Organic electrodes with multi-role natural amino acid groups for sodium-ion batteries with high-capacity and long-life

Organic electrodes possess numerous advantages of structure designability, high capacity, and accommodating large cations. However, the capacity of organic electrode materials in sodium-ion batteries remains low, and their solubility in organic electrolytes leads to a shortened lifespan. Researchers are thus concerned about enhancing their performance through compound design. In this study, we successfully improved both the capacity and cycling stability by simply grafting amino acids onto organic compounds (PMCDI). Firstly, the introduction of amino acids facilitated the formation of a more stable layered structure of PMCDI through hydrogen bonding. Additionally, the amino acid groups promoted intermolecular interactions between the organic electrode material and the carboxymethyl cellulose binder, thereby reducing interfacial resistance and significantly enhancing the cycling stability for over 2000 cycles. Secondly, both experimental and computational results revealed that the non-conjugated carboxylic acid group provided Na+ transport pathways and an additional reversible storage site, leading to an improvement in specific capacity (similar to 300 mA h g(-1)). The strategy employed in this work sheds light on the design of organic molecules for future sodium-ion batteries.