Meaning
Gradual shift in the molar ratio of active elements within a battery electrode over time. Observed stoichiometry drift typically results from side reactions that consume lithium or change the structure of the transition metals. This shift alters the electrical potential and the energy capacity of the cell.
Chemical Imbalance
Loss of mobile lithium ions into the passive layers causes a change in the internal chemistry. As the ratio of metals changes, the cell experiences the chemical imbalance of stoichiometry drift. This process is often irreversible and leads to a permanent reduction in performance.
Cycling Effect
Repetitive charging and discharging cycles accelerate the breakdown of the lattice. The mechanical strain of moving ions creates the cycling effect of stoichiometry drift. These defects trap ions and prevent them from participating in the electrochemical reaction.
Energy Density
Decreased storage capacity for a given volume is the direct result of a loss in active material sites. Because the total energy drops significantly, the system shows the energy density of stoichiometry drift. Manufacturers must design systems with an initial overcapacity to account for this expected decline over the life of the product so that the device continues to meet user expectations until the end of its service life.
