What factors affect the cycle life of lithium-ion battery packs?
What factors affect the cycle life of lithium-ion battery packs? In recent years, lithium-ion batteries have become a new type of battery with large-scale extensibility. However, after multiple charge-discharge cycles, battery capacity and other functions will decrease. Under the same conditions, the faster the battery capacity decays, the worse the battery quality. The cycle performance of a lithium-ion battery pack is an important indicator of its quality.
The charge-discharge cycle of a lithium-ion battery pack is a complex physical and chemical reaction process. The following analysis examines the factors influencing the cycle life of lithium-ion battery packs using Haobo Battery technology.
1. Planning and Production Process
In battery planning, data selection is the most crucial factor. Different data have different functional characteristics, leading to variations in battery performance. Good matching of positive and negative data results in better cycle performance and a longer battery cycle life. Generally, during planning and assembly, the capacity of the negative electrode is required to be greater than that of the positive electrode. Otherwise, lithium will precipitate on the negative electrode during charging, forming lithium dendrites, which can compromise safety. If the ratio of the negative electrode to the positive electrode is too high, excessive delta emission may occur in the positive electrode, leading to structural collapse.
The type and amount of electrolyte injected also affect battery life. The key manufacturing processes for lithium-ion battery packaging include: positive and negative electrode material preparation, coating, film formation, winding, casing, electrolyte injection, and sealing. Each step in the battery production process is extremely rigorous. Any improper handling can affect the battery's lifespan.
2. Lithium-ion battery data degrades with age.
The charge-discharge cycle of a lithium-ion battery is the process by which lithium ions separate and move back and forth between the positive and negative electrodes through the electrolyte. During the cycle, in addition to the redox reactions at the positive and negative electrodes, many side reactions occur. If the secondary response of the lithium-ion battery can be reduced to a low level, ensuring that lithium ions can consistently and successfully move back and forth between the positive and negative electrodes through the electrolyte, the cycle life of the lithium-ion battery can be extended.
The properties of the positive and negative current collectors also affect the battery's capacity and cycle life. The current collectors for the positive and negative electrodes of lithium-ion battery packs are aluminum and copper, respectively. Passivation films, poor adhesion, localized corrosion (pitting), and overall corrosion formed after current collector corrosion increase the battery's internal resistance, leading to capacity loss and reduced discharge power. Pretreatment methods such as acid-base corrosion and conductive coatings can improve the adhesion and corrosion resistance of the materials.
3. Charge and discharge standards during the cyclic process
The use of a lithium-ion battery pack involves a charge-discharge cycle. The magnitude of the charge/discharge current, the selection of the charge/discharge cutoff voltage, and the charge/discharge method are all crucial factors affecting the cycle life of a lithium-ion battery. Unnecessarily increasing the battery's operating current, adding new charging cutoff voltages, or adding new drop discharge cutoff voltages will all degrade the performance of the lithium-ion battery pack.
The charge/discharge cutoff voltages of lithium-ion batteries differ across different electrochemical systems. Overcharging occurs when the charging cutoff voltage is exceeded during the charging process. When a lithium-ion battery is overcharged, excess lithium ions released from the positive electrode will deposit or embed into the negative electrode. The deposited active lithium readily reacts with the solvent, releasing heat and raising the battery temperature. Over-discharging occurs when the discharge voltage of a lithium-ion battery falls below the discharge cutoff voltage.
During over-discharge, lithium ions are excessively released from the negative electrode, making it difficult for them to be re-intercalated into the battery for the next charge. In future over-discharge cycles, the discharge capacity and charge/discharge power of the lithium-ion battery will decrease significantly. Furthermore, lithium-ion batteries may melt under high current conditions, potentially damaging device components.
