For the current generation there is only a limited number of Lithium-ion batteries to choose from
IIRC the Leaf uses LiFePO4 and I wouldn't be too suprised if Ford went the same route
As for capacity: 23 mwhr
It'll be interesting to see how this stacks up with the Leaf. The Leaf has a 24 mwhr battery and 80 kw/110hp motor. The Focus - I think I read somewhere but I do no have a link - has ~100 wk motor and 23 mwhr battery.
Either way since Nissan has continued to screw those who reserved the vehicle last April for $100 I'm asking for my money back and going with the Focus.
Once Li-Air comes to fruition or someone finally makes a solid-state battery (i.e. EEStor - not holding my breath) that can be mass produced then we'll have the battery breakthrough that'll change everything
EDIT: Fixed the Focus's motor's power. Thanks california/klaus