Lithium Insertion in Nanoporous Carbon Materials Produced from Carbides

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Lithium Insertion in Nanoporous Carbon Materials Produced from Carbides I.M. Kotina1, V.M. Lebedev1, A.G. Ilves1, G.V. Patsekina1, L.M. Tuhkonen1, S.K. Gordeev2 , M.A. Yagovkina3 , and Thommy Ekström4 1 Petersburg Nuclear Physics Institute, Gatchina, Leningrad district, 188350, Russia 2 Central Research Institute for Materials, 191014, St. Petersburg, Russia 3 Mehanobr-Analyt Co, 199026, St. Petersburg, Russia 4 Skeleton Technologies Group, SE-12653, Stockholm, Sweden ABSTRACT In this work, the results of a study of the lithium insertion process in nanoporous carbons (NPC) obtained from carbides (SiC, TiC, Mo2C) by chlorination are presented. Lithium insertion was produced in the temperature range of 30-200 0C via the vacuum deposition and diffusion. The major analytical tools for study included nuclear reaction method and X-ray diffraction. Diffusion coefficients of lithium at this temperature interval were estimated. Possible mechanism of lithium diffusion is discussed. Investigation of phase composition of lithiated samples was carried out at room temperature. Phase composition is found to be dependent on the relationship between deposition and diffusion rates. INTRODUCTION In the past decade, significant research efforts have been focused on the search for suitable carbon materials as an alternative anode(s) for lithium rechargeable batteries. The main requirement to these materials is a high quantity of reversible lithium ion insertion. This property appears to be a function of the carbon network structure [1-2]. The structural variation of carbon materials also plays an important role in the stoichiometry and phase composition of the lithiated carbons. In this paper, the process of lithium insertion in nanoporous carbons (NPC) obtained from carbides (SiC, TiC, Mo2C) by chlorination is studied. These materials are of interest for their high-developed surface (total porosity is up to 70%) on which lithium deposition can take place and for high open nanoporosity that makes it possible to have enough value of lithium diffusion coefficient. The objectives of the study are to determine lithium diffusion mechanism and the factors that affect the stoichiometry and phase composition of lithium insertion in NPC. EXPERIMENTAL The samples used in this study (bulk NPC) were obtained through the temperature chlorinating process from an intermediate product prepared on the base carbide powders (SiC, TiC, Mo2C). These materials have high total porosity up to 70% and nanoporosity about 50%. Their specific surface area is up to 1300 sm2 / g. Pore sizes and value of graphitised fragments in bulk NPC under study depend on initial carbide powder [3]. So pore sizes are the largest in the npC< Mo2C>B samples and are the smallest in the C< SiC>B ones. At he same time, total volume of ordered graphite fragments is the largest in the C< SiC>B samples. Lithium insertion in the samples being studied was carried out by vacuum evaporation and subsequent diffusion at the temperatures ranging from 30 oC to 200 oC. The nuclear reaction

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