| 1. |
- Pan, Ruijun, et al.
(författare)
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Double-sided conductive separators for lithium-metal batteries
- 2019
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Ingår i: Energy Storage Materials. - : Elsevier. - 2405-8289 .- 2405-8297. ; 21, s. 464-473
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Tidskriftsartikel (refereegranskat)abstract
- A novel double-sided conductive (DSC) separator consisting of two 5 μm-thick carbon nanotube (CNT)/cellulose nanofiber (CNF) composite layers coated on each side of a 20 μm-thick glass-fiber (GF)/CNF composite membrane is described. In a lithium-metal battery (LMB), the DSC separator exhibits a high ionic conductivity (i.e. 1.7 mS cm−1 using an LP40 electrolyte) due to the high porosity (i.e. 66%) of the GF/CNF membrane. More stable Li anodes can also be realized by depositing Li within the porous electronically conducting CNT/CNF matrix at the DSC separator anode side due to the decreased current density. The CNT/CNF layer of the DSC separator facing the cathode, which is in direct electric contact with the current collector, decreases the overpotential for the cathode and consequently improves its capacity and rate performance significantly. A Li/Li cell containing a DSC separator showed an improved cycling stability compared to an analogous cell equipped with a commercial Celgard separator at current densities up to 5 mA cm−2 for Li deposition and stripping capacities up to 5 mAh cm−2. A proof-of-concept LMB containing a lithium iron phosphate (LFP) composite cathode and a DSC separator showed a significantly improved rate capability, yielding capacities of about 110 mAh g−1 at 5 C and 80 mAh g−1 at 10 C. The LMB cell containing a DSC separator also exhibited a capacity retention of 80% after 200 cycles at a rate of 6 C indicating that the two-sided conductive separator design has significant potential in facilitating the development of well-functioning LMBs.
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| 2. |
- Pan, Ruijun, et al.
(författare)
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Nanocellulose Modified Polyethylene Separators for Lithium Metal Batteries
- 2018
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Ingår i: Small. - : Wiley-VCH Verlagsgesellschaft. - 1613-6810 .- 1613-6829. ; 14:21
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Poor cycling stability and safety concerns regarding lithium (Li) metal anodes are two major issues preventing the commercialization of highâ€energy density Li metalâ€based batteries. Herein, a novel triâ€layer separator design that significantly enhances the cycling stability and safety of Li metalâ€based batteries is presented. A thin, thermally stable, flexible, and hydrophilic cellulose nanofiber layer, produced using a straightforward paperâ€making process, is directly laminated on each side of a plasmaâ€treated polyethylene (PE) separator. The 2.5 µm thick, mesoporous (≈20 nm average pore size) cellulose nanofiber layer stabilizes the Li metal anodes by generating a uniform Li+ flux toward the electrode through its homogenous nanochannels, leading to improved cycling stability. As the triâ€layer separator maintains its dimensional stability even at 200 °C when the internal PE layer is melted and blocks the ion transport through the separator, the separator also provides an effective thermal shutdown function. The present nanocelluloseâ€based triâ€layer separator design thus significantly facilitates the realization of highâ€energy density Li metalâ€based batteries.
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| 3. |
- Pan, Ruijun, et al.
(författare)
-
Polydopamine-based redox-active separator for lithium-ion batteries
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Tidskriftsartikel (refereegranskat)abstract
- The performance of lithium-ion batteries (LIBs) can be effectively increased with functionalized separators. Herein, it is demonstrated that polydopamine-based redox-active (PRA) separators can provide additional capacity to that of typical anode materials, increase the volumetric capacity of the cell, as well as, decrease the cell resistance to yield an improved performance at higher cycling rates. The PRA separators, which are composed of a 2 µm thick electrically insulating nanocellulose fiber (NCF) layer and an 18 µm thick polydopamine (PDA) and carbon nanotube (CNT) containing redox-active layer, are readily produced using a facile paper-making process. The PRA separators are also easily wettable by commonly employed electrolytes (e.g. LP40) and exhibit a high dimensional stability even at elevated temperatures (e.g. 150 ºC). In addition, the pore structure endows the PRA separator with a high ionic conductivity (i.e. 1.06 mS cm-1 after soaking with LP40 electrolyte) that increases the rate performance of the cells. Due to the presence of the redox-active layer, Li4Ti5O12 (LTO) half-cells containing PRA separator were found to exhibit significantly higher capacities than the corresponding cells containing commercial separators. These results clearly show that the implementation of this type of redox-active separators constitutes a straightforward and effective way to increase the energy and power densities of LIBs.
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| 4. |
- Pan, Ruijun, et al.
(författare)
-
Polydopamine-based redox-active separators for lithium-ion batteries
- 2019
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Ingår i: Journal of Materiomics. - : Elsevier. - 2352-8478 .- 2352-8486. ; , s. 204-213
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Tidskriftsartikel (refereegranskat)abstract
- The performance of lithium-ion batteries (LIBs) can be effectively increased with functionalized separators. Herein, it is demonstrated that polydopamine-based redox-active (PRA) separators can provide additional capacity to that of typical anode materials, increase the volumetric capacity of the cell, as well as, decrease the cell resistance to yield an improved performance at higher cycling rates. The PRA separators, which are composed of a 2 μm thick electrically insulating nanocellulose fiber (NCF) layer and an 18 μm thick polydopamine (PDA) and carbon nanotube (CNT) containing redox-active layer, are readily produced using a facile paper-making process. The PRA separators are also easily wettable by commonly employed electrolytes (e.g. LP40) and exhibit a high dimensional stability. In addition, the pore structure endows the PRA separator with a high ionic conductivity (i.e. 1.06 mS cm−1) that increases the rate performance of the cells. Due to the presence of the redox-active layer, Li4Ti5O12 (LTO) half-cells containing PRA separator were found to exhibit significantly higher capacities than the corresponding cells containing commercial separators. These results clearly show that the implementation of this type of redox-active separators constitutes a straightforward and effective way to increase the energy and power densities of LIBs.
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| 5. |
- Pan, Ruijun, et al.
(författare)
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Sandwich-structured nano/micro fiber-based separators for lithium metal batteries
- 2019
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Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 55, s. 316-326
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Tidskriftsartikel (refereegranskat)abstract
- Although the increased need for high-energy/power-density energy storage systems has revived the research on lithium metal batteries (LMBs), the influence of the separator on the performance of LMBs is still generally neglected. In the present study, a sandwich-structured separator (referred to as the CGC separator below) composed of two 2.5µm thick cellulose nanofiber (CNF) surface layers and an intermediate 15µm thick glass microfiber (GMF) and CNF composite layer is described. While the CNF surface layers of the CGC separator feature a homogeneous distribution of nano-sized pores favoring the attainment of a homogeneous current distribution at both electrodes, the intermediate GMF/CNF layer contains macropores facilitating the ionic transport through the separator. The CGC separator exhibited a much better electrolyte wettability and thermal stability compared to a Celgard separator, due to the use of the hydrophilic and thermally stable CNFs and GMFs. It is also shown that the combination of nano-sized and micro-sized fibers used in the CGC separator yields a higher ionic conductivity than that for the commercial separator (1.14 vs. 0.49 mS cm−1). Moreover, the influence of the separator pore structure (e.g. the porosity and pore distribution) on the performance of LMBs is studied for both Li anodes and LiFePO4 composite cathodes. The results demonstrate that the use of separators with high porosities and homogeneous surface pore distributions can improve the performances (e.g. capacities and stabilities) of LMBs considerably, and also highlights the importance of proper separator/electrode interactions. The present approach constitutes a practical engineering strategy for the production of separators with nano/micro fibers and a promising route for the development of LMBs with improved safety and enhanced electrochemical performances.
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