Lithium is the lightest metal with the smallest atomic mass in nature. Its relative atomic mass is 6.94g/mol, =0.53g/cm3. Lithium is chemically very active and easily loses electrons and is oxidized into lithium ions. Therefore, the negative electrode potential of the standard electrode is the largest (-3.045V) and the electrochemical equivalent is the smallest (0.26g/Ah). These characteristics make lithium a high specific energy material. The ternary lithium battery refers to a lithium secondary battery using three transition metal oxides as the positive electrode material. Fully combine the characteristics of cobalt lithium oxide, with good cycle performance, with high specific capacity lithium nickelate, high safety and low cost lithium manganese, and through molecular level mixing, doping, synthesis and nickel, cobalt and manganese, etc. Coating and surface modification of composite oxide lithium in which various elements are intercalated. It is a kind of lithium ion that is currently widely researched and applied.
Ternary lithium battery life
The theoretical life of ternary lithium battery is about 800 times, which is at the middle level of commercial rechargeable lithium battery. Lithium iron phosphate has about 2,000 cycles, while lithium titanate is said to have 10,000 cycles. The current mainstream battery manufacturer's ternary battery specification promises 500 times (charge and discharge under standard conditions), but due to consistency issues, the important thing is that the voltage and internal resistance cannot be exactly the same. Its cycle life is about 400 times. The manufacturer recommends that the SOC use window is 10%~90%. It is recommended not to charge and discharge deeply, otherwise it will cause irreversible damage to the positive and negative structure of the battery. If the battery is calculated by light charging and light discharging, the cycle life of the battery is at least 1000 times. In addition, if the lithium battery is continuously exposed to high power and high temperature, the battery life will be greatly reduced to less than 200 times.
Ternary lithium battery has its advantages and disadvantages
Ternary lithium battery is a battery with excellent overall performance, balanced capacity and high safety. The important functions, advantages and disadvantages of the three metal elements are as follows:
CO3 +: Reduce the occupation of cation mixing, stabilize the layered structure of the material, reduce the impedance value, increase the conductivity, and improve the cycle and multiplier performance.
Ni2+: increase the capacity of the material (increase the volume and energy density of the material). However, due to the similar radii of lithium and nickel, excessive nickel content can also cause dislocation mixing of lithium and nickel. The higher the concentration of nickel ions in the lithium layer, the more difficult it is for the lithium ions in the layered structure to escape, resulting in poor electrochemical performance.
Mn4+: Not only can reduce the material cost, but also improve the safety and stability of the material. However, high manganese content easily forms a spinel phase, destroys the lamella structure, and reduces capacitance and cycle attenuation.
The biggest advantage of high-energy-density ternary lithium batteries, the platform is an important battery energy density and voltage, and the index determines the basic performance and cost of the battery. The higher the voltage platform, the greater the capacity of the concrete, then the same volume, The weight, even the same ampere hour battery, the high-voltage platform ternary material lithium battery has a longer life. The discharge voltages of single ternary lithium batteries are as high as 3.7V, 3.2V and 2.3V respectively. Therefore, from the perspective of energy density, ternary lithium batteries have absolute advantages over lithium iron phosphate, lithium manganate, and lithium titanate.
Poor safety and short cycle life are important shortcomings of ternary lithium batteries, especially their safety performance has become an important factor restricting their large-scale configuration and large-scale integrated applications. A large number of actual measurement results show that large-capacity ternary batteries are difficult to pass safety tests such as acupuncture and overcharge. This is also the reason why large-capacity batteries generally introduce more manganese elements, or even mix with lithium manganate. The 500-cycle life of ternary lithium batteries is in the middle of this range, so the important application areas of ternary lithium batteries are consumer electronics products, such as 3C digital products.