Hybrid Organosulfur Cathode Materials for Rechargeable Lithium Batteries

The success of lithium-ion batteries (LIBs) has driven the vigorous development of mobile electronic devices and electric vehicles. As a key component of LIBs, the energy density of traditional cathode materials has approached the theoretical limit, and the scarce transition metal elements have significantly increased the cost of batteries. In pursuit of cheap, abundant, and high-capacity materials, more attention is being focused on conversion-type cathodes. Sulfur (S), as a competitive nonmetallic element with extremely high theoretical capacity, has been widely studied in recent years. However, the poor conductivity of S and its discharge product, high solubility of the intermediate product polysulfides, and large volume change during cycling limit the practicality of S cathodes. Organosulfur materials, as a supplement to S cathodes, are considered promising organic electrode materials due to their high capacity, structural designability, and low cost. Unfortunately, the inherent high solubility and sluggish kinetics of organosulfur molecules hinder their further development. To break through the bottleneck faced by organosulfur compounds, various strategies have been adopted including conductive additives, electrocatalytic mediators, advanced electrolytes, and modified separators. Among them, the introduction of inorganic components can effectively regulate the characteristics of organosulfur molecules, thereby greatly improving the electrochemical performance of organosulfur batteries. In this Account, we first introduce the redox mechanism of organosulfur cathodes and provide a detailed discussion of the current development bottlenecks of organosulfur materials. Meanwhile, the strategy of improving the performance of organosulfur batteries through the construction of organic-inorganic composite cathodes is emphasized. In the design of organosulfur molecules, various heteroatoms such as N, O, and Se are introduced into the functional groups. The regulation of electronic structure and physicochemical properties at the molecular level can fundamentally manipulate the electrochemical performance of organosulfur. Second, the addition of conductive substrates like carbon nanotubes (CNTs) and reduced graphene oxide (rGO) with high conductivity and specific surface area provides rich conductive pathways and sufficient physical adsorption for organosulfur compounds. In addition, the introduction of a catalytic medium including transition metal sulfides and oxides can reduce the dissolution of soluble S species through strong polar adsorption and accelerate the conversion of organosulfur through electrocatalytic ability. Intermolecular or atomic interactions between active organosulfur groups and inorganic materials provide a simple and practical solution for improving the electrochemical performance of organosulfur materials. Finally, solutions to the challenges faced by organosulfur cathodes and the future development prospects of high-performance organosulfur batteries are summarized. Overall, it is expected that this Account could inspire more interest in cathode materials design and provide promising directions for the design of practical next-generation rechargeable lithium batteries and beyond.