| 1. |
- Jaradat, Ahmad, et al.
(författare)
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A High-Rate Li–CO2 Battery Enabled by 2D Medium-Entropy Catalyst
- 2023
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Ingår i: Advanced Functional Materials. - 1616-301X .- 1616-3028. ; 33:21
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-air batteries based on CO2 reactant (Li–CO2) have recently been of interest because it has been found that reversible Li/CO2 electrochemistry is feasible. In this study, a new medium-entropy cathode catalyst, (NbTa)0.5BiS3, that enables the reversible electrochemistry to operate at high rates is presented. This medium entropy cathode catalyst is combined with an ionic liquid-based electrolyte blend to give a Li–CO2 battery that operates at high current density of 5000 mA g−1 and capacity of 5000 mAh g−1 for up to 125 cycles, far exceeding reported values in the literature for this type of battery. The higher rate performance is believed to be due to the greater stability of the multi-element (NbTa)0.5BiS3 catalyst because of its higher entropy compared to previously used catalysts with a smaller number of elements with lower entropies. Evidence for this comes from computational studies giving very low surface energies (high surface stability) for (NbTa)0.5BiS3 and transmission electron microscopystudies showing the structure being retained after cycling. In addition, the calculations indicate that Nb-terminated surface promotes Li–CO2 electrochemistry resulting in Li2CO3 and carbon formation, consistent with the products found in the cell. These results open new direction to design and develop high-performance Li–CO2 batteries.
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| 2. |
- Majidi, Leily, et al.
(författare)
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Nanostructured Conductive Metal Organic Frameworks for Sustainable Low Charge Overpotentials in Li-Air Batteries
- 2022
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 18:4
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Tidskriftsartikel (refereegranskat)abstract
- Lithium–oxygen batteries are among the most attractive alternatives for future electrified transportation. However, their practical application is hindered by many obstacles. Due to the insulating nature of Li2O2 product and the slow kinetics of reactions, attaining sustainable low charge overpotentials at high rates becomes a challenge resulting in the battery's early failure and low round trip efficiency. Herein, outstanding characteristics are discovered of a conductive metal organic framework (c-MOF) that promotes the growth of nanocrystalline Li2O2 with amorphous regions. This provides a platform for the continuous growth of Li2O2 units away from framework, enabling a fast discharge at high current rates. Moreover, the Li2O2 structure works in synergy with the redox mediator (RM). The conductivity of the amorphous regions of the Li2O2 allows the RM to act directly on the Li2O2 surface instead of catalyst edges and then transport through the electrolyte to the Li2O2 surface. This direct charge transfer enables a small charge potential of <3.7 V under high current densities (1–2 A g−1) sustained for a long cycle life (100–300 cycles) for large capacities (1000–2000 mAh g−1). These results open a new direction for utilizing c-MOFs towards advanced energy storage systems.
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| 3. |
- Hemmat, Zahra, et al.
(författare)
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Unprecedented Multifunctionality in 1D Nb1-xTaxS3 Transition Metal Trichalcogenide Alloy
- 2022
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 32:34
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Tidskriftsartikel (refereegranskat)abstract
- 1D materials, such as nanofibers or nanoribbons are considered as the future ultimate limit of downscaling for modern electrical and electrochemical devices. Here, for the first time, nanofibers of a solid solution transition metal trichalcogenide (TMTC), Nb1-xTaxS3, are successfully synthesized with outstanding electrical, thermal, and electrochemical characteristics rivaling the performance of the-state-of-the art materials for each application. This material shows nearly unchanged sheet resistance (≈740 Ω sq−1) versus bending cycles tested up to 90 cycles, stable sheet resistance in ambient conditions tested up to 60 days, remarkably high electrical breakdown current density of ≈30 MA cm−2, strong evidence of successive charge density wave transitions, and outstanding thermal stability up to ≈800 K. Additionally, this material demonstrates excellent activity and selectivity for CO2 conversion to CO reaching ≈350 mA cm−2 at −0.8 V versus RHE with a turnover frequency number of 25. It also exhibits an excellent performance in a high-rate Li–air battery with the specific capacity of 3000 mAh g−1 at a current density of 0.3 mA cm−2. This study uncovers the multifunctionality in 1D TMTC alloys for a wide range of applications and opens a new direction for the design of the next generation low-dimensional materials.
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| 4. |
- Li, Biao, et al.
(författare)
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Capturing dynamic ligand-to-metal charge transfer with a long-lived cationic intermediate for anionic redox
- 2022
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Ingår i: Nature Materials. - : Springer Nature. - 1476-1122 .- 1476-4660. ; 21:10, s. 1165-1174
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Tidskriftsartikel (refereegranskat)abstract
- Reversible anionic redox reactions represent a transformational change for creating advanced high-energy-density positive-electrode materials for lithium-ion batteries. The activation mechanism of these reactions is frequently linked to ligand-to-metal charge transfer (LMCT) processes, which have not been fully validated experimentally due to the lack of suitable model materials. Here we show that the activation of anionic redox in cation-disordered rock-salt Li1.17Ti0.58Ni0.25O2 involves a long-lived intermediate Ni3+/4+ species, which can fully evolve to Ni2+ during relaxation. Combining electrochemical analysis and spectroscopic techniques, we quantitatively identified that the reduction of this Ni3+/4+ species goes through a dynamic LMCT process (Ni3+/4+–O2− → Ni2+–On−). Our findings provide experimental validation of previous theoretical hypotheses and help to rationalize several peculiarities associated with anionic redox, such as cationic–anionic redox inversion and voltage hysteresis. This work also provides additional guidance for designing high-capacity electrodes by screening appropriate cationic species for mediating LMCT.
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| 5. |
- Wang, Shuxi, et al.
(författare)
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Thermodynamics and Kinetics in Anisotropic Growth of One-Dimensional Midentropy Nanoribbons
- 2023
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Ingår i: ACS Nano. - 1936-0851 .- 1936-086X. ; 17:15, s. 15053-15064
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Tidskriftsartikel (refereegranskat)abstract
- One-dimensional (1D) materials demonstrate anisotropic in-plane physical properties that enable a wide range of functionalities in electronics, photonics, valleytronics, optoelectronics, and catalysis. Here, we undertake an in-depth study of the growth mechanism for equimolar midentropy alloy of (NbTaTi)0.33S3 nanoribbons as a model system for 1D transition metal trichalcogenide structures. To understand the thermodynamic and kinetic effects in the growth process, the energetically preferred phases at different synthesis temperatures and times are investigated, and the phase evolution is inspected at a sequence of growth steps. It is uncovered that the dynamics of the growth process occurs at four different stages via preferential incorporation of chemical species at high-surface-energy facets. Also, a sequence of temperature and time dependent nonuniform to uniform phase evolutions has emerged in the composition and structure of (NbTaTi)0.33S3 which is described based on an anisotropic vapor–solid (V–S) mechanism. Furthermore, direct evidence for the 3D structure of the charge density wave (CDW) phase (width less than 100 nm) is provided by three-dimensional electron diffraction (3DED) in individual nanoribbons at cryogenic temperature, and detailed comparisons are made between the phases obtained before and after CDW transformation. This study provides important fundamental information for the design and synthesis of future 1D alloy structures.
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