New paper published on “Unraveling the Electrochemical Mechanism in Tin Oxide/MXene Nanocomposites as Highly Reversible Negative Electrodes for Lithium-Ion Batteries” in Advanced Materials Interfaces.

As the demand for power and energy storage continues to grow, we researchers are constantly exploring new ways to improve battery performance. One promising approach involves using conversion/alloying materials, such as tin oxide, to design high-performance lithium-ion batteries. While these materials show excellent performance and ease of preparation, they often suffer from mechanical instabilities during cycling that limits their usefulness. This issue can be addressed (and overcome) by combining tin oxide with MXene.

In this study, we prepared a 50/50 (by mass) tin oxide / Ti-MXene (SnO2/Ti3C2Tz) nanocomposite and optimized it as a negative electrode for lithium-ion batteries. The result? A nanocomposite that delivers over 500 mAh/g for 700 cycles at 0.1 A/g and demonstrates excellent rate capability, with 340 mAh/g at 8 A/g.

The success of this nanocomposite lies in the synergistic behavior of its two components, which we confirmed through ex situ chemical, structural, and morphological analyses. Not only does this knowledge allow us to formulate a reaction mechanism with lithium-ions that provides partial reversibility of the conversion reaction, but it also opens up new possibilities for designing high-performance lithium-ion batteries.

Thanks to our great team of collaborators:

Team Ricerca sul Sistema Energetico – RSE SpA & Università degli Studi di Milano-Bicocca:
Antonio Gentile
Chiara Ferrara
Stefano Marchionna
Riccardo Ruffo

Team INM-Leibniz Institute for New Materials:
Stefanie Arnold
Volker Presser

Team Karlsruhe Institute of Technology (KIT)
Yushu Tang
Julia Maibach
Christian Kübel

Our research team has published an article in ChemSusChem on the promising use of stable and efficient SnO₂ electrodes for degrading refractory organic pollutants in wastewater treatment. Our approach involved the preparation of Ti³⁺ self-doped urchin-like rutile TiO₂ nanoclusters (TiO_2-xNCs) on a Ti mesh substrate using hydrothermal and electroreduction methods, which served as an interlayer for the deposition of Sb-SnO₂. Our TiO_2-xNCs/Sb-SnO₂ anode exhibited a high oxygen evolution potential and strong *OH generation ability, resulting in improved degradation performance for rhodamine B, methylene blue, alizarin yellow R, and methyl orange. Our unique rutile interlayer also extended the anode lifetime sixfold due to its good lattice match with SnO₂ and three-dimensional concave-convex structure. Overall, our work highlights the importance of designing interlayer crystal forms and structures for achieving efficient and stable SnO₂ electrodes in addressing dye wastewater problems. This work was done in collaboration with our colleagues from Chongqing University.

New paper published in the Journal of Industrial and Engineering Chemistry. In cooperation with former group member Choonsoo Kim (now at Kongju University, Korea), we have used redox flow desalination for the valorization of tetramethylammonium hydroxide as a value-added organic compounds from wastewater which is widely being used as an etching solvent, photoresist developer, and surfactant
in semiconductor and display industries. By applying a low cell voltage (<1.2 V), a reversible redox
reaction allowed a continuous removal of TMAH from the wastewater stream and a simultaneous recovery for reuse as a form of tetramethylammonium cation. The TMAH removal rate was approximately
4.3 mM/g/h with a 40% recovery ratio.

New perspective paper published in Communications Materials. The high entropy concept is ideally suited for MXenes but also capable to be a unique tool to tailor and improve electrochemical properties in other materials.

Multiple principal element or high-entropy materials have recently been studied in the two-dimensional (2D) materials phase space. These promising classes of materials combine the unique behavior of solid-solution and entropy-stabilized systems with high aspect ratios and atomically thin characteristics of 2D materials. The current experimental space of these materials includes 2D transition metal oxides, carbides/carbonitrides/nitrides (MXenes), dichalcogenides, and hydrotalcites. However, high-entropy 2D materials have the potential to expand into other types, such as 2D metal-organic frameworks, 2D transition metal carbo-chalcogenides, and 2D transition metal borides (MBenes).

So, what is our perspective article about? We discuss the entropy stabilization from bulk to 2D systems, the effects of disordered multi-valent elements on lattice distortion and local electronic structures and elucidate how these local changes influence the catalytic and electrochemical behavior of these 2D high-entropy materials. We also provide a perspective on 2D high-entropy materials research and its challenges and discuss the importance of this emerging field of nanomaterials in designing tunable compositions with unique electronic structures for energy, catalytic, electronic, and structural applications.

This perspective paper has been the result of our collaboration with my dear friend Babak Anasori (with his team: Kartik Nemani and Brian Wyatt) from Purdue University and our team (including Mohammad Torkamanzadeh).

New paper published in ACS Applied Nano Materials. Rolling bearings need lubrication to operate smoothly, but when traditional methods fail, multiwall carbon nanotubes (MWCNT) can come to the rescue. To understand how MWCNTs lubricate highly loaded contacts, we combined experimentation and large-scale molecular dynamics simulations. We applied tribometry to iron plates coated with different types of MWCNTs, discovering that both resulted in a steady-state coefficient of friction of 0.18. Wear tracks and tribolayers revealed a transformation process, resulting in layers of MWCNT fragments, iron oxide, and iron carbide nanoparticles embedded in an amorphous carbon matrix. We also found that MWCNTs slide against the ball interface to provide low carbon transfer to the counter body. Molecular dynamics simulations predicted a low-load regime that keeps MWCNTs intact, and a high-load regime that partially collapses the tube structure, forming a-C regions. We confirmed the results through transmission electron microscopy, and formulated a multistep lubrication mechanism for MWCNT coatings rubbing against alumina on an iron substrate. This work was done in collaboration with the teams of Frank Mücklich and Michael Moseler.

New paper published in the Journal of the American Ceramic Society on the synthesis of new hybrid electrode materials for Li-ion batteries (LIBs). Through controlled oxidation of layered Ti₂SnC, we were able to obtain TiO₂-SnO₂-C/carbide hybrid materials using two different methods: partial oxidation in an open-air furnace (OAF) and rapid thermal annealing (RTA). The resulting carbide phase included both residual Ti₂SnC and TiC as a reaction product. In testing, we found that the sample oxidized in the OAF at 700°C for 1 hour had the highest initial lithiation capacity of 838 mAh/g at 100 mA/g. However, its delithiation capacity decreased to 427 mAh/g over cycling. In contrast, the RTA sample treated at 800°C for 30 seconds demonstrated the most efficient performance, with a reversible capacity of approximately 270 mAh/g after 150 cycles and a specific capacity of about 150 mAh/g under high cycling rate (2000 mA/g). Our findings suggest that this processing method could have wide-ranging applications in energy storage, particularly for other members of the MAX family. This work was the latest product of collaboration with the team of Michael Naguib (Tulane University, USA).