Selenium or Tellurium as Eutectic Accelerators for High-Performance Lithium/Sodium–Sulfur Batteries

Lithium (Li)/sodium (Na)–sulfur (S) batteries are considered to be competitive candidates for the next-generation energy storage devices due to ultrahigh theoretical energy densities and potential low costs. However, the insulating nature of S and dissolution of intermediate polysulfides hinder the development. Here, the use of selenium (Se) or tellurium (Te) as eutectic accelerators in S cathodes can significantly improve the performances. Se and Te can not only be easily introduced into S to form uniform dispersions at the molecular level through S–Se or S–Te bonds and contribute to capacity through their inherent redox reactions, but also significantly accelerate reaction kinetics and alleviate polysulfide dissolution to achieve excellent battery performances. Even for solid-state conversion mechanisms or in all-solid-state batteries, Se or Te can enhance the electronic and ionic conductivities to result in better rate and cycling performances. Overall, Se or Te modified S cathodes possess good compatibility with both Li and Na anode materials and can exhibit excellent electrochemical performances. Therefore, the use of Se or Te as eutectic accelerators in S cathodes is a universal and effective strategy to enhance battery performances and obtain better Li/Na–S batteries. Graphic Abstract