Understanding the Loss of Active Lithium in Batteries
In the long-term use of lithium batteries, capacity loss is an inevitable phenomenon. In standard battery failure analysis, capacity loss is categorized as either reversible or irreversible. active lithium analysis is crucial for understanding these changes.
What is Active Lithium?
Active lithium refers to the lithium ions that participate in the charging and discharging processes within a battery. Not all lithium ions on electrode materials are active; only those involved in these processes are considered active lithium. The active lithium analysis helps in understanding the charging capacity at low rates when the battery is in a fresh state.
Quantifying the Loss of Active Lithium
For accurate active lithium analysis, it is crucial to comprehend the changes between fresh and aged active lithium. In a fully discharged, freshly disassembled battery, charging cycles are executed to create electrode potential maps. The active lithium analysis involves normalizing these curves, as demonstrated in the figure below. The starting point of the negative electrode is positioned at 0, with the positive electrode curve adjusted accordingly.
Calculating Active Lithium Loss
The essence of active lithium analysis is determining the starting potential of the positive electrode in the lithium insertion state, both pre and post-aging. This potential indicates the battery's completely emptied state. The difference in lithium quantity removed when charged to the same cut-off potential denotes the active lithium loss. For active material loss, active lithium analysis involves evaluating the disparity in the charging and discharging capacities per unit area of the electrodes.
Minimizing Reversible Decay Influence
In active lithium analysis, minimizing the effects of reversible decay is essential. This is achieved by conducting electrode charging and discharging at the lowest possible rate conditions.
Active lithium analysis provides comprehensive insights into battery health, distinguishing between reversible and irreversible changes. Understanding these processes is key for battery optimization and prolongation of their lifecycle.