Engineering dynamic electrolyte microenvironments via double-shell hosts for practical lithium–sulfur batteries

Aiming at the severe shuttle effect of lithium polysulfides (LiPSs), sluggish kinetics of sulfur redox reactions, and easy passivation of local catalytic sites by high-concentration LiPSs in lithium–sulfur (Li–S) batteries, the research team led by Weiwei Sun and Chunman Zheng from National University of Defense Technology proposed a design concept of "host structure-induced dynamic microenvironment regulation of electrolyte". By constructing a double-shelled hollow Prussian blue analogue derivative as sulfur host, the synergistic optimization of LiPS concentration field, potential field and reaction kinetics is realized. A double-shelled hollow Prussian blue analogue-derived sulfur host material Co₂.₅Fe/NC was designed and fabricated. This work delivers a novel research paradigm for the sulfur cathode design of Li–S batteries and exhibits great potential for practical applications.

Lithium–sulfur (Li–S) batteries are regarded as promising candidates for next-generation high-energy-density energy storage systems due to their ultrahigh theoretical specific capacity and energy density. Nevertheless, their practical commercialization is plagued by numerous challenges, among which the most prominent ones include the shuttle effect of lithium polysulfides (LiPSs), sluggish sulfur redox kinetics, and low utilization of active materials under lean-electrolyte and high-sulfur-loading conditions. To tackle these obstacles, the research team breaks away from the conventional strategy that solely pursues high catalytic activity and proposes a sulfur host design based on double-shelled hollow Prussian blue analogue derivatives. By precisely tuning the Co/Fe molar ratio, a high-efficiency double-shelled hollow Co₂.₅Fe/NC sulfur host is synthesized, which constructs a dynamic electrolyte microenvironment. During charge and discharge, this architecture triggers self-driven electrolyte flow inside the nanoreactor, alleviating the local accumulation of lithium polysulfides near catalytic sites and thereby preventing catalyst poisoning and active material passivation. Benefiting from the synergistic homogenization of LiPS concentration and potential fields enabled by the double-shelled structure, the Co₂.₅Fe/NC cathode delivers outstanding cycling stability under lean-electrolyte conditions, with an ultralow capacity decay of only 0.016% per cycle over 1000 cycles at 2 C. Furthermore, the assembled Ah-level pouch cell achieves a remarkable energy density of 454.7 Wh kg⁻¹, demonstrating great prospects for practical applications.

This study proposes a sulfur host design strategy based on double-shelled hollow Prussian blue analogue derivatives and highlights the active regulatory effect of host architectures on the local electrochemical microenvironment of lithium–sulfur batteries. Compared with conventional approaches that merely pursue high intrinsic catalytic activity, this work demonstrates the great significance of host structure-induced microenvironment regulation. Even when the catalyst possesses moderate intrinsic activity, a rationally engineered double-shelled structure can deliver superior comprehensive electrochemical performance by optimizing the local reaction surroundings. This research not only offers an innovative structural modulation strategy for designing sulfur hosts in lithium–sulfur batteries, but also inspires researchers to pay more attention to the dynamic management of reaction microenvironments rather than only improving single material compositions or catalytic activity when investigating complex conversion-type battery systems.

Title:
Engineering Dynamic Electrolyte Microenvironments via Double-Shell Hosts for Practical Lithium–Sulfur Batteries
Journal Name: Nano-Micro Letters
DOI: https://doi.org/10.1007/s40820-026-02260-2 
URL: https://scholarcast.cast.org.cn/top-news/2078133470931316736