Hot Ambient project up to 170 F

I am working with a project to be use inside a trailer, during the summer temperatures outside can hit 116 F and inside the trailer can reach 170 F, the project uses a battery.
Any recommendations on the type of battery to use? (currently, I am using a Lithium-Ion Polymer Battery - 3.7v 2500mAh) and maybe some recommendations on the type of enclosure?. Its a small project maybe 3" x 6" x 1".

Search for battory + extended temperature range and read the specificatuions.