Novel Polyamine-Based Cathodes for Dual-Ion Batteries
Authors: Obrezkov Filipp , Stevenson Keith J 
Published: July 2021

For decades, the design of energy storage devices constantly faces new challenges associated with the growing demand for portable electronics, electric vehicles and smart grids. [1] In particular, there is an urgent need for development of inexpensive, stable and high-power batteries which are capable to operate without significant capacity losses in charge-discharge cycles. The widespread installation of such devices in the stationary energy storage systems for power plants would allow to create a sustainable smart grid ecosystem.
Dual-ion batteries (DIB) is a special type of energy storage devices in which both cations and anions are involved in redox processes. DIB represent one of the most promising post-lithium technology for stationary energy storage due to their relatively high energy density, rate capabilities and low cost. For the low cost of materials, dual-carbon batteries (DCB), in which both electrodes are presented by carbon materials, is the most popular and well-studied type of DIB. [2] Nevertheless, DCB have significant drawbacks such as low specific capacity of the cathode material (<110 mAh/g), [3] and high operation voltages (>5V) [2,3] leading to rapid electrolyte degradation.
Among the variety of advanced cathode materials for dual-ion batteries, we consider polymeric aromatic amines as the most promising ones for its outstanding performance characteristics. In particular, the materials of this type show optimal values of redox potential (3-4 V vs. Li+/Li), [4] high values of specific capacity (up to 223 mAh/g), [5] and extremely high current rates available for battery charge and discharge (up to 300C). [6]

In the present work, we report synthesis and a comprehensive study of a large group of polymeric aromatic amines as active cathode materials for dual-ion batteries with high theoretical specific capacities (>160 mAh/g). Within the framework of the research project, the cathode materials for ultrafast lithium-based and high-energy potassium-based dual-ion batteries were developed. In particular, the polyamine-based organic cathodes with impressive rate capabilities delivering specific capacities of up to 84 mAh/g at 100C current rate in lithium batteries were designed. [7] The use of cheaper and concentrated potassium-based electrolyte (2.2 M KPF6 in diglyme) allowed us to assemble potassium dual-ion batteries with the cathode energy densities of up to 593 Wh/kg, while poly(N-phenyl-5,10-dihydrophenazine) was applied as an active material. [8] Another significant step towards the dual-ion batteries with improved performance was made by increasing of active material content to impressive for organic cathodes 80%, while poly(diphenylamine) and multi-walled carbon nanotubes were applied as an active material and carbon filler, respectively.
This study was financially supported by the Russian Foundation for Basic Research, project 19-33-90233.

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