With innovations such as electric vehicles as well as laptop computers and mobile phones, we have an increasing dependence on rechargeable batteries. Many of these technologies, especially the electric vehicles, boast high efficiency and environmental friendliness, since energy conversion in batteries does not have the limits in traditional heat engines, and the vehicles do not emit gaseous pollutant.

However, can the battery based technologies really lower our ecological foot print while maintaining material comfort? Let's take a step back to examine the batteries and their environmental impact before fully embracing those innovations.

Let's discover the general principles behind a working rechargeable battery, specifics of electric car batteries as well as their environmental impact.

The rudimentary principles of a cells, working unit within batteries, have changed little over the centuries. A cell needs negative electrode, positive electrode, and electrolyte to be functional.

A good negative electrode is a stable conductor that can be easily manufactured at a low cost, while a positive electrode needs to be stable in contact with the electrolyte and an effective oxidizing agent. An electrolyte, on the other hand, is an insulator that has high ionic conductivity.

It also has to be cheap, safe to handle, and inert to temperature fluctuations. Most importantly, an electrolyte cannot react with the electrodes. The electrolyte is usually isolated from the rest of the battery, so the electric circuit is incomplete so the cell can retain its energy without discharging.

Once a load is connected, electrons will flow from the oxidized negative to the oxidizing positive electrode, and reduce its material. The electrolyte then becomes activated as positive ions can now flow to positive electrode while the negative ions flow in the other direction (Fig 1.a).

This process is reversed during charging (Fig 1.b), where an external power source encourages the ions to flow in a direction opposite to that of discharging, and the positive electrode is then oxidized.