Trace Contaminant Induced Lattice Strain and Phase Instability in Recycled High-Nickel Cathodes
Trace impurities in recycled high-nickel cathodes induce lattice strain and microcracking, accelerating capacity fade and raising landed cost per cycle.
Rock-Salt Fm-3m
Meaning
Crystalline phases defined by the Fm-3m space group represent a disordered arrangement where lithium and transition metal ions occupy the same lattice sites. The formation of rock-salt fm-3m structures is typically a sign of severe degradation on the surface of cathode particles. This inactive layer prevents the efficient movement of ions and leads to a rapid loss of capacity.
Phase Transformation
Exposure to high temperatures or aggressive cycling triggers the collapse of the layered structure into this cubic form. The rock-salt fm-3m phase is thermodynamically stable but electrochemically inert. Once this transition occurs, the affected material no longer contributes to the energy storage of the cell.
Ionic Impedance
Disordered layers lack the clear channels found in healthy cathode crystals. As the thickness of the rock-salt fm-3m layer increases, the resistance to ion diffusion rises significantly. This blockage forces the battery to work harder to deliver the same amount of power, generating more heat.
Structural Limit
Engineers use surface treatments to delay the onset of this structural decay. Preventing the growth of rock-salt fm-3m is a primary goal when designing batteries for long life applications. This limit on structural stability defines the maximum voltage that a cathode can safely reach.