• Korean Journal of Materials Research
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• v.30 no.12
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• pp.709-714
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• 2020

For zinc-air batteries, there are several limitations associated with zinc anodes. The self-discharge behavior of zinc-air batteries is a critical issue that is induced by corrosion reaction and hydrogen evolution reaction (HER) of zinc anodes. Aluminum and indium are effective additives for controlling the hydrogen evolution reaction as well as the corrosion reaction. To enhance the electrochemical performances of zinc-air batteries, mechanically alloyed Zn-Al and Zn-In materials with different compositions are successfully fabricated at 500rpm and 5h milling time. Investigated materials are characterized by X-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM), and energy dispersive spectrometer (EDS). Alloys are investigated for the application as novel anodes in zinc-air batteries. Especially, the material with 3 wt% of indium (ZI3) delivers 445.37 mAh/g and 408.52 mAh/g of specific discharge capacity with 1 h and 6 h storage, respectively. Also, it shows 91.72 % capacity retention and has the lowest value of corrosion current density among attempted materials.

• Corrosion Science and Technology
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• v.21 no.6
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• pp.445-453
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• 2022

SiO_x was prepared from a mixture of Si and SiO₂ via high-energy ball milling as a negative electrode material for Li-ion batteries. The molar ratio of Si to SiO₂ as precursors and the milling time were varied to identify the synthetic condition that could exhibit desirable anode performances. With an appropriate milling time, the material showed a unique microstructure in which amorphous Si nanoparticles were intimately embedded within the SiO₂ matrix. The interface between the Si and SiO₂ was composed of silicon suboxides with Si oxidation states from 0 to +4 as proven by X-ray photoelectron spectroscopy and electrochemical analysis. With the addition of a conductive carbon (Super P carbon black) as a coating material, the SiO_x/C manifested superior specific capacity to a commercial SiO_x/C composite without compromising its cycle-life performance. The simple mechanochemical method described in this study will shed light on cost-effective synthesis of high-capacity silicon oxides as promising anode materials.

• Journal of the Korean Electrochemical Society
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• v.5 no.1
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• pp.30-38
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• 2002

Disordered carbon and boron-substituted disordered carbons $C_{l-x}B_x(x=0.05,\;0.10,\;0.20)$ were synthesized by Pyrolysis of LPG(liquid Propane gas)and $BCl_3$. Their electrochemical properties as anode materials for Li-ion secondary batteries were then investigated. When PVDF is added to the sample in a weight ratio 5 : 95, the disordered carbon with x=0.00 had the first discharge capacity 374 mAh/g. Its cycling performance was relatively good from the second cycle and it had the discharge capacity 258 mAh/g at the 10th cycle. When PVDF is added to the sample in a weight ratio 5 : 95, the sample with x=0.05 among the samples $C_{l-x}B_x(x=0.05,\;0.10,\;0.20)$ exhibited the largest first discharge capacity 860 mAh/g and discharge capacity 181 mAh/g at the 10th cycle. All the samples had similar cycling performances from the second cycle. The sample $C_{0.90}B_{0.10}$ showed the best electrochemical properties as a anode materials fur Li-ion secondary battery from the view points of the first discharge capacity(853 mAh/g when $10w1.\%$ PVDF is used), cycling performance, discharge capacity(400mAh/g at the 10th cycle when $10wt.\%$ PVDF is used). All the samples showed generally larger charge and discharge capacities when $10wt.\%$ PVDF ratter than $5wt.\%$ PVDF is used. The plateau region in the range of voltage lower than 1.25V becomes larger probably since the structure becomes less disordered by the addition of boron. When boron is added, the charge and discharge capacities decreased suddenly at the second cycle. This may be become only a part of Li are reversibly deintercalated and intercalated and a part of Li which are strongly combined with B are not deintercalated. The increases in charge and discharge capacities are considered to be resulted from the increase in the potential of Li in the boron-added carbons, caused by the strengthening of the chemical bond between the intercalated Li and the boron-carbon host since the boron acts as electron acceptor.

• Journal of the Korean Electrochemical Society
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• v.16 no.2
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• pp.59-64
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• 2013

Using $Na_2CO_3$ and $MeSO_4$ (Me = Ni, Co and Mn) as starting materials, the precursor of $[Ni_{0.6}Co_{0.2}Mn_{0.2}]CO_3$ has been synthesized by carbonate co-precipitation. The precursor was mixed with $Li_2CO_3$, and calcined at 750, 850, and$950^{\circ}C$ in air. Effect of calcinations temperature on characteristics of $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ cathode materials was investigated. The structure and characteristics of $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ were determined by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and electrochemical measurements. The X-ray diffraction (XRD) results show that the intensity ratio of $I_{(003)}/I_{(104)}$ increased and the R-factor ratio decreased with the increase of calcinations temperature. And Scanning electron microscopy (SEM) result show that the primary particle size increased. Especially, the $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ calcined at $950^{\circ}C$ for 24 H shows excellent electrochemical performances with reversible specific capacity of $165.3mAhg^{-1}$ [cut-off voltage 2.5~4.3 V, 0.1 C($17mAhg^{-1}$)] and good capacity retention of 95.4% after 50th charge/discharge cycles[cut-off voltage 2.5~4.3 V, 1 C($170mAhg^{-1}$)].

• Journal of the Korean Electrochemical Society
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• v.17 no.2
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• pp.103-110
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• 2014

In the study, a room temperature ionic liquids as a co-solvent was used to evaluate the feasibility with various electrodes in Li-ion batteries. 1-Ethyl-1-methyl piperidinium bis(trifluoromethanesulfonyl) imide(PP12 TFSI) is an ionic liquid that melts at $85^{\circ}C$. Pure PP12 TFSI is not able to be used as an electrolyte because it is a solid salt at room temperature. PP12 TFSI is mixed with EC/DEC(1/1 vol.%) to prepare mixed solvents. The electrolyte 1.5M $LiPF_6$ in a mixed solvent having 44 wt.% PP12 TFSI is prepared to evaluated the various electrodes. The electrolytes provides good cycles life of cells with $LiNi_{0.5}Mn_{1.5}O_4(LNMO)$, $LiFePO_4(LFP)$, $Li_4Ti_5O_{12}(LTO)$ and artificial graphite. Further improvement of the cell performances can be accomplished by enhancing wettability of electrolytes to electrodes.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.280-288
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• 2017

Nanocarbon base materials such as, graphene and graphene hybrid with high electrochemical performances have great deal of attention to investigate flexible, stretchable display and wearable electronics in order to develop portable and high efficient energy storage devices. Battery, fuel cell and supercapacitor are able to achieve those properties for flexible, stretchable and wearable electronics, especially the supercapacitor is a promise energy storage device due to their remarkable properties including high power and energy density, environment friendly, fast charge-discharge and high stability. In this study, we have fabricated flexible supercapacitor composed of graphene/conductive polymer composite which could improve its electrochemical performance. As a result, specific capacitance value of the flexible supercapacitor (unbent) was $198.5F\;g^{-1}$ which decreased to $128.3F\;g^{-1}$ (65% retention) after $500^{th}$ bending cycle.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.191-198
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• 2018

SnSb alloy powders with excess Sn or Sb are fabricated by the high energy ball-milling of pure Sn and Sb powders with different Sn/Sb molar ratios, and then their material properties and lithium electrochemical performances are investigated. It is revealed by X-ray diffraction that SnSb alloys are successfully synthesized, and the powder size is decreased via ball-milling. Charge-discharge test using a coin-cell shows that the best result, in terms of the cyclability and the capacity after 50 cycles, comes from the electrode composed of Sn : Sb = 4 : 6, i.e. the capacity of $580mAh\;g^{-1}$ after 50 cycles. When the electrode is composed of Sn : Sb = 3 : 7, however, the capacity is noticeably decreased by the restrained Sn reaction with Li-ion. The pure SnSb alloy powders (Sn : Sb = 5 : 5) results in the second best performance. In the case of Sn-rich SnSb alloys, the initial capacity is relatively high, but the capacity is quickly fading after 20 cycles.

• Applied Chemistry for Engineering
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• v.26 no.5
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• pp.543-548
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• 2015

Si/C/CNF composites as anode materials for lithium-ion batteries were examined to improve the capacity and cycle performance. Si/C/CNF composites were prepared by the fabrication process including the synthesis and magnesiothermic reduction of SBA-15 to obtain Si/MgO by ball milling and the carbonization of phenol resin with CNF and HCl etching. Prepared Si/C/CNF composites were then analysed by BET, XRD, FE-SEM and TGA. Among SBA-15 samples synthesized at reaction temperatures between 50 and $70^{\circ}C$, the SBA-15 at $60^{\circ}C$ showed the largest specific surface area. Also the electrochemical performances of Si/C/CNF composites as an anode electrode were investigated by constant current charge/discharge test, cyclic voltammetry and impedance tests in the electrolyte of LiPF6 dissolved in mixed organic solvents (EC : DMC : EMC = 1 : 1 : 1 vol%). The coin cell using Si/C/CNF composites (Si : CNF = 97 : 3 in weight) showed better capacity (1,947 mAh/g) than that of other composition coin cells. The capacity retention ratio decreased from 84% (Si : CNF = 97 : 3 in weight) to 77% (Si : CNF = 89 : 11 in weight). It was found that the Si/C/CNF composite electrode shows an improved cycling performance and electric conductivity.

• Journal of the Korean Applied Science and Technology
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• v.36 no.4
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• pp.1253-1258
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• 2019

The solid-state electrolyte based on polymer is applicable to various electrochemical devices including supercapacitor, battery, sensor, actuator and has great attention to develop its ionic conductivity from conventional polymer electrolyte by uisng wide range of ionic liquids. The research about ion gel as a solid state electrolyte with the ionic liquid has focused on the wearable and flexible electronic device to use as the high electrical and electrochemical performances, mechanical strength of polymer. In this work, we have investigated and developed solid-state electrolyte based on the ionic liquid and polymer with enhanced ionic conductivity and stability.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.746-752
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• 2016

In this study, soft carbon was prepared by carbonization of carbon precursor (pitch) obtained from PFO (pyrolysis fuel oil) heat treatment. Three carbon precursors prepared by the thermal reaction were 3903 (at $390^{\circ}C$ for 3 h), 4001 (at $400^{\circ}C$ for 1 h) and 4002 (at $400^{\circ}C$ for 2 h). After the prepared soft carbon was ground to a particle size of $25{\sim}35^{\circ}C$, the soft carbon was synthesised by the chemical treatment with boric acid ($H_3BO_3$). The prepared soft carbon were analysed by XRD, FE-SEM and XPS. Also, the electrochemical performances of soft carbon were investigated by constant current charge/discharge test, cyclic voltammetry and impedance tests in the electrolyte of $LiPF_6$ dissolved inorganic solvents (EC:DMC=1:1 vol%+VC 3 wt%). The coin cell using soft carbon of $25{\sim}35^{\circ}C$ with 3903 soft carbon ($H_3BO_3$/Pitch=3:100 in weight) has better initial capacity and efficiency (330 mAh/g, 82%) than those of other coin cells. Also, it was found that the retention rate capability of 2C/0.1C was 90% after 30 cycles.