We absolutely could. But we won't as manufacturers want to use batteries in shapes they want. In the case of laptops of bigger this also often ends up with th

We absolutely could. But we won't as manufacturers want to use batteries in shapes they want. In the case of laptops of bigger this also often ends up with there still being space despite them using a custom size. We were pretty close to a couple of standards of Li-Ion flat battery in the mid to late 00s, at least in Europe, due to proliferation of Nokia and Sony Ericsson. Nokia especially had some batteries that they used across several models. And the voltage and current being the same, you could also use smaller batteries in some models. The latter has been useful for the 808 PureView I have. Getting the specific battery that it used is now impossible. But it can take a very common Nokia battery with a slightly lower capacity.