Quantum‑size FeS2 with delocalized electronic regions enable high‑performance sodium‑ion batteries across wide temperatures

As the demand for sustainable and low-cost energy storage grows, sodium-ion batteries (SIBs) have emerged as a promising alternative to lithium-ion systems. However, their performance under extreme temperatures remains a major hurdle. Now, researchers from China University of Mining and Technology, led by Professor Danyang Zhao and Professor Yanwei Sui, have developed a breakthrough anode material—quantum-sized FeS₂ anchored on 3D MXene—that delivers exceptional sodium storage performance from −35 °C to 65 °C.

Why This Innovation Matters

• Wide-Temperature Operation: The FeS₂ quantum dot (QD)/MXene anode maintains high capacities of 255.2 mAh g^-1 at −35 °C and 424.9 mAh g^-1 at 65 °C, enabling reliable battery performance in extreme environments.
• Fast Ion Transport: Quantum confinement creates delocalized electronic regions and abundant edge defects, significantly reducing Na⁺ diffusion barriers and enhancing reaction kinetics.
• High Energy Density: When paired with Na₃V₂(PO₄)₃ cathode, the full cell achieves a record energy density of 162.4 Wh kg^-1 at −35 °C, outperforming most reported wide-temperature SIBs.

Design Highlights

• Quantum-Size Engineering: Ultra-small FeS₂ QDs (5–8 nm) maximize edge atom exposure, promoting charge delocalization and pseudocapacitive behavior without compromising structural integrity.
• 3D MXene Skeleton: Ti₃C₂ MXene forms a robust, conductive scaffold via Fe–O–Ti bonding, preventing QD aggregation and accommodating volume changes during cycling.
• Strong Interfacial Coupling: X-ray absorption and Raman spectroscopy confirm Ti–O–Fe bonds and charge redistribution, which enhance electronic conductivity and stabilize the active material.

Performance and Outlook

• Long-Term Stability: The anode retains 370.1 mAh g^-1 after 2500 cycles at 1 A g^-1, demonstrating superior cycling durability across temperatures.
• Fast Charge/Discharge: Pseudocapacitive contributions dominate (up to 77%), enabling rapid Na⁺ storage and high-rate capability.
• Scalable Strategy: The ion-induced self-assembly method is extendable to other transition metal sulfides (e.g., CoS₂, NiS₂), offering a universal route to high-performance SIB anodes.

This work introduces a powerful strategy to harness quantum-size effects for wide-temperature energy storage, paving the way for durable, high-energy sodium-ion batteries in aerospace, electric vehicles, and grid systems. Stay tuned for more innovations from Professor Zhao and Professor Sui’s team!