The composite of manganese dioxide (MnO2) with high theoretical capacity (1230 mAh g−1) and carbon nanofiber paper with high electrical conductivity is attracting attention as a next-generation ...battery anode material. This study proposes a facile route for coating mesoporous MnO2 on the carbon fiber by low-temperature reduction of KMnO4 and intercalating graphene into the carbon paper through vacuum filtration. The MnO2 coated carbon nanofiber (MOCNF) is synthesized in the form of paper, while maintaining the flexibility and strength with graphene intercalated between MOCNF papers. The resulting paper is applied for the lithium ion battery anode without any current collector, binder and conductor. This free-standing electrode has a discharge capacity of 945 mAh g−1 at 100 mA g−1 and shows a high discharge capacity of 545 mAh g−1 at 1000 mA g−1 even after 1000 cycles. This stable cycle performance originates from the mesoporosity of MnO2 and the intercalation of graphene, which accelerates the kinetics of redox reaction and mitigates the electrochemical isolation of MnO2 from the carbon nanofibers. This paper-type material can be a next-generation battery anode with considerable flexibility and capacity. Furthermore, the facile method of MnO2 coating and graphene intercalation can be applied to the other electrode synthesis.
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•Mesoporous MnO2 was coated on the carbon fiber by low-temperature reduction of KMnO4.•Graphene layers were intercalated into the electrospun carbon sheets through facile vacuum filtration.•Resultant paper was used as a lithium ion battery anode without any current collector, binder and conductor.•MnO2 induced high capacity, and intercalated graphene prevented electrochemical isolation of MnO2.
Liquid metal extraction (LME) for recycling rare-earth elements from magnets is studied, in the present study, to examine its suitability as an environmentally friendly alternative for a circular ...economy. While Nd (neodymium) extraction efficiency can easily reach almost 100%, based on the high reactivity of Mg (magnesium), Dy (dysprosium) extraction has been limited because of the Dy-Fe intermetallic phase as the main extractive bottleneck. In the present paper, the boro-additive effect is designed thermodynamically and examined in the ternary and quinary systems to improve the selectivity of recovery. Based on the strong chemical affinity between B (boron) and Fe, the effect of excess boron, which is produced by the depletion of B in FeB by Mg, successfully resulted in the formation of Fe
B instead of Dy-Fe bonding. However, the growth of the Fe
B layer, which is the reason for the isolated Mg, leads to the production of other byproducts, rare-earth borides (
B
,
= Nd and Dy), as the side effect. By adjusting the ratio of FeB, the extraction efficiency of Dy over 12 h with FeB addition is improved to 80%, which is almost the same extraction efficiency of the conventional LME process over 24 h.
In this study, we present a method for assembling biofunctionalized paper into a multiform structured scaffold system for reliable tissue regeneration using an origami-based approach. The surface of ...a paper was conformally modified with a poly(styrene-comaleic anhydride) layer via initiated chemical vapor deposition followed by the immobilization of poly-L-lysine (PLL) and deposition of Ca²⁺. This procedure ensures the formation of alginate hydrogel on the paper due to Ca²⁺ diffusion. Furthermore, strong adhesion of the alginate hydrogel on the paper onto the paper substrate was achieved due to an electrostatic interaction between the alginate and PLL. The developed scaffold system was versatile and allowed area-selective cell seeding. Also, the hydrogel-laden paper could be folded freely into 3D tissue-like structures using a simple origami-based method. The cylindrically constructed paper scaffold system with chondrocytes was applied into a three-ring defect trachea in rabbits. The transplanted engineered tissues replaced the native trachea without stenosis after 4 wks. As for the custom-built scaffold system, the hydrogel-laden paper system will provide a robust and facile method for the formation of tissues mimicking native tissue constructs.
Wearable electronics represent a significant paradigm shift in consumer electronics since they eliminate the necessity for separate carriage of devices. In particular, integration of flexible ...electronic devices with clothes, glasses, watches, and skin will bring new opportunities beyond what can be imagined by current inflexible counterparts. Although considerable progresses have been seen for wearable electronics, lithium rechargeable batteries, the power sources of the devices, do not keep pace with such progresses due to tenuous mechanical stabilities, causing them to remain as the limiting elements in the entire technology. Herein, we revisit the key components of the battery (current collector, binder, and separator) and replace them with the materials that support robust mechanical endurance of the battery. The final full-cells in the forms of clothes and watchstraps exhibited comparable electrochemical performance to those of conventional metal foil-based cells even under severe folding-unfolding motions simulating actual wearing conditions. Furthermore, the wearable textile battery was integrated with flexible and lightweight solar cells on the battery pouch to enable convenient solar-charging capabilities.
Polymeric binders play an important role in electrochemical performance of high-capacity silicon (Si) anodes that usually suffer from severe capacity fading due to unparalleled volume change of Si ...during cycling. In an effort to find efficient polymeric binders that could mitigate such capacity fading, herein, we introduce polymerized β-cyclodextrin (β-CDp) binder for Si nanoparticle anodes. Unlike one-dimensional binders, hyperbranched network structure of β-CDp presents multidimensional hydrogen-bonding interactions with Si particles and therefore offers robust contacts between both components. Even the Si nanoparticles that lost the original contacts with the binder during cycling recover within the multidimensional binder network, thus creating a self-healing effect. Utilizing these advantageous features, β-CDp-based Si electrode shows markedly improved cycling performance compared to those of other well-known binder cases, especially when combined with linear polymers at an appropriate ratio to form hybrid binders.
Electronic skins (e-skins)-electronic sensors mechanically compliant to human skin-have long been developed as an ideal electronic platform for noninvasive human health monitoring. For reliable ...physical health monitoring, the interface between the e-skin and human skin must be conformal and intact consistently. However, conventional e-skins cannot perfectly permeate sweat in normal day-to-day activities, resulting in degradation of the intimate interface over time and impeding stable physical sensing. Here, we present a sweat pore-inspired perforated e-skin that can effectively suppress sweat accumulation and allow inorganic sensors to obtain physical health information without malfunctioning. The auxetic dumbbell through-hole patterns in perforated e-skins lead to synergistic effects on physical properties including mechanical reliability, conformability, areal mass density, and adhesion to the skin. The perforated e-skin allows one to laminate onto the skin with consistent homeostasis, enabling multiple inorganic sensors on the skin to reliably monitor the wearer's health over a period of weeks.
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•Adhesion energy of the graphene–Cu interface is controlled by various liquids.•Thermodynamic work of adhesion reveals the mechanism of adhesion control.•Effective reduction of damage ...to graphene during the transfer process is achieved.•Transferred graphene shows superior properties and is applicable to flexible devices.
Mechanical transfer of synthesized graphene has attracted considerable attention owing to its widely applicable and substrate recyclable process. Particularly, the interfacial adhesion energy between graphene and the growth Cu substrate plays an important role in the mechanical transfer of graphene without compromising its quality and properties. However, the quantitative control of adhesion for the graphene–Cu interface has remained a challenge. Here, we introduce liquid-assisted adhesion control of the graphene–Cu interface for a damage-free mechanical transfer process. It is demonstrated using environmentally assisted fracture mechanics testing that the adhesion energy of the graphene–Cu interface can be controlled by separating the interface in liquid environments. Analysis of the wetting characteristics for each surface and the thermodynamic work of adhesion calculation reveal the mechanism of liquid-assisted adhesion control. Liquid-assisted adhesion control effectively reduces structural defects in the transferred graphene layers. Finally, the applicability of the adhesion-controlled graphene transfer method to flexible and stretchable electronics is investigated.
Proton exchange membrane fuel cell (PEMFC) is a renewable energy source rapidly approaching commercial viability. The performance is significantly affected by the transfer of fluid, charges, and ...heat; gas diffusion layer (GDL) is primarily concerned with the consistent transfer of these components, which are heavily influenced by the material and design. High-efficiency GDL must have excellent thermal conductivity, electrical conductivity, permeability, corrosion resistance, and high mechanical characteristics. The first step in creating a high-performance GDL is selecting the appropriate material. Therefore, titanium is a suitable substitute for steel or carbon due to its high strength-to-weight and superior corrosion resistance. The second crucial parameter is the fabrication method that governs all the properties. This review seeks to comprehend numerous fabrication methods such as tape casting, 3D printing, freeze casting, phase separation technique, and lithography, along with the porosity controller in each process such as partial sintering, input design, ice structure, pore agent, etching time, and mask width. Moreover, other GDL properties are being studied, including microstructure and morphology. In the future, GeoDict simulation is highly recommended for optimizing various GDL properties, as it is frequently used for other porous materials. The approach can save time and energy compared to intensive experimental work.
The development of
small-molecule acceptors (SMAs) has significantly
enhanced the power conversion efficiency (PCE) of polymer solar cells
(PSCs); however, the inferior mechanical properties of ...SMA-based PSCs
often limit their long-term stability and application in wearable
power generators. Herein, we demonstrate a simple and effective strategy
for enhancing the mechanical robustness and PCE of PSCs by incorporating
a high-molecular-weight (MW) polymer acceptor (
P
A
, P(NDI2OD-T2)). The addition of 10–20 wt %
P
A
leads to a more than 4-fold increase in the
mechanical ductility of the SMA-based PSCs in terms of the crack onset
strain (COS). At the same time, the incorporation of
P
A
into the active layer improves the charge transport
and recombination properties, increasing the PCE of the PSC from 14.6
to 15.4%. The added
P
A
s act as tie molecules,
providing mechanical and electrical bridges between adjacent domains
of SMAs. Thus, for the first time, we produce highly efficient and
mechanically robust PSCs with a 15% PCE and 10% COS at the same time,
thereby demonstrating their great potential as stretchable or wearable
power generators. To understand the origin of the dual enhancements
realized by
P
A
, we investigate the influence
of the
P
A
content on electrical, structural,
and morphological properties of the PSCs.
Transfer printing of inorganic thin-film semiconductors has attracted considerable attention to realize high-performance soft electronics on unusual substrates. However, conventional transfer ...technologies including elastomeric transfer printing, laser-assisted transfer, and electrostatic transfer still have challenging issues such as stamp reusability, additional adhesives, and device damage. Here, a micro-vacuum assisted selective transfer is reported to assemble micro-sized inorganic semiconductors onto unconventional substrates. 20 μm-sized micro-hole arrays are formed via laser-induced etching technology on a glass substrate. The vacuum controllable module, consisting of a laser-drilled glass and hard-polydimethylsiloxane micro-channels, enables selective modulation of micro-vacuum suction force on microchip arrays. Ultrahigh adhesion switchability of 3.364 × 10
, accomplished by pressure control during the micro-vacuum transfer procedure, facilitates the pick-up and release of thin-film semiconductors without additional adhesives and chip damage. Heterogeneous integration of III-V materials and silicon is demonstrated by assembling microchips with diverse shapes and sizes from different mother wafers on the same plane. Multiple selective transfers are implemented by independent pressure control of two separate vacuum channels with a high transfer yield of 98.06%. Finally, flexible micro light-emitting diodes and transistors with uniform electrical/optical properties are fabricated via micro-vacuum assisted selective transfer.
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