Li–O₂ batteries are considered promising next-generation energy-storage systems because their theoretical specific energy approaches 3,500 Wh kg⁻¹. Their practical development, however, remains restricted by poor cycling stability, low round-trip efficiency, limited high-rate performance, and large charging overpotentials. These problems arise mainly from electrically insulating and insoluble Li₂O₂, which accumulates during discharge, blocks electrode pores, passivates catalytic surfaces, and hinders mass and charge transport. Large toroidal Li₂O₂ particles can provide high capacity but are difficult to decompose, whereas more easily decomposed flower-like or film-like products generally cause rapid surface passivation and lower capacity. A central challenge is therefore to coordinate pore-level transport and catalytic activity to overcome this capacity–polarization trade-off.
A study (DOI: 10.48130/scm-0026-0016) published in Sustainable Carbon Materials on 21 April 2026 by Ying Yao's team, Beijing Institute of Technology, reports that coupling large mesopores with abundant pyridinic-nitrogen sites enables high-capacity toroidal Li₂O₂ growth without the severe charging polarization usually associated with this discharge morphology.
To create the catalysts, the researchers synthesized zeolitic imidazolate framework-7 precursors in three solvents—N,N-dimethylformamide, deionized water, and methanol—under vacuum-assisted heating, followed by pyrolysis at 950 °C under nitrogen. The resulting carbon materials, designated ZDC, ZWC, and ZMC, differed in their pore structures and surface nitrogen configurations. The team characterized their morphology, porosity, chemical composition, and structural properties using electron microscopy, nitrogen adsorption–desorption analysis, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. ZDC contained pores spanning approximately 3–30 nm and nearly 35% pyridinic nitrogen, while ZWC possessed the largest surface area but only 11.73% pyridinic nitrogen. ZMC had abundant pyridinic nitrogen but lacked larger mesoporous transport channels. These materials were then incorporated into cathodes and evaluated in Li–O₂ cells using cyclic voltammetry, galvanostatic cycling, electrochemical impedance spectroscopy, and discharge-product analysis. At 100 mA g⁻¹, ZDC delivered 21,395 mAh g⁻¹, substantially exceeding the 13,719 mAh g⁻¹ obtained with ZWC and 3,225 mAh g⁻¹ with ZMC. ZDC also showed the lowest discharge and charge overpotentials, approximately 0.21 and 0.77 V, respectively. Its cycling life exceeded 2,500 hours, compared with 1,250 hours for ZWC and 800 hours for ZMC. Even at 1,000 mA g⁻¹, the optimized cathode retained stable cycling and a charge overpotential of about 0.90 V. Microscopy revealed toroidal Li₂O₂ on ZDC and ZWC but flower-like deposits on ZMC. Although toroidal Li₂O₂ is normally associated with difficult oxidation, the ZDC cathode decomposed it at a lower overpotential than ZMC required for its flower-like deposits. The researchers attributed this behavior to complementary functions: mesopores larger than 6 nm sustained oxygen and lithium-ion transport and preserved access to active surfaces, while electron-rich pyridinic-nitrogen sites lowered the kinetic barrier for Li₂O₂ decomposition. Together, these features prevented pore blockage and maintained reversible electrochemical reactions over extended cycling.
Overall, the study shows that battery performance depends not simply on maximizing surface area or catalytic-site concentration, but on coordinating transport pathways with chemically active sites. The optimized ZDC catalyst combines sufficient space for discharge-product storage, efficient reactant transport, and rapid Li₂O₂ decomposition, thereby reconciling high capacity with low polarization and prolonged cycling. Although further studies are required to assess practical cell configurations, long-term stability, and scalability, the dual-modulation approach provides a general materials-design strategy for developing efficient porous carbon cathodes for metal–oxygen batteries.
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References
DOI
10.48130/scm-0026-0016
Original Source URL
https://doi.org/10.48130/scm-0026-0016
Funding information
The use of the Swagelok cell was supported by Cunzhong Zhang at the Beijing Institute of Technology.
About Sustainable Carbon Materials
Sustainable Carbon Materials (e-ISSN 3070-3557) is a multidisciplinary platform for communicating advances in fundamental and applied research on carbon-based materials. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon materials around the world to deliver findings from this rapidly expanding field of science. It is a peer-reviewed, open-access journal that publishes review, original research, invited review, rapid report, perspective, commentary and correspondence papers.