Search

Lignin-based carbon fibers (LCFs) from the renewable resource softwood kraft lignin were synthesized via oxidative thermostabilization of pure melt-spun lignin and carbonization at different temperatures from 1000°C to 1700°C. The resulting LCFs were characterized by tensile testing, scanning electron microscopy (SEM), X-ray diffraction (XRD) and confocal Raman spectroscopy. The microstructure is mainly amorphous carbon with some nanocrystalline domains. The strength and stiffness are inversely proportional to the carbonization temperature, while the LCFs carbonized at 1000°C exhibit a strength of 628 MPa and a stiffness of 37 GPa. Furthermore, the application potential of LCFs was evaluated as negative electrodes in a lithium-ion battery (LIB) by electrochemical cycling at different current rates in a half-cell setup. The capacity drops with the carbonization temperature and the LCFs carbonized at 1000°C have a capacity of 335 mAh g−1. All LCFs showed good cycling stability. Because of the mechanical integrity and conductivity of the LCFs, there is no need to apply current collectors, conductive additives or binders. The advantage is an increased gravimetric energy density compared to graphite, which is the most common negative electrode material. LCFs show a promising multifunctional behavior, including good mechanical integrity, conductivity and an ability to intercalate lithium for LIBs.

Flexible Li-ion batteries attract increasing interest for applications in bendable and wearable electronic devices. TEMPO-oxidized cellulose nanofibrils (TOCNF), a renewable material, is a promising candidate as binder for flexible Li-ion batteries with good mechanical properties. Paper batteries can be produced using a water-based paper making process, avoiding the use of toxic solvents. In this work, finely dispersed TOCNF was used and showed good binding properties at concentrations as low as 4 wt %. The TOCNF was characterized using atomic force microscopy and found to be well dispersed with fibrils of average widths of about 2.7 nm and lengths of approximately 0.1-1 μm. Traces of moisture, trapped in the hygroscopic cellulose, is a concern when the material is used in Li-ion batteries. The low amount of binder reduces possible moisture and also increases the capacity of the electrodes, based on total weight. Effects of moisture on electrochemical battery performance were studied on electrodes dried at 110 °C in a vacuum for varying periods. It was found that increased drying time slightly increased the specific capacities of the LiFePO4 electrodes, whereas the capacities of the graphite electrodes decreased. The Coulombic efficiencies of the electrodes were not much affected by the varying drying times. Drying the electrodes for 1 h was enough to achieve good electrochemical performance. Addition of vinylene carbonate to the electrolyte had a positive effect on cycling for both graphite and LiFePO4. A failure mechanism observed at high TOCNF concentrations is the formation of compact films in the electrodes.

Carbon fibers have the combined mechanical and electrochemical properties needed to make them particularly well suited for usage as electrodes in a structural lithium-ion battery, a material that s ...

The electrochemical properties of various iron oxide scales on steel exposed in saturated calcium hydroxide solutions were investigated. The iron oxide scales were manufactured by different heat treatments and grinding processes and characterized using X-ray diffraction and scanning electron microscope. The electrochemical properties of the scales were assessed by measuring the corrosion potential and using electrochemical impedance spectroscopy and potentiodynamic polarization curves. It was found that wustite and magnetite are less noble compared to hematite but are more effective as cathodic surfaces. The results show that the electrochemical properties of the mill scale can be an important contributing factor in the corrosion of steel in concrete.

The mechanical and electrochemical properties are coupled through a piezo-electrochemical effect in Li-intercalated carbon fibers. It is demonstrated that this piezo-electrochemical effect makes it possible to harvest electrical energy from mechanical work. Continuous polyacrylonitrile-based carbon fibers that can work both as electrodes for Li-ion batteries and structural reinforcement for composites materials are used in this study. Applying a tensile force to carbon fiber bundles used as Li-intercalating electrodes results in a response of the electrode potential of a few millivolts which allows, at low current densities, lithiation at higher electrode potential than delithiation. More electrical energy is thereby released from the cell at discharge than provided at charge, harvesting energy from the mechanical work of the applied force. The measured harvested specific electrical power is in the order of 1 muW/g for current densities in the order of 1 mA/g, but this has a potential of being increased significantly. QC 20150713

A MEMS-based amperometric nitric oxide (NO) gas sensor is reported in this paper. The sensor is designed to detect NO gas for the purpose of asthma monitoring. The unique property of this sensor li ...

The objective of this study was to modify highly insulative and lightweight biorenewable foam thermosets to be semi-conductive for primarily building material applications. The foams were formed an ...

We report a method to deposit a thin solid polymer electrolyte (SPE) coating around individual carbon fibres for the realization of novel battery designs. In this study an electrocoating method is used to coat methacrylate-based solid polymer electrolytes onto carbon fibres. By this approach a dense uniform, apparently pinhole-free, poly(methoxy polyethylene glycol (350) monomethacrylate) coating with an average coating thickness of 470. nm was deposited around carbon fibres. Li-triflate, used as supporting electrolyte remained in the coating after the electrocoating operation. The Li-ion content in the solid polymer coating was found to be sufficiently high for battery applications. A battery device was built employing the SPE coated carbon fibres as negative electrode demonstrating reversible specific capacity of 260. mA. h/g at low currents (C/10), suggesting that these coated carbon fibres can be employed in future structural composite batteries.

Flexible battery solutions is an emerging field due to a demand for bendable electronic devices. In this study, a route to make flexible positive electrodes for Li-ion batteries by utilizing nanofi ...

The technology of electrically assisted delamination has potential applications in many fields, such as easy-to-open consumer packaging and recycling of lightweight materials. A better understanding about the mechanisms leading to debonding is important for further development of the technique, and is a goal of this study. A functional epoxy-based adhesive, applied between two aluminum foils, has been investigated using electrochemical and surface analytical techniques. Delamination occurred at the anodic adhesive boundary, which became acidic during polarization. The reactions during polarization of the laminates consisted of two steps, with aluminum oxide/hydroxide formation as the first and the build-up of a sulfur rich organic film as the second. Several possible debonding processes are discussed.

This paper reports on a novel miniaturized MEMS-based amperometric nitric oxide sensor that is suitable for a point of care testing device for asthma. The novelty lies in the combination of a high surface area microporous structured electrode, nano-structured Nafion that is coated on the side walls of the micropores, and liquid electrolyte. This combination allows detection of very low concentration (parts-per-billion) gas, has a high sensitivity of 4 μA/ppm/cm2 and has both a response and a recovery time of 6 s. The sensor is integrated with a PCB potentiostat to form a complete measuring module. The limit of detection of this sensor was estimated to be 0.3 ppb.

The binder material plays an important role in the electrodes for Li-ion batteries, keeping good electrochemical stability and adhesion with the current collectors. The conventional binder for the commercial Li-ion batteries is poly vinylidene fluoride (PVDF). However, it requires dissolving in an organic solvent, typically N-methyl-2-pyrrolidione (NMP), which is toxic and expensive. Kraft lignin is a byproduct which is extracted from pulp and paper industries by the LignoBoost process [1]. Its utilization has gained considerable attention due to its reasonable cost, relatively high purity and being renewable. In this work, kraft lignin was used for the first time as a binder material in Li-ion batteries [2]. It is more environmental friendly and potentially less expensive compared to the PVDF binder. Electrodes, LiFePO4 positive and graphite negative electrodes bound by kraft lignin, were characterized using scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge cycles. Results show that the electrodes have good reversible capacities about 150 mAh g-1 for positive electrode and 300 mAh g-1 for negative electrode cycled at C/10, and fairly good rate capabilities. The negatives have a very high cycling stability with about 98% retention after 50 cycles cycled at C/4. It illustrates that lignin is a promising alternative sustainable binder material for green Li-ion batteries. Reference 1. Tomani, P., The lignoboost process. Cellulose Chemistry & Technology, 2010. 44(1): p. 53. 2. Lu, H., et al., Lignin as a Binder Material for Eco-Friendly Li-Ion Batteries. Materials, 2016. 9(3): p. 127. Figure 1

Li-ion batteries are today essential for portable electronic devices as a main power source. Flexible Li-ion batteries have attracted great attention and could be very useful in the emerging fields of flexible, wearable, implantable and bendable electronic devices. Nano-fibrillated cellulose (NFC), with a high aspect ratio (length/diameter) of the nanofibrils, has shown to be a promising binder material for flexible Li-ion batteries [i] [ii]. As a reinforcement component, it gives flexible electrodes good mechanical properties. In addition, the process of making the flexible electrodes is water-based, eliminating the toxicity problem of using conventional poly(vinylidene fluoride) (PVDF) as binder. However, capacity fading limits the stability of the flexible electrodes during repeated cycling. Side reactions on the graphite negative electrodes could be the reason for the capacity loss. Li4Ti5O12(LTO), with a high potential of 1.55 V versus Li metal, could be an alternative to graphite for flexible negative electrodes, reducing the reactivity with the electrolyte. In this work, the electrochemical performance, such as specific capacity and columbic efficiency (CE), and mechanical properties of flexible LTO anode electrodes using NFC as binder are investigated. Fig 1 shows the photograph of LTO electrode, illustrating the flexibility. Fig. 1 Photograph of flexible Li4Ti5O12 negative electrode. [i] S.Leijonmarck, et al. Flexible nano-paper-based positive electrodes for Li-ion batteries-Preparation process and properties, Nano Energy, 2013, 2, 794–800. [ii] S.Leijonmarck, et al. Single-paper flexible Li-ion battery cells through a paper-making process based on nano-fibrillated cellulose, Journal of Materials Chemistry A, 2013, 1, 4671-4677. Figure 1

There is a continuing and growing demand for new and improved battery technologies. Extensive research is dedicated to pushing the limits of Li-ion batteries in terms of safety, environmental aspects, cost, lifetime and performance. A lot of the focus lies on improving graphite and other types of carbon-based electrodes [1-2] and extensive research has been on going since the beginning of the 90’s. Another possible route is improving technologies on a system level by introducing multifunctional materials. One way to do this is with structural batteries, where a battery can replace a load-bearing component in an electric or a hybrid electric vehicle for instance, and still maintaining the battery function. This way the weight is reduced (as well as freeing up space) on a system level and the overall performance is increased. A trade off between mechanical and electrochemical properties is expected, however, to increase overall effectiveness the performance of the battery does not need to be on par with a state of the art Li-ion battery. This concept of utilizing multifunctional materials in battery applications for instance has previously been studied with various methods and results [3-5]. This work focuses on investigating the electrochemical properties of commercial PAN based carbon fibers as electrodes for a future structural application. The cycleability and lifetime of the battery are two important factors for this concept to be realized. The focus is on evaluating the coulombic efficiency of carbon fibers which previous studies [6-8] has shown to have a good capacity as well as mechanical properties. The capacity was determined to be around 80% of the theoretical capacity of commercial graphite electrodes when cycled at a C/10 rate (fully charged in ten hours). One of the most promising carbon fibers is IMS65, which is an intermediate modulus fiber with a high strength and stiffness. The combination of good mechanical and electrochemical properties makes this fiber (and other similar) a very promising candidate for a structural battery application, which is the background to the work currently being done. The goal of this work is thus to thoroughly examine the electrochemical properties, in particular the coulombic efficiency, of commercially available carbon fibers to find a good candidate for usage in a structural battery application in terms of lifetime, power and capacity. The methodology utilizes a half-cell setup where the carbon fibers are used as working electrode and lithium foil as counter electrode. A glass-microfiber filter is used as a separator and the liquid electrolyte is 1.0 M LiPf6in EC/DEC (1:1 by weight, Selectilyte LP40) with and without VC (Vinylene Carbonate) added as an electrolyte additive. The cell is placed in a heat box with a controlled temperature and cycled in a high precision charger setup to accurately determine the coulombic efficiency and capacity of the carbon fibers. In a final concept, a liquid electrolyte cannot be used if the battery is to have structural properties as well. Instead, utilizing a solid polymer electrolyte is proposed. The effect of the solid polymer electrolyte on the electrochemical performance will therefore also be presented. Other important parameters studied are the surface coating (normally a sizing of epoxy or polyurethane) and epoxy tabbing (for tensile testing) of the fibers and its effect on the electrochemical properties. [1] T. Iijima, K. Suzuki and Y. Matsuda, Synthetic metals, 73, 9-20 (1995) [2] J. S. Kim, W. Y. Yoon, K. Soo Yoo, G. S. Park, C. W. Lee, Y. Murakamia and D. Shindo, Journal of power sources, 104, 175-180 (2002) [3] J. F. Snyder, E. L. Wong, C. W. Hubbard, Journal of The Electrochemical Society, 156, A215-A224 (2009) [4] P. Liu, E. Sherman and A. Jacob, Journal of Power Sources, 189, 646-650 (2009) [5] S. M. Shalouf, J. Zhang and C. H. Wang, Plastics, Rubber and Composites, 43, 98-104 (2014) [6] M. h. Kjell, E. Jacques, D. Zenkert, M. Behm and G. Lindbergh, Journal of The Electrochemical Society, 158 (12), A1455-A1460 (2011) [7] E. Jacques, M. H. Kjell, D. Zenkert, G. Lindbergh and M. Behm, Carbon, 59, 246-254 (2013) [8] E. Jacques, M. Kjell, D. Zenkert and G. Lindbergh, Carbon, 68, 725-733 (2014)

Li-ion batteries are the most important power source in the application of portable electronics. Flexible Li-ion batteries attract increasing interest and could be very useful in bendable and wearable electronic devices. Nano-fibrillated cellulose (NFC), a renewable material, is a promising candidate as a binder for flexible Li-ion batteries, with good mechanical properties. They can be produced using a water-based paper making process, avoiding the use of toxic solvents. Recent work has shown capacity fading during repeated cycling of the paper based Li-ion batteries, and the traces of moisture in the NFC may be the cause for this degradation[i],[ii]. In the present work, the cycling stability of flexible positive electrodes (Fig. 1) for Li-ion batteries using NFC as a binder is investigated and discussed as function of electrode drying conditions, mainly the time and temperature. Preliminary results show that the cells with longer drying time of the NFC-based electrode obtains a better cycling performance at C/10, as well as a higher coulombic efficiency. [i] S.Leijonmarck, et al. Flexible nano-paper-based positive electrodes for Li-ion batteries-Preparation process and properties, Nano Energy, 2013, 2, 794–800. [ii] S.Leijonmarck, et al. Single-paper flexible Li-ion battery cells through a paper-making process based on nano-fibrillated cellulose, Journal of Materials Chemistry A, 2013, 1, 4671-4677.

Recently, a need for mechanically flexible and strong batteries has arisen to power technical solutions such as active RFID tags and bendable reading devices. In this work, a method for making flex ...

Within the framework of this thesis, three innovative electrochemical devices have been studied. A part of the work is devoted to an already existing device, laminates which are debonded by the application of a voltage. This type of material can potentially be used in a wide range of applications, including adhesive joints in vehicles to both reduce the total weight and to simplify the disassembly after end-of-life, enabling an inexpensive recycling process. Although already a functioning device, the development and tailoring of this process was slowed by a lack of knowledge concerning the actual electrochemical processes responsible for the debonding. The laminate studied consisted of an epoxy adhesive, mixed with an ionic liquid, bonding two aluminium foils. The results showed that the electrochemical reaction taking place at the releasing anode interface caused a very large increase in potential during galvanostatic polarization. Scanning electron microscopy images showed reaction products growing out from the electrode surface into the adhesive. These reaction products were believed to cause the debonding through swelling of the anodic interface so rupturing the adhesive bond.The other part of the work in this thesis was aimed at innovative lithium ion (Li‑ion) battery concepts. Commercial Li-ion batteries are two-dimensional thin film constructions utilized in most often mechanically rigid products. Two routes were followed in this thesis. In the first, the aim was flexible batteries that could be used in applications such as bendable reading devices. For this purpose, nano-fibrillated cellulose was used as binder material to make flexible battery components. This was achieved through a water-based filtration process, creating flexible and strong papers. These paper-based battery components showed good mechanical properties as well as good rate capabilities during cycling. The drawback using this method was relatively low coulombic efficiencies believed to originate from side-reactions caused by water remnants in the cellulose structure. The second Li-ion battery route comprised an electrochemical process to coat carbon fibers, shown to perform well as negative electrode in Li-ion batteries, from a monomer solution. The resulting polymer coatings were ~500 nm thick and contained lithium ions. This process could be controlled by mainly salt content in the monomer solution and polarization time, yielding thin and apparently pin-hole free coatings. By utilizing the carbon fiber/polymer composite as integrated electrode and electrolyte, a variety of battery designs could possibly be created, such as three-dimensional batteries and structural batteries.