Electronic Conductivity Research Articles

Solid-state preparation of in-situ grown graphene-embedded bi-metallic NiMnS hybrids for high-performance asymmetric supercapacitor

Endowed with intrinsic redox-rich features and superior electronic conductivities, mixed-metallic sulphides offer high prospects in electrochemical charge storage, especially in supercapacitors. Hence, their rational design and scalable preparation are of great scientific significance. Herein, we report the in-situ growth of nanostructured hybrids of NiMnS directly embedded into graphene sheets by a straightforward, scalable solid-state synthesis method. In this environment-friendly approach, the metal precursors, elemental sulphur, and graphene oxide (GO) are homogeneously mixed under ball-milling, followed by controlled thermal treatment. Incited from their unique synergistic contribution, the resulting NiMnS/G hybrids exhibit impressive electrochemical performance as a battery-type electrode in an aqueous electrolyte. The NiMnS/G hybrid electrode displayed a high specific capacity of 871.7C g−1 at 2 A g−1 with superior rate capability. Moreover, the asymmetric supercapacitor (ASC) device assembled based on the surface-enhanced NiMnS/G nanohybrid as the positive electrode and activated carbon (AC) as the negative electrode achieves an intriguing performance, delivering a maximum energy density of 53.4 Wh kg−1 at a power density of 500 W kg−1. The ASCs were successfully cycled over 10,000 cycles with 87 % capacitance retention and around 99 % Coulombic efficiency. This simple yet scalable strategy holds high promise and may pave the way for preparing other multimetallic sulphide-based hybrid electrode materials for electrochemical energy storage applications.

Multi-core–shell nanoboxes comprising polydopamine-derived C coated NiCo@C and FeCo@C nanohybrid for enhanced electrochemical quantification of nitrofurantoin

The development of a high-performance electrochemical sensing platform for monitoring nitrofurantoin (NFT) levels in various real samples plays an important role in the research community worldwide. To accomplish this objective, the crucial challenge is to construct sensing interfaces with outstanding electrocatalytic capabilities. In the present work, a highly efficient metal@carbon electrocatalyst with porous and multi-core–shell nanobox structure comprising polydopamine (PDA)-derived C coated NiCo@C and FeCo@C nanohybrid (named as NiCo@C/FeCo@C@C) was fabricated by simply pyrolyzing NiCo@FeCo Prussian blue analogues (PBA)@PDA. The carbonization of PDA into carbon shells protected the framework from collapsing during high-temperature pyrolysis process, thus enlarging the specific surface areas and porosity. The NiCo@C/FeCo@C@C composite attained an enhanced electrochemical capability, such as an outstanding electronic conductivity from the double carbon shell with porous structure, a large number of active sites and a high electrocatalytic activity from the metallic alloy nanoparticles, which exhibited a highly sensitive response to NFT. Under optimized experimental conditions, the established NiCo@C/FeCo@C@C electrochemical sensor displayed a wide linear range of 0.05–100 μM for NFT determination, coupled with a low detection limit of 14 nM. The practical feasibility of this sensor was also confirmed by the analysis of NFT in tablet and lake water samples with outstanding recovery rates. Moreover, the sustainability of the sensor was demonstrated through its prominent performance in high reproducibility, selectivity and long-term stability. This study thus introduces an innovative approach for the advance of highly efficient electrocatalysts in the area of electrochemical sensing.

One step glow-discharge electrolysis-based preparation of Al doped Ni-Co layered double hydroxide/ graphene oxide as supercapacitor electrode material

Nickel-cobalt layered double hydroxides (LDHs) are promising materials for supercapacitor electrodes; however, they face challenges in terms of cycling stability and rate capability owing to agglomeration and low conductivity. In this study, Ni(III)CoAlx-LDH/GO with an extended layer spacing and excellent electronic conductivity was synthesized by one-step glow discharge electrolysis. A nickel–cobalt alloy was used as the anode, a graphite rod as the cathode, and sodium chloride as the electrolyte. In addition, incorporating an appropriate amount of aluminum chloride into the electrolyte can alter the microstructure of the electrode material, leading to enhanced electrochemical performance. Ni(III)CoAl0.2-LDH/GO, synthesized using 0.2 g AlCl3, demonstrated exceptional electrochemical performance of 1014C g−1 at 2 A/g. At a current density of 5 A/g, the capacitance retention rate was 85.3 % after 10,000 cycles, indicating strong cyclic stability. Moreover, an asymmetric supercapacitor built with Ni(III)CoAl0.2-LDH/GO as the anode and commercial activated carbon as the cathode achieved a specific capacitance of 146.2F/g at a current density of 1 A/g. This device demonstrated outstanding circular stability, retaining 85.07 % of its capacitance after 10,000 cycles. In addition, the device achieves relatively high energy density and power density (energy density of 66.63 Wh kg−1 at a power density of 1022.23 W kg−1). This study introduces a novel synthesis method for the preparation of high-performance electrode materials aimed at advancing energy storage devices.

Design and synthesis of FeS2/graphite sandwich structure with enhanced lithium-storage performance for lithium-ion and solid-state lithium batteries

As a conversion-type cathode material, FeS2 emerges as a promising candidate for the next generation of energy storage solutions, attributed to its cost-effectiveness, environment-friendliness and high theoretical capacity. However, several challenges hinder its practical application, including sluggish kinetics, insulating reaction products and significant volume fluctuation during cycling, which collectively compromise its rate capability and cycle stability. Herein, a well-designed sandwich structure of FeS2 embedded between graphite layers (FeS2/C) is obtained using a chloride intercalation and sulfidation strategy. The layered graphite-FeS2-graphite configuration boosts the active sites and adsorption capacity of Li+, thereby guaranteeing a high reversible capacity. Furthermore, the graphitic carbon matrix serves a dual purpose: it enhances electronic conductivity and restrain the volume fluctuation of FeS2 during long cycling. This combination ensures robust electrochemical kinetics, structural integrity and long life. Consequently, the FeS2/C composites exhibit exceptional lithium storage performance, achieving capacities of 506.2 mAh g−1 at 0.5 A/g and 277.2 mAh g−1 at 5.0 A/g. Additionally, the FeS2/C composites show promising potential as cathodes for all solid-state lithium batteries, showcasing high specific capacities of 658.0 mAh g−1 at 0.1 A/g for the second cycle and maintaining a cycle performance of 288.5 mAh g−1 after 800 cycles at 0.5 A/g. These values surpass the second discharge specific capacity of 96.1 mAh g−1 and cycle capacity of 25.3 mAh g−1 observed for Fe2O3/C composites. The discharge mechanism of FeS2/C composites was further characterized through in-situ transmission electron microscope test. This work provides valuable insights for designing and synthesizing FeS2, highlighting its potential for lithium ion storage and all solid-state lithium batteries.

NiS2/FeS2 binary nanoparticles confined in interconnected carbon framework with regulated pore structure enabled by citric acid for enhanced sodium storage properties

Recently, pyrite iron disulfide (FeS2) has emerged as a promising anode candidate for sodium-ion batteries (SIBs) due to its high theoretical capacity, affordability, non-toxicity and abundant resource in nature. However, the utilization of FeS2 still confronts the challenges of inferior rate capability and cycling instability for sodium storage, stemming from its low electronic conductivity and substantial volume changes during cycling. Herein, to address these obstacles, NiS2/FeS2 binary nanoparticles encapsulated within a network of interconnected N-doped porous carbon framework (NiS2/FeS2@NPC) are prepared by a successive solid-state ball milling, carbonization and sulfurization strategy with coordination complex of nickel iron Prussian blue analogue (NiFe-PBA) as precursor. The introduction of citric acid plays a critical role for the formation of interconnected carbon framework with regulated internal porous structure, thereby achieving heterostructured NiS2/FeS2@NPC with modulated specific surface area and pore volume. The rational design of interconnected N-doped porous carbon framework and heterogeneous structure guarantees rapid ion/electron transport kinetics, alleviated mechanical stress, and enhanced structural integrity. Benefitting from these advantages, the optimal NiS2/FeS2@NPC-1 electrode exhibits a high reversible capacity (545 mAh/g at 1 A/g), superior rate capability (267 mAh/g at 5 A/g) and ultrastable long-term cycling performance (98.5 % retention over 1000 cycles at 5 A/g). This study presents a novel and efficient design approach for creating durable and high-rate anode materials based on metal sulfides for SIBs.

Simultaneous modification of Na+-rich and Mn2+-doping on Na3V2(PO4)3 for superior electrochemical performance: Experimental and theoretical study

Recently, the weak intrinsic conductivity limits the application of Na3V2(PO4)3 (NVP). Herein, a simultaneous optimized scheme is proposed to comprehensively improve the kinetic properties and modify the electronic structure of NVP. Significantly, bivalent Mn2+ is introduced to occupy V3+ site, resulting in favorable p-type substitution effects to produce more hole carriers thus accelerating electronic conductivity. Moreover, Mn2+ possesses a larger ionic radius than V3+ (0.067nm vs. 0.064nm), thus Mn2+ behaves efficient pillar effect to enhance the skeleton steadiness and broaden the migration pathway of Na+, indicating notably improved structure stability and ionic transport rate. Moreover, for the electronic equilibrium of the system, more Na+ will be introduced into the NVP bulk system after Mn2+ doping and Na-rich Na3+xV2-xMnx(PO4)3 compounds are designed, supplying more active carriers to participate the de-intercalation process and generating more reversible capacity. In addition, the optimized electronic construction of Mn2+ doped NVP is deeply investigated by DFT calculations, demonstrating the reduced band gap and declined energy barrier for Na+ transportation. Meanwhile, moderate CNTs are introduced together with coated carbon layers to construct an effective three-dimensional conductive network, significantly elevating the electron transfer property. The enwrapped CNTs also restrain the overgrowth and reunion of powders, thereby reducing the grain size and cutting down the transportation ways of Na+. Finally, the modified Na3.04V1.96Mn0.04(PO4)3@CNTs reveals superior electrochemical performance. It releases 120.8 mAh g-1 at 0.1C. It maintains remarkable retention value of 89.8% at 10C after 1000 cycles, suggesting a relatively low attenuation rate of 0.011% per cycle. Even at 50C, it still delivers a capacity of 63.6 mAh g-1 and keeps 68.2% after 4000 cycles.

A needle-like covalent organic framework with highly accessible phenazine and π-conjugated structure for potassium storage and its reaction mechanism

Covalent organic frameworks (COFs) with features of light elements, tailored functional groups, and designable structures are regarded as promising candidates for future potassium ion batteries (PIBs), while the low electronic conductivity and intricate reaction mechanism restrict their practical application. Herein, a needle-like COF material, marked as CPT, was synthesized by an acid-catalyzed condensation reaction between cyclohexanehexone and 2,3,7,8-phenazine tetramine. It was constructed by interconnected phenazine with π-conjugated structures, displaying the advantages of rich electron delocalization, thin sheet thickness, and low dissolution in electrolytes. When applied as the anode of PIBs, the CPT anode delivered a high reversible capacity of 305 mAh g−1 at 0.1 A g−1 over 200 cycles. Besides, it also exhibited promising potential for “high-temperature” application potential by retaining a capacity of 400 mAh g−1 at 0.1 A g−1 after 100 cycles at 45 °C. Full cells with CPT anode and potassiathed organic cathode displayed good cycling and rate performances. Furthermore, the step-wise K-storage mechanism was jointly determined by in-situ characterization techniques and theoretical calculations. This study not only presents a molecular engineering approach for designing organic materials but also provides novel insights into the underlying mechanism governing potassium storage.

Synergistic effect of NASICON Na3V2(PO4)2F3 and 2D MXene for high-performance symmetric Sodium-ion batteries

Sodium fluorophosphate-based Na3V2(PO4)2F3 (NVPF) cathode materials have been widely analyzed in Sodium-ion batteries (SIB) owing to their high energy density and high working voltage. However, the low electronic conductivity of NVPF is a factor hindering their efficient use. To enhance the electronic conductivity of NVPF, in this work, a porous Na3V2(PO4)2F3 and a 2D Ti3C2-based MXene nanocomposite was synthesized using a facile sol-gel method. The NVPF, with the presence of two active redox couples, is a suitable choice for symmetric batteries. The NVPF + 2D MXene nanocomposite was analyzed for its structural and thermal characteristics, and a symmetric cell prepared from them was investigated for its electrochemical characteristics. Structural analysis of the materials developed indicates that the MXene addition has not altered the crystal structure of the NVPF. A remarkable improvement in the electrochemical performance of NVPF in the sodium symmetric cell is noticed, as indicated by its high specific discharge capacity of 92mAhg-1 at 1C for the MXene-incorporated composite structures. This improvement in electrochemical behaviour is confirmed in the rate capability curves, GCD curves, and GITT curves. The diffusion coefficient values obtained from GITT analysis showed improved kinetics in the synthesized material due to the MXene incorporation. The calculated values of the diffusion coefficient of Na+confirms the accelerated kinetics of Na+ ion migration during the intercalation/de-intercalation process in the MXene 5wt% nanocomposites, with a value of 9.57 × 10–9 cm2s-1 when compared to 4. 14 × 10–9 cm2s-1 for the pristine sample.

High-performance flexible CoFe2O4/N-doped carbon nanofiber composite anode materials for sodium-ion batteries

Graphite is traditionally used as an anode material but is unsuitable for use in sodium-ion batteries because it has a low specific capacity and poor safety characteristics, it is therefore necessary to develop alternative anode materials. Flexible CoFe2O4 nanoparticle/N-doped carbon nanofiber films were prepared by electrospinning and calcination. The advantages of this process included inexpensive starting materials, easy preparation, and suitability for commercialization. The inherent shortcomings of CoFe2O4, such as poor electronic conductivity and large changes in volume, were mitigated via elemental doping and the formation of composites with high-quality carbon materials. Nitrogen-doped carbon nanofibers with large specific surface areas and superior mechanical properties were used as the supporting skeleton of the material. These nanofibers limited the volume expansion of CoFe2O4 throughout the cycling process and increased the ion diffusion velocity in the material. The optimal integration of nanoscale CoFe2O4 particles, which possess a higher theoretical specific capacity, with a nitrogen-doped carbon nanofiber conductive framework featuring a crosslinked three-dimensional structure facilitated the infiltration of the electrolyte into the electrode. This integration reduced the diffusion distance of sodium ions and effectively reduced the volume expansion of the material, as well as damage to the material during the electrochemical reaction. After 200 cycles at a current density of 0.1 A g−1, it provided a high sodium storage capacity of 365.7 mA h g−1. The capacity was maintained at 176.3 mA h g−1 even at a high current density of 2 A g−1. Exhibits good cycle stability.

A La1.85Mg0.15Ce2O7-δ-based ceramic hydrogen pump for stable hydrogen separation out of the H2-CO2 mixtures

Currently, hydrogen is largely produced from steam methane reforming with the H2-and CO2-containing stream as the process gas. It is highly relevant to explore new pathways to efficiently separate hydrogen out of the H2-CO2 mixed gases. In the present work, a novel ceramic hydrogen pump for H2 purification is designed with thin La1.85Mg0.15Ce2O7-δ (LMCO) electrolytes supported by symmetrical Ni-LMCO electrodes, and is fabricated by using the tape casting, tape lamination and co-sintering techniques. Chemical stability and proton conductivities are evaluated for fluorite LMCO oxides in humidified 10 % H2-90 % CO2. Superior stability of LMCO in CO2 allows for stable and selective hydrogen separation out of humidified 10 % H2–90 % CO2. The Faraday’s efficiency decreases pronouncedly with an increase in the operation temperature, e.g., ≈ 30 % at 700 ℃ vs. ≈ 76 % at 500 ℃, due to increasingly high reduction susceptibility of Ce4+ to Ce3+ and the resultant electronic conductivities. A reasonable H2 flux of 0.57 mL·min−1·cm−2 is achieved at 500 °C and 0.25 V with electricity consumption of 0.72 kWh·Nm−3 H2. Operation at a higher pumping voltage of 0.49 V yields a larger H2 flux of 1.16 mL·min−1·cm−2, but simultaneously results in higher electricity consumption of 1.42 kWh·Nm−3 H2. Impedance analysis reveals that the H2 fluxes for the present ceramic hydrogen pump are predominantly limited by high resistances against bulk transport of protons through the LMCO electrolytes as well as sluggish hydrogen oxidation kinetics in humidified 10 % H2–90 % CO2.

High-Power and Long-Lifespan Rechargeable Ion Batteries based on Na+-Confined Na+/Mg2+ Coinsertion Chemistry.

Magnesium-sodium hybrid ion batteries (MSHIBs) are expected to achieve excellent rate capability. However, existing MSHIB cathodes exhibit low ionic conductivity and poor structural stability, resulting in low power density and cycle lifespan. Herein, sodium-rich Na3.7V6O16·2.9H2O (Na-rich NVO) nanobelts are synthesized as MSHIB cathodes. Excess Na+ induced NaO5 and NaO3 interlayer pins, which ensures NVO structural stability to accommodate Mg2+ and Na+. They also confine the migration pathway of cations to the diffusion direction, lowering the migration barriers of Mg2+ and enhancing the ionic conductivity. Excess interlayer Na+ increases the electronic conductivity of the involved Na-rich NVO cathode. The cathode exhibits a high Mg2+ diffusion coefficient, and the resulting MSHIBs exhibit a power density of 3.4kW kg-1 and a lifespan of 20 000 cycles at 5.0 A g-1, with a capacity retention rate of 85%. Overall, this study paves the way for designing and developing fast-charging secondary batteries.

Enhancing Li4Ti5O12 Anodes for High‐Performance Batteries: Ti3+ Induction via Plasma‐Enhanced Chemical Vapor Deposition and Dual Carbon/LLZO Coatings

AbstractLithium titanium oxide (LTO) is a promising anode material due to its ability to store lithium through intercalation reactions. However, its electrochemical performance is limited by poor electron conductivity and side reactions with the electrolyte. In this study, plasma‐enhanced chemical vapor deposition (PECVD) is employed to introduce oxygen vacancies and self‐doped Ti3+ into LTO to improve the internal conductivity. Subsequent carbon coating and aluminum‐doped lithium lanthanum zirconate garnet (LLZO) layers resulted in a multi‐layered composite denoted as LTO−L‐x. Morphological analyses using SEM and TEM demonstrated the successful growth of Al‐doped LLZO on carbon‐coated LTO. Aluminum ions in LLZO cubic structure are crucial for stabilizing the high ionic conductive phase during cooling, as confirmed by X‐ray diffraction. The dual coating layers have a significant impact on the rate capability, reducing polarization gaps and enabling higher capacities at various current rates. Long‐term cycling tests reveal the robustness of the composite, with LTO−L‐1.0 retaining 90.8 % capacity after 4000 cycles at 1.0 A g−1. This underscores the sustained high electronic and ionic conductivity facilitated by the dual coating layers. The study contributes to the design of advanced anode materials for lithium‐ion batteries, emphasizing the importance of tailored coating strategies to address conductivity and stability challenges.

Synthesis and Properties of Nickel Copper Phosphorus (NixCuyPz) Catalyst

Nowadays, scientists around the world are paying more attention to renewable hydrogen fuels. There is a growing need for precious metal catalysts to calculate the cost of obtaining renewable energy, an efficient method of producing H2 by electrolysis of water, as well as to facilitate the decomposition of water into its elemental parts. Today, due to the increase in the problem of the shortage of energy resources and the growing of CO2 emissions into the atmosphere, attention is being paid to hydrogen energy. However, the production of H2 requires low-cost, efficient catalysts that facilitate hydrogen/oxygen separation reactions in the water splitting. For this purpose, intermediate metal phosphides (Fe, Co, Ni, Cu, Mo, W) were used as effective electrocatalysts for water decomposition. The catalytic activity of intermediate metal phosphides to form hydrogen is largely dependent on the phosphorus content, but the P atoms play an important role in increasing efficiency. The production of hydrogen by electrolysis of water on the basis of bifunctional catalysts has good prospects for use in the energy industry. In the article, the one-step hydrothermal synthesis method and physico-chemical (electronic structure and conductivity, structure morphology) of double metal phosphide with NixCuyPz composition were studied.

Heterostructured GCN Nanosheets/ZnO nanoflowers for enhanced TMO loading: From high-performance three electrode systems to printed flexible asymmetric supercapacitors

Transition metal oxides (TMOs) are widely used in the development of high-energy-density devices due to their multiple oxidation states and their frequent heterostructuring with carbon-based materials. However, the synthesis process often leads to severe nanoparticle agglomeration and weak synergistic effects with carbon-based templates, thereby limiting their application potential. In this study, we constructed graphitic carbon nitride (GCN) nanosheets/ZnO nanoflowers (NFs) structures with high TMOs loading by utilizing GCN nanosheets, which are rich in surface nitrogen content, as enriched templates for metal ions in conjunction with ultrasonic cavitation. Compared with GCN nanosheets/ZnO nanoparticles (NPs), the ZnO NFs exhibited vertical growth and a fluffy structure on a 2D material template, which resulted in high electronic conductivity, a large effective surface area, hierarchical pores, and strong synergistic interactions with GCNs, thus improving electrochemical performance. This structural enhancement enabled the GCN/ZnO NFs electrodes to achieve a high specific capacitance of 1524F g−1 at a current density of 1 A g−1 in a three-electrode supercapacitor system. Additionally, we formulated GCN/ZnO NFs into electronic inks and used them for the mass production of flexible supercapacitors with the aid of dispensing printing technology. These flexible supercapacitors retained 94% of their specific capacitance even under extreme conditions of 90° torsion. Our proposed strategy of modulating TMOs and 2D structures can create active electrode materials with higher loading capacities, thereby enabling comprehensive customization in material design and device preparation processes.

Sodium ion conduction in perovskite-type sodium lanthanum niobate ceramics

The electrical conductivity of NaxLa(1−x)/3NbO3 ceramics has been studied over a composition range of 0.15 ≤ x ≤ 0.45 to identify optimal conductivity conditions and to elucidate the structural and chemical factors affecting the Na+ ion conductivity. The composition with x = 0.25 achieves the highest total conductivity of 7.0 × 10−4 S cm−1 at 350 °C, with Na+ ion transference number of unity. The random distribution of Na, La and vacancy in the two crystallographically independent A sites in perovskite structures significantly impacts the conductivity. In addition, NaxLa(1−x)/3NbO3 perovskite ceramics exhibit high dielectric constants (εr = 220−470) and suppressed electronic conductivity, making them potentially beneficial as an interfacial material to mitigate chemical potential differences between electrolytes and electrode active materials.

Triphenylene-Based 2D cMOFs: Unraveling the H2S Sensing Mechanism and Applications for a Real-Time Wireless Chemiresistive Sensor.

Two-dimensional conductive metal-organic frameworks (2D cMOFs) stand at the forefront of chemiresistive sensing innovations due to their high surface areas, distinctive morphologies, and substantial electronic conductivity. Particularly, 2D cMOFs crafted using 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) and 2,3,6,7,10,11-hexaiminotriphenylene (HITP) organic ligands have garnered a large amount of attention due to their designable active sites and proper conductive characteristics. Nevertheless, a deeper exploration into their sensing mechanisms is imperative for a comprehensive understanding of the intrinsic chemistry, which is crucial for the intricate design of specialized 2D cMOF chemiresistive sensors. In this study, we fabricate six M-HXTP (M = Co, Ni, and Cu; X = H and I) chemiresistive sensors, focusing on the application of hydrogen sulfide (H2S) detection. Among these, the 2D cMOFs incorporating Cu metal manifested a remarkably enhanced response to H2S. A combination of experimental and computational studies unveils the mechanisms of sulfur oxidation and Cu reduction, wherein distortion of the reduced MX4 cluster markedly amplifies the sensing response. Lastly, a real-time and portable wireless H2S sensing module has been demonstrated by using the Cu-HHTP composite material, highlighting the substantial practical significance and potential applicability.

3D printed conductive hydrogel based on silk fibroin and tetramer-grafted-polyethylenimine micelle for body-motion monitoring

Conductive hydrogels hold significant promise for applications in flexible wearable, soft robotics, implantable devices, and other fields, which offer distinct advantages due to their biomimetic structures, intrinsic properties, and biocompatibility. This study builds upon our previous research by fabricating a conductive hydrogel through the combination of 30 % Pluronic F127 and aniline tetramer-grafted-polyethyleneimine (AT-PEI) copolymers. To enhance the properties of hydrogels, we successfully engineered silk fibroin-based conductive hydrogels (SF-AD) by inducing the transition of silk fibroin from a random coil to a β-sheet structure using the F127 and AT-PEI/DNA complex (AD), endowing the hydrogels with dual ionic and electronic conductivity. The conductivity of all hydrogel exceeds 10−4 S/cm. Additionally, SEM was employed to characterize the pore size of the hydrogels, revealing a decrease with higher AD content. The swelling ratio ranged between 4.89 and 6.50, indicating the tunable nature of the hydrogels' structure. Utilizing 3D printing, we produced a 2 × 2 cm2 mesh active conductive layer that ensures a more uniform stress distribution—maximum sensitivity with a grid width of 4 mm. Our assembled hydrogel sensor demonstrated long-term stability in cycling tests over 1000 cycles and proved capable of recognizing various human movements. The SF-AD hydrogel, characterized by its unique combination of properties and potential for customization, presents broad prospects for future applications in flexible electronics.

Applications of Two-dimensional Materials in Perovskite Solar Cells

As a new type of solar cell, perovskite solar cells (PSCs) exhibit significant potential due to the high performance. In recent years, they have garnered substantial attention due to their impressive photovoltaic conversion efficiency, low production costs, malleability, and other advantageous characteristics. However, there remains considerable room for the improvement in the performance of perovskite solar cells. Key factors that critically influence their performance include the charge transport layer, electrode materials, and overall cell structure. Two-dimensional (2D) materials, as emerging substances, facilitate the modifications of PSCs and enhance the electronic conduction. In this paper, a concise overview of perovskite solar cells is provided, followed by a summary of the current progress in enhancing their performance. The applications of 2D materials in the solar cell sector are highlighted. Finally, the existing challenges and issues confronting perovskite solar cells are discussed. This work will help promote the application of 2D materials in PSCs.

Simultaneously Enhanced Low Temperature Li+ Transport Kinetics and Crystal Stability of Nb1.94Mo0.06O5@C Anode Induced by Distorted NbO6 Octahedron

AbstractThe electrochemical performances of lithium‐ion batteries (LIBs) will be significantly degraded under low‐temperature conditions, which restricts their wide application in cold environments. Herein, the low‐temperature transport kinetics of a novel Nb1.94Mo0.06O5@C nanocomposite anode is accelerated greatly via engineering the microstructure and NbO6 octahedron. The detailed crystallographic features are characterized by using synchrotron radiation, spherical electron microscope, and density functional theory simulation methods. Both experimental and simulation analysis suggest that Mo6+ preferentially replaces Nb5+ in the regular octahedral location and distorts the NbO6 octahedron, resulting in a widened c‐axis spacing and a lowered ion diffusion barrier. Coupled with the enhanced electronic conductivity derived from surface carbon layer, Nb1.94Mo0.06O5@C anode exhibits an enhanced charge transfer process, improved Li+ diffusion kinetics, pronounced pseudo‐capacitance process, and excellent low temperature capacity. Furthermore, in situ X‐ray diffraction and ex situ electron microscope elucidate that the structural evolution of Nb1.94Mo0.06O5@C is highly reversible, unveiling its excellent cycling stability. The full cell assembled with LiNi0.6Co0.2Mn0.2O2 cathode demonstrates excellent practicality. This study reveals the critical role of distorting NbO6 octahedron and expanding crystal spacing in facilitating rapid Li+ diffusion and enhancing charge storage performance of Nb2O5 at low temperatures.

Enhancing Thermoelectric Performance of Mg3Sb2 Through Substitutional Doping: Sustainable Energy Solutions via First-Principles Calculations

Mg3Sb2-based materials, part of the Zintl compound family, are known for their low thermal conductivity but face challenges in thermoelectric applications due to their low energy conversion efficiency. This study addressed these limitations through first-principles calculations using the CASTEP module in Materials Studio 8.0, aiming to enhance the thermoelectric performance of Mg3Sb2 via strategic doping. Density functional theory (DFT) calculations were performed to analyze electronic properties, including band structure and density of states (D.O.S.), providing insights into the influence of various dopants. The semiclassical Boltzmann transport theory, implemented in BoltzTrap (version 1.2.5), was used to evaluate key thermoelectric properties such as the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and electronic figure of merit (eZT). The results indicate that doping significantly improved the thermoelectric properties of Mg3Sb2, facilitating a transition from p-type to n-type behavior. Bi doping reduced the band gap from 0.401 eV to 0.144 eV, increasing carrier concentration and mobility, resulting in an electrical conductivity of 1.66 × 106 S/m and an eZT of 0.757. Ge doping increased the Seebeck coefficient to −392.1 μV/K at 300 K and reduced the band gap to 0.09 eV, achieving an electronic ZT of 0.859 with low thermal conductivity (11 W/mK). Si doping enhanced stability and achieved an electrical conductivity of 1.627 × 106 S/m with an electronic thermal conductivity of 11.3 W/mK, improving thermoelectric performance. These findings established the potential of doped Mg3Sb2 as a highly efficient thermoelectric material, paving the way for future research and applications in sustainable energy solutions.