I hope that this confirms to the guidelines that Silverfox has listed, but as a storage solution for myself, I store my CR123s and 3.7v+ batteries in a Surplus Ammunition Box (Dimensions are about 12-inches x 6-inches x 7-inches).
I first got the idea from a CPF supporter/retailer who sells batteries with a Pelican case. I thought it would be a ideal storage container, because it is essentially made of metal, and it would have to be a pretty tough fire to punch a hole in it. I figure that if a cell was to explode in the container, there would be enough airspace in the sealed container to prevent a catastrophic release and it is contained in the container.
But, I have been getting second thoughts because this might be a flawed theory. Would it be safe to store such batteries in such a sealed container?