Parameter evaluation of printed primary Zn/MnO2 batteries with nonwoven and hydrogel separators

Potentially important parameters of printed flexible batteries based on the primary zinc-manganese dioxide (Zn/MnO2) system were investigated using a fractional factorial design of experiments. A novel hydrogel electrolyte made of lactic acid and cornstarch proved the functionality. Using this kind of hydrogel, it was important to prevent unwanted side reactions with the zinc electrode. Accurate control of the electrode mass is absolutely necessary, since the mass of deposited MnO2 and the mass ratio of MnO2:Zn determine the capacity of the cells. With optimised parameter settings the capacity of printed cells was increased to over 100 mAh, which is equivalent to an area-related specific capacity of about 7.3 mAh cm−2. This is within the range of commercially available button cells, which provided between 125-155 mAh under the same discharge conditions. By means of electrochemical impedance spectroscopy, the cells were examined immediately after assembly. Within three hours the cell could be identified as, in principle, working or defective. As such, precious measurement time can be saved by selecting promising cells prior to characterisation.