| 1. |
- Cavallo, Carmen, 1986, et al.
(författare)
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Effect of the Niobium Doping Concentration on the Charge Storage Mechanism of Mesoporous Anatase Beads as an Anode for High-Rate Li-Ion Batteries
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:1, s. 215-225
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Tidskriftsartikel (refereegranskat)abstract
- A promising strategy to improve the rate performance of Li-ion batteries is to enhance and facilitate the insertion of Li ions into nanostructured oxides like TiO2. In this work, we present a systematic study of pentavalent-doped anatase TiO2 materials for third-generation high-rate Li-ion batteries. Mesoporous niobium-doped anatase beads (Nb-doped TiO2) with different Nb5+ doping (n-type) concentrations (0.1, 1.0, and 10% at.) were synthesized via an improved template approach followed by hydrothermal treatment. The formation of intrinsic n-type defects and oxygen vacancies under RT conditions gives rise to a metallic-type conduction due to a shift of the Fermi energy level. The increase in the metallic character, confirmed by electrochemical impedance spectroscopy, enhances the performance of the anatase bead electrodes in terms of rate capability and provides higher capacities both at low and fast charging rates. The experimental data were supported by density functional theory (DFT) calculations showing how a different n-type doping can be correlated to the same electrochemical effect on the final device. The Nb-doped TiO2 electrode materials exhibit an improved cycling stability at all the doping concentrations by overcoming the capacity fade shown in the case of pure TiO2 beads. The 0.1% Nb-doped TiO2-based electrodes exhibit the highest reversible capacities of 180 mAh g-1 at 1C (330 mA g-1) after 500 cycles and 110 mAh g-1 at 10C (3300 mA g-1) after 1000 cycles. Our experimental and computational results highlight the possibility of using n-type doped TiO2 materials as anodes in high-rate Li-ion batteries.
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| 2. |
- Cengiz, Elif Ceylan, 1986, et al.
(författare)
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Review - Reference Electrodes in Li-Ion and Next Generation Batteries: Correct Potential Assessment, Applications and Practices
- 2021
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 168:12
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Forskningsöversikt (refereegranskat)abstract
- This review provides an accessible analysis of the processes on reference electrodes and their applications in Li-ion and next generation batteries research. It covers fundamentals and definitions as well as specific practical applications and is intended to be comprehensible for researchers in the battery field with diverse backgrounds. It covers fundamental concepts, such as two- and three-electrodes configurations, as well as more complex quasi- or pseudo- reference electrodes. The electrode potential and its dependance on the concentration of species and nature of solvents are explained in detail and supported by relevant examples. The solvent, in particular the cation solvation energy, contribution to the electrode potential is important and a largely unknown issue in most the battery research. This effect can be as high as half a volt for the Li/Li+ couple and we provide concrete examples of the battery systems where this effect must be taken into account. With this review, we aim to provide guidelines for the use and assessment of reference electrodes in the Li-ion and next generation batteries research that are comprehensive and accessible to an audience with a diverse scientific background.
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| 3. |
- Liu, Yangyang, et al.
(författare)
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Insight into the Critical Role of Exchange Current Density on Electrodeposition Behavior of Lithium Metal
- 2021
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Ingår i: Advanced Science. - : Wiley. - 2198-3844 .- 2198-3844. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- Due to an ultrahigh theoretical specific capacity of 3860 mAh g−1, lithium (Li) is regarded as the ultimate anode for high-energy-density batteries. However, the practical application of Li metal anode is hindered by safety concerns and low Coulombic efficiency both of which are resulted fromunavoidable dendrite growth during electrodeposition. This study focuses on a critical parameter for electrodeposition, the exchange current density, which has attracted only little attention in research on Li metal batteries. A phase-field model is presented to show the effect of exchange current density on electrodeposition behavior of Li. The results show that a uniform distribution of cathodic current density, hence uniform electrodeposition, on electrode is obtained with lower exchange current density. Furthermore, it is demonstrated that lower exchange current density contributes to form a larger critical radius of nucleation in the initial electrocrystallization that results in a dense deposition of Li, which is a foundation for improved Coulombic efficiency and dendrite-free morphology. The findings not only pave the way to practical rechargeable Li metal batteries but can also be translated to the design of stable metal anodes, e.g., for sodium (Na), magnesium (Mg), and zinc (Zn) batteries.
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| 4. |
- Sadd, Matthew, 1994
(författare)
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Operando Analysis of Materials and Processes in Next Generation Batteries
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the rise in popularity of electric vehicles and electromobility solutions, there is a higher than ever demand for high energy density batteries. Accompanying this increased demand there is also an increased pressure for lower costs, longer durability, and the use of more sustainable materials. Going beyond the constraints imposed by the Li-ion battery, Next Generation Batteries, encompassing a host of technologies and chemistries, have the potential to provide higher energy densities, while using more sustainable materials and at a lower cost. When exploring Next Generation Battery technologies novel materials and complex reactions are introduced underpinning the working mechanisms of energy storage. To move these technologies closer to realisation, a clear understanding of materials and processes during operation need to be established. To achieve this goal, investigations using operando characterisation techniques, measurements that are made during battery charge and discharge, provide a unique tool to advance the understanding of how a given battery technology works. This thesis explores the use operando analysis methods to reveal the inner workings of three key next generation battery technologies; Na-ion anodes and how the electrode structure can be tuned to facilitate Na ion intercalation, how Lithium-Sulfur cathodes evolve during cell cycling and the subsequent conversion of polysulfide species, and finally the structures observed when using Lithium-Metal as an anode for high-capacity batteries. The focus is to determine structural changes to electrode materials using X-ray Tomographic Microscopy, and chemical changes using Raman Spectroscopy with the aim to reveal mechanisms controlling the performance in terms of capacity, rate capability or cycling stability. Though operando measurements present an exciting opportunity to monitor process in real time, they need to be grounded in reality, thus this thesis explores supporting work, such as ex situ measurements, electrochemical evaluations, and traditional characterisation methods used in battery research, all used to determine the complex and dynamic processes that dictate how batteries perform.
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| 5. |
- Sun, Jinhua, 1987, et al.
(författare)
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Real-time imaging of Na+ reversible intercalation in "Janus" graphene stacks for battery applications
- 2021
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Ingår i: Science advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:22
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Tidskriftsartikel (refereegranskat)abstract
- Sodium, in contrast to other metals, cannot intercalate in graphite, hindering the use of this cheap, abundant element in rechargeable batteries. Here, we report a nanometric graphite-like anode for Na+ storage, formed by stacked graphene sheets functionalized only on one side, termed Janus graphene. The asymmetric functionalization allows reversible intercalation of Na+, as monitored by operando Raman spectroelectrochemistry and visualized by imaging ellipsometry. Our Janus graphene has uniform pore size, controllable functionalization density, and few edges; it can store Na+ differently from graphite and stacked graphene. Density functional theory calculations demonstrate that Na+ preferably rests close to -NH2 group forming synergic ionic bonds to graphene, making the interaction process energetically favorable. The estimated sodium storage up to C6.9Na is comparable to graphite for standard lithium ion batteries. Given such encouraging Na+ reversible intercalation behavior, our approach provides a way to design carbon-based materials for sodium ion batteries.
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