ELECTROCHEMICAL PERFORMANCE OF Ni/Cu-METALLIZED CARBON-COATED GRAPHITES FOR LITHIUM BATTERIES

摘要

Synthetic and natural graphites were metallized with Cu or Ni using a fluidized bed coating and annealing process. With this method, crystalline nanometer-sized metal islands (~ 50 nm diameter) were deposited onto the surface of graphite. Post-metallization, the graphite materials were cycled in lithium coin cells to determine their electrochemical properties in a propylene carbonate (PC) solvent based electrolyte. Better cycling performance (316 mAh/g active graphite, 20* cycle; 26% irreversible capacity) was obtained with the Cu-coated graphites versus Ni-coated or uncoated types (247 mAh/g, 20lh cycle; 62% irreversible capacity) in a 30% PC blend electrolyte at 50°C. The Cu nanosized deposits help to mediate charge transfer into the graphite particle via improved particle to particle contacts (electrical connectivity) and may contribute to improve kinetics of lithium ion insertion into the graphene layers by assisted Li-Cu inter-diffusion. Further, Cu may act as a de-solvation catalyst to remove PC-coordinated molecules from Li cations allowing Li insertion into grapheme layers and overall improved electrochemical performance. Carbon-coated graphite electrodes prepared by a vapor deposition process, show superior performance versus the uncoated graphite in a PC electrolyte system. Coated graphites are under investigation as possible new anodes for high-power lithium-ion battery applications.