Analyze the impact of electrode thermal stability on the safety of lithium-ion batteries

The impact of electrode thermal stability on the safety of lithium-ion batteries The fluid of cathode materials and electrolyte is considered to be an important cause of thermal runaway. Improving the thermal stability of cathode materials is particularly important. The development of anode materials in the industry also pays more attention, in addition to The reason for its higher price and greater profit, the important position of battery safety and an important reason for concern. Like the cathode material, the essential characteristics of the anode material determine its safety characteristics. LiFePO4 is a polyanionic structure, oxygen atoms are very stable, not easy to be released by heat, and will not cause violent reaction or burning of the electrolyte. Other transition metal oxide cathode materials tend to release oxygen when heated or overcharged, and their safety is poor. Among the transition metal oxides, LiMn2O4 exists in the charged state in the form of -MnO2. Due to its good thermal stability, this cathode material is also relatively safe. In addition, the thermal stability of the cathode material can be improved through bulk doping and surface treatment. Generally speaking, the thermal stability of the negative electrode material depends on the structure of the material and the activity of the charged negative electrode. Regarding carbon materials, spherical carbon materials such as mesophase carbon microspheres (MCMB) have a lower specific surface area and a higher charge-discharge platform than flake graphite, so their charged state activity is less, thermal stability is better, and safety is high. Compared with flake graphite, spinel Li4Ti5O12 has better structural stability and higher charge and discharge platform, so it has better thermal stability and higher safety. Therefore, MCMB or Li4Ti5O12 often replace ordinary graphite as the negative electrode of the power battery, which has higher safety requirements. Generally speaking, in addition to the thermal stability of the negative electrode material, the same material, especially graphite, is more concerned about the thermal stability of the solid electrolyte interface membrane (SEI) at the negative electrode and electrolyte interface, which is generally considered to be thermal runaway The first step. There are two ways to improve the thermal stability of the SEI film: one is to cover the surface of the cathode material, such as an amorphous carbon or metal layer on the graphite surface; the other is to add film-forming additives to the electrolyte. During the battery activation process, they form an SEI film with higher stability on the surface of the electrode material, which is conducive to better thermal stability. The safety problem of lithium-ion batteries is directly caused by unsafe electrolyte, but the fundamental reason is the low stability of the battery itself and the appearance of thermal runaway. In addition to the thermal stability of the electrolyte, the thermal stability of the electrode material is one of the most important reasons for thermal runaway. Therefore, improving the thermal stability of the electrode material is an important part of improving the safety of the battery. Its thermal stability, thermal stability should also be related to the electrolyte material including its thermal stability. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: In-depth analysis of lead-acid battery management solutions