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<title> At present lithium-ion batteries have become the cell phones, laptop computers and other mobile electronic devices, basic equipment supply, but also has begun to apply to light electric vehicles and hybrid electric vehicles. However, due to rapid demand growth in the cost of lithium-ion batteries become increasingly prominent, due to the improvement of energy density batteries, battery safety accidents have also been reported. Lithium-ion battery industry is currently an imminent major adjustment of the structure, dynamics and energy storage cell associated with the industrialization of materials, processes and equipment to the major technological innovations direction.
Using a variety of ways to increase security
Involving the safety of the battery material, battery design, manufacture and application in many aspects, simply change the cathode material can not completely guarantee the safety of the battery. Only the main material is necessary to carefully select the anode material, electrolyte and battery separator, such as a lithium-ion battery anode materials are carbon materials, metal oxides and alloys, graphite material is still today a major lithium-ion battery anode material, However, its safety performance than the hard carbon materials, while the spinel lithium titanate anode material has a higher security. May be resistant to higher temperatures using a new electrolyte membrane and processing of flame retardants is to improve the safety of Dell INSPIRON 8000 Laptop Battery techniques.
Affect the safety of lithium-ion batteries are a major factor in battery electrode materials, electrolytes and manufacturing processes and use conditions. A cell phone used in lithium-ion battery weighing about 20 grams, the basic requirement is that the probability of security incidents occurred less than one in a million, which is acceptable to the public the minimum standards, the reality is even more than 1/10000000 small. Electric bicycle lithium-ion battery packs used in the weight of 3 kg to 4 kg, 100 times bigger than a cell phone, pure electric cars will use 300 kg to 400 kg of batteries, as electric bus, or the weight of the battery electric trucks will be is 1500 kg and 2000 kg, even more "mobile phone" 75,000 times the ~ 100000 times. As the battery capacity increases, the possibility of a significant increase in security incidents. Therefore, the power battery made of lithium-ion batteries, it must improve its safety performance, the greater the single cell, asking for security indexes also higher. Such as the commonly used in mobile phone batteries in use lithium cobalt oxide and graphite as a lithium-ion battery anode material for the positive, the battery large-scale post-licensure safety will not be guaranteed.
China started to carry out research and development lithium-ion battery electric vehicles when there have been a number of explosions and burning accidents, one of the main reason is that the use of mobile phone batteries are usually used in lithium cobalt oxide as cathode material for batteries. Then search for alternative cathode material for lithium cobalt oxide to address the security issues is the driving force-type lithium-ion battery R & D a top priority issue. China's high-power lithium-ion battery safety issues in the "Tenth Five-Year" period, has been a better solution. Using modified lithium manganese oxide cathode materials, reduces the nature of the content of active lithium cobalt acid lithium than low. Japan's mass-produced lithium manganese battery capacity of small monomer, such as publicly reported for the 3000 Tokyo Electric Power car battery for the 216 13Ah lithium manganese batteries.
Lithium iron phosphate as cathode to do a better safety
On the cathode, the lithium iron phosphate (LiFePO4) Charge-state thermal stability of high oxidation capacity of the electrolyte is low, with better security, can be used to make a larger battery. LiFePO4 theoretical capacity of 170 mAh / g, relative to the lithium metal voltage of 3.5V, made of materials, the actual reversible capacities greater than 160 mAh / g. Compared with other materials, lithium-ion in the chemical diffusion coefficient of LiFePO4 lower electronic conductivity at room temperature is far below that of other cathode materials, the need by reducing the material size, coated with conductive agent means to enhance the material properties and the realization of applications brought the defect is low density, the volume is too large and electrolyte battery usage more. The current research focus is to develop new lithium iron phosphate synthesis methods and the material was modified to improve the overall performance of lithium iron phosphate.
The first synthesis of lithium iron phosphate JB Goodenough way to solid-phase reaction. This method is simple and convenient, easy to operate, a longer cycle of disadvantage is that synthetic products were difficult to control the stability of the batch. How to heat treatment and powder processing, the process to prevent the oxidation of divalent iron is the synthesis of critical control points. There are a lot of R & D team developed the carbon-thermal reduction method, co-precipitation, hydrothermal method, spray pyrolysis method.
At present the international community can produce lithium iron phosphate enterprises Valence, A123, Phostech so. Lithium iron phosphate under way in the development of industrial enterprises are also a lot. According to the Internet survey, 80% of domestic well-known cathode materials for lithium battery suppliers of foreign claims that its lithium iron phosphate during development and production of related products. And the "international professional players," contrast, from the investment in R & D intensity and time point of view, is still in its early stages.
Compared to other lithium battery material, lithium iron phosphate is still very young. Some people say that the battery used in electric tools, it was said that it would apply to electric bus batteries, the initial opening up is the need to be encouraged.
Japan in the field of lithium-ion battery has a monopoly, Sony, Sanyo Electric, Matsushita Battery, NEC and other famous companies have built large-scale lithium-ion battery production line, but most manufacturers in addition to maintaining and expanding the production of the original brand, the all use their own advantages to develop lithium-ion battery of new products. Japan's New Sunshine Program since 1992 to start vehicle lithium-ion battery development plans, R & D funds invested over one billion U.S. dollars, access to technology and technological breakthroughs. Toyota has recently begun mass production of lithium-ion rechargeable battery, in February 2003 for the listing of a small car "Vitz" part of the model, the stability to withstand the test of the market. Hitachi, NEC, Mitsubishi and other companies producing lithium-ion batteries used in electric vehicles and hybrid bulk electric vehicles, Fuji Heavy Industries, Tokyo Electric Power Design for the introduction of use of lithium manganese oxide cathode materials for SONY PCGA-BP2NX Laptop Battery electric vehicle "R1e", fast charging mode, 15 minutes can be filled with 80% of the charge may be moving around a sub-80km. Maximum speed of 100km / h. Tokyo Electric Power in 2006 and then into 30 year R1e. In addition, since 2007 to import a total of about 3000. Overall, Japan remains the leading countries power battery technology, its power batteries and their mass production of key materials technology has matured, the performance has almost meet the demand for electric vehicles.
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