Lithium ion, or lithium iron?

Someone asked me recently: "what's the difference?" Here's a simple explanation.

Every battery in our driveway and garage is lithium ion. Most are also lithium iron.

Let's start with "ion". An ion is just an atom that's missing an electron, so it's left with a positive charge.

Inside a battery cell are two plates, the anode and cathode, separated by the electrolyte liquid. At the anode, the battery pulls the electron(s) off the lithium atom, leaving a positively charged ion behind. The electron takes the long way round — out through a wire, where we put it to work spinning a motor or boiling the kettle. That stream of electrons through the wire is the current. The ion, meanwhile, moves from the anode through the electrolyte to the cathode, where it recombines with the electron.

The plates are where a battery gets its name:

• The anode is almost always graphite — plain carbon.
• The cathode is the part that varies. In an LFP battery it's iron phosphate (Li-Fe-PO). In an NMC battery it's nickel, manganese and cobalt (Ni-Mn-Co).

LFP wins on safety, lifespan and supply chain ethics — more charge cycles, no cobalt, and you can happily charge it to 100% every day.

NMC wins on energy density — lighter for the same range — and it charges faster, especially in the cold.

Our standard-range Model Y uses LFP, while the Long Range cars tend to use NMC. It's the same story on the wall: our newer Powerwall 3 batteries are LFP, our older Powerwall 2 is nickel-based. We've got both chemistries living under one roof.