Changes of anode materials during extended cycling of lithium ion batteries

Abstract EN

Experimental data on lithium ion batteries with LiCoO2 as cathode and SSG (a modified natural graphite) as anode showing good uniformity, high capacity and good cycling behavior are reported.

Three cells were cycled for 500, 1060 and 1600 cycles, the changes of the graphitic anode material were investigated by X-ray diffraction, scanning electronic microscopy, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and capacity measurements in order to identify the mechanism of capacity fading of these lithium ion batteries.

During cycling, the graphitic structure is very stable and evidently does not change.

However, the electrolyte solution continuously reacts with the anode material during cycling and the thickness of the surface film on the anode material increases with cycling, which leads to a change of the surface composition, increase of charge transfer resistance and decrease of the height of redox peaks in cyclic voltammograms.

The comparison of the capacity fading of the anode material and the complete lithium ion batteries shows clearly that the anode mainly contributes to capacity fading of lithium ion batteries due to reactions of electrolyte solution constituents with the anode material during cycling.

These results provide valuable clues for manufacturing lithium ion batteries with improved cycling behavior.