| 1. |
- Gond, Ritambhara, et al.
(författare)
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Non-flammable liquid electrolytes for safe batteries
- 2021
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Ingår i: Materials Horizons. - : Royal Society of Chemistry. - 2051-6347 .- 2051-6355. ; 8:11, s. 2913-2928
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Tidskriftsartikel (refereegranskat)abstract
- With continual increments in energy density gradually boosting the performance of rechargeable alkali metal ion (e.g. Li+, Na+, K+) batteries, their safe operation is of growing importance and needs to be considered during their development. This is essential, given the high-profile incidents involving battery fires as portrayed by the media. Such hazardous events result from exothermic chemical reactions occurring between the flammable electrolyte and the electrode material under abusive operating conditions. Some classes of non-flammable organic liquid electrolytes have shown potential towards safer batteries with minimal detrimental effect on cycling and, in some cases, even enhanced performance. This article reviews the state-of-the-art in non-flammable liquid electrolytes for Li-, Na- and K-ion batteries. It provides the reader with an overview of carbonate, ether and phosphate-based organic electrolytes, co-solvated electrolytes and electrolytes with flame-retardant additives as well as highly concentrated and locally highly concentrated electrolytes, ionic liquids and inorganic electrolytes. Furthermore, the functionality and purpose of the components present in typical non-flammable mixtures are discussed. Moreover, many non-flammable liquid electrolytes are shown to offer improved cycling stability and rate capability compared to conventional flammable liquid electrolytes.
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| 2. |
- 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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| 3. |
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| 4. |
- Kotronia, Antonia, et al.
(författare)
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Impact of Binders on Self-Discharge in Graphite Dual-Ion Batteries
- 2023
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Ingår i: Electrochemistry communications. - : Elsevier. - 1388-2481 .- 1873-1902. ; 146
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Tidskriftsartikel (refereegranskat)abstract
- This article offers insight into the role of binders in the overall performance of a dual-ion battery (DIB). Replacing sodium carboxymethyl cellulose (CMC) with poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) enhances the interfacial stability of a graphite positive electrode in a DIB. Electrochemical testing combined with X-ray photoelectron spectroscopy (XPS) and operando pressure measurements highlight that PVdF-HFP suppresses parasitic reactions at the cathode-electrolyte interface (CEI), in sharp contrast with CMC. However, CMC causes less interfacial resistance and is hence beneficial in terms of rate capability.
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| 5. |
- Mathew, Alma, et al.
(författare)
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Limitations of polyacrylic acid binders when employed in thick LNMO Li-ion battery electrodes
- 2024
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Ingår i: Journal of the Electrochemical Society. - : Institute of Physics Publishing (IOPP). - 0013-4651 .- 1945-7111. ; 171:2
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Tidskriftsartikel (refereegranskat)abstract
- Polyacrylic acid (PAA) is here studied as a binder material for LiNi0.5Mn1.5O4 (LNMO) cathodes for lithium-ion batteries. When the LNMO electrodes are fabricated with an active mass loading of similar to 10 mg cm-2 (similar to 1.5 mA h cm-2), poor discharge capacity and short cycle life is obtained in full-cells with graphite electrodes. The electrochemical results with PAA are compared with a commonly used water-based binder, sodium carboxymethyl cellulose (CMC), which shows better electrochemical performance. The main cause for these problems in PAA based cells is identified to be the high internal resistance in the initial cycles, caused by factors such as contact resistance, inhomogeneous binder distribution and poor electrolyte wetting of the active material.
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| 6. |
- Salian, Girish D., et al.
(författare)
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Understanding the electrochemical and interfacial behaviour of sulfolane-based electrolytes in LiNi0.5Mn1.5O4-graphite full-cells
- 2023
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Ingår i: Batteries & Supercaps. - : John Wiley & Sons. - 2566-6223. ; n/a:n/a
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Tidskriftsartikel (refereegranskat)abstract
- An ethylene carbonate-free electrolyte composed of 1 M lithium bis(fluorosulfonyl) imide (LiFSI) in sulfolane (SL) is studied here for LiNi0.5Mn1.5O4-graphite full-cells. An important focus on the evaluation of the anodic stability of the SL electrolyte and the passivation layers formed on LNMO and graphite is being analysed along with intermittent current interruption (ICI) technique to observe the resistance while cycling. The results show that the sulfolane electrolyte shows more degradation at higher potentials unlike previous reports which suggested higher oxidative stability. However, the passivation layers formed due to this electrolyte degradation prevents further degradation. The resistance measurements show that major resistance arises from the cathode. The pressure evolution during the formation cycles suggests that there is lower gas evolution with sulfolane electrolyte than in the conventional electrolyte. The study opens a new outlook on the sulfolane based electrolyte especially regarding its oxidative/anodic stability.
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| 7. |
- van Ekeren, Wessel, et al.
(författare)
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A comparative analysis of the influence of hydrofluoroethers as diluents on solvation structure and electrochemical performance in non-flammable electrolytes
- 2023
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 11:8, s. 4111-4125
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Tidskriftsartikel (refereegranskat)abstract
- To enhance battery safety, it is of utmost importance to develop non-flammable electrolytes. An emerging concept within this research field is the development of localized highly concentrated electrolytes (LHCEs). This type of liquid electrolyte relies on the concept of highly concentrated electrolytes (HCEs), but possesses lower viscosity, improved conductivity and reduced costs due to the addition of diluent solvents. In this work, two different hydrofluoroethers, i.e., bis(2,2,2-trifluoroethyl) ether (BTFE) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), are studied as diluents in a phosphate-based non-flammable liquid electrolyte. These two solvents were added to a highly concentrated electrolyte of 3.0 M lithium bis(fluorosulfonyl)imide (LiFSI) in triethyl phosphate (TEP) whereby the salt concentration was diluted to 1.5 M. The solvation structures of the HCE and LHCE were studied by means of Raman spectroscopy and Nuclear Magnetic Resonance (NMR) spectroscopy, where the latter was shown to be essential to provide more detailed insights. By using molecular dynamics simulations, it was shown that a highly concentrated Li+-TEP solvation sheath is formed, which can be protected by the diluents TTE and BTFE. These simulations have also clarified the energetic interaction between the components in the LHCE, which supports the experimental results from the viscosity and the NMR measurements. By performing non-covalent interaction analysis (NCI) it was possible to show the main contributions of the observed chemical shifts, which indicated that TTE has a stronger effect on the solvation structure than BTFE. Moreover, the electrochemical performances of the electrolytes were evaluated in half-cells (Li|NMC622, Li|graphite), full-cells (NMC622|graphite) and Li metal cells (Li|Cu). Galvanostatic cycling has shown that the TTE based electrolyte performs better in full-cells and Li-metal cells, compared to the BTFE based electrolyte. Operando pressure measurements have indicated that no significant amount of gases is evolved in NMC622|graphite cells using the here presented LHCEs, while a cell with 1.0 M LiFSI in TEP displayed clear formation of gaseous products in the first cycles. The formation of gaseous products is accompanied by solvent co-intercalation, as shown by operando XRD, and quick cell failure. This work provides insights on understanding the solvation structure of LHCEs and highlights the relationship between electrochemical performance and pressure evolution.
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| 10. |
- Welch, Jonas, et al.
(författare)
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Optimization of Sodium Bis(oxalato)borate (NaBOB) in Triethyl Phosphate (TEP) by Electrolyte Additives
- 2022
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Ingår i: Journal of the Electrochemical Society. - : Institute of Physics (IOP). - 0013-4651 .- 1945-7111. ; 169:12
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Tidskriftsartikel (refereegranskat)abstract
- The electrolyte solution of NaBOB in TEP is a low-cost, fluorine-free and flame-retardant electrolyte with ionic conductivity of 5 mS cm(-1), recently discovered to show promises for sodium-ion batteries. Here, the abilities of this electrolyte to effectively form a solid electrolyte interphase (SEI) was augmented with five common electrolyte additives of fluoroethylene carbonate (FEC), vinylene carbonate (VC), prop-1-ene-1,3-sultone (PES), 1,3,2-dioxathiolane 2,2-dioxide (DTD) and tris(trimethylsilyl)phosphite (TTSPi). Full-cells with electrodes of Prussian white and hard carbon and industrial mass loadings of >10 mg cm(-2) and electrolyte volumes of <5 ml g(-1) were used. X-ray photoelectron spectroscopy (XPS) and pressure analysis were also deployed to investigate parasitic reactions. Cells using electrolyte additives of PES, PES+DTD and PES+TTSPi (3 wt%) showed significantly increased performance in terms of capacity retention and initial Coulombic efficiency as compared to additive-free NaBOB-TEP. The best cell retained 80% discharge capacity (89 mAh g(-1)) after 450 cycles, which is also significantly better than reference cells using 1 M NaPF6 in EC:DEC electrolyte. This study sheds light on opportunities to optimize the NaBOB-TEP electrolyte for full-cell sodium-ion batteries in order to move from low-mass-loading lab-scale electrodes to high mass loading electrodes aiming for commercialization of sodium-ion batteries.
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