Filters

20223

More filters

20223
Reset filters

Settings

Author: Breitung, Ben × End date: 2022 × Start date: 2022 × End date: 2022 × Start date: 2022 ×

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Time‐Dependent Cation Selectivity of Titanium Carbide MXene in Aqueous Solution
    (Weinheim : Wiley-VCH, 2022) Wang, Lei; Torkamanzadeh, Mohammad; Majed, Ahmad; Zhang, Yuan; Wang, Qingsong; Breitung, Ben; Feng, Guang; Naguib, Michael; Presser, Volker
    Electrochemical ion separation is a promising technology to recover valuable ionic species from water. Pseudocapacitive materials, especially 2D materials, are up-and-coming electrodes for electrochemical ion separation. For implementation, it is essential to understand the interplay of the intrinsic preference of a specific ion (by charge/size), kinetic ion preference (by mobility), and crystal structure changes. Ti3C2Tz MXene is chosen here to investigate its selective behavior toward alkali and alkaline earth cations. Utilizing an online inductively coupled plasma system, it is found that Ti3C2Tz shows a time-dependent selectivity feature. In the early stage of charging (up to about 50 min), K+ is preferred, while ultimately Ca2+ and Mg2+ uptake dominate; this unique phenomenon is related to dehydration energy barriers and the ion exchange effect between divalent and monovalent cations. Given the wide variety of MXenes, this work opens the door to a new avenue where selective ion-separation with MXene can be further engineered and optimized.
  • Thumbnail Image
    Item
    High‐Entropy Sulfides as Electrode Materials for Li‐Ion Batteries
    (Weinheim : Wiley-VCH, 2022) Lin, Ling; Wang, Kai; Sarkar, Abhishek; Njel, Christian; Karkera, Guruprakash; Wang, Qingsong; Azmi, Raheleh; Fichtner, Maximilian; Hahn, Horst; Schweidler, Simon; Breitung, Ben
    High-entropy sulfides (HESs) containing 5 equiatomic transition metals (M), with different M:S ratios, are prepared by a facile one-step mechanochemical approach. Two new types of single-phase HESs with pyrite (Pa-3) and orthorhombic (Pnma) structures are obtained and demonstrate a homogeneously mixed solid solution. The straightforward synthesis method can easily tune the desired metal to sulfur ratio for HESs with different stoichiometries, by utilizing the respective metal sulfides, even pure metals, and sulfur as precursor chemicals. The structural details and solid solution nature of HESs are studied by X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma optical emission spectroscopy, and Mössbauer spectroscopy. Since transition metal sulfides are a very versatile material class, here the application of HESs is presented as electrode materials for reversible electrochemical energy storage, in which the HESs show high specific capacities and excellent rate capabilities in secondary Li-ion batteries.
  • Thumbnail Image
    Item
    P2-type layered high-entropy oxides as sodium-ion cathode materials
    (Bristol : IOP Science, 2022) Wang, Junbo; Dreyer, Sören L; Wang, Kai; Ding, Ziming; Diemant, Thomas; Karkera, Guruprakash; Ma, Yanjiao; Sarkar, Abhishek; Zhou, Bei; Gorbunov, Mikhail V; Omar, Ahmad; Mikhailova, Daria; Presser, Volker; Fichtner, Maximilian; Hahn, Horst; Brezesinski, Torsten; Breitung, Ben; Wang, Qingsong
    P2-type layered oxides with the general Na-deficient composition NaxTMO2 (x < 1, TM: transition metal) are a promising class of cathode materials for sodium-ion batteries. The open Na+ transport pathways present in the structure 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. Three different compositions of layered P2-type oxides were synthesized by solid-state chemistry, Na0.67(Mn0.55Ni0.21Co0.24)O2, Na0.67(Mn0.45Ni0.18Co0.24Ti0.1Mg0.03)O2 and Na0.67(Mn0.45Ni0.18Co0.18Ti0.1Mg0.03Al0.04Fe0.02)O2 with low, medium and high configurational entropy, respectively. The high-entropy cathode material shows lower structural transformation and Mn dissolution upon cycling in a wide voltage range from 1.5 to 4.6 V. Advanced operando techniques and post-mortem analysis were used to probe the underlying reaction mechanism thoroughly. 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.