Sodium batteries are already in electric cars many months ago

https://www.engadget.com/the-first-ev-with-a-lithium-free-sodium-battery-hits-the-road-in-january-214828536.html

Also you could buy individual cells on AliExpress

https://www.youtube.com/watch?v=s6zcI1GrkK4

To save battery life I suppose. Also some phones may kill a background app even when told not to thus preventing messages from being received.

Probably something that does not require a phone number while still using google firebase notification system? Basically a less buggy version of session messenger.

From my understanding briar requires both clients to be online at the same time to use?

Sodium batteries are already in electric cars many months ago

https://www.engadget.com/the-first-ev-with-a-lithium-free-sodium-battery-hits-the-road-in-january-214828536.html

Also you could buy individual cells on AliExpress

https://www.youtube.com/watch?v=s6zcI1GrkK4