Molecular Engineering of Phthalocyanine-based Azo Covalent Organic Framework Materials for Improving Lithium Storage Behaviors
Abstract
Phthalocyanine-based polymers are promising for energy storage due to their tunable redox-active sites, robust frameworks, and conjugated properties. However, the structure-property relationship between phthalocyanine content and electrochemical performance remains unclear, hindering the rational design of high-performance electrodes. In this work, the influence of phthalocyanine content was systematically investigated by controlling the molar ratio of N,N,N',N'-tetrakis(p-aminophenyl)p-phenylenediamine (TPPDA) to tetranitro-nickel phthalocyanine (NiPc-(NO2)4) (2:1, 1:1, 1:2). Three TPPDA-NiPc azo polymers were synthesized, revealing that higher phthalocyanine content enhanced structural integrity, azo bond density, and polymerization degree, while incorporating more reversible redox sites. The TPPDA-NiPc (1:2) electrode exhibited superior cycling stability and rate capability, delivering a maximum capacity of 970.5 mAh g-1 at 100 mA g-1- 453.6 and 238.4 mAh g-1 higher than the (2:1) and (1:1) electrodes, respectively. This performance stems from the optimized polymer network and shortened ion transport paths enabled by phthalocyanine incorporation.