Mechanical polishing as an improved surface treatment for platinum screen-printed electrodes

The viability of mechanical polishing as a surface pre-treatment method for commercially available platinum screen-printed electrodes (SPEs) was investigated and compared to a range of other pre-treatment methods (UV-Ozone treatment, soaking in N,N-dimethylformamide, soaking and anodizing in aqueous NaOH solution, and ultrasonication in tetrahydrofuran). Conventional electrochemical activation of platinum SPEs in 0.5 M H2SO4 solution was ineffective for the removal of contaminants found to be passivating the screen-printed surfaces. However, mechanical polishing showed a significant improvement in hydrogen adsorption and in electrochemically active surface areas (probed by two different redox couples) due to the effective removal of surface contaminants. Results are also presented that suggest that SPEs are highly susceptible to degradation by strong acidic or caustic solutions, and could potentially lead to instability in long-term applications due to continual etching of the binding materials. The ability of SPEs to be polished effectively extends the reusability of these traditionally "single-use" devices

Gap width modification on fully screen-printed coplanar Zn|MnO2 batteries

Fully printed primary zinc-manganese dioxide (Zn|MnO2) batteries in coplanar configuration were fabricated by sequential screen printing. While electrode dimensions and transferred active masses were kept at constant levels, electrode separating gaps were incrementally enlarged from 1 mm to 5 mm. Calendering of solely zinc anodes increased interparticle contact of active material within the electrodes while the porosity of manganese dioxide based electrodes was maintained by non-calendering. Chronopotentiometry revealed areal capacities for coplanar batteries up to 2.8 mAh cm−2. Galvanostatic electrochemical impedance spectroscopy measurements and short circuit measurements were used to comprehensively characterise the effect of gap width extension on bulk electrolyte resistance and charge transfer resistance values. Linear relationships between nominal gap widths, short circuit currents and internal resistances were evidenced, but showed only minor impact on actual discharge capacities. The findings contradict previous assumptions to minimise gap widths of printed coplanar batteries to a sub-millimetre range in order to retain useful discharge capacities. The results presented in this study may facilitate process transfer of printed batteries to an industrial environment

The effect of electrode calendering on the performance of fully printed Zn∣MnO2 batteries

Primary zinc–carbon batteries with a coplanar battery architecture were prepared by screen printing. Prior to battery activation by printing of an acidic zinc chloride electrolyte, printed zinc and manganese dioxide electrodes were compacted by calendering. Material densification of the electodes resulted in electrode layer thickness reduction on both sides, modified micropore surface area and volume on the cathode side. Galvanostatic impedance measurements and chronopotentiometry were used to characterise fabricated batteries with the individually prepared electrode configurations. While calendering of both electrodes of the batteries showed adverse effects by an increase of internal resistances and a reduction of discharge capacities, exclusive calendering of the zinc anode increased the active material utilisation by electrochemical cell reaction and thus the discharge efficiency of the battery