Construction of Large Non-Localized π-Electron System for Enhanced Sodium-ton Storage

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 pi-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 pi-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.

Automated summary

A phthalocyanine derivative (TPcDS) with a large non-localized pi-electron system was designed through thermodynamic polymerization to address issues such as low conductivity and high dissolution rate in small molecular organic materials for sodium-ion batteries. The TPcDS molecule achieved a high reversible capacity of 364 mAh g(-1) and maintained a charge capacity of 246 mAh g(-1) after 500 cycles at 0.1 A g(-1), showcasing its potential as an effective organic electrode material.