| The emphasis of this dissertation was focused on the research of high performance Ni-MH battery and its new positive materials.For the research of high performance Ni-MH battery, one of the findings was that AA2300mAh high capacity Ni-MH battery was successfully manufactured with sphericalβ-Ni(OH)2 and AB5 hydrogen storage alloy serving as positive and negative materials respectively. The experimental Ni-MH battery could provide a capacity of 2330mAh and preferable cyclic performance. The physical characters of 6 kinds of separators were compared with each other as well as their influence on the electrochemical performance of dynamical Ni-MH batteries. The evaluating methods of Ni-MH separators were also summarized. The effects of electrolyte additives, such as LiOH, NaOH and Na2WO4, on the electrochemical performance of Ni-MH batteries were investigated and it was concluded that 5wt%Na2WO4 was more effective for improving short-dated electrochemical properties of Ni-MH batteries at 70℃. Based on the surface morphologies and fractographies of exploded steel shell, the explosion problem of high capacity Ni-MH batteries was primarily discussed. It could be generalized that the occurrence of battery explosion could be ascribed to the combined actions of micro-fissures of nickel coating, hydrogen embrittlement, H+ transportation and internal pressure p in the charging process.For the study of new positive materials, smaller size spherical Ni(OH)2 particles, prepared by precipitation conversion, could reduce the charging potential of nickel electrode and release a capacity of 20mAh/g more than nominal value, when it was mechanically mixed with common spherical Ni(OH)2 powders at a 3wt% weight ratio. Non-doped and Al3+, Zn2+, Mn2+, Fe3+, Co2+, Mg2+, Cr3+ doped Ni(OH)2 powders were synthesized individually by homogeneous precipitation with a higher heating temperature and NH3·H2O, generated from the thermal decomposition of urea, as precipitant. All the prepared Ni(OH)2, which had smaller grain sizes and more lattice defects, belong to turbostraticα-Ni(OH)2 structure and displayed high electrochemical cyclic stability. Compared with each other, Al3+ dopedα-Ni(OH)2, with a chemical formula of Ni0.70Al0.18(OH)1.6(CO3)0.1(SO4)0.07·(H2O)0.6, showed higher discharging plateau and more stable cyclic performance. It had the highest special capacity and charging-discharging efficiency. Its microstructure was composed of agglomerated nanocrystal fibrous bundles. Furthermore, Al3+ dopedα-Ni(OH)2 represented an excellent electrochemical stability, high rate discharging ability at 60℃and a capacity of 10mAh/g lower than that at 25℃. After charged and discharged for 95 cycles, the experimental electrode materials remainedαphase.In this paper, the preparation of Ni(OH)2 active materials by solid state ball milling method was firstly synthetically studied. The phase structure and electrochemical performance of non-doped and Al3+, Zn2+, Mn2+, Fe3+, Co2+, Mg2+, Cr3+ doped Ni(OH)2 powders were investigated individually. The contributions of Ni:Al ration in the reaction reagents, rotating speed, ball milling periods and ball-mass ratio to the structure and electrochemical properties of Al3+ doped Ni(OH)2 were also researched. Moreover, the phase structure, thermal stability, and electrochemical properties of Al3+Zn2+, Al3+Zn2+Co2+ multiple doped Ni(OH)2 synthesized by optimum technique was explored too. The results showed that stable Ni(OH)2 powders could be made in the following process: directly ball milling the mixture of caustic alkali, nickel salt, metallic ion additive and anion stabilizing agent, and then cleaning, centrifugalizing and vacuum drying the milling products. Non-doped, Zn2+, Mn2+, Co2+, Mg2+, Cr3+ doped milling products wereβ-Ni(OH)2 or mainlyβ-Ni(OH)2, while Fe3+, Al3+ doped outgrowth belong toα-Ni(OH)2. Solid state ball milling Ni(OH)2 had smaller grain sizes, lower crystallinity and more lattice defects. However, they all exhibited high electrochemical cyclic performance and structural stability. The microstructure of Al3+ dopedα-Ni(OH)2 was made up of nanocrystal fibrous bundles with a high agglomerated appearance. It showed a high ambient electrochemical properties and discharging cyclic stability at 60℃. Compared with Y2O3, Na2WO4 greatly improve 60℃discharge ability of Al3+ dopedα-Ni(OH)2. With the reduction of Al3+ content in the starting reagents, the phase structure of Al3+ dopedα-Ni(OH)2 transformed fromα-Ni(OH)2 toα/β-Ni(OH)2 and then toβ-Ni(OH)2. However, rotating speed, ball milling periods and ball-mass ratio would never change the crystal structure of Al3+ dopedα-Ni(OH)2. In the ranges of experimental conditions, the best ball milling technology for Al3+ doped Ni(OH)2 was that a 5:1 ratio of nickel to aluminum in the reactive agents combined with a 200r/min rotating speed, a 90min milling period and 30:1 ball-mass ratio. The Al3+Zn2+, Al3+Zn2+Co2+ multiple doped outputs were bothα-Ni(OH)2 structure with a lower capacity, higher cyclic stability, and enhanced activity.
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