Power battery safety should not be underestimated lithium titanate battery advantages highlighted

During the "May Day" period, a series of electric bus fires occurred in the parking lot of the Crab Island Resort in Chaoyang District, Beijing, causing people to pay more attention to the safety of new energy vehicle batteries.
​With the increase in the number of commercial applications of electric vehicles, spontaneous combustion, fire and explosion of lithium-ion power batteries for electric vehicles occur from time to time, and it is a key opportunity for the development of the electric vehicle industry, any electric vehicle safety accident not only has a major impact on the manufacturing enterprises involved, but also a heavy blow to the entire industry. Power battery is the core components of electric vehicles, electric vehicles fire or explosion, people's first thought is often the battery problem, so now the battery of electric vehicles in the end is safe?
​Battery mechanism analysis lithium titanate material has better safety performance
​From the perspective of battery mechanism, the fire and explosion of lithium-ion battery is caused by the thermal runaway of lithium-ion battery, and the root cause is the violent chemical exothermic reaction between the electrode and the electrolyte under appropriate conditions. At present, the positive electrode materials commercially used in lithium-ion power batteries are lithium iron phosphate, lithium nickel-cobalt manganate, lithium nickel-cobalt aluminate and lithium manganate, etc. The main anode materials are graphite or its composite materials and lithium titanate, etc. The electrolyte is mainly composed of organic solvent and lithium salt, and the main component of the diaphragm is polypropylene, polyethylene or composite materials of both.
​For the positive electrode material, the temperature required for thermal decomposition of lithium iron phosphate is the highest, and the heat released by its decomposition is the least, which is the best safety of the positive electrode material at present. In the negative electrode material, the reaction temperature of the graphite negative electrode and the electrolyte is the lowest, the easiest reaction with the electrolyte, the highest heat released, and the decomposition reaction temperature of the lithium titanate negative electrode is not only higher than the reaction of graphite and the electrolyte, but the heat released is much lower than the heat released by the graphite reaction, so the safety of lithium titanate material is much higher than the graphite negative electrode.
​In addition, in the charge and discharge cycle of the power battery, some physical and chemical changes in the battery composition will lead to the decline of the battery performance, and these changes will affect the safety of the battery to a certain extent. In fact, in the actual use of the battery after delivery, accidents such as battery fire often occur. The existing research results on the safety of uncycled fresh batteries cannot fully explain the accident mechanism. Different materials, different capacities, and different designs may have different electrochemical or abuse resistance behaviors during the battery cycle. According to the different anode materials used, the common power batteries on the market are divided into two categories, carbon negative system and lithium titanate negative system battery.
​Since the potential after the carbon negative electrode is embedded with lithium is very close to the potential of lithium metal, the deposition of lithium metal generally occurs on the surface of the negative electrode. When lithium ions migrate to the negative surface, some lithium ions do not enter the negative active material to form a stable compound, but obtain electrons and deposit on the negative surface to become lithium metal, and gradually form lithium dendrites. With the continuous increase of the number of cycles, the internal polarization is intensified, and the lithium dendrites continue to grow with the cycle of the lithium-ion battery, which may penetrate the diaphragm and cause a short circuit of the positive and negative poles. After nearly a thousand cycles of the battery, due to changes in the structure of the battery material (continuous expansion and contraction) and the accumulation of side reaction products (lithium evolution), there are many bumps on the surface of the negative carbon electrode. This change not only affects the electrode structure and activity, but also causes the diaphragm to be stressed and deformed, increasing the possibility of damage. It is easy for the battery to get out of control in the experiment of short circuit, extrusion and overcharge.
​Compared with carbon anode materials, lithium titanate materials are known as "zero-strain materials", high stability, with a higher lithium input potential (1.55Vvs.Li+/Li), fundamentally eliminating the production of metal lithium dendrites, reducing the risk of internal short circuits in the battery. The reaction activity between lithium titanate and electrolyte is low, and almost no SEI film is generated, so it has good cycle stability and safety, and its cycle life at room temperature can reach more than 25,000 times. At very high temperatures, lithium titanate is able to absorb the oxygen generated by the decomposition of the positive electrode, reducing the risk of thermal runaway and improving the safety of the battery. Using lithium titanate instead of carbon material as the negative electrode of lithium-ion battery provides a solid foundation for ensuring the safety of lithium-ion battery and improving the cycle performance and service life of the battery.
​Lithium titanate firmly practices the mission of battery safety
​The safety of the power battery depends more on the material itself and the manufacturing process, and the high safety of the lithium titanate battery effectively solves the problems caused by the security risks for the promotion and application of new energy batteries. Lithium titanate batteries have incomparable advantages in terms of the most important safety. Following the new national standard, lithium titanate battery after acupuncture, drill, cutting and other "cruel" experiments, and no fire, explosion and other phenomena, withstood the test of safety testing. The market acceptance of lithium titanate battery technology continues to increase, and has now formed a tripartite situation in the power lithium battery market with ternary lithium batteries and lithium iron phosphate batteries.
​Lithium titanate battery is lithium battery with the longest life and the highest safety. The cycle life of lithium titanate battery is long, and it can achieve more than 10,000 charge and discharge cycles, which is higher than that of ordinary lithium batteries. Moreover, the lithium titanate fast charging performance is very good, and its charging rate not only reaches 6C equivalent to lithium iron phosphate and ternary, but also can realize the charging rate of 10C of electrochemical supercapacitors. This proves on the other hand that lithium titanate is actually very widely used.
​At present, the domestic market technology of lithium titanate battery is relatively mature, mainly used in the application of electric vehicles for buses and ferrybuses and other fields, the domestic production of lithium titanate material is relatively early Yinlong, micro macro, Bo Lei Da, etc., foreign Toshiba in 2007 had a lithium ion battery based on lithium titanate negative electrode came out. Among them, the lithium titanate battery represented by Yinlong has overcome the "five major problems" recognized in the industry, achieving 6-minute fast charging, wide temperature resistance (-50℃ - +60℃), 30-year cycle life, high safety without fire and explosion, high efficiency and other excellent characteristics. However, the low energy density of lithium titanate batteries is its biggest drawback, at present, the energy density gap between lithium titanate batteries and lithium iron phosphate batteries is also shrinking.