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

Abstract

Hard carbon shows a promising application for sodium storage but suffers from low electrochemical stability, which leads to poor rate capacity and cycle life. Here, we report a heteroatom‐doping hard/soft carbon hybrid prepared by easy oxidizing acid treatment and low temperature catalytic graphitization. The heteroatoms increase the sodium‐ion adsorption capability during slope region, showing an important contribution at high current. Besides, the introduction of oriented domains enhances the conductivity, as well as the heteroatom doping, and electrochemical stability of hard/soft carbon hybrids. What's more, these structure characteristics also benefit the stable storage of sodium ions, supported by a 74% increase in terms of reversible capacity. Thus, the electrochemical performance retains a fast and reversible capacity of 125 mAh⋅g−1 at high current density of 8 C.

Hard Carbon Anodes: Fundamental Understanding and Commercial Perspectives for Na‐Ion Batteries beyond Li‐Ion and K‐Ion Counterparts

“…Graphite, SC, reduced graphene oxide (rGO), and CNTs have been reported to enhance the performance of HC anodes to some extent. [ 101 ] SC has been frequently reported to be effective for filling the open pores, decreasing the surface area, and enhancing the rate performance of HC. Hu and co‐workers reported the synthesis of an HC/SC composite with a mixture of pitch and phenolic resin as precursors, and the composite delivered an impressively high ICE of 88% and a high reversible capacity of 284 mAh g −1 in SIBs.…”

“…Codoping of HC with N,O or P,O can also be easily realized by HNO 3 ‐ or H 3 PO 4 ‐assisted pyrolysis of the precursors. [ 41a,110 ] Recently, a N,O‐codoped HC/SC composite was synthesized by Fe 3+ ‐assisted pyrolysis and then HNO 3 oxidation, [ 101a ] the product delivered high rate capacity in SIBs. Codoping of HC with P,O atoms has been realized by electrospinning of polyvinylpyrrolidone (PVP) with H 3 PO 4 and then pyrolysis, high reversible capacity of 393.4 mAh g −1 was achieved in PIBs.…”

A Promising Hard Carbon−Soft Carbon Composite Anode with Boosting Sodium Storage Performance

“…The former will promote electrode/electrolyte contact and sodium ion accommodation, the latter will benefit ion diffusion. [38] The FESEM images of HC and HC-SC composite are displayed in Figure 3. The morphology of HC exhibits a uniform structure that the undulating carbon blocks with numerous holes on the surface (Figure 3a and 3b).…”

“…It can be seen that HC‐SC presents a higher specific surface area and a larger pore size (<20 nm). The former will promote electrode/electrolyte contact and sodium ion accommodation, the latter will benefit ion diffusion …”

The recent progress of pitch-based carbon anodes in sodium-ion batteries

“…An amphiphilic carbon material (ACM) with vast polyaromatic hydrocarbon rigid segments was prepared from coal tar pitch by nitro-sulfuric acid treatment [101,102]. Liu and co-workers [103] used the ACM as a precursor, with an easy oxidizing acid treatment and 1000°C catalytic graphitization to prepare the heteroatomdoped hard/soft hybrids. Herein, the Fe(NO 3 ) 3 •9H 2 O was used as a catalyst, followed by the HNO 3 oxidation.…”