Do ternary lithium and lithium iron phosphate affect the performance of electric vehicles?

　　I believe many people have heard that lithium batteries for vehicles in the new energy automobile industry are divided into ternary polymer lithium batteries and lithium iron phosphate batteries. So, what are the differences in performance between these two kinds of batteries made of different materials? What makes these differences? Due to the change in the trend of government subsidies, BYD, which used to achieve mass production in the field of lithium iron phosphate batteries, began to develop lithium ternary on a large scale. Why? If you have seen lithium-ion batteries, you must understand the structure and principle of lithium-ion batteries. Its appearance is similar to our commonly used No. 5 battery, but its size is slightly larger. From the outside, we can see the positive and negative poles of the battery, as well as the whole battery shell. What is the internal structure and working principle of the battery? The battery is mainly composed of positive pole, negative pole, electrolyte and diaphragm. These materials are encapsulated in a cylindrical steel cylinder. Because there are many holes in the cathode material, it can store a lot of electrons. During the discharge, these electrons move to the positive material through an external circuit. When the battery is connected to an external consumer, a circuit is formed from the positive to the consumer and then to the negative. This is the basic working principle of the battery. In the basic charging and discharging schematic diagram of lithium ion battery, the anode material is actually our very common graphite. Because graphite naturally has many holes and good conductivity, its ability to hold electrons is much higher than that of cathode materials. Therefore, for lithium ion batteries, the important bottleneck lies in the cathode materials. This is also the reason why major battery companies continue to improve the performance of cathode materials to improve the charging capacity (energy density) of lithium ion batteries

　　Lithium ternary and lithium iron phosphate, as we often say, refer to cathode materials. In the field of traditional lead-acid batteries, dilute sulfuric acid with very low cost is used as the electrolyte. This is why when we replace the car battery for the first time, we sometimes fill the new battery with liquid. This liquid is an electrolyte. As the important component of dilute sulfuric acid is water, water will have conductivity under the action of acid particles, so it can form a current circuit inside the battery. However, due to the poor conductivity of water, the voltage of traditional lead-acid battery is less than 2 volts, while the voltage of lithium ion battery cell we use can reach 3-4 volts, so lithium salt should be used to replace the traditional water-based electrolyte. The function of the diaphragm is to block electrons and let them flow along the path of the external circuit, but ions can pass through the diaphragm to form a circuit without shorting the positive and negative electrodes. Charging and discharging principle of lithium-ion batteries The reason why lithium-ion batteries can be charged and discharged is that they convert electrical energy into chemical energy during charging and chemical energy into electrical energy during discharging. In short, during the charging process, lithium ions are embedded from the positive electrode material into the negative electrode material through the electrolyte; In the discharge process, lithium ions are embedded from the negative electrode material into the positive electrode material through the electrolyte, while electrons form a current through the external circuit

　　For lithium ion batteries, the performance of cathode materials is very important. It must have good conductivity, good compatibility with electrolyte and excellent stability. The performance of lithium iron phosphate is different from that of lithium ternary. Lithium iron phosphate battery has high safety and long cycle life. The experiment shows that after 1600 charge discharge cycles, the lithium iron phosphate battery can still maintain 80% of the power. In addition, the performance of lithium iron phosphate battery during high-power discharge is also very stable. This is a usage scenario we often encounter: when accelerating or running at high speed, the battery needs to discharge with high power. In this process, the voltage stability can make the vehicle have better performance. Moreover, in the process of high-power discharge, the actual capacity of the battery will decrease, which is one of the reasons why the high-speed driving range of electric vehicles will decrease. The stability performance of lithium iron phosphate battery is very outstanding. Another advantage of lithium iron phosphate is its high safety. It can withstand the high temperature of 700-800 ℃, and will not release oxygen molecules under extreme conditions such as puncture, impact and short circuit, and will not cause violent combustion and explosion. This is why BYD still uses lithium iron phosphate batteries on buses with large passenger capacity. Due to the large passenger capacity of buses, higher safety requirements than passenger cars, but less sensitive to weight and volume, lithium iron phosphate is a good choice. However, lithium iron phosphate also has two disadvantages that cannot be ignored: first, its energy density is relatively low, its weight is large, and its volume is large; Second, it is relatively sensitive to temperature. In low temperature environment, the charging capacity will be significantly reduced

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