A perylene-based aromatic polyimide with multiple carbonyls enabling high-capacity and stable organic lithium and sodium ion batteries

Redox-active organic electrode materials are considered promising alternatives to inorganic intercalation analogs in organic metal-ion batteries. However, their poor cycling stability owing to high solubility in organic electrolytes and poor electronic conductivity remain a challenge for all-organic battery applications. Constructing new conjugated aromatic polyimides (PIs) or polymers with characteristics of improved electronic conductivity and abundant redox-active units (i.e., dual redox units containing multiple carbonyl groups) is an effective method of preventing these battery problems. In this study, we synthesized a perylene-3,4:9,10-tetracarboxylic dianhydride (perylene)-based aromatic PI as the cathode material, which is incorporated with two distinct types of redox-active units through the polymerization of perylene-3,4:9,10-tetracarboxylic acid with a 2,6-diaminoanthraquinone moiety, which has multiple redox-active carbonyl sites. The as-prepared PI exhibited significantly lower stability problems and enhanced the performance of electrochemical kinetics in both organic lithium and sodium ion batteries owing to improved electronic conductivity via a unique π-conjugation structure and the PI's multiple redox kinetics. The battery cells with the PI cathode exhibited initial discharge capacities of 209 mA h g−1 (for Li+/Li) and 207 mA h g−1 (for Na+/Na) at a high current rate of 200 mA g−1. The PI exhibited a better long-life cycling stability with a high-rate discharge ability (15 mA h g−1 for Li+/Li) with a capacity retention of 14%; and 78 mA h g−1 for Na+/Na with 54% capacity retention at a current density of 1C over 1000 cycles. These values are among the best when the delivered high specific capacities and stable cycle performance of both Li+/Na+ ion storage are compared with the previously reported similar PIs used for Li+-ion storage. This demonstrates the promising potential application of multiple redox-active units (i.e., dual redox-active units) in the design of sustainable cathodic materials for next-generation electrochemical energy storage devices.