3D Printing of Batteries—Comparison Between Fabrication Processes

The recent development that printing technologies have experienced, combined with the increasing demand for miniaturized wearables and portable electronics, has boosted the interest in compact and high energy density freeform energy storage devices. At the moment, emerging applications and devices such as biomedical sensors or micro-electro-mechanical systems, are limited in shape, size and price by the energy storage devices that power them.<br/>In this regard, printing technologies propose an affordable and adaptable alternative of creating complex architectures that could maximize the energy density of batteries and supercapacitors[1].<br/>Although a substantial effort has been done to push forward the application of printing strategies for energy storage devices, especially by additive manufacturing, this field is still in its infancy and a lot of challenges remain[2].<br/>A recurrent problem in this field is the lack of information on how the microstructure of the composites is affected by the selected fabrication method and how this impact the performance of the final device. This makes it difficult to translate results and isolate problems, as well as optimize designs and composites.<br/>In this work, we present a systematic study of the changes that occur on the electrode materials when we move from traditional techniques to printing based methods. We give special attention to the correlation of the electrochemical performance of the devices with the microstructure shown by the electrodes fabricated by each technique.<br/>The selected techniques encompass traditional battery fabrication methods such as slurry casting and filtration and more advanced ones used in printed devices, including extrusion printing, spray coating and aerosol jet printing. To fairly compare these methods, the same ink formulations were used across all techniques. For each technique, three different percentages of conductive additive were used to assess the behaviour shown by each fabrication method. The main active material used for this work was LTO in combination with CNTs, but to prove that the results can be extrapolated to any materials, silicon was also used to back up the findings.<br/>The methodology used for the electrochemical analysis, was mainly the comparison of their rate performance. The results were fitted to physical models[3] and the differences were correlated to the observations made by morphological and structural based techniques, such as TEM, SEM and BET.<br/>It was found that significant differences in the network arrangement can be induced by the deposition technique, creating segregated[4] or randomly arranged networks depending on the processes involved. It was also found that porosity is another factor that is massively affected by the fabrication technique and its effect on the electrochemical performance is influenced by the network arrangement.<br/>In summary, our work is a systematic and insightful study of how the deposition techniques affect each of the physical parameters of the electrodes and how those interplay with the device performance. Additionally, we highlight the main issues in each technique and ways to mitigate them.<br/>[1] Y. Pang, Y. Cao, Y. Chu, M. Liu, K. Snyder, D. MacKenzie, C. Cao, Additive Manufacturing of Batteries, Adv. Funct. Mater. 30 (2020). doi:10.1002/adfm.201906244.<br/>[2] P. Chang, H. Mei, S. Zhou, K.G. Dassios, L. Cheng, 3D printed electrochemical energy storage devices, J. Mater. Chem. A. 7 (2019). doi:10.1039/c8ta11860d.<br/>[3] R. Tian, S.-H.H. Park, P.J. King, G. Cunningham, J. Coelho, V. Nicolosi, J.N. Coleman, Quantifying the factors limiting rate performance in battery electrodes, Nat. Commun. 10 (2019). doi:10.1038/s41467-019-09792-9.<br/>[4] S.-H.H. Park, P.J. King, R. Tian, C.S. Boland, J. Coelho, C. (John) Zhang, P. McBean, N. McEvoy, M.P. Kremer, D. Daly, J.N. Coleman, V. Nicolosi, High areal capacity battery electrodes enabled by segregated nanotube networks, Nat. Energy. 4 (2019). doi:10.1038/s41560-019-0398-y.