Amorphization of fused perylene diimide dimers for high-efficiency potassium-organic batteries

Abstract

Organic carbonyls are emerging as promising electrodes for potassium-ion batteries (PIBs) owing to their remarkable structural adaptability. Nevertheless, most small-molecule carbonyls still face significant challenges related to solubility issues and sluggish kinetics. Herein, a simple but efficient “two in one” strategy is employed, i.e., perylenetetracarboxylic diimide is firstly linked by low-weight ethylene to form a dimer (labelled as PTCDI2) to enhance the intramolecular interactions, followed by tuning through amorphization via electrochemical activation aiming to improve the charge transfer. The resulting PTCDI2 anode delivers high reversible capacity (310 mA h g⁻¹ at 0.5 A g⁻¹), outstanding rate capability (160 mA h g⁻¹ at 10 A g⁻¹) and remarkable long-term cycle stability (over 2000 cycles with a retention of 75%). Ex situ characterization methods demonstrate that improved electrochemical performance of PIBs with PTCDI2 anodes benefits from the following aspects: (1) the ethylene bridge strongly enhances the intramolecular interactions between two PTCDI monomers, thereby effectively overcoming the dissolution issue and (2) the transformation of PTCDI2 from crystalline to amorphous during cycling provides multiple pathways for ions, resulting in accelerated ion dynamics. The concept of incorporating ethylene-bridged structures and inducing amorphization in carbonyl anodes offers an effective avenue to tailor high-performance organic electrode materials for PIBs.