Unveiling the Confined Space Charge Storage Mechanism in Vanadium Chalcogenides/Carbon Mixed Conductor Interface for...

Vanadium chalcogenides demonstrate exceptional electrochemical performance as anode candidates for potassium-ion batteries (PIBs) applications, yet their reaction mechanism, whether governed solely by intercalation or intercalation-conversion processes, has remained controversial. Herein, the dual charge storage mechanism in VSSe@C is unveiled, combining K⁺ intercalation and interfacial supercapacitive space charge storage mechanism. The abundant VSSe/carbon interfaces within the confined space in the carbon nanofiber are directly captured by 3D electron microscopy, and this rich interface enables decoupled electron transport (via carbon) and potassium ion (K⁺) transport (via VSSe), triggering interfacial supercapacitive space charge storage mechanism in addition to the K⁺ intercalation. This dual mechanism endows the VSSe electrode to achieve a reversible specific capacity of 309 mAh g^-1 with negligible volumetric expansion (0.86%) and no phase degradation. Benefiting from these features, the ultrahigh stability for over 5000 cycles with a capacity retention of 83.3% at 2 A g^-1 is demonstrated, and the application of VSSe@C in the potassium pouch cell with perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) cathode is further validated. This work highlights extra charge storage mechanisms in the mixed ion/electron conductor interface, emphasizing the critical role of interfacial engineering in unlocking high-performance durable energy storage systems.