• Carbon letters
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• v.1 no.3_4
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• pp.170-177
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• 2001

Lithium intercalated carbon (LIC) are basically employed as an anode for currently commercialized lithium secondary batteries. However, there are still strong interests in modifying carbon surface of active materials of the anode because the amount of irreversible capacity, charge-discharge capacity and high rate capability are largely determined by the surface conditions of the carbon. In this study, the carbonaceous materials were coated with tin oxide and copper by fluidized-bed chemical vapor deposition (CVD) method and their coating effects on electrochemical characteristics were investigated. The electrode which coated with tin oxides gave the higher capacity than that of raw material. Their capacity decreased with the progress of cycling possibly due to severe volume changes. However, the cyclability was improved by coating with copper on the surface of the tin oxides coated carbonaceous materials, which plays an important role as an inactive matrix buffering volume changes. An impedance on passivation film was decreased as tin oxides contents and it resulted in the higher capacity.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.786-790
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• 1998

K-GIC of the new carbon electrode to improve performance of carbon negative electrode in lithium ion secondary battery was prepated and its electrical characteristics were studied. Form this study, intercalated K quantity was increased in order of $2>3>1mole/{\ell}$ of KCl solution. And, for KCl solution of 1mole, the mole ratio of carbon and potassium was 156~388 carbon/potassium. The proper condition of K-GIC preparation was KCl solution of $1mole/{\ell}$, reaction temperature of $700^{\circ}C$, reaction time of 1 hour. From this condition, the intercalation and deintercalation behavior of lithium was very excellent. Also the reversibility was excellent.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.6
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• pp.328-334
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• 2000

A lithium ion secondary battery using carbon as a negative electrode has been developed. Further improvements to increase the cell capacity are expected by modifying the structure of the carbonaceous material. There are hopes for the development of large capacity lithium ion secondary batteries with long cycle, high energy density, high power density, and high energy efficiency. In the present paper, needle cokes from petroleum were examined as an anode of lithium ion secondary battery. Petroleum cokes, MCL(Molten Caustic Leaching) treated in Korea Institute Energy Research, were carbonized at various temperatures of 0, 500, 700, $19700^{\circ}C$ at heating rate of $2^{\circ}C$/min for lh. The electrolyte was used lM liPF6 EC/DEC (1:1). The voltage range of charge & discharge was 0.0V(0.05V) ~ 2.0V. The treated petroleum coke at $700^{\circ}C$ had an initial capacity over 560mAh.g which beyond the theoretical maximum capacity, 372mAh/g for LiC6. This phenomena suggests that carbon materials with disordered structure had higher cell capacity than that the graphitic carbon materials.

• Journal of the Semiconductor & Display Technology
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• v.7 no.2
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• pp.13-17
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• 2008

In this paper, in order to get the characteristics of the lithium secondary cell, such as charge and discharge characteristic, temperature characteristic, self-discharge characteristic and the capacity recovery rate etc, we build a thermal model that estimate the impedance of battery by experiment & simulation. In this one-dimensional model, Seven governing equations are made to solve seven variables c, $c_s,\;\Phi_1,\;\Phi_2,\;i_2$, j and T. The thermal model parameters used in this model have been adjusted according to the experimental data measured in the laboratory. The result(Voc, Impedance) of this research can be used in BMS(Battery Management System), so an efficient method of using battery is developed.

• Carbon letters
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• v.5 no.3
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• pp.118-126
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• 2004

MCMB (Mesocarbon microbeads) is a kind of anode material for lithium-ion secondary battery. MCMB charge/discharge cycle stability is one of the important criterion at lithium-ion battery operation. In this study, the cycling stability of a lithium-ion secondary battery has been examined. MCMB was made by the direct solvent extraction method. After the MCMB was carbonized and graphitized, the measurement of charge/discharge capacity and efficiency were carried out. In the result, discharge capacity of MCMB in the initial cycle was above 290.0 mAh/g. After the second cycle, efficiency of charge/discharge MCMB was about 98%. These results were similar to the commercial MCMB product.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.631-636
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• 2018

This paper proposed an optimal operation strategy for a hybrid energy storage system (HESS) with a lithium-ion battery and lead-acid battery for mild hybrid electric vehicles (mild HEVs). The proposed mild HEV system is targeted to mount the electric motor and the battery to a conventional internal combustion engine vehicle. Because the proposed mild HEV includes the motor and energy storage device of small capacity, the system focuses on low system cost and small size. To overcome these limitations, it is necessary to use a lead acid battery which is used for a vehicle. Thus, it is possible to use more energy using HESS with a lithium battery and a lead storage battery. The HESS, which combines the lithium-ion battery and the secondary battery in parallel, can achieve better performance by using the two types of energy storage systems with different characteristics. However, the system requires an operation strategy because accurate and selective control of the batteries for each situation is necessary. In this paper, an optimal operation strategy is proposed considering characteristics of each energy storage system, state-of-charge (SOC), bidirectional converters, the desired output power, and driving conditions in the mild HEV system. The performance of the proposed system is evaluated through several case studies with respect to energy capacity, SOC, battery characteristic, and system efficiency.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.822-824
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• 1998

The lithium polymer battery with polymer electrolyte is expected as a safe and long cycle life battery. This paper reports primarily the recent development results of a solid polymer electrolyte, which is a key point of the secondary battery system. The new type of polymer electrolyte was prepared under a dry Ar atmosphere by dissolving $LiCIO_4$ in a matrix of EC, PC and then dispersing polyacrylonitrile(PAN). Also adding some inorganic filler $Al_2O_3$. The dispersed solution heated at $120^{\circ}C$. The polymer electrolyte were characterized by EIS(Electrochemical Impedance Spectroscopy), TGA(Thermo Gravimetric analysis), DMA(Dynamic Mechanical Analyzer), DSC (Differential Scanning Calorimetry). The lithium ion yield is 0.29 when PAN-$Al_2O_3$ which was applied DC 5mV. The ionic conductivity of PAN, PAN-$Al_2O_3$ polymer electrolytes were showed $1.0{\times}10^{-4}S/cm$, $8.4{\times}10^{-4}S/cm$ at room temperature. When inorganic filler was added in the polymer electrolyte, ionic conductivity and lithium yield more larger than without inorganic filler.

• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.3
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• pp.119-123
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• 2005

Lithium titanium oxide as anode material for energy storage prepared by novel synthesis method. Li$_{4}$Ti$_{5}$O$_{12}$ based spinel-framework structures are of great interest material for lithium-ion batteries. We describe here Li$_{4}$Ti$_{5}$O$_{12}$ a zero-strain insertion material was prepared by novel sol-gel method and by high energy ball milling (HEBM) of precursor to from nanocrystalline phases. According to the X-ray diffraction and scanning electron microscopy analysis, uniformly distributed Li$_{4}$ Ti$_{5}$O$_{12}$ particles with grain sizes of 100nm were synthesized. Lithium cells, consisting of Li$_{4}$ Ti$_{5}$O$_{12}$ anode and lithium cathode showed the 173 mAh/g in the range of 1.0 $\~$ 3.0 V. Furthermore, the crystalline structure of Li$_{4}$ Ti$_{5}$O$_{12}$ didn't transform during the lithium intercalation and deintercalation process.

• Journal of the Korean Ceramic Society
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• v.39 no.4
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• pp.394-400
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• 2002

Tin oxide thin films doped with silicon as anodes for lithium secondary battery were fabricated by R. F. magnetron sputtering technique. The electrochemical results for lithium secondary battery anodes showed that addition of silicon decreases the oxidic state of tin, and, hence, reduced the irreversible capacity during the first discharge/charge cycle. The (110),(101),(211) planes were grown with increasing substrate temperatures. The reversible capacity of thin films fabricated in conditions of $300^{\circ}C$ substrate temperature and 7:3 $Ar:O_2$ ratio was 700 mAh/g.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.4
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• pp.353-363
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• 2012

The relationship between the diffusivity and electrochemical characteristics of lithium secondary battery with the modified Si anode material prepared in HF/$AgNO_3$ solution was investigated. The crystallographic structure and images of the modified porous Si and modified Si/Cu was examined using the X-ray diffraction, BET and SEM. To examine the effect of metal composite and pore size distribution according to chemical etching on the electrochemical characterization, the electrodes for half cells were prepared with the modified Si, modified Si/Cu, and modified Si/Cu annealed with $600^{\circ}C$. Our results showed that the chemical diffusivity of lithium ions was related to structure and resistance of Si/Cu composite anode material. The lithium diffusivity in modified silicon compound calculated from the CV was at the range of $1{\times}10^{-12}$ to $9{\times}10^{-16}cm^2/s$. The effects of modified silicon structure and resistance on the cycling efficiency were significant.