660 Technische Chemie
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The significant demand for energy storage systems has spurred innovative designs and extensive research on lithium-ion batteries (LIBs). To that end, an in-depth examination of utilized materials and relevant methods in conjunction with comparing electrochemical mechanisms is required. Lithium titanate (LTO) anode materials have received substantial interest in high-performance LIBs for numerous applications. Nevertheless, LTO is limited due to capacity fading at high rates, especially in the extended potential range of 0.01–3.00 V versus Li+/Li, while delivering the theoretical capacity of 293 mAh g−1. This study demonstrates how the performance of the LTO anode can be improved by modifying the manufacturing process. Altering the dry and wet mixing duration and speeds throughout the manufacturing process leads to differences in particle sizes and homogeneity of dispersion and structure. The optimized anode at 5 A g−1 (≈17C) and 10 A g−1 (≈34C) yielded 188 and 153 mAh g−1 and retained 73% and 68% of their initial capacity after 1000 cycles, respectively. The following findings offer valuable information regarding the empirical modifications required during electrode fabrication. Additionally, it sheds light on the potential to produce efficient anodes using commercial LTO powder.
Supercapacitors are efficient and versatile energy storage devices, offering remarkable power density, fast charge/discharge rates, and exceptional cycle life. As research continues to push the boundaries of their performance, electrode fabrication techniques are critical aspects influencing the overall capabilities of supercapacitors. Herein, we aim to shed light on the advantages offered by dry electrode processing for advanced supercapacitors. Notably, our study explores the performance of these electrodes in three different types of electrolytes: organic, ionic liquids, and quasi-solid states. By examining the impact of dry electrode processing on various electrode and electrolyte systems, we show valuable insights into the versatility and efficacy of this technique. The supercapacitors employing dry electrodes demonstrated significant improvements compared with conventional wet electrodes, with a lifespan extension of +45% in organic, +192% in ionic liquids, and +84% in quasi-solid electrolytes. Moreover, the increased electrode densities achievable through the dry approach directly translate to improved volumetric outputs, enhancing energy storage capacities within compact form factors. Notably, dry electrode-prepared supercapacitors outperformed their wet electrode counterparts, exhibiting a higher energy density of 6.1 Wh cm−3 compared with 4.7 Wh cm−3 at a high power density of 195 W cm−3, marking a substantial 28% energy improvement in the quasi-solid electrolyte.
Selenium disulfide (often referred to as SeS2) encompasses a family of mixed selenium-sulfide eight-membered rings, traditionally used as an anti-dandruff agent in shampoos. SeS2 can be produced by reacting hydrogen sulfide (H2S) with selenite (SeO32−) under acidic conditions. This chemistry is also possible with natural spring waters that are rich in H2S, thus providing an avenue for the more sustainable, green production of high-quality SeS2 particles from an abundant natural source. The orange material obtained this way consists of small globules with a diameter in the range of 1.1 to 1.2 µm composed of various SexS8−x chalcogen rings. It shows the usual composition and characteristics of a Se-S interchalcogen compound in EDX and Raman spectroscopy. Since the mineral water from Bad Nenndorf is also rich in salts, the leftover brine has been evaporated to yield a selenium-enriched salt mixture similar to table salt. As the water from Bad Nenndorf—in comparison to other bodies of water around the world—is still rather modest in terms of its H2S content, especially when compared with volcanic waters, this approach may be refined further to become economically and ecologically viable, especially as a regional business model for small and medium-sized enterprises.
Soft-adaptive electronics require both sensor and conductor materials. The key parameter for these materials is their mechanoelectrical properties. Liquid metals and solid conductive composites have been exploited in this application field, but both are limited by either their chemical stability or limited flexibility, respectively. Electrofluids are a novel approach towards soft electronic components. They are concentrated colloidal suspensions of conductive particles, in which dynamic contacts retain electrical conductivity under deformation, filling the gap between liquid metals and solid composites. Here, we study the mechanical and electrical network interplay of electrofluids based on multi-walled carbon nanotubes (MWCNTs) in glycerol. These networks arise at different filler concentrations, showing a different response to external deformations. We found that electrical conductivity occurs without the presence of a rigid mechanical network, which allows MWCNT suspensions to be electrically conductive even under flow conditions. By performing rheoelectrical measurements, we observed how the mechanical and electrical networks evolved with the applied deformation. We demonstrated the applicability of electrofluids with tailored mechanoelectrical properties as soft electrical connectors.
Soft electrical components are highly demanded in human-machine interaction devices. ”Electrofluids” (EFs) as suspensions of electrically conductive filler particles in non-conductive solvents have been proposed as promising sensors and conductive materials since they can flow and retain electrical conductivity. As they remain liquid in working conditions, encapsulation and manufacturing of complex patterns remain as a challenge but would enable a wider variety of applications. We propose direct ink writing (DIW) as method to manufacture carbon-based EFs. We performed simple shear flow and Fourier-transform (FT) rheology to evaluate the printability of EFs containing different concentrations of Carbon Black and Graphene Powder by DIW. Electrofluids exhibited three important characteristics to be manufactured via DIW: yield stress behaviour (confirmed by flow curves), high brittleness, and a fast mechanical recovery within a range of 15 seconds. We created printability maps to distinguish printable and non-printable EFs. We used printable EFs to manufacture complex patterns. As a proof of the great potential of the EFs and DIW combination, we compared simple and multiline strain gauges enhancing the sensitivity of EF as strain sensor by 400%.
Life After Death: Re-Purposing End-of-Life Supercapacitors for Electrochemical Water Desalination
(2024)
This study explores the potential of re-purposing end-of-life commercial supercapacitors as electrochemical desalination cells, aligning with circular economy principles. A commercial 500-Farad supercapacitor was disassembled, and its carbon electrodes underwent various degrees of modification. The most straightforward modification involved NaOH-etching of the aluminum current collector to produce free-standing carbon films. More advanced modifications included CO2 activation and binder-added wet processing of the electrodes. When evaluated as electrodes for electrochemical desalination via capacitive deionization of low-salinity (20 mM) NaCl solutions, the minimally modified NaOH-etched carbon electrodes achieved an average desalination capacity of 5.8 mg g−1 and a charge efficiency of 80 %. In contrast, the CO2-activated, wet-processed electrodes demonstrated an improved desalination capacity of 7.9 mg g−1 and a charge efficiency above 90 % with stable performance over 20 cycles. These findings highlight the feasibility and effectiveness of recycling supercapacitors for sustainable water desalination applications, offering a promising avenue for resource recovery and re-purposing in pursuing environmental sustainability.
Electrochemical water desalination is an emerging technology known for its high efficiency and low energy consumption in removing ions from aqueous media. The present thesis begins by explaining the fundamentals of a typical electrochemical water desalination system and presenting relevant performance metrics. The significance and limitations of the latter metrics are then discussed based on the generations of the electrodes developed during the past few decades. This report seeks to expand the scope by investigating MXene (titanium carbide) as a purely pseudocapacitive material characterized by a capacitor-like electric response achieved through ion intercalation. Afterward, the merit of MXene when utilized as an electrode in electrochemical desalination is investigated for both single-salt and multi-salt aqueous solutions, ultimately establishing qualitative insights into the relationship between MXene properties and its electrochemical desalination behavior. Finally, the thesis goes beyond MXene and explores its sibling materials, such as MBene (transition metal boride), for lithium-ion battery electrodes. As another application of 2D nanolamellar materials at the water-energy nexus, we have explored MXene conversion into transition metal dichalcogenides by sulfidation heat treatment and its merit as electrodes for hydrogen electrocatalysis. These findings can contribute to developing more efficient and sustainable energy storage, conversion, and desalination technologies.
Chemical and Structural Comparison of Different Commercial Food Supplements for Silicon Uptake
(2023)
Various food supplements for silicon uptake were compared in terms of their structures and chemical compositions. In particular, we analyzed the silanol group content, which can be an indicator of the uptake of the siliceous species in the human body. We analyzed the commercial products Original Silicea Balsam®, Flügge Siliceous Earth Powder, Pure Colloidal Silicon, and BioSil® by applying various methods such as FTIR, 29Si NMR, and TGA. The Si-OH group content of the samples containing pure silica was the highest for the Original Silicea Balsam followed by the Pure Colloidal Silicon. The siliceous earth powder revealed the lowest content of such groups and the densest structure. BioSil® contained a considerable concentration of organic molecules that stabilized orthosilicic acid. The study may help to understand the silicon uptake behavior of different food supplements depending on their chemical structure.
Ionic liquid mixtures show promise as electrolytes for supercapacitors with nanoporous electrodes. Herein, we investigate theoretically and with experiments how binary electrolytes comprising a common anion and two types of differently-sized cations affect capacitive energy storage. We find that such electrolytes can enhance the capacitance of single nanopores and nanoporous electrodes under potential differences negative relative to the potential of zero charge. For a two-electrode cell, however, they are beneficial only at low and intermediate cell voltages, while a neat ionic liquid performs better at higher voltages. We reveal subtle effects of how the distribution of pores accessible to different types of ions correlates with charge storage and suggest approaches to increase capacitance and stored energy density with ionic liquid mixtures.
Printed electronic paper identifies its interest in flexible organic electronics and sustainable and clean energy applications because of its straightforward production method, cost-effectiveness, and positive environmental impact. However, current limitations include restricted material thickness and the use of supporting substrate for printing. Here, 2D and 3D electronic patterned paper are fabricated from direct ink writing (DIW) nanocellulose and PEDOT:PSS-based materials using syringe deposition and 3D printing. The conductor patterns are integrated in the bulk of the paper, while non-conductive sections are used as support to form free-standing paper. The strong interface between the patterns of electronic patterned paper gives mechanical stability for practical handling. The conductive paper-based electrode has 202 S cm−1 and is capable of handling electric current up to 0.7 A, which can be used for high-power devices. Printed supercapacitor papers show high specific energy of 4.05 Wh kg−1, specific power of 4615 W kg−1 at 0.06 A g−1, and capacitance retention above 95% after 2000 cycles. The new design structure of electronic patterned papers presents a solution for additive manufacturing of paper-based composites for supercapacitors, wearable electronics, or sensors for smart packaging.