The following result is obtained by our Internet Research Algorithm: Xiaomi uses Li-Polymer batteries which has a short lifespan, hence reducing battery life after 2 years of usage is very natural. One should not use their phones while charging, as radiation at its highest while the phone is charging also processor affects when you do heavy usage of your phone when it's charging. If you keep using your phone while charging it, it will become prone to overheating that could cause the harmful chemicals present in the battery to leak, which affects battery life as well. Hence, don't use your phone when it's charging unless it is very necessary.