With the increasing emphasis on environmental protection, the development of flame retardants for epoxy resin (EP) has tended to be non-toxic, efficient, multifunctional and systematic. Currently reported flame retardants have been capable of providing flame retardancy, heat resistance and thermal stability to EP. However, many aspects still need to be further improved. This paper reviews the development of EPs in halogen-free flame retardants, focusing on phosphorus flame retardants, carbon-based materials, silicon flame retardants, inorganic nanofillers, and metal-containing compounds. These flame retardants can be used on their own or in combination to achieve the desired results. The effects of these flame retardants on the thermal stability and flame retardancy of EPs were discussed. Despite the great progress on flame retardants for EP in recent years, further improvement of EP is needed to obtain numerous eco-friendly high-performance materials.

Sodium ion batteries (SIBs) have been extensively investigated as a promising alternative for lithium ion batteries (LIBs) owing to the readily available character of sodium, lower costs of battery systems, as well as a similar working mechanism to LIBs. However, this view turns out to be oversimplified; countless reviews especially in the last years contradict each other, and it is still a challenging task to design highly performing electrode materials for SIBs. Due to the larger radius of Na⁺, its lower covalent character, and the resulting changes in intercalation chemistry, sodium is far from being only the bigger relative of lithium, and the difference leads to altered loading curves, and the occurrence of a multiplicity of binding sites. An in‐depth holistic understanding of the sodium storage mechanisms is needed to resolve the controversial discussions in the research community, ideally starting with unquestionable thermodynamic points. Here, taking a tutorial perspective, first the recent discussions on the storage mechanism of sodium in carbons are reviewed from an unorthodox viewpoint, namely addressing sodium uptake as a multifaceted adsorption process with an added electrochemical binding potential. This model is based on literature data. Afterward, challenges and perspectives revealed by such a model are discussed.