There’s not really a way to keep batteries from exploding/shorting if you have them exposed to metal, and change in your pocket... Which is what happened here.

Perhaps he should have properly secured the battery before sticking it in his pocket.

Well, this isn’t an e-cig that exploded. It was the battery that belongs in an e-cig. A battery sitting in a pocket with keys, loose change, etc will do what any battery will with exposed contacts. It will short itself.