One of the biggest challenges we will face over the next few decades is finding a way to power the future while maintaining strong socioeconomic growth and a clean environment. A transition from the ...use of fossil fuels to renewable energy sources is expected. Cellulose, the most abundant natural biopolymer on earth, is a unique, sustainable, functional material with exciting properties: it is low‐cost and has hierarchical fibrous structures, a high surface area, thermal stability, hydrophilicity, biocompatibility, and mechanical flexibility, which makes it ideal for use in sustainable, flexible energy storage devices. This review focuses on energy storage applications involving different forms of cellulose (i.e., cellulose microfibers, nanocellulose fibers, and cellulose nanocrystals) in supercapacitors, with particular emphasis on new trends and performance considerations relevant to these fields. Recent advances and approaches to obtaining high capacity devices are evaluated and the limitations of cellulose‐based systems are discussed. For the first time, a combination of device‐specific factors such as electrode structures, mass loadings, areal capacities, and volumetric properties are taken into account, so as to evaluate and compare the energy storage performance and to better assess the merits of cellulose‐based materials with respect to real applications.
The most exciting recent advances in the supercapacitor application of cellulose composites based on different types of cellulose are summarized. In particular, this work focuses on parameters of cellulose‐based electrodes which affect the overall capacity performance metrics of supercapacitors. Approaches toward the realisation of high active masses and high volumetric capacitances for cellulose based electrodes are discussed.
All‐polymer and paper‐based energy storage devices have significant inherent advantages in comparison with many currently employed batteries and supercapacitors regarding environmental friendliness, ...flexibility, cost and versatility. The research within this field is currently undergoing an exciting development as new polymers, composites and paper‐based devices are being developed. In this report, we review recent progress concerning the development of flexible energy storage devices based on electronically conducting polymers and cellulose containing composites with particular emphasis on paper‐based batteries and supercapacitors. We discuss recent progress in the development of the most commonly used electronically conducting polymers used in flexible device prototypes, the advantages and disadvantages of this type of energy storage devices, as well as the two main approaches used in the manufacturing of paper‐based charge storage devices.
Recent progress within the field of conducting polymer and cellulose‐based charge storage is reviewed with particular emphasis on the development of environmentally friendly, versatile and flexible paper‐based batteries and supercapacitors. The latter devices, which can be constructed from a few paper sheets, enable the realization of a range of new types of charge storage devices.
The transition from 3D to 2D lithium deposition can be achieved with low Li-ion concentrations by forming a multitude of lithium nuclei on the lithium surface prior to the deposition using a ...nucleation pulse followed by pulsed galvanostatic deposition. Under these conditions, homogeneous lithium metal deposition is favored by the diffusion-controlled mass transfer to the nuclei-enriched surface.
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Lithium metal electrodes are not widely used in rechargeable batteries as dendritic lithium growth and electrolyte reactions raise serious stability and safety concerns. In this study, we show that reproducible two-dimensional lithium deposition can be realized using a lithium salt concentration of 0.020 M, an added supporting salt, and a short lithium nucleation pulse. This approach, which is common in electrodeposition of metals, increases the lithium nuclei density on the electrode surface and decreases the extent of Li+ migration favoring dendritic lithium growth. Contrary to common belief, ascribing the dendrite problem to heterogeneous lithium nucleation due to an unstable solid electrolyte interphase layer, we show that the main lithium deposition problem stems from the difficulty to obtain two-dimensional deposition at the low lithium deposition overpotentials encountered in conventional high-lithium concentration electrolytes. The present results hence clearly demonstrate that two-dimensional lithium deposition can be realized in lithium-metal-based batteries.
Conducting polymers for battery applications have been subject to numerous investigations during the last two decades. However, the functional charging rates and the cycling stabilities have so far ...been found to be insufficient for practical applications. These shortcomings can, at least partially, be explained by the fact that thick layers of the conducting polymers have been used to obtain sufficient capacities of the batteries. In the present letter, we introduce a novel nanostructured high-surface area electrode material for energy storage applications composed of cellulose fibers of algal origin individually coated with a 50 nm thin layer of polypyrrole. Our results show the hitherto highest reported charge capacities and charging rates for an all polymer paper-based battery. The composite conductive paper material is shown to have a specific surface area of 80 m2 g−1 and batteries based on this material can be charged with currents as high as 600 mA cm−2 with only 6% loss in capacity over 100 subsequent charge and discharge cycles. The aqueous-based batteries, which are entirely based on cellulose and polypyrrole and exhibit charge capacities between 25 and 33 mAh g−1 or 38−50 mAh g−1 per weight of the active material, open up new possibilities for the production of environmentally friendly, cost efficient, up-scalable and lightweight energy storage systems.
Multicomponent carbide thin films of (CrNbTaTiW)C (30–40at.% C) with different metal contents were deposited at different temperatures using non-reactive DC magnetron sputtering. The lattice ...distortion for the metal lattice was estimated to vary from about 3 to 5%. Most films crystallized in the cubic B1 structure but Ta/W-rich films deposited at 600°C exhibited a tetragonal distortion. X-ray diffraction results show that near-equimolar films exhibited a strong (111) texture. In contrast, Ta/W-rich films exhibited a shift from (111) to (100) texture at 450°C. The in-plane relationship was determined to MC(111)-12-1//Al2O3(001)110 with a lattice mismatch of about 11% along the Al2O3110 direction. A segregation of Cr to the grain boundaries was observed in all films. The microstructure was found to be the most important factor for high hardness. Less dense Nb-rich and near-equimolar films deposited at low temperatures exhibited the lowest hardness (12GPa), while very dense Ta/W-rich high temperature films were found to be the hardest (36GPa). No correlation was found between the lattice distortion and the hardness. Corrosion studies revealed that the multicomponent films exhibited excellent corrosion resistance, superior to that of a reference hyper-duplex stainless steel, in 1.0M HCl.
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•A novel multicomponent carbide ((CrNbTaTiW)C) has been deposited by magnetron sputtering.•Extremely hard multicomponent carbides can be deposited by tuning of the composition and deposition temperature.•The hardest film exhibits a tetragonal distortion of the fcc-based lattice not previously observed for carbides.•(CrNbTaTiW)C films show excellent corrosion resistance superior to commercially available hyper-duplex stainless steels.
•(Al,Cr,Nb,Y,Zr)N films have been deposited by reactive magnetron sputtering.•All films consisted of a single NaCl-type solid solution.•Indications of partial elemental segregation on the nanoscale ...was observed.•Hardness and corrosion resistance were improved compared to a (Nb,Zr)N film.
Multi-component nitride thin films in the Al–Cr–Nb–Y–Zr system with non-equimolar composition have been deposited by reactive dc magnetron sputtering. The substrate temperature and substrate bias have been varied, from room temperature to 700 °C and from 0 to −200 V respectively. The relationship between these varied growth conditions on the structure, morphology, mechanical and corrosion properties of the films have been probed.
All films consisted of a single solid solution with a NaCl-type structure, as shown by X-ray diffraction. However, elemental energy dispersive spectroscopy maps, obtained in the scanning transmission electron microscope, indicated that there could be partial segregation of Al, Cr and Y atoms within the grains. The microstructure of the films became denser, more fine-grained and smoother as the bias and temperature were increased. Nanoindentation showed that the hardness of the films increased with both bias and temperature, reaching a maximum of 27 ± 2 GPa. The corrosion resistance of the films, studied by performing potentiodynamic polarisation curves in 1 M HCl, was also found to be improved when compared to a commercially available hyper-duplex stainless steel and a ternary reference (Nb,Zr)N thin film as well.
Composites of polypyrrole (PPy) and Cladophora nanocellulose, reinforced with 8 μm‐thick chopped carbon filaments, can be used as electrode materials to obtain paper‐based energy‐storage devices with ...unprecedented performance at high charge and discharge rates. Charge capacities of more than 200 C g−1 (PPy) are obtained for paper‐based electrodes at potential scan rates as high as 500 mV s−1, whereas cell capacitances of ∼60–70 F g−1 (PPy) are reached for symmetric supercapacitor cells with capacitances up to 3.0 F (i.e.,0.48 F cm−2) when charged to 0.6 V using current densities as high as 31 A g−1 based on the PPy weight (i.e., 99 mA cm−2). Energy and power densities of 1.75 Wh kg−1 and 2.7 kW kg−1, respectively, are obtained when normalized with respect to twice the PPy weight of the smaller electrode. No loss in cell capacitance is seen during charging/discharging at 7.7 A g−1 (PPy) over 1500 cycles. It is proposed that the nonelectroactive carbon filaments decrease the contact resistances and the resistance of the reduced PPy composite. The present straightforward approach represents significant progress in the development of low‐cost and environmentally friendly paper‐based energy‐storage devices for high‐power applications.
Adding carbon filaments to composite electrodes containing polypyrrole and nanocellulose significantly improves the performance of supercapacitors based on these electrodes. The electrode charge capacity and cell capacitance are maintained at high potential scan rates and charging currents when carbon filaments are included to decrease the cell resistance. The results represent significant progress in the development of inexpensive, paper‐based, environmentally friendly energy‐storage devices.
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•The peak hardness of the as-grown films was 12.4 GPa and increased 4 GPa after annealing.•The TaNiSiC remained amorphous after annealing up to 700 °C for a total of four hours.•A few ...atomic percent of Si significantly increased the corrosion resistance.•Separation of Ni and C decrease the resistance to crystallization and material properties.
Amorphous TaNiSiC and TaNiC films (with varying Ta/Ni and Si/C ratios) were deposited using combinatorial magnetron sputtering. The TaNiSiC films remained X-ray amorphous after four hour-long annealings up to 700 °C, while TaNiC alloys with high Ni and C contents crystallized. These differences were attributed to a strong driving force for separation of Ni and C in TaNiC, whereas the addition of Si, due to its solubility in the other elements, reduced the elemental segregation in TaNiSiC. The as-deposited TaNiSiC films exhibited hardnesses of 9–12 GPa. Annealing led to an increase in hardness by 2–4 GPa, due to decreases in average atomic distance, as evidenced by X-ray diffraction measurements. Potentiodynamic polarizations from –0.7 to +1.5 V vs. Ag/AgCl (3 M NaCl) in 10 mM sodium borate showed lower current densities by up to 2 orders of magnitude with increasing Ta content (28–52 at.%). Changes in Si/C content (7–13 at.% Si) had no effect. However, optical microscopy showed that TaNiSiC films with high Si/low C contents (13/10 at.%) suffered much less localized etching compared to TaNiC films. Thus, Si had a significant role in increasing the mechanical strength, corrosion resistance, and thermal stability of the TaNiSiC films.
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•Carbon addition improves corrosion resistance, hardness, and crack resistance.•Thermodynamic calculations were performed using the Calphad method.•The calculations predicted carbide ...formation, and Cr depletion from the alloy phase.•Carbide formation is suppressed to form a homogenous amorphous phase.
This study explores carbon addition as a materials design approach for simultaneously improving the hardness, crack resistance, and corrosion resistance of high entropy thin films. CoCrFeMnNi was selected as a starting point, due to its high concentration of weak carbide formers. The suppression of carbides is crucial to the approach, as carbide formation can decrease both ductility and corrosion resistance. Films with 0, 6, and 11 at.% C were deposited by magnetron co-sputtering, using a graphite target and a sintered compound target. The samples with 0 at.% C crystallized with a mixture of a cubic closed packed (ccp) phase and the intermetallic χ-phase. With 6 and 11 at.% C, the films were amorphous and homogenous down to the nm-scale. The hardness of the films increased from 8 GPa in the carbon-free film to 16 GPa in the film with 11 at.% C. Furthermore, the carbon significantly improved the crack resistance as shown in fragmentation tests, where the crack density was strongly reduced. The changes in mechanical properties were primarily attributed to the shift from crystalline to amorphous. Lastly, the carbon improved the corrosion resistance by a progressive lowering of the corrosion current and the passive current with increasing carbon concentration.
All-polymer paper-based electrodes with a thickness up to hundreds of micrometers ( e.g. 290 μm), large active mass loadings (>20 mg cm −2 ) and relatively high densities (1.23 g cm −3 ) can be ...straightforwardly obtained from pristine low-cost polypyrrole–cellulose composites by decreasing the porosity of the material via space engineering. By straightforward compression of the composites, compact capacitive storage devices with improved space utilization are obtained without significantly compromising the electrochemical performance of the devices. This indicates that the compression unlike other methods previously used to vary the porosity of these composites does not affect the distribution of the mesopores which mainly determines the electrochemical performance of the material. When used to manufacture green supercapacitors comprising entirely of environmentally friendly materials, the freestanding and binder-free porous yet dense electrodes yield an areal capacitance of 5.66 F cm −2 , a device volumetric energy density of 3.7 W h L −1 (based on the volume of the entire device) and the largest volumetric electrode capacitance of 236 F cm −3 so far reported for conducting polymer-based electrodes. The presented results for symmetric supercapacitors containing aqueous electrolytes represent significant progress in the development of inexpensive and environmentally friendly high-performance paper-based energy storage devices.
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