• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.279-284
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• 2021

The high theoretical specific capacity of lithium-sulfur (Li-S) batteries makes them a more promising energy storage system than conventional lithium-ion batteries (LIBs). However, the slow kinetics of the electrochemical conversion reaction seriously hinders the utilization of Li-S as an active battery material and has prevented the successful application of Li-S cells. Therefore, exploration of alternatives that can overcome the sluggish electrochemical reaction is necessary to increase the performance of Li-S batteries. In this work, an ionic liquid (IL) is proposed as a functional additive to promote the electrochemical reactivity of the Li-S cell. The sluggish electrochemical reaction is mainly caused by precipitation of low-order polysulfide (l-PS) onto the positive electrode, so the IL is adopted as a solubilizer to remove the precipitated l-PS from the positive electrode to promote additional electron transfer reactions. The ILs effectively dissolve l-PS and greatly improve the electrochemical performance by allowing greater utilization of l-PS, which results in a higher initial specific capacity, together with a moderate retention rate. The results presented here confirmed that the use of an IL as an additive is quite effective at enhancing the overall performance of the Li-S cell and this understanding will enable the construction of highly efficient Li-S batteries.

• 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 Electrochemical Society
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• v.3 no.3
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• pp.131-135
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• 2000

In order to investigate the origin of capacity fading with charge/discharge cycling in $LiMn_2O_4$ thin film battery, impedance studies have been performed with increasing cycling in $LiMn_2O_4/1M\;LiClO_4-PC/Li$ cells. The fitted values obtained from impedance data show good agreements with the experimental results. Especially, the element of charge transfer resistance of $LiMn_2O_4/liquid$ electrolyte interface initially increased, and then saturated with increasing the charge/discharge cycles, which could explain the cause of initial abrupt capacity fading of $LiMn_2O_4$ thin film with cycling due to interfacial reaction. The steady capacity fading is caused by the increasing of Warburg resistance. The chemical diffusion coefficient of Li ions decreased from $5.15\times10^{-11}cm^2/sec$ at 1st cycles to $6.3\times10^{-12}cm^2/sec$ at 800th cycles, which attributed to the Jahn-Teller distortion/Mn dissolution which diminishes tetra hedral sites necessary for Li diffusion in $LiMn_2O_4$.

• Journal of the Korean Electrochemical Society
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• v.24 no.4
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• pp.93-99
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• 2021

In order to decrease the weight of stretchable energy storage devices, interest in developing lightweight materials to replace metal current collectors is increasing. In this study, nanofibers prepared by electrospinning a conductive polymer, PEDOT:PSS, were used as current collectors for lithium ion batteries. The nanofiber showed improved electrical conductivity by using DMSO, a dopant, and indicated a stretch rate of 30% or more from the elasticity evaluation result. In addition, the use of the nanofiber current collector facilitates penetration of the liquid electrolyte and exhibits the effect of increasing the electronic conductivity through the nanofiber network. The lithium-ion battery using the DMSO-doped PEDOT:PSS@PAM nanofiber current collector indicated a high discharge capacity of 135mAh g^-1, and indicated a high capacity retention rate of 73.5% after 1000 cycles. Thus, the excellent electrochemical stability and mechanical properties of conductive nanofibers showed that they can be used as lightweight current collectors for stretchable energy storage devices.

• Membrane Journal
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• v.26 no.5
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• pp.337-350
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• 2016

Lithium-ion rechargeable batteries (LIBs) have garnered increasing attention with the rapid advancements in portable electronics, electric vehicles, and grid-scale energy storage systems which are expected to drastically change our future lives. This review describes a separator membrane, one of the key components in LIBs, in terms of porous structure and physicochemical properties, and its recent development trends are followed. The separator membrane is a kind of porous membrane that is positioned between a cathode and an anode. Its major functions involve electrical isolation between the electrodes while serving as an ionic transport channel that is filled with liquid electrolyte. The separator membranes are not directly involved in redox reactions of LIBs, however, their aforementioned roles significantly affect performance and safety of LIBs. A variety of research approaches have been recently conducted in separator membranes in order to further reinforce battery safeties and also widen chemical functionalities. This review starts with introduction to commercial polyolefin separators that are currently most widely used in LIBs. Based on this understanding, modified polyolefin separators, nonwoven separators, ceramic composite separators, and chemically active separators will be described, with special attention to their relationship with future research directions of advanced LIBs.

• Journal of the Korean Electrochemical Society
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• v.25 no.3
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• pp.95-104
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• 2022

The development of non-flammable all-solid-state batteries (ASSLBs) has become a hot topic due to the known drawbacks of commercial lithium-ion batteries. As the possibility of applying sulfide solid electrolytes (SSEs) for electric vehicle batteries increases, efforts for the low-cost mass-production are actively underway. Until now, most studies have used high-energy mechanical milling, which is easy to control composition and impurities and can reduce the process time. Through this, various SSEs that exceed the Li⁺ conductivity of liquid electrolytes have been reported, and expectations for the realization of ASSLBs are growing. However, the high-energy mechanical milling method has disadvantages in obtaining the same physical properties when mass-produced, and in controlling the particle size or shape, so that physical properties deteriorate during the full process. On the other hand, wet chemical synthesis technology, which has advantages in mass production and low price, is still in the initial exploration stage. In this technology, SSEs are mainly manufactured through producing a particle-type, solution-type, or mixed-type precursor, but a clear understanding of the reaction mechanism hasn't been made yet. In this review, wet chemical synthesis technologies for SSEs are summarized regarding the reaction mechanism between the raw materials in the solvent.

• Journal of the Korean Electrochemical Society
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• v.15 no.4
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• pp.230-235
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• 2012

Polymer electrolytes consisted of $BF_3LiMA$ and 300 (PEGMA300) or 1100 (PEGMA1100) g $mol^{-1}$ of PEGMA were prepared and the electrochemical properties were characterized. Interestingly, the AC-impedance measurement shows $1.22{\times}10^{-5}S\;cm^{-1}$ of room temperature ionic conductivity from PEGMA1100 based solid polymer electrolytes while $8.54{\times}10^{-7}S\;cm^{-1}$ was observed in PEGMA300 based liquid polymer electrolytes. The more suitable coordination between lithium ion and ethylene oxide (EO) unit might be the reason of higher ionic conductivity which can be possible in PEGMA1100 based electrolytes since it has 23 EO units in monomer. The lithium ion transference number was found to be 0.6 due to the side reactions between $BF_3$ and lithium metal expecially for longer time but 0.9 was observed within 3000 seconds of measuring time which is strong evidence of a single-ion conductor.