Thiophene derivatives as electrode materials for high-performance sodium-ion batteries

Organic compounds with high theoretical capacity, tunable redox potentials and rich structural chemistry are considered as promising electrode materials for sodium-ion batteries (SIBs). However, organic electrode materials suffer from low electronic conductivity and low structural stability, hindering their practical applications. Thiophene compounds have been well considered in the design of photoelectric materials with improved charge transfer properties. It is envisaged that electron-transfer capability is also essential in addressing the issues of organic electrode materials for SIBs. Herein, sodium thieno[3,2-b]thiophene-2,5-dicarboxylate (STTDC), an organic compound with high electron transfer capability is designed and synthesized. When employed as an electrode material for SIBs, remarkably high electrochemical performance, including large reversible capacity, high rate capability and excellent stability was achieved. A large specific discharge capacity of 430 mA h g−1 is delivered at a current density of 50 mA g−1. A high reversible capacity of approximately 288 mA h g−1 is retained after 4000 cycles at a high current density of 2.0 A g−1. The present work sheds new light on the design of high-performance organic electrode materials.