I don’t think that a phone charger would work anyway as the laptop needs a 20V DC supply from the charger and even though the phone charger has a USB-C plug most phone chargers only supply 5V DC
Here’s the hardware maintenance manual for the laptop.
On p.30 it shows how to test the battery. If the battery is discharged then it may be due to a faulty DC-In cable -example only. and not that it is a faulty battery
Go to p.95 to view the necessary pre-requisite steps and then the procedure to remove/replace the DC-In cable. Disconnect the cable plug from the motherboard and use an Ohmmeter to prove continuity from the socket to the cable plug
If the DC-In socket is faulty the part number is 00UR507. The part number was found from this link showing the parts for the laptop. (click on Select Commodities > Cables Internal (23) > p.2 at the bottom of the list to find CABLE,CONN SET,12D,Amphenol. The supplier in the link above was only to show what the part looked like and how much it may cost. There are other suppliers online that may suit you better. Just search for 00UR507 to find suppliers that suit you.
Once you have access to the internal components check the RTC battery as well. See p.31 of the manual for how to do this.
If all the above checks test OK then try a power refresh to see if this resolves the problem.
Disconnect the charger if connected, remove the main battery, remove the RTC battery.
Press and hold the laptop power button for 30 seconds and release.
Reconnect the RTC battery, reconnect the main battery, reconnect the charger and try to turn on the laptop.
If it turns on allow it to fully boot and then check the charge status of the battery. If it is charging, allow it to fully charge before disconnecting the charger. Also create a Win 10 battery report to check the state of the battery.