Paving the Way for Improved Battery Performance by Controlling Micro-/Macro-Structures

Researchers at Missouri S&T are investigating unique processing methods for manufacturing battery electrodes that could lead to transformational enhancements in battery capacity, energy density, and life cycle.  

Although remarkable advances have been made in lithium ion batteries (LIBs) during the past several decades, higher energy and power densities are still required for portable devices, transportation, and stationary applications. The amount of materials in an electrode determines the energy and power of the LIB and, thus, the requirement for a high tap density is of considerable importance. The conventional strategy towards creating a high tap density is to add more material to achieve a higher packing density. While an increase in the volume fraction of an active material improves the transport of lithium ions and electrons in the solid phase, it impedes the transport of lithium ions in the electrolyte. For this reason, increasing packing density is not always desirable. An alternative strategy is to add more material by increasing the thickness of the electrodes. This approach, however, limits the transport of ions and electrons, resulting in poor power performance and inefficient utilization of materials. 

Dr. Jonghyun Park, assistant professor, and Mr. Jie Li, Ph.D. candidate, of the mechanical and aerospace engineering department at Missouri S&T, whose research focuses on additive manufacturing, advanced batteries, and multiscale/metaphysical modeling of batteries, turned to manufacturing as a means to increase tap density. With colleagues, Dr. Xinhua Liang, associate professor of chemical and biochemical engineering, and Dr. Frank Liou, professor of mechanical engineering, Dr. Park and Mr. Li developed a new manufacturing technique for fabricating battery electrodes that simultaneously controls the patterning of the macro-/micro-structures to increase tap density, helping address current energy storage technology gaps and future energy storage requirements. 

 Modern batteries are fabricated in the form of laminated structures that are composed of randomly mixed constituent materials. This randomness in conventional methods can provide a possibility of developing new breakthrough processing techniques to build well-organized structures that can improve battery performance. 

The proposed processing technique consists of an electric field process that controls the microstructure pattern of manganese-based electrodes, and an additive manufacturing process that controls the macro-3D structures and the integration of both scales. The synergistic control of micro-/macrostructures is a novel concept in energy material processing that has considerable potential for providing unprecedented control of electrode structures, thereby enhancing battery performance. Electrochemical tests have shown that these new electrodes exhibit superior performance in their specific capacity, areal capacity, and cycle life. The final areal capacity increased by over 20% with this technology. Their work was reported in the article “Macro-/Micro-Controlled 3D Lithium-Ion Batteries via Additive Manufacturing and Electric Field Processing,” published in Nature: Scientific Reports (https://www.nature.com/articles/s41598-018-20329-w).

Says Dr. Park, “with this new manufacturing method, 3D well-organized electrode structures which cannot be achieved from conventional fabrication methods are possible, opening the possibility to significantly improve battery performance.”