Yes, electronic devices can charge their batteries through various methods without being plugged into a source of electricity. What all the different methods have in common is that they absorb energy that is in some other form (heat, light, vibrations, radio waves, etc.) from the external environment and then convert the energy into electrochemical energy that is stored in the device's batteries. While such methods are scientifically sound and have already been successfully demonstrated, the energy captured from the outside environment is often not enough to be practically useful. Intense research is currently underway to make energy capture more efficient, and breakthroughs are beginning to be achieved in this area. Many phones are already available that offer wireless charging. Let us look at the main types of energy a device can use to charge itself without being plugged in.

Solar panels are able to capture energy from sunlight and recharge batteries. Miniaturized solar panels are available to recharge portable electronic devices without needing to plug them into the wall. Public Domain Image, source: NASA.Solar EnergyThe oldest energy capture method used on electronic devices is most likely solar energy capture using a solar cell. Small calculators that use solar cells to help power them have been around for decades. Solar cells (photovoltaics) absorb ordinary light and convert it directly to electricity using layers of semiconductors. While photovoltaics are well understood and commercially established at this point, there are several drawbacks in using photovoltaics to recharge a handheld electronic device. The main drawback is that the light-to-electricity conversion process of photovoltaics is inefficient. Recent advances have however been made that boost the efficiency, and intense research is ongoing to continue to increase the efficiency. The other drawback is that for typical lighting levels, light does not contain that much energy to begin with. For traditional solar cells to provide reasonable output power, they have to be large in size, out in the direct sunlight for a long time, and oriented towards the sun. of these conditions is very practical for a cell phone that you keep in your pocket or your hand most of the day.