Many people, including those involved in energy storage technology, photovoltaic power generation, and home energy storage, have noticed a sharp drop in the range of electric vehicles and a decrease in the capacity of energy storage batteries after prolonged use. Occasionally, problems such as bulging and overheating may occur, which are often simply attributed to "battery aging." However, the core cause of most premature aging and safety hazards in lithium batteries is lithium plating.
Normal lithium battery charging is a stable and reversible electrochemical process: lithium ions are extracted from the positive electrode, migrate through the electrolyte and separator to the negative electrode, and are stably embedded in the layered structure of the graphite negative electrode. During discharge, they are extracted in the reverse direction to complete the energy cycle. The graphite negative electrode has a fixed lithium intercalation potential range. If the operating conditions are abnormal, the cell parameters are unbalanced, and the negative electrode's carrying capacity is insufficient, lithium ions that cannot be intercalated in time will precipitate on the electrode surface, reducing to metallic lithium—this is lithium plating. Lithium deposition mainly falls into three categories: dead lithium, deposited lithium, and lithium dendrites. Needle-shaped lithium dendrites are the most dangerous, easily piercing the separator, causing micro-short circuits, self-discharge, and in severe cases, directly leading to battery thermal runaway.
I. Daily Operating Conditions: The Main Cause of Lithium Deposition
Improper operation during daily use is the core factor contributing to high lithium deposition rates, mainly falling into three categories. First, prolonged high-power fast charging. Fast charging essentially involves a large current input, causing a massive number of lithium ions to rapidly escape from the positive electrode in a short time. However, the ion diffusion rate of the graphite negative electrode is limited, unable to absorb all lithium ions in time; excess ions accumulate on the negative electrode surface, depositing metallic lithium. Industry tests show that slow charging below 1C at room temperature carries virtually no risk of lithium deposition, 1.5C fast charging results in slight lithium deposition, and 2C and above overcharging leads to large-area lithium deposition at the electrode edges. Prolonged high-frequency fast charging significantly accelerates battery aging.
Second, charging in low-temperature environments. This is also the core reason why automakers limit current in low-temperature environments and lock fast charging via BMS. At low temperatures, electrolyte viscosity increases, significantly reducing lithium-ion migration efficiency. Simultaneously, graphite lattice shrinkage drastically increases the difficulty of lithium intercalation. Especially when forced into high-power charging below 0°C, lithium ions accumulate on the negative electrode surface, rapidly forming lithium dendrites. Data shows that at -10°C, charging with the same current results in ten times more lithium deposition than at room temperature, a key reason for faster battery degradation in northern winters.
Finally, overcharging and improper use of older batteries also contribute. Abnormal BMS protection and excessive charging voltage can cause overcharging. At a full charge, the negative electrode's lithium intercalation space is completely saturated, forcing excess lithium ions to deposit. Older batteries with higher cycle counts have graphite particle pulverization and a thickened SEI film, already reducing the effective lithium intercalation space. Using the same charging parameters as new batteries is equivalent to overcharging, continuously inducing lithium deposition.
II. Manufacturing Process: Hidden Dangers Inherent in Battery Manufacturing
Besides issues arising from usage, some batteries inherently possess lithium plating risks upon leaving the factory. If the negative electrode active material ratio is insufficient or the N/P ratio is low during production, the lithium ions extracted from the positive electrode will exceed the negative electrode's carrying capacity, leading to continuous lithium plating during charging. Simultaneously, process defects such as uneven electrode coating, excessive rolling, insufficient positive and negative electrode coverage, and poor electrolyte wetting can all cause localized blockage of lithium intercalation channels, resulting in fixed-point lithium plating defects, affecting the overall battery life and safety.
III. Irreversible Hazards of Lithium Plating and Practical Mitigation Methods
The damage caused by lithium plating is completely irreversible and cannot be repaired or restored by charging. Some of the deposited metallic lithium becomes "dead lithium," permanently depleting the cell's active lithium source and causing continuous capacity decay. The remaining lithium will react with the electrolyte, increasing the battery's internal resistance, leading to overheating and accelerated self-discharge. Furthermore, the continuous growth of lithium dendrites can directly puncture the separator, causing bulging, short circuits, and even fires and explosions.
To reduce lithium plating damage, avoid high-power charging at low temperatures during daily use. In winter, prioritize preheating the battery before charging with a small current, and reduce high-frequency overcharging. For older batteries, appropriately reduce the charging rate and full-charge limit. In industry operations and maintenance, it is necessary to strictly control the cell manufacturing process and composition, optimize BMS charging strategies, and automatically reduce current in the high SOC range to reduce polarization risks.
Lithium plating occurs throughout the entire life cycle of lithium batteries and is a core pain point for battery safety and lifespan. Understanding the causes of lithium plating and standardizing usage and maintenance methods are essential to effectively slow down battery degradation and avoid safety risks at the source.
