In recent years, reports of fires and even explosions caused by lithium-ion batteries are not uncommon. Let’s learn about the thermal stability and overcharge, high temperature and short circuit safety analysis of lithium batteries with Dongguan Yunsheng Electronics:

Lithium-ion batteries are mainly composed of negative electrode material, electrolyte and positive electrode material. When the negative electrode material graphite is in the charged state, the chemical activity is close to that of metallic lithium. The SEI film on the surface decomposes at high temperatures, and the lithium ions embedded in the graphite react with the electrolyte and the binder polyvinylidene fluoride to release a lot of heat.

Alkyl carbonate organic solutions are commonly used as electrolytes, which are flammable. The positive electrode material is usually a transition metal oxide, which has strong oxidizing properties in the charged state, and is easily decomposed to release oxygen at high temperatures. The released oxygen undergoes an oxidation reaction with the electrolyte, and then releases a large amount of heat.

Therefore, from the point of view of materials, lithium-ion batteries have a strong risk, especially in the case of abuse, safety issues are more prominent.

1. Thermal stability analysis of lithium-ion battery materials

The fire hazard of lithium-ion batteries is mainly determined by the amount of heat generated by chemical reactions in various parts of the battery. In the final analysis, the fire hazard of lithium-ion batteries depends on the thermal stability of the battery material, and the thermal stability of the battery material depends on the chemical reaction between its internal parts. At present, people mainly use Differential Scanning Calorimeter (DSC), Thermogravimetric Analyzer (TGA), Adiabatic Accelerating Calorimeter (ARC), etc. to study the thermal stability of battery-related materials.

1 Influencing factors of the thermal stability of anode materials:

The thermal stability of carbon fiber, hard carbon, soft carbon and MCMB four different structure carbon materials was studied by DSC. The study found that the first exothermic peak of the four types of carbon all appeared at 100°C. This exothermic peak is considered to be caused by the decomposition of the SEI film; as the temperature rises to 230°C, the carbon structure and specific surface area are thermally stable to the material The influence of sex is gradually emerging. Carbon electrode materials with graphite structure (carbon fiber, MCMB) generate more heat than carbon electrode materials with amorphous structure (soft carbon, hard carbon). XRD shows that at about 230°C, the total amount of lithium intercalation loss is linearly related to the carbon specific surface area.