This is according to analyst Ming-Chi Kuo who wrote in an investor note seen by MacRumors. According to Kuo, “The new 2H21 iPhone models feature a larger battery capacity than the iPhone 12 series, thanks to the space-saving design of many components. Hence, the new 2H21 iPhone models are also slightly heavier than the iPhone 12. The space-saving design includes integrating the SIM card slot with the mainboard, reducing the front optical modules’ thickness, etc.”
Kuo does not mention exactly how much bigger of a battery we could be looking at, so it remains to be seen how big of a difference in battery life we’re talking about. That being said, it should be noted that usually new features in phones can also take up battery, which means that larger batteries might be used to make up for the additional drain and might not necessarily result in any massive gains.
We’re talking about potential features like a built-in Touch ID sensor and also a display with a higher refresh rate, all of which will no doubt have an effect on the battery.