Why a drained battery still is not safe to shred
Electric car batteries are built from small units called cells, wired into groups called modules inside 1 pack. A cell runs between about 2.5 and 4 volts, and recyclers count 2.5 volts as fully drained, called 0% state of charge. A university thesis found that even then, enough charge remains between the 2 electrodes of a cell, the anode and the cathode, that letting them touch during crushing can spark a fire or start thermal runaway, an uncontrolled heating reaction inside the cell. A full pack carries between 200 and 800 volts, above the 60 volts that marks equipment as high voltage under safety rules. The thesis found thermal runaway can start at 90 degrees Celsius and climb past 800 degrees Celsius, hot enough to force open neighboring cells and spread through the whole pack.
Taking the pack apart before the shredder
United States rules, enforced by the Environmental Protection Agency, let a handler take a pack down to its modules or individual cells without opening a cell casing, and count that as disassembly rather than damage. A handler may not breach a cell casing at all, except to remove leftover electrolyte, then must reseal it. Shredding itself is only allowed at a destination facility built for the job, never at a general handler. A university thesis lists what comes off a pack during disassembly, the aluminum casing, a circuit board, copper wiring and current collectors, the metal foils inside a cell, plus cabling and plastics.
What the shredder leaves behind, and what falls through
Only the modules or cells go into the shredder, and what comes out is not 1 material. A peer reviewed study describes a separation step right after shredding, sorted by size, that pulls out the coarse fraction, aluminum and copper current collector foils plus metal casings, and sets it aside. What falls through as fine powder is black mass, named for the dark color the graphite from the anode takes on when mixed with metallic particles from the cathode. Aqua Metals, a battery recycling company, estimates black mass makes up 40% to 50% of the total weight of an electric vehicle battery, with the rest split between binder, copper, electrolyte, plastics, aluminum and steel.
1 peer reviewed study measured a real 10 gram sample of black mass and found 28% was anode material, mostly graphite, and 57% was cathode material, a nickel manganese cobalt oxide. The remaining 15% comes from arithmetic done for this article against the 85% total recovery the study states, not a figure the study prints itself.
This is 1 measured 10 gram sample of black mass from 1 peer reviewed study, not a fixed recipe every batch matches. The 15% not recovered as either is arithmetic done for this article against the 85% total recovery the study states, not a number the study prints as 1 line itself.
Show the numbers
| Anode material | 28 |
| Cathode material | 57 |
| Not recovered as either | 15 |
The metals inside black mass are not the same twice
Black mass is not 1 fixed recipe. Aqua Metals gives a general range for the metals commonly found inside it, shown below. A separate peer reviewed study measured 3 industrial samples for their dominant metal instead of a general range, and they came back nickel rich, manganese rich at 30.1%, and cobalt rich at 34.1%. The 2 studies measured different things, a range against 3 samples each chosen for being rich in 1 metal, so neither contradicts the other. Both agree that black mass from 1 recycled pack differs from another, even before the chemical process that comes next to pull the metals out.
This is a general estimate from 1 company for metal shares across black mass generally, not a measurement of 1 sample. The remainder of black mass is graphite plus metal flakes, not covered by this chart.
Show the numbers
| Cobalt | 5% to 20% |
| Nickel | 5% to 15% |
| Manganese | 2% to 10% |
| Copper | 3% to 10% |
| Lithium compounds | 2% to 6% |
| Aluminum | 1% to 5% |
| Iron | 1% to 5% |