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Batteries are the unrecognized building blocks of 21st century innovation. From keeping your smartphone working to powering laptops for portable workplaces and classrooms, batteries fuel nearly every aspect of modern life. In fact, the argument can be made that battery technology determines the speed at which our world progresses. With each battery advancement, cellphones last a little longer while performing increasingly more complex tasks, artificial hearts beat a little surer, and electric cars travel a few miles farther.
Batteries may seem simple and boring from their sleek metal exteriors. However, these unassuming miracles of science transport electrical energy to places far from the electric grid, and the story of how they work is a crucial part of the development of the technological age.
What Is a Battery?
A battery is an energy source that transforms chemical energy into a limited amount of electrical energy when its circuit is activated. Batteries use what is called direct current (DC) electricity. This differs from the alternating current (AC) that runs through home outlets in that DC only flows in one direction. This is a key aspect of batteries because the electrons they store and discharge (the definition of electrical energy) can only flow from their negative to positive terminals when in use. Since Alessandro Volta invented the first modern electrochemical cell in 1800, batteries have been the standard for portable electricity. They now exist in any mobile appliance or gadget that requires electrical energy to operate.
As we move from gas-powered vehicles and coal-driven power plants to more environmentally sustainable electric vehicles and solar-powered personal homes, battery efficiency becomes ever more important. The next stage of the technological movement, wearable technology, requires new battery innovations in order to power its small but complex devices. Batteries will soon be fueling all of the newest innovations in the future of humanity.
- Batteries: Types and History: Take a deeper dive into the history of batteries and the types that exist.
- Five New Battery Technologies That Will Change the Future: In this article, five upcoming battery technologies and the global consequences of their development are explored.
What Are the Main Parts of a Battery?
All batteries are composed of three main parts: a cathode, an anode, and an electrolyte substance to facilitate electron flow. Most modern batteries also have a separator, a collector, and electrical contacts. The separator sits between the cathode and anode, blocking these two electrodes from touching. The collector is a rod located in the cathode and is used to gather electrons that have completed the battery’s circuit. The electrical contacts are the points that connect the anode and cathode to the circuit. They are typically made of tin-plated steel or brass and are the silver ridge and indent you feel at the top and bottom of a standard household battery. The container (or jacket) may differ from battery to battery, but the elements within are largely the same.
- Diagram of Battery Parts: A labeled diagram shows a basic battery’s parts.
Why Do Batteries Need Two Different Metals?
The cathode and anode are always made of two different metals, and the reason why is found in the structure of the atom itself.
Any atom is made of three main parts: protons (positively charged), electrons (negatively charged), and neutrons (no charge). When an atom loses or gains an electron, it becomes electrically charged. All atoms and molecules naturally seek to be electrically balanced, meaning that there are an equal number or protons and electrons within. This means that atoms with a positive charge will pull electrons toward them, and those with a negative charge will seek to push the extra electrons away.
In order for a battery to function, there must be a consistent flow of electrons in the same direction. Different materials are more prone to give up or seek out electrons, and this encourages the electrons to flow between the two electrodes by traveling through the circuit the battery is connected to.
- All Elements of the Periodic Table That Can Be Used to Make Batteries: A variety of different elements can be used to create batteries.
- Matter, Electrons, and Atoms: All you need to know about matter, elements, and atoms is laid out simply in this free lesson from Khan Academy.
How Does a Battery Work?
When a battery is at full charge, all of the extra electrons are on the anode side of the battery. When the battery is connected to a circuit, electrons move from the anode into the device being powered. They then travel to the cathode of the battery. The anode and cathode are separated by a barrier within the battery to keep the electrons from flowing directly from the anode to the cathode. Both electrodes are surrounded by an electrolyte that can absorb extra positive or negative ions to keep the charges on both sides balanced.
When all of the extra electrons have moved into the cathode side of the battery, the battery is dead. Once the electrons are all on the cathode’s side, a battery must be recharged in order to be used again. Typically, this is done by using an electrical current to push the electrons back to the anode. In cars, this electrical current is generated when the car’s gas engine runs. The engine turns a generator (called the alternator), which feeds electricity back to the battery, thus refilling the anode terminal with electrons as the car rolls down the street.
- Boundless Chemistry: Batteries: This university-level text dives deep into the chemical changes that take place inside of batteries.
Types of Batteries
Batteries come in varying shapes, sizes, and strengths, from a half-volt potato battery to the 180 kg lithium-ion batteries that power the International Space Station.
Batteries can be split into two categories: primary and secondary. The difference is that primary batteries cannot be recharged, whereas secondary batteries are rechargeable.
The most common kinds of primary batteries are zinc-carbon, alkaline, and lithium. Since they cannot be recharged, once they are used up, they must be discarded or recycled. This makes them less than ideal for the environment, as the chemicals in these batteries can seep into the soil at trash depots. However, these batteries tend to contain a higher initial voltage and capacity than rechargeable ones and so need to be changed less often.
The oldest consumer battery type, zinc-carbon batteries are the standard cylindrical batteries used for flashlights or battery-powered toys. As the name suggests, they are composed of a zinc anode and a carbon cathode, which are surrounded by an ammonium chloride electrolyte solution. These batteries are inexpensive to produce and cheap to buy, but they don’t last long in comparison with other battery types. They work best for electronics that consume little energy.
While similar in appearance to zinc-carbon batteries, alkaline batteries’ potassium hydroxide electrolyte gives them a much longer run time and shelf life. Because their materials are costlier, they are significantly more expensive than zinc-carbon batteries, but the expense may be worth it if you want to keep things like TV remotes and video game controllers running longer between battery changes.
Button batteries, named after their resemblance to small silver buttons, are single-cell batteries typically made with lithium that are used in watches, hearing aids, and other tiny, low-power devices. These batteries are notorious for being dangerous, especially to children, due to how easily they can be swallowed. If a battery is swallowed and gets stuck in the esophagus, it can produce an electrical current that causes potentially fatal burns.
While they can be better for the environment, secondary batteries (or rechargeables) have tended to not last as long as primary batteries. However, battery technology has improved significantly so that rechargeables are giving primary batteries significant competition in all uses. Also, because secondary batteries have a lower internal resistance than primary, they are preferred for devices with a high current demand, such as power tools.
One negative of secondary batteries is aging and self-discharge. Self-discharge is the loss of stored energy from a battery when it sits unused. If you expect to store rechargeable batteries for extended periods of time, it’s a good idea to constantly put a low amount of charge into the battery; devices called trickle chargers can be used for this purpose. Even with good maintenance, though, a secondary battery only has a limited number of charge cycles before it can no longer be recharged.
Lead-acid batteries are most commonly used to power vehicles like cars, boats, or motorcycles. They have been around since the middle of the 19th century and are bulky, heavy, block-shaped batteries. They are able to produce the 250-amp burst required to start the average car, but they must remain charged or the batteries will become unusable.
Although all secondary batteries are good for a limited number of charges, lead-acid batteries have a particularly low lifespan, typically only 200 to 300 complete cycles. Also, the lead in lead-acid batteries is highly toxic for the environment when these batteries do need to be discarded.
Invented 40 years after the lead-acid battery, nickel-cadmium batteries are known as the most forgiving batteries of the rechargeable battery world. They have been used in everything from radios to medical equipment and power tools. However, due to the high toxicity of cadmium, environmental regulations have limited their non-commercial uses. Nickel-cadmium batteries also have a high recharge cycle count and can be stored for long periods of time (as opposed to lead-acid batteries). They also can be charged quickly without causing damage.
One major downside of nickel-cadmium is that it is subject to something called a memory effect. If the battery isn’t fully discharged before it is recharged, over time, the battery seems to “remember” the smaller amount of power that was needed before it was fully charged. Eventually, it will not provide any power past that point.
The next incarnation of nickel-cadmium, nickel-metal hydride batteries (NiMH) were developed in the 1980s. They are similar to nickel-cadmium batteries but have a higher energy capacity and are much less toxic for the environment. Because of that, they are the most available rechargeable battery for consumers. One downside is that they can be more finicky to charge than nickel-cadmium batteries and are more susceptible to self-discharging over a shorter period of time.
Lithium-ion is the newest type of secondary battery. Lithium-ion batteries were developed in the 1990s and can hold twice as much energy as a nickel-cadmium battery. They also work at higher voltages and aren’t prone to self-discharging or the memory effect. As a result, lithium-ion batteries are used in most modern electronic devices, like laptops and smartphones. However, they do tend to last for fewer charge cycles than nickel-metal hydride batteries. Also, lithium-ion batteries have been prone to internal damage that causes them to overheat and combust; exploding batteries have caused a rising number of serious injuries and even fatalities in recent years.
Fuel cells are used like batteries, but they aren’t actually batteries, as they work differently. Instead of using a sealed cell, they require the constant input of reactants to create electricity. Typically, fuel cells use hydrogen pumped to the anode and air, containing oxygen, pumped to the cathode. The small hydrogen atoms move across to the oxygen side, releasing energy as they combine to form water. One major advantage of fuel cells is that they create no harmful emissions and are essentially pollutant-free. The only byproducts of their use are water and heat. However, one drawback is that they require a supply of hydrogen as fuel, which can be expensive. Right now, fuel cells are mostly used on the space station and in rockets. As an added benefit, astronauts are able to drink the purified water that is produced when the fuel cells generate power.
- How to Make a Potato Battery: Learn more about how batteries work by building your own battery from a potato.
- Different Types of Batteries and Their Applications: Read about the pros and cons of various battery types and their specifications.
- Future of Batteries: Winner Takes All? Find out more about the state of the battery market and its future.