• Korean Chemical Engineering Research
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• v.55 no.4
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• pp.483-489
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• 2017

The loss of the sulfur cathode material through dissolution of the polysulfide into electrolyte causes a significant capacity reduction of the lithium-sulfur cell during the charge-discharge reaction, thereby debilitating the electrochemical performance of the cell. We addressed this problem by using a chemical and physical approach called reduction of polysulfide dissolution through direct coating functional inorganic (graphene oxide) or organic layer (polyethylene oxide) on electrode, since the deposition of external functional layer can chemically interact with polysulfide and physically prevent the leakage of lithium polysulfide out of the electrode. Through this approach, we obtained a composite electrode for a lithium-sulfur battery (sulfur: 60%) coated with uniform and thin external functional layers where the thin external layer was coated on the electrode by solution coating and drying by a subsequent heat treatment at low temperature (${\sim}80^{\circ}C$). The external functional layer, such as inorganic or organic layer, not only alleviates the dissolution of the polysulfide electrolyte during the charging/discharging through physical layer formation, but also makes a chemical interaction between the polysulfide and the functional layer. As-formed lithium-sulfur battery exhibits stable cycling electrochemical performance during charging and discharging at a reversible capacity of 700~1187 mAh/g at 0.1 C (1 C = 1675 mA/g) for 30 cycles or more.

• Journal of Powder Materials
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• v.29 no.6
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• pp.485-491
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• 2022

Lithium lanthanum titanium oxide (LLTO) is a promising ceramic electrolyte because of its high ionic conductivity at room temperature, low electrical conductivity, and outstanding physical properties. Several routes for the synthesis of bulk LLTO are known, in particular, solid-state synthesis and sol-gel method. However, the extremely low ionic conductivity of LLTO at grain boundaries is one of the major problems for practical applications. To diminish the grain boundary effect, the structure of LLTO is tuned to nanoscale morphology with structures of different dimensionalities (0D spheres, and 1D tubes and wires); this strategy has great potential to enhance the ion conduction by intensifying Li diffusion and minimizing the grain boundary resistance. Therefore, in this work, 0D spherical LLTO is synthesized using ultrasonic spray pyrolysis (USP). The USP method primarily yields spherical particles from the droplets generated by ultrasonic waves passed through several heating zones. LLTO is synthesized using USP, and the effects of each precursor and their mechanisms as well as synthesis parameters are analyzed and discussed to optimize the synthesis. The phase structure of the obtained materials is analyzed using X-ray diffraction, and their morphology and particle size are analyzed using field-emission scanning electron microscopy.

• Bulletin of the Korean Chemical Society
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• v.24 no.10
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• pp.1495-1500
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• 2003

Equilibria and applications of a synergistic extraction were studied for the determination of a trace lithium by using thenoyltrifluoroacetone (TTA) and trioctylphosphine oxide (TOPO) as ligands. Several equations were derived for the extraction of lithium into m-xylene as a phase of Li-TTA·mTOPO adduct. Distribution coefficients and extraction constant were determined together with a stability constant of the adduct. The adduct was quantitatively extracted from the basic solution of higher than pH 9 by shaking for 30 minutes. m-Xylene was selected as an optimum solvent by comparing the extraction efficiency among several kinds of organic solvents. The stability constant (${\Beta}_2$) for Li-TTA/2TOPO was 150 times higher than Li-TTA/TOPO. The distribution coefficient of Li-TTA/2TOPO into m-xylene was 9.12 and the logarithmic extraction constant (log $K_{ex}$) was 6.76. Trace lithium of sub-ppm level in seawater samples could be determined under modified conditions and a detection limit equivalent to 3 times standard deviation for background absorption was 0.42 ng/mL.

• Journal of the Korean Electrochemical Society
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• v.21 no.3
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• pp.55-60
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• 2018

The demand for LIBs with higher energy densities has increased continuously because the emergence of wider and more challenging applications including HEV and EV has became imperative. However, in the case of anode material, graphite is insufficient to meet this need. To meet such demand, several type of negative electrode materials like silicon, tin, SiO, and transition metal oxide have been investigated for the advanced lithium secondary batteries. Recently, lithium vanadium oxide, which has a layered structure, is assumed as one of the promising anode material as alternative of graphite. This material shows a high volumetric capacity, which is 1.5 times higher than that of graphite. However, relative low electrical conductivity and particle fracture, which results in the electrolyte decomposition and loss of electric contact between electrode, induce rapid capacity decay. In this report, we investigated the effect of electrolyte additive on the electrochemical characteristics of lithium vanadium oxide.

• Journal of Environmental Science International
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• v.23 no.7
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• pp.1289-1297
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• 2014

In this study, PVC-LMO beads were prepared by immobilizing lithium manganese oxide (LMO) with poly vinyl chloride (PVC) diluted in dioxane solvent. XRD and SEM analysis confirmed that LMO was immobilized well in PVC-LMO beads. The diameter of PVC-LMO beads prepared by dioxane solvent was about 2 mm. The adsorption experiments of lithium ions by PVC-LMO beads were conducted batchwise. The optimum pH was pH 10. The adsorption characteristics of lithium ions by PVC-LMO beads was well described by the pseudo-second-order kinetic model. The maximum adsorption capacity obtained from Langmuir model was 24.25 mg/g. The thermodynamic parameters such as ${\Delta}H^{\circ}$, ${\Delta}S^{\circ}$ and ${\Delta}G^{\circ}$ were evaluated. The calculated ${\Delta}G^{\circ}$ was between -6.16 and -4.14 kJ/mol (below zero), indicating the spontaneous nature of $Li^+$ adsorption on PVC-LMO beads. Also, the results showed that PVC-LMO beads prepared in this study could be used for the removal of lithium ions from seawater containing coexisting ions such as $Na^+$, $K^+$, $Mg^{2+}$ and $Ca^{2+}$.

• Polymer(Korea)
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• v.27 no.4
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• pp.385-391
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• 2003

Lithium p-［Methoxyoligo(ethyleneoxy)］ benzenesulfonates (LiEOnBS) with different repeating unit of ethylene oxide were synthesized and were used for preparing gel-polymer electrolytes. The conductivities and lithium ion transference number were measured as a function of Li-salt concentration and repeating unit of ethylene oxide of the LiEOnBS. The maximum conductivity of the resulting gel-polymer electrolyte was found to be 4.89${\times}$10$\^$－4/ S/cm (LiEO7.3BS, 0.5 M) at 30$^{\circ}C$. The lithium ion transference number (t$\sub$Li$\sub$＋//) measurement were performed by means of the combination do polarization and ac impedance methods in gel-polymer electrolytes. Lithium ion transference number was measured to be in the range of 0.75∼0.92 for the LiEOnBS containing gel-polymer electrolytes. The maximum t$\sub$Li$\sub$＋// was obtained to be 0.92 for the 0.1 M LiEOnBS containing polymer electrolytes. The synthesized LiEOnBS showed single ion transport like characteristics when n was large than 3.

• Clean Technology
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• v.20 no.2
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• pp.154-159
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• 2014

In this study, PVC-LMO beads were prepared by immobilizing lithium manganese oxide (LMO) with poly vinyl chloride (PVC) diluted in dimethyl sulfoxide (DMSO) solvent on behalf of N-methyl-2-pyrrolidone (NMP). XRD analysis confirmed that LMO was immobilized well in PVC-LMO beads. The diameter of PVC-LMO beads synthesized by DMSO was about 4 mm. The adsorption experiments of lithium ions by PVC-LMO beads were conducted batchwise. The maximum adsorption capacity obtained from Langmuir model was 21.31 mg/g. The adsorption characteristics of lithium ions by PVC-LMO beads was well described by the pseudo-second-order kinetic model. It was considered that the internal diffusion was the rate controlling step.

• Journal of the Korean Ceramic Society
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• v.54 no.5
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• pp.438-442
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• 2017

This paper reports the facile synthesis of microlamella-structured porous copper (Cu)-oxide-based electrode and its potential application as an advanced anode material for lithium-ion batteries (LIBs). Nanowire-like Cu oxide, which is created by a simple thermal oxidation process, is radially and uniformly formed on the entire surface of Cu foam that has been fabricated using a combination of water-based slurry freezing and sintering (freeze casting). Compared to the Cu foil with a Cu oxide layer grown under the same processing conditions, the Cu foam anode with 63% porosity exhibits over twice as much capacity as the Cu foil (264.2 vs. 131.1 mAh/g at 0.2 C), confirming its potential for use as an anode electrode for LIBs.

• 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.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1267-1269
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• 2010

The pure crystalline $Li_{1.1}V_{0.9}O_2$ powder has been prepared by a simple solid state reaction of $Li_2CO_3$ and $V_2O_3$ precursors under nitrogen gas containing 10 mol % hydrogen gas flow. The structure of $Li_{1.1}V_{0.9}O_2$ powder was analyzed using Xray diffraction (XRD) and scanning electron microscope (SEM). The stoichiometric $Li_{1.1}V_{0.9}O_2$ powder was used as anode active material for lithium secondary batteries. Its electrochemical properties were investigated by cyclic voltammetry and constant current methods using lithium foil electrode. The observed specific discharge capacity and charge capacity were 360 mAh/g and 260 mAh/g during the first cycle, respectively. In addition, the cyclic efficiency of this cell was 72.2% in the first cycle. The specific capacity of $Li_{1.1}V_{0.9}O_2$ anode rapidly declines as the current rate increases and retains only 30 % of the capacity of 0.1C rate at 1C rate. The crystallinity of the $Li_{1.1}V_{0.9}O_2$ anode decrease as discharge reaction proceeds. However, the relative intensity of main peaks was almost recovered when the cell was charged up to 1.5 V.