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Park, Nankang,Jiangxi Province
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1, an overview

Nickel-cadmium (Ni-Cd) batteries contain highly toxic element cadmium has been one of the crusade against the battery of environmental protection workers object. Organizations like the EU is continuing to adopt the policies and directives ("Waste Electrical and Electronic Equipment Directive" WEEE "restrictions on the use of certain hazardous substances in electrical and electronic equipment" RoHS), but also speeded up the process of nickel-cadmium batteries battery alternative. Nickel-metal hydride (Ni-HM) batteries are the most promising alternative, how to solve the problem of performance nickel-metal hydride battery in high temperature environment is the key to its ability in larger areas. Ni-MH battery during charge and discharge process, the environment, is bound to involve the problem of temperature on battery performance and service life, high-capacity mobile power supply urgently needed by the military, aerospace, marine, petroleum, coal, geological exploration and operations, ice and mountaineering sports secondary mobile power, has a strong strategic significance of the scientific value and economic value. In addition, the nickel-hydrogen battery in the fuel cell + Ni-MH battery (electric-electric hybrid) gasoline + Ni-MH battery (hybrid), hybrid vehicles, also has important application value prospects.

Rechargeable batteries in charging and discharging process, changes in ambient temperature, battery performance impact, although all cell materials have a certain impact on battery performance, however, the high-temperature batteries, improve and optimize the positive, the negative electrode material is a better approach, with the exception of a small number of patent disclosures to improve the hydrogen storage alloy, the main technology is the cathode material, add mechanical mixing of rare earth, precious metals, alkaline earth elements, such as battery cathode material formulations, such as of Mg, Ca, Sr, Sc, Y, La, lanthanides, Ti, Zr, and Cr, Mo,, W, Mn and Fe, Co. and Cu and Zn in and Cd in, B,, Al, Ga, In, Si, P, As, Sb, Bi one or more of oxides, hydroxides. Cathode ingredients several different nature of the material is difficult to achieve completely uniform, so consider using in the manufacture of spherical nickel hydroxide coprecipitation doping these elements, consider the spherical nickel hydroxide coated with a layer of the above elements.

Although the above are several ways to play a role in improving the high temperature battery performance, there are still many gaps and lack of reduced battery performance, first, to improve the internal structure of the ball nickel, to prevent the generation of γ-of NiOOH hope β-NiOOH with β-Ni (OH) 2 charge-discharge conversion easy (γ-NiOOH layer spacing is 0.69nm, β-Ni (OH) 2 crystal layer spacing of approximately 0.46nm, β-of NiOOH crystal layer spacing of approximately 0.48nm. caused by the presence of γ-NiOOH electrode expansion of the active material losses, lower conductivity, severely reducing the electrode cycle life and efficiency); another way is to add conductive material to improve conductivity by adding CoO or Co (OH) 2. However, the cobalt hydroxide as a raw material powder in the process of charging and discharging, while dissolved in an alkaline aqueous solution, while again precipitate and drastic structural change occurs, part of the cobalt compound free, resulting in the cobalt content changes result in reduced battery performance. Although the coated ball Nickel for the above phenomenon has been some improvement, but there are still coated too weak to charge and discharge the surface layer dissolved and the shedding phenomenon.

Functionally gradient materials (Functionary Gradient Materials, FGM) is a maceral structure, performance ladder changes in high-performance materials. Has high mechanical strength, thermal shock, high temperature performance characteristics. Wide range of applications in electronic components, artificial teeth, car engines, brakes, chemical parts. The authors believe that combining the principle of graded materials with ball Nickel manufacturing will become the development trend of high-temperature battery cathode material.

2, high temperature nickel-metal hydride batteries key technologies

2.1, the cathode materials for improved

2.1.1, the cathode materials for mechanical mixing

Added by mechanical mixing ingredients in the battery the periodic table in II A, III B, IV B, VII B and VIII of B, Ⅱ B main group elements, and 3,4,5-cycle elements, oxides or hydroxides, is able to improve or improved high temperature performance of nickel-metal hydride. The world famous battery manufacturing company in China to apply for authorization of the patent in more than described, such as Japan's Panasonic, Sanyo; BYD; Germany HC Shi Take. Details as follows:

2.1.2, the cathode materials for chemical coprecipitation

These elements in the cathode material of spherical nickel hydroxide production process, the use of doping to the layered structure of nickel hydroxide, to replace part of the nickel ions to form a solid solution, and make better uniformity between elements; outside of the spherical nickel hydroxide package overlying layer of cobalt hydroxide, etc., for improving the overall performance of the battery, both improved functionality. Representative of the patent as follows:

Improvement of 2.2, the anode material

Ni-MH battery anode material for hydrogen storage alloy, the main elements for M (NiCoMnAl) 5, ie, the AB5. M is a rare earth of La, of Ce, Pr and Nd.

Liu Huafu of chemical formula for Mm0.95 to 1.05Ni4.08 ~ 4.40Co0.38 ~~ 0.95Mn0.25 ~ 0.399Al0.32 ~~ 0.49M0.04 ~ 0.999, of Mm as lanthanum, cerium, praseodymium, neodymium rare earth alloy, M vanadium, bismuth, iron, gallium, zinc, silicon, boron, tungsten, molybdenum, chromium, titanium, lithium, tin, copper and one of the two kinds of element or three element or four elements. For the MH-Ni secondary battery. Fast charging, and has a high electrochemical capacity of hydrogen storage alloy in high temperature conditions.

Li Rong et al. Anode material composition (atomic%) as follows: the AB5, composed of high-temperature nickel-metal hydride battery anode material, A for La, Ce, Pr, Nd, Y element; B, Ni, Co, Mn, Al elements;

Sichuan University has developed excellent low-temperature hydrogen storage alloy, Ni-MH battery manufacturing technology with the distinctive, prepared rated capacity 8Ah D-type Ni-MH battery. The battery 18 the Ministry of Information Industry, Tianjin, Changhong power company, Jianzhong lithium battery factory in Chengdu and Sichuan University's own testing found: performance at room temperature is 0.2C capacity 9.2Ah capacity 9.0Ah, 1C, its high rate capability of about 98%, small current (0.2C ~ 0.4C) charge-discharge cycle life greater than 500, 1C high-current charge-discharge cycle life of more than 300 times at room temperature to set aside 28 days of self-discharge is less than 10%; low temperature performance at -40 ℃. 0.2C and -40 ° C, 0.4C under the conditions of the discharge capacity reaches 80% of rated capacity at -45 ℃, 0.2C under the conditions of the discharge capacity reaches 70% of the rated capacity; high temperature performance of 55 ° C / 0.2C charge for 6.5 hours , 0.2C discharge capacity is greater than the rated capacity of 90%, 55 ℃ leave it for 8 hours 0.2C discharge, the discharge capacity is greater than the actual capacity of 90%, 50 ° C storage capacity of 30 days no any loss. Under the leadership of Academician Tu Mingjing, prior to the Materials Institute of Sichuan University doctoral tutor Professor Chen Yungui presided over the completion of the development of neodymium-free nickel-hydrogen battery, a leading performance in the major brand batteries at home and abroad against the test, obtained four national invention patents, and 2003 Top Ten Technology of the Chinese Rare Earth News is one of honor. Tu Mingjing Academy of Sciences and Professor Chen Yungui is actively promoting this excellent performance, wide temperature nickel metal hydride batteries to start the aircraft excellent low-temperature high-current discharge performance of Ni-MH turn on the power and electric vehicles with large temperature, long life and low-cost nickel the development of hydrogen battery [1].

Doping diffusion coating gradient composite of spherical nickel hydroxide

Spherical nickel hydroxide industrialization of more than 10 years of experience, doped Cd + Co, cobalt-doped Zn + Co ball Nickel commercialization of more mature package (or follow-cobalt) is gradually moving toward commercialization. That some people say [2] "β-Ni (OH) 2 development has reached the limit; nanometer of Ni (OH) 2 and α-Ni (OH) 2 materials research and development prospects will be very broad.

Functionally Gradient Materials (Functionally Gradient Materials, referred to as FGM) is a new type of functional response to the needs of the modern aerospace industry and other high-tech fields, developed to meet the repeated normal work under extreme conditions (ultra-high temperature, large temperature drop) materials [3]. International composite functional materials to develop the field of cutting-edge technology.

Dopant diffusion coating gradient composite spherical nickel hydroxide should be divided into two concepts:

A doped spherical nickel hydroxide, it is in the traditional doped Cd + Co and doped Zn + Co ball nickel base, optimize the II group elements, rare earth elements, preparation of a uniform composition and microstructure of the grain size interlayer spacing, FWHM larger doping, surface area and particle size distribution to meet the requirements, quality and stability of spherical nickel hydroxide. In this regard, the authors believe that the developed system microcrystalline online triple Control Act ", product stability, uniformity; the process again to control the ease of parameter precision Reliability; low investment in equipment and overall cost in domestic leading position. Matsushita Battery bulk supply, the product of nearly 1000 tons, with no quality complaints, the first of its kind to create a similar domestic products [4] [5].

Gradient composite of spherical nickel hydroxide, which ball nickel package cobalt are similar, but there are a lot of difference. Package nickel cobalt ball is simply the deposition of spherical nickel hydroxide coated single layer of cobalt hydroxide; gradient composite of spherical nickel hydroxide is For permeability materials (cobalt, yttrium, titanium, calcium, magnesium, or other rare earth elements) with the repair material (doped spherical nickel) were kept in tightly controlled conditions, the diffusion coating ion and hydroxyl gathered in the role of additives in the substrate (ion doped surface of the ball Nickel) continue along the substrate the rapid diffusion of crystal defects within the matrix. For alloying elements enrichment on the substrate surface crystallization, and finally the formation penetrate a certain depth to the base body outside to the inside, For the infiltration element concentration gradient descent, gradient changes in its organizational structure, the formation of the substrate the outer surface with desire infiltration the performance of metal substrates heart still maintain the original performance, the performance gradually over the middle layer of functionally gradient materials. Densification of the components of continuous changes in the gradient diffusion coating material and the substrate with a solid manufacturing into a diffusion coating material and the substrate in the reaction of the cell materials do not come off easily, to ensure the battery cycle performance life consistency to your selection. II group elements , rare earth elements were prepared by doping diffusion coating gradient composite of spherical nickel hydroxide to obtain the effect of high temperature nickel-metal hydride battery.

4, Conclusions

Nickel-metal hydride battery cathode ingredients, add the rare earth, rare and alkaline earth element or oxide, can improve the performance of nickel-metal hydride battery in high temperature state, of which the representative elements: that of Mg, Ca, Sr., of Sc, Y, and of La, La Department of elements Ti, Zr, and Cr, Mo,, W, Mn and Fe, Co., of Cu, Zn, Cd, B, Al, Ga, In, Si, P, As, Sb, and Bi in one or more oxides , hydroxides. Which zirconium in the new energy materials research applications there are many introduced [6] [7] [8] In addition to the zirconium in nuclear power plants (nuclear, zirconium plate, pipe) the industrialization of the practical application outside of the other nickel-metal hydride positive and negative materials and lithium battery cathode material additives do not yet have the practical application of the industry. The mechanical mixing surface mixing uniformity problems which could affect performance; chemical precipitation doping, coating has certain advantages over mechanical mixing, there are still the technology of production and process control; doped diffusion coating gradient composite of spherical nickel hydroxide may solve the above defects in an effective way.