The architectural design of electrodes offers new opportunities for next-generation electrochemical energy storage devices (EESDs) by increasing surface area, thickness and storage capacity.
But conventional thick electrodes increase ion diffusion length and cause larger ion-concentration gradients, limiting reaction kinetics, including storage capacity.
To overcome these challenges, Lawrence Livermore National Laboratory (LLNL) scientists and collaborators at the University of California, Santa Cruz 3D-printed a new and compact device configuration with two interpenetrated, individually addressable electrodes, allowing precise control over the geometric features and interactions between the electrodes.
Using powerful high-performance computing facilities at LLNL, the team demonstrated through computational simulation that the interpenetrated electrode design improves ion-diffusion kinetics in EESDs by shortening the ion-diffusion length and reducing ion-concentration inhomogeneity.
"The device with interpenetrated electrodes outperformed the traditional separate electrode configuration, enhancing both volumetric energy density and capacity retention rate," said LLNL postdoc Longsheng Feng, co-author of a paper appearing in Nano-Micro Letters.
This free-standing device structure also avoids short-circuiting without needing a separator. The feature size and number of interpenetrated units can be adjusted during printing to balance surface area and ion diffusion.
The team used a zinc manganese dioxide battery as a model system and found that the device outperforms conventional separate electrode configurations, improving volumetric energy density by 221% and exhibiting a higher capacity retention rate of 49% compared to 35% at temperatures from 20 to 0 °C.
"Our study introduces a new EESD architecture applicable to lithium-ion, sodium-ion batteries, supercapacitors and other storage systems," Feng said. "To our knowledge, this is the first time that interpenetrated lattices have been used for architectural EESDs."
Significantly ordered, periodically entangled two electrodes occupying the same free volume are close to each other throughout the whole structure regardless of its thickness. This structural characteristic is anticipated to enhance the ion diffusion kinetics during the charging and discharging processes.
"This new tool kit of materials and designs will enable high-performance energy storage in conditions relevant to national security missions and the broader energy storage community," said LLNL scientist Marcus Worsley, a co-lead author.
Other LLNL authors include Tae Wook Hoo and Cheng Zhu. The work is funded by the LLNL Laboratory Directed Research and Development Program.
