Low contact resistance carbon thin film modified current collectors for lithium Ion batteries

Carbon films have been synthesized by chemical vapor deposition (CVD) on AISI 304 stainless steel (304SS) sheets with various C2H2/H-2 flow ratios at 810 degrees C. The films exhibit three different morphologies and structures: filament, sphere and transition types at different C2H2/H-2 flow ratios, as characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. It was found that the degree of graphitization increased with decreasing C2H2/H-2 flow ratios. The carbon film modified 304SS sheets were used as cathode current collectors and coated with an active layer containing LiMn2O4 active materials, conducting additives and binders for lithium ion batteries. The electrochemical properties of these LiMn2O4 cells with bare and carbon film modified current collectors were investigated. Under high current operation, such as 3000 mA/g, the capacity of the LiMn2O4 cell with transition type carbon film modified current collector is 55% higher than the cell with bare current collector. The enhanced performances of high current density charge-discharge cycles can be attributed to the reduced contact resistance and improved charge transfer efficiency provided by the transition type carbon film modified current collectors. (C) 2014 Elsevier B.V. All rights reserved.