| 1. |
- Asfaw, Habtom Desta, Dr. 1986-, et al.
(författare)
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A polymeric cathode-electrolyte interface enhances the performance of MoS2-graphite potassium dual-ion intercalation battery
- 2022
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Ingår i: Cell Reports Physical Science. - : Elsevier. - 2666-3864. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Anion intercalation in the graphite cathode of a dual-ion battery (DIB) occurs at unusually high voltage (>4.5 V K+/K). This exacerbates electrolyte degradation and corrosion of Al current collectors, leading to poor coulombic efficiency (CE), typically <90%, and short cell life as a result. These limitations can be mitigated if a stable cathode-electrolyte interface layer (CEI) can form on the graphite electrode. In this study, we demonstrate that the performance of a potassium-based DIB can be improved with a triallyl phosphate (TAP) monomer added in 6 m KN(SO2CF3)2 (KTFSI)-dimethyl carbonate (DMC) electrolyte. The TAP additive forms a stable polymeric CEI on the graphite particles and thus increases the CE of the cell to 97%–99%. Together with MoS2-negative electrodes with a pre-formed solid electrolyte interphase (SEI) layer, the DIB concept has been shown to offer specific capacities from ∼40 to 80 mAh g−1 with an average discharge voltage of 3.7 V.
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| 2. |
- Asfaw, Habtom D., Dr. 1986-, et al.
(författare)
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Bio-derived hard carbon nanosheets with high rate sodium-ion storage characteristics
- 2022
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Ingår i: Sustainable Materials and Technologies. - : Elsevier. - 2214-9937. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- Biomass is a sustainable precursor of hard carbons destined for use in sodium-ion batteries. This study explores the synthesis of hard carbon nanosheets (HCNS) from oxidized cork and impact of synthesis temperature on the hard carbon characteristics. An increase in the carbonization temperature from 1000 to 1500 °C generally leads to lower BET specific surface areas (~55 to 20 m2 g−1) and d002 interlayer spacing (~ 4.0 to 3.7 Å). The effect of synthesis temperature is reflected in the initial coulombic efficiency (iCE) which increases from 72% at 1000 °C to 88% at 1500 °C, as a result of the decrease in surface area, and structural defects in the hard carbon as verified using Raman scattering. The impact of cycling temperature (~25, 30 and 55 °C) on the rate capability and long-term cycling is investigated using high precision coulometry cycler. For a galvanostatic test at 20 mA g−1 and ~ 25 °C, a reversible capacity of 276 mAh g−1 is observed with an iCE of ~88%. Increasing cycling temperature enhances the rate performance, but slightly lowers the iCE (~86% at 30 °C and ~ 81% at 55 °C). At 20 mA g−1, the reversible capacities obtained at 30 °C and 55 °C are on average ~ 260 and ~ 270 mAh g−1, respectively. For constant-current constant-voltage (CCCV) tests conducted at 30 °C, reversible capacities ranging from 252 to 268, 247–252, and 237–242 mAh g−1 can be obtained at 10, 100, and 1000 mA g−1, respectively. The respective capacities obtained at 55 °C are about 272–290, 260–279, and 234–265 mAh g−1 at 10, 100 and 1000 mA g−1. The applicability of the HCNS electrodes is eventually evaluated in full-cells with Prussian white cathodes, for which a discharge capacity of 152 mAh g−1 is obtained with an iCE of ~90%.
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| 3. |
- Asfaw, Habtom D., 1986-, et al.
(författare)
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Charting the course to solid-state dual-ion batteries
- 2023
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Ingår i: Carbon Energy. - : John Wiley & Sons. - 2637-9368 .- 2637-9368.
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Forskningsöversikt (refereegranskat)abstract
- An electrolyte destined for use in a dual-ion battery (DIB) must be stable at the inherently high potential required for anion intercalation in the graphite electrode, while also protecting the Al current collector from anodic dissolution. A higher salt concentration is needed in the electrolyte, in comparison to typical battery electrolytes, to maximize energy density, while ensuring acceptable ionic conductivity and operational safety. In recent years, studies have demonstrated that highly concentrated organic electrolytes, ionic liquids, gel polymer electrolytes (GPEs), ionogels, and water-in-salt electrolytes can potentially be used in DIBs. GPEs can help reduce the use of solvents and thus lead to a substantial change in the Coulombic efficiency, energy density, and long-term cycle life of DIBs. Furthermore, GPEs are suited to manufacture compact DIB designs without separators by virtue of their mechanical strength and electrical performance. In this review, we highlight the latest advances in the application of different electrolytes in DIBs, with particular emphasis on GPEs.
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| 4. |
- Asfaw, Habtom Desta, Dr. 1986-, et al.
(författare)
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Tailoring the Microstructure and Electrochemical Performance of 3D Microbattery Electrodes Based on Carbon Foams
- 2019
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Ingår i: Energy Technology. - : Wiley. - 2194-4288 .- 2194-4296.
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Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional (3D) carbon electrodes with suitable microstructural features and stable electrochemical performance are required for practical applications in 3D lithium (Li)-ion batteries. Herein, the optimization of the microstructures and electrochemical performances of carbon electrodes derived from emulsion-templated polymer foams are dealt with. Exploiting the rheological properties of the emulsion precursors, carbon foams with variable void sizes and specific surface areas are obtained. Carbon foams with an average void size of around 3.8 mu m are produced, and improvements are observed both in the coulombic efficiency and the cyclability of the carbon foam electrodes synthesized at 2200 degrees C. A stable areal capacity of up to 1.22 mAh cm(-2) (108 mAh g(-1)) is achieved at a current density of 50 mu A cm(-2). In addition, the areal capacity remains almost unaltered, i.e., 1.03 mAh cm(-2) (91 mAh g(-1)), although the cycling current density increases to 500 mu A cm(-2) indicating that the materials are promising for power demanding applications.
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| 5. |
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| 6. |
- Hassan, Ismail Yussuf, et al.
(författare)
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Monitoring Self-discharge in a Dual-ion Battery Using In Situ Raman Spectro-electrochemistry
- 2023
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Ingår i: Materials Research Express. - : Institute of Physics Publishing (IOPP). - 2053-1591. ; 10:11
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Tidskriftsartikel (refereegranskat)abstract
- A dual-ion battery employs two graphite electrodes to host cations and anions from the electrolyte. The high potential required to intercalate anions in graphite fully, typically > 5 V versus Li+/Li, triggers electrolyte decomposition and dissolution of the aluminium current collector. Such unwanted reactions significantly aggravate self-discharge, leading to low energy efficiency and shorter cycle life. This study investigates changes in graphite structure during the intercalation of bis(fluorosulfonyl)imide (FSI) anion in 4 M LiFSI in ethyl methyl carbonate (EMC) and evaluates the stability of the associated FSI-intercalated graphite compounds using in situ Raman spectroscopy. The results highlight the critical importance of the duration the GICs remain in contact with the electrolyte, before the acquisition of the Raman spectra. Accordingly, the GICs with high FSI anion content exhibited only short-term stability and lost anions during open-circuit potential relaxation; only dilute GIC phases (stages ≥ IV) were sufficiently stable in the presence of the concentrated electrolyte. Furthermore, the formation of gaseous products during the charge–discharge cycles was verified using a 3-electrode cell with a pressure sensor. Future studies can adopt the experimental strategy developed in this work to assess the efficacy of electrolyte additives in mitigating self-discharge in DIBs.
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| 7. |
- Koriukina, Tatiana, 1994-, et al.
(författare)
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On the Use of Ti3C2TX MXene as a Negative Electrode Material for Lithium-Ion Batteries
- 2022
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7:45, s. 41696-41710
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Tidskriftsartikel (refereegranskat)abstract
- The pursuit of new and better battery materials has given rise to numerous studies of the possibilities to use two-dimensional negative electrode materials, such as MXenes, in lithium-ion batteries. Nevertheless, both the origin of the capacity and the reasons for significant variations in the capacity seen for different MXene electrodes still remain unclear, even for the most studied MXene: Ti3C2Tx. Herein, freestanding Ti3C2Tx MXene films, composed only of Ti3C2Tx MXene flakes, are studied as additive-free negative lithium-ion battery electrodes, employing lithium metal half-cells and a combination of chronopotentiometry, cyclic voltammetry, X-ray photoelectron spectroscopy, hard X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy experiments. The aim of this study is to identify the redox reactions responsible for the observed reversible and irreversible capacities of Ti3C2Tx- based lithium-ion batteries as well as the reasons for the significant capacity variation seen in the literature. The results demonstrate that the reversible capacity mainly stems from redox reactions involving the Tx-Ti-C titanium species situated on the surfaces of the MXene flakes, whereas the Ti-C titanium present in the core of the flakes remains electro-inactive. While a relatively low reversible capacity is obtained for electrodes composed of pristine Ti3C2Tx MXene flakes, significantly higher capacities are seen after having exposed the flakes to water and air prior to the manufacturing of the electrodes. This is ascribed to a change in the titanium oxidation state at the surfaces of the MXene flakes, resulting in increased concentrations of Ti(II), Ti(III), and Ti(IV) in the Tx-Ti-C surface species. The significant irreversible capacity seen in the first cycles is mainly attributed to the presence of residual water in the Ti3C2Tx electrodes. As the capacities of Ti3C2Tx MXene negative electrodes depend on the concentration of Ti(II), Ti(III), and Ti(IV) in the Tx-Ti-C surface species and the water content, different capacities can be expected when using different manufacturing, pretreatment, and drying procedures.
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