Review: Insight on Porous Carbon Positive Electrode for Sodium-Ion Capacitors: Interplay Between Synthesis,...

Sodium ion capacitors (SICs) represent a major advancement in the field of energy storage technology. SICs combine the high energy of batteries with the high power of capacitors by pairing battery-type (negative) and capacitor-type (positive) electrodes, offering a cost-effective alternative to lithium-based systems. Since its inception in 2012, numerous research works have focused on the optimization of electrode materials, particularly the porous carbons (PCs) positive electrode material. PCs such as activated carbons are mostly adopted thanks to their good compatibility with high potential windows. However, the commercial viability of SICs is currently being limited by the low discharge capacity of the activated carbon positive electrode. This review provides an in-depth analysis of how synthesis properties impact porous carbon properties (morphology, porosity, structure and surface chemistry), drawn from literature findings from comprehensive databases. It further establishes the synthesis-property correlation with the electrochemical performance of PCs in Na metal half-cell. Also, the charge storage mechanisms as related to capacitive and pseudo-capacitive mechanisms were extensively examined. Additionally, pre-sodiation strategies for building dual-carbon SIC full cells are discussed, alongside the performance of PCs incorporating various carbon-based negative electrode materials. Finally, it addresses the challenges and opportunities in improving PC performance toward SIC commercialization.