Development of carbon conductive additives for advanced lithium ion batteries

The newly developed conductive carbon blacks C-NERGY™ Super C65 and C-NERGY™ Super C45 were studied with regard to their performance as conductive additives in positive lithium ion battery electrodes and compared to other reference conductive carbon blacks. The lowest electrical volume resistivity and highest compressibility were found for C-NERGY™ Super C45 dry-mixed with LiCoO2 powder. Mixing by high shear forces in acetone dispersion improved the electrical resistivity and compressibility of the C-NERGY™ Super C65 containing LiCoO2 mixture to the same level obtained for the C-NERGY™ Super C45 mixture in the same process. Acetone dispersions of C-NERGY™ Super C45 and LiCoO2 showed the lowest viscosities attributed to the carbon black's specific BET surface area of 45 m2 g−1 being the lowest of all carbon blacks studied. The easy dispersibility of C-NERGY™ Super C45 in LiCoO2 could be explained by its particular surface group chemistry characterized by time-of-flight secondary ion mass spectrometry. The electrical volume resistivity of the LiCoO2/carbon black mixtures was in line with the high current rate performance of half-cells with related LiCoO2 electrodes. Compared to the investigated carbon blacks, the electrical volume resistivity of the graphite conductive additives C-NERGY™ KS6L and C-NERGY™ SFG6L at different concentrations in LiCoO2 powders showed higher critical volume fractions but lower ultimate resistivity levels. Adding one of these graphites to the carbon black conductive mass improved the electrode density and, at concentrations above the critical volume fraction of the graphite component, significantly decreased the ultimate resistivity level of the LiCoO2 electrode mass.