Difference between intercalated lithium and metallic lithium (Li-ion batteries) I have a question about Li-ion batteries. I sometimes see the two terms - intercalated lithium and metallic lithium - used when talking about this type of batteries and I was wondering what is the difference between the two? 

I understand that the intercalation means that the Li cations are transferred from one electrode to another and that is why it is called intercalated lithium (or am I wrong?). But what about metallic lithium? What does that mean? 

I found this on Wikipedia:


  Li-ion batteries use an intercalated lithium compound as one electrode material, compared to the metallic lithium used in a non-rechargeable lithium battery


But what makes them different? In other words, what are the differences between intercalated lithium and metallic lithium? Can anyone help me to understand this?
Intercalation is the addition of lithium ions into a host material without significantly changing the host's structure. In my research, I will often prepare test cells where the cathode is an intercalation material, like $\ce{CoO2}$, which can accomodate (or "intercalate") layers of lithium ions between the oxygen layers in the crystal lattice to form $\ce{LiCoO2}$. It's not that there are layers of cathode material surrounding lithium, but rather there's only 1 material, but lithium ions can move into and out of it.

$$ \ce{CoO2 + Li+ + e^- -&gt; LiCoO2} $$

I mostly use lithium metal for the anode because it's easy to work with and has a stable potential, making it a good reference electrode:

$$ \ce{Li^+ + e^- -&gt; Li_{(s)}} $$

In this setup we have an intercalation cathode ($\ce{LiCoO2}$), and a lithium metal anode. The major downside is that when you cycle lithium metal, it forms dendrites which can puncture the separator and short-circuit the cell, leading to catastrophic failure. To solve this problem, commercial cells use graphite anodes, which can intercalate lithium ions:

$$ \ce{C6 + Li+ + e- -&gt; LiC6} $$

This solves the dendrite problem, but makes the battery less efficient. Since dendrite formation is only a problem with repeated cycling, non-rechargeable ("primary") batteries just use lithium metal instead. Lots of researchers have tried to solve "the dendrite problem" for decades, with little success.

The diagram below shows a lithium ion battery with an intercalation cathode on the right: the green parts are lithium, the blue parts are transition metals (Ni, Co, etc.) and the red spheres are oxygen. The anode on the left is the graphite intercalation anode, but you could replace it with a metallic lithium anode.