The overall goal of the project is to make battery electrodes using Additive Manufacturing (AM) methods with nanoparticle sintering aimed at realizing high capacity batteries. The major objectives of the project are: (1) a) to investigate the use of AM technology to manufacture porous battery electrodes. In particular, the project aims to obtain optimal manufacturing process parameters that can control the electrode porosity over multiple length scales; (2) to test the hypothesis that hierarchical porous battery electrodes can lead to electrochemically robust and mechanically strong batteries; and (3) to analyze the performance degradation of porous electrodes during battery operation and solve this problem to overcome electrode capacity reduction. 

The main outcomes of this project are listed as follow: At first, we developed new hybrid 3D structure electrodes with a high aspect ratio are fabricated through extrusion-based additive manufacturing to achieve high mass loading. This new 3D printed battery exhibited both high areal and specific capacity, thus overcoming the trade-off between the two of the conventional laminated batteries. This excellent battery performance was achieved by introducing a hybrid 3D structure that utilizes the benefits of the existing laminated structure and three-dimensional interdigitated structure. This innovative design and fabrication process demonstrated the high areal energy and power density, which is a critical requirement for energy storage systems in transportation and stationary applications.

Next, the extrusion-based method was extended to aerosol-based technology. In this work, we reported a major advance in 3D batteries, where highly complex and controlled 3D electrode architectures with a lattice structure and a hierarchical porosity are realized by 3D printing. Microlattice electrodes with porous solid truss members (Ag) were fabricated by Aerosol Jet 3D printing that leads to an unprecedented improvement in the battery performance such as 400% increase in specific capacity, 100% increase in areal capacity, and a high electrode volume utilization when compared to a thin solid Ag block electrode. Further, the microlattice electrodes retained their morphologies after 40 electrochemical cycles, demonstrating their mechanical robustness. These results indicated that the 3D microlattice structure with a hierarchical porosity enhanced the electrolyte transport through the electrode volume, increased the available surface area for electrochemical reaction, and relieved the intercalation-induced stress; leading to an extremely robust high capacity battery system.

Finally, we have identified the key principles of how our proposed structure improves the battery performance. The diffusion/migration of electrons/ions inside the battery was comprehensively analyzed via a 3D electrochemical model and subsequently validated by experiments on 3D micro-lattice electrodes made by Aerosol Jet printing. Lithium concentration and potential distribution were mapped to correlate battery performance with different shapes, thicknesses, packing density, and porosities. The study revealed that the main factors determining battery performance are ion diffusion in the electrolyte and electron transport in the 3D electrode skeleton. Further, the emergence of a competition between available volume for intercalation and an easier electronic/ionic path was shown, which determined their areal/specific capacities. In order to fully reap the benefits offered by 3D structures for both energy and power performance, the length scale of members forming electrode structures needs to be optimized at a scale of the order of the intercalation diffusion length, which is tens of micrometers. This study revealed highly useful guidelines for optimized 3D electrode designs and the possible manufacturing routes to realize them in order to achieve superior battery performance.

For the education part, total five PhD students and two undergraduate students involved in this project and exposed to the cutting-edge additive manufacturing and electrochemical device technology. Training on additive manufacturing, characterization of microstructures, assembly of lithium ion battery coin cells, battery testing, and modeling well established their skills and critical thinking for their future careers. Three PhD students have graduated; one PhD student is expected to graduate in May 2021; and one PhD student is expected to graduate in May 2022. Four undergraduate students were involved in the project, which helped them understand basic engineering concepts and grasp basic experimental skills.

For the dissemination of research outcomes, five journal papers have been published based on this project, and two manuscripts are in pending. The PIs or their PhD students attended conferences for 13 presentations and 12 invited presentations.

The outcomes of this project are expected to have great scientific as well as technological impact on the development of advanced lithium ion batteries. Understanding the links between the atomic scale, microstructure, macroscopic properties, and failure is one of the fundamental challenges in the mechanics of battery materials. The knowledge and approaches gained from this investigation will be of particular use to the battery community.

Last Modified: 01/02/2021
Modified by: Jonghyun Park