Fire hazards of lithium-ion batteries and related research progress

　　The company’s world’s first plug-in hybrid electric vehicle using lithium iron phosphate batteries has passed four frontal and side impact tests by the National Highway Traffic Safety Administration (NHTSA) and has received a five-star safety rating. Three weeks later, on June 6, a crash test prototype caught fire in the warehouse, and the fire was in the battery compartment. The disassembly inspection found that the battery compartment was penetrated by the transverse rigid member under the driver's seat during the collision, causing damage to the lithium-ion battery coolant circulation system, leakage and short circuit, causing a fire.

　　Lithium-ion battery (Lithium-ionBattery) relies on the movement of lithium ions between the positive electrode and the negative electrode to complete charging and discharging. It is a high-performance rechargeable battery. Lithium-ion batteries are different from "lithium batteries" 　　 (LithiumBattery). The anode material of the latter is manganese dioxide or thionyl chloride, and the anode is lithium. After the battery is assembled, it can store electrical energy without charging, and it is easy to charge and discharge. Lithium crystals are formed and short-circuit inside the battery. In general, charging is prohibited. Therefore, lithium-ion batteries should not be referred to as "lithium batteries" for short.　　The original idea of using lithium for discharge originated from the 19th century American inventor Edison, who proposed that Li+MnO2=LiMnO2 is the redox reaction of discharge. However, due to its very active chemical properties and very high requirements for processing, storage and use, lithium has not been used for a long time. In the 1980s, Bell Laboratories successfully trial-produced the first usable lithium-ion graphite electrode rechargeable battery. In 1991, Sony released the first commercial lithium-ion battery. Since then, lithium-ion battery technology has developed rapidly, due to its high energy density (the mass and volume are more than 50% less than the nickel-cadmium or nickel-hydrogen battery of the same capacity, and the energy density is 540~720KJ/Kg), and the open circuit voltage is high (the single working voltage is 3.3 ~4.2V, equivalent to 3 nickel-cadmium or nickel-metal hydride batteries connected in series), high output power (300~1500/Kg), no pollution (not including cadmium, lead, mercury and other harmful heavy metal substances), high cycle life, no The advantages of memory effect, fast charging, and wide operating temperature range (-20~60℃) are widely used in consumer electronics, military products, aviation products and other fields. With the rapid development of electric vehicle technology, lithium-ion batteries have become an important source of power for electric vehicles and hybrid vehicles. According to forecasts, the current lithium-ion battery market is expanding by 20% every year. In 2011, the global market for lithium-ion batteries will reach US$8 billion and will reach US$18 billion in 2020.　　2. Overview of lithium-ion battery fires　　With the widespread use of lithium-ion batteries, their fire hazards have gradually emerged. There have been many influential fire accidents at home and abroad, and large-scale recalls of related products have occurred. 2.1 Lithium-ion battery use and fire in the transportation field In 2006, a DC-8 cargo plane of a certain express company in the United States caught fire due to the lithium-ion batteries used in the transportation of laptops. It made an emergency landing at the airport. Three crew members were injured.　　 In 2010, a Boeing 747 cargo plane of the company crashed in Dubai. The cause was also the fire of the lithium-ion battery loaded. For this reason, the US Federal Aviation Administration (FAA) has repeatedly issued warnings on the safety hazards during the air transportation of lithium-ion batteries, and the international civil aviation industry has also put forward strict restrictions on the transportation of lithium-ion batteries.　　2.2 Fire in the field of lithium-ion battery recycling 　　The fire in the lithium-ion battery recycling warehouse in Trail, Canada, on November 7, 2009, is the most influential fire accident of this type so far. The warehouse where the fire broke out is located on the Columbia River in southern British Columbia, with a construction area of 6,500 square meters. It belongs to TOXCO Inc., headquartered in Anaheim, California, USA. In August 2009, the company received a special subsidy of US$9.5 million from the US Department of Energy for the research and development of lithium-ion battery recycling technology.　　 At the time of the fire, there were a large number of lithium batteries and lithium-ion batteries that were collected for disposal in the warehouse, including small mobile phones and laptop batteries, as well as high-power batteries used in electric vehicles. After the fire broke out, it quickly entered a violent burning stage, and the local government initiated a regional emergency response mechanism. Due to the fierce fire and the fear that lithium reacts with water to produce lithium hydroxide and hydrogen, the combustion will be more violent. The fire was not completely extinguished until the next afternoon, causing some damage to the local environment. The cause of the fire has not been determined. It is estimated that the lithium batteries stored in the warehouse were short-circuited and overheated and caused by high-temperature combustion. 2.3 The fire hazard of automotive lithium-ion batteries has attracted high attention. As an important part of promoting the development of new energy, countries attach great importance to the technology of electric vehicles and hybrid electric vehicles. It is estimated that the number of electric vehicles in the United States will reach 1 million in 2015. Sales of electric vehicles will also reach 500,000. Lithium-ion batteries are the most widely used form of energy for electric vehicles. In recent years, there have been many electric vehicle fires related to lithium-ion batteries at home and abroad.　　 On January 7, 2010, a certain brand of "dual-electric" super capacitor and lithium-ion battery hybrid pure electric bus in the garage of Urumqi City Public Transport Company broke out due to overheating of the lithium iron phosphate battery. (The car was shut down due to cold weather on December 23, 2009, and it caught fire after being parked for 15 days).