The lifepo4 battery refers to a lithium ion battery using lithium iron phosphate as a positive electrode material. The positive electrode materials of lithium ion batteries mainly include lithium cobaltate, lithium manganate, lithium nickelate, ternary materials, lithium iron phosphate and the like. Among them, lithium cobaltate is the positive electrode material used in most lithium ion batteries. In principle, lithium iron phosphate is also an embedding/deintercalation process, which is identical to lithium cobaltate and lithium manganate.
The lifepo4 battery belongs to lithium ion secondary battery, and one main purpose is to use it as a power battery, which has great advantages over NI-MH and Ni-Cd batteries.
The lifepo4 battery has high charge and discharge efficiency, and the charge and discharge efficiency can reach over 90% under the condition of discharge. The lead-acid battery is about 80%.
The P-O bond in the lithium iron phosphate crystal is stable and difficult to decompose, and does not collapse or heat like a lithium cobaltate or forms a strong oxidizing substance even at a high temperature or overcharge, and thus has good safety. It has been reported that in the actual operation, a small part of the sample was found to have a burning phenomenon in the acupuncture or short circuit test, but there was no explosion event. 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 was still Explosion phenomenon. Even so, its overcharge safety has been greatly improved compared to the ordinary liquid electrolyte lithium cobalt oxide battery.
The lifepo4 battery refers to a lithium ion battery using lithium iron phosphate as a positive electrode material.
The long-life lead-acid battery has a cycle life of about 300 times, and the highest is 500 times. The lifepo4 power battery has cycle life of more than 2,000 times, and the standard charge (5 hour rate) can be used up to 2000 times. The same quality lead-acid battery is "new half year, old half year, maintenance and maintenance for half a year", up to 1~1.5 years, while lifepo4 battery is used under the same conditions, the theoretical life will reach 7~8 years. Considering comprehensively, the performance price ratio is theoretically more than four times that of lead-acid batteries. High-current discharge can be quickly charged and discharged with high current 2C. Under the special charger, the battery can be fully charged within 1.5 minutes of 1.5C charging, and the starting current can reach 2C, but the lead-acid battery has no such performance.
The peak temperature of lithium iron phosphate can reach 350 ° C -500 ° C while lithium manganate and lithium cobaltate are only around 200 ° C. Wide operating temperature range (-20C--+75C), high temperature resistance, lithium iron phosphate electric heating peak up to 350 ° C -500 ° C and lithium manganate and lithium cobalt oxide only around 200 ° C.
It has larger capacity than ordinary batteries (lead acid battery, etc.). 5AH-1000AH (single)
Rechargeable batteries work conditions that are often not fully discharged, and the capacity will quickly fall below the rated capacity. This phenomenon is called the memory effect. Like nickel-metal hydride and nickel-cadmium batteries can be remembered, but lithium iron phosphate batteries do not have this phenomenon. No matter what state the battery is in, it can be used with charging, without having to discharge.
The volume of the lifepo4 battery of the same specification capacity is 2/3 of the volume of the lead-acid battery, and the weight is 1/3 of the lead-acid battery.
The battery is generally considered to be free of any heavy metals and rare metals (Ni-MH batteries require rare metals), non-toxic (SGS certified), non-polluting, in line with European RoHS regulations, is an absolute green battery certificate. Therefore, the reason why lithium batteries are favored by the industry is mainly environmental considerations. Therefore, the battery has been included in the “863” national high-tech development plan during the “Tenth Five-Year Plan” period, and has become a national key support and encouragement development project. With China's accession to the WTO, the export volume of electric bicycles in China will increase rapidly, and electric bicycles entering Europe and the United States have been required to be equipped with non-polluting batteries.
However, some experts said that the environmental pollution caused by lead-acid batteries mainly occurred in the production process and recycling process of enterprises. In the same way, lithium batteries are good in the new energy industry, but it can not avoid the problem of heavy metal pollution. Lead, arsenic, cadmium, mercury, chromium, etc. may be released into dust and water during processing of metal materials. The battery itself is a chemical substance, so there may be two kinds of pollution: one is the process waste pollution in the production process; the other is the battery pollution after the scrap.
Lithium iron phosphate batteries also have their disadvantages: for example, poor low temperature performance, low tap density of positive electrode materials, and the capacity of lithium iron phosphate batteries of equal capacity are larger than lithium ion batteries such as lithium cobalt oxide, so there is no advantage in micro batteries. When used in a power battery, a lithium iron phosphate battery, like other batteries, needs to face battery consistency problems.
At present, the most promising cathode materials for dynamic lithium-ion batteries are modified lithium manganate (LiMn2O4), lithium iron phosphate (LiFePO4) and lithium nickel cobalt manganese oxide (Li(Ni, Co, Mn)O2). material. Nickel-cobalt-manganese hydride ternary materials are generally considered to be difficult to become the mainstream of power-type lithium-ion batteries for electric vehicles due to the lack of cobalt resources and high nickel and cobalt, and high price fluctuations, but can be related to spinel manganate. Lithium is mixed in a certain range.
3.disadvantages
Whether a kind of material has potential for application development, in addition to focusing on its advantages, is more critical whether the material has fundamental defects.
Lithium iron phosphate is widely used as a positive electrode material for power lithium-ion batteries in China. Market analysts such as government, scientific research institutions, enterprises and even securities companies are optimistic about this material as the development direction of power lithium-ion batteries. Analysis of the reasons, mainly have the following two points: First, the impact of the US research and development direction, the United States Valence and A123 company first used lithium iron phosphate as the cathode material for lithium-ion batteries. Secondly, there has been no preparation of lithium manganate materials with good high temperature cycle and storage properties for use in power lithium-ion batteries. However, lithium iron phosphate also has fundamental defects that cannot be ignored. The main points are as follows:
In addition, from the experience of research and development and production of lithium-ion batteries, Japan is the first commercialized country of lithium-ion batteries, and has always occupied the high-end lithium-ion battery market. Although the United States leads in some basic research, there is still no large-scale lithium-ion battery manufacturer. Therefore, it is more reasonable for Japan to choose modified lithium manganate as a positive electrode material for a power-type lithium ion battery. Even in the United States, lithium iron phosphate and lithium manganate are used as the cathode materials for power-type lithium-ion batteries, and the federal government also supports the development of these two systems. In view of the above problems of lithium iron phosphate, it is difficult to be widely used as a positive electrode material for a power type lithium ion battery in fields such as new energy vehicles. If it can solve the problem of high temperature cycle and poor storage performance of lithium manganate, with its advantages of low cost and high rate performance, it will have great potential in the application of power lithium-ion batteries.
The performance of lithium-ion battery depends mainly on the positive and negative materials. Lithium iron phosphate is a lithium battery material that has only appeared in recent years. The large-capacity lithium iron phosphate battery developed in China in July 2005. Its safety performance and cycle life are incomparable to other materials, which are the most important technical indicators of power batteries. 1C charge and discharge cycle life of 2000 times. Single cell battery overcharge voltage 30V does not burn, puncture does not explode. Lithium iron phosphate cathode materials make large-capacity lithium-ion batteries easier to use in series. To meet the needs of frequent charging and discharging of electric vehicles. It has the advantages of non-toxic, non-polluting, good safety performance, wide source of raw materials, low price and long service life. It is an ideal cathode material for a new generation of lithium ion batteries.
This project belongs to the development of functional energy materials in high-tech projects, and is the key area supported by the national “863” plan, “973” plan and “Eleventh Five-Year” high-tech industry development plan.
The positive electrode of lithium-ion battery is lithium iron phosphate material, which has great advantages in safety performance and cycle life. These are also one of the most important technical indicators of power battery. 1C charge and discharge cycle life can be achieved 2000 times, puncture does not explode, it is not easy to burn and explode when overcharged. Lithium iron phosphate cathode materials make large-capacity lithium-ion batteries easier to use in series.
Through the above introduction, the LiFePO4 battery can be summarized as follows.
High efficiency output: standard discharge is 2~5C, continuous high current discharge can reach 10C, instantaneous pulse discharge (10S) can reach 20C;
Good performance at high temperature: the internal temperature is as high as 95 °C when the external temperature is 65 °C, and the temperature is up to 160 °C when the battery is discharged. The structure of the battery is safe and intact;
Even if the inside or outside of the battery is damaged, the battery does not burn, does not explode, and has the best safety;
Excellent cycle life, after 500 cycles, its discharge capacity is still greater than 95%;
No damage to zero volts after overdischarge;
Fast charging;
low cost;
No pollution to the environment.
Application of lithium iron phosphate power battery
Since lithium iron phosphate power batteries have the above characteristics and produce batteries of various capacities, they are quickly widely used. Its main application areas are:
Large electric vehicles: buses, electric cars, scenic tour buses and hybrid vehicles;
Light electric vehicles: electric bicycles, golf carts, small flat battery cars, forklifts, cleaning cars, electric wheelchairs, etc.;
Power tools: electric drills, chainsaws, lawn mowers, etc.;
Remote control of cars, boats, airplanes and other toys;
Energy storage equipment for solar and wind power generation;
UPS and emergency lights, warning lights and miner's lamps (safest);
Replace the 3V disposable lithium battery in the camera and the 9V nickel-cadmium or nickel-hydrogen rechargeable battery (the same size);
Small medical equipment and portable instruments.
Here is an application example of replacing a lead-acid battery with a lifepo4 power battery. It adopts 36V/10Ah (360Wh) lead-acid battery, its weight is 12kg, it can walk about 50km with a single charge, the charging frequency is about 100 times, and the use time is about 1 year. If the lifepo4 power battery is used, the same 360Wh energy (12 10Ah batteries are connected in series), the weight is about 4kg, the charging can walk about 80km, the charging frequency can reach 1000 times, and the service life can reach 3 to 5 years. Although the price of lifepo4 battery is much higher than that of lead-acid batteries, the overall economic effect is better with lifepo4 battery and lighter in use.
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