Lithium is the lightest metal with high specific energy, and it has the smallest atomic mass (its atomic weight is 6.94g/mol, ρ=0.53g/cm3).
A ternary power lithium battery is a lithium secondary battery that uses nickel-cobalt-manganese, three transition metal oxides, as the cathode material. It integrates the good cycling performance of lithium cobaltate, the high specific capacity of lithium nickelate, and the high safety and low cost of lithium manganese.
Ternary power lithium battery also synthesizes the synergistic composite inlaid lithium oxide, such as nickel-cobalt-manganese, using molecular level mixing, wrapping, and surface modifications. the ternary power lithium battery is a type of lithium-ion rechargeable battery that is widely studied and used.
Ternary power lithium battery life
Lithium battery life refers to the battery after a period of use specifically when the capacity of the battery has decayed to 70% of the nominal capacity (at room temperature 25 ℃, standard atmospheric pressure, and battery capacity discharged at 0.2C). The industry generally calculates the cycle life of a lithium battery by the number of full discharge cycles.
Over the course of use, lithium batteries undergo irreversible electrochemical reactions inside the battery, leading to a decrease in capacity, such as the breakdown of the electrolyte, the inactivation of the active material, the collapse of the positive and negative electrode structure, resulting in a decrease in the number of lithium ions embedded and de-embedded, etc.
Experiments have shown that higher-magnification discharges lead to faster capacity decay, and if the discharge current is lower, the battery voltage will be closer to the equilibrium voltage, which can release more energy.
The theoretical life of a lithium battery is about 800 cycles, which is moderate among commercially available rechargeable lithium batteries. Lithium iron phosphate is about 2,000 cycles while lithium titanate is said to reach 10,000 cycles.
Battery manufacturers promise more than 500 cycles under standard conditions in the specifications of their ternary batteries, but, due to consistency problems (the voltage and internal resistance can not be exactly the same), its cycle life is about 400 cycles. Manufacturers recommend the use of a SOC window of 10-90%, is not recommended for deep charge and discharge as it may cause irreversible damage to the positive and negative structure of the battery. In addition, if the lithium battery is frequently discharged in high magnification and high-temperature environment, the battery life can reduce to less than 200 cycles.
Ternary power lithium battery material
The ternary power lithium battery is a comprehensive and excellent battery with a balanced capacity and safety. The main roles, advantages, and disadvantages of the three metal elements are as follows:
Co3+ reduces cationic mixing occupancy, stabilizes the laminar structure of the material, reduces impedance value, improves conductivity, and improves cycling and multiplication performance.
Ni2+ can improve the capacity of the material (improve the volumetric energy density of the material); however, because lithium and nickel have a similar radius, too much nickel will also cause the dislocation phenomenon with lithium, resulting in lithium-nickel mixing. The greater the concentration of nickel ions in the lithium layer, the more difficult the lithium in the laminar structure, resulting in poor electrochemical performance.
Mn4+ not only reduces material costs but also improves the safety and stability of the material. However, too much Manganese will make the battery prone to the emergence of the spinel phase and destroy the laminar structure, resulting in reduced capacity and cyclic decay.
Ternary power lithium battery energy density
When compared to lithium iron phosphate, lithium manganate, or lithium titanate, high energy density is the biggest advantage of ternary lithium batteries. The voltage platform is an important indicator of the battery energy density, which determines the basic performance and cost of the battery. The higher the voltage platform, the larger the capacity.
The discharge voltage platform of a single ternary lithium battery is as high as 3.7V, 3.2V for lithium iron phosphate, and only 2.3V for lithium titanate, so, in terms of energy density, the ternary lithium battery has an absolute advantage over lithium iron phosphate, lithium manganate or lithium titanate.
Poor safety and short cycle life are the main shortcomings of ternary lithium batteries. Safety performance has especially been a major factor limiting its large-scale packaging and large-scale integrated applications. The 500-cycles cycle life in a lithium battery is medium to low, so the ternary lithium battery is the most important application field in 3C digital and other consumer electronics.