This phone from Google has a 3,430 mAh battery. Kid-friendly features and durable design make it perfect for young users, but it's also a great secondary phone.
Amazon
Google Pixel 3 XL (2018) G013C 128GB - 6.3" inch - Android 9 Pie - (GSM Only, No CDMA) Factory Unlocked 4G/LTE Smartphone - International Version (Just Black)