Search Results (6)

Hanji-derived porous carbon has been developed and utilized as a cathode material for Li-S batteries, demonstrating exceptional electrochemical performance and stability. The unique porous structure and high surface area of Hanji-based carbon enhanced S utilization and significantly improved the overall efficiency of the battery. The material exhibited excellent electrical conductivity and structural stability, effectively addressing the major challenges of Li-S batteries, such as the polysulfide shuttle effect and active material loss. In addition, flake carbon-coated separators (FCCSs) were integrated into Li-S cells to further enhance their performance, achieving a high initial specific capacity of approximately 1200 mAh/g and maintaining a capacity of 620 mAh/g after 100 cycles. In contrast, cells with conventional polypropylene separators exhibited lower initial capacities (946 mAh/g), which decreased to 366 mAh/g after 100 cycles. FCCSs also demonstrated superior capacity retention and stability under varying charge–discharge rates, maintaining a capacity of 200 mAh/g at 3 C and recovering to 730 mAh/g when the rate was 0.1 C. This study provides valuable insights into the development of sustainable and efficient Li-S battery systems, with Hanji-based carbon and FCCSs emerging as promising components for commercial applications. Full article

A carbonized interlayer effectively helps to improve the electrochemical performance of lithium–sulfur (Li–S) batteries. In this study, a simple and inexpensive carbon intermediate layer was fabricated using a traditional Korean paper called “hanji”. This carbon interlayer has a fibrous porous structure, with a specific surface area of 91.82 m² g⁻¹ and a BJH adsorption average pore diameter of 26.63 nm. The prepared carbon interlayer was utilized as an intermediary layer in Li–S batteries to decrease the charge-transfer resistance and capture dissolved lithium polysulfides. The porous fiber-shaped carbon interlayer suppressed the migration of polysulfides produced during the electrochemical process. The carbon interlayer facilitates the adsorption of soluble lithium polysulfides, allowing for their re-utilization in subsequent cycles. Additionally, the carbon interlayer significantly reduces the polarization of the cell. This simple strategy results in a significant improvement in cycle performance. Consequently, the discharge capacity at 0.5 C after 150 cycles was confirmed to have improved by more than twofold, reaching 230 mAh g⁻¹ for cells without the interlayer and 583 mAh g⁻¹ for cells with the interlayer. This study demonstrates a simple method for improving the capacity of Li–S batteries by integrating a functional carbon interlayer. Full article

Microtube-like porous carbon (MPC) and tube-like porous carbon–sulfur (MPC-S) composites were synthesized by carbonizing milkweed pappus with sulfur, and they were used as cathodes for lithium–sulfur batteries. The morphology and uniformity of these materials were characterized using X-ray powder diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy with an energy-dispersive X-ray analyzer, thermogravimetric analysis, and X-ray photoelectron spectrometry. The electrochemical performance of the MPC-S cathodes was measured using the charge/discharge cycling performance, C rate, and AC impedance. The composite cathodes with 93.8 wt.% sulfur exhibited a stable specific capacity of 743 mAh g⁻¹ after 200 cycles at a 0.5 C. Full article

It has been reported that improving electrical conductivity and maintaining stable structure during discharge/charge process are challenge for Si to be used as an anode for lithium ion batteries (LIB). To address this problem, milkweed (MW) was carbonized to prepare hollow carbon microtubes (HCMT) derived from biomass as an anode template for LIB. In order to improve electrical conductivity, various materials such as chitosan (CTS), agarose, and polyvinylidene fluoride (PVDF) are used as carbon source (C1, C2, and C3) by carbonization. Carbon coated HCMT@Si composits, HCMT@Si@C1, HCMT@Si@C1@C2, and HCMT@Si@C1@C3, have been successfully synthesized. Changes in structure and crystallinity of HCMT@Si composites were characterized by using X-ray diffraction (XRD). Specific surface area for samples was calculated by using BET (Brunauer–Emmett–Teller). Also, pore size and particle size were obtained by particle and pore size analysis system. The surface morphology was evaluated using high resolution scanning electron microscopy (HR-SEM), Field Emission transmission electron microscopy (TEM). The thermal properties of HCMT@Si composites were analyzed by thermogravimetric analysis (TGA). Our research was performed to study the synthesis and electrochemical performance of Si composite with HCMT by the carbonization of natural micro hollow milkweed to form an inner space. After carbonization at 900 °C for 2 h in N₂ flow, inner diameter of HCMT obtained was about 10 μm. The electrochemical tests indicate that HCMT@Si@C1@C3 exhibits discharge capacity of 932.18 mAh/g at 0.5 A/g after 100 cycles. Full article

Lithium-sulfur (Li-S) batteries have shown a high theoretical specific capacity of 1675 mAh g⁻¹. However, amongst the issues they have, the low electron conductivity of sulfur and its dissolution represent the biggest challenge limiting its practical applications. This contributes to the low utilization of the active sulfur at the cathode—a phenomenon known as the “shuttling effect.” To overcome these limitations, some strategies such as physical confinement (sulfur–carbon composite), chemical adsorption (N and/or S doping) electrolyte design, and separator design have already been proposed. Calcium citrate is the most attractive carbon source because no activation process is necessary and the fabrication process is very simple. In this experiment, we synthesized calcium citrate and sulfur (S) to conduct a charging–discharging test and compared them by adding thiourea (TU) as well as S in the carbonized calcium citrate (CaC). This effective and simple technique for material production can accommodate the charge/discharge reactions and preserve the structure over long cycles. A CaC/TU-S composite is acceptable for an initial discharge capacity of 1051.6 mAh g⁻¹ over 100 cycles at 1 C. The results show that the CaC-S and CaC/TU-S composites have a good, stable specific capacity. Full article

The geometric structures of Pd-complexes {Pd([9]aneB₂A)L₂ and Pd([9]aneBAB)L₂ where A = P, S; B = N; L = PH₃, P(CH₃)₃, Cl⁻}, their selective orbital interaction towards equatorial or axial (soft A…Pd) coordination of macrocyclic [9]aneB₂A tridentate to PdL₂, and electron density transfer from the electron-rich trans L-ligand to the low-lying unfilled a_1g(5s)-orbital of PdL₂ were investigated using B3P86/lanl2DZ for Pd and 6-311+G** for other atoms. The pentacoordinate endo-[Pd([9]aneB₂A)(L-donor)₂]²⁺ complex with an axial (soft A--Pd) quasi-bond was optimized for stability. The fifth (soft A--Pd) quasi-bond between the σ-donor of soft A and the partially unfilled a_1g(5s)-orbital of PdL₂ was formed. The pentacoordinate endo-Pd([9]aneB₂A)(L-donor)₂]²⁺ complex has been found to be more stable than the corresponding tetracoordinate endo-Pd complexes. Except for the endo-Pd pentacoordinates, the tetracoordinate Pd([9]aneBAB)L₂ complex with one equatorial (soft A-Pd) bond is found to be more stable than the Pd([9]aneB₂A)L₂ isomer without the equatorial (A-Pd) bond. In particular, the geometric configuration of endo-[Pd([9]anePNP)(L-donor)₂]²⁺ could not be optimized. Full article