Young Soo Yun

The nanostructure design of porous carbon-based electrode materials is key to improving the electrochemical performance of supercapacitors. In this study, hierarchically porous carbon nanosheets (HP-CNSs) were fabricated using waste coffee grounds by in situ carbonization and activation processes using KOH. Despite the simple synthesis process, the HP-CNSs had a high aspect ratio nanostructure (∼20 nm thickness to several micrometers in lateral size), a high specific surface area of 1945.7 m(2)

Nitrogen- and micropore-containing carbon nanotubes (NMCNTs) were prepared by carbonization of nitrogen-enriched, polymer-coated carbon nanotubes (CNTs), and the electrochemical performances of the NMCNTs with different heteroatom contents were investigated. NMCNTs-700 containing 9.1 wt% nitrogen atoms had a capacitance of 190.8 F/g, which was much higher than that of pristine CNTs (48.4 F/g), despite the similar surface area of the two CNTs, and was also higher than that of activated CNTs (151.

Abstract Ultra‐thin hollow carbon nanospheres (UTH‐CNs) are fabricated for use as anodes of asymmetric sodium ion pseudocapacitors. The ∼3 nm thick amorphous carbon walls obtained from regenerated silk proteins as a template exhibit a well‐defined porous structure suitable for reversible sodium‐ion storage. The UTH‐CNs show remarkable electrochemical activity with sodium via a pseudocapacitive reaction, delivering a large reversible capacity as well as superior rate performance for more than 100

Anode-free sodium metal batteries (AF-SMBs) can deliver high energy and enormous power, but their cycle lives are still insufficient for them to be practical as a power source in modern electronic devices and/or grid systems. In this study, a nanohybrid template based on high aspect-ratio silver nanofibers and nitrogen-rich carbon thin layers as a core-shell structure is designed to improve the Coulombic efficiency (CE) and cycling performance of AF-SMBs. The catalytic nanohybrid templates drama

Sodium-ion batteries (SIBs) have received considerable attention as sustainable and stable energy-storage devices, but their electrochemical performance is inferior to that of current lithium-ion batteries. In this study, we designed high-plateau-capacity hard carbons from waste beverage coffee (WBC) grounds as an anodes for SIBs, using a simple pyrolysis process followed by heating. The inherent structure of the basalt-like WBCs was preserved during the thermal treatment process, resulting in h

In this study, low-density, hard-carbon fibers incorporating multitudinous closed pores with few-nanometer-scale widths were prepared from waste silk fabric by a simple high-temperature heating process (2000 °C). The pyroprotein carbon fibers exhibited a significantly high single-plateau capacity of 300 mA h g–1 at ∼0.1 V Na+/Na, a high initial Coulombic efficiency of ∼91.9%, and stable cycling behaviors of more than 200 cycles when used as the anode of a sodium-ion battery. Characterization usi

We report microporous carbon nanosheets containing numerous redox active heteroatoms fabricated from exfoliated waste coffee grounds by simple heating with KOH for pseudocapacitive charge storage. We found that various heteroatom combinations in carbonaceous materials can be a redox host for lithium ion storage. The bio-inspired nanomaterials had unique characteristics, showing superior electrochemical performances as cathode for asymmetric pseudocapacitors.

A comprehensive study is conducted on hard carbon (HC) series samples by tuning the graphitic local microstructures systematically as an anode for SIBs in both carbonate- (CBE) and glyme-based electrolytes (GBE). The results reveal more detailed charge storage characters of HCs on the LVP section. 1) The LVP capacity is closely related to the prismatic surface area to the basal plane as well as the bulk density, regardless of electrolyte systems. 2) The glyme-sodium ion complex can facilitate so

The use of reduced graphene oxide (rGO) suffers from irreparable damage because of topological defects and residual heteroatoms, which degrade the inherent properties of graphene. To restore its electrical transport properties, charge-transfer chemical doping with d-electron-rich heteroatoms has been proposed. Herein, we report the effects of atomic-level selenium doping in rGO. Using first-principles calculations, we found that selenium atoms could be selectively bonded in particular locations,

Nanohybrid anode materials for Na-ion batteries (NIBs) based on conversion and/or alloying reactions can provide significantly improved energy and power characteristics, while suffering from low Coulombic efficiency and unfavorable voltage properties. An NIB paper-type nanohybrid anode (PNA) based on tin sulfide nanoparticles and acid-treated multiwalled carbon nanotubes is reported. In 1 m NaPF₆ dissolved in diethylene glycol dimethyl ether as an electrolyte, the above PNA shows a hi