Studies On Cathode And Technology Of High Power Alkaline Zn/MnO₂ Battery

The mercury-free, alkaline Zn/MnO₂ battery, because of excellent integration performance .environmental compatibility and low cost materials, has been the uppermost product in primary cells. However, the portable digital electronic products which can only be driven by large current are appearing. The commercial alkaline Zn/MnO₂ battery couldn't meet this requirement. Therefore, improving high-rate discharge performance of the Zn/MnO₂ battery has been a market competitive hotspot.The main problems affecting high-rate discharge are ohm resistance and polarization caused during discharge. In order to increase ability of electron conduct and ion diffusion, we adjusted the positive formula and processing technology . The paper adopts a new polymer separator which is suitable to in-situ casting so as to adapt to transformed positive electrode. The main results and findings are summarized as follows:1. To decrease the resistance of cathode ring and serious polarization during large current discharge, we confirmed positive components and the optimum positive formula by orthonormal method, meanwhile adopted mixing method of ball-milling. The SEM indicates surface of EMD is coated graphite of high conductibility, so the conductivity of cathode is promoted. Resistance test demonstrates that the cathode ring axial resistance rate is decreased 30% in comparison with that of the commercial battery. The result of powder microelectrode shows that positive powder has higher react activity and less polarization. The capacities (1188.0mAh) of prepared AA size alkaline Zn/MnO₂ battery is increased 77% compared to that (672.0mAh) of commercial battery, moreover capacities of middle-high voltage region was also promoted obviously, the utilization (25.0%) of active material (EMD) was risen about 15.0% and reached 39.5%.2. We adopted transformed positive electrode (high specific surface area) for replacement of cylindrical electrode to decrease the apparent current density, weakenelectrochemical and concentration polarization. However conventional separator couldn't adapt to the transformed electrode, the two types of PVA separator (more porosity and alkaline separator) which can be cast in-situ were prepared by cross-linking and modified method. Because of fewer thickness of the separator compared to the conventional separator, packing amounts of negative materials will be added about 8%. The performance of high power will be effectively promoted. SEM morphology analysis indicates that the appearance of the separator is uniform. CV test proves that the separator exhibit good chemical and electrochemical Stability, stable potential window is according with working voltage range of alkaline Zn/MnO2 battery. EIS demonstrated the separator has high conductivity. High-power discharge performance of AA size alkaline Zn/MnQj cell manufactured using transformed cathode electrode was improved obviously.