iPhone 6 water damage

3 month’s ago, I dropped my iphone6 in the sink with water running. I powered it off, shook out as much water as I could, blow dried it on cool setting, and left it alone for a few days. I was able to power it up after and immediately back it up. It didn’t seem to have any issues other than a slightly faster battery drain and it would take more time to charge past 95% (up to 95% took a normal amount of time). It was running on iOS 9 but I recently got an Apple Watch that required me to upgrade to iOS 11. Ever since then, my phone needs to be charged 2-3 times a day. It’s also ridiculously laggy. I know a lot of it has to do with the iOS issue as well as the battery drain from being connected to the watch. My question is, will replacing the battery help significantly? Or could the extra lag be from corrosion that a battery swap won’t help. It wasn’t laggy at all on iOS 9.