Defect‐Rich Soft Carbon Porous Nanosheets for Fast and High‐Capacity Sodium‐Ion Storage

Abstract

Soft carbon has attracted tremendous attention as an anode in rocking‐chair batteries owing to its exceptional properties including low‐cost, tunable interlayer distance, and favorable electronic conductivity. However, it fails to exhibit decent performance for sodium‐ion storage owing to difficulties in the formation of sodium intercalation compounds. Here, microporous soft carbon nanosheets are developed via a microwave induced exfoliation strategy from a conventional soft carbon compound obtained by pyrolysis of 3,4,9,10‐perylene tetracarboxylic dianhydride. The micropores and defects at the edges synergistically leads to enhanced kinetics and extra sodium‐ion storage sites, which contribute to the capacity increase from 134 to 232 mAh g−1 and a superior rate capability of 103 mAh g−1 at 1000 mA g−1 for sodium‐ion storage. In addition, the capacitance‐dominated sodium‐ion storage mechanism is identified through the kinetics analysis. The in situ X‐ray diffraction analyses are used to reveal that sodium ions intercalate into graphitic layers for the first time. Furthermore, the as‐prepared nanosheets can also function as an outstanding anode for potassium‐ion storage (reversible capacity of 291 mAh g−1) and dual‐ion full cell (cell‐level capacity of 61 mAh g−1 and average working voltage of 4.2 V). These properties represent the potential of soft carbon for achieving high‐energy, high‐rate, and low‐cost energy storage systems.

Effect of Intrinsic Defects of Carbon Materials on the Sodium Storage Performance

“…In addition, the D‐band can be fitted to four bands (Table S3, Supporting Information) . For DT‐C, the fitted curves show a significant improvement of the D1 band, corresponding to the more exposed edges on the carbon layer due to the dual templates assisted synthesis method . The calculated I D1 / I G ratio of DT‐C is 1.16, which is higher than that of HT‐C (1.09) and NT‐C (0.98).…”

“…The change of defect degree is owing to the generation of irregular lattice brought by the templates. In addition, the D‐band can be fitted to four bands (Table S3, Supporting Information) . For DT‐C, the fitted curves show a significant improvement of the D1 band, corresponding to the more exposed edges on the carbon layer due to the dual templates assisted synthesis method .…”

“…It has been discovered that intrinsic carbon defects can enhance the electrocatalytic performance of carbon‐based electrocatalysts toward oxygen reduction, carbon dioxide reduction, oxygen evolution, and hydrogen evolution reactions . Although it is reported that the construction of carbon materials with defects may have effect on the sodium storage behavior, the related sodium storage mechanism deserves further study . Especially, there is still a lack of detailed characterization and theoretical explanation for the effects of carbon defects (intrinsic defects) on sodium storage performance.…”

Defect Engineering on Electrode Materials for Rechargeable Batteries

“…For instance, Mai and co‐workers prepared microporous soft carbon nanosheets by microwave induced exfoliation. Structural characterization results showed that the surface area increased after exfoliation with the volume of micropores increased by more than 100 times, and the favorable defects on the edge of graphene layer were significantly increased . Due to the synergism‐enhanced kinetics and additional sodium storage sites provided by the micropores and defects at the edges, this material has high rate capacity.…”

Recent research progresses in ether‐ and ester‐based electrolytes for sodium‐ion batteries

“…In addition, the use of aluminum, instead of copper, for the negative current collectors in SIBs, can significantly reduce the whole weight of batteries and as a result effectively increase the energy density of batteries. On the basis of these advantages, a variety of advanced cathodes and anodes with delicately designed morphology and compositions have been successfully developed for SIBs, many of which now have been proven to have huge potential for commercial application …”