Designing High Performance Organic Batteries

Conspectus Redox active organic and polymeric materials have witnessed the rapid development and commercialization of lithium-ion batteries (LIBs) over the last century and the increasing interest in developing various alternatives to LIBs in the past 30 years. As a kind of potential alternative, organic and polymeric materials have the advantages of flexibility, tunable performance through molecular design, potentially high specific capacity, vast natural resources, and recyclability. However, until now, only a handful inorganic materials have been adopted as electrodes in commercialized LIBs. Although the development of carbonyl-based materials revived organic batteries and stimulated plentiful organic materials for batteries in the past 10 years due to their high theoretical capacities and long-term cycleabilities compared with their pioneers (e.g., conducting polymers), organic batteries are still facing many challenges. For example, it is still essential to enhance the theoretical and experimental capacities of organic materials. Moreover, typically, organic materials suffer relatively low conductivity, which limits their rate capability. In addition, many organic materials, especially small molecules, show poor cycling stability because of their dissolution in organic electrolytes. Other requirements, such as high voltage output and low cost, are also crucial for organic batteries. Therefore, insights into fundamentals (e.g., intramolecular and intermolecular interactions) for a deep understanding of organic batteries and constructive strategies ranging from material design to manipulation of other components (e.g., conductive additives, binders, electrolytes, and separators through controlling the intramolecular and intermolecular interactions and manipulating the ionic transport) are of great significance to boost the performance of organic batteries. In this Account, we give an overview of our efforts to develop high performance organic batteries with various strategies from the aspects of molecular design and the manipulation of other components. Inspired by the experience in organic electronics, we proposed that the extension of the π-conjugated system is helpful for stabilizing the +1/–1 charge/discharge states, improving the charge transport, and facilitating the layered packing (good for ionic diffusion) and hence would benefit the rate capability and cyclability. The π–d conjugation can effectively improve the electrical conductivity and pro