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.
18650 is awesome, a good balance of weight to capacity. They are the standard cells used in laptops, vapes, small powerbanks, power tool batteries, and so on. They can also go into a fairly standard charger for AA and AAA batteries and give a lovely nominal 3.7V.
That said, pouches are better for inside a device like a controller. The weight of a battery is significantly influenced by the casing. A pouch is almost entirely capacity, a cell like an 18650 or AA is largely the metal of the casing. If you have the pouch inside the plastic of the device you can save that weight.
I think laptop batteries are usually thinner than 18650s? All the ones I've seen are, anyway
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?
Pouch cells suck, there are no standard sizes and they like to puff up and break open the case of whatever they are inside of.