EVE Energy offers a lot of energy and extremely low self-discharge with non-rechargeable lithium thionyl chloride 3.6V batteries, so that a battery change does not have to happen during the life of the device. In that case, the designer can choose to solder the primary lithium cell directly to the PCB instead of placing it in a removable holder.
In addition to common elongated cylindrical cells with solder lips, there are also compact prismatic cells in a rectangular shape:
EF651615 400mAh 16.8×15.8×6.8mm
EF651620 500mAh 16.8×20.1×6.8mm
EF651625 800mAh 16.8×25.8×6.8mm
EF702338 1600mAh 23.3×38.3×7.2mm
And so-called wafer cells, like a round disk:
ER22G68 400mAh Ø22.6×8.0mm
ER32L65 1000mAh Ø32.9×7.1mm
ER32L100 1700mAh Ø32.9×10.5mm
In addition to the 3.6V lithium thionyl chloride, EVE also has lithium manganese oxide in 3.0V in many versions and even as a pouch pack.