iCloud for old photo storage only

I have an external hard drive with thousands of old photos from my digital camera days. I would like them to be saved on iCloud so I have a backup version just in case. I do not want all of these photos on my phone- I just want to access them when I log into iCloud. I have plenty of iCloud storage but not so much on my phone (even with optimizing). Is there a way for these old photos to be separately stored on iCloud only and to just continue my current photo syncing between my phone and iCloud?