Supercritical CO₂ in the Development of Highly Efficient Composite Cathodes for Li-S Batteries

Conventional Li-S battery cathode synthesis routes are time-consuming, energy-intensive, use toxic solvents, and yet fail to effectively confine sulfur into carbon matrices, reducing the cathode efficiency. Supercritical CO₂ (scCO₂) presents notable benefits as a "green solvent" due to its affordability, chemical inertness, recyclability, non-flammability, and non-toxicity. It eliminates the need for energy-intensive post-heat treatments, providing a more sustainable and efficient option. CO₂ in supercritical state gains unique gas-like and liquid-like properties that enable precise sulfur loading, uniform encapsulation, and improved sulfur-carbon interactions, which enhance conductivity and reaction kinetics. Recent studies show that cathodes prepared using scCO₂ exhibit exceptional electrochemical performance, including long-term cycling stability and high coulombic efficiency. The versatility of scCO₂ in infiltrating various host architectures also makes it suitable for a wide range of cathode designs. Despite its tremendous potential, this advanced synthesis technology is often overlooked in textbooks, underscoring the need for awareness within the research community. This review highlights the remarkable features of scCO₂ and examine up-to-date research progress, focusing on its application in developing high-performance carbon/sulfur composite cathodes. An application-focused audience would benefit from a summary of this review, as they reveal new Li-S cathode synthesis technologies that haven't been widely explored or discussed.