What is the charging principle of lithium batteries?

       Ternary lithium battery refers to a lithium secondary battery that uses three transition metal oxides of nickel, cobalt and manganese as the positive electrode material. It fully integrates the good cycle performance of lithium cobalt oxide, the high specific capacity of lithium nickelate and the high safety and low cost of lithium manganate. It uses molecular level mixing, doping, coating and surface modification methods to synthesize nickel. Cobalt and manganese and other multi-element synergistic composite lithium intercalation oxides. It is a lithium-ion rechargeable battery that is widely researched and applied.

　　The life of ternary lithium battery

　　 The so-called lithium battery life refers to the battery's capacity decay to 70% of the nominal capacity (the battery capacity at room temperature 25°C, standard atmospheric pressure, and 0.2C discharge) after a period of use, and the life can be considered as the end of life. In the industry, the cycle life is generally calculated by the number of cycles of fully charged and discharged lithium batteries.

　　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 cycles, while lithium titanate is said to be able to reach 10,000 cycles. At present, mainstream battery manufacturers promise more than 500 times (charge and discharge under standard conditions) in the specifications of their ternary battery cells. However, after the batteries are assembled into a battery pack, due to consistency problems, the main voltage and internal The resistance can not be exactly the same, and its cycle life is about 400 times. In addition, if lithium batteries are frequently discharged under high-rate and high-temperature environments, the battery life will be drastically reduced to less than 200 times.

　　 The 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 the voltage platform is an important indicator of battery energy density, which determines the basic efficiency and cost of the battery. The higher the voltage platform, the larger the specific capacity, so the same volume, weight, and even the same Ampere’s battery, the ternary material lithium battery with a higher voltage platform has a longer battery life. The discharge voltage platform of the single ternary lithium battery is as high as 3.7V, the lithium iron phosphate is 3.2V, and the lithium titanate is only 2.3V. Therefore, from the perspective of energy density, the ternary lithium battery is better than lithium iron phosphate, lithium manganate or Lithium titanate has an absolute advantage.

　　Poor safety and short cycle life are the main shortcomings of ternary lithium batteries, especially the safety performance, which has been a major factor that has restricted its large-scale matching and large-scale integrated applications. A large number of actual tests show that it is difficult for ternary batteries with larger capacity to pass safety tests such as acupuncture and overcharge. This is also the reason why more manganese elements are generally introduced in large-capacity batteries, or even mixed with lithium manganate. The cycle life of 500 times is in the middle of the lithium battery, so the main application field of the ternary lithium battery is consumer electronic products such as 3C digital.