- the human body resistance is considerably lower while in the water, making 5V (and enough amps) dangerous.
Don't take this as 100% medical advice, but AFAIK, although the resistance of human skin is considerably lower when wet, it is still not low enough for 5 volts to be lethal. You'd need to apply the voltage directly to your internal organs to get a serious effect.
- lithium battery capable of delivering high voltage when dropped into water while being charged.
A cell's voltage is fundamentally limited by the electochemical potential of its electrodes and can never go much above 4-5V no matter how you abuse the battery. To get a higher voltage you need an external circuit with some inductance. Or put more cells in series, but I don't think they use more than 7.4V in mobile phones.
Looking at the two articles mentioned it seems the real causes of such electrocutions are:
- The charger itself being dropped in water (which means the full line voltage going into the charger is now applied to water)
- The charger having an isolation fault which means the charger's outputs are at full line voltage relative to ground, and thus the phone's electronics. Dropping the phone in the water is thus equivalent to dropping the mains cord in the water. In fact you don't even need to drop the phone in the water if it has a non-insulated metal chassis....