Redox flow batteries are potentially transformative energy storage technologies that enable increased renewable electricity to be applied to grids and off-grid for local communities. Current widespread adoption is hindered by engineering issues of the large-scale battery stacks and low power densities due to non-optimised electrodes. The role of the electrode in flow batteries is to provide active sites for the redox reactions and facilitate mass transport and charge transfer. Therefore, the performance of the RFB is dependent on the porous microstructure of the electrodes. Commercial electrodes usually consist of fibre carbon mats of varying porous structure. Although their use is widespread, these materials suffer from poor wettability and high pressure drop. This PhD project will explore the use of 3D printing, a processing technique that allows for flexibility and scalability to design and manufacture electrodes with tailored porosity and electrocatalytic activity, combined with in-situ characterisation techniques to establish structure-property relationships, key to produce optimised efficient energy storage systems. The materials produced will also be tested in other battery technologies, including Na-ion batteries.