The advent of printed large area electronics has started delivering exciting innovations over the last few years. A key enabler for fully thin devices are printed energy storage devices. Over the last few years, Zinergy has embarked on a mission to develop simple, low cost, printed energy storage devices which are compatible with other printed electronic devices. 

Printing is a very versatile technique for batteries. It allows to control not only size and shape of devices, but also via thickness control and ink formulations there is a toolkit to adapt the battery´s energy and power requirements to a large set of applications, optimising for energy, power or mechanical properties. Printing batteries allows a degree of freedom in design generally not possible with more traditional production methods. 

In this paper we discuss the use of a printed co-planar battery electrode layout, constructed in a polymer casing which allows the in-situ observation of electrode/electrolyte dynamics. The effects during discharge at various current rates was done by visual time lapsed observation of the formation of compound residues which crystallise and re-dissolve during the discharge process. An aqueous, acidic Zinc/MnO₂ system is used and the spatial observation of reactants allows also the visualisation of electrolyte/ion movement. In addition, it is noted that the presence of the separator plays a critical role in providing nucleation sites for crystallisation. Electrical discharge curves and optical measurements are complemented with in-situ X-ray synchrotron data, allowing the observation of the components formed and as a result provide a better understanding of the discharge process, leading to and overall improved battery design. 

This paper provides an overview of the learnings from in situ measurements of co-planar aqueous zinc batteries, and it is hoped that this system may be more generally applied to observe reaction dynamics in different battery systems, contributing to the electrochemical energy storage field in general.