Nickel Metal Hydride No. 5 battery.Key technologies related to high-temperature nickel-metal hydride batteries

Nickel-cadmium (Ni-Cd) batteries have always been one of the targets of environmental protection workers because they contain the highly toxic element cadmium.

1. Overview Nickel-cadmium (Ni-Cd) batteries have always been one of the batteries targeted by environmental protection workers because they contain the highly toxic element cadmium. Organizations such as the European Union continue to issue policies and directives (the "Waste Electrical and Electronic Equipment Directive" WEEE and the "Directive on the Restriction of the Use of Certain Hazardous Substances in Electronic and Electrical Equipment" RoHS), which has accelerated the process of replacing nickel-cadmium batteries with other batteries. Nickel-metal hydride (Ni-HM) batteries are the most promising alternative. How to solve the performance problems of Ni-MH batteries in high-temperature environments is the key to their application in wider areas. The charging and discharging process and use environment of nickel-metal hydride batteries inevitably involve the impact of temperature on battery performance and service life. High-capacity mobile power supplies, special aerospace, navigation, petroleum, coal, geological exploration and operations, and ice are urgently needed by the military. The secondary mobile power supply used in mountaineering and mountaineering sports projects has strong strategic significance, scientific value and economic value. In addition, nickel-metal hydride power batteries also have important application prospects in hybrid vehicles such as fuel cells + nickel-metal hydride batteries (electric-electric hybrid) and gasoline + nickel-metal hydride batteries (gas-electric hybrid). During the charging and discharging process of rechargeable batteries, changes in ambient temperature, etc., have an impact on battery performance. Although all battery materials have a certain impact on battery performance, as far as high-temperature batteries are concerned, improving and optimizing positive and negative electrode materials is a A better method, except for a few patents disclosing improvements to hydrogen storage alloys, is that the main technology lies in the cathode material, including the use of mechanical mixing methods to add rare earths, rare metals, alkaline earth elements, etc., such as Mg, Ca, etc. to the battery cathode material formula. Sr, Sc, Y, La, lanthanides, Ti, Zr, Cr, Mo, W, Mn, Fe, Co, Cu, Zn, Cd, B, Al, Ga, In, Si, P, As, Sb, Bi one or more oxides and hydroxides. Since it is difficult to achieve complete uniformity of several materials with different properties when batching the positive electrode, it is considered to use co-precipitation doping with the above elements when making spherical nickel hydroxide, and it is also considered to coat the spherical nickel with a layer of hydroxide of the above elements. Although the above methods have played a certain role in improving the performance of high-temperature batteries, there are still many shortcomings and deficiencies. The main method to solve the problem of reduced battery performance is to improve the internal structure of spherical nickel to prevent the production of γ-NiOOH and hope for β-NiOOH. It can be easily converted when charging and discharging with β-Ni(OH)2 (γ-NiOOH layer spacing is 0.69nm, β-Ni(OH)2 crystal layer spacing is about 0.46nm, β-NiOOH crystal layer spacing is about 0.48nm, The presence of γ-NiOOH causes the electrode to expand, resulting in the loss of active materials and reduced conductivity, seriously reducing the cycle life and efficiency of the electrode); another method is to add conductive materials to improve conductivity, adding CoO or Co(OH)2. However, during the charging and discharging process, the cobalt hydroxide as raw material powder dissolves in the alkaline aqueous solution and precipitates again, and undergoes rapid structural changes. Some cobalt compounds are free, causing changes in the amount of cobalt and reducing battery performance. Although the coated nickel ball has improved the above phenomenon to some extent, there is still a phenomenon that the coating is not strong enough and the surface layer dissolves and falls off after charging and discharging. Functional Gradient Materials (FGM) is a high-performance material with step-change changes in microscopic composition, structure, and performance. It has the characteristics of high mechanical strength, thermal shock resistance, and high temperature resistance. It is widely used in electronic components, artificial teeth, automobile engines, brakes, chemical components, etc. The author believes that combining the principles of gradient materials with spherical nickel manufacturing will become the development trend of high-temperature battery cathode materials. 2. Key technologies of high-temperature nickel-metal hydride batteries 2.1. Improvement of cathode materials 2.1.1. Mechanical mixing method of cathode materials. During battery batching, the main group elements of IIA, IIIB, IVB, VIIB, VIIIB, and IIB in the periodic table are added through the mechanical mixing method. And elements, oxides or hydroxides of periods 3, 4 and 5 can better improve or improve the high temperature performance of nickel metal hydride. Many of the patents applied for authorization by world-famous battery manufacturing companies in China are introduced, such as Japan's Panasonic and Sanyo; China's BYD; Germany's H.C. Stark and other companies. 2.2. Improvement of negative electrode material The negative electrode material of nickel-metal hydride battery adopts hydrogen storage alloy, and the main component element is M(NiCoMnAl)5, which is AB5. M is rare earth La, Ce, Pr, Nd. Liu Huafu adopts a chemical formula composed of Mm0.95～1.05Ni4.08～4.40Co0.38～0.95Mn0.25～0.399Al0.32～0.49M0.04～0.999, Mm is a rare earth alloy of lanthanum, cerium, praseodymium and neodymium, M It is two elements, three elements or four elements among vanadium, bismuth, iron, gallium, zinc, silicon, boron, tungsten, molybdenum, chromium, titanium, lithium, tin and copper. Used for MH-Ni secondary batteries. A hydrogen storage alloy material that can be charged quickly under high temperature conditions and has high electrochemical capacity. The composition (atomic %) of the negative electrode material by Li Rong and others is: AB5. In the negative electrode material for high-temperature nickel-hydrogen batteries, A is La, Ce, Pr, Nd, and Y elements; B is Ni, Co, Mn, and Al. Element; Sichuan University has developed a low-temperature hydrogen storage alloy with excellent performance, and combined with the unique nickel-metal hydride battery manufacturing technology, a D-type nickel-metal hydride battery with a rated capacity of 8Ah has been prepared. The battery has been tested by the Tianjin 18th Institute of the Ministry of Information Industry, Changhong Power Supply Company, Chengdu Jianzhong Lithium Battery Factory and Sichuan University itself and found that the normal temperature performance is 0.2C capacity 9.2Ah, 1C capacity 9.0Ah, and its high rate performance is about 98%. The low current (0.2C~0.4C) charge and discharge cycle life is more than 500 times, the 1C high current charge and discharge cycle life is more than 300 times, the self-discharge after being left at room temperature for 28 days is less than 10%; the low temperature performance is -40℃, 0.2C and The discharge capacity reaches 80% of the rated capacity under the conditions of -40℃ and 0.4C, and the discharge capacity reaches 70% of the rated capacity under the conditions of -45℃ and 0.2C. The high temperature performance is 55℃/0.2C. After charging for 6.5 hours, 0.2C The discharge capacity is greater than 90% of the rated capacity. After being discharged at 0.2C for 8 hours at 55°C, the discharge capacity is greater than 90% of the actual capacity. No loss of capacity is seen after 30 days of storage at 50°C. Under the leadership of Academician Tu Mingjing, Professor Chen Yungui, the former doctoral supervisor of the School of Materials of Sichuan University, presided over the development of neodymium-free nickel-hydrogen power batteries. Its comprehensive performance is in the lead in the confrontation test of major domestic and foreign brand batteries, and has won the Four national invention patent authorizations and the honor of being one of the top ten rare earth science and technology news in China in 2003. Academician Tu Mingjing and Professor Chen Yungui are actively promoting this wide-temperature nickel-hydrogen battery with excellent performance, developing nickel-hydrogen starting power supplies with excellent low-temperature and high-current discharge performance for aircraft and wide-temperature, long-life and low-cost nickel nickel batteries for electric vehicles. Development of hydrogen batteries [1]. 3. Doping and plating gradient composite spherical nickel hydroxide has more than ten years of experience in the industrialization of spherical nickel hydroxide. The commercialization of doped Cd+Co and doped Zn+Co spherical nickel is relatively mature. Cobalt-coated (or cobalt-coated) ) is gradually moving towards commercialization. So much so that some people say [2] "The current development of β-Ni(OH)2 is close to the limit; the research and development prospects of nano-Ni(OH)2 and α-Ni(OH)2 materials will be very broad." Functionally Gradient Materials (FGM) is a new type of functional material developed in response to the needs of high-tech fields such as modern aerospace special industries and to meet the requirements of repeated normal operation in extreme environments (ultra-high temperatures, large temperature differences) [ 3]. It is currently the main development frontier technology field of international composite functional materials. Doped infiltration plating gradient composite spherical nickel hydroxide should be divided into two concepts: 1. Doped spherical nickel hydroxide, which is based on the traditional doped Cd+Co and doped Zn+Co spherical nickel, optimized selection II Group elements, rare earth elements, etc., to prepare spherical nickel hydroxide with uniform composition, small microstructure grain size, large interlayer spacing, large half-height width, specific surface area and particle size distribution that meet the requirements, and stable quality. In this regard, the author believes that the "system microcrystal online three-dimensional control method" developed by him is at a leading level in terms of product stability and uniformity; ease of process re-online control, precision and reliability of parameters; low equipment investment and overall product cost. Domestic leading position. There was not a single quality complaint among the nearly 1,000 tons of products supplied to Panasonic Battery Company in batches for one year, which was the first of its kind in China [4][5]. 2. Gradient composite spherical nickel hydroxide is similar to the current cobalt-coated spherical nickel, but it is also very different. Cobalt-coated spherical nickel is simply deposited and coated with a single layer of cobalt hydroxide in spherical nickel hydroxide; gradient composite spherical nickel hydroxide is made by adding the material to be infiltrated (cobalt, yttrium, titanium, calcium, magnesium or other rare earth elements) The material to be repaired (doped spherical nickel) is placed under strictly controlled conditions. The plating ions and hydroxides gather on the surface of the base material (doped spherical nickel) under the action of additives. The ions continue to move along the surface of the base material. Crystal defects diffuse rapidly into the matrix. Finally, the metal elements to be infiltrated are enriched and crystallized on the surface of the substrate, and penetrate into the matrix to a certain depth. From the surface to the inside, the concentration of the elements to be infiltrated decreases in a gradient, and its organizational structure also changes in a gradient, forming a layer of infiltration on the outer surface of the substrate. The performance of metal, the core of the base material still maintains the original performance, and the performance of the middle layer gradually exceeds the gradient functional material. The densification of the gradient material with continuously changing components makes the plating material and the matrix firmly bonded. The plating material and the matrix are not easy to fall off during the reaction process of making the battery material, ensuring the consistency of battery cycle performance and life. By adding selected Group II elements , rare earth elements, etc., to prepare doped and infiltrated gradient composite spherical nickel hydroxide to obtain the effect of high-temperature nickel-hydrogen batteries. 4. Conclusion Adding rare earth, rare, alkaline earth elements or oxides to the cathode ingredients of nickel-metal hydride batteries can improve the performance of nickel-metal hydride batteries at high temperatures. The representative elements are: such as Mg, Ca, Sr, Sc, Y, One or more of La, lanthanide elements, Ti, Zr, Cr, Mo, W, Mn, Fe, Co, Cu, Zn, Cd, B, Al, Ga, In, Si, P, As, Sb, Bi oxides and hydroxides. Among them, there are many introductions to the research and application of zirconium in new energy materials [6][7][8]. In addition to zirconium’s practical industrial applications in special applications (nuclear energy, zirconium plates, pipes), other applications in nickel-hydrogen positive and negative electrodes are Materials and lithium battery cathode material additives do not yet have practical industrial applications. Mechanical mixing method has surface mixing problems with uniformity, which affects performance; chemical precipitation doping and coating have certain advantages over mechanical mixing methods, and there are still production process control technologies; doping, infiltration and plating gradient composite spherical nickel hydroxide may be the solution to the above effective method for deficiencies.