Where is the LITHIUM in NMC Cathode?

This maybe a noob question, but regarding NMC Cathodes, it is said that 33% each of Ni, Mn and Cobalt. So where is the LITHIUM supposed to be if all Ni Mn and Co already make up 100%?




(Reusing my deleted comments:)


$\ce{Ni + Mn + Co}$ do not make 100%, as they are there in form of mixed oxide. Each 33% rather means they are in 1:1:1 ratio. E.g. for purely $\ce{Co}$ cathodes, the composition is $\ce{Li\_xCoO2}$, with 0<x<1. The key is not to make x=0 nor 1, what would lead to irreversible changes.


In fact, it is formally mixed $\ce{Li + Ni + Mn + Co}$ oxide, where $\ce{Ni + Mn + Co + O}$ form an anionic lattice, while Li+ ions are intercalated within it, in variable amounts according to the charge state ( More charge = less Li, as it is moved to the graphite anode)


See also [Wikipedia: Lithium nickel manganese cobalt oxides](https://en.wikipedia.org/wiki/Lithium_nickel_manganese_cobalt_oxides)



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> Lithium nickel manganese cobalt oxides (abbreviated Li-NMC, LNMC, NMC or NCM) are mixed metal oxides of lithium, nickel, manganese and cobalt. They have the general formula $\ce{LiNi\_xMn\_yCo\_zO2}$. The most important representatives have a composition with $x + y + z$ that is near 1, with a small amount of lithium on the transition metal site. In commercial NMC samples, the composition typically has < 5% excess lithium.
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From [neicorporation.com: Lithium Nickel Manganese Cobalt Oxide (NMC) Electrode Sheets](https://www.neicorporation.com/products/batteries/lithium-ion-cathode-materials/#tab-id-8):



> 
> Layered Lithium Nickel Manganese Cobalt Oxide ($\ce{LiNi\_xMn\_yCo\_zO2}$) is a widely used class of cathode material with NMC111 ($\ce{LiNi\_{1/3}Mn\_{1/3}Co\_{1/3}O2}$), also known as NMC333) being the most common representative. However, Ni-rich NMCs (NMC811, 622, 532) are becoming more and more in focus now in current research due to their higher specific capacity and energy. Among these materials, NMC811 ($\ce{LiNi\_{0.8}Mn\_{0.1}Co\_{0.1}O2}$) can deliver a high capacity of ~$\pu{200 mAh/g}$ with an average discharge potential of ~$\pu{3.8 V}$ (vs. $\ce{Li+}$/$\ce{Li}$), making it a promising positive electrode material for high energy density lithium-ion batteries.
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