Lithium requires SUPERVISION period. Only single cell 3.7 volts are reliably simple to manage.
Take your laptop battery apart. See all those extra wires coming from the assembled pack? They are not for decoration. They are for monitoring and control.
From the smallest >3.7 volt light to the largest motor vehicle battery bank lithium DEMANDS supervision and management. Autos have a sophisticated processor unit and sensors up the gozinta that feed data to the onboard processor.
So wanna be gyro gearlooses who try and build lithium battery banks sans management are like people who would tease each other with a vial of nitroglycerin.
"Hey Claude! Shake it and see what it does"
I tinker with LiPo and by observation have learned the chemistry is hugely unforgiving. Dead Dog or Two Alarm Fire is not the wisest way to learn.