“To give a further example of the magnitude of the problem, the fair weather current density is stated from several sources to be approximately 3E-12 amps / meter². This means that if a square meter of conducting material was placed horizontally in the air, approximately .000000000003 amps would flow through that surface. To illustrate the problem further, if a wire (1/32inch diam., for example) was used instead of a square meter of material, the current flow would be approximately (4.95E-7meters²) *( 3E-12amps / meter² ) = 1.5E-18 amps, or .0000000000000000015 amps.” — Clifford E Carnicom, Measuring Atmospheric electricity

So much for charging a phone with energy from the ambient air.