A density functional theory study on the thermodynamic and dynamic properties of anthraquinone analogue cathode materials for rechargeable lithium ion batteries

Abstract

Organic redox compounds have become the emerging electrode materials for rechargeable lithium ion batteries. The high electrochemical performance provides organic electrode materials with great opportunities to be applied in electric energy storage devices. Among the different types of organic materials, conjugated carbonyl compounds are the most promising type at present, because only they can simultaneously achieve, high energy density, high cycling stability, and high power density. In this research, a series of heteroatom substituted anthraquinone (AQ) derivatives were designed theoretically so that the high theoretical capacity of AQ remained. The discharge and charge mechanism as well as the thermodynamic and dynamic properties of AQ and its derivatives were investigated using first-principles density functional theory. Using heteroatom substitution, both the thermodynamic and dynamic properties of AQ as cathode materials could be largely improved. Among these conjugated carboxyl compounds, BDOZD and BDIOZD with a simultaneously high theoretical capacity and high working potential exhibit the largest energy density of about 780 W h kg, which is 41% larger than that of AQ. The PQD with the smallest value of λ gives the largest charge transfer rate constant, which is about four times as large as the prototype molecule, AQ. The most interesting finding is that the lithium ion transfer plays a very important role in influencing both the discharge potential and electrochemical charge transfer rate. The present study illustrates that theoretical calculations provide a highly effective way to discover potential materials for use with rechargeable lithium ion batteries.

Molecular Design of Phenanthrenequinone Derivatives as Organic Cathode Materials

“…For the second strategy, electron‐withdrawing inductive (series E) or conjugative (series F) functional groups are incorporated to PQ. In our recent theoretical study on AQ derivatives, we demonstrated that the electronic structures of conjugated carbonyl compounds could be significantly modified by hetero‐atom substitution . Jang and co‐workers found that the redox properties of the AQ derivatives can be improved by modifying their chemical structures with electron‐withdrawing carboxyl groups…”

“…The HOMO level of PQ‐Li 2 reflects not only the electron affinity but also the bonding energy of the Li‐ion with the carbonyl group. In our recent study, it was illustrated that the HOMO energy of AQ‐Li 2 is a better indicator to evaluate the reduction potential of AQ derivatives because both the electron transfer factor and the Li‐ion transfer factor are included . Figure b shows an excellent linear correlation between the computed reduction potential and HOMO energy of AQ‐Li 2 derivatives.…”

“…The ESP value and reduction potential of five molecules increase in the same order as the electronic effect of heterocyclic compounds, C01<PQ<A03<D05<B03. In our recent study on AQ derivatives, the isoxazole‐ and pyridazine‐substituted AQ also exhibit the highest discharge potential among all the designed molecules …”

“…These studies highlight the potential for carbonyl compounds to be improved through the use of electron‐withdrawing functional‐group substitution. However, the increase in molecular weight considerably reduces the specific capacities and results in overall low energy densities …”

“…Similarly, changing the conjugated backbone of phenanthrenequinone (PQ) from biphenyl to bithiophene and to bipyridine increases the average discharge potential from 2.61 to 2.68 and to 2.74 V (vs. Li/Li + ), respectively . In our recent theoretical study on a series of AQ derivatives, we demonstrated that both thermodynamic and kinetic properties of AQ could be significantly modified by introducing heteroaromatic building blocks . Shimizu et al.…”