en.Wedoany.com Reported - A research team led by Academician Sun Shigang and Professor Liao Honggang from Xiamen University, in collaboration with Professor Huang Yunhui's team from Huazhong University of Science and Technology, has for the first time observed concentration-driven phase separation at the electrode/electrolyte interface in real time at the nanoscale using a self-developed electrochemical in situ liquid-phase transmission electron microscopy device. This reveals the formation and evolution of a high-concentration lithium polysulfide interfacial layer in lithium-sulfur batteries. The findings were published in the journal Nature.
Lithium-sulfur batteries are considered an important system for next-generation high-specific-energy energy storage devices. However, under conditions close to practical applications, such as high sulfur loading and lean electrolyte, the microscopic reaction mechanisms inside the battery have long been difficult to observe and explain, limiting improvements in energy density, fast-charging performance, and cycling stability. The research team overcame the limitations of traditional observation methods by using electrochemical in situ liquid-phase transmission electron microscopy to achieve high-resolution real-time dynamic imaging of such interfacial reactions.
The observations revealed that during the discharge process, lithium polysulfides continuously accumulate at the electrode interface and undergo phase separation, forming a high-concentration interfacial layer rich in ion clusters. This establishes two pathways for lithium sulfide deposition: one involves charge transfer reactions on the electrode surface followed by deposition, and the other involves charge transfer in the electrolyte followed by deposition and growth. These two pathways jointly determine the efficiency and stability of the sulfur conversion reaction in lithium-sulfur batteries.
Based on these findings, the team proposed an optimization strategy for material design and interface regulation in high-specific-energy, fast-charging lithium-sulfur batteries. This involves rationally controlling the concentration of lithium polysulfides, sulfur content, and electrode interface structure to establish a balance between surface-mediated nucleation and solution-mediated growth, thereby achieving efficient sulfur conversion and enhancing battery performance. This study reveals the formation mechanism of micron-thick lithium sulfide deposition layers, providing a new scientific basis for designing next-generation high-energy-density, fast-charging, and long-life energy storage devices.
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