A drop of gasoline, a match, and a battery all store energy, but only the battery is recyclable after it has expended its energy. This is because, chemically speaking, a dead battery is not much different from a fresh one. Most batteries we use today make use of metals that either release or accept electrons. For example, in an alkaline double-A battery, zinc metal reacts with hydroxide ions to form zinc oxide and release electrons at the negative terminal. The electrons travel through a device, such as a light bulb, and then return to the positive terminal where they are accepted by manganese dioxide. Different batteries use different combinations of metals and non-metals, such as graphite, in order to generate a stream of electrons.
Almost all batteries, including single-use batteries, are theoretically rechargeable since the metals and chemicals are still present. However, trying to recharge a single-use battery results in a variety of side reactions that produce contaminants, reducing the battery’s capacity and potentially damaging its internal structure. Rechargeable batteries are engineered to avoid these issues. For example, in a lithium-ion battery, lithium ships give up electrons to power the circuit and then dock at the other side of the battery. Over time, some of the lithium ion ships veer off course and engage in side reactions, reducing the battery’s efficiency.
Recycling batteries is important since it prevents potentially toxic battery metals from leaking into the environment. It also conserves resources, as Earth has only 22 million tons of lithium, enough for about 2.5 billion EVs. However, most lithium-ion batteries are not manufactured with recycling in mind, and so currently only 5% of lithium-ion batteries are recycled. Regulations that clearly define who is responsible for a spent battery and what should happen to it can boost recycling dramatically. For example, lead-acid batteries are generally subject to stringent regulations and are recycled at much higher rates than lithium-ion batteries. Over the next century, we’ll need to recycle huge numbers of EV batteries, so scientists are working on making the battery recycling process cheaper and more environmentally friendly. Smelting uses a lot of energy and, depending on the type of battery, can release harmful by-products. In addition to regulations, industrial processes, and our own individual choices, battery tech will also continue to evolve. There are proof-of-concept batteries being developed that can convert physical force, ambient sound, and even pee into electricity. However, if your top priority is to make your number one source of power, you may have to wait a long time.