Dynamic Core Temperature Reconstruction for Transient Swelling Deconvolution in Prismatic Modules
Deconvoluting swelling requires dynamic internal thermal reconstruction to separate reversible expansion from heat driven volume growth.
Lithium Intercalation Strain
Meaning
Structural distortion occurring within the crystal lattice of electrode materials as they host or release lithium ions accompanies the charging and discharging of electrochemical cells. The phenomenon, known as lithium intercalation strain, happens when the changing concentration of lithium modifies the unit cell volume. These dimensional changes are characteristic of most insertion electrodes.
Lattice Expansion
Active materials like graphite and transition metal oxides undergo crystalline phase transitions that alter their physical dimensions. During insertion, the lattice can expand up to ten percent in graphite and over two hundred percent in silicon-based materials, driving lithium intercalation strain. The resulting change in volume generates high tensile and compressive stresses within individual particles.
Mechanical Damage
Cyclic stress from these volumetric changes causes mechanical failure of the active materials. When lithium intercalation strain is high, it leads to particle cracking and electrical isolation of the active material from the carbon black matrix. This mechanical degradation reduces the storage capacity and shortens the operating life of the battery.
It also accelerates the degradation of the electrolyte on the newly exposed crack surfaces.
Electrode Behavior
Compacting pressures applied during module assembly must accommodate these bulk changes in electrode thickness. If the housing is too rigid, lithium intercalation strain generates high pressures that can damage the casing or separator. Engineers must design breathing room within the pack to absorb these dynamic volume changes.