Influence of lithium salts on the behaviour of a petroleum coke in organiccarbonate solutions

We studied the influence of the anion of lithium: salts dissolved in a solu tion based on propylene carbonate (PC), ethylene carbonate (EC) and dimethy l carbonate (DMC) on the electrochemical properties of a petroleum coke (LO NZA) and on the petroleum coke/electrolyte interface. We explored a correla tion between the electrochemical properties and the surface chemistry of th is coke using infrared spectroscopy, Rutherford backscattering spectrometry , fluoride selective electrode and standard electrochemical techniques. The different techniques show that LiF is a major product of the reduction of LiAsF6 and LiBF4 and a minor product of the reduction of LiCF3SO3 and LiTFS I. Alkyl carbonates are generated by reductions of the carbonate solvents t o an extent which is independent of the anion of the lithium salt. Electroc hemical behaviour of the coke is discussed with regard to the composition o f the passivating layer. We found better cycling behaviour and greater lith ium stability with LiCF3SO3 and LiTFSI. (C) 1999 Elsevier Science Ltd. All rights reserved.