Chemical and Biomolecular Engineering Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2751
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Item NEW ELECTROLYTE AND ELECTRODE MATERIALS FOR USE IN LITHIUM- ION BATTERIES(2010) Basrur, Veidhes; Raghavan, Srinivasa; Wang, Chunsheng; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Lithium-ion batteries have emerged as the preferred type of rechargeable batteries, but there is a need to improve the performance of the electrolytes and electrodes therein. Here, we report studies on new electrolyte and anode materials for use in such batteries. First, we report a class of gel electrolytes prepared by utilizing the synergistic interactions between a molecular gelator, 1,3:2,4-di-O-methylbenzylidene-D-sorbitol (MDBS), and a nanoscale particulate material, fumed silica (FS). When MDBS and FS are combined in a liquid electrolyte of propylene carbonate and lithium perchlorate, the liquid is converted into a free-standing gel due to the formation of a strong MDBS-FS network. The gel exhibits an elastic shear modulus ~ 1000 kPa and a yield stress around 15 kPa - both values far exceed those obtainable by MDBS or FS alone in the same liquid. The electrolyte also shows high conductivity (~ 5 x 10-3 S/cm), a wide electrochemical stability window (up to 4.5 V), and good interfacial stability with lithium electrode. In the second study, we describe a new polymeric binder [(poly(acrylamide-co-acrylic acid)] for use in conjunction with silicon (Si) anodes. This binder was combined with Si particles to form composite anode materials, which were then subjected to galvanostatic charge-discharge tests. Capacities exceeding 1000 mAh/g after 120 cycles have been obtained depending on the molecular weight of the binder and the concentration of the Si particles. The above binder thus presents a viable alternative to carboxymethyl cellulose (CMC), which is the current benchmark binder material for Si anodes.