iron phosphate lithium battery, lithium iron phosphate refers to as a positive electrode material for lithium ion batteries. The positive electrode material of lithium ion battery of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, ternary materials, lithium iron phosphate. Wherein the lithium cobaltate is a lithium ion battery positive electrode material used in the vast majority.
1. Eight advantages of lithium iron phosphate
Improve
Safety Performance
crystal of lithium iron phosphate-PO bond in a solid, difficult to decompose, even at a high temperature or overcharge will not as lithium cobalt oxide as the structure collapses or heat to form a strong oxidizing agent, it has a good security. There are reports that, in actual operation needle or short experiments found that small sample of burning phenomenon occurred, but one case of explosion occurs, and the experiments used far beyond the self-discharge charge high voltage charging voltage times, still found explosions. Nevertheless, its overcharge safety than the ordinary liquid electrolyte lithium cobalt oxide batteries, is much improved.
improved lifetime
refers to lithium iron phosphate lithium iron phosphate as a cathode material for lithium ion batteries.
long cycle life in lead-acid battery life of about 300, the maximum is500 iron phosphate lithium battery, lithium iron phosphate battery, the cycle life of more than 2,000 times, the standard charge (5 hour rate) used, up to 2000 times. With the quality of lead-acid batteries is the “new six months, six months old, Maintenance and six months”, most will be from 1 to 1.5 years, while the lithium iron phosphate used under the same conditions, the theoretical life expectancy will reach 7 to 8 years. Taken together, the cost performance is more than four times theoretically lead-acid batteries. Large current discharge high current 2C fast charge and discharge, at a dedicated charger, 1.5C charging the battery in 40 minutes to make full, the starting current of up to 2C, whereas no such lead-acid battery performance. Good
The high temperature performance
lithium iron phosphate peak heating up 350 ℃ -500 ℃ and lithium manganate and lithium cobaltate only about 200 ℃. Wide temperature range (-20C – + 75C), lithium iron phosphate peak heating temperature resistance up to 350 ℃ -500 ℃ and lithium manganate and lithium cobaltate only about 200 ℃.
mass
has a larger capacity than ordinary batteries (lead-acid, etc.). 5AH-1000AH (monomer)
no memory effect
Rechargeable batteries always in full working under conditions of complete hold, the capacity is lower than the nominal capacity rapidly, a phenomenon called memory effect. Such as nickel hydrogen, nickel cadmium batteries memory exists, no such phenomenon lithium iron phosphate, regardless of what state the cell, can recharge it with, without first recharge is done.
light weight
Lithium iron phosphate volumetric size equal volume of lead-acid battery capacity is 2/3, 1/3 the weight of lead-acid batteries.
environmental protection
The battery is generally considered to be free of any heavy metals and rare metals (nickel-metal hydride batteries to be rare), non-toxic (SGS certification through), non-polluting, in line with European RoHS regulations as an absolute green battery card. So why lithium batteries are optimistic about the industry, mainly environmental considerations, so the battery and included in the “863” national high-tech development plan for the period “15”, a project supported by the state and encourage development. With China’s accession to WTO, Chinese exports of electric bicycles will increase rapidly, and enter the European electric bike has been with the requirements of pollution-free batteries.
But some experts said the environmental pollution caused by lead-acid batteries, mainly in the business of non-standard production processes and recycling sectors. Similarly, lithium batteries are not new energy industryWrong, but it can not avoid the problem of heavy metal pollution. Metal materials processing lead, arsenic, cadmium, mercury, chromium and the like are likely to be released into the water and dust. Battery itself is a chemical substance, it is possible pollution will have two: First, the production process of fecal contamination in the project; the second is battery pollution later scrapped.
Lithium iron phosphate has its drawbacks: for example, the difference between low temperature performance, small tap density of the positive electrode material and volume capacity of lithium iron phosphate is larger than the lithium cobalt oxide, lithium-ion battery, it is not advantageous in terms of microbattery . And when used in motive power batteries, lithium iron phosphate batteries and other batteries, battery consistency to face the problem.
Comparative battery power
applied to the most promising power lithium-ion battery cathode materials are modified lithium manganate (LiMn2O4), lithium iron phosphate (LiFePO4) and lithium nickel cobalt manganese oxide (Li ( ni, Co, Mn) O2) ternary material. Lithium nickel cobalt manganese-cobalt ternary material due to lack of resources and the nickel, cobalt, into high and volatile prices and other reasons, electric vehicle generally considered difficult to become the mainstream of the power type lithium ion battery, but the acid and manganese spinel lithium complex used within a certain range.
Industry Applications
carbon coated aluminum foil for the lithium industry to bring technological innovation and industrial upgrading
improve the performance of lithium-powered products, improve discharge rate
With the increasing domestic battery manufacturers battery performance requirements, general domestic Identification of new energy battery materials: conductive material amp; conductive coating aluminum / copper foil.
The advantages: when dealing with cell material, often have a high rate discharge performance, larger than the capacity, but poor cycle stability, decay is more serious reasons, had to make trade-offs to give up.
Applications, golf bag in a battery pack
This is a magical coating, will improve the performance of the battery, into a new era.
electrically conductive coating is electrically conductive nanoparticles were dispersed particles composed of graphite coating. It can provide excellent static conductivity, energy absorbing layer is a protective layer. It can also provide good cover protective properties. There aqueous coating and solvent resistance, can be applied in an aluminum, copper, stainless steel, aluminum and titanium bipolar plate.
carbon coating is coated on the performance of lithium batteries bring the lift
1 to reduce the internal resistance of the battery, the dynamic resistance suppressing increase in the charge-discharge cycle; 2. significantly improve the consistency of the battery pack and reduce powerThis pool composition; 3. increase adhesion of the active material and the bonding of the current collector, reduced manufacturing costs pole piece; 4. reduced polarization, improving rate properties reduce thermal effects; 5. prevent electrolytic corrosion of the current collector; 6 comprehensive factor thereby extending battery life. 7. Coating thickness: thickness of a conventional single-sided 1 ~ 3μm.
In recent years, mainly in Japan and Korea develop lithium-ion battery to power modified lithium manganate and lithium nickel cobalt manganese ternary materials for the positive electrode material, such as Panasonic Toyota and Panasonic EV Energy, a joint venture company, Hitachi, Sony, Shin-Kobe Electric, NEC, Sanyo, Samsung and LG and so on. U.S. mainly developed to lithium iron phosphate cathode material of the power type lithium ion battery, such as A123 Systems, Valence company, but the major U.S. automobile manufacturers in which the PHEV an EV chose manganese-based cathode material system power type lithium ion battery, It is said that the United States and the A123 Inc. is considering to enter the field of lithium manganese oxide materials, while Germany and other European countries and other countries mainly take the form of a battery electric vehicle development companies, such as Daimler-Benz and France, Saft Union, Germany’s Volkswagen and Japan’s Sanyo cooperation agreement Wait. At present Germany’s Volkswagen and France’s Renault, with the support of their governments are also being developed and the production of power lithium-ion battery.
2. Disadvantage of lithium iron phosphate
whether a material has potential applications, in addition to the advantage of interest, the more critical is whether the material is fundamentally flawed. China is now a popular choice for lithium iron phosphate cathode material for lithium-ion batteries as the power from government, scienceResearch institutions, businesses and even securities companies and other market analysts are optimistic about the material, the direction of its development as a power type lithium ion battery. Analysis of the reasons, mainly the following two points: First, the United States is affected by the direction of research and development, the United States Valence and A123 first company to make use of lithium iron phosphate lithium-ion battery cathode material. Followed by a country has not been prepared for lithium manganate material having good high-temperature cycle performance and storage power of the lithium ion battery. However, the presence of lithium iron phosphate can not be ignored fundamentally flawed, summed up in the following points: 1, when the sintering process for preparing lithium iron phosphate, the presence of iron oxide is reduced to elemental iron may be a reducing atmosphere at a high temperature sex. Elemental iron may cause micro-short circuit of the battery, the battery is the most taboo substance. This is the main reason for this has not Japan as a power type lithium ion battery positive electrode material of the material. 2, the lithium iron phosphate on the performance of some drawbacks, such as the tap density and compact density is low, resulting in a lower energy density of the lithium ion battery. Poor low temperature performance, even if it is carbon-coated nano-technology and does not solve the problem. Dr. Don Hillebrand, director of Argonne National Laboratory, the US central storage system comes lithium iron phosphate battery low temperature performance, he used to describe the terrible, their lithium-ion battery test results show shows that type lithium iron phosphate lithium iron phosphate at low temperature under (hereinafter 0 ℃) can not make electric cars. Although there are manufacturers claim that the lithium iron phosphate batteries at a low temperature capacity retention rate is still good, but that the discharge current is small and the discharge cutoff voltage low situation. In this situation, the device simply can not start work. 3, production cost and manufacturing cost of battery materials, battery low yield, poor consistency. Lithium iron phosphate coated with carbon and nanometer despite improved electrochemical performance, but also bring other problems, such as reduction in energy density, improves defective synthesis cost, performance and electrode processing problems demanding environmental requirements. Although the chemical elements in the lithium iron phosphate Li, Fe and P is very rich, lower cost, but the cost of producing lithium iron phosphate product is not a low, pre-development costs even remove, the material cost of the process as well as higher the cost of preparing a battery, will power storage unit such that the final cost is high. 4, product consistency is poor. Currently no plant a lithium iron phosphate material can solve this problem. From the perspective of preparation of materials, lithium iron phosphateSynthesis is a complex multi-phase reaction, solid phase phosphate, iron oxide, and lithium salts, plus a carbon precursor and a reducing gas. In this complex reaction process, it is difficult to ensure consistency of response.
5, intellectual property issues. The first related to lithium iron phosphate patent applications in 1993, June 25 amp by the F X MITTERMAIER; SOEHNE OHG (DE) is obtained, and in the same year on August 19 announced the result of the application. Basic patent lithium iron phosphate are all University of Texas, and the carbon coating patents have been applied for Canadians. The two basic patent is not to go around, and if the cost is calculated on royalties, then the cost of the product will be further enhanced.
In addition, R & D and production of lithium-ion batteries experience point of view, Japan is the first commercial lithium ion battery in the country, and has been dominated by high-end lithium-ion battery market. Although the United States on the basis of a number of leading research, but so far there is not a large lithium-ion battery manufacturers. Thus, Japanese selected modified lithium manganate as the power type lithium ion battery positive electrode material have their sense. Even in the United States, the use of lithium iron phosphate and the lithium manganate as manufacturers power type lithium ion battery positive electrode material are each half of the federal government is to support development of both systems. In view of the above problems of the lithium iron phosphate is present, it is difficult as a power type lithium ion battery positive electrode material widely used in the field of new energy vehicles. If the difference between the high-temperature cycle can solve problems with storage performance of lithium manganese oxide present, by virtue of its advantages of low cost and high rate performance, application of the power type lithium ion battery will have a great potential.
3. The working principle of lithium iron phosphate
Full name of lithium iron phosphate Lithium iron phosphate is a lithium ion battery, referred to as the iron phosphate lithium battery. Because of its properties particularly suitable for application force aspect, the addition of “power” in the name of the word, namely iron phosphate lithium battery. It was also referred to as “lithium iron (of LiFe) battery.”
Value
Metal Exchange, cobalt (Co) the most expensive, and the small amount of memory, a nickel (Ni), manganese (Mn) less expensive, and iron (Fe) is the cheapest. Price is also consistent with the cathode material market price of these metals. Therefore, LiFePO4 cathode material made of lithium-ion batteries are the most expensive. Another feature is its pollution to the environment.
As the rechargeable battery is required: high capacity, high output voltage, excellent charge and discharge cycle characteristics, the output voltage is stable, large current charge and discharge, electrochemically stable performance, safety in use (not due to overcharge, discharge and short circuit caused by improper operation of fire or explosion), a wide operating temperature range, non-toxic or less toxic pollution to the environment. Using LiFePO4 as the positive electrode of lithium iron phosphate are good in these performance requirements, in particular the discharge (5 ~ 10C discharge) in the large discharge rate, the discharge voltage is stable, safety (no combustion, explosion), the number of life (cycles ), pollution of the environment, it is the best, is the best high-current output power of the battery.
structure and working principle
of the internal structure of LiFePO4 battery. LiFePO4 left is an olivine structure as a positive electrode of a battery, a battery connected to the positive and aluminum foil, the intermediate membrane is a polymer, it is spaced apart from the positive and negative, but lithium ions Li + and electrons e- can not be on the right by carbon (graphite) to form a battery negative electrode, a copper foil with a negative electrode connected to a battery. Battery electrolyte between the upper and lower end of the battery, the battery housing sealed by a metal package.
LiFePO4 internal cell structure
LiFePO4 during charging of the battery, the positive electrode of lithium ion Li + to the anode migrate through the polymer membrane; during discharge, lithium ions in the negative electrode to the positive electrode of Li + to migrate through the membrane. A lithium ion battery is the result of migration of lithium ions during charging and discharging to and fro named.
The main performance
of LiFePO4 battery nominal voltage is 3.2V, the termination voltage is 3.6V, the discharge terminationVoltage is 2.0V. Due to the different positive and negative electrode material, electrolyte material quality and process each manufacturer uses which will be some differences in performance. For example, the same model (same package, standard battery), the battery capacity are very different (~ 10 Percentage 20 percent).
The main iron phosphate lithium battery properties are shown in Table 1. For comparison with other rechargeable batteries, but also other types of rechargeable batteries are listed in the performance table. It is noted that herein, the production of different plants iron phosphate lithium battery will be some differences in performance parameters; Further, some are not included in the battery performance, such as the internal resistance of the battery, self-discharge rate, discharge temperature and the like.
Table 1 ferric phosphate lithium battery performance parameters
iron phosphate lithium battery capacity are very different, can be divided into three categories: small, when a few tenths to a few milliamperes, medium dozens when mAh, hundreds of large-scale mAh. Similar parameters of different types of batteries are also some differences. Here again present the most widely introduce a small standard parameters cylindrical package lithium iron phosphate battery. Outer profile dimensions: a diameter of 18mm, 650mm high (model 18650), its performance parameters shown in Table 2.
Table 2 Parameter cylindrical package of small standard battery of lithium iron phosphate
over-discharge to zero voltage test
The STL18650 (1100mAh) iron phosphate lithium battery discharged to zero voltage done test. Test conditions: with the 0.5C charging rate of STL18650 1100mAh battery is full, and then discharged to a discharge rate of 1.0C to a battery voltage 0C. Then put the battery divided into two 0V: storing a set of seven days, the other group of storage 30 days; stored after the expiry of a full charge rate 0.5C, 1.0C and then discharged. Finally, comparing the two zero-voltage storage different from the difference.
The results of the test, the zero voltage stored 7 days no leakage, good performance, capacity percentage 100; 30 days storage, no leakage, good performance, the percentage of capacity, 98; 30 days storage battery charge do 3 discharge cycle, and returned to the capacity of one hundred percent.
This test illustrates the battery even when the discharge occurred (even to 0V), and store a predetermined time, the battery does not leak, damage. This is another kind of the lithium ion battery does not have properties.
4. characteristics of lithium iron phosphate
Through the above description, LiFePO4 battery characteristics can be summarized as follows.
High output efficiency: Discharge Standard is 2 ~ 5C, continuous high-current discharge up to 10C, instantaneous pulse discharge (10S) up to 20C; good when
The high temperature performance: external temperature 65 ℃ internal temperature is as high as 95 ℃, at the end of battery discharge temperature up to 160. ℃, the structural safety of the battery, intact;
even though the battery internal or external injury, burn battery does not explode, the safety of the best;
excellent cycle life , after 500 cycles, the discharge capacity is still more than 95 percentage;
over-discharge to zero volts and no damage;
fast charge;
low cost;
no memory effect: rechargeable battery working conditions, often in full finished hold, the capacity will be lower than the rated capacity value rapidly, a phenomenon called memory effect. NiMH, NiCd memory exists, no such phenomenon lithium iron phosphate, regardless of what state the cell, can recharge it with, without first recharge is done.
small size, light weight, same size volume capacity of lithium iron phosphate 1/3 of the volume of lead-acid batteries, lead-acid battery weight of 1/3.
environmental pollution, the battery does not contain any heavy metals and rare metals (nickel-hydrogen battery to be rare), toxic (SGS authentication), non-polluting, in line with the provisions of the European ROHS, absolute green batteries. Lead-acid batteries, but there are a lot of lead, after discarding if not handled properly, will form a secondary pollution to the environment, while lithium iron phosphate material in terms of production and use, bothNon-polluting. .