• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.309-314
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• 2010

The surface modified $LiMn_2O_4$ materials with Li-Fe composites were prepared by a sol-gel method to improve the electrochemical performance of $LiMn_2O_4$ and were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and transmission electron microscopy (TEM)-EDS. XRD results indicate that all the samples (modified and pristine samples) have cubic spinel structures, and XRD, XPS, and TEM-EDS data reveal the formation of $Li(Li_xFe_xMn_{2-2x})O_4$ solid solution on the surface of particles. For the electrochemical properties, the modified material demonstrated dramatically enhanced reversibility and stability even at elevated temperature. These improvements are attributed to the formation of the solid solution, and thus-formed solid solution phase on the surface of $LiMn_2O_4$ particle reduces the dissolution of Mn ion and suppresses the Jahn-Teller effect.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.5
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• pp.335-340
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• 2018

Transition metal oxide materials have attracted widespread attention as Li-ion battery electrode materials owing to their high theoretical capacity and good Li storage capability, in addition to various nanostructured materials. Here, we fabricated a CoO Li-ion battery in which Co nanoparticles (NPs) are deposited into a current collector through electrophoretic deposition (EPD) without binding and conductive agents, enabling us to focus on the intrinsic electrochemical properties of CoO during the conversion reaction. Through optimized Co NP synthesis and electrophoretic deposition (EPD), CoO Li-ion battery with 630 mAh/g was fabricated with high cycle stability, which can potentially be used as a test platform for a fundamental understanding of conversion reaction.

• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2698-2700
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• 2010

• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.31-35
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• 2007

In this review article, we are going to explain the recent development of lithium secondary batteries for a cellular phone. There are three kinds of rechargeable batteries for cellular phones such as nickel-cadmium, nickel-metal hydride, and lithium ion or lithium ion polymer. The lithium secondary battery is one of the most excellent battery in the point of view of energy density. It means very small and light one among same capacity batteries is the lithium secondary battery. The market volume of lithium secondary batteries increases steeply about 15% annually. The trend of R&D is focused on novel cathode materials including $LiFePO_4$, novel anode materials such as lithium titanate, silicon, and tin, elecrolytes, and safety insurance.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.180-186
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• 2018

We report the discovery of Li-rich $Li_{1+x}[(Ni_{0.225}Co_{0.15}Mn_{0.625})_{1-y}V_y]O_2$ as a cathode material for rechargeable lithium-ion batteries in which a small amount of tetravalent vanadium ($V^{4+}$) is selectively and completely incorporated into the manganese sites in the lattice structure. The unwanted oxidation of vanadium to form a $V_2O_5-like$ secondary phase during high-temperature crystallization is prevented by uniformly dispersing the vanadium ions in coprecipitated $[(Ni_{0.225}Co_{0.15}Mn_{0.625})_{1-y}V_y](OH)_2$ particles. Upon doping with $V^{4+}$ ions, the initial discharge capacity (>$275mA\;h\;g^{-1}$), capacity retention, and voltage decay characteristics of the Li-rich layered oxides are improved significantly in comparison with those of the conventional undoped counterpart.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.620-627
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• 1999

Electrochemical properties of the Al current collector being used in lithium ion batteries have been studied in the 4 different aprotic electrolytes(1 M $LiBF_4$ EC : DMC, 1 M $LiBF_4$ EC : EMC. 1 M $LiPF_6$ EC : DMC. 1 M $LiPF_6$ EC : EMC) employing cyclic voltammetry and impedance measurement. Al electrode showed a wide range of the electrochemical window(0.5~4.1 V vs. $Li/Li^{+}$). However, solid interfacial materials has been formed on the Al surface due to reduction of impurities($H_2O$, $O_2$, etc), lithium salts, and electrolytes at low applied potentials, and aluminum oxides in the highly oxidizing potential as well. Especially, Al current collector was susceptible to localized in consequence of impurities in electrolytes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.4
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• pp.351-359
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• 2014

This paper introduces the lithium ion battery system for LEO(Low Earth Orbit) small satellites. This study proves the reliability of lithium ion batteries applying to the space application. The specifications for lithium ion battery unit are proposed to supply power to the satellite and the overall mechanical design including structural simulation to confirm the reliability of the lithium ion BMS(Battery Management System) under the space environment and launching conditions. The results of structural simulation, functional tests, and space environmental tests show the lithium ion battery system is space qualified. Space qualification of the small satellite battery system to secure reliability of BMS and lithium ion batteries lend credibility for using lithium ion batteries in space application.

• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.197-210
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• 2008

The cathode materials for lithium ion battery have been developed in accordance with the battery performance. $LiCoO_2$ initially adapted at lithium ion battery is going to be useful even at the charging voltage of 4.3 V by surface treatment or doping which drastically improved the performance of $LiCoO_2$. On the other hand, the complicate and multiple functions of recent electronic equipments required higher operational voltage and higher capacity than ever, which is going to be driving force for developing new cathode materials. Some of them are $LiNi_{1-x}{M_xO_2}$, $Li[Ni_{x}Mn_{y}Co_{z}]O_{2}$, $Li[{Ni}_{1/2}{Mn}_{1/2}]O_{2}$. Other new type of cathode materials having high safety is also developed to apply for HEV (hybrid electrical vehicle) and power tool applications. ${LiMn}_{2}{O}_{4}$ and $LiFePO_4$ are famous for highly stable material, which are expected to give contribution to make safer battery. In near future, the various materials having both capacity and safety will be developed by new technology, such as solid solution composite.

• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.61-65
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• 2010

Ultrathin atomic layer deposition (ALD) coatings were found to enhance the performance of lithium-ion batteries (LIBs). Previous studies have demonstrated that $LiCoO_2$ cathode powders coated with metal oxides with thicknesses of $\sim100-1000{\AA}$ grown using wet chemical techniques improved LIB performance. In this study, $LiCoO_2$ powders were coated with conformal $Al_2O_3$ ALD films with thicknesses of only $\sim3-4{\AA}$ established using 2 ALD cycles. The coated $LiCoO_2$ powders exhibited a capacity retention of 89% after 120 charge-discharge cycles in the 3.3~4.5 V (vs. $Li/Li^+$) range. In contrast, the bare $LiCoO_2$ powders displayed only a 45% capacity retention. This dramatic improvement may result from the ultrathin $Al_2O_3$ ALD film acting to minimize Co dissolution or to reduce surface electrolyte reactions.

• Carbon letters
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• v.2 no.1
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• pp.72-75
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• 2001

The performance of Li-ion system based on $LiCoO_2$ and Graphite is well optimized for the 3C applications. The charge-discharge mode, the manufacturing process, the cell performance and the thermal reactions affecting safety has been explained in the engineering point of view. The energy density of the current LIB system is in the range of 300~400 Wh/l. In order to achieve the energy density higher than 500 Wh/l, the active materials should be modified or changed. Adopting new high capacity anode materials would be effective to improve energy density.