Lithium–sulfur batteries could store substantially more energy than conventional lithium-ion batteries while relying on sulfur, an abundant and relatively inexpensive material. Heterogeneous/homogeneous catalytic role of molecular catalysts in lithium–sulfur batteries Yi Ke, Can Qian, Zhuang Ji, Yuan Yang, Cai Qi, Xinwei Wang, Jinhai Zhang, Yuping Wu & Yiren ZhongA new review published in Energy & Environment Nexus examines how precisely designed molecular catalysts could address these challenges. "Molecular catalysts give researchers an unusually precise way to control the complex sulfur reactions inside lithium–sulfur batteries," said corresponding author Yiren Zhong. Why lithium–sulfur batteries lose performance Lithium–sulfur batteries have a theoretical specific capacity of 1,672 milliampere-hours per gram and a theoretical energy density of 2,600 watt-hours per kilogram. These systems immobilize molecular catalysts while preserving some of the mobility and accessibility associated with homogeneous catalysis.