Modeling Mesoporous 3D-Printed Lattice Electrodes for Energy Storage

Abstract

3D printing could offer the versatility to design and manufacture energy storage devices on demand. The precision and material flexibility of 3D printing is ideal for integrating porous electrodes that can enhance electrochemical performance [1] . This work analyzes the electrical conductivity of 3D-printed mesoscale strut lattices at the 100 μm – 1 mm scale with 40 – 90 % volumetric porosity to develop optimal electrodes for energy storage devices. We use a graph-theory-based model [2] to compute the conductivity of multiple 3D lattice types with either solid conducting struts or struts coated with conductive material. These structures show 3 – 5X higher conductivity than random conductive foams that lack an internal periodic mesostructure [3] . Using microstereolithography, we 3D print samples with high-resolution struts (< 70 µm) that maintain their shape and achieve high conductivity after carbonization at 700 ˚C. By tuning the lattice architecture, we manipulate the tradeoff between conductivity, weight, and porosity, validating our simulations with experimental measurements. These results demonstrate that that body-centered cubic (BCC) strut lattices have optimal conductivity per weight compared with other lattice types. Implementing these 3D-printed conductive lattices as supercapacitor electrodes, we see that the lattice architecture impacts the gravimetric capacitance of the devices as well as the mechanical strength, with octet structures outperforming both cubic and BCC lattices. Electrochemical impedance spectroscopy (EIS) shows that 3D-printed electrodes with higher porosity exhibit higher gravimetric double layer capacitance and lower charge transfer resistance, making them ideal candidates for use in supercapacitor electrodes as free-standing 3D hosts for active materials. CV characterization of the electrodes also illustrates how our graph theory-based model for 3D lattices can predict the optimal structure for energy storage. This model can also serve to predict electrode performance and tailor design for integration of higher surface area nanoporous materials on these conductive 3D printed scaffolds. This allows us to guide the design of 3D printed electrodes to minimize charge transfer resistance and achieve an optimal balance between gravimetric and volumetric energy density for device applications. [1] J. Zhao, Y. Zhang, X. Zhao, R. Wang, J. Xie, C. Yang, J. Wang, Q. Zhang, L. Li, C. Lu, Y. Yao, Advanced Functional Materials 2019 , 29 , 1900809. [2] J. E. Huddy, M. S. Rahman, A. B. Hamlin, Y. Ye, W. J. Scheideler, Cell Reports Physical Science 2022 , 3 , 100786. [3] F. G. Cuevas, J. M. Montes, J. Cintas, P. Urban, J Porous Mater 2008 , 16 , 675. Figure showing (a) designed octet (blue), cubic (orange), and BCC (red) lattice types as well as (b) SEM images of their experimental 3D-printed counterparts and (c) measured electrical resistance. Figure 1