Based on the description on their site, the controller includes a built-in battery: "8.39 Wh Li-ion battery, 35+ hours of gameplay... "
That was disappointing for me. Specially condidering the Steam Frame's controllers make use of AA batteries: "One replaceable AA battery per controller, 40hr battery life"
AA Batteries might not be as convenient to use, but being able to replace them is a great advantage. All my Xbox360 controllers still work fine, but none of my PS3' Dualshock 3s.
The official docking station could be used to recharge (rechargables) AA batteries so the functionality could remain the same.
Perhaps more modern ones, but the ones in my last and current laptops are both 18650s. 6 cells, 9 cells, you stack in series to increase voltage, parallel to get more capacity, so a 3s2p would have ~14V which is more than the required 12V for internal components, no boost converters needed. That said, now they do a lot of pouch batteries which are actually multiple internal pouches run in series to get the same sort of voltage but made with the chassis fitting them perfectly, no wasted space.
Yeah I've only seen the pouch type.
How much more modern are we talking? I've a 72 whr battery in my 2017 Yoga 720 that is a slim pouch.
Or rather, how old is your last/current laptop. Or is it a workstation replacement brick?