Enough about lithium iron phosphate batteries!

Lithium iron phosphate battery refers to lithium ion battery with lithium iron phosphate as positive electrode material. The anode materials of lithium ion battery mainly include lithium cobalt acid, lithium manganese acid, lithium nickel acid, ternary materials, lithium iron phosphate and so on. At present, lithium cobalt oxide is the anode material used in most lithium ion batteries. In terms of material principle, lithium iron phosphate is also an embedded/unembedded process, which is exactly the same as lithium cobalt and lithium manganese.

1. Introduction

Lithium iron phosphate battery is a lithium ion secondary battery, one of the main USES is as a power battery, compared with ni-mh, ni-cd battery has great advantages.

The charging and discharging efficiency of lithium iron phosphate battery is higher than 90%. Lead-acid batteries are about 80%.

2. Eight advantages

Improved safety performance

The p-o bond in the lithium iron phosphate crystal is stable and difficult to be decomposed. Even at high temperature or over charge, it will not 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 of acupuncture or short circuit experiment, a small part of samples were found to have combustion phenomenon, but there was no explosion event. However, in the overcharge experiment, a high voltage charge that was several times higher than its own discharge voltage was used, and explosion phenomenon was still found. Nevertheless, its overcharge safety has been greatly improved compared with ordinary liquid electrolyte lithium cobalt battery.

Life improvement

Lithium iron phosphate battery refers to lithium ion battery with lithium iron phosphate as the positive electrode material.

Long life lead-acid battery cycle life of 300 times or so, the highest is 500 times, and lithium iron phosphate power battery cycle life of more than 2000 times, the standard charge (5 hours rate) use, can reach 2000 times. Lead-acid battery of the same quality is "new half year, old half year, maintenance and maintenance of half a year", the most is 1~1.5 years, and lithium iron phosphate battery in the same condition, the theoretical life will reach 7~8 years. Overall, the performance price is more than 4 times of the theoretical lead-acid battery. Large current discharge can be large current 2C quick charge and discharge, in the special charger, 1.5C charge can make the battery full within 40 minutes, starting current up to 2C, but lead-acid batteries do not have this 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 can reach 350 ℃ to 500 ℃ heating peak lithium cobalt and lithium manganese acid and acid only at about 200 ℃.

The large capacity

It has a larger capacity than ordinary batteries (lead acid, etc.). 5 ah ah - 1000 (monomer)

No memory effect

Rechargeable batteries often work under the condition of being constantly filled, and the capacity will quickly fall below the rated capacity value. This phenomenon is called memory effect. Nickel-metal hydride and nickel-cadmium batteries have memory, while lithium iron phosphate batteries have no such phenomenon. No matter what state the battery is in, it can be charged and used at any time, without having to be put out before recharging.

Light weight

Lithium iron phosphate batteries of the same size are two-thirds the size and one-third 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 need rare metals), non-toxic (SGS certification), pollution-free, in line with European RoHS regulations, for the absolute green environmental protection battery certificate. Therefore, lithium battery is favored by the industry, mainly due to environmental considerations, so the battery was included in the "863" national high-tech development plan during the "tenth five-year plan" period, and became a national key support and encourage development project. With China's accession to the WTO, China's exports of electric bicycles will increase rapidly, while electric bicycles entering the us and Europe have been required to be equipped with pollution-free batteries.

But some experts say that the environmental pollution caused by lead-acid batteries mainly occurs in the non-standard production process and recycling process. Similarly, lithium batteries are good for the new energy industry, but they are not immune to heavy metal pollution. Metal materials such as lead, arsenic, cadmium, mercury and chromium can be released into dust and water. Battery itself is a chemical substance, so there may be two kinds of pollution. Second, battery pollution after scrapping.

Lithium iron phosphate battery also has its disadvantages: for example, low temperature performance is poor, the positive electrode material vibrates density is small, the volume of equal capacity lithium iron phosphate battery is larger than lithium ion battery such as lithium cobalt acid, so it has no advantage in the micro battery. When used in power batteries, lithium iron phosphate batteries, like other batteries, need to face the problem of battery consistency.

Comparison of power batteries

At present, the most promising anode materials for dynamic lithium ion batteries are mainly modified lithium manganate (LiMn2O4), lithium iron phosphate (LiFePO4) and lithium nickel-cobalt manganate (Li(Ni,Co,Mn)O2) ternary materials. Due to the lack of cobalt resources and the high cost of nickel and cobalt, it is generally believed that it is difficult to become the mainstream of the power type lithium ion battery for electric vehicles, but it can be mixed with spinel lithium manganese oxide within a certain range.

Industry application

Aluminum foil coating for the lithium battery industry to bring technological innovation and industrial upgrading

Improve the performance of lithium battery and discharge rate

With the increasing requirement of domestic battery manufacturers on battery performance, new energy battery materials are generally accepted in China: conductive materials & conductive coating aluminum foil/copper foil.

Its advantages are as follows: when dealing with battery materials, it often has good charging and discharging performance with high rate, large specific capacity, poor cycling stability, serious attenuation and other reasons, so it has to make a choice 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 can provide excellent static conductivity, is a protective energy absorption layer. It can also provide good cover protection performance. The coating is water based and solvent based and can be used on aluminum, copper, stainless steel, aluminum and titanium bipolar plates.

Carbon coating can improve the performance of lithium battery as follows

1. Reduce the internal resistance of the battery and restrain the increase of dynamic internal resistance during the charging and discharging cycle;

2. Significantly improve the consistency of the battery pack and reduce the cost of the battery pack;

3. Improve the adhesion of active materials and collector fluid, and reduce the manufacturing cost of pole sheet;

4. Reduce polarization, improve multiplier performance and reduce thermal effect;

5. Prevent the corrosion of electrolyte on the collector fluid;

6. Combine factors to extend battery life.

7. Coating thickness: 1 ~ 3 m for conventional single thickness.

In recent years, Japan and the republic of Korea have mainly developed dynamic lithium ion batteries with modified lithium manganate and nickel-cobalt lithium manganate tri-material as the positive electrode material. 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 power-based lithium-ion batteries with support from their governments.

3. The shortcomings

Whether a material has potential for application development, in addition to focusing on its advantages, more critical is whether the material has fundamental defects.

At present, lithium iron phosphate is widely used as the positive electrode material for dynamic lithium ion batteries in China. Market analysts from the government, scientific research institutions, enterprises and even securities companies are optimistic about this material and regard it as the development direction of dynamic lithium ion batteries. Valence and A123 of the United States were the first to use lithium iron phosphate as the cathode material for lithium-ion batteries. Secondly, lithium manganate materials with good high temperature cycling and storage performance for dynamic lithium ion batteries have not been prepared in China. However, lithium iron phosphate also has fundamental defects that cannot be ignored, which can be summarized as follows:

1. In the sintering process of the preparation of lithium iron phosphate, there is a possibility that the iron oxide can be reduced to the elemental iron under the high temperature reducing atmosphere. The elemental iron is the most taboo substance in the battery because it can cause micro-short circuit of the battery. This is also the main reason why Japan has not used this material as a positive electrode material for dynamic lithium-ion batteries.

2. Lithium iron phosphate has some performance defects, such as low density of vibration and compaction, resulting in low energy density of lithium ion battery. The low temperature performance is poor, even if the nano and carbon coating does not solve this problem. Argonne national laboratory, Dr DonHillebrand, director of the center for energy storage system 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 the capacity retention rate of lithium iron phosphate battery is good at low temperature, that is in the case of low discharge current and low cut-off voltage. In this case, the device simply won't work.

3. The material preparation cost is higher than the battery manufacturing cost, and the battery yield is low with poor consistency. Although the nanometer and carbon coating of lithium iron phosphate improves the electrochemical properties of the material, it also brings other problems, such as the reduction of energy density, the increase of synthesis cost, poor electrode processing performance and the harsh requirements on the environment. Although the chemical elements Li, Fe and P in lithium iron phosphate are abundant and the cost is low, the production cost of lithium iron phosphate product is not low. Even if the initial research and development cost is removed, the process cost of the material plus the cost of preparing the battery will make the final unit energy storage cost higher.

4. Poor product consistency. At present, there is no lithium iron phosphate material factory in China that can solve this problem. From the point of view of material preparation, the synthesis reaction of lithium iron phosphate is a complex multiphase reaction, including solid phase phosphates, iron oxides and lithium salts, plus carbon precursor and reducing gas phase. In this complex reaction process, it is difficult to ensure the consistency of the reaction.

5. Intellectual property rights. The earliest patent application for lithium iron phosphate was obtained on 25 June 1993 by FXMITTERMAIER&SOEHNEOHG(DE) and the results were announced on 19 August 1993. The basic patent for lithium iron phosphate is held by the university of Texas, while the carbon-coated patent is held by the canadians. There is no way around these two foundational patents, and if royalties are included in the cost, the cost of the product will go up even further.

In addition, from the research and development and production experience of lithium ion battery, Japan is the earliest commercialized country of lithium ion battery, and has been occupying the high-end lithium ion battery market. The United States, though leading in some basic research, has so far not had a large lithium-ion battery manufacturer. Therefore, it is more reasonable for Japan to choose modified lithium manganate as the positive electrode material for dynamic lithium ion batteries. Even in the United States, manufacturers of lithium iron phosphate and lithium manganate as anode materials for power lithium-ion batteries are split 50-50, and the federal government supports both systems. In view of the above problems existing in lithium iron phosphate, it is difficult to be widely used as a positive electrode material for dynamic lithium ion batteries in new energy vehicles and other fields. If it can solve the problem of poor high-temperature cycling and storage performance of lithium manganate, it will have great potential in the application of dynamic lithium ion batteries due to its advantages of low cost and high magnification performance.

The full name of lithium iron phosphate battery is lithium iron phosphate lithium ion battery, the name is too long, referred to as lithium iron phosphate battery. Since its performance is particularly suitable for the application of power, the word "power" was added in the name, namely lithium iron phosphate power battery. It is also called "lithium iron (LiFe) power battery".

meaning

By the time I added this entry (April 24, 2013), cobalt (Co) is the most expensive metal on the market, and it doesn't have much storage, nickel (Ni) and manganese (Mn) are the cheapest, and iron (Fe) is the cheapest. The prices of anode materials are also in line with those of these metals. Therefore, the LiFePO4 anode lithium ion battery should be the cheapest. Another characteristic of it is no pollution to the environment.

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

The internal structure of the LiFePO4 battery is shown in figure 1. On the left is the olivine LiFePO4 as the positive electrode of the battery, which is connected by aluminum foil and the positive electrode of the battery. In the middle is a polymer membrane, which separates the positive electrode from the negative electrode. But lithium ion Li+ can pass through while electron e- cannot. Between the upper and lower ends of the battery is the electrolyte of the battery, which is sealed by a metal shell.

When the LiFePO4 battery is charged, the lithium ion Li+ in the positive electrode migrates to the negative electrode through the polymer membrane. During discharge, the lithium ion Li+ in the negative electrode migrates to the positive electrode through the diaphragm. Lithium-ion batteries are named for the way they move back and forth between charge and discharge.

The main performance

The nominal voltage of LiFePO4 battery is 3.2v, the termination charging voltage is 3.6v, and the termination discharging voltage is 2.0v. Due to the different quality and process of positive and negative electrode materials and electrolyte materials used by various manufacturers, there will be some differences in their performance. For example, the battery capacity of the same type (standard battery in the same package) varies greatly (10% ~ 20%).

The main performance of lithium iron phosphate battery is listed in table 1. For comparison with other rechargeable batteries, the performance of other types of rechargeable batteries is also listed in the table. It should be noted here that the performance parameters of lithium iron phosphate power batteries produced by different factories will have some differences. In addition, some battery properties are not included, such as battery internal resistance, self-discharge rate, charging and discharging temperature.

Lithium iron phosphate power batteries vary widely in capacity and can be divided into three categories: small ones ranging from a few tenths to a few milliamps, medium-sized ones ranging from a few tens of milliamps, and large ones ranging from a few hundred milliamps. There are also some differences in the same parameters for different types of batteries. The parameters of a small standard cylindrical encapsulated lithium iron phosphate battery, which is widely used at present, are introduced here. Its overall size: diameter 18mm, height 650mm(model 18650), its parameter performance is shown in table 2.

Over discharge to zero voltage test

The STL18650(1100mAh) lithium iron phosphate battery was used for the test from discharge to zero voltage. Test conditions: 1100mAh STL18650 battery was fully charged with 0.5c charging rate, and then discharged to 0C battery voltage with 1.0c discharging rate. Then put the 0V battery into two groups: one group for 7 days, another group for 30 days; When the storage expires, charge it with 0.5c charging rate and discharge it with 1.0c. Finally, the differences between the two ZVS storage periods were compared.

The test results show that after 7 days of zero voltage storage, the battery has no leakage, good performance and 100% capacity. After 30 days, no leakage, good performance, 98% capacity; After 30 days of storage, the battery was charged and discharged for 3 more cycles, and the capacity was restored to 100%.

This test shows that even if the battery has been discharged (even to 0V), and stored for a certain time, the battery will not leak or damage. This is a characteristic that other kinds of lithium-ion batteries do not have.

Lithium iron phosphate battery features

Through the above introduction, the LiFePO4 battery can be summarized as follows.

High efficiency output: standard discharge of 2 ~ 5C, continuous high current discharge up to 10C, instantaneous pulse discharge (10S) up to 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 internal or external damage, the battery does not burn, do not explode, the best safety;

Excellent cycle life, 500 cycles, the discharge capacity is still greater than 95%;

Over discharge to zero volts without damage;

Quick charging;

Low cost;

No pollution to the environment.

Application of lithium iron phosphate battery

Because the lithium iron phosphate power battery has the above characteristics, and produces a variety of different capacity of the battery, it will soon be widely used. Its main application areas are:

Large electric vehicles: buses, electric cars, tourist attractions and hybrid vehicles, etc.

Light electric vehicles: electric bicycles, golf carts, small flat-bed electric vehicles, forklifts, cleaning vehicles, electric wheelchairs, etc.;

Power tools: electric drill, chainsaw, lawn mower, etc.

Remote control of cars, boats, aircraft and other toys;

Solar and wind energy storage equipment;

UPS and emergency lights, warning lights and mine lights (best safety);

Replace 3V disposable lithium batteries and 9V nickel-cadmium or nickel-hydride rechargeable batteries in cameras (the same size);

Small medical instruments and portable instruments, etc.

Here is an example of the application of lithium iron phosphate power batteries instead of lead-acid batteries. The lead-acid battery is adopted 36V/10Ah(360Wh), with a weight of 12kg, a walking distance of about 50km with a charge of about 100 times, and a service time of about 1 year. If the lithium iron phosphate power battery is used, the same 360Wh energy (composed of 12 10Ah batteries in series) is used, with a weight of about 4kg. The battery can be charged once for a walk of about 80km, and the charging times can be up to 1000 times. The service life can be up to 3-5 years. Although lithium iron phosphate batteries are much more expensive than lead-acid batteries, the overall economics are better and lighter to use.

5. Battery performance

The performance of lithium ion power battery mainly depends on the positive and negative electrode materials, lithium iron phosphate as a lithium battery material is only in recent years, the domestic development of large capacity lithium iron phosphate battery is July 2005. Its safety performance and cycle life is other materials can not be compared, these are the most important technical indicators of power batteries. The cycle life of 1C is up to 2000 times. Single battery overcharge voltage 30V does not burn, puncture does not explode. Lithium iron phosphate anode materials to make large capacity lithium ion batteries easier to use in series. In order to meet the needs of frequent charging and discharging of electric vehicles. It is an ideal anode material for the new generation of lithium ion batteries.

This project belongs to the development of functional energy materials in high-tech projects, and is the key support area of the national "863" plan, "973" plan and the "eleventh five-year" high-tech industry development plan.

The safety performance and cycle life of lithium iron phosphate materials are the most important technical indicators of lithium ion batteries. 1C charge and discharge cycle life can achieve 2000 times, puncture does not explode, over charge is not easy to burn and explosion. High-capacity lithium-ion batteries made from lithium iron phosphate anode materials are easier to use in series.

6. Scientific research application

Lithium iron phosphate battery

The recent flurry of reports about new batteries that could replace conventional lithium-ion batteries has given us hope for more battery life in phones and tablets, but much of it remains in the lab, and it's not clear when, or even if, it will be ready for commercial use on a large scale. In August 2012, the new energy company DebochTEC.GmbH brought another new energy technology closer to reality: iron-containing lithium batteries.

DebochTEC. GmbH, according to the lithium iron phosphate battery technology, the white paper published in the use of 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 4 s mobile phone recharged almost four times.

What's more, when used in a single low-magnification charging and discharging environment, the battery's power remains at about 80% after up to 3,000 cycles, while ordinary lithium batteries can be recharged around 500 times. According to the charge and discharge every 3 days, can be used for 24 years, is a veritable longevity battery.

This new battery technology can be widely used in portable portable power supply, small UPS, laptop batteries, car batteries and other equipment. In addition, DebochTEC. In the field of civil automobiles, blue color is used 2,500 times. The green, 2000 times is suitable for small portable mobile devices.

The page contains the contents of the machine translation.