| 1. |
- Hernández, Guiomar, et al.
(författare)
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Fluorine-Free Electrolytes for Lithium and Sodium Batteries
- 2022
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Ingår i: Batteries & Supercaps. - : John Wiley & Sons. - 2566-6223. ; 5:6
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Forskningsöversikt (refereegranskat)abstract
- Fluorinated components in the form of salts, solvents and/or additives are a staple of electrolytes for high-performance Li- and Na-ion batteries, but this comes at a cost. Issues like potential toxicity, corrosivity and environmental concerns have sparked interest in fluorine-free alternatives. Of course, these electrolytes should be able to deliver performance that is on par with the electrolytes being in use today in commercial batteries. This begs the question: Are we there yet? This review outlines why fluorine is regarded as an essential component in battery electrolytes, along with the numerous problems it causes and possible strategies to eliminate it from Li- and Na-ion battery electrolytes. The examples provided demonstrate the possibilities of creating fully fluorine-free electrolytes with similar performance as their fluorinated counterparts, but also that there is still a lot of room for improvement, not least in terms of optimizing the fluorine-free systems independently of their fluorinated predecessors.
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| 2. |
- Mathew, Alma, et al.
(författare)
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Understanding the Capacity Fade in Polyacrylonitrile Binder-based LiNi0.5Mn1.5O4 Cells
- 2022
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Ingår i: Batteries & Supercaps. - : John Wiley & Sons. - 2566-6223. ; 5:12
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Binders are electrochemically inactive components that have a crucial impact in battery ageing although being present in only small amounts, typically 1?3?% w/w in commercial products. The electrochemical performance of a battery can be tailored via these inactive materials by optimizing the electrode integrity and surface chemistry. Polyacrylonitrile (PAN) for LiNi0.5Mn1.5O4 (LNMO) half-cells is here investigated as a binder material to enable a stable electrode-electrolyte interface. Despite being previously described in literature as an oxidatively stable polymer, it is shown that PAN degrades and develops resistive layers within the LNMO cathode. We demonstrate continuous internal resistance increase in LNMO-based cells during battery operation using intermittent current interruption (ICI) technique. Through a combination of on-line electrochemical mass spectrometry (OEMS) and X-ray photoelectron spectroscopy (XPS) characterization techniques, the degradation products can be identified as solid on the LNMO electrode surface, and no excessive gas formation seen. The increased resistance and parasitic processes are correlated to side-reactions of the PAN, possibly intramolecular cyclization, which can be identified as the main cause of the comparatively fast capacity fade.
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| 3. |
- Sångeland, Christofer, et al.
(författare)
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Dissecting the solid polymer electrolyte–electrode interface in the vicinity of electrochemical stability limits
- 2022
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:25, s. 28716-28728
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Tidskriftsartikel (refereegranskat)abstract
- Proper understanding of solid polymer electrolyte–electrode interfacial layer formation and its implications on cell performance is a vital step toward realizing practical solid-state lithium-ion batteries. At the same time, probing these solid–solid interfaces is extremely challenging as they are buried within the electrochemical system, thereby efficiently evading exposure to surface-sensitive spectroscopic methods. Still, the probing of interfacial degradation layers is essential to render an accurate picture of the behavior of these materials in the vicinity of their electrochemical stability limits and to complement the incomplete picture gained from electrochemical assessments. In this work, we address this issue in conjunction with presenting a thorough evaluation of the electrochemical stability window of the solid polymer electrolyte poly(ε-caprolactone):lithium bis(trifluoromethanesulfonyl)imide (PCL:LiTFSI). According to staircase voltammetry, the electrochemical stability window of the polyester-based electrolyte was found to span from 1.5 to 4 V vs Li+/Li. Subsequent decomposition of PCL:LiTFSI outside of the stability window led to a buildup of carbonaceous, lithium oxide and salt-derived species at the electrode–electrolyte interface, identified using postmortem spectroscopic analysis. These species formed highly resistive interphase layers, acting as major bottlenecks in the SPE system. Resistance and thickness values of these layers at different potentials were then estimated based on the impedance response between a lithium iron phosphate reference electrode and carbon-coated working electrodes. Importantly, it is only through the combination of electrochemistry and photoelectron spectroscopy that the full extent of the electrochemical performance at the limits of electrochemical stability can be reliably and accurately determined.
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| 6. |
- Sångeland, Christofer, et al.
(författare)
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Probing the interfacial chemistry of solid-state lithium batteries
- 2019
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Ingår i: Solid State Ionics. - : Elsevier. - 0167-2738 .- 1872-7689. ; 343
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Forskningsöversikt (refereegranskat)abstract
- This review aims to give a brief overview of the current state-of-the-art in the analysis of the interfacial chemistry in solid-state batteries. Despite generally regarded as being decisive for the ultimate success of these energy storage devices, this surface chemistry has so far only been explored to a rather limited extent in the scientific literature, but constitutes a research area which is currently undergoing rapid progress due to the growing interest in solid-state electrolyte materials and their corresponding battery applications. The review discusses the technical difficulties in performing these interfacial analyses for both ceramic and solid polymer electrolyte systems, and describes ways to overcome them using different methodologies: electrochemical techniques (primarily impedance spectroscopy), photoelectron spectroscopy, microscopy, and other less familiar experimental techniques. Modelling studies of the solid electrolyte-electrode interface are also included. It is concluded that especially the interfacial chemistry of polymer electrolytes has indeed been an understudied area. Furthermore, the review shows that analytical techniques employed so far have been largely complimentary to each other, but that joint studies and the development of novel analytical tools exploiting large-scale facilities will boost this research over the coming years.
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| 7. |
- Sångeland, Christofer, et al.
(författare)
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Towards room temperature operation of all-solid-state Na-ion batteries through polyester-polycarbonate-based polymer electrolytes
- 2019
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Ingår i: Energy Storage Materials. - : Elsevier BV. - 2405-8289 .- 2405-8297. ; 19, s. 31-38
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Tidskriftsartikel (refereegranskat)abstract
- In an ambition to develop solid-state Na-ion batteries functional at ambient temperature, we here explore a novel electrolyte system. Polyester-polycarbonate (PCL-PTMC) copolymers were combined with sodium bis(fluorosulfonyl) imide salt (NaFSI) to form solid polymer electrolytes for Na-ion batteries. The PCL-PTMC:NaFSI system demonstrated glass transition temperatures ranging from -64 to -11 degrees C, increasing with increasing salt content from 0 to 35 wt%, and ionic conductivities ranging from 10(-8) to 10(-5) S cm(-1) at 25 degrees C. The optimal salt concentration was clearly dependent on the level of crystallinity, which was largely determined by the CL content. At 70 and 80 mol% CL, the PCL-PTMC:NaFSI system was fully amorphous and exhibited high conductivities at lower salt concentrations. When the CL content was increased to 100 mol%, high ionic conductivities were instead observed at high salt concentrations. A decent transference number of ca. 0.5 at 80 degrees C was obtained for a polymer film containing 20 mol% CL units and 25 wt% NaFSI. Finally, a HC vertical bar 80-20(25)vertical bar Na2-xFe(Fe(CN)(6)) all-solid-state polymer electrolyte full cell was assembled to demonstrate the practical application of the material and cycled for more than 120 cycles at similar to 22 degrees C.
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