It's like any other rechargeable proprietary battery. If you want to keep it alive, buy replacements and replace the original when the time comes.
Incidentally this is why I recommend (and practice myself) keeping a stockpile of proprietary batteries for systems you particularly like. Over the years I have built up a small supply of nintendo-original batteries for GBA SP, New 3DS, DS Lite, and will soon be buying battery backups (if possible) for switch and maybe also my PS Vita. This is just something we have to prepare for as we prepare for anything else (like online service cancellation or HDD failure or disk lasers dying or capacitors giving out). Look up ownership for PC Engine, Sega hardware (esp. Game Gear), Playstation 1 and 2, Xbox and Xbox 360, for an easy source of much info on systems that demand some effort in their upkeep. Portables using non-standard rechargeable batteries will of course be problematic, as anyone who has had a phone battery die will tell you. It's just another fact of life if you are going to keep on with this hobby over many decades.
On the up side of the Switch is that it is dockable and can be played with wired controllers. That will keep it living long beyond the battery life.
The biggest pain in the butt going forward for Switch is just how many batteries will be in the mix. Just off the top of my head now:
-original switch battery
-switch lite battery
-joycon batteries
-pro controller batteries
-charge grip batteries (no doubt going to be rare too as I doubt many will buy charge grips)
To say nothing of someday if/when they bring out "switch pro" or "pro joycons" or even "VR joycons". They already have Labo and the upcoming fitness equipment to consider too. If you are a collector for Nintendo into the current century, and if you already have a lot of random Wii peripherals as part of that, then you are probably also looking at Switch now and thinking "Oh boy, here's another room of my collection for random bits of crap".
Just be happy, enjoy the system as you can, and if you really love it then buy some extra batteries and learn how to replace batteries for this kind of hardware. If you don't, then don't worry about it. Worst comes to worst, you always have docked, and that will still be better than being stuck playing a portable that is permanently plugged into a wall.