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[[File:Rechargeable AAA 1.2V, 600mAh, Nickel Metal Hydride Battery.jpg|300px|thumb|framed|Figure 1. A rechargeable [[battery]] can function as both a galvanic cell and an electrolytic cell.<ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:BaByliss_for_Men_T47_-_battery_BYD_Rechargeable_AAA-92292.jpg</ref>]]

<onlyinclude>An '''electrochemical cell''' is an apparatus that is used to generate electricity from a spontaneous [[redox reaction|oxidation-reduction reaction]], or that uses electricity to drive a nonspontaneous reaction.</onlyinclude><ref name=libre2>"Electrochemical Cells," Chemistry LibreTexts, 2020. Online. Available: https://chem.libretexts.org/@go/page/41636.</ref> An electrochemical cell is called such because it utilizes the principles of [[electrochemistry]] and is the smallest functional unit of an electrochemical system (a cell). Electrochemistry is the study of electricity and how it relates to chemical reactions. In electrochemistry, electricity can be generated by movements of electrons from one element to another in a reaction known as redox or oxidation-reduction reaction.<ref name=libre1>"Electrochemistry," Chemistry LibreTexts, 2020. Online. Available: https://chem.libretexts.org/@go/page/250.</ref> In redox reactions, [[electron]]s are transferred from one species to another. If the reaction is [[spontaneous]], [[energy]] is released, which can then be used to do useful [[work]]. If the reaction is [[nonspontaneous]], energy is consumed and work must be put into the system.<ref name=libre1/>

Electrochemical cells are important in society today especially in terms of [[energy storage]]. Electrochemical cells such as [[battery|batteries]] can be used on a large scale to store energy from [[Non-dispatchable source of electricity|intermittent energy sources]] like [[solar power|solar]] and [[wind power|wind]]. They can also be used on a smaller scale to power our phones, laptops and other electrical appliances.

There are two types of electrochemical cells: galvanic cells (also called voltaic cells) and electrolytic cells. Both types contain two [[electrode]]s, one anode and one cathode. [[Oxidation]] occurs at the anode and [[reduction]] occurs at the cathode. The electrodes are connected to each other with an external electrical connection, such as a wire, to allow [[electron]]s to flow from the anode to the cathode. The electrodes are also connected by an [[electrolyte]], an ionic substance or solution that allows [[ion]]s to transfer between the electrodes. This maintains the system’s electrical neutrality.<ref name=libre2/>

[[File:galvanic vs electrolytic cells.jpg|700px|framed|center|Figure 2. There are two types of electrochemical cells: galvanic and electrolytic. Galvanic cells are driven by a spontaneous flow of electrons to produce an electric [[current]]. Electrolytic cells need to have an input of electrical energy in order for electrons to flow.<ref name=libre2/>]]

===Galvanic Cells===
Galvanic cells, also called voltaic cells, are driven by a spontaneous [[chemical reaction]]. This means that [[electron]]s will flow spontaneously from one side of the electrochemical cell to the other. This produces an electric [[current]] through an outside [[circuit]]. The flow of charge is generated by an electrical [[voltage|potential difference]] between two points in the circuit. The cell potential is created when the two different [[metal]]s are connected, and measures the [[energy]] per unit [[charge]] available from the oxidation-reduction reaction.<ref name=rice> ''Chemistry,'' Rice University, 2015. [Online]. Available: https://web.ung.edu/media/Chemistry2/Chemistry-LR.pdf</ref> These cells are the basis for devices like [[battery|batteries]] and [[fuel cell]]s. But they are not the only kind of electrochemical cell.<ref name=libre1/>

===Electrolytic Cells===
In an electrolytic cell, a nonspontaneous chemical reaction takes place. A nonspontaneous reaction means that electrons don't want to move. Thus, an electrolytic cell requires an external source of [[electricity|electrical energy]] to force electrons to flow. Driving the redox reaction in a nonspontaneous direction generates a [[voltage|potential difference]] between the metal electrodes.<ref name=libre2/> In the case of rechargable [[battery|batteries]], they act as galvanic cells when they are discharging electrical energy, but act as an electrolytic cell when they are being recharged.<ref name=libre3>"Electrochemical Cell Conventions," Chemistry LibreTexts, 2021. Online. Available: https://chem.libretexts.org/@go/page/291.</ref>

To learn more about electrochemical cells, please check out [http://hyperphysics.phy-astr.gsu.edu/hbase/Chemical/electrochem.html hyperphysics].

== For Further Reading ==
*[[Electrode]], [[Electrolyte]]
*[[Diode]]
*[[Photovoltaic cell]]
*[[Electric current]]
* Or explore a [[Special:Random| random page!]]

==References==
{{reflist}}
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Electrochemical cell - Revision history

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energy>Jmdonev at 22:34, 19 October 2021