Although great progress has been made in carbon anodes for potassium-ion batteries, the development of advanced carbon anodes with fast reaction kinetics and high cycle stability is still a great challenge due to the large radius of K + (0.138 nm). In this work, novel ultrathin carbon nanosheets (UCNs) fabricated by vapor-induced bubbling strategy are reported to address current challenge. The results show that the UCNs are composed of 3D interconnected 30 nm-thick sheet units with well-developed hierarchical micro-/meso-/macro-pores, which can not only increase the contact area between electrode/electrolyte, but also effectively buffer the volume expansion caused by the (de)potassiation. In addition, UCNs have a carbon composite structure of intertwined pseudo-graphite domains and amorphous carbon domains, providing abundant storage active sites and fast transport channels for K + . Specifically, the UCN-1300 delivers a K + storage capacity of ≈350 mAh g −1 at a current density of 0.05 A g −1 . Moreover, it presents excellent cycle stability, maintaining a capacity of 120 mAh g −1 after 5000 cycles at a current density of 5 A g −1 , with a capacity retention rate of more than 99%. In prior reports, carbon anodes demonstrating such a high K + storage capacity and outstanding cycle stability are rarely obtained.
Carbon materials with defect-rich structure are highly demanded for various electrochemical scenes, but encountering a conflict with the deteriorative intrinsic conductivity. Herein, we build a highway-mediated nanoarchitecture that consists of the ordered pseudographitic nanodomains among disordered highly nitrogen-doped segments through a supramolecular self-assembly strategy. The “order-in-disorder” nanosheet-like carbon obtained at 800 °C (O/D NSLC-800) achieves a tradeoff with high defect degree (21.9 at% of doped nitrogen) and compensated electrical conductivity simultaneously. As expected, symmetrical O/D NSLC-800 electrodes exhibit superior capacitive deionization (CDI) performance, including brackish water desalination (≈82 mg NaCl g −1 at a cell voltage of 1.6 V in a 1000 mg L −1 NaCl solution) and reusage of actual refining circulating cooling water, outperforming most of the reported state-of-the-art CDI electrodes. The implanted pseudographitic nanodomains lower the resistance and activation energy of charge transfer, which motivates the synergy of hosting sites of multiple nitrogen configurations. Our findings shed light on electrically conductive nanoarchitecture design of defect-rich materials for advanced electrochemical applications based on molecular-level modulation.
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