Tailoring 2D Heteroatom‐Doped Carbon Nanosheets with Dominated Pseudocapacitive Behaviors Enabling Fast and High‐Performance Sodium Storage

Abstract

2D carbon nanosheets are considered to be promising candidates for use as sodium ion battery (SIB) anodes due to their large specific surface area and excellent electronic conductivity. However, their applications are hampered by inferior cycling performance, insufficient storage capacity, and high cost. N, B co‐doping carbon nanosheets (NBTs) are synthesized using biomass‐based gelatin as carbon precursor and boric acid as template, and demonstrate their great potential as high‐performance SIB anodes in practical applications. The synergistic effect of heteroatom doping and ultrathin 2D structure provides the NBTs with abundant defects, active sites, and short ion/electron transfer distance, which favors and improves the storage capabilities and rate performances. The optimized NBTs present a remarkable cyclability and superb rate capability (309 mAh g−1 at 0.2 A g−1 for 200 cycles; 225 mAh g−1 at 1 A g−1 for 2000 cycles). Meanwhile, the Na storage mechanism is proved to be a pseudocapacitive‐controlled process, which accounts for the fast charge/discharge behaviors. This work demonstrates an effective template method to produce 2D heteroatoms co‐doping carbon nanosheets to achieve excellent Na storage performances.

A Reanalysis of the Diverse Sodium Species in Carbon Anodes for Sodium Ion Batteries: A Thermodynamic View

“…[105,106] Recently, Jin et al reported the successful synthesis of N, B co-doping 2D carbon nanosheets (NBTs) using H 3 BO 3 as templates and low-cost gelatine as carbon precursors (Figure 13a). [31] The 2D nanosheet structure and heteroatom doping was shown to be beneficial to improve the electrode/electrolyte contact, created defects, and active sites for Na + adsorption and thus achieved improved storage capacity (309 mAh g −1 at 0.2 A g −1 for 200 cycles), excellent rate performance (192 mAh g −1 at 10 A g −1 ), and an already acceptable cyclability (225 mAh g −1 for 200 cycles at 1 A g −1 ). The sodium storage mechanism was also studied using ex situ X-ray diffraction (XRD) measurements at different states during first charge/discharge process.…”

“…[1][2][3][4][5] Rechargeable lithium-ion batteries (LIBs) as one of the state-of-the-art conductivity, and breaking graphitic packing. [30][31][32] The overall performance is, however, still not remarkable, and to achieve high capacity, stable cycling, and high Coulombic efficiency (CE) simultaneously from the first cycle is very difficult. Therefore, an in-depth understanding of the interaction processes toward the sodium storage in hard carbonbased anodes is highly profitable and in our opinion, the most promising way to resolve the current contradictious situation.…”

“…c) The capacitive and diffusion contribution ratios for NBT700 at different scan rates. Reproduced with permission [31]. Copyright 2020, Wiley-VCH.…”

Understanding the improved performance of sulfur‐doped interconnected carbon microspheres for Na‐ion storage

“…To further improve Na-ion storage performance, another valid strategy is doping heteroatom to decorate the surface and structure of hard carbon, which can effectively enhance its electrical conductivity. [19][20][21][22][23][24] Among all the heteroatoms, sulfur doping in hard carbon could lead to an increase of lattice distance, which is in favor of the effective insertion and extraction of Na ion. Li et al 25 designed sulfur-doped disordered carbon by pyrolysis of precursor in sulfur steam, leading to excellent reversibility for Na-ion storage (271 mAh g -1 at 1 A g -1 after 1000 cycles).…”

Construction of Nitrogen-Doped Carbon Nanosheets for Efficient and Stable Oxygen Reduction Electrocatalysis

“…26,27 Secondly, carbon nanosheets have been explored as electrochemical active materials in the field of electrocatalysis due to their large surface area, superior mechanical/chemical stability and electronic properties. [28][29][30] Carbon sheets with edges have been studied as a model structure for hosting various ORR active sites. [31][32][33] The optimized twodimensional structure can provide excellent accessibility for reactants and products, thereby markedly enhancing mass transport efficiency.…”