The battery does help a camera body autofocus an EF lens faster.
From Chuck Westfall… “In addition, the EOS-1D X achieves a higher lens motor drive speed with select L-series USM telephoto lenses than the 5D Mark III because of the 1D X’s more powerful battery pack.” [source]
Some discussion has come up about AF performance being affected by battery voltage. The LP-E4 style batter in the 1D series is 11.1 volts, while the LP-E6 is 7.2 volts. I do not have the technical papers of the relationship between voltage and AF performance on for EF lenses. If such an article exists, I would love to see it. We were passing on information that came to us from a new source.
What to expect?
We’ve received some interesting information about the development of the EOS 7D Mark II.
We’re told at least one variation of the camera being developed has an integrated grip, really making it a “Baby EOS-1D X”. We’re told that the larger battery seen in the EOS-1D X is part of the reason it will autofocus bigger lenses better than a camera with say an LP-E6. If this is going to be targeted at sports and wildlife photographers, the bigger battery makes a lot of sense. I would expect the camera to be somewhat smaller, as the mirrorbox and prism wouldn’t need to be as large. It’s sounding like Canon is really going to test how much people are willing to spend on an APS-C body.
It is a 2013 camera by all indications, most likely the late summer/early fall.
No other specifications were mentioned.