A ternary battery refers to a ternary lithium-ion battery, refers to the lithium-ion battery in which the positive electrode material uses lithium nickel cobalt manganese (Li (NiCoMn) O2) ternary positive electrode material. The precursor product of the ternary composite positive electrode material is based on nickel salt, Cobalt salt, and manganese salt are used as raw materials, and the ratio of nickel, cobalt, and manganese in it can be adjusted according to actual needs. The battery with ternary material as the positive electrode is safer than a lithium cobalt oxide battery.
Ternary lithium batteries are suitable for power batteries or small batteries, especially batteries with relatively high capacity. At present, batteries of ternary materials have replaced the lithium cobalt oxide batteries that were widely used before, and are widely used in the field of notebook batteries.
At present, there are two kinds of important and popular lithium-ion batteries on the market: iron phosphate lithium-ion batteries and ternary lithium-ion batteries. Under such circumstances, which is better, a ternary lithium-ion battery or a lithium iron phosphate battery? Let’s see which of the two is better.
One. Lithium iron phosphate battery
Lithium iron phosphate battery: The raw material phosphorus and iron are abundant in the earth, and the supply channels are less restricted. Moderate voltage (3.2V), large capacity per unit weight (170mAh/g), high discharge power, fast charging and long cycle life, and higher stability in high temperature and high heat environments than other types of batteries.
Advantages and disadvantages of LiFePO4 battery
Lithium iron phosphate battery is a lithium-ion battery that uses lithium iron phosphate (LiFePO4) as the positive electrode material and carbon as the negative electrode material. The rated voltage of the single cell is 3.2V, and the charging cut-off voltage is 3.6V~3.65V. Because its performance is particularly suitable for power applications, the word “power” is added to the name, that is, lithium iron phosphate power battery. Some people also call it a “lithium iron (LiFe) power battery”.
Lithium iron phosphate battery is a kind of lithium battery. Like the battery used in our mobile phones, it is named because the positive electrode material of lithium iron phosphate battery is mainly a compound of phosphorus, acid, iron, and lithium. The following is a detailed introduction to the advantages and disadvantages of this new material.
Advantages of LiFePO4 battery
1. Good safety performance
The P-O bond in lithium iron phosphate crystal is stable and difficult to decompose. Even at high temperatures or overcharge, it will not collapse and generate heat or form strong oxidizing substances like lithium cobalt oxide, so it has good safety. Some reports pointed out that in the actual operation, a small part of the samples was found to burn in acupuncture or short-circuit experiments, but no explosion occurred. In the overcharge experiment, a high voltage charge that was several times higher than the self-discharge voltage was used, and it was found that there were still some samples. explosion phenomenon. Even so, its overcharge safety has been greatly improved compared with ordinary liquid electrolyte lithium cobalt oxide batteries.
2. Long life
The cycle life of long-life lead-acid batteries is about 300 times, and the maximum is 500 times, while the cycle life of lithium iron phosphate power batteries can reach more than 2000 times, and the standard charge (5-hour rate) can reach 2000 times. Lead-acid batteries of the same quality are “new for half a year, old for half a year, and maintained for half a year”, which is 1 to 1.5 years at most, while LiFePO4 batteries is used under the same conditions, and their theoretical life will reach 7 to 8 years. Considering comprehensively, the performance-price ratio is theoretically more than 4 times that of lead-acid batteries. High current discharge can quickly charge and discharge high current 2C. Under the special charger, the battery can be fully charged within 40 minutes after charging at 1.5C, and the starting current can reach 2C, while lead-acid batteries do not have this performance.
3. Good high-temperature performance
The electric heating peak of lithium iron phosphate can reach 350°C-500°C, while lithium manganese oxide and lithium cobalt oxide are only around 200°C. The working temperature range is wide (-20C–75C), and it has high-temperature resistance. The electric heating peak of lithium iron phosphate can reach 350°C-500°C, while lithium manganese oxide and lithium cobalt oxide are only around 200°C.
4. Large capacity
The capacity of the battery will quickly drop below the rated capacity value when the battery is often fully charged, this phenomenon is called the memory effect. NiMH and NiCd batteries have memory, but LiFePO4 batteries do not have this phenomenon. No matter what state the battery is in, it can be charged and used at any time, and there is no need to discharge it first and then recharge it.
5. Lightweight
The volume of the lithium iron phosphate battery with the same specification and capacity is 2/3 of the volume of the lead-acid battery, and the weight is 1/3 of the lead-acid battery.
6. Environmental protection
LiFePO4 batteries are generally considered to contain no heavy metals and rare metals (rare metals are required for nickel-hydrogen batteries), are non-toxic (SGS certified), non-polluting, and comply with European RoHS regulations, which is an absolute green battery certificate. Therefore, the reason why lithium batteries are favored by the industry is mainly due to environmental protection considerations. Therefore, this battery has been included in the “863” national high-tech development plan during the “Tenth Five-Year Plan” period and has become a project supported and encouraged by the state.
LiFePO4 battery also has their disadvantages: for example, poor low-temperature performance, the low tap density of positive electrode materials, and equal-capacity LiFePO4 batteries are larger than lithium-ion batteries such as lithium cobalt oxide, so they do not have advantages in micro-batteries. When used in power batteries, LiFePO4 batteries, like other batteries, need to face the problem of battery consistency.
Disadvantages of LiFePO4 batteries
Whether a material has application development potential, in addition to focusing on its advantages, is more critical than whether the material has fundamental defects.
1. The tap density of the positive electrode of the lithium iron phosphate battery is small, the density is generally around 0.8 to 1.3, and the volume is large.
2. The electrical conductivity is poor, the lithium-ion diffusion rate is slow, and the actual specific capacity is low when charging and discharging at a high rate.
3. The low-temperature performance of the LiFePO4 battery is poor.
4. The life of a single lithium iron phosphate battery is long, about 2000 times, but the life of a lithium iron phosphate battery pack is short, generally about 500 times.
Currently, the most common lithium batteries on the market are lithium cobalt oxide (LiCoO2) and lithium manganate. As a kind of lithium battery, lithium iron phosphate is mainly used in the field of power systems, such as electric steam, automobiles, military aerospace, power tools, and uninterruptible power supplies. It has attracted much attention because of its excellent structural stability and safety performance. And it has a longer service life, so it is more suitable for use in the field of power systems.
Two. Ternary lithium battery
Ternary polymer lithium-ion battery: a lithium-ion battery whose positive electrode material uses nickel-cobalt manganese oxide (Li(NiCoMn)O2) ternary positive electrode material, especially refers to the positive electrode is ternary, the negative electrode is graphite “ternary power lithium battery “. The other kind of positive electrode is ternary and the negative electrode is lithium titanate, which is usually called “lithium titanate” and does not belong to the so-called “ternary material.”
The ternary lithium-ion battery has high energy density and better cycle performance than normal lithium cobaltate. At present, with the continuous improvement of the formula and the improvement of the structure, the nominal voltage of the battery has reached 3.7V, and the capacity has reached or exceeded the level of the cobalt-acid lithium-ion battery.
Ternary lithium battery is a secondary lithium-ion battery that uses three nickel-cobalt-manganese transition metal oxides as positive electrode materials. It fully combines the good performance of the lithium cobalt oxide cycle, the high specific capacity of lithium nickel oxide, and the high safety and low cost of lithium manganese oxide. Composite lithium intercalation oxides with multiple elements such as cobalt and manganese at the molecular level. It is a rechargeable lithium-ion battery that has been extensively researched and applied.
Advantages and disadvantages of ternary lithium battery
The advantages of ternary lithium batteries are smaller volumes, higher capacity density, low-temperature resistance, and better cycle performance, which is the mainstream of new energy passenger vehicles. Disadvantages: poor thermal stability, it will decompose at 250-300°C, and the chemical reaction of ternary lithium materials is particularly strong. Once the oxygen molecules are released, the electrolyte will burn rapidly under the action of high temperature, and then deflagration will occur.
Ternary lithium batteries are relatively balanced in terms of capacity and safety and are batteries with excellent overall performance. The important functions, advantages, and disadvantages of these three metal elements are as follows:
Co3+: Reduce the mixed occupation of cations, stabilize the layered structure of the material, reduce the resistance value, increase the conductivity, and improve the cycle performance and speed. Ni2+: The capacity of the material can be increased (the energy density of the increased material volume). Since the radii of Li and Ni are similar, too much Ni will also cause Li-Ni mixed discharge due to dislocations with Li and the concentration of Ni ions in the Li layer. The larger the lithium, the more difficult it is to deinterlace it in the layered structure, leading to poor electrochemical performance.
Mn4+: It can not only reduce the material cost but also improve the safety and stability of the material. However, if the content of Mn is too high, the spinel phase will easily appear and the layered structure will be destroyed, thus reducing the capacity and attenuation of the cycle.
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 batteries. An-time batteries with higher voltage platforms and ternary material lithium-ion batteries have longer battery life. The discharge voltage platform of a single ternary lithium battery is as high as 3.7V, that of lithium iron phosphate is 3.2V, and that of lithium titanate is only 2.3V. Therefore, from the perspective of energy density, ternary lithium batteries are superior to lithium phosphate, lithium manganate, or lithium titanate and have absolute advantages.
Poor safety and short cycle life are important disadvantages of ternary lithium batteries, especially the safety performance, which has become an important factor limiting their large-scale implementation and large-scale integration applications. A large number of actual tests have shown that it is difficult for large-capacity ternary batteries to pass safety tests such as acupuncture and overloading, which is why large-capacity ternary batteries usually introduce more manganese or even use manganese salts.
How many years is the lifespan of a ternary lithium battery?
The theoretical lifespan of a ternary lithium battery is about 800 cycles, which is the average lifespan among commercially available rechargeable lithium-ion batteries. Lithium iron phosphate lasted about 2,000 cycles, while lithium titanate reached 10,000 cycles. At present, traditional battery manufacturers have promised that the specifications of their ternary batteries are more than 500 times (charging and discharging under standard conditions), but after assembling the battery pack into a battery pack, due to the problem of resistance, the relationship between resistance and internal resistance Can not be the same, its lifespan is about 400 times.
Three. Comparison of lithium iron phosphate lithium-ion battery and ternary lithium battery
1. In terms of the richness of raw materials, LiFePO4 batteries are more abundant than ternary lithium-ion batteries (containing cobalt, which is a precious and rare mining city);
2. In terms of manufacturing cost, LiFePO4 batteries are cheaper than ternary lithium-ion batteries, and are more suitable for the low-end market demand;
3. The energy density of the ternary lithium-ion battery is higher than that of the lithium iron phosphate battery. Under the same battery space, the capacity of the ternary lithium-ion battery is larger;
4. In terms of environmental temperature adaptation and stability, iron phosphate lithium-ion batteries are better than ternary polymer lithium-ion batteries. It can be seen that these two batteries have their advantages, depending on the environment in which the product is used.
5. In terms of service life, the theoretical value of LiFePO4 battery is longer than that of ternary lithium-ion batteries;
6. In terms of high-temperature resistance, the electric heating peak of lithium iron phosphate can reach 350°C-500°C, while lithium manganate and lithium cobaltate are only around 200°C;
7. In terms of low-temperature performance, ternary lithium-ion batteries are better than lithium-iron phosphate batteries;
Compared with LiFePO4 batteries, ternary lithium batteries have a much higher weight and energy density, about 200Wh/kg, which means that ternary lithium batteries of the same weight have a longer cruising range than LiFePO4 batteries.
However, its disadvantages are also obvious. When its temperature is 250-350 ° C, the internal chemical composition begins to decompose, so it puts forward extremely high requirements for the battery management system, and it is necessary to install a safety device for each battery. In addition, due to the small size of the single cell, the number of battery cells required for a bicycle is very large. Taking MODEL S as an example, more than 7,000 18650 ternary lithium batteries can meet the assembly consumption of a car, which undoubtedly provides a further step for the battery management system. Increased control difficulty. Therefore, among the models currently on sale in the market, only Tesla uses ternary lithium batteries.
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