Black mass and white mass: what recycling does with battery graphite

Inside a lithium-ion cell

A lithium-ion cell is a stack of coated foils. The positive electrode is aluminium foil coated with a lithium metal oxide: nickel manganese cobalt oxide (NMC), nickel cobalt aluminium oxide (NCA) or lithium iron phosphate (LFP). The negative electrode is copper foil coated with graphite. Both coatings are held together by a polymer binder, usually PVDF on the cathode, and the cell is filled with an organic electrolyte containing a fluorinated lithium salt, typically LiPF₆. Graphite alone typically accounts for 14 to 20% of the mass of a whole cell, depending on its chemistry (Chernyaev et al., 2024).

From spent cell to black mass

Recycling starts with making the cells safe. They are discharged, then crushed and shredded, often under an inert atmosphere or in a liquid, because damaged cells can release flammable electrolyte. Many plants add a thermal step at a few hundred degrees to evaporate the electrolyte and decompose the binder. Magnets, eddy current separators, air tables and sieves then remove steel, aluminium, copper and plastics.

The fine fraction that passes the last screens, typically below about 100 micrometres, is black mass: the active material of both electrodes, mixed together (Vanderbruggen et al., 2022).

A typical black mass from nickel-based cells contains:

• graphite from the anode, typically 25 to 40% by weight; industrially sourced black mass has been measured at around 40% (Recovery of graphite from industrial black mass, 2025)
• lithium, nickel, cobalt and manganese, mostly as oxides
• copper and aluminium residues from the foils
• fluorine and phosphorus from the binder and electrolyte salt, and some carbon black

Black mass from LFP cells contains iron and phosphate instead of nickel and cobalt and is worth far less to a metal refiner, which is why recyclers usually keep the two apart.

What refining does with it

Black mass is sold to refineries that turn it into battery-grade metal salts. Two families of process dominate (Harper et al., 2019).

Pyrometallurgy smelts the material at around 1,500 °C. Cobalt, nickel, copper and iron collect in a metal alloy that is refined further by leaching, while aluminium, manganese and lithium largely end up in the slag. Graphite does not survive: it burns, serving as a fuel and as a reducing agent for the metal oxides (Cornelio, Zanoletti and Bontempi, 2024).

Hydrometallurgy dissolves the metals, usually in sulfuric acid with a reducing agent such as hydrogen peroxide, and separates them by precipitation and solvent extraction. Graphite is insoluble and ends up in the leach residue, mixed with undissolved oxides, binder and metal salts. Recovering battery-grade graphite from that residue is possible but needs extensive purification (Chernyaev et al., 2024).

Either way, up to two fifths of the black mass is treated as a by-product. That is a waste of a highly processed material: synthetic anode graphite is made by heating coke to well above 2,500 °C in a slow, energy-intensive graphitisation step, natural graphite is purified with acids or at high temperature, and both are shaped and coated before they go into a cell (Asenbauer et al., 2020).

Separating graphite first

Graphite and the cathode oxides behave very differently in water. Graphite is naturally hydrophobic; the metal oxides are hydrophilic. Froth flotation, a separation method used for decades in mineral processing, exploits exactly that difference: air bubbles carry the graphite to the surface while the oxides stay in the slurry.

The obstacle is the binder, which coats both kinds of particle and blurs the difference between them. Research groups have shown that removing the binder first makes separation work well. With a thermally and mechanically pretreated black mass, flotation recovered 94.4% of the graphite in the froth and 89.4% of the metal oxides in the underflow (Vanderbruggen et al., 2022). Another study recovered 85% of the graphite and 80% of the oxides and showed that the process water can be reused (Salces et al., 2022).

Flotation is one route; others combine classification, chemical treatment and purification. What matters for a buyer is the end result: a graphite stream that can be purified back to battery grade, and a metal stream with as little graphite as possible.

White mass

The metal-rich fraction left after graphite removal is called white mass, after its lighter colour.

For a refinery, this changes several things:

• More metal per tonne. With 25 to 40% of the mass removed, every tonne of feed carries correspondingly more lithium, nickel and cobalt.
• Less residue. In leaching, graphite takes up tank volume, has to be filtered off and leaves as a residue that holds back part of the valuable solution. Without it, there is less to filter, wash and dispose of.
• Less reagent per tonne of metal, because there is less inert solid to wet and wash.
• In smelting, less carbon is burned, which reduces direct CO₂ emissions from the furnace, although the process then needs another reductant or energy source.

How much of this a refiner gains depends on its plant. Plants limited by tank volume, filter capacity or residue handling gain the most. Each refiner should test white mass in its own process.

Why it matters now

Since March 2025 the EU classifies black mass as hazardous waste (Commission Delegated Decision (EU) 2025/934). It can no longer be exported from the EU to countries outside the OECD, so more of it has to be treated in Europe. The EU Batteries Regulation requires recyclers to recover at least 50% of the lithium by the end of 2027 and 80% by the end of 2031, and 90% rising to 95% of the cobalt, copper and nickel (Regulation (EU) 2023/1542). Graphite has no recovery target of its own yet, but natural graphite is covered by the regulation's due diligence rules, and both natural and synthetic graphite are strategic raw materials under the Critical Raw Materials Act. See why Europe needs its own graphite.

Where Aeroborn fits

Aeroborn's Battery Recycling and Upgrading platform separates black mass into graphite, which we purify to battery grade at 99.95% carbon, and white mass, which goes to metal recyclers as a graphite-free feed. The platform is patented. What buyers check in recovered graphite is covered in what makes graphite battery grade. Refiners who want to test white mass in their process can contact us.