• 한국전기화학회:학술대회논문집
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• 1998.12a
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• pp.7-27
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• 1998

In order to design capacity of lithium ion battery, some calculations were carried out based on the characteristics of materials by the given battery shape and dimension. The principle of design was built by the interpretation of the correlation of material, electrochemical and battery factors. Parameters of materials are fundamental physical properties of constituent such as cathode. separator, anode, current collectors and electrolyte. Electrochemical factor includes potential pattern as a function of specific capacity, specific discharge capacity(or initial irreversible specific capacity or Ah efficiency) as a function of specific charge capacity and material balancing. Parameters of battery are dimension, construction hardware and performance. Battery capacity was simulated for a lithium cobalt dioxide as cathode and a hard carbon as anode to achieve 1100 mAh for the charge limit voltage of 4.2V, the weight ratio(+/-) of 2.4 and ICR18650. A fabricated test cell (ICR18650) which have weight ratio(+/-) of 2.4 discharged to 1093 mAh for the charge limit voltage of 4.2V. The sequential discharge capacity show good correspondence with designed capacity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.350-351
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• 2005

The electrochemical behavior of Si-C material synthesized by heating the mixture of silicon and polyvinylidene fluoride (PVDF). Coin cells of the type 2025 were made using the synthesized material and the electrochemical studies were performed. Si-C/Li cells were made by using the developed Si-C material. Charge/discharge test was performed at 0.1C hour rate. Initial charge and discharge capacities at Si-C material derived from 20 wt.% of PVDF was found to be 1,830 and 526 mAh/g respectively. Initial charge/discharge characteristics of the electrode were analyzed. The level of reversible specific capacity was about 216 mAh/g at Si-C material derived from 20 wt.% of PVDF, IIE, intercalation efficiency at initial charge/discharge, was 68 %. Surface irreversible specific capacity was 31 mAh/g, and average specific resistance was 2.6 ohm*g.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.2
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• pp.53-61
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• 2004

Characteristics of half cells of graphite/lithium and LiCoO$_2$/lithium, and full cells of graphite/LiCoO$_2$/ were analyzed by the use of GISOC(the gradual increasing of the state of charge). GISOC analyses generated IIE(the initial intercalation efficiency), which represents lithium intercalation property of the electrode material, and IIC$_{s}$(the initial irreversible capacity by the surface), which represents irreversible reaction between the electrode surface and electrolyte. Linear-fit range of graphite and LiCo/O$_2$electrodes were respectively 370 and 150 mAh/g based on material weight. IIE of graphite and LiCo/O$_2$electrodes were respectively 93∼94 % and 94∼95 %, and IICs of graphite and LiCo/O$_2$electrodes were 15∼17 mAH/g and 0.3∼1.7 mAh/g, respectively. IIE of graphite/LiCo/O$_2$full cell for GX25 and DJG311 as graphite showed 89∼90 %, which IIE value was lower than IIE of half cell of the cathode and the anode. Parameters of IIE and IIC$_{s}$ can also be used to represent not only half cell but also full cell. The characteristics of the full cell can be simulated through the correlative interpretation of potential profile, IIE, and IIC$_{s}$ of half cells.cells.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.511-516
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• 2004

A Li$[Co_{0.17}Li_{0.28}Mn_{0.55}]O_2$ cathode compound was prepared by a simple combustion method. The X-ray diffraction pattern showed that this compound could be classified as ${\alpha} -NaFeO_2$ structure type with the lattice constants of a = 2.8405(9) ${\AA}$ and c = 14.228(4) ${\AA}$. According to XANES analysis, the oxidation state of Mn and Co ions in the compound were 4+ and 3+, respectively. During the first charge process, the irreversible voltage plateau at around 4.65 V was observed. The similar voltage-plateau was observed in the initial charge profile of other solid solution series between $Li_2MnO_3\;and\;LiMnO_2$ (M=Ni, Cr...). The first discharge capacity was 187 mAh/g and the second discharge capacity increased to 204 mAh/g. As the increase of cycling number, one smooth discharge profile was converted to two distinct sub-plateaus and the discharge capacity was slowly decreased. From the Co and Mn K-edge XANES spectra measured at different cyclic process, it can be concluded that irreversible transformation of phase is occurred during continuous cycling process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.4
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• pp.255-262
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• 2016

Effects of $SiO_x$ or C shells on electrochemical properties of Si nanoparticles were investigated. $SiO_x$ shells with thickness of 10~15 nm were formed on homogeneously crystalline Si nanoparticles. Incase of Si-C nanoparticles, there were 30~40 layers of C with a number of defects. Li-ion batteries were fabricated with the above-mentioned nanoparticles, and their electrochemical properties were measured. Pristine Si shows a high IRC (initial reversible capacity) of 2,517 mAh/g and ICE (initial columbic efficiency) of 87%, but low capacity retention of 22%, respectively. $SiO_x$ shells decreased IRC (1,534 mAh/g) and ICE (54%), while the retention increased up to 65%, which can be explained by irreversible phases such as $LiO_2$ and $Li_2SiO_3$. C shells exhibited no differences in IRC and ICE compared to the pristine Si but an enhanced retention of 54%, which might be from proper defect structures.

• Journal of Power System Engineering
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• v.17 no.1
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• pp.104-109
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• 2013

Tin and Tinoxide nanoparticles were prepared by arc-discharge nanopowder process. The negative electrode were fabricated using Tin and Tinoxide nanopower. The microstructure and electrochemistry properties were investigated and compared between Tin and Tinoxide. The oxidation film has microstructure of core/shell type and the shell which was attached around Tin nanoparticle consisted of amorphous $SnO_2$. The shape of Tinoxide nanoparticles was formed with irregular shape in comparison with Tin particle. Initial discharge capcity of Tinoxide electrode possesed about 1000mAh/g, which is about 320mAh/g higher than Tin electrode. Irreversible capacity of Tin electrode is much higher than Tinoxide. The cycle performance of Tinoxide electrode was indicated that is batter than Tin. The Tin negative electrode lost most of capacity after 4 cycle but Tinoxide electrode still retained the capacity. The Tinoxide does show some promise as Li-ion battery anode due to their large reversible capacity at low potentials.

• Bulletin of the Korean Chemical Society
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• v.27 no.8
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• pp.1175-1180
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• 2006

Si-C composites were prepared by the carbonization of polyaniline (PAn) coated on silicone powder. The physical and electrochemical properties of the Si-C composites were characterized by particle-size analysis, X-ray diffraction, scanning electron microscopy, and battery electrochemical tests. The average particle size of Si was increased by the coating of Pan but somewhat reduced by the carbonization to give silicone-carbon composites. The co-existence of crystalline silicone and amorphous-like carbon was confirmed by XRD analyses. SEM photos showed that the silicone particles were well covered with carbonaceous materials, depending on the PAn content. Si-C$\mid$Li cells were fabricated using the Si-C composites and tested using galvanostatic charge-discharge. Si-C$\mid$Li cells gave better electrochemical properties than Si|Li cells. Si-C$\mid$Li cells using Si-C from HCl-undoped precursor PAn showed better electrochemical properties than precursor PAn doped in HCl. The addition of an electrolyte containing 4-fluoroethylene carbonate (FEC) increased the initial discharge capacity. Also, another electrochemical test, the galvanostatic charge-discharge test with GISOC (gradual increasing of the state of charge) was carried out. Si-C(Si:PAn = 50:50 wt. ratio)|Li cell showed 414 mAh/g of reversible specific capacity, 75.7% of IIE (initial intercalation efficiency), 35.4 mAh/g of IICs (surface irreversible specific capacity).

• Korean Journal of Materials Research
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• v.22 no.1
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• pp.1-7
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• 2012

Thin film electrode consisting purely of porous anodic tin oxide with well-defined nano-channeled structure was fabricated for the first time and its electrochemical properties were investigated for application to an anode in a rechargeable lithium battery. To prepare the thin film electrode, first, a bi-layer of porous anodic tin oxides with well-defined nano-channels and discrete nano-channels with lots of lateral micro-cracks was prepared by pulsed and continuous anodization processes, respectively. Subsequent to the Cu coating on the layer, well-defined nano-channeled tin oxide was mechanically separated from the specimen, leading to an electrode comprised of porous tin oxide and a Cu current collector. The porous tin oxide nearly maintained its initial nano-structured character in spite of there being a series of fabrication steps. The resulting tin oxide film electrode reacted reversibly with lithium as an anode in a rechargeable lithium battery. Moreover, the tin oxide showed far more enhanced cycling stability than that of powders obtained from anodic tin oxides, strongly indicating that this thin film electrode is mechanically more stable against cycling-induced internal stress. In spite of the enhanced cycling stability, however, the reduction in the initial irreversible capacity and additional improvement of cycling stability are still needed to allow for practical use.

• Corrosion Science and Technology
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• v.20 no.1
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• pp.15-21
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• 2021

Through a simple filtration process, followed by carbonization within a reductive environment, coffee waste grounds can be transformed into a non-porous hard carbon for use in multiple contexts. This resulting coffee-waste carbon has been evaluated as an eco-friendly and cost-effective replacement for conventional graphite. When compared with different types of carbon, our study found that the coffee-waste carbon fell into the category of hard carbon, as verified from the galvanostatic charge/discharge profiles. The coffee-waste carbon showed a superior rate capability when compared to that of graphite, while compromising smaller capacity at low C rates. During electrochemical reactions, it was also found that the coffee-waste carbon is well exposed to electrolytes, and its disordered characteristic is advantageous for ionic transport which leads to the low tortuosity of Li ions. Finally, the high irreversible capacity (low initial Coulombic efficiency) of the coffee-waste carbon, which if also often observed in amorphous carbon, can be adequately resolved through a solution-based prelithiation process, thereby proving that the coffee-waste carbon material is quite suitable for commercial use as an anode material for quickly-chargeable electrodes.

• Journal of the Korean Electrochemical Society
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• v.5 no.2
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• pp.52-56
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• 2002

Tin oxide was coated on graphite particle by sol-gel method and an electrode with this material having microcrystalline structure for lithium ion battery was obtained by heat treatment in the range $400-600^{\circ}C$. The content of tin oxide was controlled within the range of $2.25wt\%\~11.1wt\%$. The discharge capacity increased with the content of tin oxide and also initial irreversible capacity increased. The discharge capacity of tin oxide electrode showed more than 350 mAh/g at the initial cycle and 300 mAh/g after the 30th cycle in propylene carbonate(PC) based electrolyte whereas graphite electrode without surface modification showed 140 mAh/g. When the charge and discharge rate was changed from C/5 to C/2, The discharge capacity of tin oxide and graphite electrode showed $92\%\;and\;77\%$ of initial capacity, respectively. It has been considered that such an enhancement of electrode characteristics was caused because lithium $oxide(Li_2O)$ passive film formed from the reaction between tin oxide and lithium ion prevented the exfoliation of graphite electrode and also reduced tin enhanced the electrical conduction between graphite particles to improve the current distribution of electrode.