lithium 18650 li ion battery

　　Technical dispute between lithium 18650 li ion battery and ternary lithium battery pack

　　The technical dispute between lithium iron phosphate batteries and ternary lithium battery packs. In the era of lithium batteries, the focus is on ternary lithium and lithium iron phosphate. In the future, who will win between ternary lithium and lithium iron phosphate? Ternary lithium battery packs and lithium iron phosphate batteries have not yet been able to To determine the winner, ternary lithium batteries have a slight advantage, but neither is a perfect solution at least at this stage.

　　Technical dispute between iron lithium battery and ternary lithium battery pack

　　There are four main commercial technology routes for power batteries in my country: lithium iron phosphate batteries, ternary batteries, lithium manganate and lithium titanate. Lithium manganese oxide batteries are mainly due to low energy density, while lithium titanate batteries are mainly due to high costs. Their total market share in the power battery market is less than 5%. The iron lithium battery route and the ternary lithium battery pack route have become the main routes in the power battery market, accounting for ~95% of the market share.

　　Lithium iron phosphate batteries are characterized by high safety, high rate charge and discharge characteristics and long cycle life. Literature shows that the charging conditions are charging to 3.65V at a 1C rate, then switching to constant voltage until the current drops to 0.02C, and then discharging at a 1C rate to a cut-off voltage of 2.0V. After 1,600 cycles, the battery capacity still remains 80% of the initial capacity. Lithium iron phosphate batteries also have good fast charging characteristics. Under 3C rate charging conditions, they can charge 55% in 15 minutes and charge more than 95% of their capacity in 30 minutes.

　　The biggest advantage of lithium iron phosphate batteries is their safety. Lithium iron phosphate has stable chemical properties and good high-temperature stability. It will only start to decompose at 700-800°C, and it will not be exposed to impacts, needle sticks, short circuits, etc. Releases oxygen molecules, will not cause violent combustion, and has high safety performance.

　　However, the disadvantage of lithium iron phosphate batteries is that their performance is greatly affected by temperature. Especially in low-temperature environments, the discharge capacity and capacity will be greatly reduced. In addition, the energy density of lithium iron phosphate is low. Calculating only the weight of the battery, the energy density is only 120Wh/kg. If the energy density of the entire stack, including the battery management system, heat dissipation and other components, is calculated, it 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 improvement of the 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. Different from lithium iron phosphate, the voltage platform of ternary lithium battery is very high, which means that under the same volume or weight, the specific energy and specific power of the ternary lithium battery pack are greater. In addition, ternary lithium batteries also have great advantages in terms of high-rate charging and low-temperature resistance.

　　The battle over the technical routes between ternary lithium battery packs and lithium iron phosphate seems huge, but for users and vehicle companies, the two technical routes actually have their own merits. In the final analysis, different models choose different batteries suitable for their operation, which is the root of the problem.

　　The thermal stability of the ternary lithium battery pack is poor, and it will decompose at 250-300°C. When encountering the flammable electrolyte and carbon materials in the battery, the heat generated will further intensify the decomposition of the positive electrode, and in a very short time It will explode. Although there are safety concerns, due to policy regulations on energy density, ternary lithium battery packs have shown a tendency to replace lithium iron phosphate batteries and become the mainstream of passenger cars.

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