Advice needed on 20-series battery "Power Pack"

[Matt Kernal]

I picked up an HP 20-series "Power Pack" (external battery recharger) device along with the Ni-Cd AA battery/holder.

The problem is that years ago, somebody left the battery in the recharger, and it has leaked/disharged to the point where the battery is stuck in the recharger.

Since it's too frozen to muscle it out with brute force, and I don't want to damage the plastic by prying it out, how can I remove the battery from the Power Pack? Can it be submerged in some kind of mild solution (like citric acid or distilled water) that doesn't damage the plastic or electronics, so the parts can be separated?

Any advice would be appreciated.

Thanks,
Matt