Sustainable sodium-ion batteries using organic materials: A review on storage mechanisms, progress, emerging concepts and perspectives

In the path of achieving a sustainable and cost-effective energy storage technology, organic materials (OMs) for sodium-ion batteries (SIBs) are considered to be a promising solution. Eliminating the use of transition metals in the battery active materials is in line with “Affordable and Clean Energy,” noted as the Sustainable Development Goal (SDG-7) of the United Nations. OMs used in post lithium-ion batteries are cost-effective, environmentally friendly, and can deliver reasonably high energy density. A diverse class of OMs, such as n-type, p-type, bipolar, and conducting polymers, which contains carbonyl, pyrazine, nitroxy radical-based, and azo-based functional groups, has been investigated. With respect to the type of active material and operating voltage, OMs exhibit a variety of storage mechanisms. Despite this, achieving practical organic sodium-ion batteries (OSIBs) still faces hurdles arising from low operating voltage, poor electronic conductivity, low material loading of organic materials and low cycle life. Despite numerous review articles available for OSIBs, a review paper focused on storage mechanisms of different OSIBs, recent progress, and a solution-oriented perspective for attaining high-performance OMs is still lacking. Here, we have compiled different types of OMs and discussed their storage mechanisms. Highlighted recent research outcomes on OMs, including metal/covalent organic frameworks for high-energy OSIBs. Further, we have discussed different possible all-OSIBs based on the electrode configurations and included a detailed perspective describing how to improve energy density and cycle life to attain practical all-OSIBs.