Active Material Research Articles

Preparation and hydration of low-carbon UHPC with high fraction of activated tuff and recycled fine powders

Due to the high energy consumption and carbon emission of cement, using active supplementary materials in concrete is widely studied. In this paper, waste tuff micropowder and recycled fine powder (RFP) with maximum replaced ratio of 70 % were investigated by alkali activation in ultra-high performance concrete (UHPC), the mechanical properties and hydration process were studied with different dosages and activators. The results show that the strength activity index of tuff and RFP both enhanced after calcium hydroxide activation. The alkali activator accelerated the hydration speed of tuff and RFP, also leaded to a low heat generated. The compressive strength was reduced with the replaced ratio of tuff and RFP, but the flexural strength was improved once tuff added and cured in appropriate temperature. In the cement-tuff/RFP system, calcium hydroxide accelerates cement hydration and activates part of the tuff and RFP to generate C-(A)-S-H to improve the strength of the mortar. Due to the low degree of tuff activation, less hydration products were formed, leaded to an increase in porosity. The RFP was effectively activated by calcium hydroxide, and the generated C-(A)-S-H and CaCO3 effectively refined the pore structure. The activation of RFP consumed limited mixing water, while the excessive CaCO3 generated by activation will cause the loss of UHPC strength.

Rice Straw‐Derived Biochar as Anode Material for Lithium‐Ion Battery: A Step toward Sustainable Development

In the present study, sustainable upscaling of rice straw, an agri‐residue, is explored as the way to obtain active material to prepare anode for use in lithium‐ion batteries (LIBs). The biochar having high carbon and low silica content is prepared by initial chemical treatment of rice straw followed by its pyrolysis. The pristine and modified biochar are characterized using Brunauer‐Emmett‐Teller surface area, energy dispersive X‐ray spectroscopy, carbon hydrogen nitrogen sulphur elemental analysis, scanning electron microscopy, X‐Ray power diffraction, Fourier transform infrared spectroscopy and Raman analysis and the modified biochar show an enhancement in graphitic carbon content. A coin cell is assembled using anode prepared from modified biochar. The coin cell is subjected to electrochemical testing and had a discharge capacity of 352 mA.h g−1. Further, the coin cell is tested for 100 cycles and a columbic efficiency of 99.7% was obtained. Therefore, biochar derived from pyrolysis of rice straw has the potential to be used as anode material for LIBs.

High Capacitance Based on Vacancy Defective Porous Carbon in Ionic Liquid

AbstractPorous carbons have been extensively studied in electrochemical capacitors (ECs). However, low capacitance remains a limitation due to the electrical double layer (EDL) storage mechanism when porous carbons are used in ionic liquids (ILs) based ECs. Herein, the nitrogen‐derived vacancy defects in porous carbon nanospheres are found which can boost capacitive charge storage and present reversible high capacitance of 427 F g−1 in pure IL electrolyte, equal to a normalized area capacitance (CA) of 16 µF cm−2, surpassing the theoretical EDL CA (≈11 µF cm−2). When used as capacitive cathode, the assembled Lithium hybrid capacitor express high energy density of 635 Wh kg−1 based on active material under much high‐power density of 14.5 kW kg−1. A combination of control experiments and density functional theory investigation indicate that the EC's performance improvement mostly stems from strong interactions at vacancy defects, triggering extraordinary faradaic capacitance. The results shed light on defect engineering for realizing extra faradaic capacitance of carbon materials, and open up new opportunities for improving EC's energy density.

The origins of size-dependent UV stabilities of CdZnTeS alloyed quantum dots

CdTe-based quantum dots (QDs) have been used as active materials in various applications, such as sensing, imaging, and light-harvesting devices where the QDs are continuously illuminated by suitable lights. Passivation of CdTe QDs with stable inorganic layers to form core/shell or core/multiple-shell structures has been demonstrated to improve the stabilities of QDs against illumination. However, information related to the UV stability of newly developed CdZnTeS alloyed QDs has not been fully explored yet. Herein, we synthesized CdZnTeS alloyed QDs of different sizes and compared their size-dependent stabilities under UV irradiation. Upon UV exposure the first excitonic peak of QDs blue-shifted, gradually and the relative Cd concentration decreased indicating that QDs were steadily dissolved. We found that the smaller QDs dissolved faster than the larger QDs. By correlating this with the change in the QDs' crystalline structure corroborated by X-ray diffraction studies, we demonstrated that the alloyed structure with a sulfide-rich surface enhances the stabilities of larger QDs. The size-dependent stabilities of alloyed QDs demonstrated here provide information for selecting the right QDs for specific applications.

Mass scale synthesis of graphene nanosheets using waste cardboard for application in perovskite solar cells and supercapacitors

Advanced graphene-based materials have been proficiently incorporated into next-generation solar cells and supercapacitors because of their high electrical conductivity, large surface area, excellent charge-transport ability, and exceptional optical properties. Herein, we report the synthesis of graphene nanosheets (GNs) from waste cardboard via pyrolysis, with ethyl alcohol as the growth initiator. Additionally, we demonstrated the use of GNs in energy conversion and storage applications. Using the GN electrode in perovskite solar cells resulted in an excellent power conversion efficiency of ∼10.41 % for an active area of 1 cm2, indicating an enhancement of approximately 27 % compared to conventional electrodes. Furthermore, the GNs were used as active electrode materials in supercapacitors with excellent electrochemical performance and a high gravimetric specific capacitance of 167.5 F/g at a scan rate of 2 mV/s. The developed GNs can be efficiently used for energy storage, conversion, and electrochemical sensing applications.

Investigating optical up-conversion process of erbium-doped ceria nanoparticles in photonic bilayer Bragg structure

This paper offers a thorough analysis using simulations, delving into the dual photonic impacts of using a Bragg stack in the optical upconversion (UC) process; the alteration of the local density of photon states (LDOS) and the amplification of local irradiance. We specifically investigate their influence on the upconversion quantum yield of the upconverter Er–CeO2nanoparticles (NPs). The Bragg stack being analyzed is composed of layers that alternate between TiO2 and Poly(methylmethacrylate) (PMMA), with the latter housing nanoparticles responsible for upconversion. The photonic effects are initially simulated independently and later integrated in a rate equation model to study its effect on the upconversion efficiency. This model accurately describes the kinetics associated with the upconversion (UC) processes within Er–CeO2 NPs. In order to ascertain the highest achievable upconversion efficiency across a spectrum of realistically feasible structures, adjustments are made to the refractive index of the active material within the con-fines of available materials. This work demonstrates the positive effect of photonic Bragg structure on the upconversion efficiency of Er–CeO2NPs.

In-situ growth of 3D amorphous Ni-Co-Mn phosphate on 2D Ti3C2Tx nanocomposite for commercial-level hybrid energy storage application

To overcome the limited electronic conductivity and capacity of single and binary transition metal phosphates (TMPs), highly electrochemical active materials and rational structural design of ternary TMPs composite are urgently required. In this study, we successfully synthesized an amorphous 3D Ni-Co-Mn phosphate@2D Ti3C2Tx (MXene) nanocomposite (NCMP series) through the electrodeposition method. The amorphous Ni-Co-Mn phosphate effectively restricts the self-accumulation of MXene nanosheets, resulting in the development of a porous nanostructure. This structure exposes more active sites, expands the ion transport path, and enhances the conductivity of the Ni-Co-Mn phosphate@Ti3C2Tx material. Owing to the synergistic effect offered by Ni-Co-Mn phosphate and MXene nanocomposite, the anchored Ni-Co-Mn phosphate@Ti3C2Tx (NCMP-5) electrode delivers an elevated capacity of 342 mAh/g (1230 C/g) at 5.0 A/g, surpassing the pristine Ni-Co-Mn phosphate (NCMP-4, 260 mAh/g) and MXene (33.3 mAh/g). Moreover, a hybrid solid-state supercapacitor (HSSC) device is assembled with NCMP-5 as a cathode and reduced graphene oxide (rGO) as an anode within a polymer gel (PVA-KOH) electrolyte. Notably, the fabricated HSSC device displays a supreme specific capacity of 27.5 mAh/g (99 C/g) and a high (volumetric) energy density of 22 Wh/kg (3.6 Wh/cm3) at a power density of 0.80 kW/kg (0.13 kW/cm3) for 1.0 A/g. Moreover, the HSSC device retains 95.4 % of its initial capacity even after 10,000 cycles. Importantly, the operational potential window of two serially connected HSSC devices approaches +3.2 V, enabling different colored commercial light-emitting diodes (LEDs) to be efficiently illuminated. Eventually, the remarkable supercapacitive characteristics of the 3D@2D amorphous Ni-Co-Mn phosphate@MXene nanocomposite make it an attractive choice for advanced electroactive materials in upcoming hybrid energy storage technologies.

Novel synthesis of FeF3·0.33H2O@hollow acetylene black nanosphere and its long-life electrochemical properties as a cathode for lithium-ion batteries

Iron (III) fluoride (FeF3), characterized by high voltage and high specific capacity and emerges as a promising candidate for the forthcoming generation of cathode materials in lithium-ion batteries. This study employs a novel methodology by introducing Fe3+ sources into hollow acetylene black particles through a vacuum impregnation method. This innovative approach results in the synthesis of a composite material comprising FeF3∙0.33H2O encapsulated within hollow acetylene black nanospheres, denoted as the FeF3∙0.33H2O @hollow acetylene black nanosphere composite material (FF@HCN). The composite exhibits a shell composed of highly graphitized carbon and a core containing FeF3∙0.33H2O particles in the range of 10–20 nm. The proportion of active materials is 75.56 %. The acetylene black has chain-like structure and high specific surface area, significantly enhances the material's conductivity, contributing 74.4 % to the pseudocapacitance at a scan rate of 1 mV s−1. The cavity graphite shell plays a crucial role in restricting the expansion and pulverization decay of FeF3∙0.33H2O nanoparticles, thereby markedly improving the cycle stability. The initial capacity of the FF@HCN composite is 224.4 mAh g−1, and after 1000 cycles at 0.1 C, it maintains a capacity of 162.3 mAh g−1, resulting in a capacity retention rate of 72.3 % and decay per cycle of 0.027 %.

A thermostable ionic liquid-methacrylate-based polymer electrolyte for energy storage application

In recent years, gel polymer electrolytes (GPEs) incorporating ionic liquids (ILs) have been explored extensively for lithium-ion batteries due to their favourable thermal stability and high ionic conductivity. Gel polymer electrolytes can also improve the safety of lithium-ion batteries by eliminating the flammable organic solvents which are often used in traditional electrolyte systems. Herein, we report an efficient synthesis of a thermostable ionic liquid-methacrylate-based polymer gel electrolyte via a photo-initiated phase separation (PIPS) process in an inert environment. Anionic liquid phase of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI), coupled with a low molecular weight polyethylene glycol dimethyl ether (PEGDME), was combined with a solid phase of bisphenol A ethoxylate dimethacrylate (BEMA) at varying solid to liquid ratios to produce a thermally stable gel electrolyte. The highest ionic conductivity of 1.9 × 10−3 S cm−1 (at 30 °C) was achieved for the electrolyte with a solid-to-liquid ratio of 1:3 by weight. The Lithium metal cells utilizing these electrolytes and LiFePO4 as cathode active material exhibited the initial discharge capacity of 144 mAh g−1 with capacity retention of 85 % over 100 cycles in ambient temperature. The thermal stability of the cells was significantly improved upon increasing the EMIMTFSI content. This study illustrates the potential application of the IL-methacrylate gel polymer electrolyte system in enhancing the safety of Li-ion batteries through careful tuning of the composition. Their versatile properties also make them suitable for quasi-solid-state batteries with high energy density and safety.

Evaluating Polyacrylic Acid as a Universal Aqueous Binder for Ni-Rich Cathodes NMC811 and Si Anodes in Full Cell Lithium-ion Batteries.

Silicon (Si) and silicon/graphite (Si/Gr) composite anodes are promising candidates due to their high theoretical capacity, low operating potential and natural abundance for high energy density Li-ion batteries. Green electrode production, eliminating organic volatile solvents require advancement of aqueous electrodes. Engineering the binder plays a critical role for improving waterborne electrodes. Lithium substituted polyacrylic acid LiPAA has been demonstrated as a promising binder for Si/Gr anodes and for Ni-rich cathodes in different cell configurations. LiPAA is utilized to minimize the volume expansion during cycling for Si/Gr anodes. LiPAA is formed in situ during cathode slurry preparation to regulate the pH and dimmish the Li loss. Using advanced characterization techniques, we investigated the slurries, electrodes, and active material reaction with LiPAA and its effect to the cycling performance. Our results indicate that the performance of high Si containing anode is limited by the amount of Si in the electrode. The failure mechanism with respect to high Si content was studied thoroughly. Aqueous processed cathodes with LiPAA binder in combination with Si anodes outperformed NMP based cathodes. Hence, LiPAA was successfully utilized as an active binder for both a high Si containing anode and for a Ni rich cathode.

Shock-endurable and reversible evolution between CoOOH and intermediate governed by interfacial strain for fluctuating oxygen evolution

Transition metal oxide usually suffers from reconstruction into metal oxyhydroxide during oxygen evolution reaction (OER), while irreversible evolution between metal oxyhydroxides and intermediate species cannot agilely response to the fluctuating power of renewable energy. Herein, an individual CoMoxO4 phase with a tunable Co/Mo stoichiometry is reconstructed into CoOOH skin as active material for OER. Compressive strain induced by CoMo1.14O4/CoOOH interface, downshifting the d-band center of CoOOH, is an effective strategy to not only accelerate the sluggish kinetics of OER, but also enable inspiring the expeditious evolution and the reversibility between CoOOH and intermediate species. The reversibility is an applicable demand for OER in case of fluctuating potential. Reaction current on CoMo1.14O4 at constant potential is demonstrated by the lower fluctuation of 1.7 %, relative to 13.8 % in CoMoO4 after 12 cycles. Meanwhile, an anion exchange membrane water splitting electrolyzer made of CoMo1.14O4 anode can endure current shock of 50 ∼ 800 mA cm−2 in 0.2 s, which has negligible decay at 800 mA cm−2 after 9 shocks. Designing strategy of interfacial strain modulated by stoichiometry can be universally extended into the other oxide electrocatalysts including NiMoO4 and their derivatives.

Monolithic Interphase Enables Fast Kinetics for High‐Performance Sodium‐Ion Batteries at Subzero Temperature

AbstractIn spite of the competitive performance at room temperature, the development of sodium‐ion batteries (SIBs) is still hindered by sluggish electrochemical reaction kinetics and unstable electrode/electrolyte interphase under subzero environments. Herein, a low‐concentration electrolyte, consisting of 0.5M NaPF6 dissolving in diethylene glycol dimethyl ether solvent, is proposed for SIBs working at low temperature. Such an electrolyte generates a thin, amorphous, and homogeneous cathode/electrolyte interphase at low temperature. The interphase is monolithic and rich in organic components, reducing the limitation of Na+ migration through inorganic crystals, thereby facilitating the interfacial Na+ dynamics at low temperature. Furthermore, it effectively blocks the unfavorable side reactions between active materials and electrolytes, improving the structural stability. Consequently, Na0.7Li0.03Mg0.03Ni0.27Mn0.6Ti0.07O2//Na and hard carbon//Na cells deliver a high capacity retention of 90.8 % after 900 cycles at 1C, a capacity over 310 mAh g−1 under −30 °C, respectively, showing long‐term cycling stability and great rate capability at low temperature.

Research Progress and Application of Multimodal Flexible Sensors for Electronic Skin.

In recent years, wearable electronic skin has garnered significant attention due to its broad range of applications in various fields, including personal health monitoring, human motion perception, human-computer interaction, and flexible display. The flexible multimodal sensor, as the core component of electronic skin, can mimic the multistimulus sensing ability of human skin, which is highly significant for the development of the next generation of electronic devices. This paper provides a summary of the latest advancements in multimodal sensors that possess two or more response capabilities (such as force, temperature, humidity, etc.) simultaneously. It explores the relationship between materials and multiple sensing capabilities, focusing on both active materials that are the same and different. The paper also discusses the preparation methods, device structures, and sensing properties of these sensors. Furthermore, it introduces the applications of multimodal sensors in human motion and health monitoring, as well as intelligent robots. Finally, the current limitations and future challenges of multimodal sensors will be presented.

Monolithic Interphase Enables Fast Kinetics for High-Performance Sodium-Ion Batteries at Subzero Temperature.

In spite of the competitive performance at room temperature, the development of sodium-ion batteries (SIBs) is still hindered by sluggish electrochemical reaction kinetics and unstable electrode/electrolyte interphase under subzero environments. Herein, a low-concentration electrolyte, consisting of 0.5M NaPF6 dissolving in diethylene glycol dimethyl ether solvent, is proposed for SIBs working at low temperature. Such an electrolyte generates a thin, amorphous, and homogeneous cathode/electrolyte interphase at low temperature. The interphase is monolithic and rich in organic components, reducing the limitation of Na+ migration through inorganic crystals, thereby facilitating the interfacial Na+ dynamics at low temperature. Furthermore, it effectively blocks the unfavorable side reactions between active materials and electrolytes, improving the structural stability. Consequently, Na0.7Li0.03Mg0.03Ni0.27Mn0.6Ti0.07O2//Na and hard carbon//Na cells deliver a high capacity retention of 90.8 % after 900 cycles at 1C, a capacity over 310 mAh g-1 under -30 °C, respectively, showing long-term cycling stability and great rate capability at low temperature.

Accelerating Na2S/Na2S2 conversion kinetics by electrolyte additive with high Na2S/Na2S2 solubility for high-performance room-temperature sodium–sulfur batteries

The development of room-temperature sodium sulfur batteries is severely constrained by the sluggish solid-solid conversion kinetics of Na2S/Na2S2 and the accumulation of “dead Na2S/Na2S2”. Here, we accelerate the conversion kinetics of Na2S/Na2S2 as well as reduce the accumulation of “dead Na2S/Na2S2” by 1-butyl-1-methylpyrrolidine trifluoromethanesulfonate ([P14][OTf]) ionic liquid additive that is compatible with metallic Na and has high Na2S/Na2S2 solubility. The results of three-electrode kinetics tests show a significant enhancement of the apparent redox kinetics of Na2S/Na2S2 through increasing its concentration. During battery cycling, the increase in Na2S/Na2S2 concentration can induce the formation of three-dimensional Na2S deposition and reduce the coverage of the electrode effective electroactive area, thus decreasing the battery polarization, especially at high rates. In addition, high Na2S/Na2S2 solubility can promote the reuse of “dead Na2S/Na2S2” and greatly improve the utilization of active material. At 2C rate, 351 mAh g−1 can be maintained after 800 cycles, and the capacity decay per cycle is 0.046 %. The rate and cycle performance of the battery are greatly improved. Further, a mechanism is proposed for the enhancement of battery performance via overpotential and diffusion theories.

Fe,Ni-Based Metal-Organic Frameworks Embedded in Nanoporous Nitrogen-Doped Graphene as a Highly Efficient Electrocatalyst for the Oxygen Evolution Reaction.

The quest for economically sustainable electrocatalysts to replace critical materials in anodes for the oxygen evolution reaction (OER) is a key goal in electrochemical conversion technologies, and, in this context, metal-organic frameworks (MOFs) offer great promise as alternative electroactive materials. In this study, a series of nanostructured electrocatalysts was successfully synthesized by growing tailored Ni-Fe-based MOFs on nitrogen-doped graphene, creating composite systems named MIL-NG-n. Their growth was tuned using a molecular modulator, revealing a non-trivial trend of the properties as a function of the modulator quantity. The most active material displayed an excellent OER performance characterized by a potential of 1.47 V (vs. RHE) to reach 10 mA cm-2, a low Tafel slope (42 mV dec-1), and a stability exceeding 18 h in 0.1 M KOH. This outstanding performance was attributed to the synergistic effect between the unique MOF architecture and N-doped graphene, enhancing the amount of active sites and the electron transfer. Compared to a simple mixture of MOFs and N-doped graphene or the deposition of Fe and Ni atoms on the N-doped graphene, these hybrid materials demonstrated a clearly superior OER performance.

Residual NMP and Its Impacts on Performance of Lithium-Ion Cells

Abstract N-methyl-2-pyrrolidone (NMP) is the most common solvent used in coating positive electrode materials on aluminum foil during the manufacturing of lithium-ion batteries. NMP is a strongly polar aprotic solvent that effectively dissolves the polyvinylidene difluoride binder. While the majority of NMP typically evaporates during the electrode baking process, trace amounts may persist, particularly in positive electrodes containing nano-sized and highly-porous active materials. We noted residual NMP in the positive electrodes of Li-ion pouch cells containing LiMn0.8Fe0.2PO4 due to the extremely high surface area of the material and we wanted to determine the impact of this residual NMP. Therefore, a control electrolyte was purposely spiked with varying amounts of NMP and used in NMC532/graphite pouch cells to investigate the impact of residual NMP on lithium-ion battery performance. Experimental results indicate that NMP has the potential not only to neutralize the electrolyte additive ethylene sulfate but also to independently increase cathode impedance, leading to a higher rate of capacity loss during charge-discharge cycling. It is crucial to establish the appropriate procedure for baking electrodes containing NMP, both in laboratory and industrial settings, to mitigate these effects.

Achieving a Double Advantage Through Design of TiO2/C Interlaced Coating for Si Anode

AbstractMultifunctional coating strategy shows promising prospective in advancing Si‐based anodes towards practical applications in Li‐ion batteries. Dual coating of amorphous carbon and TiO2 shows demonstrable advantages owing to high elasticity of amorphous carbon and mechanical toughness of TiO2. However, for past design of Si@C@TiO2 composite electrode, wherein C and TiO2 are configured layer‐by‐layer, a long‐standing problem exists as that a thin TiO2 coating is insufficient to stabilize the electrode's architecture while a thick one prevents the core active material of Si far from fully electrochemically utilization due to the too strong structural constraint effect. Herein, it presents that a facial heat treatment of Si@C@TiO2 with thick enough TiO2 can readily avert the problem. Such a strategy promotes the capacity utilization rate from 39% to 61% for the initial cycle and from 43% to 85% after 200 cycles. Model structure of C/TiO2 multilayer films is employed to reveal the role of the heat treatment. It finds that the heat treatment can transform a layer‐by‐layer structure of C@TiO2 into an interlaced structure of C/TiO2 which exhibits a dual advantage in withstanding mechanical strain and simultaneously promoting Li‐ion storage and electron/Li‐ion transport.

Synthesis and application of gelatin-based controlled-release antibacterial films containing oregano essential oil/β-cyclodextrin microcapsules for chilling preservation of grass carp fillets

This work aimed to synthesize oregano essential oil/β-cyclodextrin microcapsules (OEO/β-CDs) and then prepare gelatin-based controlled-release antibacterial films with different OEO/β-CDs contents (0%–2%) for chilling preservation of grass carp fillets. The results of FTIR, XRD, DSC and accelerated release ratio showed that OEO was successfully encapsulated in OEO/β-CDs and its thermal stability was effectively improved. Moreover, at 2% of addition amount of OEO/β-CDs, the tensile strength of the films increased from 14.43 MPa to 18.72 MPa. In addition, the films showed significant antibacterial activity against Pseudomonas (61.52%), Aeromonas (62.87%), and Shewanella putrefaciens (66.67%). Preservation experiments showed that the films effectively prevented the increase of TVB-N, and TBA value of the refrigerated fillets and significantly suppressed the growth of spoilage organisms, thus extending the shelf life by 2–3 days. Therefore, the synthesized film has promising potential as an active packaging material for the preservation of grass carp.

Polyphenols functionalized MOF encapsulated BPQDs for synergistic photothermal/photodynamic antibacterial properties and multifunctional food preservation

Active antibacterial materials play an important role in solving food safety problems caused by pathogen contamination. In this study, a composite active antibacterial material with the synergistic antibacterial effectiveness of photothermal, photodynamic and the surface charge of polyphenols was developed, where the multi-porous polyphenol functionalized metal–organic frameworks (ZIF-8-TA) were used as the framework carrier, and black phosphorus quantum dots (BPQDs) were used as the photosensitive source. The resulted ZIF-8-TA/PBQDs possesses excellent photothermal conversion efficiency (27.92%), photodynamic performance and surface charge, and these factors ensure the outstanding broad-spectrum antibacterial performance (100%). Multifunctional characteristics and excellent biocompatibility endow the materials with vast potential for foodstuff packaging. The results showed that the composite antibacterial film produced by doping ZIF-8-TA/PBQDs into chitosan could effectively prolong the shelf life of foodstuff compared with commercial membrane. The successful implementation of this research provides a new idea for controlling microbial contamination and developing multifunctional antibacterial materials.