Increasing the Gravimetric Energy Density of Organic Based Secondary Battery Cathodes Using Small Radius Cations (Li⁺ and Mg²⁺)

Abstract

One of the major challenges in electrochemical energy storage (EES) is increasing the gravimetric capacity and energy density of the cathode material. Here we demonstrate how to increase the gravimetric energy density of electrical energy storage devices based on the use of organic materials through exploitation of the strong ionic coupling between a reduced carbonyl functionality and small cations such as lithium (Li(+)) and magnesium (Mg(2+)). Binding of the cation to the reduced carbonyl results in a positive shift of the formal reduction potential of the carbonyl couple. This has the effect of increasing the cell voltage which, in turn, results in an increase in the energy density. We show how this interaction can be used to dramatically increase, by up to a factor of 2, the energy density for a selected case study using 1,2-di(thiophen-2-yl)ethane-1,2-dione (DTED). We have carried out electrochemical and computational studies in order to understand the thermodynamic (positive shift of 250 mV and 1 V in the formal potential for the first and second reductions, respectively, of the carbonyl groups of DTED) and kinetic effects between small radii cations (Li(+) and Mg(2+)) and the reduced carbonyl functionality of carbonyl-based organic molecules (C-bOMs).

Biologically inspired pteridine redox centres for rechargeable batteries

“…In tetrabutylammonium perchlorate (TBAP), which contains TBA þ as noninteracting cations, pteridine derivatives exhibited two reduction and oxidation peaks in the cyclic voltammetry curves. The use of LiClO 4 as a supporting electrolyte resulted in more complicated redox behaviour with positive shifts of the average redox potentials, which is attributed to the possible existence of interacting Li þ cation 16,28 .…”

Molecular Engineering with Organic Carbonyl Electrode Materials for Advanced Stationary and Redox Flow Rechargeable Batteries

“…Indeed, both the redox potential [183][184][185][186][187][188][189][190] and structural properties [191][192][193] of organic compounds can be predicted by computational studies. However, innumerable organic molecules make it a daunting task to identify optimal structures by experimentation.…”

Recent Developments and Trends in Redox Flow Batteries

“…Furthermore, molecular engineering can also be realized by replacing the C atom with a heteroatom such as N, O, or S, especially for a five-membered ring, which will unburden the capacity penalty imposed by the increased molecular weight from the substituent. The same group also formulated a unique method to tune the redox potential of a carbonyl based organic redox active molecule by exploring the effect of cations in the supporting electrolyte as observed by RDV and verified by DFT [90]. Taking 1,2-di(thiophen-2-yl)ethane-1,2-dione (DTED) as an example, in the presence of a non-coordinating salt (tetrabutylammonium perchlorate), there are two 1-electron transfer processes observed at −1.36 and −2.20 V versus Ag/Ag + .…”