Tailoring Conductive 3D Porous Hard Carbon for Supercapacitors

Abstract

Hard carbon has attracted great attention for energy storage owing to low cost and extremely high microporosity, however, hindered by its low electrical conductivity. The common strategy to improve the conductivity is through graphitization process which requires temperatures as high as 3000 °C and inevitably destroys the porous structure. Herein, a balance between the specific surface area and electrical conductivity in a 3D porous hard carbon by in situ iron‐catalyzed graphitization process together with the Si–O–Si network is successfully achieved. The Fe can accelerate the localized graphitization at relatively low temperature (1000 °C) to form nanographite domains with enhanced conductivity, while the Si–O–Si network contributes to generating a 3D porous structure. As a result, the optimized hard carbon exhibits a 3D interconnected and hierarchical porous structure with extremely high specific surface area (2075 m2 g−1) and excellent electrical conductivity (12 S cm−1) which is comparable with that of artificial graphite. And thus, high capacitance of 315 F g−1 and excellent rate capability (174 F g−1 at 40 A g−1) are simultaneously achieved when used as electrodes for supercapacitors. The strategy is promising to build hard carbon materials with well‐tuned properties for high‐performance energy storage.

Modulating Intrinsic Defect Structure of Fibrous Hard Carbon for Super‐Fast and High‐Areal Sodium Energy Storage

“…The electrical conductivity in Figure 4h also verifies the superior electron transfer capability of the TC‐900, even compared with other carbon materials reported in the literatures. [ 14,28,64–67 ] In addition to electron transfer and Na + migration, the Na + diffusion kinetic also has a great impact on the high‐rate charge/discharge process, which can be verified by the facts that, though the electric conductivity of TC‐900 is significantly higher than that of Ti‐900 (Figure 4i), the mesopores‐dominated Ti‐900 shows excellent rate capability with a high capacity retention of 65.2% at 50 A g −1 . Meanwhile, the TC‐1000 with a larger average pore size also retains a high capacity retention of 50.0%, higher than other TC samples.…”

From Waste Biomass to Hard Carbon Anodes: Predicting the Relationship between Biomass Processing Parameters and Performance of Hard Carbons in Sodium-Ion Batteries

“…For instance, the hard carbon derived from Ginkgo leaves [84] has a larger specific surface area and a higher ID/IG ratio compared to the hard carbon Apart from the major carbonization process, an extra pre-treatment and post-treatment may also be included to improve the precursor structure, HC electrochemical performance, and economic process [32]. Specifically, these additional treatments include: acid wash for high ash content precursor [71]; activation to alter porosity [71]; heteroatom-doping for improving the surface chemistry of HC [72,73]; pre-sodiation to improve ICE and longterm cycling performance of the HC anode [74]; and catalytic graphitization to reduce the temperature requirement, and thus increase the economic process [75]. In the majority of studies, a direct carbonization of biomass by-product precursors is conducted without pre-/post-treatment.…”