High temperatures affect lithium-ion batteries; is high temperature the cause of lithium-ion battery bulging? Lithium-ion batteries have advantages such as high operating voltage, low self-discharge, no memory effect, and no pollution. Lithium iron phosphate batteries are favored in the new energy industry and are widely used in power lithium-ion batteries and energy storage. However, the speed of their promotion and the breadth and depth of their application are not as satisfactory as expected. Besides factors such as price and batch consistency issues caused by battery materials themselves, their temperature performance is also a crucial factor hindering their rapid promotion.
High temperature effect on lithium-ion batteries
Of all environmental factors, temperature has the greatest impact on battery charge and discharge performance. Electrochemical reactions at the electrode/electrolyte interface are related to ambient temperature; as temperature rises, the output power of the lithium-ion battery increases. Temperature also affects the electrolyte transport rate; higher temperatures accelerate transport, while lower temperatures slow it down, thus impacting battery charge and discharge performance. However, temperatures exceeding 45°C can disrupt the chemical balance within the battery, leading to side reactions.
Temperature directly affects discharge performance, impacting discharge capacity and voltage. Lower temperatures increase internal resistance, slow electrochemical reactions, and rapidly increase polarization resistance, leading to a decrease in discharge capacity and plateau, thus affecting power and energy output. Lithium-ion battery capacity degradation is influenced by battery polarization, where lithium-ion diffusion cannot keep pace with electron transfer, resulting in fewer lithium-ions being held at the positive electrode. This polarization process is further intensified at high temperatures (60°C), becoming the fundamental cause of lithium-ion battery capacity decay.
The high-temperature failure mechanism of lithium-ion batteries is far more complex than previously reported, and it is difficult to distinguish between the loss of active lithium and the loss of active materials in actual research. During the lithium intercalation process of lithium iron phosphate materials, some lithium-intercalated lithium iron phosphate phases are isolated from the electronic conductivity channels formed by the conductive agent due to internal stress, resulting in irreversible deintercalation and deintercalation and causing loss of active materials.
Is high temperature the cause of lithium-ion battery swelling?
1. The main reason for lithium-ion battery swelling is the presence of gas inside the lithium-ion cell. Almost all lithium-ion cells show signs of damage as the first sign of gas buildup inside the cell. In contrast, vacuum-packed polymer cells exhibit swelling. Therefore, cell swelling is also an early warning sign of cell damage or potential safety issues.
2. Battery cells are affected by high temperatures. If battery cells are stored at high temperatures for a long time, the temperature will accelerate some chemical reactions inside the battery cell to form gas. This effect is more pronounced when the battery cell is fully charged or slightly overcharged. Therefore, long-term storage of battery cells at high temperatures should be avoided.
3. Overcharging causes all the lithium atoms in the positive electrode material to migrate into the negative electrode material, leading to the deformation and collapse of the originally full grid in the positive electrode. This is a major reason for the decrease in the capacity of lithium-ion batteries. During this process, the number of lithium ions in the negative electrode increases, and excessive accumulation causes lithium atoms to grow into stumps and crystals, resulting in battery swelling.
4. The SEI film protects the negative electrode material, preventing structural collapse and extending the cycle life of the electrode. However, the SEI film is not static; it undergoes slight changes during charge and discharge, primarily reversible changes in some organic components. Over-discharge of the battery causes reversible damage to the SEI film. The destruction of the SEI protecting the negative electrode material leads to its collapse, resulting in bulging.
The chemical and electrochemical reactions of lithium-ion batteries at high temperatures are extremely complex. Studying the reaction mechanisms between the internal components of the battery, suppressing various exothermic reactions, and improving battery safety under abuse conditions are crucial. Lithium-ion batteries are greatly affected by temperature. In applications such as power lithium-ion batteries and environments heavily influenced by temperature, thermal management is essential to improve battery efficiency and extend battery system lifespan.
