Meaning
Microstructural defect processes involve the clustering of unoccupied atomic sites into larger voids within a metal electrode. During the stripping of a lithium anode, vacancy condensation occurs when the rate of lithium removal from the surface is faster than the rate at which the remaining atoms can rearrange. This process leads to the formation of microscopic pits that reduce the active surface area of the electrode.
Atomic Diffusion
The movement of vacancies from the interface into the bulk metal depends on the diffusion coefficient of the lithium atoms. If the diffusion is slow, vacancies accumulate at the boundary and eventually merge to create a physical gap between the metal and the solid electrolyte.
Void Nucleation
Voids begin to form at sites where the structural integrity of the metal is lower, such as grain boundaries or impurities. Once a small void nucleates, it acts as a sink for other vacancies, causing it to grow in size and depth during continued discharge.
Contact Maintenance
The loss of contact area caused by the presence of voids increases the local current density and the overall resistance of the battery. This growth in impedance reduces the efficiency of the cell and can lead to thermal issues if the battery is forced to operate at high power levels. Over time, the accumulated damage from multiple cycles makes the battery more susceptible to catastrophic failure during fast charging.
