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Pan, Ruijun
Publications (10 of 19) Show all publications
Chien, Y.-C., Pan, R., Lee, M.-T., Nyholm, L., Brandell, D. & Lacey, M. (2019). Cellulose Separators With Integrated Carbon Nanotube Interlayers for Lithium-Sulfur Batteries: An Investigation into the Complex Interplay between Cell Components. Journal of the Electrochemical Society, 166(14), A3235-A3241
Open this publication in new window or tab >>Cellulose Separators With Integrated Carbon Nanotube Interlayers for Lithium-Sulfur Batteries: An Investigation into the Complex Interplay between Cell Components
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2019 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 166, no 14, p. A3235-A3241Article in journal (Refereed) Published
Abstract [en]

This work aims to address two major roadblocks in the development of lithium-sulfur (Li-S) batteries: the inefficient deposition of Li on the metallic Li electrode and the parasitic "polysulfide redox shuttle". These roadblocks are here approached, respectively, by the combination of a cellulose separator with a cathode-facing conductive porous carbon interlayer, based on their previously reported individual benefits. Both approaches result in significant improvements in cycle life in test cells with positive electrodes with practically relevant specifications. Despite the substantially prolonged cycle life, the combination of the interlayer and cellulose separator generates an increase in polysulfide shuttle current, leading to greatly reduced Coulombic efficiency. Based on XPS analyses, the latter is ascribed to a change in the composition of the solid electrolyte interphase (SEI) on the Li electrode. At the same time, the rate of electrolyte decomposition is found to be lower in cells with cellulose-based separators, which corroborates the observation of longer cycle life. These seemingly contradictory and counterintuitive observations demonstrate the complicated interactions between the cell components in the Li-S system and how strategies aiming to mitigate one unwanted process may exacerbate another. This study demonstrates the value of a holistic approach to the development of Li-S chemistry.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-395795 (URN)10.1149/2.0301914jes (DOI)000487673900002 ()
Funder
Swedish Energy Agency, 42762-1Swedish Energy Agency, 42031-1
Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-25Bibliographically approved
Pan, R. (2019). Cladophora Cellulose-based Separators for Lithium Batteries. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Cladophora Cellulose-based Separators for Lithium Batteries
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The development of lithium-ion batteries (LIBs) has been focused on exploring and improving the electrode materials and electrolytes in the past decades. An indispensable component, the separator, is however not studied as extensively. In general, a separator has two functions, i.e. preventing the direct contact between the cathode and anode and providing the ionic transport pathways. Commercial separators for LIBs are usually made of polyolefin materials, which often have low thermal stabilities and poor electrolyte wettabilities.

In this thesis, a new type of material, i.e. Cladophora cellulose, is used to manufacture separators for LIBs and lithium-metal batteries (LMBs). The separators, made with Cladophora cellulose fibers via a straightforward paper making method, possess several advantages compared to conventional polyolefin separators regarding, e.g. ionic conductivity, thermal stability, electrolyte wettability and pore distribution, providing promising alternatives for battery separators.

Apart from studying the two basic functions mentioned above, two types of advanced separator functionalities have been studied, i.e. redox-activity and the attainment of a homogeneous current distribution, in conjunction with proposals for new separator designs.

Two types of redox-active separators have been devised for the first time in the separator field, based on the use of a redox-active conducting polymer, polypyrrole (PPy) and a natural polymer, polydopamine (PDA). Based on their redox-active potentials, the PPy-based redox-active separator was designed to contribute capacity to the cathode of a LIB, while the PDA-based redox-active separator was proposed to be used on the anode side.

It is known that a homogeneous current distribution is beneficial for the battery performance. Therefore, two new types of separators with homogenous pore distributions have been manufactured to study the influence of the pore distribution on the Li deposition/stripping behavior and composite cathode utilization in LMBs. With the knowledge obtained from the study, a stable, long lifetime paper-based LMB was designed.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 61
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1754
Keywords
Cellulose, Separator, Paper making, Lithium-ion battery, Lithium-metal battery, Functionalization.
National Category
Materials Chemistry
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-368963 (URN)978-91-513-0529-5 (ISBN)
Public defence
2019-02-08, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2019-01-16 Created: 2018-12-10 Last updated: 2019-01-21
Pan, R., Sun, R., Wang, Z., Lindh, J., Edström, K., Strömme, M. & Nyholm, L. (2019). Double-sided conductive separators for lithium-metal batteries. Energy Storage Materials, 21, 464-473
Open this publication in new window or tab >>Double-sided conductive separators for lithium-metal batteries
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2019 (English)In: Energy Storage Materials, ISSN 2405-8297, Vol. 21, p. 464-473Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials; Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-389860 (URN)10.1016/j.ensm.2019.06.025 (DOI)000484341600043 ()
Funder
Swedish Energy Agency
Available from: 2019-07-30 Created: 2019-07-30 Last updated: 2019-10-21Bibliographically approved
Wang, Z., Tammela, P., Pan, R., Strömme, M. & Nyholm, L. (2019). Flexible Nanocellulose based Energy Storage Devices. In: MRS (Ed.), MRS Spring Meeting 2019: . Paper presented at MRS Spring Meeting 2019. Phoenix 22-26/4 2019. Phoenix, Article ID ES03.06.01ES03.06.01.
Open this publication in new window or tab >>Flexible Nanocellulose based Energy Storage Devices
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2019 (English)In: MRS Spring Meeting 2019 / [ed] MRS, Phoenix, 2019, article id ES03.06.01ES03.06.01Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

The strong need for the development of inexpensive, flexible, light-weight and environmentally friendly energy storage devices has resulted in large interest in new cellulose-based electrode materials that can be used in batteries and supercapacitors [1-3]. In this presentation it will be shown that flexible nanocellulose and polypyrrole composites, manufactured by chemical polymerization of e.g. pyrrole on a nanocellulose substrate, can be used as electrodes in charge storage devices containing either water or organic solvent based electrolytes. The aqueous flexible paper-based devices exhibit high charge storage capacities (e.g. 9 Wh/kg) as well as excellent power capabilities (e.g. 3.5 kW/kg) due to the large surface area (up to 250 m2/g) of the nanocellulose and the thin (i.e. 50 nm) layer of polypyrrole present on the nanocellulose fibers. The straightforward (papermaking) composite synthesis approach and the electrochemical properties of the resulting composites will be discussed. It will also be shown that high active mass paper electrodes [4-8] with mass loadings of up to 20 mg/cm2 can be employed at high current densities without significant loss of electrochemical performance as a result of the advantageous structure of the electrodes. Devices with unprecedented areal and volumetric cell capacitances (e.g. 5.7 F/cm2 and 240 F/cm3) that can cycle for thousands of cycles in aqueous electrolytes can likewise be realized. As the cellulose composites also can be used in lithium-ion batteries [9,10], functional (e.g. redox-active) separators [11] for lithium based batteries and in the realization of all-cellulose energy storage devices [12], the present materials provide new exciting possibilities for the development of green and foldable devices for a range of new applications, many of which are incompatible with conventional batteries and supercapacitors.

Place, publisher, year, edition, pages
Phoenix: , 2019
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-389521 (URN)
Conference
MRS Spring Meeting 2019. Phoenix 22-26/4 2019
Available from: 2019-07-16 Created: 2019-07-16 Last updated: 2019-07-16
Zhao, J., Pan, R., Sun, R., Wen, C., Zhang, S.-L., Wu, B., . . . Zhang, Z.-B. (2019). High-Conductivity Reduced-Graphene-Oxide/Copper Aerogel for Energy Storage. Nano Energy, 60, 760-767
Open this publication in new window or tab >>High-Conductivity Reduced-Graphene-Oxide/Copper Aerogel for Energy Storage
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2019 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 60, p. 760-767Article in journal (Refereed) Published
Abstract [en]

This work reports a room-temperature, solution-phase and one-pot method for macro-assembly of a three-dimensional (3D) reduced-graphene-oxide/copper hybrid hydrogel. The hydrogel is subsequently transformed into a highly conductive aerogel via freeze-drying. The aerogel, featuring reduced graphene oxide (rGO) networks decorated with Cu and CuxO nanoparticles (Cu/CuxO@rGO), exhibits a specific surface area of 48 m(2)/g and an apparent electrical conductivity of similar to 33 and similar to 430 S/m prior to and after mechanical compression, respectively. The compressed Cu/CuxO@rGO aerogel delivers a specific capacity of similar to 453 mAh g(-1) at a current density of 1 A/g and similar to 184 mAh g(-1) at 50 A/g in a 3 M KOH aqueous electrolyte evidenced by electrochemical measurements. Galvanostatic cycling tests at 5 A/g demonstrates that the Cu/CuxO@rGO aerogel retains 38% (similar to 129 mAh g(-1)) of the initial capacity (similar to 339 mAh g(-1)) after 500 cycles. The straightforward manufacturing process and the promising electrochemical performances make the Cu/CuxO@rGO aerogel an attractive electrode candidate in energy storage applications.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-381347 (URN)10.1016/j.nanoen.2019.04.023 (DOI)000467774100084 ()
Funder
Swedish Foundation for Strategic Research , Dnr SE13-0061Swedish Research Council, 621-2014-5596
Available from: 2019-04-08 Created: 2019-04-08 Last updated: 2019-06-11Bibliographically approved
Lindgren, F., Rehnlund, D., Pan, R., Pettersson, J., Younesi, R., Xu, C., . . . Nyholm, L. (2019). On the Capacity Losses Seen for Optimized Nano-Si Composite Electrodes in Li-Metal Half-Cells. Advanced Energy Materials, 9(33), Article ID 1901608.
Open this publication in new window or tab >>On the Capacity Losses Seen for Optimized Nano-Si Composite Electrodes in Li-Metal Half-Cells
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2019 (English)In: Advanced Energy Materials, ISSN 1614-6832, Vol. 9, no 33, article id 1901608Article in journal (Refereed) Published
Abstract [en]

While the use of silicon‐based electrodes can increase the capacity of Li‐ion batteries considerably, their application is associated with significant capacity losses. In this work, the influences of solid electrolyte interphase (SEI) formation, volume expansion, and lithium trapping are evaluated for two different electrochemical cycling schemes using lithium‐metal half‐cells containing silicon nanoparticle–based composite electrodes. Lithium trapping, caused by incomplete delithiation, is demonstrated to be the main reason for the capacity loss while SEI formation and dissolution affect the accumulated capacity loss due to a decreased coulombic efficiency. The capacity losses can be explained by the increasing lithium concentration in the electrode causing a decreasing lithiation potential and the lithiation cut‐off limit being reached faster. A lithium‐to‐silicon atomic ratio of 3.28 is found for a silicon electrode after 650 cycles using 1200 mAhg−1 capacity limited cycling. The results further show that the lithiation step is the capacity‐limiting step and that the capacity losses can be minimized by increasing the efficiency of the delithiation step via the inclusion of constant voltage delithiation steps. Lithium trapping due to incomplete delithiation consequently constitutes a very important capacity loss phenomenon for silicon composite electrodes.

Keywords
asymmetric cycling, hard X-ray photoelectron spectroscopy, lithium trapping, silicon, solid electrolyte interphase layer
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-398839 (URN)10.1002/aenm.201901608 (DOI)000477265600001 ()
Funder
Swedish Research Council, VR-2015-04421Swedish Research Council, VR-2017-06320StandUp
Note

De 2 första författarna delar förstaförfattarskapet.

Available from: 2019-12-11 Created: 2019-12-11 Last updated: 2019-12-11Bibliographically approved
Pan, R., Wang, Z., Sun, R., Lindh, J., Edström, K., Strömme, M. & Nyholm, L. (2019). Polydopamine-based redox-active separators for lithium-ion batteries. Journal of Materiomics, 204-213
Open this publication in new window or tab >>Polydopamine-based redox-active separators for lithium-ion batteries
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2019 (English)In: Journal of Materiomics, ISSN 2352-8478, p. 204-213Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Lithium-ion battery, Separator, Cellulose, Polydopamine, Redox-active
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-370069 (URN)10.1016/j.jmat.2018.12.007 (DOI)000470660000008 ()
Funder
Swedish Energy Agency, 2017-013543
Available from: 2018-12-18 Created: 2018-12-18 Last updated: 2019-06-26Bibliographically approved
Pan, R., Sun, R., Wang, Z., Lindh, J., Edström, K., Strömme, M. & Nyholm, L. (2019). Sandwich-structured nano/micro fiber-based separators for lithium metal batteries. Nano Energy, 55, 316-326
Open this publication in new window or tab >>Sandwich-structured nano/micro fiber-based separators for lithium metal batteries
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2019 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 55, p. 316-326Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Cellulose, separator, sandwich structure, lithium metal battery, current distribution, three-electrode
National Category
Nano Technology Materials Chemistry
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-364826 (URN)10.1016/j.nanoen.2018.11.005 (DOI)000454636200029 ()
Funder
StandUpSwedish Energy Agency
Available from: 2018-11-04 Created: 2018-11-04 Last updated: 2019-06-12Bibliographically approved
Edström, K., Pan, R., Wang, Z., Nyholm, L. & Strömme, M. (2019). Separators As a Tool for Enhanced Battery Performance. In: The electrochemical Society (Ed.), International Battery Association 2019: Batteries and Energy Storage. Paper presented at International Battery Association 2019 (IBA meeting, La Jolla, California, 3-8 March 2019). La Jolla, Article ID 117872.
Open this publication in new window or tab >>Separators As a Tool for Enhanced Battery Performance
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2019 (English)In: International Battery Association 2019: Batteries and Energy Storage / [ed] The electrochemical Society, La Jolla, 2019, article id 117872Conference paper, Oral presentation with published abstract (Refereed)
Place, publisher, year, edition, pages
La Jolla: , 2019
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-389519 (URN)
Conference
International Battery Association 2019 (IBA meeting, La Jolla, California, 3-8 March 2019)
Available from: 2019-07-16 Created: 2019-07-16 Last updated: 2019-07-16
Wang, Z., Pan, R., Xu, C., Ruan, C., Edström, K., Strømme, M. & Nyholm, L. (2018). Conducting polymer paper-derived separators for lithium metal batteries. Energy Storage Materials, 13, 283-292
Open this publication in new window or tab >>Conducting polymer paper-derived separators for lithium metal batteries
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2018 (English)In: Energy Storage Materials, ISSN 2405-8297, Vol. 13, p. 283-292Article in journal (Refereed) Published
Abstract [en]

Overoxidised polypyrrole (PPy) paper has been employed as a mesoporous separator for lithium metal batteries (LMBs) based on its narrow pore size distribution, good thermal stability, high ionic conductivity (1.1 mS cm−1 with a LP40 electrolyte) and high electrolyte wettability. The overoxidised PPy paper was produced from a PPy/cellulose composite using a combined base and heat-treatment process, yielding a highly interrupted pyrrole molecular structure including N-containing polar groups maintaining the readily adaptable mesoporous structure of the pristine PPy paper. This well-defined pore structure gave rise to a homogeneous current distribution which significantly increased the performance of a LiFePO4|Li cell. With the overoxidised PPy separator, a symmetric Li|Li cell could be cycled reversibly for more than 600 h without any short-circuits in a LP40 electrolyte. This approach facilitates the manufacturing of well-defined separators for fundamental investigations of the influence of the separator structure on the performance of LMBs.

Keywords
Conducting polymers, nanocellulose, separator, porosity, lithium metal, batteries
National Category
Inorganic Chemistry Engineering and Technology
Research subject
Chemistry with specialization in Inorganic Chemistry; Chemistry with specialization in Materials Chemistry; Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-355543 (URN)10.1016/j.ensm.2018.02.006 (DOI)000436924800033 ()
Funder
Swedish Energy Agency, TriLiSwedish Foundation for Strategic Research , RMA-110012Carl Tryggers foundation StandUp
Available from: 2018-07-01 Created: 2018-07-01 Last updated: 2019-12-11Bibliographically approved
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