The short version
Nickel sulfide is easy to make battery-grade and running out. Nickel laterite is abundant and was long stuck in stainless steel. High-pressure acid leaching and the nickel-matte conversion route opened laterite to the battery market and reshaped world supply.
Stage by stage
Magmatic sulfide or tropical laterite
Sulfide ore formed where magma separated a metal-rich liquid. Laterite formed where millions of years of rain rotted ultramafic rock at the surface.
Sudbury, Norilsk or Sulawesi laterite
Sulfide is mined underground and floated. Laterite is stripped from shallow soil with excavators.
Smelting or high-pressure acid leach
Sulfide goes to a smelter and becomes matte. Laterite is either smelted to ferronickel or leached in an autoclave at 250 C and 40 bar.
Note: HPAL is capital-intensive and historically difficult to commission.
Nickel sulfate
Matte or mixed hydroxide precipitate is dissolved and crystallised into battery-grade sulfate.
Cathode precursor and active material
Nickel, manganese and cobalt sulfates are co-precipitated into a mixed hydroxide, then lithiated and calcined.
Battery, or stainless steel
Around two-thirds of nickel still goes into stainless steel.
