The layers of graphite are held together via London dispersion force. This force is weak. I know carbon having a smaller atomic radius and few electrons is one factor for this force's weakness.
But, the free electron is weakly bound with the adjacent three atoms. Does this constrains the free electron's ability to disperse, making the London force weaker?
P.S. This might be a duplicate question. Inform me if you find similar one(I haven't found any)