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Technical analysis of lithium iron battery and ternary lithium battery pack

by:Vglory      2021-05-08
Lithium iron phosphate batteries are characterized by high safety, high rate charge and discharge characteristics and long cycle life. The literature shows that under the charging condition of 1C rate charging to 3.65V, then switching to constant voltage until the current drops to 0.02C, and then discharging to the cut-off voltage of 2.0V at 1C rate, the battery capacity still has 80% of the initial capacity after 1600 cycles. Lithium iron phosphate batteries also have good fast charging characteristics. Under the condition of 3C rate charging, they can be charged 55% in 15 minutes, and the capacity is more than 95% in 30 minutes. The biggest advantage of lithium iron phosphate battery is its safety. The chemical properties of lithium iron phosphate are stable, and the high temperature stability is good. Analysis will only start at 700-800℃, and it will not be exposed to impacts, needle sticks, short circuits, etc. It releases oxygen molecules, no violent combustion occurs, and the safety performance is high. However, the disadvantage of the lithium iron phosphate battery is that its performance is greatly affected by temperature, especially in a low temperature environment, the discharge capacity and capacity will be greatly reduced. In addition, the energy density of lithium iron phosphate is low. The energy density of the battery is only 120Wh/kg. If the energy density of the entire stack, including the battery management system, heat dissipation and other components is calculated, the energy density is even lower. In the field of small passenger cars, ternary lithium battery packs have completely replaced lithium iron phosphate batteries. The ternary lithium battery pack has high energy density and better cycle performance than normal lithium cobalt oxide. At present, with the continuous improvement of the formula and the perfect structure, the nominal voltage of the battery has reached 3.7V, and the capacity has reached or exceeded the level of lithium cobalt oxide batteries. Ternary lithium battery refers to a lithium battery that uses lithium nickel cobalt manganate as the positive electrode material and graphite as the negative electrode material. Unlike lithium iron phosphate, the ternary lithium battery has a high voltage platform, which means that the specific energy and specific power of the ternary lithium battery pack are greater under the same volume or weight. In addition, ternary lithium batteries also have great advantages in terms of high-rate charging and low-temperature resistance. The competition between the ternary lithium battery pack and the lithium iron phosphate technical route seems huge, but for users and vehicle companies, the two technical routes actually have their own merits. In the final analysis, choosing different batteries for different models is the root of the problem. The thermal stability of the ternary lithium battery pack is poor, and analysis will occur at 250-300°C. It will stop after encountering the combustible electrolyte and carbon materials in the battery, and the heat that appears will further aggravate the positive electrode analysis, in a very short time It will deflagrate. Although there are safety concerns, ternary lithium battery packs have shown a trend to replace lithium iron phosphate batteries and become the mainstream of passenger cars because of the policy's energy density regulations. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete it. Previous: Is the electrolyte an important part of protecting the safety of lithium batteries?
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