You can get them with different voltage drop-off curves

E.g., this battery is 1.5V for ~70% of the capacity, before it gradually reduce to 1.0 V

https://www.xtar.cc/product/xtar-1-5v-aa-clr-3300-lithium-ba...

edit: And one with USB-C and linearly decreasing voltage curve https://www.xtar.cc/product/xtar-aa-lithium-lr-2000mah-usb-c...