Not that I can find any info on, no. The N96 came with a 950mAh BL-5F battery - you could cram the 1200mAh BL-6F battery into it, but it was never sold with that. The N95 8GB also had a higher capacity battery than the original N95, but that wouldn't fit properly in the older model.

In the early days, moving from NiCad to NiMH, and more recently from NiMH to Lithium batteries, you could get higher capacity replacements (though I'm not aware of the original manufacturers releasing these), but things have been pretty steady for a while now. The latest advancements seem to be more in the area of charge rate and life span, rather than capacity.