The Influence Of Nanometric Additives On The Electrochemical Performance Of Positive Electrode In Mh/Ni Batteries

Nickel/metal hydride (Ni/MH) power batteries is considered one of the most promising devices for electric vehicle (EV) and hybrid electric vehicle (HEV) applications due to both its high rate charge/discharge capability and its high reliability. High power performance is one of the key requirements for a power battery, and is strongly affected by the high charge and discharge rate performance of the active materials. The high rate performance of the active materials is closely associated with the activation behavior of the active materials. Further improvements in the overall performance of the Ni/MH power batteries partially rely on gaining a better understanding of the activation characteristics of nickel hydroxide, which is the active material for the positive electrode of the battery. However, nickel hydroxide is a P-type semiconductor with low conductivity, and therefore we should add some conductive agent or additives into the positive electrode.In the first chapter, the main statement is the working principle of Ni/MH, the development of Ni/MH, and nano materials in the application of Ni/MH. Finally, it is introduced the research background of this subject.In the second chapter, it is showed the main experimental material and instruments, and completely explained the preparation and test methods of nano-ZnO and electrode.In the third chapter, it is argued that the influence of nano-ZnO on the electrochemical performance of MH/Ni batteries. Nano-ZnO was prepared by the method of direnct precipitation, and used as additive to prepare the positive electrode of MH/Ni battery. The influence of electrochemical performance was investigated in the positive electrode with different content of nano-ZnO. The result indicate that the positive electrode with nano-ZnO shows finer electrochemical performance, which not only expresses a higher discharge capacity, a higher、longer、more flat discharge platform, but also increases reversible、conductivity and oxygen evolution potential to some extent. Especially, the discharge capacity of positive electrode with4wt.%of nano-ZnO up to305mAh/g,which also shows the highest、longest、the most flat discharge platform.In the fourth chapter, it is discussed that influence of nano-ZnO and CNTs on the electrochemical performance of MH/Ni batteries. Nano-ZnO was prepared by the method of direct precipitation, and used as additive with CNTs to prepare the positive electrode of MH/Ni battery. The influence of electrochemical performance was investigated in the positive electrode with different content of nano-ZnO and CNTs. The result indicate that all the positive electrodes with mixing additives show greater discharge capacity retention rate and nano-ZnO expresses finer electrochemical performance at the low-rate of0.2C, and the positive electrode with4wt.%nano-ZnO expresses highest discharge capacity, which not only keeps301mAh/g for the highest discharge capacity,but also retains292mAh/g after40cycles. At the high-rate of1C, the discharge capacity of the positive electrodes with mixing additives decrease seriously, but CNTs indicates better performance and the positive electrode with both3wt.%ZnO and1wt.%CNTs expresses greatest discharge capacity, especially, which retain212mAh/g after40cycles.In the fifth chapter, it is argued that the influence of nano-CuO on the electrochemical performance of MH/Ni batteries. Nano-CuO was prepared by the method of solid phase synthesis, and used as additive to prepare the positive electrode of MH/Ni battery. The influence of electrochemical performance was investigated in the positive electrode with different content of nano-CuO. The result indicate that the positive electrode with4wt.%nano-CuO expresses highest discharge capacity in the low rate of0.2C, which not only keeps280mAh/g for the highest discharge capacity,but also retains270mAh/g after40cycles; in the high rate of1C,the positive electrode with4wt.%nano-CuO expresses highest discharge capacity, which not only keeps252mAh/g for the highest discharge capacity,but also retains243mAh/g after40cycles;Thus, through this subject we can know that nano-ZnO and nano-CuO is very useful to improve the activation performance and efficiency of nickel hydroxide, which is the active material for the positive electrode of MH/Ni battery. In the low rate of discharge system, nano-ZnO and nano-CuO can improve the electrochemical performance of MH/Ni batteries; In the high rate of discharge system, CNTs and nano-CuO can improve the high-rate discharge properties of MH/Ni battery.