Alkaline Zn/MnO2 batteries are inexpensive, non-toxic and are readily available for use. They would be ideal for grid scale application if it lasts long and has sufficient capacity left. MnO2 is the cathode which often produces irreversible Mn3+ due to the increase of MnO. Therefore, it is of great importance we prevent the unstable Mn3+ being dissolved by limiting the DOD to allow stabilization to the electrochemical cycles of these cathodes by increasing the life span, reducing the capacity and expenses. Although, this does not prevent the failure and fade of the battery capacity which is due to the formation of Mn3O4 and ZnMn2O4. (The compounds were formed from MnO2 being reduced to MnOOH which is reduced further to Mn(OH)2 after 2e- discharge it becomes susceptible to Zn poisoning and produces Mn3O4 and ZnMn2O4.) With regards to the anode, the Zn can discharge and produce zincate, which either deposits on the cathode or reacts with Zn to form a haeterolite. Due to heaterolite increasing per cycle, it prevents Mn from precipitating and lowers the cell potential by increasing the resistance.
When the concentration of zincate is greater than 0.1M, it becomes detrimental. Therefore, decreasing the concentration of zinc on the cathode lowers the probability of the Zn/MnO2 battery to fail. Other published methods on reducing zincate crossover does not remove Zn transport or cathode failure, but only delays the effect of Zn crossover.
NaSICON (sodium super ion conducting ceramic) separator are conductors for cations and thus prevents Zn from travelling through the separator. NaSICON have recently been investigated as a ceramic separator in liquid electrolyte battery cells. Therefore, presenting a commercial separator in liquid electrolyte battery cells examined under limited DOD for cathode limited Zn/MnO2 cells.
The chemical reagents, resources and materials required are MnO2 powder, graphite powder, KOH, Zn powder, PTFE, expanded coper and nickel mesh, Zn foil, Cellophane 350P00 separator, celgard 3501, cellulose fibre tissue and NaSICON discs.
The experimental procedure consists of 1. Prepare a MnO2 electrode by combining EMD powder, graphite powder, PTEE dispersion, isopropyl alcohol to produce a malleable putty which is baked and wrapped in 4 layers of cellulose fibre tissue.
2. prepare the Zn electrode by combining Zn powder, ZnO, SOBS, PTFE then compressed it onto a copper current collector, which is then wrapped into 4 layers of cellulose fibre tissue. Wrapping in cellulose fibre tissue to aid electrode welting.
3. An electrolyte must be prepared with 30% sodium hydroxide and deionised water. 4. Perform EI spectroscopy and polarization curve testing. This was achieved by using 3D printed H-cell. The chambers were separated by either no separator, 0.5mm NaSICON or 1mm thick NaSICON separators.
5. evolves assembling the electrodes in a polypropylene case. The 3 different separators such as 0.5mm NaSICON membrane, a Celgard with a cellophane layered membrane or 3 layers Cellophane 350P00 were placed between the electrodes. This concept is to observe limited zincate transport and its effect on the batteries life span.
6. lastly we will measure the diffusion of zinc through a custom 3D propylene H-cell. This concludes the brief outline of the experimental procedure.