• Transactions of the Korean hydrogen and new energy society
• /
• v.7 no.2
• /
• pp.165-171
• /
• 1996

The effect of rolling on the charge-discharge property was studied for metal hydride negative electrode. $(LM)Ni_{3.6}Al_{0.4}Co_{0.7}Mn_{0.3}$(pleateau pressure : below 1 atm at room temperature, volume expansion : 9%, entalpy : $8.7kcal/molH_2$) alloy was prepared by arc melting, and then it was coated with various copper weight percent. The copper coated alloys were then rolled with the different reduction ratio. From the results, it was found that the maximum discharge capacity increased with increasing reduction ratio, and 15wt% copper coated sample shows the highest discharge capacity, 324mAh/g, after rolling with 30% reduction ratio. In view of cycle life for the negative electrode, the 15wt% copper coated electrode which was rolled with 13% reduction ratio showed the longest cycle life compared with other electrodes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.361-362
• /
• 2007

Phospho-olivine $LiFePO_4$ cathode materials were prepared by hydrothermal reaction. Carbon black was added to enhance the electrical conductivity of $LiFePO_4$. The structural and morphological performance of $LiFePO_4$ and $LiFePO_4$-C powders were characterized by X-ray diffraction (XRD) and FE-SEM. $LiFePO_4/SPE/Li$ and $LiFePO_4$-C/SPE/Li cells were characterized electrochemically by charge/discharge experiments. The results showed that the discharge capacity of $LiFePO_4$-C/SPE/Li cell was 103 mAh/g at the first cycle. The discharge capacity of $LiFePO_4$-C/SPE/Li cell with 5 wt% carbon black was the largest among $LiFePO_4$-C/SPE/Li cells, 126 mAh/g at the first cycle and 123 mAh/g after 30 cycles, respectively. It was demonstrated that cycling performance of $LiFePO_4$-C/SPE/Li cell with 5 wt% carbon black was better than that of $LiFePO_4$/SPE/Li cell.

• Journal of Electrochemical Science and Technology
• /
• v.3 no.4
• /
• pp.172-177
• /
• 2012

Mo-doped $LiFePO_4$ was synthesized via co-precipitation method using sucrose as the carbon source. Structure, surface morphology, and the electrochemical properties of the synthesized olivine compounds were investigated using Rietveld refinement of X-ray diffraction data (XRD), scanning electron microscopy (SEM), and electrochemical charge-ischarge tests. Spherical morphology with the particle size of ${\sim}8{\mu}m$ authenticated the enhanced tap density and volumetric energy density of the synthesized materials. Charge-discharge behavior of $LiFePO_4$ and Mo-doped $LiFePO_4$ cells demonstrated a specific capacity of 130 and 145 mAh $g^{-1}$, respectively. Mo-doped $LiFePO_4$ cells exhibited an excellent discharge capacity at 96 mAh $g^{-1}$ at 7 C-rate.

• Electrical & Electronic Materials
• /
• v.7 no.4
• /
• pp.317-324
• /
• 1994

In this study, new preparation method of LiCoO$_{2}$ was applied to develop cathode active material for Li rechargeable cell, and followed by X-ray diffraction analysis, electrochemical properties and initial charge/discharge characteristics as function of current density. HC8A72- and CC9A24-LiCoO$_{2}$ were prepared by heating treatment of the mixture of LiOH H$_{2}$O/CoCO$_{3}$(1:1 mole ratio) and the mixture of Li$_{2}$CO$_{3}$/CoCO$_{3}$(1:2 mole ratio) at 850 and 900.deg. C, respectively. Two prepared LiCoO$_{2}$s were identified as same structure by X-ray diffraction analysis. a and c lattice constant were 2.816.angs. and 14.046.angs., respectively. The electrochemical potential of CFM-LiCoO$_{2}$(Cyprus Foote Mineral Co.'s product), HC8A72-LiCoO$_{2}$ and CC9A24 LiCoO$_{2}$ electrode were approximately between 3.32V and 3.42V vs. Li/Li reference electrode. Stable cycling behavior was obtained during the cyclic voltammetry of LiCoO$_{2}$ electrode. According as scan rate increases, cathodic capacity decreases, but redox coulombic efficiency was about 100% at potential range between 3.6V and 4.2V vs. Li/Li reference electrode. Cathodic capacity of HC8A72-LiCoO$_{2}$ was 32% higher than that of CFM-LiCoO$_{2}$ and that of CC9A24-LiCoO$_{2}$ was 47% lower than that of CFM-LiCoO$_{2}$ at 130th cycle in the condition of lmV/sec scan rate. Constant cur-rent charge/discharge characteristics of LiCoO$_{2}$/Li cell showed increasing Ah efficiency with initial charge/discharge cycle. Specific discharge capacities of CFM and HC8A72-LiCoO$_{2}$ cathode active materials were about 93mAh/g correspondent to 34% of theretical value, 110mAh/g correspondent to 40% of theretical value, respectively. In the view of reversibility, HC8A72-LiCoO$_{2}$ was also more excellent than CFM- and CC9A24-LiCoO$_{2}$.

• Journal of the Semiconductor & Display Technology
• /
• v.6 no.1 s.18
• /
• pp.53-57
• /
• 2007

In this paper, the intelligent estimation algorithm is developed for residual quantity estimate of lithium secondary cell and we suggest the control algorithm to get battery SOC through thermal modeling of electric cell. Lithium secondary cell gives cycle life, charge characteristic, discharge characteristic, temperature characteristic, self-discharge characteristic and the capacity recovery rate etc. Therefore, we make an accurate estimate of the capacity of battery according to thermal modeling to know the capacity of electric cell that is decreased by various special quality of lithium secondary cell. And we show effectiveness through comparison of value as result that use simulation and fuzzy logic.

• Journal of the Korean Electrochemical Society
• /
• v.2 no.1
• /
• pp.46-49
• /
• 1999

Lithium cobalt oxide cathode for thin-film rechargeable lithium batteries were fablicated by electron-beam evaporation. Annealed lithium cobalt oxide, which was deposited on to stainless steel substrate, showed well-developed (003) planes of the hexagonal structure and potential plateau at $\~3.9 V$. Lithium cobalt oxide thin films had the stoichiometric Li/co ratio at high deposition rates and exhibited high discharge capacity at $15{\AA}/s$. As the annealing temperature increased, discharge capacity increased with maximum value at $700^{\circ}C$, but showed low capacity as a result of reaction with substrate above $700^{\circ}C$. Unuiformity of the lithium and cobalt in the depth profile gave initial capacity loss with charge/discharge performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.11a
• /
• pp.359-362
• /
• 2000

The purpose of this study is to research and develop graphene composite for lithium polymer battery. VO(graphene) composite is one of the promising material as a electrode active material for lithium polymer battery(LPB). We investigated AC impedance response and charge/discharge cycling of VO(graphene)/SPE/Li cells. The first discharge capacity of VO(graphene) cathode with 50wt.% V$_2$O$\sub$5/ was 150mAh/g, while that of VO(graphene) cathode with 85wt.% V$_2$O$\sub$5/ was 248mAh/g. The Ah efficiency was above 98% after the 2nd cycle. The discharge capacity of VO(graphene) anode with 3wt.% V$_2$O$\sub$5/ was 718 and 266mAh/g at cycle 1 and 10 at room temperature, respectively. The VO(graphene) anode with 3wt.% V$_2$O$\sub$5/ in PVDF-PAN-PC-EC-LiC1O$_4$ electrolyte showed good capacity with cycling.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.05c
• /
• pp.88-90
• /
• 2003

The purpose of this study is to research and develop tin oxide-flash composite for lithium Ion polymer battery. Tin oxide is one of the promising material as a electrode active material for lithium Ion polymer battery (LIPB). Tin-based oxides have theoretical volumetric and gravimetric capacities that are four and two times that of carbon, respectively. We investigated cyclic voltammetry and charge/discharge cycling of SnO-flyash/SPE/Li cells. The first discharge capacity of SnO-flyash composite anode was 720 mAh/g. The discharge capacity of SnO-flyash composite anode 412 and 314 mAh/g at cycle 2 and 10 at room temperature, respectively. The SnO-flyash composite anode with PVDF-PMMA-PC-EC-$LiClO_4$ electrolyte showed good capacity with cycling.

• Journal of the Korean Electrochemical Society
• /
• v.19 no.3
• /
• pp.114-121
• /
• 2016

This study investigates a CFD modeling of the charge-discharge behavior due to heat generation during charge-discharge cycles of a Li-ion secondary battery(LIB). Present LIB system adopted a current-density equation, heat and mass transfer governing equations upon the 1-dimensional system to the thickness direction for the rectangular pouch configuration. According to the 3-kinds of the charge-discharge current densities of 1C($17.5A/m^2$), 3C($52.5A/m^2$) and 5C($87.5A/m^2$) subject to a 3 V of cut-off voltage, a constant-temperature system at 298 K and three different heat generating systems were analyzed with comparison. Battery capacity decreases with increment of charge-discharge densities not only at the constant-temperature system but also at the heat-generating system. The time for charge-discharge cycles increases at the heat-generating system compare to the constant-temperature system. These trends are considered that the increase of temperature due to heat generation causes the decrement of equilibrium potential of electrodes and the increment of diffusivity of Li ions. Furthermore, cooling effects were discussed in order to control the influence of heat generation due to charge-discharge behavior of a Li-ion secondary battery.

• Journal of the Korean Electrochemical Society
• /
• v.7 no.3
• /
• pp.131-137
• /
• 2004

Sol-gel method which provides better electrochemical and physiochemical properties compared to the solid-state method was used to synthesize the material of $LiFe_yMn_{2-y}O_4$. Fe was substituted to increase the structural stability so that the effects of the substitution amount and sintering temperature were analyzed. XRD was used for the structural analysis of produced material, which in turn, showed the same cubic spinel structure as $LiMn_2O_4$ despite the substitution of $Fe^{3+}$. During the synthesis of $LiFe_yMn_{2-y}O_4$, as the sintering temperature and the doping amount of Fe(y=0.05, 0.1, 0.2)were increased, grain growth proceeded which in turn, showed a high crystalline and a large grain size, certain morphology with narrow specific surface area and large pore volume distribution was observed. In order to examine the ability for the practical use of the battery, charge-discharge tests were undertaken. When the substitution amount of $Fe^{3+}\;into\;LiMn_2O_4$ increased, the initial discharge capacity showed a tendency to decrease within the region of $3.0\~4.2V$ but when charge-discharge processes were repeated, other capacity maintenance properties turned out to be outstanding. In addition, when the sintering temperature was $800\~850^{\circ}C$, the initial capacity was small but showed very stable cycle performance. According to EVS(electrochemical voltage spectroscopy) test, $LiFe_yMn_{2-y}O_4(y=0,\;0.05,\;0.1,\;0.2)$ showed two plateau region and the typical peaks of manganese spinel structure when the substitution amount of $Fe^{3+}$ increased, the peak value at about 4.15V during the charge-discharge process showed a tendency to decrease. From the previous results, the local distortion due to the biphase within the region near 4.15V during the lithium extraction gave a phase transition to a more suitable single phase. When the transition was derived, the discharge capacity decreased. However the cycle performance showed an outstanding result.