Since 2020 t14/t16 thinkpads no longer have a user swappable battery without removing screws. So you can get a 50wh standard battery or 82wh. Before 2020 you could get a slightly larger 96wh battery with a bump out, plus the small internal battery.

A power bank with a usb-c 65w pd will work for most laptops. Many of these will be 100wh/20000mah or 150wh/30000mah, to meet airplane limits.

I use a T480 as my daily driver and recently upgraded to a 72wh battery after the old 24wh pack died. I bought a Lenovo-branded Total Micro battery off of CDW to ensure I was actually getting what I paid for, as the last battery was a cheap knockoff that barely lasted a year. The 72wh battery was about a $10 difference to the 48wh battery and will easily last 10 hours but could last 14 hours with conservative use.

This is the specific battery I bought: https://www.cdw.com/product/total-micro-battery-lenovo-think...