/or H, relieves the repulsive force on the N–X bond without the assistance of Li, and thus, no structural decomposition occurs. Second, the incorporation of BH2 is verified to be the most beneficial for improving the theoretical performance. Third, all the redox properties are better correlated with electron affinity and solvation energy than the electronegativity of functionality, implying that these key parameters cooperatively contribute to the electrochemical redox potential; additionally, solvation energy plays a crucial role in determining cathodic deactivation. Fourth, the improvement to the Li storage capability of anthraquinone using the third solution can primarily be ascribed to solvation energy remaining at a negative value even after the binding of more Li atoms than the other derivatives.

Anthraquinone and its derivatives as sustainable materials for electrochemical applications – a joint experimental and theoretical investigation of the redox potential in solution

“…In addition molecular data visualizations for the electrostatic surface potentials 26,82 have been prepared for all AQ derivatives and correlated against the measured electrochemical potential as shown in Fig. S10 (ESI†).…”

“…In addition, electrostatic surface potentials (ESPs) 26,82 were generated for all AQ derivatives, considering again only the most accurate calculation method being DFT at the B3LYP+D3/ 6-31++G(d,p)/SMD level, and the compounds were sorted according to their respective measured electrochemical potentials.…”

“…In contrast, the IP shows a surprisingly low correlation, and since the electronegativity and hardness are both derived from IP and EA data, the respective correlation against the experimental data is considerably poor as well. In addition molecular data visualizations for the electrostatic surface potentials 26,82 have been prepared for all AQ derivatives and correlated against the measured electrochemical potential as shown in Fig. S10 (ESI †).…”

“…24 Among the various types of organic materials, small molecular compounds are considered as highly promising candidates. In particular, quinone-based derivatives, such as anthraquinones (AQ), [25][26][27] are intensely studied for their potential application as a cathode material in metal-ion batteries. 28 This is inter alia a consequence of their capability to accommodate a two-electron reduction, resulting in a high energy storage capability in combination with fast charging/discharging rates.…”

Carbonyl-Based Redox-Active Compounds as Organic Electrodes for Batteries: Escape from Middle–High Redox Potentials and Further Improvement?

“…The quest for performant organic electrodes has thus given rise to different strategies, with the objective to develop suited materials or electrode manufacturing for this type of application (see, e.g. , refs − ). In this area, fancy ways of discovering new materials precisely targeted toward device optimization with departure from standards mainly rely on the conjunction of synthesis feasibility and subsequent obtention of satisfying features especially (but not solely) of electrochemical nature.…”