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Asfaw, Habtom Desta, Dr.ORCID iD iconorcid.org/0000-0001-5861-4281
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Publications (10 of 18) Show all publications
Asfaw, H. D., Kotronia, A., Tai, C.-W., Nyholm, L. & Edström, K. (2019). Tailoring the Microstructure and Electrochemical Performance of 3D Microbattery Electrodes Based on Carbon Foams. Energy Technology, 7(10), Article ID UNSP 1900797.
Open this publication in new window or tab >>Tailoring the Microstructure and Electrochemical Performance of 3D Microbattery Electrodes Based on Carbon Foams
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2019 (English)In: Energy Technology, ISSN 0829-7681, E-ISSN 2057-4215, Vol. 7, no 10, article id UNSP 1900797Article in journal (Refereed) Published
Abstract [en]

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 μm are produced, and improvements are observed both in the coulombic efficiency and the cyclability of the carbon foam electrodes synthesized at 2200 °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 μA 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 μA cm−2 indicating that the materials are promising for power demanding applications.

Keywords
carbon foams, emulsions, lithium-ion storage, microbatteries, three-dimensional
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-393356 (URN)10.1002/ente.201900797 (DOI)000481541100001 ()
Funder
Swedish Research Council, 2012-4681Swedish Energy AgencyStandUpKnut and Alice Wallenberg Foundation
Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-11-04Bibliographically approved
Priimagi, P., Asfaw, H. D., Srivastav, S., Kasemagi, H., Aabloo, A., Brandell, D. & Zadin, V. (2018). Modeling 3D-microbatteries based on carbon foams. Electrochimica Acta, 281, 665-675
Open this publication in new window or tab >>Modeling 3D-microbatteries based on carbon foams
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2018 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 281, p. 665-675Article in journal (Refereed) Published
Abstract [en]

Porous electrodes are considered attractive for potential use as 3D current collectors in Li-ion microbatteries. Carbon foams, in particular, can be coated with a variety of active materials to prepare electrodes which can maximize energy and power density simultaneously. Modeling such electrodes will aid the selection of microstructural parameters (e.g. porosity) required to optimize their electrochemical performance. Here, experimentally-validated Finite Element Methodology (FEM) is used to simulate a 3D Li-ion microbattery featuring a carbon foam electrode coated by layers of LiFePO4 nanoparticles. The electrodes are cycled against Li-metal at various current densities, and the electrochemical data obtained are used to benchmark and parametrize the simulations. By systematic variation of the LiFePO4 coating thickness and homogeneity and the foam substrate, it is revealed that LiFePO4 exhibits a uniform delithiation process and that the electrochemical reactions favor particles closer to the carbon structure, which is due to the poor electrical conductivity of LiFePO4. Therefore, the cell capacity (mAh cm(-2)) per footprint area can be increased by using lower charging currents, smaller carbon macropore sizes and thicker LiFePO4 coatings. The porous carbon structure provides an excellent template for loadings of LiFePO4 material, which in turn allows using thicker coatings with improved cell performance.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keywords
3D-microbatteries, Electrochemistry modeling, Finite element methodology, Carbon foam
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-361489 (URN)10.1016/j.electacta.2018.05.179 (DOI)000439134600073 ()
Available from: 2018-09-27 Created: 2018-09-27 Last updated: 2018-09-27Bibliographically approved
Doubaji, S., Ma, L., Asfaw, H. D., Izanzar, I., Xu, R., Alami, J., . . . Saadoune, I. (2018). On the P2-NaxCo1−y(Mn2/3Ni1/3)yO2 Cathode Materials for Sodium-Ion Batteries: Synthesis, Electrochemical Performance, and Redox Processes Occurring during the Electrochemical Cycling. ACS Applied Materials and Interfaces, 10(1), 488-501
Open this publication in new window or tab >>On the P2-NaxCo1−y(Mn2/3Ni1/3)yO2 Cathode Materials for Sodium-Ion Batteries: Synthesis, Electrochemical Performance, and Redox Processes Occurring during the Electrochemical Cycling
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 1, p. 488-501Article in journal (Refereed) Published
Abstract [en]

P2-type NaMO2sodiated layered oxides withmixed transition metals are receiving considerable attention foruse as cathodes in sodium-ion batteries. A study on solidsolution (1−y)P2-NaxCoO2−(y)P2-NaxMn2/3Ni1/3O2(y=0,1/3, 1/2, 2/3, 1) reveals that changing the composition of thetransition metals affects the resulting structure and the stabilityof pure P2 phases at various temperatures of calcination. For 0≤y≤1.0, the P2-NaxCo(1−y)Mn2y/3Niy/3O2solid-solutioncompounds deliver good electrochemical performance whencycled between 2.0 and 4.2 V versus Na+/Na with improved capacity stability in long-term cycling, especially for electrodematerials with lower Co content (y= 1/2 and 2/3), despite lower discharge capacities being observed. The (1/2)P2-NaxCoO2−(1/2)P2-NaxMn2/3Ni1/3O2composition delivers a discharge capacity of 101.04 mAh g−1with a capacity loss of only 3% after 100cycles and a Coulombic efficiency exceeding 99.2%. Cycling this material to a higher cutoffvoltage of 4.5 V versus Na+/Naincreases the specific discharge capacity to≈140 mAh g−1due to the appearance of a well-defined high-voltage plateau, but afteronly 20 cycles, capacity retention declines to 88% and Coulombic efficiency drops to around 97%. In situ X-ray absorption near-edge structure measurements conducted on composition NaxCo1/2Mn1/3Ni1/6O2(y= 1/2) in the two potential windows studiedhelp elucidate the operating potential of each transition metal redox couple. It also reveals that at the high-voltage plateau, all ofthe transition metals are stable, raising the suspicion of possible contribution of oxygen ions in the high-voltage plateau.

Keywords
Na-ion batteries, P2-type materials, energy storage, in situ XANES measurements, high-voltage plateau
National Category
Natural Sciences Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-337712 (URN)10.1021/acsami.7b13472 (DOI)000422814400053 ()29098854 (PubMedID)
Funder
StandUpSwedish Research Council, 2015-05106
Available from: 2018-01-03 Created: 2018-01-03 Last updated: 2018-02-28Bibliographically approved
Sun, B., Asfaw, H. D., Rehnlund, D., Mindemark, J., Nyholm, L., Edström, K. & Brandell, D. (2018). Towards Solid-State 3D-Microbatteries using Functionalized Polycarbonate-based Polymer Electrolytes. ACS Applied Materials and Interfaces, 10(3), 2407-2413
Open this publication in new window or tab >>Towards Solid-State 3D-Microbatteries using Functionalized Polycarbonate-based Polymer Electrolytes
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 3, p. 2407-2413Article in journal (Refereed) Published
Abstract [en]

3D-microbatteries (3D-MBs) impose new demands for theselection, fabrication and compatibility of the different battery components, notleast the electrolytes. Herein, solid polymer electrolytes (SPEs) based on poly(trimethylene carbonate) (PTMC) have been implemented in 3D-MB systems. 3D electrodes of two different architectures, LiFePO4-coated carbon foams and Cu2O-coated Cu nanopillars, have been coated with SPEs and used in Li-cells. Functionalized PTMC with hydroxyl end groups was found to enable uniform and well-covering coatings on LiFePO4-coated carbon foams, although the cell cycling performance was limited by the large SPE resistance. By employing a SPE prepared from a copolymer of TMC and caprolactone (CL), with higher ionic conductivity, Li-cells composed of Cu2O-coated Cu nanopillars were constructed and tested both at room temperature and 60 °C. The footprint areal capacity of the cells was ca. 0.02 mAh cm-2 for an area gain factor (AF) of 2.5, and 0.2 mAh cm-2 for a relatively dense nanopillar-array (AF=25) at a current density of 0.008 mA cm-2at ambient temperature (22±1 °C). These results provide new routes towards the realization of all-solid-state 3D-MBs.

Keywords
Li-battery, 3D-microbattery, polymer electrolyte, nanopillars, carbon foam, Cu2O, Cu, nanorods
National Category
Inorganic Chemistry Materials Chemistry
Research subject
Chemistry with specialization in Organic Chemistry; Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-336964 (URN)10.1021/acsmi.7b13788 (DOI)000423496500027 ()29199816 (PubMedID)
Funder
StandUp
Available from: 2017-12-19 Created: 2017-12-19 Last updated: 2018-03-16Bibliographically approved
Kotronia, A., Asfaw, H. D., Brandell, D. & Edström, K. (2017). CaS- and MgS-assisted graphitization of porous carbons for energy storage applications. In: : . Paper presented at Oorgandagarna 2017.
Open this publication in new window or tab >>CaS- and MgS-assisted graphitization of porous carbons for energy storage applications
2017 (English)Conference paper