Cheap lithium batteries are usually manufactured with little or no heed given to safety standards. There may be a chemical imbalance in the cell or the cell wall may be too rigid to permit any expansion from gas produced as the battery discharges.
Also, what is up with not selling a satnav solution for a phone with GPS? Madness!
"An idealist is one who, on noticing that a rose smells better than a cabbage, concludes that it will also make better soup." - H.L. Mencken