Emerging organic electrodes for Na-ion and K-ion batteries

The redox-active organic compounds are the suitable electrode materials for Li/Na/K-ion batteries. Since organic solids are mainly made of organic building units through Van der Waals forces, organic electrodes can provide enough void space to electrochemically store large-radius Na+ ion and K+ ion. This discovery indicates that one properly-designed organic electrode can be simultaneously applied into Li/Na/K-ion batteries, paving a wider road for the development of organic electrodes in the future. In fact, this research field recently becomes very hot and huge progress has been witnessed. Thus, it is right time for us to summarize the historic development track of organic electrodes applied in Na-ion and K-ion batteries during the past decade. The electron-storage and Na/K-ion-storage mechanisms of these organic electrodes are fully unveiled according to their typical organic functional groups and redox mechanisms. Meanwhile, the general principles and useful tactics for designing organic electrodes are provided. Finally, the structure-property relationship from the perspective of molecule level and the performance of the fabricated Na-ion and K-ion batteries are comprehensively compared and discussed.