Tell your friend that it is a manufacturing problem up the...

Tell your friend that it is a manufacturing problem up the supply chain, not a mining supply problem, so he should not be concerned about LTR.

To answer the question, lithium batteries do produce a lot of heat, just like the ones on your mobile phone.
There are many factors which attribute to the design of a battery that will impact heat, namely the amount of current that is being drawn from the battery. ie. The more power the car drains, the more current is draw and hence more heat is produced.
The engineers have lots of ways to handle this problem. I wouldn't be too worried, otherwise companies wouldn't be investing in massive giga factories if this was a problem they don't think they can overcome.

The article also mentioned used cars so if there are any cheap modifications done then it may also cause fire in the wiring or connectors with the wrong power rating then that will also cause a problem too.

The bottom line is that there are too many factors to consider and I wouldn't be concerned about it.
Regular motor cars are just as likely to catch fire - I know I have had one catch fire!