Researchers at The University of Texas at Austin and Stony Brook University have fabricated a thicker electrode for lithium-ion batteries by controlling nanosheet assembly via the combination of an external magnetic field and drying-based densification.

This dense and thick electrode is capable of delivering a high volumetric capacity >1,600 mAh cm⁻³, with an areal capacity up to 32 mAh cm⁻², which is among the best reported in the literature. A paper on the work is published in Proceedings of the National Academy of Sciences (PNAS).

Two-dimensional materials are commonly believed as a promising candidate for high-rate energy storage applications because it only needs to be several nanometers thick for rapid charge transport. However, for thick-electrode-design-based next-generation, high-energy batteries, the restacking of nanosheets as building blocks can cause significant bottlenecks in charge transport, leading to difficulty in achieving both high energy and fast charging.

—Guihua Yu, co-corresponding author

The researchers used two-dimensional materials as the building blocks of the electrode, stacking them to create thickness and then used a magnetic field to manipulate their orientations. The research team used commercially available magnets during the fabrication process to arrange the two-dimensional materials in a vertical alignment, creating a fast lane for ions to travel through the electrode.

Typically, thicker electrodes force the ions to travel longer distances to move through the battery, which leads to slower charging time. The typical horizontal alignment of the layers of material that make up the electrode force the ions to snake back and forth.

Our electrode shows superior electrochemical performance partially due to the high mechanical strength, high electrical conductivity, and facilitated lithium-ion transport thanks to the unique architecture we designed.

—Zhengyu Ju, lead author

In addition to comparing their electrode with a commercial electrode, they also fabricated a horizontally arranged electrode using the same materials for experimental control purposes. They were able to recharge the vertical thick electrode to 50% energy level in 30 minutes, compared with 2 hours and 30 minutes with the horizontal electrode.

The researchers emphasized they are early in their work in this area. They looked at just a single type of battery electrode in this research.

Their goal is to generalize their methodology of vertically organized electrode layers to apply it to different types of electrodes using other materials. This could help the technique become more widely adopted in industry, so it could enable future fast-charging yet high-energy batteries that power electric vehicles.

Here, we develop a method of controlling nanosheet assembly via the combination of an external magnetic field and drying-based densification to prepare high-density, low-tortuosity electrodes. The vertically interconnected nanosheet network provides efficient pathways for mass transport, delivering both high areal and volumetric capacities far beyond those of commercial electrodes. The methodology demonstrated is potentially universal in aligning nanosheets in a vertical and dense manner for advanced battery electrodes.

—Ju et al.

Resources

• Zhengyu Ju et al. (2022) “Vertically assembled nanosheet networks for high-density thick battery electrodes” PNAS doi: 10.1073/pnas.2212777119