Edge-Nitrogen-Rich Carbon Dots Pillared Graphene Blocks with Ultrahigh Volumetric/Gravimetric Capacities and Ultralong Life for Sodium-Ion Storage

The development of stable electrode materials for sodium-ion batteries (NIBs) with excellent rate capacity, high volumetric/gravimetric capacity, and ultralong-term cycling stability still remains a challenge. Herein, a novel strategy for the synthesis of edge-nitrogen-rich carbon dots pillared graphene blocks (N-CDGB) through self-polymerization of aniline into graphene oxide blocks, and subsequent carbonization is developed. Due to high bulk density (1.5 g cm −3 ) and integrated lamellar structure with large edge-interlayer spacing (4.2 Å) pillared by nitrogen-doped carbon dots (95% edge-nitrogen content), the dense N-CDGB shows robust structural stability, fast ion/electron transfer pathways, and more active sites for sodium storage. As a result, the N-CDGB electrode exhibits ultrahigh reversible volumetric and gravimetric capacities (780 mAh cm −3 /520 mAh g −1 at 0.02 A g −1 ) far exceeding those of graphene (108 mAh cm −3 /290 mAh g −1 ) and hard carbon (297 mAh cm −3 /311 mAh g −1 ), excellent rate capability (118 mAh g −1 /177 mAh cm −3 at 10 A g −1 ), and superior cycling stability up to 10 000 cycles with almost no capacity loss at 10 A g −1 . This work signifies the superiority of densely pillared structure in the future development of NIBs with high volumetric/gravimetric capacity and ultralong-term cycling stability.