Near-Theoretical Redox-Site Utilization and Fast Zn²⁺ Storage in a Polyimide-CNT Cathode

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• High utilization efficiency and fast electrochemical transport are critical challenges for organic cathodes in aqueous zinc-ion batteries.
• Developing advanced organic electrode materials is essential for next-generation energy storage solutions.

Purpose of the Study:

• To design and synthesize a π-conjugated imide-linked polyimide (PMDA-PTO) integrated with carbon nanotubes (CNTs).
• To investigate the electrochemical performance and storage mechanism of the PMDA-PTO-CNT composite in aqueous zinc-ion batteries.

Main Methods:

• Synthesis of a carbonyl-rich conjugated polyimide framework and its integration with a carbon nanotube network.
• Electrochemical testing including galvanostatic cycling, rate capability tests, and long-term cycling stability.
• Ex situ spectroscopic and scattering analyses (FTIR, XPS, GIWAXS) and density functional theory (DFT) calculations to elucidate the storage mechanism.

Main Results:

• The PMDA-PTO-CNT composite achieved a high discharge capacity of 328 mAh g^-1 at 0.05 A g^-1, demonstrating ~98% theoretical capacity utilization.
• Excellent rate capability was observed, maintaining 316 mAh g^-1 at 20 A g^-1, alongside remarkable cycling stability over 10,000 cycles at 5 A g^-1.
• Electrochemical analyses indicated reduced polarization and enhanced pseudocapacitive behavior, supported by mechanistic studies revealing a reversible carbonyl-centered cation-storage mechanism.

Conclusions:

• The integrated CNT network effectively promotes electronic percolation and redox-site accessibility in the PMDA-PTO cathode.
• The study provides crucial insights into structure-transport relationships in quinone-based polymer cathodes for aqueous zinc-ion batteries.
• The developed material demonstrates high utilization, fast kinetics, and long-term stability, paving the way for advanced organic electrode materials.