How lithium-ion cells are made

Lithium ions shuttle between a graphite sheet on copper foil and a metal oxide on aluminum foil.

stations: 10
things upstream: 54
raw sources: 23
steps from the ground: 6

The short version

Cell plants mix cathode and anode slurries, coat them onto aluminum and copper foil, dry the sheets and roll them to a set thickness. Electrodes slit to width are wound or stacked with a separator, welded to terminals and enclosed. A partial vacuum then draws in electrolyte, and the first slow charge builds a protective film inside.

Mix the slurries

Active powders are blended with binders and conductive additives into something like thick paint, with magnetic filters catching stray metal. Cathode and anode batches stay separate.

Goes in
Lithium carbonate Cobalt Nickel Manganese Synthetic graphite
Coat the foils

A slot die lays slurry onto moving foil, metal oxide onto aluminum for the cathode and graphite onto copper for the anode. Width has to be right to within 0.1 mm, and the edges are the hard part.

Goes in
Aluminum Copper
Dry the coating

Convective air dryers run right after coating, and the solvent is recovered. Anode lines add infrared as a booster.
Calender to thickness

Rollers press the sheet to a controlled thickness and porosity, without letting it crack.
Slit and dry again

Electrodes run up to 1.5 m wide until blades cut them to cell width. A burr here could pierce the separator later and cause a short. A second drying removes the last solvent and water.
Wind or stack

For a cylinder, anode, separator and cathode wind into a spiral. Pouch cells stack the layers one by one. Alignment matters, as does avoiding any puncture.

Goes in
Polyethylene
Weld the terminals

Gathered foils are joined to their tabs by laser, spot or ultrasonic welding, with care that no spatter stays in the cell.
Close the can

The roll or stack goes into a can or heat-sealed pouch. A high-voltage test then checks for debris, folds and holes in the separator.

Goes in
Steel
Fill with electrolyte

A partial vacuum pulls a set dose of electrolyte through every layer of the dry cell. Weighing the cell before and after confirms the fill.
Form and age

Each cell gets its first charge under tight control of current and temperature, which builds a microscopic protective layer on the anode. Cells rest for days or weeks while sensors watch for voltage drift, and every one is graded.

End of the lineLithium-ion cell Next it goes into electric car battery, smartphone, laptop and 7 more.

Worth repeating

In the three decades since Li-ion batteries were first sold in 1991, their volumetric energy density tripled and their cost dropped tenfold.
Cells come in three shapes: cylindrical cans, prismatic cases and soft pouches.