Solubility Challenges and Strategies for Organic Sodium-Ion Batteries: Status and Perspectives

Organic sodium-ion batteries (OSIBs) possessing excellent characteristics of low price, abundant sources, and eco-compatibility have gained numerous attentions in the recent decade. However, solubility is one of the main severe limitations of the application of OSIBs, especially for small organic molecules. The dissolution of molecules into electrolytes can cause the loss of active materials, the pulverization of electrodes, and even short circuits in batteries, as active materials may shuttle through separators, thus leading to poor cycling stability for sodium-ion batteries. Thus, there is an urgent need to develop insoluble organic molecules for OSIBs. The advanced development of OSIBs over the past decades is overviewed, and the primary challenges faced by long-cycling OSIBs in terms of solubility are systematically analyzed. Focusing on the three core components of the battery system electrodes, separators, and electrolytes, targeted optimization strategies are proposed to mitigate solubility issues and enhance battery performance. In addition, the prospects of OSIBs toward long-cycle stability and practical application are explored.