| This thesis generalize the development of Zn-Ni cell,analysis the problems and solvements of shape change, dentrites formation, corrosion and passivation of rechargeable zinc negative electrode.It systematically studies the preparing and performance of zinc electrode material.The main synthesized methods for preparing calcium zincate as zinc electrode material are chemical synthesis method,ball-milling method and chemical coprecipitation method.Through the three methods,we synthesized calcium zincate of different shape and construction,and analyse their physicochemical properties by XRD,CV,TG,DSC,micropolariscope,making experiment cell to test their charge and discharge nature.The main conclusions are as follows:1. Calcium zincate of good crystalline form were made in neutral solution and 1M NaOH solution by chemical synthesis method.In neural solution,their shape change as regular tetragonal→tetragonal and hexagonal mixture→regular hexagonal→tetragonal and hexagonal mixture→regular tetragonal,and the uniform tetragonal and hexagonal calcium zincate were made at room temperature and 40℃seperatelly.In 1M NaOH solution,the shape of calcium zincate didn't change regularly as the temperature changed.2. XRD of tetragonal and hexagonal calcium zincate indicate that they all belong to monoclinic system,and their structural formula are all Ca[Zn(OH)3]2·2H2O.We don't know their atom distribution because we hadn't gained their crystal big enough.3. Hexagonal calcium zincate has lower solubility than tetragonal calcium zincate in various KOH solution at room temperature and 40℃,and each sample has higher solubility at 40℃than that at room temperature.4. Hexagonal calcium zincate has better recycle capacity than tetragonal calcium zincate though their CV showd imperfect reversibility.5. The electrochemical testing of the two samples indicated that the hexagonal calcium zincate had 8%～12% higher discharge capacity than the tetragonal calcium zinca-te,showed better application prospect.6. Calcium zincate samples can be got in 10% NaOH by ball milling for 10h.Within 30h,the samples' structural formula was Ca[Zn(OH)3]2·2H2O,and with time extention,when ball milling time were 40～60h,we got a mixture of Ca[Zn(OH)3]2·2H2O and CaZn2(OH)6·2H2O.7. As the concentration of NaOH mediator changed,calcium zincate still can be synthesized when it got 40%,and each sample was Ca[Zn(OH)3]2·2H2O in different NaOH density,their cell parameters decreased with NaOH concentration increased.8. The calcium zincate made in 20% NaOH solution had the best discharge capacity, and the secondary was the sample made in 25% NaOH solution,samples made in 35% and 40% NaOH solution had lower discharge capacity.9. For chemical coprecipitation, the best ratio of Zn/Ca was 2:1.
|
PDF Full Text Request