What are the advantages and disadvantages of the lithium iron phosphate battery

The introduction of lithium iron phosphate battery

Lithium iron phosphate battery belongs to Li-ion secondary battery. One of the main applications is used as power battery. It has apparent advantages than NI-MH and Ni-Cd battery.

The charging and discharging rate of the lithium iron phosphate battery is relatively higher, 80%-90%. That of lead-acid battery is 80%.

The advantages and disadvantages of the lithium iron phosphate battery

The advantages of lithium iron phosphate battery

The improvement of safety performance

Given that the P-O bond of lithium iron phosphate crystal is too stable to be destroyed. It won’t break the structure, heat up or form strong oxidizing substance, which proves that it has great safety performance. There have been cases reported that some samples have combustion phenomena after acupuncture or on short circuit test, but no explosion. Nevertheless, it makes greater progress on safety performance than normal liquid electrolyte lithium cobalt oxide battery.

Improvement of cycle life

Lithium iron phosphate battery is a lithium ion battery using lithium iron phosphate as anode material.

The cycle life of lead-acid battery with long cycle life is 300 times or so, and its max is 500 times. However, lithium iron phosphate power battery can reach over 2000 times, and 2000 times under standard charging (5 Ah). The lead-acid battery with equivalent quality can be used for half year as a new one, half year for an old one, and one more half year after maintenance. Above all, its cycle life is about 1-1.5 years. In contrast, lithium iron phosphate battery can be used for 7-8 years theoretically under the same circumstance. All in all, the ratio of performance and price of lithium iron phosphate battery will be over 4 times than lead –acid battery. It can be fast charged through 2C current, and fully charged within 40 minutes under 1.5C by specified charger. The starting current can reach 2C, while lead –acid battery has no such performance at present.

Good high temperature performance

It has wide operating temperature range (-20C--+75C) and good high temperature performance. Electric heating peak value of lithium iron phosphate can reach 350℃-500℃, while lithium manganite and lithium cobalt oxide is around 200℃. 

Large capacity

Lithium iron phosphate battery has larger capacity than normal battery (lead-acid, etc.). 5AH-1000AH (single battery)

No memory effect

If a rechargeable battery always works without discharging completely, its capacity will rapidly lessen than rated capacity. This situation is called memory effect. NI-MH battery and nickel-cadmium battery have memory effect, but not Lithium iron phosphate battery. Whatever its state is, charge and use at any time, no need to recharge after fully discharge.

Light weight

The volume of lithium iron phosphate battery with the same capacity is 2/3 as lead-acid battery, and its weight is 1/3 as lead-acid battery.

Environmental protection

Lithium iron phosphate battery is believed that it doesn’t have any heavy metal or rare metal (NI-MH battery needs rare metal). It is non-toxic (passed SGS certificate), extremely environmentally friendly battery meeting RoHS regulation. Considering for environmental protection, this battery is listed in “863” national high-tech development schemes and becomes the key project with national support and encouragement. As China joins in WTO, the export volume of Chinese electric bikes will increase rapidly. At present, all electric bikes that import to Europe need to prepare environmentally friendly battery.

However, some experts said that the pollution caused by lead-acid battery mainly happens in irregular manufacturing process and recycle handling of the enterprises. Similarly, Li ion battery cannot prevent heavy metal pollution even that it belongs to new energy industry. During processing, lead, arsenic, cadmium, mercury, chromium and so on may be released into dust and water. Battery itself is a chemical substance, so it may produce two kinds of pollution: one is industrial waste, the other is battery pollution after scrap.

Lithium iron phosphate battery also has its shortcomings: such as poor low temperature performance, small tap density of anode material. The lithium iron phosphate battery with same capacity has larger volume than lithium cobalt oxide battery, so it has no advantages on micro battery. It still needs to deal with battery consistency issue, just like any other battery, when it is used as power battery.

Comparison of power battery

Nowadays, those anode materials mostly used in power lithium ion battery include lithium manganite, lithium iron phosphate and Ni-Co lithium manganite ternary material. This ternary material is difficult to become the mainstream in electrical vehicle power Li-ion battery because lack of cobalt resources, high cost of nickel, cobalt and price fluctuation, but it can be used together with lithium manganite spinel to some degree.

Industry application

Carbon-coated aluminum foil helps lithium ion battery industry on technical innovation and industry upgrading.

Upgrade the product performance of lithium ion battery and improve discharge rate.

As the performance requirement of domestic battery manufacture is more and more severe, new energy battery materials are widely popular: conducting material & aluminum foil / copper foil  conductive coating.

Its advantages are: when deal with battery material, it has good high charging and discharging performance, larger specific capacity, but poor cycling stability which can help stopping continuous usage.

Product application: inside the golf vehicle battery pack

This is a wonderful coating that improves battery performance and leads the battery industry into a new era.

Conductive coating is constituted by separate Nano-conductive graphite covering particle. It can provide with great static conductive performance by a layer of energy absorbing protection which has protective properties. There are liquid coating and solvent coating. Both of them can be used on aluminum sheet, copper sheet, stainless steel, aluminum and titanium bipolar plates.

Carbon-coated coating can improve Li-ion battery performance as below.

Decrease battery internal resistance, and restrain increasing dynamic resistance during charging and discharging process.

Apparently improve consistency of battery pack and reduce the cost.

Improve adhesive ability of active material and current collector, so as to reduce pole piece manufacture cost.

Reduce polarization, improve rate capability and decrease low thermal effect.

Prevent electrolyte corroding the current collector.

Control all factors, so as to prolong battery cycle life.

Thickness of coating: single layer is normally 1～3μm.

Japan and South Korea mainly develop lithium ion power battery with lithium manganite and Ni-Co lithium manganite ternary material as anode material at present. America mainly invents lithium ion power battery with lithium iron phosphate as anode material, but its major vehicle manufacturer decides to use manganese-based anode material Li-ion power battery in PHEV and EV. It is said that American A123 company is considering to expand into the area of lithium manganite material, while European countries such as Germany devote to cooperate with battery companies in other country to develop power vehicle, for example, alliance between Daimler-Benz and France Saft, collaboration agreement between German Volkswagen and Japan SANYO. Recently, German Volkswagen and France Renault are developing and producing Li-ion power battery.

The disadvantages of lithium iron phosphate battery

Whether the material has application potential is not only depended on its advantages, but the more important point is whether it has fundamental disadvantages.

Lithium iron phosphate is widely used as anode material in lithium ion battery at home recently. From government, scientific research institution, enterprise and even market analyst in security companies are optimistic on this material and regard it as the developing direction of Li-ion power battery. As for the reasons, there are mainly two factors: first it is affected by American developing direction. American Valence and A123 are the first two companies to use lithium iron phosphate as anode material in Li-ion battery. Besides, there is no lithium manganite material with good high temperature circulatory and storage performance that can be used in Li-ion battery at home. However, lithium iron phosphate still has some noticeable fundamental shortcomings as follow:

During sintering process of lithium iron phosphate, iron oxide may turn back into iron under high temperature reducing conditions. Iron will result in micro short circuit of the battery and it is the most taboo in a battery. This is also the reason why Japan don’t use lithium iron phosphate as anode material in lithium ion power battery.

There are some performance shortcomings of lithium iron phosphate, such as low tap density and compaction density, which also results in low capacity density. Besides, its poor low temperature performance issue cannot be solved even by nanocrystallization and carbon-encapsulated. DonHillebrand doctor, center director of American Argonne National Laborator storage energy system, described the low temperature performance of lithium iron phosphate battery with the word “terrible”. The report result of the test of lithium iron phosphate battery shows that it cannot be used in electrical vehicle under low temperature (below 0℃). Some factories still believe that capacity retention ratio of lithium iron phosphate battery is quite OK under low temperature, but that only occurs under small discharging current and low discharging cut-off voltage. Under this circumstances, the device cannot work normally.

Lithium iron phosphate has high material and manufacturing cost, low production yield and low consistency. Nanocrystallization and carbon-encapsulated do improve the electrochemical performance of material, but still lead to other issue, such as low energy density, high cost of material synthesis, processing failure of electrode and strict requirement of environment. Although chemical elements Li, Fe and P are rich resources and have low price, the manufacturing process cost of lithium iron phosphate is not low. Except the R&D costs, the material processing cost and battery processing will make higher cost of final single storage capacity.

Poor product consistency: There is no factory of lithium iron phosphate can deal with this issue. As for material processing, the synthetic reaction of lithium iron phosphate is a sophisticated heterogeneous reaction, including solidoid phosphate, iron oxides, lithium, precursor of carbon and reductant gas phase. It’s difficult to make sure the consistency of the reaction during a complicated chemical reaction.

Intellectual property issue: the earliest patent of lithium iron phosphate was applied by FXMITTERMAIER&SOEHNEOHG(DE) on June 25th,1993. The result was announced in the next year. The basic patent of lithium iron phosphate is belong to American University of Texas, while the carbon-encapsulated patent is belong to Canadians. These two patent royalties will increase the product cost, too.

As for the experience of R&D and manufacture of Li-ion battery, Japan is the earliest commercialized country and plays the leading role in high-end Li-ion battery business all the time. Although America has some leading basic research, there is no large scale Li-ion battery manufacture enterprise in America. Therefore, it makes sense for Japan to use lithium manganite as anode material in Li-ion power battery. Even in America, the quantity of manufacturers using lithium iron phosphate and lithium manganite as the anode material of Li-ion power battery end up an equal split. The federal government supports the R&D of both of these materials. Based on the above issues of lithium iron phosphate, it’s difficult to widely use it as anode material of Li-ion power battery in new energy vehicle area. If one day, someone can solve the problems of high temperature circulatory and poor storage performance, lithium iron phosphate must be really potential in Li-ion power battery application with its advantages of low cost and high rate performance.

The work principles and features of lithium iron phosphate battery

The full name of lithium iron is lithium iron lithium ion battery. It is such a long name, so that we can call it lithium iron phosphate battery. Because its performance is really suitable for power application, so named lithium iron phosphate power battery, some may call Li-Fe power battery.

Significance

By the end of adding this word entry (April 4th,2013), cobalt is the most expensive in commodity market with small storage, nickel and manganese are cheaper, while iron is the cheapest. The prices of anode materials are also consistent with these metals. Therefore, it is the cheapest to use the Li-ion battery using lithium iron phosphate as anode material. Besides, it is environmentally friendly.

The requirements of rechargeable battery: high capacity, high output voltage, good charging and discharging recycle performance, stable output voltage, can charge and discharge by large current, stable electrochemistry performance, maintain safe during usage (won’t result in combustion or explosion due to overcharging, over-discharging, etc.), wide operation temperature rage, non-toxic or little toxic, environmental friendly. Lithium iron phosphate battery using LiFePO4 as anode material has good performance requirements, especially on large discharge rate (discharging at 5-10c), discharging voltage stability, safety (no combustion, no explosion), cycle life (cycle times), no pollution on environment. It is the best large current output power battery at present.

Structure and work principles

The structure inside LiFePO4 battery is as shown in Figure 1. The left side is LiFePO4 in olivine Structure as the anode material of the battery, connected by aluminum foil and anode. The separator in the middle isolates the anode and cathode, which can pass Li+ but not e-. The right side is the cathode combined by carbon (graphite), which connected by copper foil and the cathode. It is the electrolyte between upper and lower end. The battery is sealed by metal outer.

While charging, the Li+ of the lithium iron phosphate battery transmits to the cathode through polymer separator. During discharging, the Li+ transmits to the anode through separator. This kind of transmission of Li ion during charging and discharging is the reason why it is named lithium ion battery.

Major performance

The nominal voltage of LiFePO4 battery is 3.2V, charge limited voltage is 3.6V, and end-off voltage is 2.0V. It will have differences on performance because of different anode & cathode materials, quality and process of electrolyte materials. For example, the capacity of battery is much different (10%-20%) with the same type (standard battery with the same packaging).

The major performance of lithium iron phosphate power battery is listed in Figure 1. In order to comparing with any other rechargeable battery, it also lists other type of rechargeable battery. It is noted that there are some differences on each performance parameter of different lithium iron phosphate battery factories. Besides, some battery performances are not in the list, such as internal resistance, self-discharge rate, charging and discharging temperature, etc.

There are big differences on lithium iron phosphate battery capacity, which can be classified into three categories: small-scale is a few tenths of a mAh to a few mAh, middle-scale is dozens of mAh, while large-scale is hundreds of mAh. There are also some differences on different types of batteries with the same parameters. Here show the parameters of a cylindrical small-scale lithium iron phosphate power battery with widely application. The outer size: diameter is 18mm, height is 650mm (type No. is 18650).

Over-discharge to zero voltage test

Take a test discharging to zero voltage by STL18650（1100mAh）lithium iron phosphate power battery. Test condition: charge the batteries with 0.5C charging rate, and then discharge until its voltage become zero with 1.0c charging rate. Divide these batteries into two groups: one store for 7 days, the other for 30 days. After that, recharge fully with 0.5c charging rate, and then discharge with 1.0c. Finally, find out the differences between these two kinds of zero voltage storage time.

The result is that no leakage after 7 days zero voltage storage, good performance and 100% capacity. After 30 days, there is no leakage, good performance and 98% capacity. It can return 100% capacity by three times charging and discharging cycle for the battery with 30 days storage.

This test proves that there is no leakage and no damage on the battery even though having over-discharged (even to zero voltage).

The features of lithium iron phosphate battery

Above all, we can summarize the features of LiFePO4 battery as follow: 

High efficiency output: standard discharging is 2～5C, it can reach 10c after continuous large current discharging, and its instant pulse discharging can be up to 20C.

Good performance under high temperature: the inner temperature reaches 95℃ when the outside is 65℃. It is up to 160℃ after finishing discharging, and the structure is still safe and intact.

It’s better no fire, no explosion and safe on the battery, even if the battery inside and outside was damage.

It has fantastic cycle life for that its capacity is still over 95% after 500 cycles.

No damage even discharge to zero voltage.

It can charge rapidly.

Low cost

No pollution to the environment.

The application of lithium iron phosphate battery

The lithium iron phosphate battery is widely used rapidly because it can produce battery with different capacity due to its above advantages. Its major application areas are as follow:

Large-scale electric vehicles: bus, electric car, tourist coach, HEV, etc.

Light electric vehicle: electric bicycle, golf cart, small-scale plate-type battery car, forklift, cleaning trolley, electric wheelchair, etc.

Electric tool: electric drill, electric saw, cropper, etc.

Toys such as remote-controlled car, boat, plane, etc.

The energy storage device of solar power and wind power generation

UPS &emergency light, caution light & miner light (wonderful safety performance)

The replacement of 3V disposable Li-ion battery of camera, 9V nickel-cadmium or nickel hydride rechargeable battery (totally the same size)

Small –scale medical equipment and portable instrument

Here take an application example of replacing lead-acid battery for lithium iron phosphate power battery. The lead-acid battery with 36V/10Ah（360Wh）weighed 12kg has a travel distance for around 50km after charging for one time. If charging the battery about 100 times, it can be used for one year or so. It has a travel distance for around 80km after charging for one time, can charge for 100 times, and the cycle life can reach 3～5 years, if replaced by lithium iron phosphate power battery weighed 4kg with the same capacity of 360Wh (twelve 10Ah batteries in series). Although lithium iron phosphate power battery is more expensive than lead-acid battery, it’s better to use lithium iron phosphate power battery based on the general economic strength and portability. 

The performance of lithium iron phosphate battery

The performance of Li-ion power battery depends on anode and cathode materials. Lithium iron phosphate was used as Li-ion battery material in recent years. Lithium iron phosphate battery was invented in mess at home in July, 2005. The safety performance and cycle life is disparate by other materials, which is the most important technical index of power battery. The charging and discharging cycle life reaches 2000 times with 1C current. There is no fire after overcharge voltage of 30V for single cell, no explosion with puncture. Large capacity Li-ion battery made by lithium iron phosphate is easy to be in series, so as to meet the requirement of electric vehicle frequent charging and discharging. It is the ideal anode material of Li-ion battery in new era with the advantages of non-toxic, no pollution, good safety performance, rich raw materials, low cost, long cycle life, etc.

This project belongs to the development of high-tech functionality energy materials, national 863 program, 973 program and the 11th Five-Year Plan of high-tech development key support.

The anode of Li-ion battery is made by lithium iron phosphate, which has great advantages of safety performance and cycle life and it is one of the most important technical index. The charging and discharging cycle life reaches 2000 times with 1C current. No explosion with puncture and not easy to lead in fire and explosion while overcharging. It is easier to use large capacity Li-ion battery produced by lithium iron phosphate battery in series and in parallel. 

The scientific applications of lithium iron phosphate battery

Recently, there is much news about new types of batteries make great process and is possible to replace the traditional batteries. Therefore, it is hopeful that mobile phone and tablet have longer cycle life. However, most of these batteries are still in research phase and it’s hard to say when they can become commercially available. Now, DebochTEC.GmbH, a new energy company, has brought out a new energy technique easier to implement: Li-ion battery with iron.

The white paper of lithium iron phosphate battery announced by DebochTEC.GmbH shows that the energy density of 32650 single cell (diameter is 32mm/ length is 65mm) can reach 6000mAh. Compared with 32650 single cell with 5000mAh at the current industry, the battery with the same volume has increased 1000mAh, which means 20%, so that one cell can recharge nearly 4 times to an iPhone4S.

What’s more, this kind of battery can maintain 80% capacity after recycling 3000 times under low rate charging and discharging environment of single cell, while normal battery can only recycle 500 times with the same circumstance. If charge and discharge every three-day, the battery can keep using for 24 years, so it is a veritable battery with long cycle life.

This kind of new type battery technique can be widely used in portable power bank, small-scale UPS, laptop, car battery and other devices. In order to deal with different application environment, DebochTEC.GmbH produces batteries with different colors according to the differences of charging cycles: golden one is for military with 3000 times cycle life; blue one is for civilian car area with 2500 times cycle life; green one is for small-scale portable mobile devices.