Edge-oxidation-induced densification towards hybrid bulk carbon for low-voltage, reversible and fast potassium storage

Abstract

• An edge-oxidation-induced densification route was proposed to fabricate the bulk carbon with hybrid structure of both nanographitic domains and defect networks. • Fast and reversible K + intercalation can be ensured in sp 2 /sp 3 hybridized bulk structure, which is the key to enable carbon anodes with low charge voltage, high ICE, high-rate capability and excellent cyclic stability simultaneously. • The BC-2H//KPB full cell demonstrates great potential for high-performance potassium storage. Bulk carbon with high charge capacity at low voltage, high initial coulombic efficiency (ICE) and high-rate is critical but challenging for the practice utilization of potassium-ion batteries (PIBs). Herein, an edge-oxidation-induced densification strategy is reported to construct hybrid bulk carbon, in which the edge-oxygen of oxidized pitch serves as the cross-linking agent to in-situ conduct the densification. The nanographitic domains are constructed by the localized carbonization of aromatic hydrocarbon core, serving as low voltage intercalation sites. Meanwhile, the removal of oxygen groups builds bulk defect networks around nanographitic domains, thus ensuring fast K + diffusion kinetics. The hybrid bulk carbon anode performances high reversible capacity below 1 V (248.8 mAh g −1 at 0.05 A g −1 ), high ICE (68.2%), high-rate (209.9 mAh g −1 at 1 A g −1 ) and superior cyclic stability (90% capacity retention in 4000 cycles). Moreover, the full cell shows a significant discharge plateau at ca. 3.2 V and excellent cyclic stability (97% from cycle 10th to 200th). This work provides a rational and facile strategy to realize the tradeoff between K + intercalation and fast diffusion kinetics for practical application of PIBs, and gives deep insights into the mechanism of fast and reversible potassium storage at low voltage. An edge-oxidation-induced densification strategy is reported to construct sp 2 /sp 3 hybridized bulk carbon, in which the edge-oxygen of oxidized pitch serves as the cross-linking agent to in-situ conduct the densification. The nanographitic domains and defect networks in hybrid carbon materials is efficient to boost the low voltage potassium storage capacity, ICE, rate performance and long-term cyclic stability simultaneously.