Construction of Large Non‐Localized π‐Electron System for Enhanced Sodium‐Ion Storage

Abstract Organic electrode materials with the advantages of renewability, environment‐friendliness, low cost, and high capacity have received widespread attention in recent years for sodium‐ion batteries. However, small molecular organic materials suffer from issues such as low conductivity and the high dissolution rate in electrolytes. Herein, a phthalocyanine derivative (TPcDS) with a large non‐localized π‐electron system, obtained through thermodynamic polymerization of 4‐aminophthalonitrile (AP) monomers, is designed to address these issues. According to the density function theory calculation, six sodium ions can be attracted by one polymer molecule, indicating a high theoretical capacity of 375 mA h g^‐1. The TPcDS molecule realizes sodium storage through a non‐localized π‐electron system of phthalocyanine macrocycles. When employed as an anode material for sodium‐ion batteries, the functional groups of phthalocyanine macrocycles, such as CN groups in TPcDS, experience obviously reversible structural variation upon discharge/charge. A high reversible capacity of 364 mAh g^‐1 is achieved at a current density of 0.05 A g^‐1, and a charge capacity of as high as 246 mAh g^‐1 is still maintained after 500 cycles at 0.1 A g^‐1. This work provides an effective strategy for the design and synthesis of new oligomeric organic electrode materials.