• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.1-8
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• 2016

Capacity of layered lithium nickel-cobalt-manganese oxide ($LiNi_{1-x-y}Co_xMn_yO_2$) cathode material can increase by raising the charge cut-off voltage above 4.3 V vs. $Li/Li^+$, but it is limited due to anodic instability of conventional electrolyte. We have been screening and evaluating various sulfone-based compounds of dimethyl sulfone (DMS), diethyl sulfone (DES), ethyl methyl sulfone (EMS) as electrolyte additives for high-voltage applications. Here we report improved cycling performance of $LiNi_{0.5}Co_{0.2}Mn_{0.3}O_2$ cathode by the use of dimethyl sulfone (DMS) additive under an aggressive charge condition of 4.6 V, compared to that in conventional electrolyte, and cathode-electrolyte interfacial reaction behavior. The cathode with DMS delivered discharge capacities of $198-173mAhg^{-1}$ over 50 cycles and capacity retention of 84%. Surface analysis results indicate that DMS induces to form a surface protective film at the cathode and inhibit metal-dissolution, which is correlated to improved high-voltage cycling performance.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.75.2-75.2
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• 2010

Polymer electrolyte fuel cells (PEFCs) have received a lot of attention as a power source for both stationary and mobile applications due to their attractive feature. In general, the performance of PEFCs is highly affected by the property of the electrodes. A PEFC electrode essentially consists of a gas diffusion layer and a catalyst layer. The gas difusion layer is highly porous and hydrophobicized with PTFE polymer. The catalyst layer usually contains electrocatalyst, proton conducting polymer, even PTFE as additive. Particularly, the proton conducting ionomer helps to increase the catalytic activity at three-phase boundary and catalyst utilization. Futhermore, it helps to retain moisture, resulting in preventing the electrodes from membrane dehydration. The most widely used proton conducting ionomer is perfluorinated sulfonic acid polymer, namely, Nafion from DuPont due to its high proton conductivity and good mechanical property. However, there are great demands for alternative ionomers based on non-fluorinated materials in terms of high temperature availability, environmental adaptability and production cost. In this study, the electrodes with the various content of the sulfonated poly(ether sulfone) ionomer in the catalyst layer were prepared. In addition, we evaluated electrochemical properties of the prepared electrodes containing the various amount of the ionomers by using the cyclic voltammetry and impedance spectroscopy to find an optimal ionomer composition in the catalyst layer.

• Membrane Journal
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• v.10 no.2
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• pp.66-74
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• 2000

In consideration that a high tensile strength and ion exchange capacity are maintained as the swelling of membrane is controlled by the coagulation of PSf with the introduction of ion exchange groups and PPSS without the introduction of ion exchange groups, the block copolymer of PSf and PPSS were synthesized. The cation exchange membrane was prepared by sulfonation with CSA and casted. The synthesized block copolymer and cation exchange membrane were characterized by FT-IR and their thermal stability was confirmed by TGA. The optimum sulfonation could be accomplished at a mole ratio of BPSf to CSA 1:3. The best electrochemical properties obtained by the optimal condition were area resistance of 4.37 $\Omega$ㆍ$\textrm{cm}^2$, ion exchange capacity of 1.71 meq/g dry membrane, water content of 0.2941 g $H_2O$/g dry membrane, and fixed ion concentration of 5.81 meq/g $H_2O$. When GBL was used as an additive, area resistance was increased by 13.7 % and ion exchange capacity was increased by 14.6%. When the membrane was fabricated in a form of composite using non woven cloth as a support. the tensile strength of membrane could be improved, but the electrochemical characteristics were not influenced.