Although the term “battery” was not used until Benjamin Franklin’s experiments in 1749, what are now called “Baghdad batteries” were first used in Mesopotamia around 200 BC. They consisted of a jar containing a copper-covered iron rod and an acidic agent such as vinegar. Their exact purpose is not known, but may have been religious or medicinal in nature.
The first modern battery, now known as a voltaic pile, was invented in 1799. This battery consisted of alternating layers of copper and zinc separated by brine-soaked cloth or paper. It was further refined in 1836 as the Daniell cell, which featured a glass jar containing a copper disc, a copper sulfate solution, a zinc disc, and a zinc sulfate solution. The Daniell cell worked well enough that it was used to power telephones and doorbells before electricity was commonplace.
Commercially produced batteries entered the market in 1898, manufactured by the National Carbon Company. That company eventually became the Eveready Battery Company, which is still in existence today. Battery technology continues to evolve, and more exciting breakthroughs are on the horizon.
All batteries have two terminals, a positive and a negative. Inside the battery case, an anode is connected to the negative terminal and a cathode is connected to the positive terminal. A separator sits between the two to prevent them from touching, and an electrolyte allows electrical charge to flow between them. A collector conducts the charge to the outside of the battery and through the “load,” which is whatever the battery is powering.
A series of chemical reactions occur inside the battery when the load completes the circuit: oxidation in the anode releases electrons, while reduction in the cathode absorbs those electrons. Which chemicals are involved depends on the type of battery:
- Cheap dry cell batteries: Low-end AAA, AA, C, and D batteries are often zinc-carbon. The anode is made of zinc, while the cathode is made of magnesium dioxide. The electrolyte solution may be zinc chloride or ammonium chloride.
- Higher-end dry cell batteries: More expensive AA, C, and D batteries are generally known as alkaline batteries because the electrolyte solution is alkaline in nature (pH greater than 7). The anode is made of zinc powder, the cathode of magnesium dioxide, and the electrolyte solution of potassium hydroxide. These batteries have a higher capacity than zinc-carbon batteries as well as a longer shelf life. They are also less likely to leak.
- Rechargeable lead-acid batteries: Rechargeable lead-acid batteries have an anode made of lead and a cathode made of lead dioxide. The electrolyte solution consists of diluted sulfuric acid. As the first commercially viable rechargeable batteries, lead-acid batteries are used in a variety of applications, including cars, RVs, powered wheelchairs, and even solar power storage. Increasingly, though, they are being replaced by rechargeable lithium-ion batteries due to those batteries’ superior properties.
- Rechargeable lithium-ion batteries: The anode of a lithium-ion battery is made of carbon (typically, though not always, graphite) and the cathode is made of lithium oxide. The electrolyte solution is lithium salt in an organic solvent. Lithium-ion batteries are the most advanced batteries currently in commercial use. They have a significantly higher capacity than lead-acid batteries, are far more efficient, and have a much longer lifespan.
As technology continues to rapidly evolve, batteries need to keep pace. Some of the most promising advancements will be in lithium-ion battery technology. Researchers are experimenting with a variety of compounds that can store more lithium, as well as different types of carbon to optimize the performance of the anode.
Another promising technology is lithium-sulfur battery composition. With sulfur as the cathode and metallic lithium as the anode, these batteries are just now being prototyped, but their theoretical energy density looks to be incredibly high.
Solid-state batteries will replace the electrolyte solution in traditional batteries with a solid, highly conductive electrolyte compound. New, non-flammable, high-capacity polymers could revolutionize safety, weight, and even shelf life. It’s entirely possible that solid-state technology could emerge simultaneously with lithium-sulfur technology, creating an entirely new class of batteries designed for electric vehicles, aerospace, and other heavy-load industries.
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