Meaning
Physical process involving the creation of sub micron cavities within a material during manufacturing or cycling. The occurrence of micro-void formation leads to a loss of contact between active materials and the current collector or electrolyte. These tiny gaps increase the internal resistance of the cell and limit the available power.
Stress Accumulation
Volumetric changes during the insertion and removal of ions create internal mechanical tension. As the lattice expands, micro-void formation begins at the interfaces where the strain exceeds the bonding strength of the components. This process is particularly prevalent in silicon based anodes which experience massive swelling.
Capacity Fade
Disconnected regions of the electrode no longer contribute to the storage of energy. Because micro-void formation isolates particles from the conductive network, the total usable capacity of the battery decreases over time. Preventing this separation involves using elastic binders that accommodate the moving boundaries of the active material.
If the micro-void formation is left unchecked, the conductive paths become so tortuous that the battery cannot deliver the high currents needed for acceleration. Over many cycles, the accumulation of these voids leads to a complete loss of electrical contact and the death of the cell. Careful material selection is the only way to mitigate this structural decay.
Processing Condition
Slurry composition and drying rates influence the initial porosity of the electrode layer. If the solvent evaporates too quickly, micro-void formation occurs as the solid components settle unevenly. Optimizing the thermal profile during the coating process ensures a dense and uniform structure that resists mechanical failure.
