There are standard formats for cells in Lithium-based chemistries, but they are different sizes then the Ni-based ones because of the entirely different voltage

There are standard formats for cells in Lithium-based chemistries, but they are different sizes then the Ni-based ones because of the entirely different voltages. How (not) commonly they are used tells you something how much industry cares about avoiding many different sizes. (part of it is probably also that round cells are space-inefficient in devices that aren't tube-shaped - most common consumer use cases where the consumer handles individual cells are flashlights and vape devices, and some markets do have proprietary designs as de-facto standards) Some manufacturers also make Li-Ion replacements for multi-AA devices, but thats then specific to manufacturer and device and the exact placement it expects.