Instead of disposing of batteries after two or three years, we could have recyclable batteries that last for up to nine years, by using high-frequency sound waves to remove rust that inhibits battery performance. The research, published in Nature Communications, was led by engineers at RMIT University.
“In this work, we show that exposing an oxidized MXene film to high-frequency vibrations for just a minute removes the rust on the film,” said co-lead author Hossein Alijani, PhD candidate. “This simple procedure allows its electrical and electrochemical performance to be recovered.”
The team worked with nanomaterial MXene, a class of materials that they say promises to be an exciting alternative to lithium for batteries in the future. In addition, it’s similar to graphene with its high electrical conductivity.
“Unlike graphene, MXenes are highly tailorable and open up a whole range of possible technological applications in the future,” said Leslie Yeo, co-lead senior researcher, professor, RMIT.
The big challenge with MXene is that it rusts easily — inhibiting electrical conductivity and rendering it unusable.
“To overcome this challenge, we discovered that sound waves at a certain frequency remove rust from MXene, restoring it to close to its original state,” Yeo said. “The ability to prolong the shelf life of MXene is critical to ensuring its potential to be used for commercially viable electronic parts.”
The team says its rust-removing work opens the door for the nanomaterial to be used in a wide range of applications in energy storage, sensors, wireless transmission, and environmental remediation.
Here is a Tech Briefs interview — edited for clarity and length — with Associate Professor Amgad Rezk, co-lead senior researcher, and Alijani, who assisted with the interview.
Tech Briefs: What inspired the research?
Rezk & Alijani: The broader context is the limitations with the available energy-storage materials, mostly Li-ion-based batteries. For example, lithium mining has environmental concerns, and Li-ion batteries have known safety hazards. MXene is a non-hazardous young material (only discovered in 2011) with promising energy-storage properties that could contribute to our energy demand in the near future, but it is not stable enough because it oxidizes and degrades (as do Li-batteries) very quickly in ambient operating conditions.
In our research group, we modulate the physical and chemical properties of nanomaterials (atomically thin layers) with high-frequency vibrations. The high-frequency vibrations we use are surface acoustic waves — nanometer amplitude earthquake-like vibrations generated on a chip-size piezoelectric material. We have used this technology to make nanocrystals, break nanosheets, synthesize nanoparticles, etc.
Interestingly, in our previous projects, we had seen that our acoustic waves do not oxidize nanomaterials while processing them, unlike other common harsh chemical and heat treatments. Therefore, we were inspired to test the use of our high-frequency vibrations (our main expertise) to address the challenge of nanoscale-rusting of electronic materials.
Tech Briefs: How did you arrive at the conclusion that exposing an oxidized MXene film to high-frequency vibrations for just a minute removes the rust on the film?
Rezk & Alijani: We have multiple characterization techniques in our arsenal. Initially, we took some pristine MXene materials and intentionally let them oxidize. Then, we carefully characterized them with different techniques, including X-ray diffraction and direct imaging under sophisticated high-magnification (500,000 X!) scanning and transmission electron microscopy, where we directly observed the grain-like oxidation nanoparticles. Then we exposed the samples to our high-frequency acoustics, and re-imaged them to observe the removal of the oxide/rust layer, and the film layer appeared similar to the pristine film. We have also characterized the electrical storage (capacitance) before and after the acoustic treatment, to confirm the reversal in storage capacity, which is related to battery devices able to hold charges after degradation due to the internal oxidation.
Tech Briefs: Can you explain in simple terms how the technology works?
Rezk & Alijani: On a large “macroscale,” we use, for example, sandpapers or rough brushes to remove rust from a metallic surface. On a small “nanoscale,” this is not possible, so we need different innovative approaches. These tiny vibrations, from our high-frequency acoustic chip, can “shake” the rust off the MXene film surface without damaging the entire film. Because these vibrations only affect the surface of the material, the rust is knocked off the surface, while keeping the core intact. Importantly, this technology could increase the lifetime of the material by a factor of three. Moreover, we learned that this technology is agnostic to the material, — it works for other materials too. Therefore, we think that we can implement it with the other materials.
Tech Briefs: What’s the next step with regards to your research/testing?
Rezk & Alijani: At the same time that we’d like to study this idea in further detail, we want to find collaborators from industry to upscale our technology. Our technology can possibly be integrated into electronic devices, such as the batteries in electric cars or mobile phones, and we would like to test it in commercialized electronic devices.
Tech Briefs: How long before recyclable batteries are ubiquitous?
Rezk & Alijani: That’s the billion-dollar question, as there are many factors involved, including government policies, ups and downs in the tech market, and consumers, to name a few. But one thing is certain: our need to move faster toward more sustainable resources, one of which being recyclable and/or sustainable batteries. The world is moving quickly to address this, and we can just hope this is achieved in the “near” future. Our technology is unique, relatively cheap, and potentially easily integrated with a variety of materials and processing techniques to contribute to overcoming their energy storage and longevity challenges. That’s why we want to study it more and find some industry partners to take it to the next step: upscaling and commercialization.
Tech Briefs: Do you have any advice for engineers aiming to bring their ideas to fruition/market?
Rezk & Alijani: They should pay attention to the grand problems, gaps, and needs in their fields. This can help them in shaping their ideas as they progress. They shouldn’t underestimate the role of imagination and intuition, which are usually neglected in today’s world, even in the research environment. There are no stupid ideas; actually, the crazier, the better.
Engineers shouldn’t be afraid of the things they don’t know; rather, they should embrace them. Academia is a very good place to start because we have a good degree of freedom to work on different ideas and study things in specific detail. But having ideas that work might not be enough; excellent communication skills are necessary to pitch the ideas to the consumers in the market.
Tech Briefs: Anything else you’d like to add?
Rezk & Alijani: In our research group, we trust our hunches when it comes to science, and we dare to try lots of ideas that often fail, but overall, it has paid us back very well, such as this project. As much as we need more PhD students to bring their ideas to us, we welcome industry partners to develop our ideas because our vision goes beyond academia. We want to change things for better, with our high-frequency vibrations technology.