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In this paper we report results of a synthesis method of thin-film conductive carbon coatings on LiNi1/3Co1/3Mn1/3O2 cathode active material powders for lithium-ion batteries. Thin layers of graphitic carbon were produced from a solid organic precursor, anthracene, by a one-step microwave plasma chemical vapor deposition (MPCVD) method. The structure and morphology of the carbon coatings were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The composite LiNi1/3Co1/3Mn1/3O2 electrodes were electrochemically tested in lithium half coin cells. The composite cathodes made of the carbon-coated LiNi1/3Co1/3Mn1/3O2/C powder showed superior electrochemical performance and increased capacity compared to standard composite LiNi1/3Co1/3Mn1/3O2 electrodes. [ABSTRACT FROM AUTHOR]

Several LiFePO4/C composites were prepared and characterized electrochemically in lithium half-cells. Pressed-pellet conductivities correlated well with the electrochemical performance in lithium half-cells. It was found that carbon structural factors such as sp²/sp³ and disordered/graphene (D/G), as determined by Raman spectroscopy, and H/C ratios determined from elemental analysis influenced the conductivity and rate behavior strongly. The structure of the residual carbon could be manipulated through the use of additives during LiFePO4 synthesis. Increasing the pyromellitic acid (PA) content in the precursor mix prior to calcination resulted in a significant lowering of the DIG ratio and a concomitant rise in the sp²/sp³ ratio of the carbon. Addition of both iron nitrate and PA resulted in higher sp²/sp³ ratios without further lowering the DIG ratios or increasing carbon contents. The best electrochemical results were obtained for LiFePO4 processed with both ferrocene and PA. The improvement is attributed to better decomposition of the carbon sources, as evidenced by lower H/C ratios, a slight increase of the carbon content (still below 2 wt %), and more homogeneous coverage. A discussion of the influence of carbon content vs structural factors on the composite conductivities and, by inference, the electrochemical performance is included. [ABSTRACT FROM AUTHOR]