Solid–Solid Interfacial Charge Storage of Prussian Blue/rGO Mixed-Conductor Cathode for High-Power Na Ion Batteries

For the cathode materials potentially available for high power capability, reducing their particle size can improve the bulk ionic conductivity due to reduced ion diffusion length, and exploiting new reaction mechanisms must be fundamentally advantageous. However, other issues such as synthesis difficulty, poor charge-storage stability, and capacity decay can emerge. To simultaneously address these issues, in this work, we discover a reversible solid–solid interfacial storage in the space-charge region of ultrafine Prussian blue analogues (PBAs)/reduced graphene oxide (rGO), a mixed ion/electron conductor through a so-called "job-sharing" mechanism. This mechanism shows that electrons and ions can be stored in the different phases around the interface and transport only inside there, which looks thermodynamically distinct from most conventional charge-storage mechanisms in terms of the relationship between charge storage and cell voltage. The insertion cathodes governed by the job-sharing mechanism thus exhibit outstanding performance with high capacity, fast kinetics, and stable cyclability.