Currently playing Factorio 1.1.110 with no other mods currently installed; it fails to load and returns this error message:

Failed to load mods: Path PlutoniumEn2.5ergy/graphics/entity/MOX-reactor/MOX-reactor-connect-patches-heated.png does not match any enabled mod.: PlutoniumEn2.5ergy/graphics/entity/MOX-reactor/MOX-reactor-connect-patches-heated.png; mods: PlutoniumEnergy

Known issue for 1.1. Happens with low-resolution graphics. I'm planning to make a new 1.1 release based on the latest 1.7. and then release 1.8 to be the 2.0 branch. For now you can use this version I already patched: https://github.com/JohnTheCoolingFan/PlutoniumEnergy/releases/download/v1.7.0-quickfix-1/PlutoniumEnergy_1.7.0.zip

Working on a 1.1 version that fixes bugs and includes improvements made since 1.7.0
Posted about it on my discord, but will also post here: https://github.com/JohnTheCoolingFan/PlutoniumEnergy/releases/download/v1.7.16-beta-1/PlutoniumEnergy_1.7.16.zip

Would be nice if you could check it out and report if there's any issues with it. Tested both with normal and high resolution sprites. Still could've missed something, and I don't want to re-release a 1.1 version.

Uplaoded the files to github pre-releases, because discord links will eventually fail.

Released 1.7.16, which should work for factorio 1.1