I don't know about chemicals in batteries, but Ti is pretty darn resistant to most things.

However, Ti isn't a great flashlight material for a number of reasons.

Instead of carbon-zinc, I'd look at lithium powered lights for long term storage. They have a shelf life of about ten years, are resistaint to cold.

For example, the Surefire G2 is a great deal for a very tough, bright little light.

There are also some great, low (ish) cost LED lights like this light that supports two levels, or this or this one cell light.

And the lithium cells can be had for around $1 ea. online.

-john