Unique effect of mechanical milling on the lithium intercalation properties of different carbons

Abstract

The effect of the carbon precursors morphology during a mechanical grinding experiment on the physical/electrochemical properties of the resulting ball-milled carbonaceous powders was studied. These properties strongly depend on the type of grinding mode used (shear or shock-type grinding); however, for each grinding mode, they were found to be totally independent of the nature of the precursor used (graphite, carbon, coke) and/or of its morphology (layers, microbeads and fibres). Eighty h of shock-grinding was found to produce carbonaceous milled powders able to reversibly intercalate two lithiums per six carbons `Li 2C 6' while still having an irreversible capacity of 0.8 Li. The transparency of the precursor morphology and nature to mechanical grinding with carbon materials is ascribed to the strong 2D character of the graphite structure. Finally, the observed large reversible capacity in our hydrogen-free carbonaceous milled samples is explained on the basis of the previously proposed `house of cards' model.