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Sunday, January 24, 2021

A Look at What Makes us Run: Batteries

Battery Day.  What they are and where they are going.    In some ways such a primitive thing, but still very essential to make things work and be portable.  .  

A closer look at the technology that makes portable electronics possible

By Jessie Frazelle  in Queue ACM.

Tesla held its first Battery Day on September 22, 2020 [tesla.com]. What a fantastic world we live in that we can witness the first Apple-like keynote for batteries. Batteries are a part of everyday life; without them, the world would be a much different place. Your cellphone, flashlight, tablet, laptops, drones, cars, and other devices would not be portable and operational without batteries.

At the heart of it, batteries store chemical energy and convert it into electrical energy. The chemical reaction in a battery involves the flow of electrons from one electrode to another. When a battery is discharging, electrons flow from the anode, or negative electrode, to the cathode, or positive electrode. This flow of electrons provides an electric current that can be used to power devices. Electrons have a negative charge; therefore, as the flow of negative electrons moves from one electrode to another, an electrolyte is used to balance the charge by being the route for charge-balancing positive ions to flow.

Let's break this down a bit and uncover the chemical reactions at play within batteries. An electrical current requires a flow of electrons. Where do those electrons come from?

Electrons in the anode are produced by a chemical reaction between the anode and the electrolyte. Simultaneously, another chemical reaction occurs in the cathode, enabling it to accept electrons. These chemical reactions create the flow of electrons, resulting in an electric current.

A chemical reaction that involves the exchange of electrons is known as a reduction-oxidation reaction, or redox reaction.

Reduction refers to a gain of electrons. Thus, half of this reaction—the reduction—occurs at the cathode because it gains electrons. Oxidation refers to a loss of electrons. Therefore, the other half of this reaction—oxidation—occurs at the anode because it loses electrons to the cathode. Each of these reactions has a particular electric potential. An electrochemical cell can be made up of any two conducting materials that have reactions with different standard potentials, since the more robust material, which makes up the cathode, will gain electrons from the weaker material, which makes up the anode.

Batteries can be made up of one or more electrochemical cells, each cell consisting of one anode, one cathode, and an electrolyte, as described earlier. The electrodes and electrolyte are generally made up of different types of metals or other chemical compounds. Different materials for the electrodes and electrolyte produce different chemical reactions that affect how the battery works, how much energy it can store, and its voltage.  .. " 

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