Integration of carbon nanotubes and azo-coupled redox-active polymers into core–shell structured cathodes with favorable lithium storage

Abstract

Organic redox-active polymers as sustainable and inexpensive alternatives to inorganic electrode materials still suffer from poor intrinsic conductivity and low practical capacity when used in rechargeable batteries. Herein carbon nanotubes (CNTs) are fully encapsulated in azo-coupled hyperbranched polymers (NHP) by an in situ copper(I)-catalyzed oxidative coupling condensation between tris(4-aminophenyl)amine and p-phenylenediamine in the presence of CNTs. The resulting core–shell heterostructures (NHP@CNTs) consist of highly conductive cores and electrochemically-active NHP shells with tailored thickness. Remarkably, when used as organic cathodes, NHP@CNTs deliver a higher reversible capacity (145 mA h g⁻¹ at 0.05 A g⁻¹), better rate capability (68.1 mA h g⁻¹ at 1.0 A g⁻¹), and stronger cycling stability (retaining 85 mA h g⁻¹ over 160 cycles) compared to pure NHP cathodes. The excellent lithium storage performance of NHP@CNTs can be corroborated by their unique core–shell hetero-architectures, which are favorable for fast electron transportation, efficient exposure of active sites, and porous channels accessible to electrolytes. This work may craft an unconventional approach to unlock the barrier of high-rate energy storage for organic batteries.