It can't be replaced. The iPhone itself doesn't have the function of replacing the battery icon
1. Search engine Cydia and Alkaline plug-ins and download and install them
2. On the page → click "Restart SpringBoard", on the setting page → click Enter
3. Open "Enabled" after entering "Alkaline" → click "Theme"
4. Select the battery icon in "Theme" → click "Alkaline" to return to the previous step, that is, change the completed power icon.