Digital battery

Carbon-Lithium Iron phosphate coating as effectively improve the performance of the method is now more and more attention. FRU 92P1141 40Y6799 Researchers have begun a systematic study of different carbon sources, carbon-coated layer of the composition of the thick layer of carbon coating on the effects of electrochemical properties of lithium iron phosphate. Zhao, Zhejiang University, recruits, etc. [33, 34] using polypropylene as an alternative to toner source of inorganic carbon, respectively FePO4 source of iron and Fe2O3 via solid state synthesis reaction step of LiFePO4 / Composites C, the results of research show that the decomposition at high temperature polypropylene carbon to effectively prevent the aggregation of grains LiFePO4 grew up in different Fe3 + iron source to be the product of the powder are slightly ball, the difference is very Small form, particle size of 300 ~ 600nm between the initial discharge capacity of both the difference is not large, was 160 mAh / g (0.1C) or so. Zhao advantage of this approach are summarized in [34]: the decomposition of polymer products (state of the H atom and C) have a stronger reduction of the state of carbon materials, which can reduce the temperature Synthesis and shorten the reaction time, polymerization decomposition of carbon atoms in the reaction system the state level has been decentralized, thereby achieving a uniform coating of synthetic products, and the formation of particles connected with each Other films of conductive carbon, solid-phase synthesis in the carbon film coated in situ reduces the particles of lithium iron phosphate has grown in speed, thus contributing to the particle size of cathode material for effective control. Doeff, etc. [35, 36] NF343 G1947 studied the different sources of carbon and the carbon coating in situ on the structure of the surface layer on the electrochemical performance of LiFePO4, they think of carbon fiber and carbon nanotubes can significantly improve the performance of lithium iron phosphate, LiFePO4 / C composite material performance also depends on the structure rather than the content of carbon and its electrochemical performance is strongly dependent on the surface of the carbon layer of carbon and graphite disordered in the proportion of parts in carbon, graphite carbon materials with high magnification report better performance, and As the conductivity of carbon graphite sp2 hybridization of carbon sp3 hybrid and electric is higher than the conductivity of carbon disordered, so that the electrochemical performance of LiFePO4 with the coating layer of carbon in the ratio of SP2/SP3 positive correlation, Figure 2 for LiFePO4 / C composite material and structure of carbon materials, the relationship between the electrical conductivity. Dominkó, etc. [37] using Sol - gel prepared with different thicknesses of the layer of porous carbon, crystallization good LiFePO4 / C content of carbon composites and the relationship between the thickness of the layer of carbon coated and found that the thickness of the coated carbon increases the carbon content (from 1nm to 10nm), the carbon content of 3.2% (for coated thick layer of carbon about 1 nm), the lens exit 1C of their specific capacity of approximately 140mAh / g. PB994A PP2182D

 

4. Important synthetic route of progress and industrialization

 

Materials of lithium iron phosphate, the synthesis methods can be divided into solid phase method and liquid phase chemical method in the very process of industrial production is generally the introduction of ball-milling, spray or freeze-drying [38], and granulation, crushing and screening or air and other means of improving process capability.

 

Synthesis of lithium iron phosphate of the track may be used by different sources of iron, or ferrous salt as a source of iron, ferrous salinization legitimate “and” source of law of ferric iron compounds. “Source of iron the ferrous salt in the solid state sintering method of typical materials include oxalate, ferrous Li2CO3 and NH4H2PO4 or (NH4) 2HPO4 [4], a mixture of raw materials under the inert gas after sintering; ferric phase method solid source approach Sony in Valencia, and represented the source of iron oxide or iron phosphate, Shanghai Jiaotong University, MA Zi-Feng et al [39] also made a similar Sony, with phosphate ferric iron as a source of great ball milling energy. Process solid phase is characterized by the process intuitive and quality of the material capacity and volume ratio were greater than the capacity, the production process can achieve ultra low emissions. However, solid phase method difficult to measure the precise chemical control of raw materials, process route selection is important for the requirements of process control are very high. Valencia is the successful adoption of the method solid phase to achieve the industrialization of a typical representative of the society around the “CTR” means to apply a large number of patents phosphate material. PA3191U-4BRS  PA3285U-1BRS

 

Liquid-phase chemical methods generally adopt the “legal ferrous salt, are synthetic carbon-coated lithium iron phosphate doped sub-micron and Nano-particles effective means of common methods of liquid phase chemical synthesis are essentially the hydrothermal method [ 12, 40 -42], Solvothermal [43], the gel - sol-gel method [37, 44], the method of co-precipitation [45] and so on. By the hydrothermal synthesis method, for example, use generally LiOHH2O, H3PO4 and water-soluble ferrous salt (as FeSO4) as the precursor, the reaction at low temperature hydrothermal by a number of hours LiFePO4 direct synthesis. reaction conditions Liquid-phase synthesis of the advantages of low temperature (low energy), flexible and controllable, the product structure of homogeneous composition (a small amount of synthesis) can be synthesized nano-particles, disadvantage is that when production equipment to large scale, demanding, not easy controlling the oxidation of ferrous ions is not easy to achieve a real sense of the wording of the measure chemicals, materials, performance and stability, not easy to control the batch, and easy to produce programs pollutants and sewage. For the gel - sol-gel, it is reaction time is too long Er Shi has seriously reduced the productivity problem. Methods of synthesis in liquid phase there is an obvious disadvantage is that synthetic materials, press on the density below the capacity of the small volume of material, the battery manufacturing process, the transformation of matter is very difficult (mixing and embedding). Hydro-Quebec is a typical representative of chemical methods in liquid phase, materials , particles of lithium iron phosphate in a particle diameter of 50 ~ 250 nm between the magnification of the 1C discharge capacity at room temperature is higher than 140mAh / g, 60 ℃ under 0.25C/1C charge and discharge 400 times the capacity retention rate from 98.2% [46]. PA3468U-1ACA PA3097U-1ACA

 

To date, reported publicly have large volumes of manufacture of phosphate lithium iron-based cathode materials for lithium-ion batteries the company of only two U.S. companies Valence Technology [47] and A123systems [48]. The first claim is the first commercial company to iron phosphate lithium battery, which says that its nano-phosphate batteries with features ultra-high power is now the company has received Sequoia Capital, General Electric, Motorola, Qualcomm and d other companies 1.5 100 million U.S. dollars of investment products, including batteries of professional power tools, HEV (Hybrid Electric Vehicle) Battery, PHEV (Plug-in) battery and the BEV (battery EV) battery. In Japan NTT, Mitsui has also actively developed the lithium iron phosphate material [49]. Mainland China and Taiwan, as some manufacturers to join the ranks of the evolution of material, some manufacturers have made progress [50-52]. PPP012L F1781A

 

5 Conclusion

 

Intrinsically safe, non toxic, greener, rich in raw materials, high performance lithium-ion battery cathode material lithium iron phosphate lithium-ion battery materials is to achieve from mobile phones, laptops and other applications small scale through professional power tools, emergency power, light electric vehicles, hybrid electric vehicles, energy storage, and other large aerospace applications to important documents. To overcome the low conductivity of the material to bring the application of the barrier, the researchers of materials, including nano-based particles, the surface coated with carbon and a large number of body modification such as doping, and d ‘try a variety of effective synthetic methods for controlling material performance. The success of the industrialization of U.S. companies will quickly drive the internal material lithium iron phosphate and related industries. PA3396U-1ACA PA3467U-1ACA