Mid Sweden University

Time-varying electric fields induce displacement currents through capacitive coupling, resulting in current continuity even in the absence of conduction paths. While capacitive coupling is known as a parasitic effect, its role in directly activating solid-state devices in open circuits remains underexplored. Here, we demonstrate that externally generated, time-varying electric fields—produced by triboelectric excitation or moving charged objects—can directly activate linear and nonlinear components, such as diodes, rectifiers, and LEDs, without a galvanic connection. A lumped-element capacitive-coupling model captures the observed dependencies Vab∝ω and Vab∝1/r, validated experimentally on both linear and non-linear components. The resulting field-driven activation enables energy harvesting in open circuits, multi-channel control, and wireless sensing of human motion and mechanical vibrations over meter-scale distances. This quasi-static capacitive coupling operates in a distinct regime compared to resonant wireless power transfer, because it is drive by low-frequency, motion induced electric field changes that generate transient displacement currents in floating circuits. The findings here enable contact-free activation of electronic components through discrete energy transfer rather than traditional continuous power delivery.

Silicon materials are currently being explored for usage in lithium–ion battery anodes due to their high lithium storage capacity,but their practical application is hindered by severe volume expansion during cycling, leading to mechanical degradation andcapacity fading. This study introduces a novel two-pot method for synthesizing silicon nanoparticles (Si NPs) to address thesechallenges. The method decouples precursor decomposition and nanoparticles deposition enabling in situ growth of Si NPs onnanographite substrates. By replacing hazardous silane precursors with polyvinyl alcohol or hydrogen gas, we eliminate safetyrisks while simplifying production. Scanning electron microscopy and electrochemical characterization confirm uniform Si NPdeposition. The fabricated electrodes displayed stable electrochemical performance with a capacity of 503 mAh/g after 100 cyclesin a half-cell configuration. This approach offers a safe route for producing high-performance silicon-based anodes.

Triboelectric nanogenerators (TENGs) represent a promising technology for energy harvesting and self-powered sensing with a wide range of applications. Despite their potential, challenges such as the need for cost-effective, large-area electrodes and engineering sustainable triboelectric materials remain, especially given the impending restrictions on single-use engineering plastics in Europe. To address these challenges, engineering nano-graphite-coated paper is presented as a sustainable and high-performance alternative for triboelectric layers. Moreover, this material, which can be produced on an industrial scale, offers a viable replacement for metal electrodes. The combination of nano-graphite and paper, with its large contact area and inherent surface roughness, enables ultra-high power densities exceeding 14 kW m−2, driven by electrostatic discharge at the surface. Beyond energy harvesting, smart sensors are developed for floors and walls that detect movements for security purposes and smart sheets that monitor body movements and physiological activities during sleep. The findings highlight the potential of this engineering paper to serve as an eco-friendly alternative to engineering plastics in TENGs and electrodes, opening new avenues for future applications. 

Harvesting energy from distributed mechanical motions has garnered significance in future power sources for small electronics and sensors. Although technologies like triboelectric nanogenerators have shown promising results, their efficacy hinges on the alignment of motion vectors and device architectures. Here, an approach employing stationary diode cells (DiCes) to generate electricity is presented. This approach leverages dynamically changing electrostatic fields to induce potential differences across diode junctions via electrostatic induction, which is verified theoretically and experimentally. DiCes constructed with multiple diodes can directly output DC voltage and current. A 0.02 m2 sized DiCe contains 360 diodes can supply a DC voltage and current of maximum 490 V and 1.08 mA, respectively, which equals a DC power density of 26.5 W<middle dot>m-2. Capable of functioning in both contact and non-contact modes, DiCes offer versatile applications, from wirelessly powering implanted medical devices to harvesting energy from vehicles and roads.

A recyclability perspective is essential in the sustainable development of energy storage devices, such as lithium-ion batteries (LIBs), but the development of LIBs prioritizes battery capacity and energy density over recyclability, and hence, the recycling methods are complex and the recycling rate is low compared to other technologies. To improve this situation, the underlying battery design must be changed and the material choices need to be made with a sustainable mindset. A suitable and effective approach is to utilize bio-materials, such as paper and electrode composites made from graphite and cellulose, and adopt already existing recycling methods connected to the paper industry. To address this, we have developed a concept for fabricating fully disposable and resource-efficient paper-based electrodes with a large-scale roll-to-roll coating operation in which the conductive material is a nanographite and microcrystalline cellulose mixture coated on a paper separator. The overall best result was achieved with coated roll 08 with a coat weight of 12.83(22) g/m2 and after calendering, the highest density of 1.117(97) g/cm3, as well as the highest electrical conductivity with a resistivity of 0.1293(17) m (Formula presented.) m. We also verified the use of this concept as an anode in LIB half-cell coin cells, showing a specific capacity of 147 mAh/g, i.e., 40% of graphite’s theoretical performance, and a good long-term stability of battery capacity over extended cycling. This concept highlights the potential of using paper as a separator and strengthens the outlook of a new design concept wherein paper can both act as a separator and a substrate for coating the anode material. 

Silicon materials are currently being explored for usage in lithium-ion battery anodes due to their high lithium storage capacity. We have developed a novel method, using a simple thermal treatment of low-cost silicon powder and nanographite, resulting in a composite where silicon nanoparticles are grown on the graphene surfaces. Electrodes fabricated from these Si-NG composites delivered a stable capacity of 489 mAh/g during 25 cycles, i.e. higher than conventional graphite anodes (theoretical capacity: 372 mAh/g). The method uses low-cost materials and avoids complex setups, thereby suggesting industrial scalability.

Lithium-ion batteries are pivotal in modern energy storage, commonly utilizing graphite anodes for their high theoretical capacity and long cycle life. However, graphite anodes face inherent limitations, such as restricted lithium-ion storage capacity and slow diffusion rates. Enhancing the porosity of graphite and increasing d-spacing in expanded graphite anodes have been explored to improve lithium-ion diffusion and intercalation. Recent advancements suggest that nanoscale modifications, such as utilizing nano-graphite and graphene, can further enhance performance. Laser processing has emerged as a promising technique for synthesizing and modifying graphite and graphene-related materials, offering control over surface defects and microstructure. Here, we demonstrate an industrially compatible one-step laser processing method to transform a nano-graphite and graphene mixture into a nanoporous matrix, significantly improving lithium-ion battery performance. The laser-processed anodes demonstrated significantly enhanced specific capacities at all charge rates, with improved relative performance at higher charge rates. Additionally, long-term cycling at 1 C showed that laser-processed cells outperformed their non-processed counterparts, with specific capacities of 323 and 241 mAh/g, respectively.

Considerable research has been devoted to the development of cathode materials for Al-ion batteries, but challenges remain regarding the behavior of aluminum anodes. Inert oxide (Al2O3) film on Al surfaces presents a barrier to electrochemical activity. The structure of the oxide film needs to be weakened to facilitate ion transfer during electrochemical activity. This study addresses oxide film challenges by studying Al alloy anodes with different iron content. The results reveal that using an anode of 99% Al 1% Fe in a cell increases the cycling lifetime by 48%, compared to a 99.99% Al anode. The improvement observed with the 99% Al 1% Fe anode is attributed to its fractional surface area corrosion being about 12% larger than that of a 99.99% Al anode. This is coupled to precipitation of a higher number of Al3Fe particles, which are evenly scattered in the Al matrix of 99% Al 1% Fe. These Al3Fe particles constitute weak spots in the oxide film for the electrolyte to attack, and access to fresh Al. The addition of iron to an Al anode thus offers a cheap and easy route for targeting the oxide passivating film challenge in Al-ion batteries.

Inks and toners used for printing contain materials, such as polyester, with strong triboelectric properties to enhance the binding effects, making wastepaper, such as magazines and newspapers, good candidates for triboelectric materials. Herein, high-output power triboelectric nanogenerators (TENGs) that utilize wastepaper as triboelectric layers (wastepaper-based triboelectric nanogenerators (WP–TENGs)) are reported. Journal paper and office copy paper wastes are investigated. The results show that the maximum power densities of the WP–TENGs reach 43.5 W m−2, which is approximately 250 times the previously reported output of the TENG with a recycled triboelectric layer made from wastepaper. The maximum open circuit voltage (V OC) and short circuit current (I SC) are 774 V and 3.92 mA (784 mA m−2), respectively. These findings can be applied to extend the life cycle of printed papers for energy harvesting, and they can later be applied for materials recycling to enhance the sustainable development of our society. 

The triboelectric properties of the tribolayers are essential factors affecting the current density of triboelectric nanogenerators (TENGs). To enhance the current density, composites have been developed to tune their triboelectric properties. Previous studies have reported enhanced TENG performance with composite materials, primarily based on their composition, while chemical interactions between the components have been less analyzed. In this study, we report a novel approach to improve the current density of a TENG by introducing dipole-dipole interactions between a nylon filter membrane and graphene oxide (GO) through hydrogen bonds. The Raman spectroscopy confirmed the occurrence of the interactions resulting from hydrogen bonding. The enhancing mechanisms of hydrogen bonds were further analyzed by Kelvin probe force microscope (KPFM) measurement, which demonstrated that hydrogen bonding could influence the surface potential of the coated GO, leading to increased output of the nylon/GO@NFM TENG (NGN-TENG). Our results show that an ultrahigh current density of 1757 mA·m−2 was obtained with a 2 × 2 cm2 NGN-TENG. Additionally, we demonstrated the feasibility of using the NGN-TENG as a motion sensor to sense finger motions. These findings suggest that the introduction of hydrogen bonds in TENG composites can provide a promising route for improving their performance.