How to improve the safety of lithium battery packs

For safety reasons, the positive electrode material should have good compatibility and stability with the electrolyte. In the case of overcharge, the analytical reaction of the positive electrode and its reaction with the electrolyte release a lot of heat, causing an explosion. The thermal stability of lithium cobalt oxide and lithium nickel oxide is relatively poor. Because of its high specific capacity and high specific energy density, the lithium nickel cobalt manganese oxide ternary material has become an ideal choice for the current cathode material. In the process of self-assembly and suction filtration, lithium iron phosphate nanoparticles are evenly dispersed in highly conductive and porous hydroxyapatite ultra-long nanowires/Ketjen black nanoparticles/carbon fiber substrates to form a self-supporting, The high temperature resistant lithium iron phosphate cathode material with the magic composite porous structure has excellent thermal stability and fire resistance, and can maintain its electrochemical activity and structural integrity even at a high temperature of 1000 ℃. 2. Anode material The thermal stability of the anode material is related to the type of anode material, the size of the material particles, and the stability of the SEI film formed by the anode. If the large and small particles are made into a negative electrode according to a certain ratio, the contact area between the large particles can be reached, the electrode impedance can be reduced, the electrode capacity can be increased, and the possibility of the precipitation of active metal lithium can be reduced. The quality of SEI film formation directly affects the charge and discharge performance and safety of lithium battery packs, weakly oxidizing the surface of carbon materials, or carbon materials that have been reduced, doped, or surface modified, and the use of spherical or fibrous carbon materials helps The quality of SEI film is improved. The method to deal with the safety of carbon anode materials is to reduce the specific surface area of u200bu200bthe anode material and improve the thermal stability of the SEI film. 3. Diaphragm lithium battery people have recently successfully developed a new type of hydroxyapatite ultra-long nanowire-based high temperature resistant lithium battery diaphragm. In addition to high flexibility, good mechanical strength, high porosity, electrolyte wetting and In addition to the characteristics of excellent adsorption performance, it is more important to have high thermal stability, high temperature resistance, flame retardancy and fire resistance, and its structural integrity can still be maintained at a high temperature of 700 ℃. Batteries assembled with hydroxyapatite ultra-long nanowire-based high-temperature battery separators can maintain normal working conditions in a high temperature environment of 150°C and light up small bulbs, while batteries assembled with PP separators can quickly reach 150°C. When a short circuit occurs, the operating temperature and safety of the lithium battery pack can be effectively improved. 4. Electrolyte The electrolyte of lithium battery packs is basically an organic carbonate material, which is a kind of flammable material. Commonly used electrolyte salt lithium hexafluorophosphate (LiPF6) has an exothermic reaction of thermal analysis. Therefore, improving the safety of electrolyte is crucial to the safety control of power lithium batteries. Using high-concentration NaN(SO2F)2 or LiN(SO2F)2 as the lithium salt, adding the common flame retardant trimethyl phosphate TMP, the prepared electrolyte can significantly improve the thermal stability of lithium batteries, and the addition of flame retardants There is no impact on the cycle performance of the lithium battery pack. In view of the impact that power lithium-ion batteries may face in use, many people try to guard against the internal short-circuit of lithium batteries caused by external forces at the root. They have designed an electrolyte with shear thickening characteristics, which uses non-Newtonian electrolytes. The characteristics of the fluid. Under normal conditions, the electrolyte is in a liquid state. After a sudden impact, it will assume a solid state and become extremely strong. It can even achieve the effect of bulletproof, thus preventing the power lithium battery pack from the root. In the event of a collision, there is a risk of thermal runaway caused by a short circuit in the battery. 5. Conductive agent and binder The type and quantity of conductive agent and binder also affect the thermal stability of the battery. The binder and lithium react with a large amount of heat at high temperatures, and different binders generate different amounts of heat. PVDF The calorific value of fluorine-free binder is almost twice that of fluorine-free binder, replacing PVDF with fluorine-free binder can improve the thermal stability of the battery. Thermal runaway of lithium battery seriously threatens the safety of users’ lives and property. Improving the safety of lithium batteries and guarding against thermal runaway must not only make changes in battery materials, but also combine battery formula design, structural design and lithium battery packs. Multi-pronged thermal management design to jointly improve the thermal stability of the lithium battery pack and reduce the possibility of thermal runaway. With the continuous promotion of lithium battery packs, the safety of lithium batteries has attracted more and more attention. Due to the technical reasons or improper use of the battery itself, the lithium battery may explode and cause safety accidents such as fires. Especially in recent years, the demand for batteries in the electric vehicle market, which is dominated by electric vehicles, has continued to increase. In the process of developing high-power lithium battery systems, battery safety issues have attracted widespread attention, and existing problems urgently need to be further addressed. 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