The cycle life and pros & cons of ternary lithium ion battery

What is ternary lithium ion battery?

In nature, the Li is the lightest elements, smallest atomic mass metal. Its atomic mass is 6.94g/mol，ρ=0.53g/cm3. Due to active chemical property, it can easily lose e- and be oxidized to Li+. Therefore, its electrode potential is maximum negative number (-3.045V), electrochemical equivalent is also the minimum (0.26g/Ah). These features decide that it is a material with high specific energy. Ternary lithium ion battery is a secondary lithium ion battery using Nickel, Cobalt, Manganese, three transition metal oxide, as anode material. It has the combination features of nice cycle performance from lithium cobalt oxides, high specific capacity from lithium nickelate, good safety performance from lithium manganite, low cost and so on, utilizing the method of molecule horizontal mixing, doping, coating and decoration to compose compounding lithium oxide with Nickel, Cobalt, Manganese element. Ternary lithium ion battery is a rechargeable lithium ion battery that was widely researched and applied at present.

The lifespan of ternary lithium ion battery

The lifespan of lithium ion battery means 70% of rated capacity that decays after using for some time. At this moment, the battery is worn out. The battery industry tends to describe the cycle life by charging and discharging times of the lithium ion battery. During the application, the irreversible electrochemical reaction inside the battery will lessen the capacity. For example, decomposition of electrolyte, inactivation of active material, collapse of anode and cathode structure lessens the insertion and de-intercalation of Li ion. The examination shows that higher rate discharging will lead in faster decay. If the discharging current is low, the voltage will be closed to balanced voltages and the battery can discharge more energy.

The rated cycle life of ternary lithium ion battery is around 800 times, belonging to the medium level in rechargeable lithium ion battery market. lithium iron phosphate is 2000 times, while lithium titanate can reach 10,000 times. Nowadays, the mainstream battery manufacturers promise for over 500 times on their ternary cell specification (charge and discharge under standard situation). However, after the cell being made into battery pack, the cycle life is about 400 times, because the voltage cannot be the same as the internal resistance due to the consistence issue. SOC recommended by the manufacturer is 10%~90%. It has better not discharge deeply, or it may damage the anode and cathode structure irreversibly. If calculate by small current charging and discharging, the cycle life will have at least 1000 times. Besides, the cycle life will rapidly decrease to no more than 200 times after frequent discharging under high rated and high temperature environment.

The pros & cons of ternary lithium ion battery

Ternary lithium ion battery is a battery with high properties for its stable capacity and safety performance. The advantages and disadvantages of three kinds of metal elements are as follow:

Co3+: lessen the site occupancy of positive ions, stabilize the stratified structure of the material, decrease resistance value, increase conductivity, improve cycle and rate performance.

Ni2+: It can increase the capacity of material (increase volume energy density of material). Excessive Ni may lead to dislocation phenomena of Li and Ni due to their similar radius. The larger concentration of Li ion, the more difficult for Li with stratified structure to disembed, which affects the electrochemical performance.

Mn4+: it can not only decrease the material cost, but also can improve the safety and stability of the material. However, excessive Mn content will easily produce spinel to damage the stratified structure and decrease the capacity and cycle times.

High energy density is one of the advantages of ternary lithium ion battery, which voltage platform is one of its key indicators, deciding on the basic performance and cost. The higher voltage platform, the larger specific capacity is. So compared with the batteries with the same volume, weight and even AH, ternary lithium ion battery with higher voltage platform will have longer power life. The voltage of ingle ternary lithium ion battery reaches 3.7V, lithium iron phosphate is 3.2V, while lithium titanate is only 2.3V. in term of energy density, ternary lithium ion battery is apparently better than lithium iron phosphate, lithium manganite or lithium titanate.

Poor safety performance and cycle life are the main shortcomings, especially safety performance, which always limits the large-scale assembling and is also one of the main factors of large-scale integrated application. Experiments show that ternary lithium ion battery with bigger capacity is difficult to pass the acupuncture and overcharging safety test. This is the reason why battery with large capacity needs to lead in many Mn, and even apply together with lithium manganite. Cycle life of 500 times is below the medium level in lithium ion battery field. Therefore, ternary lithium ion battery tends to apply in consumer electronics, such as 3c digital.