This method should help there in order to change something and hopefully properly re-calibrate your currently used battery:
By taking out Librem 5 battery and after some seconds putting it back into its slot you might expect that noted battery percentage changed to some other value, but this is not important for you (but for the used battery of course, I guess). What is important that you do (watch/wait for around four hours) is to keep your Librem 5 charging until the red LED light turn off (100%). Please note that your Librem 5 battery by doing so cannot overcharge (I’m quite sure), so do not worry much about when to disconnect USB-PD cable from Librem 5. If you need your Mobile connection you can leave this Librem 5 on (recommended without WiFi on, not to add some slightly higher heat), but if late evening you can turn it off as well (without disconnecting charging cable before red LED off).
Once red LED light off you need to disconnect USB-PD charging cable and have three options to power on your Librem 5 again:
−− short holding of power-on button (up to 4 seconds),
−− taking out of Librem 5 battery and putting it back again.
−− Third option should not be used when battery having full capacity.
Please use provided (original) power supply (high amperage one). Hope this helps as it is more about how you behave toward your Li-ion battery and not the other way around. Please power off when battery percentage under 30%, especially 20%, and not about to be used (just do something if not about to recharge Librem 5 battery soon again). Just avoid getting into same described scenario (as I see it) again.