3D-printed interlocking electrodes demonstrate optimization potential for energy storage

Good electrochemical energy storage (EES) devices such as rechargeable batteries and supercapacitors can store a lot of energy and release it quickly, but these design goals are often at odds with each other. Using design optimization and 3D printing, a team led by engineers and scientists at Lawrence Livermore National Laboratory (LLNL) has overcome this tradeoff and demonstrated a 3D-printed electrode design for EES that maximizes storage capacity under practical conditions.

The 5.8-millimeter, ultra-thick device, made with two interlocking electrodes that maximize active material and facilitate ion and electron transport, outperformed conventional designs and showed the potential of optimization for advancing next-generation energy storage. Their results were published in a recent paper in Materials Horizons.

EES devices store and release energy through electrochemical reactions. Having thick electrodes provides more active material and therefore higher storage capacity, but it also impedes the transport of ions between the anode and cathode, which limits power (e.g., charging speed). The team thought a solution might lie in the structural design of the electrodes.

"In conventional slab-like designs, a lot of the battery material becomes underutilized because ions cannot reach deep regions efficiently, creating dead zones and concentrated resistive losses near interfaces," explained Giovanna Bucci, a co-author and staff researcher in the Computational Engineering Division (CED) at LLNL.

Exploring new design spaces

3D printing unlocks significantly larger design spaces to work with, and computational design optimization allows researchers to explore them efficiently and find non-intuitive design solutions to complex problems. While optimization has been used to design EEC electrodes before, the team was the first to optimize both electrodes simultaneously.

"The computer can produce geometries that are hard to intuit from experience alone, but are directly aligned with the device's limiting physics," said CED researcher Hanyu Li. "It helps us understand why certain geometric features are good, and how different geometries are appropriate for different use cases."

The team built an optimization framework based on experimental data to generate designs, then print them with a unique resin formulation and multi-material microstereolithography (PµSL). The electrodes were printed in two steps: first, a base layer of porous graphene oxide sheets to facilitate ion fusion; then, a layer of gold deposited on the surface to increase electronic conductivity.

The 4-millimeter electrodes are interdigitated, meaning they interlock like fingers of folded hands. This distributes the active material to reduce "dead zones" and increases the surface area to give electrode particles plenty of entry and exit points to facilitate transport.

"This study treats electrode architecture as a performance lever just as important as the material itself," said CED researcher Thomas Roy. "The optimized interpenetrating 3D layouts create many accessible pathways for ions, while the integrated conductive network supports electron transport through the structure."

The optimized electrodes outperformed both conventional 2D designs and other 3D-printed carbon-based supercapacitors, demonstrating better capacitance capabilities, improved charge storage and energy storage performance, and lower resistance. The device also showed impressive stability and reliability over more than 7500 charge/discharge cycles.

"The real breakthrough is not one component in isolation, it is the integration," said Physics and Life Sciences researcher Marcus Worsley. "The interdisciplinary nature of the project demonstrates how our team and LLNL are uniquely positioned to tackle such collaborative projects and complex problems."

The team plans to build on their success by extending the optimization framework for other devices, such as lithium-ion batteries, chemo-mechanical co-design of stretchable batteries, electrochemical flow batteries, and electrochemical mineral separation. They also plan to explore ways to use their technique for large-scale manufacturing to help deliver optimized next-generation EES devices for applications including consumer electronics, electric vehicles, renewable energy sources, and more.

Provided by Lawrence Livermore National Laboratory