It was my second time to replace a iPhone battery. The first time was around 2017. That was my iPhone 5 smartphone. That time was successful. However, I broke the connect between the screen and phone after one-time dust cleaning. That means there is a risk to open the iPhone case.
I bought my iPhone 6 at the end of 2017, it was a used phone from Amazon. It works well but only has the problem of battery. After two year's use, I feel it is a time to replace a battery. Even I am not confidence to replace the battery easily, I still want to try. The worst situation was to buy a new iPhone and I need backup my iPhone before replacing battery.
For iPhone 6, there are two adhesive bands attached on the battery, which add difficulty of replacing. The trick was to use the heat gun to heat the phone on specific location.
Following the guide, I replaced the battery step by step. Even I was a little bit nervous, I made it at last.
No risk, you may gain nothing. For now, I have 66.7% to replace the iPhone battery for old models.