Abstract
Heteroatom doping, which has long been considered as one of the most efficient approaches to significantly enhance the sodium storage ability of carbonaceous anodes, has drawn increasing attention. Compared with single doping, dual doping can introduce more defects and accelerate ionic diffusion. In addition, the synergistic effect between the dual doped atoms can significantly improve the electrochemical performances. Besides, exploring novel precursors with excellent properties, which can induce porous structure and rapid pathways for electrons/ions in the resultant carbonaceous anode, is still full of challenges. Herein, nitrogen and sulfur–co-doped urchin-like porous carbon (NSC) was fabricated through a combined strategy including carbonization and subsequent sulfidation, using covalent organic frameworks (COFs) as precursors. Because of the dual doping–endowed rich defects, high electronic conductivity, and favorable capacitive behavior, the resultant NSC exhibited excellent sodium storage performances, delivering superior sodium storage capacity (483.5 mAh g−1 at 0.1 A g−1 after 100 cycles) and excellent cycling stability up to 1,000 cycles (231.6 mAh g−1 at 1.0 A g−1). Importantly, such remarkable electrochemical performances of the resultant carbonaceous anode may shed light on the efficient conversion of COFs to functional materials.
Highlights
Because of their excellent features including long life span, high energy density, and excellent stability, lithium-ion batteries (LIBs) have become the most successful commercial batteries, which have been widely applied in various portable electronics and electric vehicles
The further conversion from the covalent organic frameworks (COFs) to porous carbon doped with N and S was realized through subsequent carbonization and sulfidation (Li et al, 2018c)
The morphologies of the pure COFs, nitrogen and sulfur–co-doped urchin-like porous carbon (NSC)-500, NSC-600, and NSC-700 were observed through field-emission scanning electron microscopy (FESEM, Figures 1B–F), from where we can detect that the morphologies of NSC-500, NSC-600, and NSC-700 maintain well compared with their precursors after the carbonization and subsequent sulfidation process
Summary
Because of their excellent features including long life span, high energy density, and excellent stability, lithium-ion batteries (LIBs) have become the most successful commercial batteries, which have been widely applied in various portable electronics and electric vehicles. The COFs-induced urchin-like morphology and porous structure and stable inner structure, combining the heteroatoms doping induced favorable ionic/electronic conductivity and rich active sites, result in expressive sodium storage performance, showing great potential for the fabrication of high-performance SIBs. In a typical synthesis, 1,3,5-triformylphloroglucinol (63 mg), p-paraphenylenediamine (48 mg), 3 M aqueous acetic acid (0.5 ml), dioxane (1.5 ml), and mesitylene (1.5 ml) were mixed, which was added into a Pyrex tube. The structure characterizations of the as-prepared samples and electrochemical methods used in this work can be found in Supporting Information (SI)
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