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德国马普所Samuelis-Ionic / electronic wiring of lithium ion battery electrodes

Time : 
Wed, 06/27/2012 - 09:30
Location : 


The storage kinetics of electrode materials for lithium ion batteries critically depends on the chemical diffusivity of Li in these materials. The two major transport processes included in this chemical diffusivity of Li are the transport of Li+ ions and the electronic conductivity of the material. Promising materials such as LiFePO4 or  TiO2 suffer from intrinsically low electronic conductivities, rendering the pure materials unusable as electrodes. Here, superimposing networks of electronically conductive second phases can help improving the electron transport in such electrodes.

This contribution presents some concepts to improve the Li transport properties in electrode material, while keeping volume demands for secondary phases low. I report on novel electronic/ionic mixed conducting networks of anatase TiO2-δ nanoparticles formed by thermal treatment in hydrogen atmosphere. A major effect of the hydrogen-thermal treatment is the reduction of stoichiometric TiO2 nanoparticles in the surface-near region of the particle, giving rise to the formation of n-type charge carriers close to the surface. The treated anatase particles show double to almost triple capacities compared to stoichiometric anatase, and also rate capabilities are strongly enhanced. At the same time, there is no volume loss for a secondary electronically conductive phase. We compare to conductive network formation by mixed electronic/lithium conducting oxides. Furthermore we also report on electrospinning techniques employed to create 1-d electrode structures with excellent electronic wiring and good access for the Li+ ions.



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