New Tetraazapentacene-Based Redox-Active Material As a Promising High-Capacity Organic Cathode for Potassium Batteries
Authors: Ramezankhani Vahid , Yakuschenko Igor K. , Shestakov Alexander F. , Stevenson Keith J. , Troshin Pavel A. 
Published: February 2020

Following the Paris agreement signed in 2015 to address the problem of global climate change, many countries are aiming to decrease CO2 emissions particularly by using renewable sources of energy, e.g. solar, wind, geothermal, etc. However, any massive implementation of renewables requires cheap and efficient solutions for bulk energy storage. There are limited examples of application of lithium-ion batteries (LIBs) for peak shaving in electric grids and for storage of the energy produced by solar plants. The main obstacle for implementation of LIBs on a large scale is related to their high cost dictated by both low abundance of lithium resources and use of expensive nanostructured inorganic cathode materials. It should be emphasized that the total amount of lithium available on the planet is insufficient even for replacing all cars currently used in the world with electric vehicles while leaving unsatisfied all other demands for energy storage. Therefore, it is imperative to develop alternative post-lithium battery technologies.
Potassium-ion batteries (KIBs) have recently attracted a particular attention since there are abundant resources of potassium in both Earth’s crust and oceans, which make this element almost an order of magnitude cheaper than lithium. Moreover, KIBs usually show higher discharge voltages in comparison with lithium-ion and, especially, sodium-ion batteries thus featuring a potential for reaching high energy densities [1]. However, the current progress in the development of KIBs is strongly limited by scarce number of suitable inorganic cathodes, which can deliver decent capacities and charge-discharge cycling stabilities.
Organic redox-active materials represent a promising alternative since they are based on abundant elements, can be cheap and environment friendly [2]. In this work we present a new organic cathode for metal-ion batteries based on octahydroxytetraazapentacene (OHTAP) possessing a theoretical capacity of ~ 520 mAh g-1. To evaluate the K-ion storage properties of OHTAP, we assembled K//OHTAP cells using either the tape or the spray coating of the slurry (OHTAP+Super-P+PVDF in NMP) on Al or Al/C current collectors. A 1 M potassium bis(trifluoromethane sulfonyl) imide (KTFSI) solution in dimethoxyethane and dioxolane mixture (DOL : DME = 1:1 v/v) was used as the electrolyte. The fabricated cells delivered stabilized capacities of >220 mAh g-1 after 10 cycles, which are among the best values reported so far for both organic and inorganic cathode materials in potassium-ion batteries. The obtained results pave a way to the development of a new family of organic cathodes for advanced potassium-ion batteries.

References

[1]. Haegyeom Kim, Jae Chul Kim, Matteo Bianchini, Dong-Hwa Seo, Jorge Rodriguez-Garcia, and Gerbrand Ceder// Advanced Energy Materials, 201702384.
[2]. Tyler B. Schon, Bryony T. McAllister, Peng-Fei Li and Dwight S. Seferos// Chem. Soc. Rev., 2016, 45, 6345