This article will tell you the fire risk of lithium ion batteries and the related research progress

Lithium ion batteries (Lithium - ion Battery) rely on Lithium movement between the positive and negative ions to complete charge and discharge, is a kind of high-performance batteries. Lithium ion battery "The lithium battery"

(Lithium Battery), the latter of the anode materials is manganese dioxide or thionyl chloride, the cathode is lithium battery assembly without charge after the completion of the reservoir has electricity, in the process of charging and discharging cycle to cause internal short circuit batteries, lithium crystallization and usually is prohibited from charging, therefore, should not be referred to as the "lithium ion batteries ".

Lithium will initially conceived for discharge from the 19th century American inventor Thomas Edison, he suggests, Li + MnO2 = LiMnO2 is discharge of REDOX reaction. But as a result of lithium chemical nature very lively, very tall to the requirement of processing, storage, use, so didn't get the application for a long time. In the 1980 s, bell laboratories successfully trial-produced the first available lithium-ion graphite electrode rechargeable batteries.In 1991, SONY released the first commercial lithium-ion batteries.Since lithium-ion battery technology rapid development, because of the high energy density (mass and volume than nickel cadmium or nickel metal hydride batteries of the same capacity to reduce more than 50%, the energy density of 540 ~ 720 kj/Kg), high open circuit voltage (monomer voltage from 3.3 V to 4.2 V, the equivalent of three series of nickel cadmium or nickel metal hydride batteries), big output power (300 ~ 1500 / Kg), no pollution (do not contain harmful heavy metals such as cadmium, lead, mercury), high cycle life, no memory effect, charging fast, wide working temperature range (20 ~ 60 ℃) etc, are widely used in consumer electronics, military industry,special products and other fields.With the rapid development of electric vehicle technology, lithium ion battery has become an important of electric vehicles, hybrid electric vehicle power source.It is predicted that the current lithium ion battery market scale expand 20% a year, lithium-ion batteries, a $8 billion global market in 2011, will reach $18 billion in 2020.

2. Summary of lithium ion battery fire

With the wide application of lithium ion battery, its fire hazard appeared gradually, many influential fire accidents at home and abroad, and sparked a massive recall of related products.

2.1 lithium ion battery fire and transportation field

In 2006, the United States, a Courier company a DC - 8 cargo plane from laptops use lithium ion battery is on fire, made an emergency landing at the airport, cargo fire burns for 4 h, most goods is exhausted, three crew members were injured.

In 2010, the company a Boeing 747 cargo plane crashed in dubai, loads of lithium ion battery fire reason also.To this end, the federalspecial administration (FAA) have repeatedly warned potential safety hazard in the process of lithium ion batteries by air, the international civilspecial also puts forward strict limits on transport of lithium ion battery.

2.2 fire lithium ion battery recycling field

On November 7, 2009 in Canada terrell (Trail), lithium ion battery recycling warehouse fire, is by far the greatest influence the fire accident.Fire in the warehouse is located in the Columbia river in southern British Columbia, a building area of 6500 m2, belonging to the headquarters is located in Anaheim, California, coach company (TOXCOInc.).In August 2009, the company special subsidies, receive 9.5 million dollars from the us department of energy (doe) is used to research and development of lithium ion battery recycling technology.

Fires when there are a lot of memory storage recycling lithium battery and lithium ion battery to be processed, including both small mobile phone and laptop batteries, also include the high power battery electric vehicle use.Immediately after the fire, into violent combustion phase, the local government launched a regional emergency linkage mechanism.Because of the fire, and worry about lithium reaction generated under the influence of water lithium hydroxide and hydrogen make the combustion more violent, firefighters without a large amount of water jet, just in the peripheral control, to prevent the spread of fire.Burning completely extinguished the fire until the next afternoon, caused some damage to the local environment.The cause has not decided, it is estimated that is stored in the warehouse overheated lithium battery short circuit, caused by high temperature combustion.

2.3 automotive lithium-ion battery fire danger caused high attention

As an important part to promote the development of new energy, for electric vehicles, hybrid electric vehicle technology, attaches great importance to the United States in 2015 electric car ownership is expected to reach 1 million units, the China production and sales of electric cars will reach 500000 units.Lithium-ion battery electric vehicles are the most widespread form of energy.At home and abroad in recent years, there have been several associated with lithium ion battery electric vehicle fires.

On January 7, 2010, urumqi city bus company garage a certain brand "electric double" super capacitance and lithium ion battery hybrid electric bus for iron phosphate lithium-ion battery fire fault overheating.(the car because of the coldness of the weather in December 23, 2009 incoming outage, park), 15 days after the fire.

On April 11, 2011, Hangzhou a electric fires in the process of driving a taxi, on July 18, 2011, Shanghai a spontaneous, pure electric bus is iron phosphate lithium-ion battery overheat faults.

Since May 2011, a U.S. car company in the production of electric car lithium-ion battery fire hazard, has drawn great attention of the international auto industry and fire community.

The company production of the world's first application of iron phosphate lithium-ion battery plug-in petrol-electric hybrids, by the national highway traffic safety administration (NHTSA) four front and side crash tests, get 5 star safety rating, but three weeks later on June 6, a crash test prototype within the warehouse fire, the fire in the battery compartment.Battery compartment in the process of dismantling inspection found that the collision was below the driver's seat through the lateral stiffness of components, lithium ion battery cooling fluid circulation system damage, leakage cause short circuit, causing a fire.

In September 2011, NHTSA has carried on the 5th to the car crash test no abnormalities are found, then specifically for the vehicle's lithium-ion battery pack for 6 times test, two groups of cells within a week after the crash test fire successively, the third battery arc discharge and generate fire occurs, the fourth group battery contact overheating phenomenon, with five cells appear slow discharge (confirmed after has nothing to do with the collision), 6 battery fire.

In November 2011, NHTSA jointly launched the U.S. department of energy (doe) the defects investigation into the car, in three trials have 2 demo car burst into flames.This result prompted the NHTSA launched in 2011, the special investigation of the car lithium-ion battery car company promptly adjust transverse stiffener to the scheme to protect the battery compartment and the cooling cooling liquid level sensor, around a battery pack for the sales of more than 8000 car recall.

In December 2011, the improved prototype based on collision test is not an exception occurs.

In January 2012, the U.S. house of representatives oversight committee subcommittee on economic reform commission jointly with the United States government to hold a hearing.

Announced in March 2012, the car company since that month 19, the car production 5 weeks, until April 23 to resume production.Not yet received the fire in the process of electric vehicles in the actual use report.

3. The current research of lithium ion battery fire danger of the situation

The nations have not, so far, formulate storage of lithium ion battery safety standards and fire rescue operation procedures.To fill this gap, many countries and organizations are carrying out a research into related basic theory and application of the technology.

The American association of fire protection agency (NFPA) early focus on lithium ion battery fire safety problem, and with support from the U.S. department of energy, and the American society of automotive engineers (SAE), and other agencies and companies such as general motors joint has carried out a number of research and training projects.On October 21 and 22, 2010, SAE and NFPA jointly hosted the summit, the first electric car safety standards to determine the safety standards of electric cars and hybrid vehicles three important areas: vehicles, production environment and emergency rescue, among them, the battery was placed on the primary safety problems.September 27 and 28, 2011, in the second session of the electric car safety standard summit, one of the focus is the car battery as well as the safety of the commercial transportation and storage battery, and subdivide the six key research direction:

Battery fire danger and safety performance;

Large-scale commercial storage battery to the fixed, mobile fire extinguishing system requirements;

In international transportation field about the battery shipping restrictions and assessment;

Battery destroyed after the resurgence of danger;

Battery for fire extinguishing agent;

Normal and accident situation of discharge standards.

In 2011, NFPA fire research foundation (FPRF) belongs to property insurance group (PIRG) launched the lithium ion battery storage risk and extinguishing method research.In the first phase of the study, through literature retrieval of the danger of the lithium ion battery and use of assessment is pointed out that the fire danger of lithium ion battery mainly from its structure, especially the high energy density and improper charging high temperature caused by electrolyte vaporization;At the same time, the battery design flaws and raw material defects caused by short circuit, over charge and stain, could cause a fire.Report says a thermal runaway rapid release of energy is the main cause of electrolyte burning, in the event of thermal runaway, the battery temperature rise rapidly, the result or be led directly to the battery material burning explosion, or the battery shell burst after intense oxidation reaction and exploded in the air and lithium.

Due to have carried out experiments and size is limited, don't know a great deal yet for the mechanism of thermal runaway, especially for the lithium ion battery mass characteristics of combustion and extinguishing methods still need further study.In August 2011, held a workshop PIRG, determine the next step research direction is a full-size fire simulation experiments.As the main content of the whole project research in the second stage, the focus of the study in 2012 are two kinds of lithium ion battery in large-scale storage under the condition of fire danger research: one kind is small size product, another kind is the large size can be used in electric vehicles and other products.Property insurance team will work with the American association of fire and share about the lithium ion batteries to store the research achievements of fire danger hierarchies, and in accordance with NFPA13 the automatic sprinkler system installation specification to carry out the relevant test, in order to help NFPA13 professional technical committee to determine the lithium ion battery storage space in the design of automatic fire extinguishing system parameters.

In July 2011, NFPA start the electric safety training programs, for emergency rescue personnel to carry out the training of safe disposal of the electric car accident, that the project is the U.S. department of energy (doe) on the basis of the American recovery and reinvestment act for a $4.4 million grant funding.NFPA is working with NHTSA pure electric vehicles, hybrid electric vehicle emergency disposal program, the world's major car factory participated in the related work.At present, the project has been carried out in 20 states in teacher training, education training about 800 faculty members, more than 15000 people registered to participate in the electric safety online training.NFPA is seeking emergency medical rescue and law enforcement personnel to participate in the training.

As specializing in supplies and industrial products safety performance research institutions, French industry environment and risk research institute (INERIS) was established in 2010, the electric vehicle (STEEVE) electrochemical energy storage research institutions, aims to further understand the performance of lithium ion battery, especially to grasp the mechanism of the fire.The researchers think that a full destructive test for fire risk really understand the lithium ion battery, and determine the corresponding safety measures is very necessary.STEEVE plan on June 27, 2012, held in Paris the high-risk storage protection seminar to submit its latest research report, aimed at high fire danger of dangerous goods within the storage facilities were analyzed, and the new fire safety protection measures were put forward.

In recent years, our country has carried out "lithium ion battery thermal hazard mechanism of mutation and explosion dynamics research", in order to reveal the lithium ion battery materials and their mutual kinetic and thermodynamic properties, the use of chemical kinetics, thermal analysis kinetics, thermal spontaneous combustion theory, mutation theory, explore the typical heat production law of lithium ion battery, the internal mutation pattern analysis of lithium ion battery explosion, for the development of lithium ion battery to provide the necessary scientific basis and technical support, to prevent the lithium ion battery fires have important theoretical and practical significance.

In recent years, Chinese scholars in thermal hazard, lithium ion battery materials lithium ion battery thermal runaway mechanism and prevention of lithium ion battery thermal runaway electrolyte flame retardant technology, etc, to carry out the related research.Devices such as researchers using C80 micro calorimeter, detailed study of lithium ion battery electrolyte is commonly used, the thermal stability of the anode materials are under different charging status of thermal stability, and thermal stability of the electrolyte between the positive and negative.Results show that the strong lewis acid in the electrolyte PF5 role, is the dominating factor for decreasing the thermal stability of electrolyte, LixCOo2 and its thermal stability and electrolyte coexistence system are supplied with electricity degree of increase and decrease, and the intercalated-li degree of thermal stability of electrolyte and LixC6 coexistence system.On this basis, reveals the lithium ion battery materials and their kinetic and thermodynamic properties of each other.

Researchers from the Angle of fire dynamics research, the integrated use of thermal explosion theory, chemical reaction kinetics and thermodynamics theory, combining the thermoelectric coupling between under the action of lithium ion battery materials and their chemical reaction thermodynamics and kinetics characteristics of experimental study, lithium ion batteries are analyzed, the possibility of fire and explosion, proposes the lithium ion battery fire triangle theory and battery explosion theory of Semenov.On the basis of using catastrophe theory, the explosion process of lithium ion battery, mutation analysis successfully with lithium ion battery explosion dovetail mutations.The study will fire science theory, the electrochemical theory and catastrophe theory, coupled to fully disclose the nature of the thermal runaway in lithium ion battery explosion are studied.

Studies have shown that leads to thermal runaway heat mainly comes from the internal chemical reaction heat, based on this, the laboratory system to study the three isopropyl benzene ester phosphate (IPPP) and toluene diphenyl phosphate ester (CDP), etc.) as lithium ion battery flame retardant additives for battery electrolyte, the positive, negative and whole cell performance and the influence law of thermal stability, and put forward the fire retardant agents inhibit the inner mechanism of the thermal runaway.Studies have shown that adding IPPP and CDP can not only effectively improve the safety of the lithium ion battery, and less effect on the electrochemical performance of battery, so as to improve the safety of the lithium ion battery provides a kind of way.The research for the development of lithium ion battery provides the necessary scientific basis and technical support, to prevent the lithium ion battery fire explosion has important theoretical and realistic significance.

4. Summary

With the expansion of lithium ion battery application, especially in the field of electric vehicle applications of large capacity lithium ion battery, lithium ion battery fire accident will significantly increase, to be carried out regarding the fire danger of basic research, to develop safety use, transport, recycling lithium-ion batteries, standards and procedures, and fire extinguishing technology research to carry out the efficient and practical.

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