N‐Doping and Defective Nanographitic Domain Coupled Hard Carbon Nanoshells for High Performance Lithium/Sodium Storage

Abstract

Hard carbons (HCs) possess high lithium/sodium storage capacities, which however suffer from low electric conductivity and poor ion diffusion kinetics. An efficient structure design with appropriate heteroatoms doping and optimized graphitic/defective degree is highly desired to tackle these problems. This work reports a new design of N-doped HC nanoshells (N-GCNs) with homogeneous defective nanographite domains, fabricated through the prechelation between Ni 2+ and chitosan and subsequent catalyst confined graphitization. The as-prepared N-GCNs deliver a high reversible lithium storage capacity of 1253 mA h g −1 , with outstanding rate performance (175 mA h g −1 at a high rate of 20 A g −1 ) and good cycling stability, which outperforms most state-of-the-art HCs. Meanwhile, a high reversible sodium storage capacity of 325 mA h g −1 is also obtained, which stabilizes at 174 mA h g −1 after 200 cycles. Density functional theory calculations are performed to uncover the coupling effect between heteroatom-doping and the defective nanographitic domains down to the atomic scale. The in situ Raman analysis reveals the "adsorption mechanism" for sodium storage and the "adsorptionintercalation mechanism" for lithium storage of N-GCNs.

Defect Engineering on Electrode Materials for Rechargeable Batteries

“…For example, Zhao and co‐workers prepared N‐doped hard carbon nanotube shells with a specific graphitization/defect degree (N‐GCNs). By prechelating Ni 2+ ions with chitosan carbon sources, the catalyst‐bound graphitization process is possible, thus ensuring uniform distribution of nanographite domains . This unique structure leads to a large number of nanopores in the graphitized domain, and the stable charge storage can be achieved by interlaminar intercalation and interfacial adsorption.…”

Catalytic Synthesis of Hard/Soft Carbon Hybrids with Heteroatom Doping for Enhanced Sodium Storage

“…This phenomenon can be ascribed to the fierce chemical reactions occurring between HNO 3 and hard carbon. The successful doping is also indicated by the FTIR spectrum, where typical C−N, C−O and C=O peaks can be found at 1310, 1380 and 1700 cm −1 , respectively (Figure S4) ,…”

“…As shown in Figure S5 and Table S4, the electrochemical impedance spectra (EIS) data for the as‐prepared samples (the equivalent electronic circuits is shown in Figure S6) indicates that samples Fe0.25H, Fe1.00H and Fe2.00H have a tiny ion transfer resistance, which is attributed to their porosity structure, which enables better accessibility between the active sites and Na + . In addition, as for hard/soft carbon hybrids with oxidation, heteroatom‐doping and the structure of the defective nanographitic domains have been reported, with the help of DFT calculation, to show a synergistic effect for enhancing the binding ability for Na + and the charge transfer ability, which thus enhances the charge transport kinetics in composites with improved rate capability . Due to this synergistic effect, sample Fe0.25H shows the lowest charge transfer resistance in EIS.…”

“…In contrast, with increasing oriented domains in hard carbon, the functional group content is changed by the oxidation, as shown in Table S2 and Table S3. Nitrogen mainly occurs as pyridinic N, pyrrolic N and graphitic N. The pyridinic N and pyrrolic N can benefit Na storage by adsorbing Na + , and the graphitic N can spur electron conduction of the carbon material ,. The content of graphitic nitrogen gradually decreases with the increase in oriented domains, while the content of pyridinic N and pyrrolic N increases.…”

Porous carbon nanospheres with moderately oriented domains for EDLC electrode

“…Apparently, this method is a high‐energy consumption process. Catalytic graphitization generally occurs at a temperature of about 900°C as well and the extra pickling process is obligatory to get rid of the catalysts . Given these reasons, it is worth searching a low‐energy and simple means to achieve moderate orientation of carbon microcrystalline structures.…”