Solid electrolyte interphase formation on metallic lithium |
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Authors: | Andrzej Lewandowski Agnieszka Swiderska-Mocek Lukasz Waliszewski |
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Institution: | 1. Faculty of Chemical Technology, Poznan University of Technology, 60965, Poznan, Poland
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Abstract: | Solutions of three salts (LiBF4, LiNTf2, LiPF6) in N-methyl-2-pyrrolidone (NMP), selected arbitrarily as a reference solvent, were investigated by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy techniques. The lithium surface in contact with LiPF6 in NMP electrolyte was covered with a protective layer (SEI) which morphology comprise small particles (of ca. 0.2 μm in radius). This salt was selected for further studies. The impedance of the Li|(LiPF6 in NMP?+?additive)|Li system was measured immediately after cell assembly and after galvanostatic charging/discharging. Fifteen different additives (10 wt.%) were used. The efficiency of individual additives was evaluated in terms of the Li|electrolyte system resistance (ΔR) or total cell impedance reduction, both deduced from EIS. Some of the additives were able to form the SEI layer and to reduce resistance/impedance of the Li|electrolyte interphase. In such cases, the lithium surface was covered with relatively uniform conglomerates, or regions separated by cracks, of ca. 1–2 μm in dimension. |
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