| 1. |
- Asp, Leif, 1966, et al.
(author)
-
A structural battery and its multifunctional performance
- 2021
-
In: Advanced Energy and Sustainability Research. - : Wiley. - 2699-9412. ; 2:3
-
Journal article (peer-reviewed)abstract
- Engineering materials that can store electrical energy in structural load paths can revolutionize lightweight design across transport modes. Stiff and strong batteries that use solid-state electrolytes and resilient electrodes and separators are generally lacking. Herein, a structural battery composite with unprecedented multifunctional performance is demonstrated, featuring an energy density of 24 Wh kg-1 and an elastic modulus of 25 GPa and tensile strength exceeding 300 MPa. The structural battery is made from multifunctional constituents, where reinforcing carbon fibers (CFs) act as electrode and current collector. A structural electrolyte is used for load transfer and ion transport and a glass fiber fabric separates the CF electrode from an aluminum foil-supported lithium–iron–phosphate positive electrode. Equipped with these materials, lighter electrical cars, aircraft, and consumer goods can be pursued.
|
|
| 2. |
- Fang, Yuan, et al.
(author)
-
Lithium insertion in hard carbon as observed by 7Li NMR and XRD. The local and mesoscopic order and their relevance for lithium storage and diffusion
- 2022
-
In: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 10:18, s. 10069-10082
-
Journal article (peer-reviewed)abstract
- We investigate hard carbon fibers in different states of charge by a combination of 7Li-NMR and 2D-XRD. In particular, we record the quadrupole-split 7Li-NMR spectra and 7Li longitudinal relaxation over a wide temperature range, and determine lithium self-diffusion both parallel and perpendicular to the fiber axis. Recording the temperature dependence permits us to interpret the presence of motional averaging of spin couplings for mobile Li. The joint analysis shows that at low Li content, Li occupies sites that lack ordered coordination and delocalized electrons and are collected in disordered spatial domains. Upon increasing the Li content, ordered sites collected in ordered domains become populated. Both disordered and ordered domains have a high inherent heterogeneity with a typical spatial extension of a few nanometers. The disordered domains exhibit a continuous topology that permits unhindered diffusion within it. At high Li content we also observe the presence of very small (∼nm) particles of metallic lithium. The joint analysis of XRD in combination with diffusion anisotropy, and anisotropy from the 7Li-NMR spectrum (with samples oriented differently with regard to the applied magnetic field), shows that the mesoscopic structure is made by ordered domains arranged in a cylindrically rolled-up manner with the mesoscopic axis parallel to the fiber axis.
|
|
| 3. |
- Guex, Leonard Gaston, et al.
(author)
-
Experimental review : chemical reduction of graphene oxide (GO) to reduced graphene oxide (rGO) by aqueous chemistry
- 2017
-
In: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 9:27, s. 9562-9571
-
Research review (peer-reviewed)abstract
- The electrical conductivity of reduced graphene oxide (rGO) obtained from graphene oxide (GO) using sodium borohydride (NaBH4) as a reducing agent has been investigated as a function of time (2 min to 24 h) and temperature (20 degrees C to 80 degrees C). Using a 300 mM aqueous NaBH4 solution at 80 degrees C, reduction of GO occurred to a large extent during the first 10 min, which yielded a conductivity increase of 5 orders of magnitude to 10 S m(-1). During the residual 1400 min of reaction, the reduction rate decreased significantly, eventually resulting in a rGO conductivity of 1500 S m(-1). High resolution XPS measurements showed that C/O increased from 2.2 for the GO to 6.9 for the rGO at the longest reaction times, due to the elimination of oxygen. The steep increase in conductivity recorded during the first 8-12 min of reaction was mainly due to the reduction of C-O (e.g., hydroxyl and epoxy) groups, suggesting the preferential attack of the reducing agent on C-O rather than C=O groups. In addition, the specular variation of the percentage content of C-O bond functionalities with the sum of Csp(2) and Csp(3) indicated that the reduction of epoxy or hydroxyl groups had a greater impact on the restoration of the conductive nature of the graphite structure in rGO. These findings were reflected in the dramatic change in the structural stability of the rGO nanofoams produced by freeze-drying. The reduction protocol in this study allowed to achieve the highest conductivity values reported so far for the aqueous reduction of graphene oxide mediated by sodium borohydride. The 4-probe sheet resistivity approach used to measure the electrical conductivity is also, for the first time, presented in detail for filtrate sheet assemblies' of stacked GO/rGO sheets.
|
|
| 4. |
- Harnden, Ross, et al.
(author)
-
Multifunctional Performance of Sodiated Carbon Fibers
- 2018
-
In: Journal of the Electrochemical Society. - : ELECTROCHEMICAL SOC INC. - 0013-4651 .- 1945-7111. ; 165:13, s. B616-B622
-
Journal article (peer-reviewed)abstract
- An investigation is conducted into the potential for sodiated PAN-based carbon fibers (CFs) to be used in multifunctional actuation, sensing, and energy harvesting. Axial CF expansion/contraction is measured during sodiation/desodiation using operando strain measurements. The reversible expansion/contraction is found to be 0.1% - which is lower than that of lithiated CFs. The axial sodiation expansion occurs in two well-defined stages, corresponding to the sloping and plateau regions of the galvanostatic cycling curve. The results indicate that the sloping region most likely corresponds to sodium insertion between graphitic sheets, while the plateau region corresponds to sodium insertion in micropores. A voltage-strain coupling is found for the CFs, with a maximum coupling factor of 0.15 +/- 0.01 V/unit strain, which could be used for strain sensing in multifunctional structures. This voltage-strain coupling is too small to be exploited for harvesting mechanical energy. The measured axial expansion is further used to estimate the capacity loss due to solid electrolyte interphase (SEI) formation, as well as capacity loss due to sodium trapped in the CF microstructure. The outcomes of this research suggest that sodiated CFs show some potential for use as actuators and sensors in future multifunctional structures, but that lithiated CFs show more promise.
|
|
| 5. |
- Peuvot, Kevin, 1992-
(author)
-
Lignin- and PAN-based carbon fibres as negative electrodes for alkali-ion batteries
- 2023
-
Doctoral thesis (other academic/artistic)abstract
- The development of sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) have accelerated since they can now reach similar gravimetric energy densities as lithium-ion batteries (LIBs) but with a lower environmental impact. Hard carbon is the most common negative electrode for SIBs and KIBs and can be made from renewable resources such as lignin. Lignin can be then manufactured into fibres which can then be used as free-standing electrodes to push even further the sustainability by reducing the amount of current collector and additives needed in the battery. The concept of structural batteries is defined as a system that can simultaneously carry mechanical load as well as store the electrical energy in form of a battery to decrease the total weight. Polyacrylonitrile-based (PAN-based) carbon fibres are some of the most adapted materials thanks to their outstanding mechanical properties as well as their ability to be used as negative electrode for LIBs. However, a structural model and insertion model for alkali-ion insertion in the PAN-based carbon fibres is still lacking and is necessary to be able to understand the dynamics and fundamentals. This thesis focuses on the use of lignin-based carbon fibres (LCFs) and PAN-based carbon fibres as negative electrodes. The potential of using LCFs as negative electrode for SIBs and KIBs is evaluated by using a combination of electrochemical techniques and material characterization methods. The LCFs have high specific capacity and high initial coulombic efficiency when used as negative electrode for SIBs. The diffusion of potassium-ions into the LCFs is investigated by implementing a numerical model. The investigation on the open circuit voltage curves and the entropy change for potassium-ion insertion suggests that the LCFs structure contains two domains which can explain why the numerical model cannot fully fit the experimental data. The PAN-based carbon fibres are investigated as negative electrode for LIBs and SIBs. For SIBs, the axial expansion is investigated during charge/discharge and shows a staged expansion between the slope region and the plateau region of the charge/discharge profile. For LIBs, a combination of ex-situ Li-NMR and ex-situ wide-angle X-ray scattering isused to determine the insertion mechanism and structure of the PAN-based carbon fibres. A structural model and insertion model for lithium-ions is suggested from our experimental results consisting of three different types of sites: disordered domain in the carbon structure, ordereddomain in the carbon structure, and pore filling.
|
|
| 6. |
- Peuvot, Kevin, et al.
(author)
-
Lignin based electrospun carbon fiber anode for sodium ion batteries
- 2019
-
In: Journal of the Electrochemical Society. - : Electrochemical Society Inc.. - 0013-4651 .- 1945-7111. ; 166:10, s. A1984-A1990
-
Journal article (peer-reviewed)abstract
- Sodium ion batteries (SIBs) are emerging as an alternative battery technology to lithium ion batteries because they have the potential of having a similar energy density and the advantage of sodium being more environmentally friendly than lithium. Hard carbon has been shown to be one of the best candidates as anode material for SIBs. However, several challenges need to be solved before commercializing SIBs such as finding cheaper and more efficient precursors to produce hard carbon and increasing the stability of hard carbon electrodes with the electrolyte. Herein, we report a new bio-based free standing electrode made from lignin based electrospun carbon fibers (LCFs) with a high specific capacity of 310 mAh.g−1 and a first coulombic efficiency of 89%. By using high precision coulometry on the LCFs at different carbonization temperatures, it was found that the cycling stability was dependent on the carbonization temperature. The results show that LCFs are a viable and renewable source to be used as anodes in future SIBs. © The Author(s) 2019.
|
|
| 7. |
- Peuvot, Kevin, et al.
(author)
-
Potassium-ion insertion in lignin-based carbon fibers
-
Other publication (other academic/artistic)abstract
- Hard carbon is one the most promising negative electrode materials for potassium-ion batteries (KIBs). However, the structure of hard carbon is complex, made of curved graphene like structures containing defects, heteroatoms, and open and closed pores, and a complete structure model is still lacking. As a result, the potassium-ion insertion mechanism into hard carbon is still under debate. In this work, we analyze the electrochemical behavior of lignin-based carbon fibres (LCFs) electrodes manufactured at different carbonization temperatures. By analyzing the open-circuit voltage curves and entropy change of the insertion reaction, it is found that hard carbon electrodes behave like a blended electrode system in which the capacity contribution of the slope and the plateau regions of the galvanostatic profile can be considered as two separate domains, with different properties. To analyze the voltage relaxation curves, we compare results from both an analytical galvanostatic intermittent titration (GITT) model and an extended finite-element based potassium insertion model in the fibers. In some regions, the model exhibits poor fitting to our experimental results, which indicate shortcomings of using an analytical GITT model for analyzing potassium ion insertion into hard carbon. We propose that, to better predict the voltage relaxation behavior of the system, blended electrode characteristics with at least two domains should be incorporated in future modeling work
|
|
| 8. |
- Wu, Qiong, et al.
(author)
-
Conductive biofoams of wheat gluten containing carbon nanotubes, carbon black or reduced graphene oxide
- 2017
-
In: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 7:30, s. 18260-18269
-
Journal article (peer-reviewed)abstract
- Conductive biofoams made from glycerol-plasticized wheat gluten (WGG) are presented as a potential substitute in electrical applications for conductive polymer foams from crude oil. The soft plasticised foams were prepared by conventional freeze-drying of wheat gluten suspensions with carbon nanotubes (CNTs), carbon black (CB) or reduced graphene oxide (rGO) as the conductive filler phase. The change in conductivity upon compression was documented and the results show not only that the CNT-filled foams show a conductivity two orders of magnitude higher than foams filled with the CB particles, but also that there is a significantly lower percolation threshold with percolation occurring already at 0.18 vol%. The rGO-filled foams gave a conductivity inferior to that obtained with the CNTs or CB particles, which is explained as being related to the sheet-like morphology of the rGO flakes. An increasing amount of conductive filler resulted in smaller pore sizes for both CNTs and CB particles due to their interference with the ice crystal formation before the lyophilization process. The conductive WGG foams with CNTs were fully elastic with up to 10% compressive strain, but with increasing compression up to 50% strain the recovery gradually decreased. The data show that the conductivity strongly depends on the type as well as the concentration of the conductive filler, and the conductivity data with different compressions applied to these biofoams are presented for the first time.
|
|
