Lithium-ion battery safety related studies:Lithium-ion batteries have become a power source of * widely used in electric vehicles. Many years of development has made great improvements in the energy density, service life and stability of the car power lithium-ion battery. However, in recent years, the electric vehicle safety accident related to the powerful lithium-ion battery has been covered with a shadow of the further development of electric vehicles. Developed a new safe and stable car lithium-lithium-donate battery has become a focus of attention. Over the years, Professor A Xinping has been committed to improving the safety of lithium-ion batteries using materials with PTC effects (POSTIVE-TEMPERATURE-COEFFICIENT, positive temperature coefficient).
Professor A Xinping first prepared a PTC effect poly (3-octylthiophene) (P3OT) to form an ultra-thin coating of less than 1 um to form an Al / p3ot / LCO sandwich structure between the Al-collector and LiCoO2 positive material. [1]. Such a positive electrode structure is first ensured that at normal temperature has the same electrochemical properties as the lithium lithium cobalt acid lithium. Then, when the internal temperature of the lithium ion battery increases to 90-100 ¡ã C, a P3OT having a PTC effect occurs is transformed by a conductive state to a high impedance anti-state, thereby remarkably reducing the electrode current and thus closing the battery reaction. Avoid the internal temperature of the battery that is too high in heat loss. The advantage of this method is that it is simple and convenient and can be compatible with the existing battery production process. At the same time, the thermal shutdown effect can also meet the work needs and safety requirements of the actual battery.
Figure 1 Working mechanism of PTC positive under abusive conditions
On the basis of the above work, the AIL team successfully developed a new PTC material poly (3-octylpyrrol) in 2018: poly (styrene sulfonate), and bonded to conductive carbon as lithium Electric conductive frame of ion battery positive material [2]. Since the composite material has a higher electron conductivity and is uniformly dispersed in the active positive electrode material, its room temperature electrochemical properties are not much changed in conventional cobalt acid lithium positive electrode. The significant difference in electrochemical performance is from high temperature conditions. High temperatures in more than 120 ¡ã C can rapidly initiate the PTC transformation of the material, so the actual lithium-ion battery can withstand the abuse of overcharge, overheating, short circuit, etc.
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