Tin/graphite composites are prepared as anode materials for Li-ion batteries using a dry ball-milling process. The main experimental variables in this work are the ball milling time (0–8 h) and composition ratio (tin:graphite=5:95, 15:85, and 30:70 w/w) of graphite and tin powder. For comparison, a tin/graphite composite is prepared using wet ball milling. The morphology and structure of the different tin/graphite composites are investigated using X-ray diffraction, Raman spectroscopy, energy-dispersive X-ray spectroscopy, and scanning and transmission electron microscopy. The electrochemical properties of the samples are also examined. The optimal dry ball milling time for the uniform mixing of graphite and tin is 6 h in a graphite-30wt.%Sn sample. The electrode prepared from the composite that is dry-ballmilled for 6 h exhibits the best cycle performance (discharge capacity after 50^th cycle: 308 mAh/g and capacity retention: 46%). The discharge capacity after the 50^th cycle is approximately 112 mAh/g, higher than that when the electrode is composed of only graphite (196 mAh/g after 50^th cycle). This result indicates that it is possible to manufacture a tin/graphite composite anode material that can effectively buffer the volume change that occurs during cycling, even using a simple dry ball-milling process.

Phosphorus is an element that plays many important roles in powder metallurgy as an alloy element. The purpose of this study is to investigate the influence of phosphorus addition on the microstructures and mechanical properties of sintered low-alloy steel. The sintered low-alloy steels Fe-0.6%C-3.89%Ni-1.95%Cu-1.40%Mo-xP (x=0, 0.05, 0.10, 0.15, 0.20%) were manufactured by compacting at 700 MPa, sintering in H₂-N₂ at 1260 °C, rapid cooling, and low-temperature tempering in Ar at 160 °C. The microstructure, pore, density, hardness, and transverse rupture strength (TRS) of the sintered low-alloy steels were evaluated. The hardness increased as the phosphorus content increased, whereas the density and TRS showed maximum values when the content of P was 0.05%. Based on microstructure observation, the phase of the microstructure changed from bainite to martensite as the content of phosphorus is increased. Hence, the most appropriate addition of phosphorus in this study was 0.05%.

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  Taehyeob Im, Kopila Gurung, Sebastian Meyers, Antonio Cutolo, Huengseok Oh, Jai-Sung Lee, Brecht Van Hooreweder, Caroline Sunyong Lee
  Journal of Materials Processing Technology.2022; 308: 117705.     CrossRef

Layered LiNi_0.83Co_0.11Mn_0.06O₂ cathode materials single- and dual-doped by the rare-earth elements Ce and Nd are successfully fabricated by using a coprecipitation-assisted solid-phase method. For comparison purposes, nondoping pristine LiNi_0.83Co_0.11Mn_0.06O₂ cathode material is also prepared using the same method. The crystal structure, morphology, and electrochemical performances are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) mapping, and electrochemical techniques. The XRD data demonstrates that all prepared samples maintain a typical α-NaFeO₂-layered structure with the R-3m space group, and that the doped samples with Ce and/or Nd have lower cation mixing than that of pristine samples without doping. The results of SEM and EDS show that doped elements are uniformly distributed in all samples. The electrochemical performances of all doped samples are better than those of pristine samples without doping. In addition, the Ce/Nd dualdoped cathode material shows the best cycling performance and the least capacity loss. At a 10 C-rate, the electrodes of Ce/Nd dual-doped cathode material exhibit good capacity retention of 72.7, 58.5, and 45.2% after 100, 200, and 300 cycles, respectively, compared to those of pristine samples without doping (24.4, 11.1, and 8.0%).

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  Heewon Choi, Nam-gyu Lim, Seong Jun Lee, Jungsoo Park
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  Journal of Alloys and Compounds.2021; 887: 161237.     CrossRef

One-dimensional rutile TiO₂ is an important inorganic compound with applicability in sensors, solar cells, and Li-based batteries. However, conventional synthesis methods for TiO₂ nanowires are complicated and entail risks of environmental contamination. In this work, we report the growth of TiO₂ nanowires on a Ti alloy powder (Ti-6wt%Al-4wt%V, Ti64) using simple thermal oxidation under a limited supply of O₂. The optimum condition for TiO₂ nanowire synthesis is studied for variables including temperature, time, and pressure. TiO₂ nanowires of ~5 μm in length and 100 nm in thickness are richly synthesized under the optimum condition with single-crystalline rutile phases. The formation of TiO₂ nanowires is greatly influenced by synthesis temperature and pressure. The synthesized TiO₂ nanowires are characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM).

Fe₃O₄/Fe/graphene nanocomposite powder is synthesized by electrical wire explosion of Fe wire and dispersed graphene in deionized water at room temperature. The structural and electrochemical characteristics of the powder are characterized by the field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, field-emission transmission electron microscopy, cyclic voltammetry, and galvanometric discharge-charge method. For comparison, Fe₃O₄/Fe nanocomposites are fabricated under the same conditions. The Fe₃O₄/Fe nanocomposite particles, around 15-30 nm in size, are highly encapsulated in a graphene matrix. The Fe₃O₄/Fe/graphene nanocomposite powder exhibits a high initial charge specific capacity of 878 mA/g and a high capacity retention of 91% (798 mA/g) after 50 cycles. The good electrochemical performance of the Fe₃O₄/Fe/graphene nanocomposite powder is clearly established by comparison of the results with those obtained for Fe₃O₄/Fe nanocomposite powder and is attributed to alleviation of volume change, good distribution of electrode active materials, and improved electrical conductivity upon the addition of graphene.

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  Kyunbae Lee, Joonsik Lee, Byung Mun Jung, Byeongjin Park, Taehoon Kim, Sang Bok Lee
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Tin is one of the most promising anode materials for next-generation lithium-ion batteries with a high energy density. However, the commercialization of tin-based anodes is still hindered due to the large volume change (over 260%) upon lithiation/delithiation cycling. To solve the problem, many efforts have been focused on enhancing structural stability of tin particles in electrodes. In this work, we synthesize tin nano-powders with an amorphous carbon layer on the surface and surroundings of the powder by electrical wire explosion in alcohol-based liquid media at room temperature. The morphology and microstructures of the powders are characterized by scanning electron microscopy, Xray diffraction, Raman spectroscopy, and transmission electron microscopy. The electrochemical properties of the powder for use as an anode material for lithium-ion battery are evaluated by cyclic voltammetry and a galvanometric dischargecharge method. It is shown that the carbon-coated tin nano-powders prepared in hexanol media exhibit a high initial charge specific capacity of 902 mAh/g and a high capacity retention of 89% after 50 cycles.

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• Optimization of carbon coating thickness to prevent crack generation in Sn nanoparticles during charge/discharge process and their electrochemical properties
  Ji-Seub Choi, Yeon-Ju Lee, Hoi-Jin Lee, Gyu-Bong Cho, Jai-Won Byeon, Hyo-Jun Ahn, Ki-Won Kim, Jou-Hyeon Ahn, Kwon-Koo Cho
  Journal of Alloys and Compounds.2020; 843: 155892.     CrossRef
• Fabrication of multilayer graphene-encapsulated Sn/SnO2 nanocomposite as an anode material for lithium-ion batteries and its electrochemical properties
  Ju-Seok Song, Gyu-Bong Cho, Ki-Won Kim, Hyo-Jun Ahn, Hye-Sung Kim, Jou-Hyeon Ahn, Kwon-Koo Cho
  Applied Surface Science.2019; 481: 736.     CrossRef

Anodic aluminum oxide (AAO) has been widely used for the development and fabrication of nano-powder with various morphologies such as particle, wire, rod, and tube. So far, many researchers have reported about shape control and fabrication of AAO films. However, they have reported on the shape control with different diameter and length of anodic aluminum oxide mainly. We present a combined mild-hard (or hard-mild) anodization to prepare shape-controlled AAO films. Two main parameters which are combination mild-hard (or hard-mild) anodization and run-time of voltage control are applied in this work. The voltages of mild and hard anodization are respectively 40 and 80 V. Anodization was conducted on the aluminum sheet in 0.3 mole oxalic acid at 4°C. AAO films with morphologies of varying interpore distance, branch-shaped pore, diameter-modulated pore and long funnel-shaped pore were fabricated. Those shapes will be able to apply to fabricate novel nano-materials with potential application which is especially a support to prevent volume expansion of inserted active materials, such as metal silicon or tin powder, in lithium ion battery. The silicon powder electrode using an AAO as a support shows outstanding cycle performance as 1003 mAh/g up to 200 cycles.

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• Nano silicon encapsulated in modified copper as an anode for high performance lithium ion battery
  Jong-Keun Ha, Anupriya K. Haridas, Gyu-Bong Cho, Hyo-Jun Ahn, Jou-Hyeon Ahn, Kwon-Koo Cho
  Applied Surface Science.2019; 481: 307.     CrossRef

The electrochemical properties of cells assembled with the LiNiO₂ (LNO) recycled from cathode materials of waste lithium secondary batteries (Li[Ni,Co,Mn]O₂), were evaluated in this study. The leaching, neutralization and solvent extraction process were applied to produce high-purity NiSO₄ solution from waste lithium secondary batteries. High-purity NiO powder was then fabricated by the heat-treatment and mixing of the NiSO₄ solution and H₂C₂O₄. Finally, LiNiO₂ as a cathode material for lithium ion secondary batteries was synthesized by heat treatment and mixing of the NiO and Li₂CO₃ powders. We assembled the cells using the LiNiO₂ powders and evaluated the electrochemical properties. Subsequently, we evaluated the recycling possibility of the cathode materials for waste lithium secondary battery using the processes applied in this work.