Advanced Characterization Techniques for Probing Redox Reaction Mechanisms in High-Performance Li–S Batteries

Abstract

The development of high-performance energy storage systems requires several key attributes, including high energy and power density, cost-effectiveness, safety, and environmental sustainability. Among the various potential technologies, lithium–sulfur batteries stand out as a promising contender for future energy storage solutions due to their exceptional theoretical specific energy density (2600 Wh kg⁻¹) and relatively high specific capacity (1675 mAh g⁻¹). However, the commercialization of lithium–sulfur batteries faces significant challenges, such as low sulfur loading, rapid capacity degradation, and poor cycling stability. At the heart of these issues lies a limited understanding of the complex conversion chemistry involved in lithium–sulfur batteries. In recent years, significant progress has been made in elucidating these reaction mechanisms, thanks to the use of both ex situ and in situ characterization techniques. Methods such as optical spectroscopy, time-of-flight secondary ion mass spectrometry, synchrotron X-ray, and neural network analysis have demonstrated great potential in uncovering the redox processes of lithium polysulfides and their underlying mechanisms, significantly advancing research in lithium–sulfur battery systems. This review focuses on the major advancements in lithium–sulfur batteries research, particularly in the study of electrocatalytic mechanisms using emerging characterization techniques. We discuss key aspects of accurately revealing the mechanisms of lithium–sulfur batteries through these advanced diagnostic methods, as well as the main challenges these techniques face. Finally, we explore the future prospects of lithium–sulfur battery commercialization.