The work principle and eight advantages of LiFePO4 battery

LiFePO4 battery, refers to a kind of lithium ion batteries which use of LiFePO4 as the anode material.Lithium ion battery anode materials mainly have cobalt acid lithium, lithium manganese acid lithium, nickel, ternary material, LiFePO4, etc.

Lithium ion batteries are extremely LiFePO4 material, its safety performance and cycle life has great advantages, which is one of the most important technical indicators of the power battery.1 c inflation cycle life can do 2000 times, puncture don't explode, overcharge when not easy combustion and explosion.LiFePO4 cathode material to make the large capacity lithium ion battery more and used in series.

LiFePO4 battery, refers to the use of LiFePO4 as the anode material of lithium ion batteries.Lithium ion battery anode materials mainly have cobalt acid lithium, lithium manganese acid lithium, nickel, ternary material, LiFePO4, etc.The cobalt acid lithium is at present most of the lithium ion battery cathode material.From material in principle, the LiFePO4 is a kind of embedded, embedded process, the principle and cobalt acid lithium manganese acid lithium is exactly the same.

1 introduction

LiFePO4 battery belong to lithium ion secondary battery, a main use is used for power battery, relative NI MH, NI Cd battery has a big advantage.

LiFePO4 battery charge and discharge efficiency is higher, discharge case to charge and discharge efficiency can reach more than 90%, while lead-acid batteries is about 80%.

2 the eight advantages

To improve the performance of security

LiFePO4 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.Even so, the overcharge safety than common liquid electrolyte cobalt acid lithium batteries, has been greatly improved.

The improvement of the life

LiFePO4 battery refers to the use of LiFePO4 as the anode material of lithium ion battery.

Long life cycle life of lead-acid battery in about 300 times, the highest is 500 times, andLiFePO4 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 LiFePO4 battery used under the same conditions, the theory of life will reach 7 ~ 8 years.Comprehensive consideration, the price performance ratio in theory for lead-acid battery more than four times.Large current discharge can be as big 2 C fast charge and discharge current, under the special charger, 1.5 C can make battery charging 40 minutes, starting current can be up to 2 C, lead-acid battery is the performance.

High temperature performance is good

LiFePO4 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 LiFePO4 electric peak of up to 350 ℃ to 500 ℃, lithium cobalt and lithium manganese acid and acid only at about 200 ℃.

The large capacity

With greater than ordinary battery (lead-acid, etc.) capacity.Single capacity of 5 ah - 1000 ah.

No memory effect

Rechargeable battery under the condition of are often filled with not to put the work, the capacity will quickly lower than the rated capacity values, this phenomenon is called memory effect.Memory like nickel metal hydrogen, nickel cadmium battery, and LiFePO4 battery do not have this phenomenon, the battery no matter in what condition, can use increases with the increasing charge, do not need to first put the recharging.

Light weight

The same specification of LiFePO4 battery capacity volume is two-thirds the size of lead-acid battery, weight is the 1/3 of lead-acid batteries.

Environmental protection

The battery is generally regarded as do not contain any heavy metals and rare metals (nickel metal hydrogen 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 accession to the WTO, Chinese exports of electric bikes will increase rapidly, and into Europe and the United States of electric bicycle has asked equipped with battery from pollution.

But experts say, lead-acid battery caused by environmental pollution, mainly in non-standard production process and recycling.By the same token, the lithium battery belongs to new energy industry is good, but it can't avoid the problem of heavy metal pollution.In the metal material processing such as lead, arsenic, cadmium, mercury, chromium is likely to be released into the dust and the water.The battery itself is a kind of chemicals, so is likely to produce two kinds of pollution: one is the production engineering process of waste pollution;2 it is scrapped after the battery pollution.

LiFePO4 battery also has its disadvantages: low temperature performance is poor, for example, tap density is small, the anode materials such as volume of LiFePO4 battery capacity than cobalt acid lithium and other lithium ion battery, so don't have an advantage in terms of micro cells.And when used for power battery, LiFePO4 battery and other batteries, battery consistency issues needs to face.

The contrast of power battery

Is currently the most promising application in power type lithium ion battery cathode material basically has modified lithium manganese acid (LiMn2O4), LiFePO4 (LiFePO4) and nickel cobalt manganese acid lithium (Li (Ni, Co, Mn) O2) ternary material.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 use of spinel lithium manganese acid mixed in a certain range.

Industry application

Coated carbon foil bring lithium electricity industry technical innovation and industry upgrade;Improve lithium electricity product performance, improve discharge rate.

As the requirement of domestic battery manufacturers of battery performance is increasing day by day, generally recognized by the domestic 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 magical coating, would improve the performance of the battery, into a new era.

Conductive coating is good by decentralizing nano conductive graphite coated particles, etc.It can provide excellent static conductivity, it is a layer of protection energy absorption layer.It can also provide a good cover protection performance.Coating with water and solvent resistance, can be used in aluminum, copper, stainless steel, aluminum and titanium plate.

Coated carbon coating on the performance of lithium-ion batteries with the following promotion:

1. Reduce the battery internal resistance, inhibition of charge and discharge cycle in the process of dynamic resistance increase;

2. Significantly improve the consistency of the battery pack, decrease the cost of the battery pack;

3. Improve the active material and fluid collection of glue adhesion, reduce the pole piece manufacturing cost;

4. Reduce the polarization, improve the rate performance, reduce the heating effect;

5. To prevent the electrolyte to set fluid corrosion;

6. The comprehensive factor and prolong the service life of the battery;

7. Coating thickness: conventional single 1 ~ 3 microns thick.

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 Infrasonic energy of a joint venture company, new Kobe motor, NEC, Hitachi, SONY, Saxony, Samsung, LG, etc.

The main development of the anode materials for LiFePO4 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 Saxony cooperation agreement, etc.Currently Volkswagen of Germany and France's Renault SA with the support of their governments are development and production of power type lithium ion battery.

disadvantages

Is a kind of material has great potential application development, in addition to focus on its merits, even more crucial is whether the material has fundamental flaws.

Domestic now generally choose the LiFePO4 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.

Analysis its reason, mainly has the following two points: first is influenced by American research direction, the Valence and the A123 company do early adoption of LiFePO4 lithium ion battery cathode material.Followed by the domestic has not been prepared for use with power type lithium ion battery has good high temperature cycle and storage performance of manganese acid lithium materials.But there are also nots allow to ignore the fundamental flaws of LiFePO4, it mainly include the following:

1. During the preparation of LiFePO4 sintering process, the reduction of iron oxide under high temperature and reducing atmosphere is the possibility of elemental iron.Elemental iron can cause cell micro short circuit, is the most taboo in the battery material.This is Japan has not the material as the main reason of power type lithium ion battery cathode material;

2. LiFePO4 has some defects on the performance, such as low tap density and compaction density, leading to a lower energy density of lithium-ion batteries.Low temperature performance is poorer, even if the nano and carbon coating to solve this problem.Argonne national laboratory, Dr DonHillebrand, director of the center for energy storage system when it comes to the LiFePO4 battery performance at low temperature with terrible to describe, their type of LiFePO4 lithium ion battery test results show that shows that the LiFePO4 battery at low temperature (below 0 ℃) could not make the electric car.Although there is also a manufacturer claims that the LiFePO4 battery capacity in low temperature retention is good, but it's a small discharge current and discharge cut-off voltage is very low.Under this condition, the equipment can't start the job.

3. The preparation of material cost and manufacturing cost is higher, batteries battery low yield, poor consistency.LiFePO4 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 LiFePO4 chemical elements in the Li, Fe and P is very rich, and a low cost, but could be prepared for the LiFePO4 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. Product consistency.At present domestic has not been a LiFePO4 material factory can solve this problem.From the Angle of material preparation, the synthetic reaction of the LiFePO4 is a complex multipurpose reaction, has a solid phosphate, iron oxide and lithium salt, plus the precursor and carbon reduction aerosols.In the process of the complex reaction, it is difficult to ensure consistency of response.

5. The problem of intellectual property rights.The earliest on an application for a patent for the LiFePO4 in June 25, 1993 by FXMITTERMAIER&SOEHNEOHG (DE), and in the same year on August 19, the application results.The basis of the LiFePO4 all patents by the United States at the university of Texas, and carbon coated by Canadian patent application.The two basic patent is not around the past, if royalties on the cost of calculation, the product cost will be further improved.

In addition, from the perspective of the experience of development and production of lithium ion battery, Japan is the country of the first commercial lithium-ion batteries, and high-end lithium ion battery has dominated the market.Although in some basic research on the leading and the United States, but so far not a single large lithium-ion battery production enterprises.As a result, Japan chose as power type lithium manganese acid lithium ion battery cathode material more makes sense.Even in the United States, use and lithium manganese acid LiFePO4 as the manufacturer of power type lithium ion battery cathode material is also a half, the federal government is also support for the development of the two systems.

In view of the problems existing in the LiFePO4, difficult as power type lithium ion battery cathode material in the field of new energy vehicles for a wide range of applications.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.

6. Working principle and characteristics of LiFePO4 battery full name is lithium ion battery, LiFePO4 the name was too long, referred to as LiFePO4 battery.Because of its performance is particularly suitable for power applications, to join in the name of "power" two words, namely the LiFePO4 power battery.Also some people called it "lithium iron (LiFe) power battery".

meaning

In the metal market, cobalt (Co) is the most expensive, and small storage capacity, nickel (Ni), manganese (Mn) cheaper, and iron (Fe) the cheapest.The price of the anode materials is consistent with the the prices of these metals market.Therefore, the use of LiFePO4 cathode material of lithium ion batteries should be the cheapest.Its another characteristic 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 LiFePO4 battery 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.

The 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 top and bottom side is the battery electrolyte battery, the battery by the metal casing airtight packaging.

LiFePO4 battery when charging, the anode of lithium ion Li + through the polymer membrane to the cathode migration;In the process of discharge, the cathode of lithium ion Li + migration through the diaphragm to the positive.Lithium ion battery is due to the lithium ion migration and named after the back and forth during charging and discharging.

The main performance

LiFePO4 battery's nominal voltage is 3.2 V, termination of charging voltage is 3.6 V, termination voltage is 2.0 V.Because of the various manufacturers adopt positive and negative electrode materials and electrolyte material quality and process is different, its performance will be some difference.For example the same models (the same kind of packaging standard cell), the battery capacity has a bigger difference (10% ~ 20%).

Here to explain is that different factory production of LiFePO4 power battery in various performance parameters will have some difference;In addition, there are some battery performance was not included in, such as battery internal resistance, self-discharge rate, temperature of the charge and discharge, etc.

LiFePO4 power battery capacity has a bigger difference, can be divided into three categories: small zero a few to several mah, medium of dozens of mah, large hundreds of mah.The same parameters of different types of batteries also have some differences.The widely used small standard cylindrical encapsulated LiFePO4 power battery, its parameters profile size: 18 mm diameter, 650 mm (model 18650).

Discharge to the zero voltage test

Using STL18650 (1100 mAh) LiFePO4 power battery discharge to zero voltage test.Test conditions: 0.5 C charge rate will be filled with 1100 mAh STL18650 batteries, and then use 1.0 C discharge rate discharge to the battery voltage is 0 C.Then to 0 v battery is divided into two groups: a group for seven days, another group of 30 days;Deposit matures with 0.5 C charge rate is full, and then use 1.0 C discharge.Finally comparing two zero voltage storage period the difference between different.

Test result, zero voltage battery for seven days without leakage, good performance, the capacity is 100%;For 30 days, no leakage, the performance good, capacity is 98%;For 30 days after the battery to do 3 times charge and discharge cycle, capacity and up to 100%.

This test shows that the battery discharge even seen (or even to 0 v), and deposit a certain time, battery leakage, damage.This is other kinds of lithium ion battery has no features.

The characteristics of the LiFePO4 battery

Through the above introduction, LiFePO4 battery can be summarized the following characteristics.

Efficient output: standard discharge is 2 ~ 5 c, continuous high discharge current can be up to 10 c, instantaneous pulse discharge (10 s) up to 20 c;

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, battery not combustion, explosion, security best;Excellent cycle life, after a 500 - cycle, its discharge capacity is greater than 95%;

Discharge to zero volts and no damage;Can quick charge;Low cost;No pollution to the environment.

The application of LiFePO4 power battery

Because the LiFePO4 power battery has the above characteristics, and produce a variety of different capacity of battery, soon be widely used.Its main application fields are:

Large electric vehicles: buses, electric cars, scenic touring and hybrid vehicles, etc.;

Light electric vehicles, electric bicycle, golf cart, small flat battery car, forklift truck, cleaning vehicles, electric wheelchair, etc.;

Electric tools: electric drill, electric saw, lawn mower, etc.;

Remote-controlled toy cars, boats, planes,

Solar and wind power energy storage equipment;

UPS and emergency lights, warning lights and a miner's lamp is best (security);

Alternative 3 v disposable lithium battery in the camera and 9 v nickel cadmium or nickel metal hydrogen rechargeable batteries (same size);

Small medical instruments and equipment and portable instruments, etc.

Here to take a replace lead-acid batteries with LiFePO4 power battery application example.With 36 v / 10 ah (360 wh) of lead-acid batteries, its weight of 12 kg, charge can walk about 50 km, charging times is about 100 times, use time about 1 year.If using LiFePO4 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.Although said that the price of LiFePO4 power battery is lead-acid battery is much higher, but the overall economic effect or using LiFePO4 power battery is better, and on the use of lighter.

Battery performance

Lithium ion power battery mainly depends on the performance of anode materials, LiFePO4 as a lithium battery materials has been appeared in recent years, domestic developed large-capacity LiFePO4 battery are in July 2005.Its safety performance and cycle life is unmatched by other materials, the most important of these is power battery technology index.1 c filling cycle life over 2000 times.Single battery charging voltage 30 v does not burn, puncture not explode.LiFePO4 cathode material to make the large capacity lithium ion battery series are more likely to use.In order to meet the needs of the frequent electric charge and discharge.Has a non-toxic, no pollution, safety performance is good, raw material sources, the price is cheap, the advantages of long service life, is the ideal of a new generation of lithium ion battery cathode material.

This project belongs to high-tech projects in the development of energy functional materials, is the national "863" plan, "973" plan and the period of "11th five-year plan" key support areas of high technology industry development planning.

Lithium ion batteries are extremely LiFePO4 material, its safety performance and cycle life has great advantages, which is one of the most important technical indicators of the power battery.1 c inflation cycle life can do 2000 times, puncture don't explode, overcharge when not easy combustion and explosion.LiFePO4 cathode material to make the large capacity lithium ion battery more and used in series.

Research and application

LiFePO4 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 DebochTEC. GmbH, LiFePO4 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 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 once every 3 days to charge and discharge computation, can be continuous use 24 years, is the longevity of 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, DebochTEC. 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;In the field of civil automobile use blue, 2500 times;Green, 2000 is suitable for small portable mobile devices.

The page contains the contents of the machine translation.