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Abstract.Rechargeable lithium ion cells operate at voltages of ~ 4.5 V, which is far beyond the thermodynamic stability window of the battery electrolyte. Strong electrolyte reduction and corrosion of the negative electrode has to be anticipated, which leads to irreversible loss of electroactive material and electrolyte, and thus strongly deteriorates cell performance. To minimize these reactions, negative electrode and electrolyte components have to be combined bringing about the electrolyte reduction products to form an effectively protecting film at the anode/electrolyte interface. This film hinders further electrolyte decomposition reactions and acts as membrane for the lithium cations, i.e., behaves as a solid electrolyte interphase (SEI). The present paper gives a review of our recent work in the field of negative electrodes in lithium ion batteries. The effects of the graphite anode surface and graphite anode surface modification on the formation of the SEI are discussed in detail by using the example: modification with carbon dioxide. 1, Introduction 1.1. Lithit,n Ion Batteries. The present development of lithium ion cells can be considered to be mainly concerned with the serious problems related to the cycling (= periodic dissolution and deposition) of metallic lithium negative electrodes (anodes) in rechargeable batteries.Lithium plating occurs more or less dendritically and in side reactions lithium corrosion and passivation takes place. The dendrites are covered with a passivating film and become therefore partly electrochemically inactive, which has to be compensated by a large excess of lithium. Moreover, the dendrites may form filaments which locally times that of LiC6) and have therefore been repeatedly suggested as anode materials for lithium ion batteries [4]. Unfortunately, the uptake and release of Li is accompanied by enormous volume changes (e.g., from Sn to Li22Sns: approximately 250 % volume increase; by comparison, from graphite to LiC6: only approximately 10 % volume increase), which in the case of "ordinary" coarse-grained, bulky metal host materials leads to cracking and crumbling of the electrode and hence renders an application in rechargeable batteries impossible. In recent years it has been found that only specially designed nano-structured multiphase metal hosts allow for long term "full capacity" charge/discharge cycling (for further information the reader is referred to the reviews [2][3][4]). However, all measures applied so far to improve the cycling stability of metal hosts have not yet resulted in a commercially available anode material. Carbons and in particular graphites are still the first choice anode materials. The Solid Electrolyte Interphase. Lithium ion cellsexhibit cell voltages of up to 4.5 V and therefore operate far beyond the thermodynamic stability window of the typically organic solvent-based electrolytes. Electrolyte decomposition occurs at both electrodes. Fortunately, electrolyte reduction products, created in situ during charge, form a protecting film at t...

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The synthesis of 2,6-disubstituted N,N,N',N'-tetramethyl-p-phenylenediamines (R ~Cl, Br, I, CN, or CMCSi(CH 3 ) 3 ), potential precursors/building blocks for molecular magnets, is presented. In addition to standard methods ( 1 H NMR, 13 C NMR, MS, IR, UV), the products were also characterised by means of cyclic voltammetry. Completely reversible electrochemical behaviour was observed for both the CN and the CMCSi(CH 3 ) 3 derivatives. Moreover, the corresponding radical cations and the dications were observed by cyclic voltammetry for these compounds. The first oxidation step of the Cl and the Br derivatives was also found to be reversible, although a chemical side reaction was detected after oxidation to the corresponding dication. The radical cation could not be detected for the I derivative. In this case direct oxidation to the dication followed by a chemical reaction was observed.

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