  Electron-cooling offers a relatively simple scheme to enable high-luminosity
collisions in future electron-ion and hadron colliders. Contemplated TeV-energy
hadron colliders require relativistic (sub 100 MeV) high-charge [${\cal
O}(\mbox{nC})$] electron beams with a specific transverse eigenemittance
partition. This paper discusses the generation of high-charge ($Q\le 3.2$~nC)
40 MeV electron bunches with eigenemittance partition consistent with
requirements associated with electron-cooling option for future electron-ion
colliders. The supporting experiment was performed at the FAST facility at
FermiLab. The data are compared with numerical simulations and the results
discussed in the context of beam requirement for future electron-ion colliders.
