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Abstract Intermittent renewable energy sources can mitigate climate change, but they require high-performance, reliable batteries. The widely used lithium-ion batteries contain Li, Co, and Ni, and the growing demand for these elements, together with their relatively limited sources, has raised concerns about their supply chain stability. Sodium-ion batteries have become an economical alternative. Sodium vanadium phosphate, Na3V2(PO4)3 (NVP), is a compelling candidate with high stability and ionic conductivity due to its polyanionic sodium superionic conductor (NASICON) structure. However, NVP suffers from poor electronic conductivity and requires hierarchical morphology to allow facile ion and electron transfer. Spray-drying has been used to achieve hierarchical secondary particle structures, but the foremost reported NVP syntheses rely on either flammable/toxic organic solvents or expensive nanocarbon additives. In this study, we spray-dry an aqueous suspension without using expensive carbon additives. The obtained NVP sodium-ion half cells showed very high reversible capacity (114.7 mAh g-1 at 0.2C), high rate capability (80.8% capacity retention at 30C), and stable cycling performance (96.7% capacity retention after 1,500 cycles at 10C). This superior performance demonstrates the great promise for NVP batteries as an alternative energy storage option to traditional lithium-ion batteries. 

Abstract Electrochemical energy systems rely on particulate porous electrodes to store or convert energies. While the three‐dimensional (3D) porous structures are introduced to maximize the interfacial area for better overall performance of the system, spatiotemporal heterogeneities arising from materials thermodynamics are localizing the charge transfer processes onto a limited portion of the available interfaces. Here, a simple but precise method is demonstrated to directly track and analyze theoperando(i.e., local and working) interfaces on the mesoscale in a practical graphite porous electrode to obtain the true local current density, which turns out to be two orders of magnitude higher than the globally averaged current density adopted by existing studies. The results shed light on the long‐standing discrepancies in kinetics parameters derived from electroanalytical measurements and from first principle predictions. Contradictory to prevailing beliefs, the electrochemical dynamics are not controlled by the solid‐state diffusion process once the spatiotemporal reaction heterogeneities emerge. 

To address the dynamic heterogeneities in porous carbon electrode used in Li-O2 batteries, microscopic charge transfer theory offers much better explanations and predictions for the reactive nucleation and growth dynamics of oxide formation during discharging a Li-O2 battery.