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| 2. |
- Nkosi, Funeka P., et al.
(författare)
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Garnet-Poly(epsilon-caprolactone-co-trimethylene carbonate) Polymer-in-Ceramic Composite Electrolyte for All-Solid-State Lithium-Ion Batteries
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:3, s. 2531-2542
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Tidskriftsartikel (refereegranskat)abstract
- A composite electrolyte based on a garnet electrolyte (LLZO) and polyester-based co-polymer (80:20 epsilon-caprolactone (CL)-trimethylene carbonate, PCL-PTMC with LiTFSI salt) is prepared. Integrating the merits of both ceramic and co-polymer electrolytes is expected to address the poor ionic conductivity and high interfacial resistance in solid-state lithium-ion batteries. The composite electrolyte with 80 wt % LLZO and 20 wt % polymer (PCL-PTMC and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) at 72:28 wt %) exhibited a Li-ion conductivity of 1.31 X 10(-4) S/cm and a transference number (t(Li+)) of 0.84 at 60 degrees C, notably higher than those of the pristine PCL-PTMC electrolyte. The prepared composite electrolyte also exhibited an electrochemical stability of up to 5.4 V vs Li+/Li. The interface between the composite electrolyte and a LiFePO4 (LFP) cathode was also improved by direct incorporation of the polymer electrolyte as a binder in the cathode coating. A Li/composite electrolyte/LFP solid-state cell provided a discharge capacity of ca. 140 mAh/g and suitable cycling stability at 55 degrees C after 40 cycles. This study clearly suggests that this type of amorphous polyester-based polymers can be applied in polymer-in-ceramic composite electrolytes for the realization of advanced all-solid-state lithium-ion batteries.
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| 3. |
- Nkosi, Funeka P., et al.
(författare)
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Understanding Lithium-Ion Conductivity in NASICON-Type Polymer-in-Ceramic Composite Electrolytes
- 2024
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 7:10, s. 4609-4619
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Tidskriftsartikel (refereegranskat)abstract
- Composite electrolytes comprising distinctive polyether (PEO) or polyester (PCL, P(CL-co-TMC)) polymers in combination with a high loading of Li1.4Al0.4Ti1.6(PO4)3 NASICON-type ceramic powders (LATP, 70 wt %) are investigated to gain insights into the limitations of their ion conductivity in resulting polymer-in-ceramic solid-state electrolyte systems. Here, LATP constitutes an advantageous ceramic Li-ion conductor with fair ionic conductivity that does not immediately suffer from limitations arising from interface issues due to the detrimental formation of surface species (e.g., Li2CO3) in contact with air and/or surrounding polymers. The Li-ion transport in all these composite electrolytes is found to follow a slow-motion regime in the polymer matrix, regardless of the nature of the polymer used. Interestingly, the weakly Li-coordinating polyester-based polymers PCL and P(CL-co-TMC) exhibit an exchange of Li+ ions between the polymer and ceramic phases and high Li-ion transference numbers compared to the polyether PEO matrix, which has strong Li–polymer coordination. LATP particle agglomeration is nevertheless observed in all the composite electrolytes, and this most likely represents a dominating cause for the lower Li-ion conductivity values of these composites when compared to those of their solid polymer electrolyte (SPE) counterparts. These findings add another step toward the development of functional composite electrolytes for all-solid-state batteries.
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| 4. |
- Xu, Chao, 1988-, et al.
(författare)
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Unraveling and Mitigating the Storage Instability of Fluoroethylene Carbonate-Containing LiPF6 Electrolytes To Stabilize Lithium Metal Anodes for High-Temperature Rechargeable Batteries
- 2019
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Ingår i: ACS Applied Energy Materials. - : AMER CHEMICAL SOC. - 2574-0962. ; 2:7, s. 4925-4935
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Tidskriftsartikel (refereegranskat)abstract
- Implementing Li metal anodes provides the potential of substantially boosting the energy density of current Li-ion battery technology. However, it suffers greatly from fast performance fading largely due to substantial volume change during cycling and the poor stability of the solid electrolyte interphase (SEI). Fluoroethylene carbonate (FEC) is widely acknowledged as an effective electrolyte additive for improving the cycling performance of batteries consisting of electrode materials that undergo large volume changes during cycling such as Li metal. In this study, we report that while FEC can form a robust SEI on the electrode, it also deteriorates the shelf life of electrolytes containing LiPF6. The degradation mechanism of LiPF6 in FEC solutions is unraveled by liquid-and solid-state NMR. Specifically, traces of water residues induce the hydrolysis of LiPF6, releasing HF and PF5 which further trigger ring-opening of FEC and its subsequent polymerization. These reactions are significantly accelerated at elevated temperatures leading to the formation of a three-dimensional fluorinated solid polymer network. Moisture scavenger additives, such as lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTDI), can delay the degradation reaction as well as improve the cycling stability of LiNi1/3Mn1/3Co1/3O2/Li metal batteries at 55 degrees C. This work highlights the poor shelf life of electrolytes containing FEC in combination with LiPF6 and thereby the great importance of developing proper storage methods as well as optimizing the content of FEC in practical cells.
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