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).
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.
Volker Presser was honored for the work on electrochemical water remediation and Lithium-ion extraction by the City of Saarbrücken. Read more about the event and all awardees.
Volker Presser presents our team’s work on Lithium-ion harvesting from aqueous media, including mine water, at a symposium organized by the Saarlandian Chamber of Commerce and Industry (IHK) on circularity and battery recycling.
Our work on lithium-ion recovery from aqueous media (including seawater) was featured by the local radio station SR3.
https://www.sr.de/sr/sr3/themen/panorama/wissenschaftler_leibniz_institut_lithiumgewinnung_100.html
It is a privilege to receive, after 2018 and 2021, the recognition as 2022 Highly Cited Researcher (HRC) by Clarivate. Only 6,938 out of abut 8M researchers have received this recognition. Citation numbers are not the most important parameter in science, but I am grateful to our team and collaborators that the community so well receives our works. I am also honored to be the only 2022 HRC of Saarland University and only 1 of 2 if counting the University Hospital, too.
New paper published in Carbon. This is our latest work from our collaboration with our Austrian partners now being published in the January issue of Carbon. Combining the expertise in catalysis of the Eder group (TU Vienna) with the innovative carbon spherogel material developed by Michael Elsaesser from the Hüsing Group (Paris Lodron Universität Salzburg) makes up for an interesting system. Spherogels are hollow carbon spheres which, as shown by this work, can be conveniently loaded with electrocatalytically active species, such as titania. In our case, we studied the photocatalytic hydrogen evolution.
After a lot of work by our Ph.D. students Stefanie Arnold and Lei Wang, our invited article in the Wiley journal SMALL on the dual-use of seawater batteries for energy storage and water desalination. Seawater batteries are a unique type of device that capitalizes, in the most common design, on a ceramic separator, an electrocatalytic reaction on one electrode side, and reversible sodium-ion electrochemistry on the other side. Since simple seawater can be used as the aqueous electrolyte in the system, the system has become known as seawater batteries. In our opinion, this technology can do more than contribute toward beyond-lithium energy storage by also being used for desalination.
New paper published in ACS Omega. Batteries employing transition-metal sulfides enable high-charge storage capacities, but polysulfide shuttling and volume expansion cause structural disintegration and early capacity fading. The design of heterostructures combining metal sulfides and carbon with an optimized morphology can effectively address these issues. Our work introduces dopamine-coated copper Prussian blue (CuPB) analogue as a template to prepare nanostructured mixed copper–iron sulfide electrodes. The material was prepared by coprecipitation of CuPB with in situ dopamine polymerization, followed by thermal sulfidation. Dopamine controls the particle size and favors K-rich CuPB due to its polymerization mechanism. While the presence of the coating prevents particle agglomeration during thermal sulfidation, its thickness demonstrates a key effect on the electrochemical performance of the derived sulfides. After a two-step activation process during cycling, the C-coated KCuFeS2 electrodes showed capacities up to 800 mAh/g at 10 mA/g with nearly 100% capacity recovery after rate handling and a capacity of 380 mAh/g at 250 mA/g after 500 cycles.
I am honored to receive the 2022 Zhaowu Tian Prize for Energy Electrochemistry. This award by the International Society of Electrochemistry recognizes the achievements in the field of electrochemistry for energy of my team and I. I am fortunate to join the list of awardees which includes from past years Xiangfeng Duan (2017), Fabio la Mantia (2018), Zhichuan (Jason) Xu (2019), and Joaquín Rodríguez-López (2021). Coming in the year of my 40th birthday and the 10-year-anniversary of being a PI at the INM – Leibniz Institute for New Materials, I am grateful to not just my team but also our esteemed collaborators, especially dear friends such as Michael Naguib, Guang Feng, Christian Prehal, Yury Gogotsi, Veronica Augustyn, and so many more!
New paper published in Electrochimica Acta on Ni-decorated AgAu alloy graphene/cobalt hydroxide electrodes for micro-supercapacitors to obtain high-performance micro-supercapacitors. A nanocomposite of graphene, cobalt hydroxide and nickel can was obtained from using gold-silver alloy lines. Using a two-step electrodeposition method, the scaly morphology is pre-deposited on a Ni film, followed by the interconnecting corrugated graphene/cobalt hydroxide composite nanomaterial. The resulting device, a graphene/cobalt hydroxide/Ni//activated carbon flexible micro-supercapacitor (MSC), was assembled by gel KOH-PVA electrolyte, graphene/cobalt hydroxide/Ni (positive electrode), and activated carbon (negative electrode). When testing, we obtained a volumetric energy of about 19 mWh/cm3 and the devices retained over 94% capacitance after 10,000 cycles. After 1,000 continuous bending/unbending cycles at a 180° bending angle with the frequency of 100 mHz, the capacitance retention of MSC is still maintained at 97% of the initial value.
Welcome to our new Postdoc Dr. Kaitlyn Prenger! Kaitlyn is a graduate of Tulane University from the esteemed team of Michael Naguib and will work on novel 2D (and other) materials for sustainable electrochemical applications.
Stefanie Arnold gives an oral presentation with the title “Design Matters: The Path to High-Performance Antimony / MXene Hybrid Electrodes for Sodium-Ion Batteries” at the MSE2022 conference in Darmstadt. This was joint work with Riccardo Ruffo‘s team and Stefano Marchionna (Italy).
new paper published in ACS Energy Letters on continuous electrochemical lithium-ion extraction. We used a redox electrolyte “engine” to drive the ion transfer (in our case: potassium ferricyanide). Employing a pair of ceramic lithium superionic conductor (LISICON) membranes meant that only Lithium ions were accessible to the redox electrolyte for charge compensation. And to complement the design, we used an anion exchange membrane to separate the inflow (e.g., seawater) from a recovery solution. By this way, we obtained an electrochemical system for the continuous extraction of Lithium ions. This sets this technology apart from earlier works (including our contributions) that relied on a cyclic operation to obtain ion separation. Yet, this is just one of many more steps towards seeing such technology toward application; future research must critically address cell design, optimization of the Li-membranes, and investigating the robustness and durability of continuous operation.
This work was the result of the collaboration of our Ph.D. students Lei Wang, Stefanie Arnold, Panyu Ren, and our former Postdoc (now group leader at Bavarian Center for Battery Technology (BayBatt)) Qingsong Wang, as well as our Chinese collaborators Jun Jin and Zahoyin Wen (Chinese Academy of Sciences).
New paper published in Materials Futures. Sodium-deficient, P2-type layered oxides are promising cathodes for sodium-ion batteries. Their open sodium cation transport pathways lead to low diffusion barriers and enable high charge/discharge rates. However, a phase transition from P2 to O2 structure occurring above 4.2 V and metal dissolution at low potentials upon discharge results in rapid capacity degradation. In this work, we demonstrate the positive effect of configurational entropy on the stability of the crystal structure during battery operation. The high-entropy cathode material shows lower structural transformation and Mn dissolution upon cycling in a wide voltage range from 1.5 V to 4.6 V. Advanced operando techniques and post-mortem analysis were used to thoroughly probe the underlying reaction mechanism. Overall, the high-entropy strategy is a promising route for improving the electrochemical performance of P2 layered oxide cathodes for advanced sodium-ion battery applications.
New paper published in Desalination on the ion selectivity of carbon nanopores. It is well known that electrolyte confinement inside carbon nanopores strongly affects ion electrosorption in capacitive deionization. A thorough understanding of the intricate pore size influence enables enhanced charge storage performance and desalination in addition to ion separation. In subnanometer pores, where the pore size is smaller than hydrated ion size, a dehydration energy barrier must be overcome before the ions can be electrosorbed into the pores. Ion sieving is observed when the dehydration energy is larger than the applied energy. However, when a high electrochemical potential is used, the ions can desolvate and enter the pores. Capitalizing on the difference in size and dehydration energy barriers, this work applies the subnanometer porous carbon material, and a high electrochemical ion selectivity for Cs+ and K+ over Na+, Li+, Mg2+, and Ca2+ is observed. This establishes a viable way for selective heavy metal removal by varying pore and solvated ion sizes. Our work also shows the transition from double-layer capacitance to diffusion-limited electrochemical features in narrow ultramicropores.
Behnoosh Bornamehr gives an oral presentation on her research on electrospinning. Her talk is aptly titled “Too fast, too brittle: a study on heat treatment parameters for free-standing vanadium oxide electrodes”.
Welcome new Ph.D. student Jean Gustavo De Andrade Ruthes! Jean is from the Universidade Federal do Paraná, Brazil, and will be working on MXene / graphene batteries within our Czech-German research collaboration.