.ni / Mh Battery Of High Capacity Cathode Material-ni (oh) <sub> 2 </ Sub> Preparation And Electrochemical Performance

In order to improve the performance of high-capacity Ni/MH batteries, the chemical co-precipitation has been applied to synthesize the stabilized element doped α-Ni(OH)₂ for Ni/MH battery. The electrochemical properties of stabilized Al-Mn multi-element doped α-Ni(OH)₂ and biphase electrode materials with nanosized α-Ni(OH)₂ were investigated. The optimal ratio of nanosized α-Ni(OH)₂ for biphase electrode was also obtained.A certain stoichiometric ratio of Al and Mn was applied to synthesize the stabilized α-Ni(OH)₂ through chemical co-precipitation and the synthesis condition was optimized. The structure and morphology of as-prepared α-Ni(OH)₂ powders were characterized by X-Ray diffraction (XRD) and scanning electron microscopy (SEM). The tap density of powder was also tested. The gavalastatic performance of Al-Mn multi-element doped α-Ni(OH)₂ was performed on a DC-5 battery testing instrument. The Al-Mn multi-element doped α-Ni(OH)₂ is well crystallized α-phase. The tap density of the powder is 1.7g/cm³. The gavalastatic results show that the as-prepared α-Ni(OH)₂ is easily to be activated in charge-discharge process with the highest capacity of 410 mAh/g. The gavalastatic properties keep relatively stable in strong alkaline ambient and retain a capacity of 300 mAh/g after 50 charge-discharge cycles. The discharge potential plateau is high and stable and the charge potential plateau is low.Nanosized Al-doped α-Ni(OH)₂ was synthesized through co-precipitation in alcohol-water system. The powder was characterized by XRD and SEM. The results show that the as-prepared Ni(OH)₂ is cc-phase, spherical morphology with particle sizes of 20-30 nm. The particles are well dispersed. The dispersed nanosized α-Ni(OH)₂ particles were added into microsized spherical β-Ni(OH)₂ powder to form the biphase electrode material. The morphology of the biphase electrode material showed that the nanosized α-Ni(OH)₂ particles were effectively filled into the inter-space of microsized β-Ni(OH)₂ particles. The tap density of biphase electrode with 10 wt.% nanosized α-Ni(OH)₂ could get to 2.30 g/cm3. Cyclic voltammetry properties of biphase electrode material were investigated on a CHI-600 workstation. The activity of nanosized α-Ni(OH)₂ is supper to that of the β-Ni(OH)₂ electrode. The oxidation potential and reduction potential of nanosized α-Ni(OH)₂ are more positive than those of β-Ni(OH)₂ electrode. There are two redox processes of biphase electrode,respectively corresponding to those of 0- and nanosized oc-Ni(OH)2. By suitable amount of nanosized a-Ni(0H)2 addition, the charge-discharge investigation of the biphase electrode materials show that the discharge capacity increases and the cyclic stability enhances under overcharged condition, the discharge potential plateau increases and the charge potential plateau decreases. The biphase electrode with 10 wt.% naoosized cc-Ni(OH)2 has a best overall electrochemical performances. Excessive addition of nanosized cc-Ni(OH)2 has done no good to improve the performances of biphase electrode material.