Organic compounds with heteroatoms as overcharge protection additives for lithium cells

Various organic compounds with heteroatoms (N, O, F, Si, P, S) were tested as overcharge protection additives for 4-V class lithium cells. It was found that trimethyl-3,5-xylylsilane exhibited preferable oxidation potential (E-ox) as overcharge protection additive, and charge-discharge cycling efficiency (Eff) of lithium anode in electrolyte with arylsilanes was as high as tolyladamantanes, reported previously by us. From room temperature to 60 degrees C, E-ox of trimethyl-3,5-xylylsilane decreased only 0.07 V. Difference in E-ox among regioisomers of tolyltrimethylsilanes is smaller than that among tolyladamantanes. H-1 NMR and UV spectra suggest the steric repulsion between tolyl group and trimethylsilyl group in o-tolyltrimethylsilane is smaller than that of the related substituents of o-tolyladamantane. (c) 2006 Elsevier B.V. All rights reserved.