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).
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 Journal of Energy Storage on MXene battery electrode recycling.
Even the most wonderful electrode material, some sooner than later, will degrade. Even the most wonderful battery, regardless of the used chemistry, will see the end of its life. Battery recycling, using hydrometallurgical or pyrometallurgical pathways, is very energy consuming. So are there alternative recycling concepts? Of course there are! But many of them remain poorly explored.
New materials may not just allow better performance but also novel recycling and second-life applications. The diverse 2D material MXene, for example, can be processed into battery electrodes without binder and without conductive additive. It does not need them 😉 With 100% active mass, and associated with a 2D material, MXene is an ultimate case for an assembly-disassembly-reassembly material. Our work shows the benefits (and limitations) to this circularity of MXene batteries for lithium-ion and sodium-ion batteries.
But sometimes, even with the most heartfelt effort, recycling has its limits. No worries, though, MXenes can also have a second-life! If you oxidize materials, such as titanium based MXene, you end up with metal oxide & carbon (carbide) hybrids that show promising applications for electrocatalysis (or other energy applications).
More MXene and more recycling works upcoming! Stay tuned and I hope more people start not just exploring fancy battery materials but also what to do with spent electrodes. Only time will tell which approach will master upscaling and economic challenges but we, as scientists, must explore all possible pathways.
Big shoutout to my former Ph.D. student Yunjie Li (now in Ulm with Dominic Bresser), our Ph.D. student Stefanie Arnold, and our former Postdoc Dr. Samantha Husmann (now in industry).
New paper published in ChemSusChem in collaboration with the Kickelbick-Group at Saarland University. We have developed an exciting new class of inorganic-organic hybrid materials with redox-active components that have great potential for use in lithium-ion batteries (LIBs). The materials were prepared using an aqueous precipitation reaction of ammonium heptamolybdate (AHM) with para-phenylenediamine (PPD), and a low-energy continuous wet chemical synthesis process known as the microjet process. By varying the ratio of molybdate to organic ligand and pH, we were able to produce two different crystalline hybrid products with large surface areas in the submicrometer range and high purity and reproducibility on a large scale. The first product, [C6H10N2]2[Mo8O26] ⋅ 6 H2O, was obtained by using a ratio of para-phenylenediamine to ammonium heptamolybdate from 1 : 1 to 5 : 1. The second product, [C6H9N2]4[NH4]2[Mo7O24] ⋅ 3 H2O, was obtained by using higher PPD ratios from 9 : 1 to 30 : 1. Our electrochemical testing revealed that the second product showed exceptional battery performance, with a high capacity of 1084 mAh/g at 100 mA/g after 150 cycles. The product reached maximum capacity after an induction phase, which can be explained by a combination of a conversion reaction with lithium to Li2MoO4 and an additional in situ polymerization of PPD. We are excited about the potential of this hybrid material for use in LIB applications.