The lithium iron phosphate battery is the lithium ion battery used as the anode material. The anode materials of lithium ion batteries mainly include lithium cobalt acid, lithium manganese acid, lithium nickel acid, trimetasone, lithium iron phosphate, etc. Lithium cobalt oxide is the anode material used by most lithium ion batteries. From the principle of materials, lithium iron phosphate is also an embedded and deinlaid process, which is exactly the same as lithium cobalt oxide and lithium manganese acid.
 
1. Introduction
 
The lithium iron phosphate battery is a secondary battery of lithium ion. One of the main USES is for power battery, which has a great advantage over NI-MH and NI- Cd batteries.
 
The charging and discharging efficiency of the lithium iron phosphate battery is high, the discharge efficiency can reach more than 90%, and the lead-acid battery is about 80%.
 
2. Eight advantages
 
Improved security performance
 
Lithium iron phosphate crystals in P - solid O key, difficult to decompose, even in high temperature or overcharge when also won't like cobalt acid lithium structure collapse fever or strong oxidizing substances, thus having good security. A report pointed out that the practice of acupuncture or short circuit experiment found combustion phenomenon in a small number of samples, but no one explosion occurred, and overcharge experiments using several times greatly beyond their discharge voltage of high voltage charging, found that there are explosive. However, its overcharge safety is much better than the normal liquid electrolyte cobalt acid lithium battery.
 
Improvement in longevity
 
The lithium iron phosphate battery is the lithium ion battery used as the anode material.
 
Long life cycle life of lead-acid battery in around 300, the highest is 500 times, and lithium iron phosphate power battery, cycle life reached more than 2000 times, the standard charging rate (5 hours) to use, can reach 2000 times. With the quality of the lead-acid battery is "new half a year, half a year, maintenance, maintenance and half year old", at most 1-1.5 years, while the lithium iron phosphate batteries used under the same conditions, the theory of life will reach 7 ~ 8 years. Combined, the performance ratio is more than four times that of lead-acid batteries. Large current discharge can be charged and discharged with high current 2C. Under the special charger, 1.5c charging can fill the battery in 40 minutes, the starting current can reach 2C, while the lead-acid battery has no such performance.
 
High temperature performance
 
Lithium iron phosphate can reach 350 ℃ to 500 ℃ and the electric peak and cobalt acid lithium manganese acid lithium only at about 200 ℃. Wide range of operating temperature (20 c -- -- - + 75 c), have a high temperature resistant properties of lithium iron phosphate electric peak of up to 350 ℃ to 500 ℃, lithium cobalt and lithium manganese acid and acid only at about 200 ℃.
 
The large capacity
 
It has more capacity than normal battery (lead acid, etc.). The monomer capacity is 5ah-1000ah.
 
Nonmemory effect
 
Rechargeable batteries work at a time when they are constantly in full and uncompleted conditions, and the capacity can quickly fall below the rated capacity. This phenomenon is known as the memory effect. Like nimh and nickel-cadmium battery, there is memory, and no such phenomenon exists in lithium iron phosphate battery. The battery can be used in whatever state it is in, and it is not required to be finished and recharged.
 
Light weight
 
The equivalent size of the lithium iron phosphate battery is 2/3 the volume of lead-acid batteries and a third of the weight of lead-acid batteries.
 
Environmental protection
 
The battery is generally regarded as do not contain any heavy metals and rare metals (nickel metal hydride battery of rare metals), non-toxic (through the SGS certification), no pollution, comply with European RoHS, is absolutely green battery certificate. So the lithium battery is favored by the industry, mainly environmental considerations, so the battery and listed in the "863" during the tenth five-year national high-tech development plan, has become the national key support and encourage the development of project. With China's entry into the WTO, China's exports of electric bicycles will increase rapidly, and electric bicycles entering Europe and the United States have been required to be equipped with pollution-free batteries.
 
However, experts say that the environmental pollution caused by lead-acid batteries mainly occurs in the production process and recycling process of the enterprises. In the same way, lithium batteries are good for the new energy industry, but it also cannot avoid the problem of heavy metal pollution. Metal materials processing lead, arsenic, cadmium, mercury, chromium can be released into dust and water. The battery itself is a chemical, so it is possible to produce two kinds of pollution: one is the waste pollution in the process of production engineering. The second is the battery pollution after scrapping.
 
Lithium iron phosphate battery also has its disadvantages: low temperature performance is poor, for example, tap density is small, the anode materials such as volume of lithium iron phosphate battery capacity than cobalt acid lithium and other lithium ion battery, so don't have an advantage in terms of micro cells. When used in power batteries, iron phosphate batteries, like other batteries, face battery consistency.
 
Comparison of power cells
 
At present, the most promising materials for the dynamic lithium-ion battery are lithium manganate (LiMn2O4), lithium iron phosphate (LiFePO4) and lithium (Ni,Co,Mn) O2. Nickel cobalt manganese acid lithium cobalt ternary material due to the lack of resources and nickel and cobalt into high price fluctuation and large, is generally believed that it's hard to become the electric car with the mainstream of power type lithium ion battery, but can and spinel lithium manganese acid mixed in a certain range.
 
Industry application
 
The aluminum foil coating has brought technological innovation and industrial improvement to the lithium industry.
 
Improve the performance of lithium electric products and improve the discharge ratio.
 
As domestic battery manufacturers have increased their demand for battery performance, they generally identify with new energy battery materials: conductive materials, conductive coating aluminum foil and copper foil.
 
Its advantage lies in: in the treatment of battery materials, often have high rate charge and discharge performance is good, bigger specific capacity, but the cycle stability is poorer, attenuation serious wait for a reason, have to do choose to give up.
 
This is a fantastic coating that will improve the performance of the battery into a new era.
 
The conductive coating is composed of dispersed nano-conductive graphite coated particles. It provides excellent static and conductive properties and is a protective layer of energy absorption. It also provides good protection against protection. The coating is water-based and solvent and can be used in aluminum, copper, stainless steel, aluminum and titanium plates.
 
The performance of the carbon coating on the lithium battery has the following improvements:
 
1. Reduce the internal resistance of the battery and suppress the increase of dynamic internal resistance in the cycle of charge and discharge;
 
2. Significantly improve the consistency of the battery pack and reduce the cost of the battery pack;
 
3. Improve the adhesion of the active materials and the collected fluids, and reduce the production cost of the poles;
 
4. Reduce polarization, improve multiplier performance and reduce thermal effects;
 
5. Prevent the corrosion of the liquid from electrolyte;
 
6. Comprehensive factors to extend battery life;
 
7. Coating thickness: 1 ~ 3 mu m of conventional single surface thickness.
 
Japan and South Korea in recent years, the main development in modification and nickel cobalt manganese acid lithium manganese acid lithium ternary material as the anode material of power type lithium ion battery, such as Toyota and Panasonic, Hitachi, Panasonic EV energy of a joint venture company, new kobe motor, NEC, SONY, sanyo, samsung, LG, etc. The main development of the anode materials for lithium iron phosphate power type lithium ion battery, such as A123 systems, Valence, but the major automobile manufacturers in the PHEV and EV is the choice of manganese base power type lithium ion battery cathode material system, and it is said that the A123 company in the field of consideration into manganese acid lithium materials, and Germany and other European countries mainly adopt the battery company cooperation with other countries to develop electric vehicles, such as Daimler and French Saft alliance, Volkswagen of Germany and Japan sanyo cooperation agreement, etc. Germany's Volkswagen and France's Renault are also developing and producing dynamic lithium-ion batteries, backed by their own governments.
 
3. The shortcomings
 
Whether a material has the potential of application development, besides focusing on its merits, it is more important whether the material has fundamental defects.
 
Domestic now generally choose the lithium iron phosphate as power type lithium ion battery cathode material, from the government, scientific research institutions, enterprises, and even markets such as securities analysts are bullish on this material, as the development direction of power type lithium ion battery. There are two main reasons for this analysis: firstly, it is influenced by the us research and development direction, and the American company and A123 company first used lithium iron phosphate as the anode material for lithium ion batteries. Secondly, there has been no preparation of lithium manganese acid with high temperature cycling and storage performance for power lithium ion batteries. However, there are fundamental flaws in lithium iron phosphate that can not be ignored.
 
1. In the sintering process during the preparation of lithium iron phosphate, iron oxide has the possibility of being reduced to single iron in the atmosphere of high temperature reducing. A single iron can cause a microcircuit of the battery, which is the most taboo substance in the battery. This is also the main reason why Japan has not used the material as the anode material for lithium ion batteries.
 
2. There are some defects in the performance of lithium iron phosphate, such as the low density and compaction density, and the low energy density of the lithium ion battery. The low temperature performance is poor, and even the nano - and carbon - coated coating does not solve this problem. Argonne national laboratory, director of the center for energy storage systems Don Hillebrand Dr When it comes to the lithium iron phosphate battery performance at low temperature with terrible to describe, their type of lithium iron phosphate lithium ion battery test results show that shows that the lithium iron phosphate battery at low temperature (below 0 ℃) could not make the electric car. Although some manufacturers claim that lithium iron phosphate batteries have a good capacity at low temperatures, that is when the discharge current is small and the discharge cutoff voltage is low. In this situation, the device simply cannot start work.
3. The preparation cost of materials and the manufacture cost of the battery are higher, and the battery yield is low and the consistency is poor. Lithium iron phosphate nano and carbon coated despite the electrochemical properties of the material, but also brought other problems, such as lower energy density and the rising cost of synthesis, electrode processing performance is poor and demanding to the environment and other problems. Despite the lithium iron phosphate chemical elements in the Li, Fe and P is very rich, and a low cost, but could be prepared for the lithium iron phosphate product cost is not low, even with previous research and development costs, the process of the material cost and high cost of batteries, will make the final unit cost of energy storage battery is higher.
 
4. Poor product consistency. At present, there is no iron phosphate material factory in China to solve this problem. From the Angle of material preparation, the synthetic reaction of the lithium iron phosphate is a complex multiphase reaction, has a solid phosphate, iron oxide and lithium salt, plus the precursor and carbon reduction aerosols. In this complex reaction, it is difficult to ensure the consistency of the reaction.
 
5. Intellectual property issues. The earliest application for a lithium iron phosphate patent was obtained by F X MITTERMAIER & SOEHNE OHG (DE) on 25 June 1993, and the application results were announced on 19 August of the same year. The basic patent for lithium iron phosphate is owned by the university of Texas, and the carbon envelope patent is applied by the Canadian. These two basic patents cannot go round, and the cost of the product will be further increased if the royalties are calculated in the cost.
 
In addition, from the experience of developing and producing lithium-ion batteries, Japan is the first country to commercialize lithium-ion batteries and has been occupying the market of high-end lithium-ion batteries. The us is leading in some basic research, but so far it has not produced a large lithium-ion battery maker. Therefore, it is more reasonable for Japan to choose lithium manganese acid as the anode material for the dynamic lithium ion battery. Even in the United States, the use of lithium iron phosphate and lithium manganese dioxide as the anode materials for lithium ion batteries are half of the same, and the federal government supports both systems. In view of the above problems of lithium iron phosphate, it is difficult to be used as the anode material of power lithium-ion battery in the field of new energy automobile. If you can solve the manganese acid lithium storage high temperature cycle and difficult problems of poor performance, with its advantage of low cost and high performance ratio in the application of power type lithium ion battery will have great potential.
 
4.The full name of the working principle and characteristics of the lithium iron phosphate battery is lithium iron phosphate battery. The name is too long, which is called lithium iron phosphate battery. Since its performance is particularly suitable for dynamic applications, the word "power" is added to the name, which is the lithium iron phosphate power battery. Others call it the "lithium iron (LiFe) power cell."
signification
 
In the metal trading market, cobalt (Co) is the most expensive and has few deposits, nickel (Ni), Mn (Mn) is cheaper, and iron (Fe) is the cheapest. The price of the positive material is also in line with the prices of these metals. Therefore, lithium ion batteries made of LiFePO4 positive materials should be the cheapest. Another feature of it is pollution.
 
As the requirements of the rechargeable batteries are: high capacity, high output voltage, good charge and discharge cycle performance, stable output voltage, large current charge and discharge, electrochemical stability, use of safety (did not charge, discharge and short circuit caused by improper operation, such as the combustion or explosion), wide working temperature range, non-toxic or less poison, no pollution to the environment. Adopting LiFePO4 as anode of lithium iron phosphate batteries are good on these performance requirements, particularly in large discharge rate discharge (5 ~ 10 c discharge), stable discharge voltage, security, not burning, not an explosion, and life (cycles), on the environment pollution-free, it is the best, is currently the best large current output power battery.
 
Structure and working principle
 
LiFePO4 battery internal is the LiFePO4 of olivine structure as the positive pole of the battery, connected to the battery positive electrode by aluminum foil and polymer is among the diaphragm, which separates the positive and negative, but lithium ion Li + and electronic e - cannot pass, right is composed of carbon (graphite) battery cathode, the copper foil and negative connection of the battery. Between the upper and lower sides of the battery are the electrolytes of the battery, sealed by a metal enclosure.
 
When the LiFePO4 battery is charged, the lithium ion in the positive electrode is transferred to the negative pole through the polymer diaphragm. In the discharge process, the anode lithium ion is transferred to the positive pole through the diaphragm. The lithium ion battery is named after the lithium ions move back and forth in charge and discharge.
 
The main performance
 
The nominal voltage of the LiFePO4 battery is 3.2 V, the termination voltage is 3.6 V, and the termination voltage is 2.0 V. Due to the differences in the quality and process of positive, negative electrode materials and electrolyte materials used by various manufacturers, there will be some differences in performance. For example, the same model (the same standard battery) has a larger battery capacity (10% ~ 20%).
 
It is important to note that there are some differences in the performance parameters of the lithium iron phosphate power battery produced by different factories. In addition, some battery properties are not included, such as battery resistance, self-discharge rate, charging and discharging temperature, etc.
 
There are big differences in the capacity of the lithium iron phosphate power battery, which can be divided into three categories: small zero to several milliamps, medium dozens of milliampere hours, large hundreds of milliampere. There are some differences in the similar parameters of different types of batteries. At present, it is applied to the small standard cylindrical encapsulated iron phosphate battery, which has a diameter of 18mm and a height of 650mm (18650).
 
Discharge to zero voltage test
 
Using STL18650 (1100mAh), the lithium iron phosphate power battery was discharged to zero voltage test. Test conditions: the STL18650 battery of 1100mAh was filled with 0.5C charging rate, and then the battery voltage of 1.0C was discharged to the battery voltage of 0C. There are two groups of cells that will be placed on 0V: one for 7 days and the other for 30 days. When the storage is due, the charging rate of 0.5C is full, and then the 1.0C discharge is used. Finally compare the difference between the two zero voltage storage periods.
 
The result of the test is that the zero voltage storage is not leaking after 7 days, the performance is good, the capacity is 100%; After 30 days of storage, no leakage, good performance and 98% capacity. After 30 days of storage, the battery can be charged and discharged three times, and the capacity is restored to 100%.
 
The test showed that the battery had been discharged (even to 0V) and stored for a certain time, and the battery did not leak or damage. This is a characteristic that other types of lithium-ion batteries do not.
 
The characteristics of lithium iron phosphate battery
 
Through the above introduction, LiFePO4 battery can induce the following characteristics.
 
High efficiency output: the standard discharge is 2 ~ 5C, the continuous high current discharge can reach 10C, the instantaneous pulse discharge (10S) can reach 20C;
 
Good performance at high temperature, external temperature 65 ℃ when the internal temperature is as high as 95 ℃, at the end of the battery discharge temperature can reach 160 ℃, the structure of the battery safe and in good condition;
 
Even if the battery is damaged inside or outside, the battery does not burn, not explode, and the safety is the best.
 
Excellent cycle life, with 500 cycles, its discharge capacity is still greater than 95%;
 
There is no damage to discharge to zero volts;
 
Quick charge;
 
Low cost;
 
No pollution to the environment.
 
Application of lithium iron phosphate power battery
 
Due to the above characteristics, the lithium iron phosphate battery has been widely used in the production of various kinds of batteries. Its main applications are:
 
Large electric vehicles: buses, electric cars, sightseeing buses and hybrid vehicles;
 
Light electric vehicles: electric bicycles, golf carts, small flat-panel electric vehicles, forklifts, clean cars, electric wheelchairs, etc.
 
Electric tools: electric drill, electric saw, mower, etc.
 
Remote-controlled cars, boats, planes and other toys;
 
Energy storage equipment for solar and wind power;
 
UPS and emergency lights, warning lights and lamp (safety is best);
 
The replacement of 3V's disposable lithium batteries and 9V nickel-cadmium or nickel-nickel rechargeable batteries (the same size);
 
Small medical equipment and portable instruments.
 
Here's an example of an application of a lithium iron phosphate battery instead of a lead-acid battery. Using 36V/10Ah(360Wh) lead-acid batteries, the weight of 12kg is about 50km on a single charge and about 100 charges, about 1 year. If using lithium iron phosphate power battery, use the same 360 wh energy (12 ah battery series of 10), its weight about 4 kg, can walk 80 km or so a charge, charge number up to 1000 times, the service life of up to 3 ~ 5 years. While the price of lithium iron phosphate is much higher than the lead-acid battery, the overall economic effect is better with the iron-phosphate lithium-ion power battery, which is lighter in use.
 
5. Battery performance
 
Lithium ion power battery depends mainly on the performance of anode materials, lithium iron phosphate as a lithium battery materials has been appeared in recent years, domestic developed large-capacity lithium iron phosphate batteries are in July 2005. Its safety performance and cycle life are not comparable to other materials, which are also the most important technical indicators of power cells. The circulation life of 1C is 2000 times. Single cell overcharging pressure 30V does not burn, puncture does not explode. The lithium iron phosphate anode material makes a large capacity lithium ion battery is easier to use in series. In order to meet the needs of frequent charging and discharging of electric vehicles. It has the advantages of non-toxic, pollution-free, safe performance, wide source of raw materials, cheap price and long life. It is the ideal positive electrode material for a new generation of lithium-ion batteries.
 
This project belongs to the development of functional energy materials in high and new technology projects, which is the focus of national "863" program, "973" plan and "eleventh five-year" high-tech industrial development planning.
 
Lithium ion battery is highly advantageous in its safety and cycle life, which is one of the most important technical indexes of power battery. 1C filling cycle life can be achieved 2000 times, puncture does not explode, it is not easy to burn and explode when overcharged. The lithium iron phosphate material makes a large capacity of lithium ion batteries and is easier to use in series.
 
6. Scientific research application
 
Lithium iron phosphate battery
 
Progress recently, the new type of battery, is expected to replace traditional lithium battery report, let us see the hope of the phone, the tablet has a longer battery life, but it's a pity that most of all stay in the laboratory research stage, when or even whether large-scale commercial has to say.
In Deboch TEC. GmbH, lithium iron phosphate battery technology in the white paper released after using composite nanomaterials, single section 32650 specifications (32 mm diameter/length is 65 mm) batteries can ascend to 6000 mah, energy density and the current industry 32650 specifications of the specifications of the single section 5000 mah, compared to the same volume increased 1000 mah, which is as much as 20%, section 1 can give the iPhone 4 s mobile phone recharged almost four times.
 
Even more exciting is that low range on a single charge and discharge conditions used, the battery in the recycling of up to 3000 times, power remained at about 80%, while the common lithium battery charging circuit about 500 times the virtue. According to every three days of charging and discharging, it can be used continuously for 24 years, which is a long-lived battery.
 
This new type of battery technology can be widely used in portable mobile power supply, small UPS, a variety of equipment such as laptop battery, car battery, and for different using environment, Deboch TEC. GmbH also according to the difference in the number of times a charging circuit using different batteries color: military level oriented for gold, cycle times to 3000 times; The use of blue and 2500 in the civil automobile industry; Green and 2000 applications for small portable mobile devices.