Porous Carbon Hollow Rod for Supercapacitors with High Energy Density

Hierarchically Porous Carbon Nanosheets from One-Step Carbonization of Zinc Gluconate for High-Performance Supercapacitors

Supercapacitors, with high energy density, rapid charge-discharge capabilities, and long cycling ability, have gained favor among many researchers. However, the universality of high-performance carbon-based electrodes is often constrained by their complex fabrication methods. In this study, the common industrial materials, zinc gluconate and ammonium chloride, are uniformly mixed and subjected to a one-step carbonization strategy to prepare three-dimensional hierarchical porous carbon materials with high specific surface area and suitable nitrogen doping. The results show that a specific capacitance of 221 F g-1 is achieved at a current density of 1 A g-1. The assembled symmetrical supercapacitor achieves a high energy density of 17 Wh kg-1, and after 50,000 cycles at a current density of 50 A g-1, it retains 82% of its initial capacitance. Moreover, the operating voltage window of the symmetrical device can be easily expanded to 2.5 V when using Et4NBF4 as the electrolyte, resulting in a maximum energy density of up to 153 Wh kg-1, and retaining 85.03% of the initial specific capacitance after 10,000 cycles. This method, using common industrial materials as raw materials, provides ideas for the simple preparation of high-performance carbon materials and also provides a promising method for the large-scale production of highly porous carbons.

Facile synthesis of crumpled nitrogen-doped porous carbon nanosheets with ultrahigh surface area for high-performance supercapacitors

Porous carbon nanosheets are currently considered excellent electrode materials for high-performance supercapacitors. However, their ease of agglomeration and stacking nature reduce the available surface area and limit the electrolyte ion diffusion and transport, thereby leading to low capacitance and poor rate capability. To solve these problems, we report an adenosine blowing and KOH activation combination strategy to prepare crumpled nitrogen-doped porous carbon nanosheets (CNPCNS), which exhibit much higher specific capacitance and rate capability compared to flat microporous carbon nanosheets. The method is simple and capable of one-step scalable production of CNPCNS with ultrathin crumpled nanosheets, ultrahigh specific surface area (SSA), microporous and mesoporous structure and high heteroatom content. The optimized CNPCNS-800 with a thickness of 1.59 nm has an ultrahigh SSA of 2756 m² g^-1, high mesoporosity of 62.9% and high heteroatom content (2.6 at% for N, 5.4 at% for O). Consequently, CNPCNS-800 presents an excellent capacitance, high rate capability and long cycling stability both in 6 M KOH and EMIMBF₄. More importantly, the energy density of the CNPCNS-800-based supercapacitor in EMIMBF₄ can reach up to 94.9 W h kg^-1 at 875 W kg^-1 and is still 61.2 W h kg^-1 at 35 kW kg^-1.

Waste-converted nitrogen and fluorine co-doped porous carbon nanosheets for high performance supercapacitor with ionic liquid electrolyte

In this work, nitrogen and fluorine co-doped porous carbon nanosheets (NFPCNS) were fabricated from pharmaceutical drug residues derived from the fermentation synthesis of lincomycin hydrochloride via high-temperature pyrolysis and subsequent KOH activation without adding any nitrogen and fluorine reagents. The obtained NFPCNS exhibits an optimized integration of three dimensional interconnected nanosheet structure, large specific surface area of 2912 m² g^-1, hierarchical porous structure with large mesopore proportion (S_meso/S_micro = 151.5%, V_meso/V_micro = 248.2%) and high level heteroatom content (13.2 at.% O, 4.3 at.% N and 1.0 at.% F). Therefore, NFPCNS based supercapacitors using 1-ethyl-3-methylimidazolium tetrafluoroborate electrolyte exhibit an excellent gravimetric capacitance of 296F g^-1 at 1 A g^-1, good rate capability of 65% at 20 A g^-1 and high energy density of 125 Wh kg^-1. Furthermore, an ultra-high energy density of 173 Wh kg^-1 and a long cycling life with 93% capacitance retention after 2000 cycles has been achieved by NFPCNS based supercapacitors with 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide electrolyte. NFPCNS should be a green and efficient electrode materials for next-generation high-energy supercapacitors.