Most high end phone and laptop batteries nowadays have Lithium Polymer (LiPoly) batteries. If they were to short circuit the could potentially expand and burst, but not likely with the force required do break through the phone. They also don't have a rigid casing like Lithium Ion batteries which could help pressure build. Notice how when you Google "phones exploding" the only images you see are of older, or low end phones. A phone exploding is an extremely rare thing and no one should be worried about their phone blowing up unless you short circuit it intentionally.
