A stable covalent organic framework cathode enables ultra-long cycle life for alkali and multivalent metal rechargeable batteries

Organic electrode materials are promising candidates for sustainable and large-scale energy storage. However, the short lifespan caused by low redox stability and high solubility in electrolytes severely hinders their application. Hexaazatrinaphthalene (HATN), a popular organic cathode material possessing high theoretical capacity, also confronts this problem. Herein, for the first time, we combine chemically stable ether bonds with HATN units to synthesize a HATN-based covalent-organic framework (COF), HATN[sbnd]HHTP, to improve the cathode's structural stability and suppress solubility. By incorporating HATN[sbnd]HHTP with CNTs, the product HATN[sbnd]HHTP@CNT achieves high capacity utilization (> 210 mA h g⁻¹ at 50 mA g⁻¹) due to sufficient exposure of active sites and enhanced electronic conductivity. The stable bonding and pseudocapacitive behavior endow HATN[sbnd]HHTP@CNT with the longest lifespan of 4100 h (6900 cycles with 100% retention) among HATN-based cathodes. The cathode also exhibits activity and stability in Mg and Al batteries, further proving HATN[sbnd]HHTP@CNT a universal cathode. XPS, FT-IR and DFT calculations confirm the role of pyrazine groups as redox centers and ether bonds as structure stabilizers. The ultra-stable and universal HATN[sbnd]HHTP@CNT cathode opens a new door to designing robust organic electrodes for reliable and large-scale energy storage.