Introduction to the lifespan, advantages and disadvantages of ternary lithium batteries

Ternary lithium battery refers to a lithium secondary battery that uses three transition metal oxides of nickel, cobalt and manganese as positive electrode materials. It fully combines the good cycle performance of lithium cobalt oxide, the high specific capacity of lithium nickel oxide and the high safety and low cost of lithium manganese oxide. It uses molecular level mixing, doping, coating and surface modification methods to synthesize composite lithium-intercalated oxides of nickel, cobalt and manganese and other multi-elements. It is a lithium-ion rechargeable battery that is currently widely studied and applied.

The life of ternary lithium battery

The so-called lithium battery life refers to the end of life when the capacity of the battery decays to 70% of the nominal capacity (battery capacity at room temperature 25°C, standard atmospheric pressure, and discharged at 0.2C) after a period of use. The industry generally calculates the cycle life of lithium batteries by the number of cycles of full charge and discharge.

The theoretical life of a ternary lithium battery is about 800 cycles, which is medium among commercial rechargeable lithium batteries. Lithium iron phosphate is about 2,000 times, while lithium titanate is said to be able to reach 10,000 cycles. Currently, mainstream battery manufacturers promise more than 500 times (charge and discharge under standard conditions) in the specifications of their ternary batteries. However, after the batteries are assembled into battery packs, due to consistency issues, mainly the voltage and internal resistance cannot be exactly the same, the cycle life is about 400 times. In addition, if lithium batteries are frequently discharged at high rates and high temperatures, the battery life will drop significantly to less than 200 times.

Advantages and disadvantages of ternary lithium batteries

The ternary lithium battery is relatively balanced in terms of capacity and safety, and is a battery with excellent overall performance.

High energy density is the biggest advantage of ternary lithium batteries, and voltage platform is an important indicator of battery energy density, which determines the basic performance and cost of the battery. The higher the voltage platform, the greater the specific capacity. Therefore, for batteries of the same volume, weight, and even the same ampere-hour, ternary lithium batteries with a higher voltage platform have a longer battery life. The discharge voltage platform of a single ternary lithium battery is as high as 3.7V, lithium iron phosphate is 3.2V, and lithium titanate is only 2.3V. Therefore, from the perspective of energy density, ternary lithium batteries have an absolute advantage over lithium iron phosphate, lithium manganese oxide, or lithium titanate.

Poor safety and short cycle life are the main shortcomings of ternary lithium batteries, especially safety performance, which has always been a major factor limiting its large-scale assembly and large-scale integrated application. A large number of actual tests have shown that it is difficult for ternary batteries with larger capacity to pass safety tests such as puncture and overcharging. This is also the reason why large-capacity batteries generally require more manganese elements, and even mixed with lithium manganese oxide. The cycle life of 500 times is lower than the average among lithium batteries, so the main application area of ​​ternary lithium batteries is currently 3C digital and other consumer electronic products.