Enhancement of Diffusion-Controlled Pseudocapacity in Biphasic NaMnO2 Electrodes for Sodium Batteries by Tailoring Structural and Morphological Properties

High Resolution Image Download MS PowerPoint Slide In this study, we present a biphasic (orthorhombic/monoclinic) NaMnO 2 material synthesized by using cheap and low-temperature sol–gel methods, which presents potential applications as an advanced cathode material for aqueous sodium-ion energy storage. By leveraging its unique structural and morphological properties, our approach optimizes the balance between diffusion-controlled and surface-controlled pseudocapacitive charge storage, significantly enhancing electrochemical performance with capacity values over 100 mAh/g. Electrochemical investigations reveal that the tailored morphology of NaMnO 2 allows for a high pseudocapacitive contribution, with the Na 2 SO 4 electrolyte exhibiting the most stable cycling behavior and the highest capacity retention. Ex-situ X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and X-ray photoemission techniques confirm both intercalation and surface pseudocapacitive reactions, highlighting the interplay between intercalation and adsorption processes. The calculated value of diffusion-controlled pseudocapacity contribution of about 55% enables superior charge storage capabilities and rapid charge/discharge rates. These findings establish biphasic NaMnO 2 as a promising, structured, stable electrode material for next-generation, high-performance, and robust sodium energy storage systems.