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The advantage of new energy vehicles is that they are more low-carbon and environmentally friendly than gasoline-fueled vehicles. It uses unconventional vehicle fuels as power sources, such as lithium batteries and hydrogen fuel. Lithium-ion batteries have a wide range of applications, in addition to new energy vehicles, mobile phones, notebook computers, tablet computers, mobile power supplies, electric bicycles, power tools, and so on.
However, the safety of lithium-ion batteries cannot be underestimated. Many accidents have shown that when people are improperly charged or the ambient temperature is too high, it is very easy to cause spontaneous combustion and explosion of lithium-ion batteries, which has become the biggest pain point in the development of lithium-ion batteries.
Although the nature of the lithium battery determines its "flammable and explosive" fate, it is not completely impossible to reduce the risk and safety. With the continuous advancement of battery technology, whether mobile phone companies or new energy vehicle companies, through a reasonable battery management system and thermal management system, the battery can ensure safety without explosion or spontaneous combustion.
1. Improve the safety of electrolyte
There is a high reaction activity between the electrolyte and the positive and negative electrodes, especially at high temperatures. In order to improve the safety of the battery, improving the safety of the electrolyte is one of the more effective methods. The potential safety hazards of electrolyte can be effectively solved by adding functional additives, using new lithium salts and using new solvents.
According to the different functions of additives, they can be divided into the following categories: safety protection additives, film-forming additives, positive electrode protection additives, stabilizing lithium salt additives, lithium precipitation promoting additives, current collector anticorrosive additives, and wettability enhancing additives.
2. Improve the safety of electrode materials
Lithium iron phosphate and ternary composite materials are considered to be low-cost, "excellent safety" cathode materials, and may be popularized in the electric vehicle industry. For the positive electrode material, the common method to improve its safety is coating modification. For example, the surface coating of the positive electrode material with a metal oxide can prevent the direct contact between the positive electrode material and the electrolyte, inhibit the phase change of the positive electrode material, and improve Its structural stability reduces the disorder of cations in the crystal lattice to reduce heat generation by side reactions.
For the negative electrode material, because the surface is often the most prone to thermochemical decomposition and heat generation in the lithium ion battery, improving the thermal stability of the SEI film is a key method to improve the safety of the negative electrode material. Through weak oxidation, metal and metal oxide deposition, polymer or carbon coating, the thermal stability of the negative electrode material can be improved.
3. Improve battery safety protection design
In addition to improving the safety of battery materials, commercial lithium-ion batteries adopt many safety protection measures, such as setting battery safety valves, thermal fuses, connecting components with positive temperature coefficients in series, using thermally sealed diaphragms, loading dedicated protection circuits, and dedicated battery management System, etc., is also a means to enhance security.