Not seen or heard of a counterbalance yet with lithium ion batteries, I do know BT / Toyota offer 4 of it's smaller indoor models with a lithium ion package.

I know Jungheinrich also offer a PPT with lithium ion.

I have heard from a good source that a forklift manufacturer is testing lithium ion on a reach truck BUT there is a compromise between the size of the lithium ion part inside the battery & the extra weight that has to be placed in the bottom of battery tank to maintain the trucks stability & capacity at height.