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There are clearly some differences between the classical galvanic cell and the Li-ion batteries, but if one looks at the schematics, they looks a bit similar. Please see below:

a) The galvanic cell:

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and

b) Li-ion

![enter image description here

So I know that in theory there are two fundamental differences between the galvanic cells and Li-ion batteries:

  1. In LIB, the Li ions intercalate in the structure of the anode and cathode
  2. In LIB, there is solid-state mass diffusion of ions.

This is easy to understand, in theory, but what happens in fact in the galvanic cell? Why isn't there any diffusion? Is it because it is not concentration driven (there are two species instead of one)? But if there is no diffusion, how are they moving? In the galvanic cell, are the ions diffusing on the surface of the electrodes instead of intercalation in the structure?

Can anyone help me to understand better the differences between the two cells?

Thank you!

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2 Answers 2

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In a lithium ion battery, no metallic lithium is present physically. Lithium atoms are "dissolved" in a graphite mass, where they are ionized into lithium ions, which gets taken in between graphene planes. The corresponding electrons are moving in the graphene planes, as graphene conducts electricity. So the initial Lithium electrode is not made of Lithium atoms in graphite. It is made of Li+ cations inserted between graphene planes, which are "filled" with free electrons moving in the graphene network. These electrons repell each other and are ready to move through an outer wire to the cathode, where they can for example neutralize Fe(III) atoms, provided the corresponding lithium cations quit the anode and move to the cathode. This is why the battery is called "Lithium ION battery" (or "Lithium ION cell") and not simply "Lithium battery" (or "Lithium cell").

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in a galvanic cell a metal such as zinc spontaneously loses electrons at the anode which are accepted by the cations in the electrolyte, for example Cu2+. This naturally creates a need for anions at the anode and cations at the cathode, hence the need for a salt bridge. In a lithium ion battery lithium (really the equivalent of lithium, as in "lithiated graphite") loses an electron and travels to the anode, and in this case the cation at the cathode that accepts the electronn (lets assume a lithium iron phosphate or LFP battery) is iron(III)phosphate, converting it to iron (II)phosphate with a -1 charge. The charge imbalance still is there, but is alleviated by having the lithium ion itself migrate to the cathode. There is no need to send anions to the anode because its gone! During recharging the opposite occurs: electrons migrate back to the anode, and the same lithium ions migrate back to the anode as well, reforming our lithiated graphite.

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  • $\begingroup$ the Zn/Cu cell - as a frequent school example - is one of many possible arrangements of galvanic cells, similarly as Li ion cells. $\endgroup$
    – Poutnik
    Commented Apr 15 at 18:06

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