Sodium-ion batteries (SIBs) have received considerable attention as promising next-generation energy storage systems due to a large abundance of sodium and ion storage chemistry similar to that of lithium-ion batteries (LIBs). We report ultramicroporous hard carbon microspheres (HCMSs) derived from sucrose via a microwave-assisted solvothermal reaction as anode for SIBs. Because of the HCMSs with a larger interlayer spacing in graphitic domains and ultramicropores, it delivers excellent 3-RC features (reversible capacity, rate capability, and retention of capacity) reported to date for hard carbons derived from sugar-based carbon precursors through electrolyte optimization of carbonate esters (EC:PC, EC:DEC, EC:DMC). The HCMS-PC delivered the best reversible capacity of 265 mAh g −1 at a current density of 300 mA g −1 , showing 85.8% capacity retention after 100 cycles and 66.3% capacity retention after 500 cycles in a half-cell. A full-cell fabricated with an HCMS-PC anode and a Na 3 V 2 (PO 4 ) 3 cathode delivered reversible capacities of 81 and 48 mAh g −1 at current densities of 30 and 300 mA g −1 , respectively.

Novel detailed chemistry of WS2 synthesis.

Summary First‐generation sodium‐ion batteries (SIBs) are commercially launched by Faradion Ltd., UK, and HiNa Battery Technology Company Ltd., China, utilizing the transition metal oxide‐based cathodes. Currently, the commercial Faradion cells deliver ~1000 cycles at an energy density of ~140 to 150 Wh kg−1, whereas HiNa SIB cells deliver ~120 Wh kg−1. P2‐type, O3‐type, and composite P‐O and P‐P type transition metal oxide cathodes have generated much interest in the last few years. P2‐type layered oxides are critical as cathodes in achieving higher energy and power density in SIB technology, along with better C‐rate capabilities. Compared to their O3‐type counterparts, P2‐type layered transition metal oxides encounter lower activation energy barriers, enabling improved rate kinetics. However, P2‐type cathodes often face poor cycle stability due to undesirable phase changes during charge‐discharge cycles and structural instability to air and moisture. This review evaluates all the P2‐type layered oxide compounds as SIB cathodes, highlighting the strategies followed to meet the challenges and offers aspects of their successful commercialization.

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