Hello Esztimucus,
Thank you for reaching out to Apple Support Communities.
We were able to find this:
Preventing unexpected shutdowns
With a low battery state of charge, a higher chemical age, or colder temperatures, users are more likely to experience unexpected shutdowns. In extreme cases, shutdowns can occur more frequently, thereby rendering the device unreliable or unusable. For iPhone 6, iPhone 6 Plus, iPhone 6s, iPhone 6s Plus, iPhone SE (1st generation), iPhone 7, and iPhone 7 Plus, iOS dynamically manages performance peaks to prevent the device from unexpectedly shutting down so that the iPhone can still be used. This performance management feature is specific to iPhone and does not apply to any other Apple products. Starting with iOS 12.1, iPhone 8, iPhone 8 Plus, and iPhone X include this feature; iPhone XS, iPhone XS Max, and iPhone XR include this feature starting with iOS 13.1. Learn about performance management on iPhone 11 and later. The effects of performance management on these newer models may be less noticeable due to their more advanced hardware and software design.
More details can be found here: iPhone Battery and Performance
It may be best to reach out to Apple directly.
You can do so by going to Get Support.
They will take a closer look and check on available options.
Cheers!