Doyoung Seung

Effect of silica on the electrochemical characteristics of the plasticized polymer electrolytes based on the P(AN-co-MMA) copolymer

Abstract Composite polymer electrolyte films consisting of poly(acrylonitrile-co-methyl methacrylate) (P(AN-co-MMA)), EC–PC, LiClO 4 salts, and also silica particles have been prepared, and their electrochemical properties were studied. A maximum in the ion conductivity was found for the plasticized polymer electrolyte containing 10 wt% silica with EC–PC and was 1.7×10 −4 S/cm at −15°C and 1.9×10 −3 S/cm at 25°C. The reduction in T g of the plasticizer-rich phase in the composite polymer electrolytes due to the interaction between the added silica and lithium cation seems to be a main reason for the initial increase of the ion conductivities with the increase in the silica content. The decrease in the ion conductivity with the silica content at the higher silica content is expected to be attributed to the increase of viscosity of the plasticizer-rich phase and the decrease in the charge carrier numbers. The stability of interfacial resistance between the composite polymer electrolyte and the lithium electrode was found to be enhanced with increase of the silica content in the range studied.

Electrochemical characterization of a new high capacity cathode

Abstract This paper reports on the electrochemistry of a new series of layered manganese oxide cathodes for lithium-ion cells. The layered structure is stabilized by the partial substitution of the manganese by chromium and lithium atoms and by the partial or complete oxidation of the manganese to the +4 oxidation state. The series covers the range of compositions Li x Cr y Mn 2− y O 4+ z for which 2.2 x y z ≥0.

Redox shuttle additives for chemical overcharge protection in lithium ion batteries

We disclosed that a few kinds of aromatic compounds having thianthrene derivatives with acetyl or other functional groups were stable up to about 4.2-4.3 V against lithium. These materials, called redox shuttle, have lately been employed as a chemical overcharge protection agent that consumes the excess current during battery overcharge. They oxidized above 4 V and worked as redox shuttle when introduced into the electrolyte of a Carbon/LiCoO2 prismatic battery within less than one hour rate (1C). We also studied thermal properties of batteries containing the above-mentioned materials with ARC (Accelerating Rate Calorimeter). We ascertained that the current supplied over the full charge was not stored, but instantly and quite completely consumed in an oxidation-reduction reaction.

Rational design of ordered mesoporous carbon with controlled bimodal porosity via dual silica templating route

Combining both nano-replication and nano-imprinting techniques using dual silica templates provides a simple way to synthesize ordered mesoporous carbons with bimodal pore size distributions ( approximately 1.5 nm and approximately 3.5 nm).

Direct sulfonation of ordered mesoporous carbon for catalyst support of direct methanol fuel cell

Ordered mesoporous carbon (OMC) prepared by nano-replication method was directly functionalized with sulfonic acid group by using the ammonium sulfate salts. PtRu nanoparticles below 3 nm was supported on the sulfonated-OMC support with 70 wt% loading, and the resulting catalysts exhibited promising catalytic activity for methanol oxidation reactions.

Ordered mesoporous carbon as new support for direct methanol fuel cell: controlling of microporosity and graphitic character

As a new carbon support for the fuel cell, ordered mesoporous carbon (OMC) was prepared by the nano template method using ordered mesoporous silica. The structural properties of OMC such as microporosity and graphitic character were controlled by addition of nano silica powder during synthesis of OMC or the uses of different carbon precursors. The performance of direct methanol fuel cell in the single cell was affected significantly by the graphitic character of OMC support.