As the global pursuit of next-generation energy storage intensifies, lithium–sulfur (Li–S) batteries have long tantalized researchers with their exceptional theoretical specific energy of 2600 Wh kg -1 and the natural abundance of sulfur. Yet the journey from laboratory promise to commercial reality has been persistently blocked by the notorious shuttle effect of soluble lithium polysulfides (LiPSs) and sluggish sulfur redox reaction kinetics. Now, researchers from the National University of Defense Technology, Changsha University of Science and Technology, and National University of Singapore, led by Professor Chunman Zheng and Professor Weiwei Sun, have unveiled a paradigm-shifting strategy that challenges the conventional obsession with maximizing catalyst activity alone.
Why This Host Architecture Matters
Prevailing research has overwhelmingly concentrated on engineering highly active electrocatalysts—from metallic compounds and complex heterojunctions to single-atom sites—operating under the implicit assumption that the conductive host matrix merely provides electron pathways and physical confinement. However, this catalyst-centric approach neglects a critical electrochemical reality: within a confined nanoreactor, accelerated reaction kinetics near a highly active catalyst inevitably cause rapid local consumption of reactants and generation of high-concentration LiPSs, creating severe spatial heterogeneity analogous to "local concentration polarization." Under practical lean electrolyte conditions, this leads to electrolyte depletion, LiPSs accumulation, and ultimately the passivation of catalytic sites and formation of inactive "dead sulfur." The full potential of even intrinsically superior catalysts may never be realized as their local microenvironment becomes progressively poisoned.
The novel double-shell hollow Prussian blue analogue derivative (Co 2.5 Fe/NC) overcomes this fundamental limitation by shifting the design paradigm from solely pursuing catalytic activity to intelligently managing the electrochemical microenvironment through host architecture engineering.
Innovative Design and Mechanism
The material is synthesized through a facile, one-step ion-exchange strategy by precisely controlling the Co/Fe molar ratio at 2.5, strictly avoiding complex and corrosive template-etching processes. Finite element simulations and in situ diagnostics reveal that the double-shell structure uniquely orchestrates a self-propelled convective electrolyte flow within its nanoreactor cavity during operation. This dynamic flow actively transports polysulfides away from the catalyst surface, effectively mitigating spatial concentration heterogeneity of LiPSs—especially near the catalysts—thereby preventing active material passivation and ensuring sustained high catalytic efficiency. The double-shell architecture establishes higher overall reaction potential and current density, with particularly elevated reactivity at edges and apexes, accelerating reaction kinetics while firmly confining LiPSs within the framework.
Outstanding Performance
Remarkably, even with a catalyst of only moderate intrinsic activity, the Co 2.5 Fe/NC cathode dramatically outperforms its more active single-shell counterpart (Co 2 Fe/NC). It achieves exceptional cycling stability with merely 0.016% capacity decay per cycle over 1000 cycles at 2C under lean electrolyte conditions (E/S ratio ≈ 12), delivering 84.4% capacity retention. The cathode exhibits a high specific capacity of 1294.25 mAh g -1 at 0.2C and maintains 676.42 mAh g -1 even at 4C, demonstrating substantially augmented rate performance. In situ Raman spectroscopy confirms significantly suppressed LiPSs shuttle signals, while in situ EIS and DRT analysis reveal virtually no discernible LiPSs diffusion impedance in the double-shell structure. Li 2 S nucleation evolves from 2D to 3D instantaneous growth patterns, promoting uniform, dense deposits. Under high areal sulfur loadings (3.1–7.8 mg cm -2 ) with depleted electrolyte, the material delivers areal capacities exceeding conventional intercalation cathodes.
Applications and Future Outlook
Most critically, an Ah-level pouch cell assembled with the Co 2.5 Fe/NC cathode achieves a groundbreaking energy density of 454.7 Wh kg -1 (380.5 Wh kg -1 including all packaging components) under demanding conditions (E/S = 3.1 μL mg -1 , N/P = 1.34), with stable cycling for nearly 20 cycles at 40 mA g -1 . This performance significantly surpasses previously reported Li–S pouch cells across all key metrics including sulfur content, E/S ratio, areal loading, and N/P ratio. This work establishes "host-structure-induced microenvironment regulation" as a powerful design principle, opening promising avenues for practical high-energy-density Li–S batteries by reconceptualizing the sulfur host from a passive scaffold to an active microenvironment regulator.
Stay tuned for more groundbreaking research from this collaborative team at the National University of Defense Technology, Changsha University of Science and Technology, and National University of Singapore!
Nano-Micro Letters
News article
Engineering Dynamic Electrolyte Microenvironments via Double-Shell Hosts for Practical Lithium–Sulfur Batteries
22-Jun-2026