Is my S7 dead?

Hi, recently I received pretty old phone from my fellow friend. He was not charging it for about 1,5-2 years. I plugged it in, it showed gray battery icon. I waited about a hour, same. Cannot turn it on. Tried button combination reset. It's gone now and neither its showing any charging or power signs. I'm reviving it just for the feel, so I don't know if it's possible to do something or it needs parts.