Graphitized carbon blacks have shown a more promising electrochemical performance than the non-treated ones when being applied in small amounts as conductive additives in composite cathode electrodes for lithium ion batteries, due to the absence of surface functional groups which contribute to detrimental side-reactions with the electrolyte. Here, we report that at high potentials of >4.5 V vs. Li/Li(+), graphitic structures in carbon black can provide host sites for the partially reversible intercalation of electrolyte salt anions. This process is in analogy to the charge reaction of graphite positive electrodes in dual-ion cells. A standard furnace carbon black with small graphitic structural units, as well as slightly and highly graphitized carbon blacks, were characterized and analyzed with regard to anion intercalation. A LiPF6 containing organic solvent based electrolyte as well as a state-of-the-art ionic liquid based electrolyte composed of LiTFSI in PYR14TFSI were applied. The intercalation of both PF6(-) and TFSI(-) could be confirmed by cyclic voltammetry in electrodes made of carbon blacks. When exposed to high potentials, carbon blacks experienced strong activation in the 1st cycle, which promotes the perception for anion intercalation, and thus increases the anion intercalation capacity in the following cycles. The specific capacity from anion intercalation was evaluated by constant current charge-discharge cycling. The obtained capacity was proportional to the graphitization degree. As anion intercalation might be accompanied by decomposition reactions of the electrolyte, e.g., by co-intercalation of solvent molecules, it could induce the decomposition of the electrolyte inside the carbon and thus degradation of the carbon black graphitic structure. In order to avoid side reactions from surface groups and from anion intercalation, the thermal treatment of carbon blacks must be optimized.

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In this work, non-graphitized carbon black and graphitized carbon blacks were analyzed with regard to their performance as conductive additives in high voltage spinel Cr-doped LiNi 0.5 Mn 1.5 O 4 composite cathode electrodes. The degree of graphitization was investigated by X-ray diffraction. X-ray photoelectron spectroscopy was used to investigate the carbon black surface species and their alteration upon graphitization, as well as to the post mortem analysis of the composite cathodes. It was found that the cells with graphitized carbon blacks showed much longer cycling life. The depletion of the functional groups at the carbon black surface by graphitization apparently reduced the side reactions in the composite electrodes. Due to their superior performance, graphitized carbon black should be considered as substitute for the standard carbon black additives in the high voltage cathode electrodes.