An Investigation of the Discharge Rate Capabilities of Electrodes for Printed Nickel Based Batteries

Printed micro-batteries could be used in a variety of small electric circuits such as RFID and sensors. Printing techniques can facilitate high volume manufacture in economical processes that have much to offer in energy storage applications. Utility scale electrochemical energy storage will also become an important topic as countries across the globe set targets for highly distributed electricity generation from renewable sources. Time shifting via appropriate energy storage installations as well as peak shaving to stabilise national grids will become an important part of future electricity infrastructures where electrification of transport and heating become commonplace. To meet the demands of such a market stationary, utility scale energy storage technologies must be safe, offer long lifetimes and have inherently low cost. This can be achieved by the use of earth abundant materials and by employing rapid, roll-to-roll, solution coating or printing processes.

Micro-batteries and utility scale energy storage solutions all have different demands in terms of capacity and rate capabilities. Design of electrodes to optimise energy storage can hinder the ability to deliver power and achieve high current densities.

This study describes how print parameters and sinter conditions can be varied to find compromises between kWh capacity stored and kW power that can be delivered on demand. Typical strategies to reduce activation polarisation and increase conductivity of electrode pastes usually result in less available active material to support charge transfer, thus lowering the useful capacity of the cell. This work describes how optimising printing processes to deliver a balance of active material availability and high rate capability can produce versatile electrodes. Sinter conditions are also investigated to strike a balance between the adhesion of the sintered electrode material to the substrate and controlled highly porous sintered structures required to promote adequate mass transport through the porous network of the electrode.

Physical characteristics of the printed electrodes are confirmed by SEM micrographs, profilometery and BET surface area and porosity measurements with the rate capabilities and capacities assessed galvanostatically. EIS and novel scanning electrochemical techniques shed further light on the impact of print and sinter parameters in electrochemical performance.