Summary: Lithium iron phosphate battery refers to a lithium-ion battery using lithium iron phosphate as the cathode material. The full name of lithium iron phosphate battery is lithium iron phosphate battery, called lithium iron phosphate battery. 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) battery”. The cathode materials of lithium ion batteries mainly include lithium cobalt oxide, lithium manganate, lithium nickel oxide, ternary materials, lithium iron phosphate, etc. Among them, lithium cobalt oxide is the cathode material currently used in most lithium-ion batteries. Let's take a look at the advantages and disadvantages of lithium iron ph batteriesosphate. 1. Eight advantages of lithium iron phosphate batteries
1. Improved safety performance
The P-O bond in lithium iron phosphate crystal is stable and difficult to decompose even at high temperatures or overcharge. Unlike lithium cobalt oxide, the structure will not collapse and generate heat or form strong oxidizing substances, so it provides good safety. According to some reports, in actual operations, a small number of samples burned during acupuncture or short circuit experiments, but no explosion occurred during overload experiments, high voltage charging several times higher than the discharge voltage was used. , and it was found that there were still explosion phenomena. Despite this, its overcharge safety has been significantly improved compared to ordinary liquid electrolyte, lithium and o-acid batteries.cobalt oxide.
2. Improved lifespan
Lithium iron phosphate battery refers to a lithium-ion battery using lithium iron phosphate as the cathode material.
The lifespan of long-life lead-acid batteries is about 300 times, and the maximum is 500 times, while the lifespan of lithium iron phosphate batteries reaches more than 2,000 times when used with standard batteries. When charging (5 hours rate), it can reach 2000 times. Lead-acid batteries of the same quality last “six months for new ones, six months for old ones and another six months for maintenance”, or 1 to 1.5 years at most. However, when used under the same conditions, the theoretical life of lithium iron phosphate batteries will reach 7 to 8 years. Overall, the performance-price ratio is theoretically more than 4 times higher than that of lead-acid batteries. An electric current dischargeevé can quickly charge and discharge at a high current of 2C. Under a special charger, the battery can be fully charged in 40 minutes at 1.5C, and the starting current can reach 2C. performance.
3. Good high temperature performance
The electric heating peak of lithium iron phosphate can reach 350℃ - 500℃, while the maximum value of lithium manganate and lithium iron oxide cobalt is only about 200℃. It has a wide operating temperature range (-20°C to +75°C) and features high temperature resistance. The electric heating peak of lithium iron phosphate can reach 350℃ - 500℃, while lithium manganate and lithium cobalt oxide are only about 200℃.
4. Large capacity
Has a larger capacity than ordinary batteries (lead-acid, etc.). 5AH-1000AH (single unit)
5. No memory effect
When the batteries rechargegeables often operate in conditions where they are often fully charged and not fully discharged, the capacity decreases quickly. fall below the rated capacity value. This phenomenon is called memory effect. Nickel metal hydride and nickel cadmium batteries have memory, but lithium iron phosphate batteries do not have this phenomenon. Regardless of the state the battery is in, it can be charged and used at any time, and there is no need to discharge it first. then charge it.
6. Light weight
The volume of a lithium iron phosphate battery with the same specifications and capacity is 2/3 that of a lead-acid battery, and its weight is 1/3 that of a lead acid battery. a lead acid battery.
7. Environmental protection
The battery is generally considered to be free of heavy metals and rare metals (nickel-metal hydride batteries requireess rare metals), non-toxic (SGS certified). ), and non-polluting. It complies with European RoHS regulations and is an absolute ecological battery certificate. Therefore, the reason why lithium batteries are favored by the industry is mainly due to environmental protection considerations. Therefore, the battery was included in the national high-tech development plan “863” during the “Tenth Five-Year Plan” period. become a key national project supporting and encouraging development. With China's accession to the WTO, the export volume of Chinese electric bicycles will increase rapidly, and electric bicycles entering Europe and the United States must be equipped with non-polluting batteries.
However, some experts said that environmental pollution caused by lead-acid batteries mainly occurs in the product process.non-standard ion of the company and in the recycling processing links. In the same way, lithium batteries are beneficial to the new energy industry, but they cannot avoid the problem of heavy metal pollution. Lead, arsenic, cadmium, mercury, chromium, etc. can be released into dust and water when processing metal materials. The battery itself is a chemical substance, so it can produce two types of pollution: one is pollution from process effluents of the production project; the other is pollution from batteries after their disposal.
Lithium iron phosphate batteries also have their disadvantages: for example, poor low temperature performance, low setting density of cathode material, and the volume of lithium iron phosphate batteries of the same capacity is greater to that of Lithium-ion batteries such aslithium cobalt oxide, so micro-batteries have no advantage. When used in power batteries, lithium iron phosphate batteries, like other batteries, face battery consistency issues.
8. Comparison of power batteries
At present, the most promising cathode materials for power lithium ion batteries mainly include modified lithium manganate (LiMn2O4) and lithium iron phosphate (LiFePO4) and Lithium-nickel-cobalt manganate ternary materials (Li(Ni,Co,Mn)O2). Due to the lack of cobalt resources, the high cost of nickel and cobalt, and strong price fluctuations, it is generally believed that it is difficult to become the mainstream of power lithium-ion batteries for electric vehicles. However, they can be combined. with spinel manganate, lithium is mixed in a certaindon't beach.
2. Disadvantages of lithium iron phosphate batteries
Whether a material has potential for application development, in addition to paying attention to its advantages, the most important thing is whether the material has any fundamental defects. .
Lithium iron phosphate is now generally chosen as the cathode material to power lithium-ion batteries in China. Market analysts from government, scientific research institutes, enterprises and even securities companies are optimistic about this material and consider it. as a power type lithium-ion battery. The direction of lithium-ion battery development. Analyzing the reasons, there are two main points: First, it is influenced by the direction of research and development in the United States. The American companies Valence and A123 were the first to use lithium iron phosphate as mcathode material of lithium-ion batteries. Second, there is no domestically prepared lithium manganate material with good high-temperature cycling and storage properties that can be used in power lithium-ion batteries. But lithium iron phosphate also existsThe fundamental flaws that can be ignored can be summarized as follows:
1. During the sintering process when preparing lithium iron phosphate, iron oxide is reduced to elemental iron in a high temperature reducing atmosphere. . Elemental iron can cause micro-short circuits in batteries and is the most taboo substance in batteries. This is also the main reason why Japan has not used this material as a cathode material to power lithium-ion batteries.
2. Lithium iron phosphate has some performance defects, such as lowtapping density and low packing density, resulting in low energy density of lithium-ion batteries. Low temperature performance is poor and even nanonization and carbon coating have not solved this problem. When Dr. Don Hillebrand, director of the Center for Energy Storage Systems at Argonne National Laboratory in the United States, spoke about the low-temperature performance of lithium iron phosphate batteries, he used the word "terrible" to describe them. Lithium iron phosphate lithium ion batteries have shown that lithium iron phosphate batteries work well at low temperatures (below 0 ℃) electric vehicles cannot be driven. Although some manufacturers claim that the capacity retention rate of lithium iron phosphate batteries at low temperatures is not bad, it is when the discharge current is small and the discharge cut-off voltage is very fweak. In this situation, the device simply cannot start working.
3. The material preparation cost and battery manufacturing cost are high, the battery efficiency is low, and the consistency is poor. Although nanonization and carbon coating of lithium iron phosphate improve the electrochemical performance of the material, it also leads to other problems, such as reduced energy density, increased synthesis cost, poor processing performance electrodes and strict environmental requirements. Although the chemical elements Li, Fe and P in lithium iron phosphate are abundant and the cost is low, the cost of the prepared lithium iron phosphate product is not low even if the initial costs research and development are eliminated, the cost of the process. material plus the high cost of preparing the batteries will make the cost final per unit of energy storage higher.
4. Product consistency is poor. At present, there is no lithium iron phosphate material factory in China that can solve this problem. From the perspective of material preparation, the synthesis reaction of lithium iron phosphate is a complex multi-phase reaction, including solid phase phosphate, iron oxide and lithium salt, as well as a carbon precursor and a reducing gas phase. In this complex reaction process, it is difficult to ensure the consistency of the reaction.
5. Intellectual property issues. The first patent application for lithium iron phosphate was obtained by FXMITTERMAIER & SOEHNEOHG (DE) on June 25, 1993 and the results of the application were announced on August 19 of the same year. The basic patent of lithium iron phosphate belongs to the University of Texas in the United States, et the carbon coating patent was applied for by a Canadian. These two fundamental patents cannot be circumvented. If patent royalties are included in the cost, the cost of the product will increase further.