  Declining the lattice thermal conductivity in graphene is essential for its
thermoelectric applications. In high electron density systems, scatterings of
phonons by electrons are no less than the phonon scatterings by other phonons.
With the aid of first-principle calculations we examine the lattice thermal
conductivity in graphene by inducing electron-phonon scattering externally.
With experimentally tunable charge carrier density we find $\sim 50\%$
reduction of the lattice thermal conductivity at 200 K. The present study opens
up new avenues for potential thermoelectric applications of graphene.
