Meaning
Physical metric quantifying the mass of active material contained within a specific electrode volume after mechanical compression. Achieving a high compaction density is necessary for maximizing the energy density of a battery pack. This value dictates the thickness of the coating on the current collector and influences the final dimensions of the cell.
Volumetric Capacity
Energy storage per unit of space scales directly with the amount of material packed into the electrode. When compaction density increases, the inactive volume occupied by pores decreases. This adjustment allows for more watt-hours to be stored within the fixed external volume of a prismatic or cylindrical housing.
Ion Transport
Pore structure changes as the material is pressed to higher levels of density. Over-compression can lead to a tortuous path for lithium ions, which increases internal resistance during discharge. If compaction density exceeds the limit where electrolyte wetting occurs, the cell will suffer from limited power output.
Particle Integrity
Mechanical stress during the calendering process can cause secondary particles to fracture or deform. Graphite flakes may align in a preferred orientation when compaction density reaches extreme values. Such alignment often leads to anisotropic swelling during lithiation.
Monitoring the physical state of the particles ensures that the electrical contact remains consistent without damaging the active material.
