• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.5
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• pp.383-390
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• 2001

We have investigated the L $i_{1+x}$M $n_2$ $O_4$system as a cathode material for lithium rechargeable batteries. To improve the cycle performance of spinel LiM $n_2$ $O_4$ as the cathode of 4V class lithium secondary batteries, spinel phase L $i_{1+x}$M $n_2$ $O_4$(x=0, 0.025, 0.05, 0.075) was prepared at 75$0^{\circ}C$ for 48h. The preparation of L $i_{1+x}$M $n_2$ $O_4$ from L $i_2$ $O_3$ and Mn $O_2$ under air is studied. The compounds were synthesized by using solid-state reaction. Structural refinements were carried out with a Rietveld-refinement program. Electrochemical properties were examined using the Li/L $i_{1+x}$M $n_2$ $O_4$ cells. The capacity of L $i_{1+x}$M $n_2$ $O_4$ decreases with increases lithium content, while the cycle life improves. The initial discharge capacity are 118mAh/g and 116mAh/g for LiM $n_2$ $O_4$ decreases with increases lithium content, while the cycle life improves. The initial discharge capacity are 118mAh/g and 116mAh/g for LiM $n_2$ $O_4$ and L $i_{1.025}$M $n_2$ $O_4$, respectively.pectively.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.965-967
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• 1999

In order to solve to instability in air and to format dentrite, we used carbonized phenol resin electrode which is amorphous carbon. The structure and properties of deeply Li-doped carbonized phenol resin have been investigated in association with their utilization as electrodes in rechargeable batteries. Resol type phenol resin used as starting material. The doped lithium was found neither in metallic nor in ionic states even in the most deeply doped state($C_{2.2}$Li stage). It has also been confirmed that the carbonized phenol resin electrode has a large capacity with good stability and reversibility. These results strongly suggest that the carbonized phenol resin can make an excellent anode material for secondary batteries. Finally, we discuss that the carbonized phenol resin doped up to the $C_2Li$ stage can exhibit an energy density per volume as high as lithium metal. We know that carbonized phenol resin can used as cathode as well as anode by cyclic voltammogram.

• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.190-196
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• 2008

The multilayered membrane for lithium rechargeable batteries based on poly (vinylidene fluoride) (PVdF) is prepared with the coated layer containing nano-sized filler. The prepared membranes were subjected to studies of mechanical strength, morphology, interfacial stability, impedance spectroscopy, ionic conductivity, and cycle performance. The localized inorganic filler in the PVdF composite membrane rendered mechanical strength much reduced because of its low stretching ratio and it results in around half value of the mechanical strength of highly stretched PVdF membrane. In order to achieve high ionic conductivity and interfacial stability without sacrificing high mechanical strength, coating layer with nano-filler was newly introduced to PVdF membrane. The ionic conductivity of the coated membrane was 1.03 mS/cm, and the interface between the coating layer and PVdF membrane was stable when the membrane was immersed into liquid electrolyte. The discharge capacity of the cell based on nano-filler coated PVdF membrane was around 91% of the initial discharge capacity after 250 cycles, which is an improvement in cycle performance compared to the case for the non-coated PVdF membrane.

• Journal of Powder Materials
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• v.22 no.1
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• pp.15-20
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• 2015

The composite of porous silicon (Si) and amorphous carbon (C) is prepared by pyrolysis of a nano-porous Si + pitch mixture. The nano-porous Si is prepared by mechanical milling of magnesium powder with silicon monoxide (SiO) followed by removal of MgO with hydrochloric acid (etching process). The Brunauer-Emmett-Teller (BET) surface area of porous Si ($64.52m^2g^{-1}$) is much higher than that before etching Si/MgO ($4.28m^2g^{-1}$) which indicates pores are formed in Si after the etching process. Cycling stability is examined for the nano-porous Si + C composite and the result is compared with the composite of nonporous Si + C. The capacity retention of the former composite is 59.6% after 50 charge/discharge cycles while the latter shows only 28.0%. The pores of Si formed after the etching process is believed to accommodate large volumetric change of Si during charging and discharging process.

• Journal of the Korean Vacuum Society
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• v.9 no.1
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• pp.42-47
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• 2000

The amorphous vanadium oxide thin films for thin-film rechargeable lithium batteries were fabricated by r.f. reactive sputtering at room temperature. As the experimental parameter, oxygen partial pressure was varied during sputtering. At high oxygen partial pressures(>30%), the as-deposited films, constant current charge/discharge characteristics were carried out in 1M $LiPF_6$, EC:DMC+1:1 liquid electrolyte using lithium metal as anode. The specific capacity of amorphous $V_2O_5$ after 200cycles of operation at room temperature was higher compared to crystalline $V_2O_5$. The amorphous vanadium oxide thin film and crystalline film showed about 60$\mu$Ah/$\textrm{cm}^2\mu\textrm{m}$ and about 38$\mu$Ah/$\textrm{cm}^2\mu\textrm{m}$, respectively. These results suggest that the battery capacity of the thin film vanadium oxide cathode strongly depends on the crystallinity.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.37.2-37.2
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• 2010

Recently $Li_{1.2}Ni_{0.2}Mn_{0.6}O_2$ has been consistently examined and investigated by scientists because of its high lithium storage capacity, which exceeds beyond the conventional theoretical capacity based on conventional chemical concepts. Consequently, $Li_{1.2}Ni_{0.2}Mn_{0.6}O_2$ is considered as one of the most promising cathode candidates for next generation in Li rechargeable batteries. Yet the mechanism and the origin of the overcapacity have not been clarified. Previously, many authors have demonstrated simultaneous oxygen evolution during the first delithiation. However, it may only explain the high capacity of the first charge process, and not of the subsequent cycles. In this work, we report a clarified interpretation of the structural evolution of $Li_{1.2}Ni_{0.2}Mn_{0.6}O_2$, which is the key element in understanding its anomalously high capacity. We identify how the structural evolution of $Li_{1.2}Ni_{0.2}Mn_{0.6}O_2$ occurs upon the electrochemical cycling through careful study of electrochemical profiles, ex-situ X-ray diffraction (XRD), HR-TEM, Raman spectroscopy, and first principles calculation. Moreover, we successfully separated the structural change at subsequent cycles (mainly cation rearrangement) from the first charge process (mainly oxygen evolution with Li extraction) by intentionally synthesizing sample with large particle size. Consequently, the intermediate states of structural evolution could be well resolved. All observations made through various tools lead to the result that spinel-like cation arrangement and lithium environment are created and embedded in layered framework during repeated electrochemical cycling.

• Journal of Electrochemical Science and Technology
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• v.12 no.4
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• pp.424-430
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• 2021

The element iron (Fe) is affordable and abundantly available, and thus, it finds use in a wide range of applications. As regards its application in rechargeable lithium-ion batteries (LIBs), the electrochemical reactions of Fe must be clearly understood during battery charging and discharging with the LIB electrolyte. In this study, we conducted systematic electrochemical analyses under various voltage conditions to determine the voltage at which Fe corrosion begins in general lithium salts and organic solvents used in LIBs. During cyclic voltammetry (CV) experiments, we observed a large corrosion current above 4.0 V (vs. Li/Li⁺). When a constant voltage of 3.7 V (vs. Li/Li⁺), was applied, the current did not increase significantly at the beginning, similar to the CV scenario; on the other hand, at a voltage of 3.8 V (vs. Li/Li⁺), the current increased rapidly. The impact of this difference was visually confirmed via scanning electron microscopy and optical microscopy. Our X-ray photoelectron spectroscopy measurements showed that at 3.7 V, a thick organic solid electrolyte interphase (SEI) was formed atop a thin fluoride SEI, which means that at ≥3.8 V, the SEI cannot prevent Fe corrosion. This result confirms that Fe corrosion begins at 3.7 V, beyond which Fe is easily corrodible.

• Resources Recycling
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• v.31 no.3
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• pp.3-15
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• 2022

Lithium is the lightest metal and the first metal in the periodic table. Lithium is used in a variety of applications, including the production of organolithium compounds, as an alloying addition to aluminum and magnesium, and as the anode in rechargeable lithium ion batteries especially for electronic devices and electric vehicles. Therefore, lithium is indispensable metal in our daily lives. The use of lithium continues to rise and has increased from about 14,000 tonnes per year worldwide in the 2000 to about 82,200 tonnes in the 2000. However, lithium is a representative rare metal and ranks 32nd among the abundant elements in the earth's crust. This study reviews the current status of the lithium extraction processes as well as the trend in production amount and use. Lithium is extracted by a various methods depending on the type of resources. These extraction methods are essential for the development of new recycling processes that can extract lithium from secondary lithium resources.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.846-850
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• 2011

Nanocomposite anodes for rechargeable lithium battery are prepared by mixing tin and nickel nanoparticles via wet method and their electrochemical properties are examined. The Sn-Ni nanocomposite anode shows a maximum discharge capacity of 700 mAh $g^{-1}$ at the first cycle but very poor cycle performance. This means that the electrode porosity and the Ni component formed by the simple mixing of nanoparticles no longer play the role of buffering the volume expansion/contraction of Sn component during charge-discharge. To solve the cycle performance problem, a novel nanostructured Sn-Ni anode should be designed and tested.

• Journal of the Mineralogical Society of Korea
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• v.22 no.1
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• pp.63-72
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• 2009

Carbon-coated lithium iron phosphate ($LiFePO_4/C$) composites are synthesized by the modified mechanical activation method (modified MA process) and studied by the Rietveld structural refinement. Rietveld indices of $LiFePO_4/C$ indicate good fitting with $R_p=8.14%,\;R_{wp}=11.1%,\;R_{exp}=9.09%,\;R_B=3.88%$, and S (GofF, Goodness of fit) = 1.2, respectively. $LiFePO_4/C$ with a space group Pnma shows a = 10.3229(3)${\AA}$, b = 6.0052(2) ${\AA}$, c = 4.6939(1) ${\AA}$, and V = 290.98(1) ${\AA}^3$ in dimension, indicating good agreements with those of previous works. Synthetic powders are nano-sized ($65{\sim}90nm$) homogeneous particles with high purity. Thus the modified MA method will be an efficient process to get a high quality cathode material for commercial lithium batteries.