At present, the measures to improve the safety of lithium-ion batteries and prevent battery explosions mainly include improving the thermal stability of the battery, improving the overcharge protection ability and improving the ability to prevent the battery from short circuit. This article will provide an overview of the relationship between thermal stability and materials for Li-ion batteries.
The effect of improving the thermal stability of the battery on the material:
① The thermal stability of lithium-ion batteries is closely related to the type, structure and surface morphology of cathode materials. The thermal stability of cathode materials can be improved by optimizing synthesis conditions, improving synthesis methods, and synthesizing materials with good thermal stability; or using composite technology (such as doping technology) and surface coating technology (such as coating technology).
② The thermal stability of the negative electrode material is related to the type of negative electrode material, the size of the material particles and the stability of the SEI film formed by the negative electrode. The quality of SEI film formation directly affects the charge-discharge performance and safety of lithium-ion batteries. According to relevant reports, weakly oxidizing the surface of carbon materials, or reducing, doping, and surface-modifying carbon materials, and using spherical or fibrous carbon materials can help improve the quality of SEI films.
③The stability of the electrolyte is related to the type of lithium salt and solvent. Using lithium salt with good thermal stability and a solvent with a wide potential stability window can improve the thermal stability of the battery. There is also interest in the use of additives to improve the thermal stability of electrolytes. Adding some high boiling point, high flash point and non-flammable solvents to the electrolyte can improve the safety of the battery.
④ The type and quantity of conductive agent and binder also affect the thermal stability of the battery. The study found that replacing acetylene black with nano-stainless steel fiber can reduce the resistance of the electrode, improve the conductivity, and achieve the effect of reducing the heat release during the no-discharge process.
⑤ The reaction between the binder and lithium generates a lot of heat at high temperature. Different binders have different calorific values. The calorific value of PVDF is almost twice that of fluorine-free binders. Replacing PVDF with fluorine-free binders can improve the battery's performance. Thermal stability.
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