Energy storage battery packs, as core components of modern energy systems, face lifespan degradation that directly impacts the reliability and economic viability of energy storage. Frequent charging and discharging trigger multiple physical and chemical changes within the battery pack, leading to irreversible capacity degradation. Targeted measures can effectively slow this process.
Under frequent charging and discharging, the lifespan degradation of energy storage battery packs primarily stems from structural damage to the electrode materials. The positive and negative electrode materials of lithium-ion batteries undergo repeated lithium ion insertion and extraction during charge and discharge. Long-term cycling can cause the layered structure of the graphite negative electrode to collapse or the crystal structure of the positive electrode material to become disordered. This structural damage obstructs lithium ion migration pathways, preventing some lithium ions from participating in reactions and forming "dead lithium," which directly reduces the active material content. Furthermore, repeated charging and discharging can form a solid electrolyte interphase (SEI) on the electrode surface. While this SEI protects the electrode, its continued thickening consumes cyclable lithium ions, exacerbating capacity degradation.
Electrolyte decomposition and side reactions are another key degradation factor. During frequent charging and discharging, the organic solvents and lithium salts in the electrolyte are prone to decomposition under high pressure or high temperature conditions, generating gases and precipitates. These byproducts not only damage the contact interface between the electrode and the electrolyte but also form conductive pathways within the battery, leading to self-discharge or micro-short circuits. Furthermore, overcharging or overcharging can trigger electrolyte oxidation, generating corrosive substances such as fluoride, which further corrode the electrode materials, creating a vicious cycle.
Temperature fluctuations have an amplifying effect on the degradation of energy storage battery packs. Frequent charging and discharging leads to uneven heat generation within the battery. High-temperature areas accelerate electrolyte decomposition and electrode material corrosion, while low-temperature areas increase polarization due to reduced ion migration. This alternating hot and cold environment increases internal stress in the battery, weakens the bonding between the electrode material and the current collector, and may even cause active material shedding. Prolonged exposure to extreme temperatures can shorten the cycle life of a battery pack.
The control capabilities of the battery management system (BMS) directly influence the degradation rate. During frequent charging and discharging, if the BMS cannot accurately monitor the voltage, temperature, and internal resistance of each cell, some cells may overcharge or overdischarge. For example, if individual cells in a battery pack reach their cutoff voltage prematurely due to internal resistance differences, if the BMS fails to adjust its charge and discharge strategy promptly, a chain reaction can occur, accelerating the degradation of the entire pack. Furthermore, inadequate balancing in the BMS can lead to increased capacity differences between cells, creating a "short board effect" and further shortening the battery pack lifespan.
To address these mechanisms, optimizing the charge and discharge schedule is a fundamental measure to mitigate degradation. Avoiding prolonged periods of full charge or over-discharge, and controlling the state of charge (SOC) between 20% and 80%, can significantly reduce stress on electrode materials. Furthermore, adopting a "shallow charge and discharge" strategy, whereby the depth of charge and discharge does not exceed 50% each time, can reduce active material loss. For large-scale applications such as energy storage power stations, power allocation algorithms can prioritize healthy cells for high-frequency charging and discharging, reducing the frequency of use of aging batteries.
Temperature control and heat dissipation design are key technical measures. In frequent charging and discharging scenarios, liquid cooling, air cooling, or phase change materials are necessary to maintain the battery pack operating temperature between 15°C and 35°C. For outdoor energy storage systems, cooling intensity can be adaptively adjusted based on ambient temperature to avoid local overheating. Furthermore, preheating the battery before startup in low-temperature environments is necessary to prevent lithium ion deposition on the negative electrode surface, forming dendrites and thus reducing the risk of short circuits.
Material and process improvements are a long-term solution. Research and development of highly stable electrode materials, such as silicon-carbon composite anodes instead of graphite, can enhance structural fatigue resistance; developing electrolytes with low decomposition voltages can reduce side reactions; and optimizing battery packaging processes to strengthen the bond between the electrode and current collector and prevent active material shedding. Furthermore, upgrades to the BMS algorithm enable big data-based lifespan prediction and health management, enabling proactive identification of degradation trends and adjustment of operating strategies, extending the lifespan of the energy storage battery pack at a systemic level.
