The Regulating Role of Carbon Nanotubes and Graphene in Lithium-Ion and Lithium-Sulfur Batteries

Thiophilic-Lithiophilic Hierarchically Porous Membrane-Enabled Full Lithium-Sulfur Battery with a Low N/P Ratio

Lithium-sulfur batteries stand out as the next-generation batteries because of their high energy density and low cost. However, the shuttle effect of lithium polysulfides (LiPSs), growth of lithium dendrites, and overuse of lithium resources still hinder their further application. To address these problems, we constructed a porous network structure in which Sn is melted and coated on a frame that has a carbon nanotube (CNT) core and a nitrogen-doped carbon (NC) coating as cross-linking shell (CNT@NC@Sn). This hierarchically porous membrane electrode, which has an ultrahigh porosity of approximately 90%, works as a matrix to strengthen the conductivity of Li+ and electrons and provides enough space for the conversion between sulfur and LiPSs. Moreover, the in situ thin coating of Sn not only promotes the adsorption and catalytic conversion of LiPSs but also provides lithiophilic binding sites and induces uniform lithium deposition. Thus, the thiophilic-lithiophilic porous membrane electrode with lithium loaded on the frame (in the form of Sn-Li alloy) by electroplating can replace lithium sheets, reduce the use of Li, and improve the safety performance of the battery. Additionally, these dual-functional membranes boost the reaction kinetics and conductivity of the cathode by dispersing the sulfur slurry in the porous membrane framework. As a result, the lithium-sulfur full battery assembled with the CNT@NC@Sn integrated membrane electrode exhibits stable cycling with a reversible capacity of 617.1 mAh g-1 after 200 cycles at 1 C. The capacity decay rate per cycle is 0.105%, and the N/P ratio is as low as 2.98.

Graphene-based TiO2 composites for photocatalysis & environmental remediation: synthesis and progress

Photoactive nanomaterials constitute an emerging field in nanotechnology, finding an extensive array of applications spanning diverse areas, including electronics and photovoltaic devices, solar fuel cells, wastewater treatment, etc. Titanium dioxide (TiO₂), in its thin-film form, has been exhaustively surveyed as potential photocatalysts for environmental remediation owing to its innocuousness, stability, and photocatalytic characteristics when subjected to ultraviolet (UV) irradiation. However, TiO₂ has some shortcomings associated with a large bandgap value of around 3.2 eV, making it less efficient in the visible spectral range. TiO₂ is often consolidated with various carbon nanomaterials to overcome this limitation and enhance its efficiency. Graphene, a 2-dimensional allotrope of carbon with a bandgap tuned between 0 and 0.25 eV, exhibits unique properties, making it an attractive candidate to augment the photoactivity of semiconductor (SC) oxides. Encapsulating graphene oxide onto TiO₂ nanospheres demonstrates intensified photocatalytic properties and exceptional recyclability for the degeneration of certain dyes, including Rhodamine B. This review encompasses various techniques to synthesize graphene-based TiO₂ photoactive composites, emphasizing graphene capsulized hollow titania nanospheres, nanofibers, core/shell, and reduced graphene oxide-TiO₂-based nanocomposites. It also consolidates the application of the aforestated nanocomposites for the disintegration of various synthetic dyes, proving efficacious for water decontamination and degradation of chemicals and pharmaceuticals. Furthermore, graphene-based TiO₂ nanocomposites used as lithium (Li)-ion batteries manifesting substantial electrochemical performance and solar fuel cells for energy production are discussed here.

Perspectives on Iron Oxide-Based Materials with Carbon as Anodes for Li- and K-Ion Batteries

The necessity for large scale and sustainable energy storage systems is increasing. Lithium-ion batteries have been extensively utilized over the past decades for a range of applications including electronic devices and electric vehicles due to their distinguishing characteristics. Nevertheless, their massive deployment can be questionable due to use of critical materials as well as limited lithium resources and growing costs of extraction. One of the emerging alternative candidates is potassium-ion battery technology due to potassium’s extensive reserves along with its physical and chemical properties similar to lithium. The challenge to develop anode materials with good rate capability, stability and high safety yet remains. Iron oxides are potentially promising anodes for both battery systems due to their high theoretical capacity, low cost and abundant reserves, which aligns with the targets of large-scale application and limited environmental footprint. However, they present relevant limitations such as low electronic conductivity, significant volume changes and inadequate energy efficiency. In this review, we discuss some recent design strategies of iron oxide-based materials for both electrochemical systems and highlight the relationships of their structure performance in nanostructured anodes. Finally, we outline challenges and opportunities for these materials for possible development of KIBs as a complementary technology to LIBs.

Electrochemical Performance of Carbon-Rich Silicon Carbonitride Ceramic as Support for Sulfur Cathode in Lithium Sulfur Battery

As a promising matrix material for anchoring sulfur in the cathode for lithium-sulfur (Li-S) batteries, porous conducting supports have gained much attention. In this work, sulfur-containing C-rich SiCN composites are processed from silicon carbonitride (SiCN) ceramics, synthesized at temperatures from 800 to 1100 °C. To embed sulfur in the porous SiCN matrix, an easy and scalable procedure, denoted as melting-diffusion method, is applied. Accordingly, sulfur is infiltrated under solvothermal conditions at 155 °C into pores of carbon-rich silicon carbonitride (C-rich SiCN). The impact of the initial porosity and microstructure of the SiCN ceramics on the electrochemical performance of the synthesized SiCN-sulfur (SiCN-S) composites is analysed and discussed. A combination of the mesoporous character of SiCN and presence of a disordered free carbon phase makes the electrochemical performance of the SiCN matrix obtained at 900 °C superior to that of SiCN synthesized at lower and higher temperatures. A capacity value of more than 195 mAh/g over 50 cycles at a high sulfur content of 66 wt.% is achieved.

Ultrastable Interfacial Contacts Enabling Unimpeded Charge Transfer and Ion Diffusion in Flexible Lithium-Ion Batteries

Deteriorating interfacial contact under mechanical deformation induces large cracks and high charge transfer resistance, resulting in a severe capacity fading of flexible lithium-ion batteries (LIBs). Herein, an oxygen plasma treatment on a polymer separator combined with high-speed centrifugal spraying to construct ultrastable interfacial contacts is reported. With the treatment, abundant hydrophilic oxygen-containing functional groups are produced and ensure strong chemical adhesion between the separator and the active materials. With single walled carbon nanotubes (SWCNTs) sprayed onto the active materials, a dense thin film is formed as the current collector. Meanwhile, the centrifugal force caused by high-speed rotation together with van der Waals forces under fast evaporation produces a much closer interface between the current collector and the active materials. As a result of this ultrastable interfacial interaction, the integrated electrode shows no structural failure after 5000 bending cycles with the charge-transfer resistance as low as 35.8% and a Li-ion diffusion coefficient nearly 19 times of the untreated electrode. Flexible LIBs assembled with these integrated electrodes show excellent structural and electrochemical stability, and can work steadily under various deformed states and repeated bending. This work provides a new technique toward rational design of electrode configuration for flexible LIBs.

Sodiophilic Mg2+ -Decorated Ti3 C2 MXene for Dendrite-Free Sodium Metal Batteries with Carbonate-Based Electrolytes

The advantages of sodium metal, such as abundant resources, low cost, high capacity, and high working potential, make it a promising metal anode. Unfortunately, the hazardous dendrite growth of sodium metal is one of the major hindrances for the practical application of sodium metal batteries (SMBs). By applying multifunctional Mg(II)@Ti₃ C₂ MXene as the protective layer for commercial Cu foil, the wettability of the electrolyte on the current collector is dramatically improved with the suppression of sodium dendrites. Moreover, the first-principles calculations prove that the surface of Mg(0001) is able to establish a connection with Na(111) growth, with Mg acting as the nucleation seed for sodium. The experimental results indicate that even when a high areal capacity of sodium (2 mAh cm^-2 ) is deposited, no sodium dendrite is observed. Electrochemical tests, including symmetric cells, Na||Cu asymmetric cells, and full cells, prove the sodiophilic character of Mg²⁺ -decorated Ti₃ C₂ MXene. The results may also create a new pathway for developing other dendrite-free metal anodes, such as Li/K/Zn/Ca/Mg.

Two Birds with One Stone: Interfacial Engineering of Multifunctional Janus Separator for Lithium-Sulfur Batteries

Li-dendrite growth and unsatisfactory sulfur cathode performance are two core problems that restrict the practical applications of lithium-sulfur batteries (LSBs). Here, an all-in-one design concept for a Janus separator, enabled by the interfacial engineering strategy, is proposed to improve the performance of LSBs. At the interface of the anode/separator, the thin functionalized composite layer contains high-elastic-modulus and high-thermal-conductivity boron nitride nanosheets and oxygen-group-grafted cellulose nanofibers (BNNs@CNFs), by which the formation of "hot spots" can be effectively avoid, the Li-ion flux homogenized, and dendrite growth suppressed. Meanwhile, at the interface between the separator and the cathode, the homogenously exposed single-atom Ru on the surface of reduced graphene oxide (rGO@Ru SAs) can "trap" polysulfides and reduce the activation energy to boost their conversion kinetics. Consequently, the LSBs show a high capacity of 460 mAh g^-1 at 5C and ultrastable cycling performance with an ultralow capacity decay rate of 0.046% per cycle over 800 cycles. To further demonstrate the practical prospect of the Janus separator, a lithium-sulfur pouch cell using the Janus separator delivers a cell-level energy density of 310.2 Wh kg^-1 . This study provides a promising strategy to simultaneously tackle the challenges facing the Li anode and the sulfur cathode in LSBs.

Concept Review of a Cloud-Based Smart Battery Management System for Lithium-Ion Batteries: Feasibility, Logistics, and Functionality

Energy storage plays an important role in the adoption of renewable energy to help solve climate change problems. Lithium-ion batteries (LIBs) are an excellent solution for energy storage due to their properties. In order to ensure the safety and efficient operation of LIB systems, battery management systems (BMSs) are required. The current design and functionality of BMSs suffer from a few critical drawbacks including low computational capability and limited data storage. Recently, there has been some effort in researching and developing smart BMSs utilizing the cloud platform. A cloud-based BMS would be able to solve the problems of computational capability and data storage in the current BMSs. It would also lead to more accurate and reliable battery algorithms and allow the development of other complex BMS functions. This study reviews the concept and design of cloud-based smart BMSs and provides some perspectives on their functionality and usability as well as their benefits for future battery applications. The potential division between the local and cloud functions of smart BMSs is also discussed. Cloud-based smart BMSs are expected to improve the reliability and overall performance of LIB systems, contributing to the mass adoption of renewable energy.

Module-Designed Carbon-Coated Separators for High-Loading, High-Sulfur-Utilization Cathodes in Lithium-Sulfur Batteries

Lithium–sulfur batteries have great potential as next-generation energy-storage devices because of their high theoretical charge-storage capacity and the low cost of the sulfur cathode. To accelerate the development of lithium–sulfur technology, it is necessary to address the intrinsic material and extrinsic technological challenges brought about by the insulating active solid-state materials and the soluble active liquid-state materials. Herein, we report a systematic investigation of module-designed carbon-coated separators, where the carbon coating layer on the polypropylene membrane decreases the irreversible loss of dissolved polysulfides and increases the reaction kinetics of the high-loading sulfur cathode. Eight different conductive carbon coatings were considered to investigate how the materials’ characteristics contribute to the lithium–sulfur cell’s cathode performance. The cell with a nonporous-carbon-coated separator delivered an optimized peak capacity of 1112 mA∙h g⁻¹ at a cycling rate of C/10 and retained a high reversible capacity of 710 mA∙h g⁻¹ after 200 cycles under lean-electrolyte conditions. Moreover, we demonstrate the practical high specific capacity of the cathode and its commercial potential, achieving high sulfur loading and content of 4.0 mg cm⁻² and 70 wt%, respectively, and attaining high areal and gravimetric capacities of 4.45 mA∙h cm⁻² and 778 mA∙h g⁻¹, respectively.

Structural and Surfacial Modification of Carbon Nanofoam as an Interlayer for Electrochemically Stable Lithium-Sulfur Cells

Electrochemical lithium-sulfur batteries engage the attention of researchers due to their high-capacity sulfur cathodes, which meet the increasing energy-density needs of next-generation energy-storage systems. We present here the design, modification, and investigation of a carbon nanofoam as the interlayer in a lithium-sulfur cell to enable its high-loading sulfur cathode to attain high electrochemical utilization, efficiency, and stability. The carbon-nanofoam interlayer features a porous and tortuous carbon network that accelerates the charge transfer while decelerating the polysulfide diffusion. The improved cell demonstrates a high electrochemical utilization of over 80% and an enhanced stability of 200 cycles. With such a high-performance cell configuration, we investigate how the battery chemistry is affected by an additional polysulfide-trapping MoS2 layer and an additional electron-transferring graphene layer on the interlayer. Our results confirm that the cell-configuration modification brings major benefits to the development of a high-loading sulfur cathode for excellent electrochemical performances. We further demonstrate a high-loading cathode with the carbon-nanofoam interlayer, which attains a high sulfur loading of 8 mg cm-2, an excellent areal capacity of 8.7 mAh cm-2, and a superior energy density of 18.7 mWh cm-2 at a low electrolyte-to-sulfur ratio of 10 µL mg-1.

Semi-Immobilized Molecular Electrocatalysts for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries constitute promising next-generation energy storage devices due to the ultrahigh theoretical energy density of 2600 Wh kg^-1. However, the multiphase sulfur redox reactions with sophisticated homogeneous and heterogeneous electrochemical processes are sluggish in kinetics, thus requiring targeted and high-efficient electrocatalysts. Herein, a semi-immobilized molecular electrocatalyst is designed to tailor the characters of the sulfur redox reactions in working Li-S batteries. Specifically, porphyrin active sites are covalently grafted onto conductive and flexible polypyrrole linkers on graphene current collectors. The electrocatalyst with the semi-immobilized active sites exhibits homogeneous and heterogeneous functions simultaneously, performing enhanced redox kinetics and a regulated phase transition mode. The efficiency of the semi-immobilizing strategy is further verified in practical Li-S batteries that realize superior rate performances and long lifespan as well as a 343 Wh kg^-1 high-energy-density Li-S pouch cell. This contribution not only proposes an efficient semi-immobilizing electrocatalyst design strategy to promote the Li-S battery performances but also inspires electrocatalyst development facing analogous multiphase electrochemical energy processes.

Building a Bridge for Carbon Nanotubes from Nanoscale Structure to Macroscopic Application

Through 30 years of research, researchers have gained a deep understanding of the synthesis, characteristics, and applications of carbon nanotubes (CNTs). However, up to now, there are still few industries using CNT as the leading material. The difficulty of CNTs to be applied in industry is the gap between the properties of CNT-based aggregates and those of a single carbon nanotube. Therefore, how to maintain the intrinsic properties of CNTs when they are assembled into aggregates is of great significance. Herein, we summarize and analyze the research status of CNT materials applied in different fields from proven techniques to potential industries, including energy storage, electronics, mechanical and other applications. For each application, the intrinsic properties of CNTs and the real performances of their aggregates are compared to figure out the key problems in CNT synthesis. Finally, we give an outlook for building a bridge for CNTs from nanoscale structure to macroscopic application, giving inspiration to researchers making efforts toward the real application of carbon nanotubes.

Toward High-Performance Lithium-Sulfur Batteries: Efficient Anchoring and Catalytic Conversion of Polysulfides Using P-Doped Carbon Foam

Rational design of the sulfur cathode structure enables effective adsorption of polysulfides and accelerates the sulfur reduction reaction, which is of great significance to the practical application of lithium-sulfur batteries. Here, P-doped carbon foam (PCF) as a sulfur host for the lithium-sulfur battery cathode was successfully synthesized by a facile strategy. The tailored hierarchical pore structure combined with P doping not only facilitates Li⁺ diffusion but also enhances the adsorption and accelerates the catalytic conversion of lithium polysulfides, thus significantly improving lithium storage performance of the PCF/S cathode.

Microscale Silicon-Based Anodes: Fundamental Understanding and Industrial Prospects for Practical High-Energy Lithium-Ion Batteries

To accelerate the commercial implementation of high-energy batteries, recent research thrusts have turned to the practicality of Si-based electrodes. Although numerous nanostructured Si-based materials with exceptional performance have been reported in the past 20 years, the practical development of high-energy Si-based batteries has been beset by the bias between industrial application with gravimetrical energy shortages and scientific research with volumetric limits. In this context, the microscale design of Si-based anodes with densified microstructure has been deemed as an impactful solution to tackle these critical issues. However, their large-scale application is plagued by inadequate cycling stability. In this review, we present the challenges in Si-based materials design and draw a realistic picture regarding practical electrode engineering. Critical appraisals of recent advances in microscale design of stable Si-based materials are presented, including interfacial tailoring of Si microscale electrode, surface modification of SiO_x microscale electrode, and structural engineering of hierarchical microscale electrode. Thereafter, other practical metrics beyond active material are also explored, such as robust binder design, electrolyte exploration, prelithiation technology, and thick-electrode engineering. Finally, we provide a roadmap starting with material design and ending with the remaining challenges and integrated improvement strategies toward Si-based full cells.

A Powerful One-Step Puffing Carbonization Method for Construction of Versatile Carbon Composites with High-Efficiency Energy Storage

Carbon materials play a critical role in the advancement of electrochemical energy storage and conversion. Currently, it is still a great challenge to fabricate versatile carbon-based composites with controlled morphology, adjustable dimension, and tunable composition by a one-step synthesis process. In this work, a powerful one-step maltose-based puffing carbonization technology is reported to construct multiscale carbon-based composites on large scale. A quantity of composite examples (e.g., carbon/metal oxides, carbon/metal nitrides, carbon/metal carbides, carbon/metal sulfides, carbon/metals, metal/semiconductors, carbon/carbons) are prepared and demonstrated with required properties. These well-designed composites show advantages of large porosity, hierarchical porous structure, high conductivity, tunable components, and proportion. The formation mechanism of versatile carbon composites is attributed to the puffing-carbonization of maltose plus in situ carbothermal reaction between maltose and precursors. As a representative example, Li₂ S is in situ implanted into a hierarchical porous cross-linked puffed carbon (CPC) matrix to verify its application in lithium-sulfur batteries. The designed S-doped CPC/Li₂ S cathode shows superior electrochemical performance with higher rate capacity (621 mAh g^-1 at 2 C), smaller polarization and enhanced long-term cycles as compared to other counterparts. The research provides a general way for the construction of multifunctional component-adjustable carbon composites for advanced energy storage and conversion.

Advanced Current Collectors with Carbon Nanofoams for Electrochemically Stable Lithium-Sulfur Cells

An inexpensive sulfur cathode with the highest possible charge storage capacity is attractive for the design of lithium-ion batteries with a high energy density and low cost. To promote existing lithium–sulfur battery technologies in the current energy storage market, it is critical to increase the electrochemical stability of the conversion-type sulfur cathode. Here, we present the adoption of a carbon nanofoam as an advanced current collector for the lithium–sulfur battery cathode. The carbon nanofoam has a conductive and tortuous network, which improves the conductivity of the sulfur cathode and reduces the loss of active material. The carbon nanofoam cathode thus enables the development of a high-loading sulfur cathode (4.8 mg cm⁻²) with a high discharge capacity that approaches 500 mA·h g⁻¹ at the C/10 rate and an excellent cycle stability that achieves 90% capacity retention over 100 cycles. After adopting such an optimal cathode configuration, we superficially coat the carbon nanofoam with graphene and molybdenum disulfide (MoS₂) to amplify the fast charge transfer and strong polysulfide-trapping capabilities, respectively. The highest charge storage capacity realized by the graphene-coated carbon nanofoam is 672 mA·h g⁻¹ at the C/10 rate. The MoS₂-coated carbon nanofoam features high electrochemical utilization attaining the high discharge capacity of 633 mA·h g⁻¹ at the C/10 rate and stable cyclability featuring a capacity retention approaching 90%.

Future directions of material chemistry and energy chemistry

Energy is an important substantial foundation for the survival and development of humans. However, the over-consumption of resources and environmental pollution have become more prominent. The key factors for solving energy problems are to increase energy utilization efficiency and optimize energy structure. The development of new materials is the research emphasis in the field of material chemistry all the time. For instance, developing new light-capture materials and catalysts to improve the efficiency of existing photovoltaic cells is one of the most effective approaches to increasing solar power capacity radically. The design of high-performance catalytic materials to make better use of energy from fossil fuels and biomass. In addition, it is an important research direction of material chemistry and energy chemistry to deeply understand the reaction mechanism of energy conversion.

Restraining polysulfide shuttling by designing a dual adsorption structure of bismuth encapsulated into carbon nanotube cavity

The shuttle effect derived from the dissolution of lithium polysulfides (LIPs) seriously hinders commercialization of lithium-sulfur (Li-S) batteries. Hence, we skillfully designed 1D cowpea-like CNTs@Bi composites with a double adsorption structure, where the bismuth nanoparticles/nanorods are encapsulated in the cavities of CNTs, avoiding the aggregation of bismuth nanoparticles during cycling and improving the conductivity of the electrode. Meanwhile, the sulfur was evenly distributed on the surface of bismuth nanoparticles/nanorods, ensuring effective catalytic activity and displaying high sulfur loading. Under the synergetic effects of the physical detention of abundant pores and chemical adsorption of bismuth, LIPs can be minimised, effectively curbing the shuttle effect. Benefiting from the above advantages, the CNTs@Bi/S cathodes exhibit a high capacity of 1352 mA h g-1, long cycling lifespan (708 mA h g-1 after 200 cycles at 1 C) and excellent coulombic efficiency. As the anodes of lithium-ion batteries (LIBs), the CNTs@Bi composites also show excellent performance due to the encapsulated structure to accommodate the serious volume change. This work offers an innovative strategy for improving the performances of the Li-S batteries and LIBs.

Nanoporosity of Carbon-Sulfur Nanocomposites toward the Lithium-Sulfur Battery Electrochemistry

An ideal high-loading carbon–sulfur nanocomposite would enable high-energy-density lithium–sulfur batteries to show high electrochemical utilization, stability, and rate capability. Therefore, in this paper, we investigate the effects of the nanoporosity of various porous conductive carbon substrates (e.g., nonporous, microporous, micro/mesoporous, and macroporous carbons) on the electrochemical characteristics and cell performances of the resulting high-loading carbon–sulfur composite cathodes. The comparison analysis of this work demonstrates the importance of having high microporosity in the sulfur cathode substrate. The high-loading microporous carbon–sulfur cathode attains a high sulfur loading of 4 mg cm⁻² and sulfur content of 80 wt% at a low electrolyte-to-sulfur ratio of 10 µL mg⁻¹. The lithium–sulfur cell with the microporous carbon–sulfur cathode demonstrates excellent electrochemical performances, attaining a high discharge capacity approaching 1100 mA∙h g⁻¹, a high-capacity retention of 75% after 100 cycles, and superior high-rate capability of C/20–C/3 with excellent reversibility.

All-Graphitic Multilaminate Mesoporous Membranes by Interlayer-Confined Molecular Assembly

Layered mesostructured graphene, which combines the intrinsic advantages of planar graphene and mesoporous materials, has become interestingly important for energy storage and conversion applications. Here, an interlayer-confined molecular assembly method is presented for constructing all-graphitic multilaminate membranes (MMG⊂rGO), which are composed of monolayer mesoporous graphene (MMG) sandwiched between reduced graphene oxide (rGO) sheets. Hybrid assembly of iron-oleate complexes and organically modified GO sheets enables the preferential assembly of iron-oleate precursors at the interlayer space of densely stacked GO, driven by the like-pair molecular van der Waals interactions. Confined pyrolysis of iron-oleate complexes at GO interlayers leads to close-packed, carbon-coated Fe₃ O₄ nanocrystal arrays, which serve as intermediates to template the subsequent formation of MMG⊂rGO membranes. To demonstrate their application potentials, MMG⊂rGO membranes are exploited as dual-functional interlayers to boost the performance of Li-S batteries by concurrently suppressing the shuttle of polysulfides and the growth of Li dendrites. This work showcases the capability of molecular-based hybrid assembly for synthesizing multilayer mesostructured graphene with high packing density and its use in electrochemical energy applications.

Dual carbon-confined Sb2Se3 nanoparticles with pseudocapacitive properties for high-performance lithium-ion half/full batteries

Transition metal selenides have attracted enormous research attention as anodes for lithium-ion batteries (LIBs) due to their high theoretical specific capacities. Nevertheless, the low electronic conductivity and dramatic volume variation in electrochemical reaction processes result in rapid capacity fading and poor rate capability. Herein, a metal-organic framework is used as a template to in situ synthesize Sb₂Se₃ nanoparticles encapsulated in N-doped carbon nanotubes (N-CNTs) grafted on reduced graphene oxide (rGO) nanosheets. The synergistic effects of N-doped carbon nanotubes and reduced graphene oxide nanosheets are beneficial for providing good electrical conductivity and maintaining the structural stability of electrode materials, leading to stable cycling performance and superior rate performance. Kinetic analysis suggests that the electrochemical reaction kinetics is dominated by pseudocapacitive contribution. Notably, a high discharge capacity of 451.1 mA h g^-1 at a current density of 2.0 A g^-1 is delivered after 450 cycles. Even at a high current density of 10.0 A g^-1, a discharge capacity of 192.6 mA h g^-1 is maintained after 10 000 cycles. When coupled with a commercial LiFePO₄ cathode, the full batteries show an excellent discharge specific capacity of 534.5 mA h g^-1 at 0.2 A g^-1. This work provides an effective strategy for constructing high-performance anodes for Li⁺ storage.

Applications of Carbon in Rechargeable Electrochemical Power Sources: A Review

Rechargeable power sources are an essential element of large-scale energy systems based on renewable energy sources. One of the major challenges in rechargeable battery research is the development of electrode materials with good performance and low cost. Carbon-based materials have a wide range of properties, high electrical conductivity, and overall stability during cycling, making them suitable materials for batteries, including stationary and large-scale systems. This review summarizes the latest progress on materials based on elemental carbon for modern rechargeable electrochemical power sources, such as commonly used lead–acid and lithium-ion batteries. Use of carbon in promising technologies (lithium–sulfur, sodium-ion batteries, and supercapacitors) is also described. Carbon is a key element leading to more efficient energy storage in these power sources. The applications, modifications, possible bio-sources, and basic properties of carbon materials, as well as recent developments, are described in detail. Carbon materials presented in the review include nanomaterials (e.g., nanotubes, graphene) and composite materials with metals and their compounds.

MXene-Derived Tin O2 n- 1 Quantum Dots Distributed on Porous Carbon Nanosheets for Stable and Long-Life Li-S Batteries: Enhanced Polysulfide Mediation via Defect Engineering

The application of Li-S batteries has been hindered by the shuttling behavior and sluggish reaction kinetics of polysulfides. Here an effective polysulfide immobilizer and catalytic promoter is developed by proposing oxygen-vacancy-rich Ti_n O_{2 n -1} quantum dots (OV-T_n QDs) decorated on porous carbon nanosheets (PCN), which are modulated using Ti₃ C₂ T_x MXene as starting materials. The T_n QDs not only confine polysulfides through strong chemisorption but also promote polysulfide conversion via redox-active catalysis. The introduction of oxygen vacancies further boosts the immobilization and conversion of polysulfides by lowering the adsorption energy and shortening the bond lengths. The PCN provides a physical polysulfide confinement as well as a flexible substrate preventing OV-T_n QDs from aggregation. Moreover, the two building blocks are conductive, thereby effectively improving the electron/charge transfer. Finally, the ultrasmall size of QDs along with the porous structure endows OV-T_n QDs@PCN with large specific surface area and pore volume, affording adequate space for S loading and volume expansion. Therefore, the OV-T_n QDs@PCN/S delivers a high S loading (79.1 wt%), good rate capability (672 mA h g^-1 at 2 C), and excellent long-term cyclability (88% capacity retention over 1000 cycles at 2 C). It also exhibits good Li⁺ storage under high S-mass loading and lean electrolyte.

Flexible FeS@Fe2O3/CNT composite films as self-supporting anodes for high-performance lithium-ion batteries

The transition metal sulfides/oxides have been considered as promising anode materials for lithium ion batteries due to their high theoretical capacities but have suffered limits from the unsatisfactory electronic conductivity and limited lifespan. Here, FeS micro-flowers are synthesized by hydrothermal treatment and are wared and grafted into layer-by-layer carbon nanotubes (CNT). Subsequently, FeS@Fe₂O₃/CNT composite films are obtained by annealing, during which the FeS micro-flowers are partially oxidized to core-shell FeS@Fe₂O₃micro-flowers. The FeS@Fe₂O₃/CNT composite electrodes exhibited high reversible capacity of 1722.4 mAh g^-1(at a current density of 0.2 A g^-1after 100 cycles) and excellent cycling stability (545.1 mAh g^-1at a current density of 2 A g^-1after 600 cycles) as self-supporting anodes. The prominent electrochemical performances are attributed to the unique reciprocal overlap architecture. This structure serves as a cushion to buffer large volume expansion during discharge/charge cycles, and ameliorates electrical conductivity. Due to their good specific capacity and cycle stability, these FeS@Fe₂O₃/CNT films have high potential application value to be used as high-performance anodes for lithium-ion, lithium sulfur and flexible packaging batteries.

Graphene-Based Nanomaterials as the Cathode for Lithium-Sulfur Batteries

The global energy crisis and environmental problems are becoming increasingly serious. It is now urgent to vigorously develop an efficient energy storage system. Lithium-sulfur batteries (LSBs) are considered to be one of the most promising candidates for next-generation energy storage systems due to their high energy density. Sulfur is abundant on Earth, low-cost, and environmentally friendly, which is consistent with the characteristics of new clean energy. Although LSBs possess numerous advantages, they still suffer from numerous problems such as the dissolution and diffusion of sulfur intermediate products during the discharge process, the expansion of the electrode volume, and so on, which severely limit their further development. Graphene is a two-dimensional crystal material with a single atomic layer thickness and honeycomb bonding structure formed by sp2 hybridization of carbon atoms. Since its discovery in 2004, graphene has attracted worldwide attention due to its excellent physical and chemical properties. Herein, this review summarizes the latest developments in graphene frameworks, heteroatom-modified graphene, and graphene composite frameworks in sulfur cathodes. Moreover, the challenges and future development of graphene-based sulfur cathodes are also discussed.

Ultra-fast and facile preparation of uniform sulfur/graphene composites with microwave for lithium-sulfur batteries

Lithium-sulfur batteries are one of the most promising energy storage systems due to their high energy density. Many efforts have been made to improve the electrochemical performance of lithium-sulfur batteries. However, the complex and time-consuming preparation process hinders their practical application. In this work, an ultra-fast and facile method has been proposed to prepare the sulfur/graphene composites in a simplified and time-saving preparation process with the assistance of microwave. Microwave is introduced to help sulfur fleetly deposit uniformly on the surface of graphene within just 30 s. Nano-sized sulfur within 30 nm is generated in this ultra-fast process. Lithium-sulfur batteries with as-prepared sulfur/graphene composites exhibit good cycling life with a capacity of 503.5 mAh g^-1at 0.2 C. This method makes it possible for lithium-sulfur batteries to be practical.

Hierarchical Micro-Nanoclusters of Bimetallic Layered Hydroxide Polyhedrons as Advanced Sulfur Reservoir for High-Performance Lithium-Sulfur Batteries

Rational construction of sulfur electrodes is essential in pursuit of practically viable lithium-sulfur (Li-S) batteries. Herein, bimetallic NiCo-layered double hydroxide (NiCo-LDH) with a unique hierarchical micro-nano architecture is developed as an advanced sulfur reservoir for Li-S batteries. Compared with the monometallic Co-layered double hydroxide (Co-LDH) counterpart, the bimetallic configuration realizes much enriched, miniaturized, and vertically aligned LDH nanosheets assembled in hollow polyhedral nanoarchitecture, which geometrically benefits the interface exposure for host-guest interactions. Beyond that, the introduction of secondary metal intensifies the chemical interactions between layered double hydroxide (LDH) and sulfur species, which implements strong sulfur immobilization and catalyzation for rapid and durable sulfur electrochemistry. Furthermore, the favorable NiCo-LDH is architecturally upgraded into closely packed micro-nano clusters with facilitated long-range electron/ion conduction and robust structural integrity. Due to these attributes, the corresponding Li-S cells realize excellent cyclability over 800 cycles with a minimum capacity fading of 0.04% per cycle and good rate capability up to 2 C. Moreover, highly reversible areal capacity of 4.3 mAh cm-2 can be achieved under a raised sulfur loading of 5.5 mg cm-2. This work provides not only an effective architectural design but also a deepened understanding on bimetallic LDH sulfur reservoir for high-performance Li-S batteries.

Evolution of low-dimensional material-based field-effect transistors

Field-effect transistors (FETs) have tremendous applications in the electronics industry due to their outstanding features such as small size, easy fabrication, compatibility with integrated electronics, high sensitivity, rapid detection and easy measuring procedures. However, to meet the increasing demand of the electronics industry, efficient FETs with controlled short channel effects, enhanced surface stability, reduced size, and superior performances based on low-dimensional materials are desirable. In this review, we present the developmental roadmap of FETs from conventional to miniaturized devices and highlight their prospective applications in the field of optoelectronic devices. Initially, a detailed study of the general importance of bulk and low-dimensional materials is presented. Then, recent advances in low-dimensional material heterostructures, classification of FETs, and the applications of low-dimensional materials in field-effect transistors and photodetectors are presented in detail. In addition, we also describe current issues in low-dimensional material-based FETs and propose potential approaches to address these issues, which are crucial for developing electronic and optoelectronic devices. This review will provide guidelines for low-dimensional material-based FETs with high performance and advanced applications in the future.

Coaxial spinning fabricated high nitrogen-doped porous carbon walnut anchored on carbon fibers as anodic material with boosted lithium storage performance

Commercial graphite with low theoretical capacity cannot meet the ever-increasing requirement demands of lithium-ion batteries (LIBs) caused by the rapid development of electric devices. Rationally designed carbon-based nanomaterials can provide a wide range of possibilities to meet the growing requirements of energy storage. Hence, the porous walnut anchored on carbon fibers with reasonable pore structure, N-self doping (10.2 at%) and novel structure and morphology is designed via interaction of inner layer polyethylene oxide and outer layer polyacrylonitrile and polyvinylpyrrolidone during pyrolysis of the obtained precursor, which is fabricated by coaxial electrospinning. As an electrode material, the as-made sample shows a high discharge capacity of 965.3 mA h g^-1 at 0.2 A g^-1 in the first cycle, retains a capacity of 819.7 mA h g^-1 after 500 cycles, and displays excellent cycling stability (475.2 mA h g^-1 at 1 A g^-1 after 1000 cycles). Moreover, the capacity of the electrode material still keeps 260.5 mA h g^-1 at 5 A g^-1 after 1000 cycles. Therefore, the obtained sample has a bright application prospect as a high performance anode material for LIBs. Besides, this design idea paves the way for situ N-enriched carbon material with novel structure and morphology by coaxial electrospinning.

Graphene Coating Obtained in a Cold-Wall CVD Process on the Co-Cr Alloy (L-605) for Medical Applications

Graphene coating on the cobalt-chromium alloy was optimized and successfully carried out by a cold-wall chemical vapor deposition (CW-CVD) method. A uniform layer of graphene for a large area of the Co-Cr alloy (discs of 10 mm diameter) was confirmed by Raman mapping coated area and analyzing specific G and 2D bands; in particular, the intensity ratio and the number of layers were calculated. The effect of the CW-CVD process on the microstructure and the morphology of the Co-Cr surface was investigated by scanning X-ray photoelectron microscope (SPEM), atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Nanoindentation and scratch tests were performed to determine mechanical properties of Co-Cr disks. The results of microbiological tests indicate that the studied Co-Cr alloys covered with a graphene layer did not show a pro-coagulant effect. The obtained results confirm the possibility of using the developed coating method in medical applications, in particular in the field of cardiovascular diseases.

Nitrogen and boron doped carbon layer coated multiwall carbon nanotubes as high performance anode materials for lithium ion batteries

Lithium ion batteries (LIBs) are at present widely used as energy storage and conversion device in our daily life. However, due to the limited power density, the application of LIBs is still restricted in some areas such as commercial vehicles or heavy-duty trucks. An effective strategy to solve this problem is to increase energy density through the development of battery materials. At the same time, a stable long cycling battery is a great demand of environmental protection and industry. Herein we present our new materials, nitrogen and boron doped carbon layer coated multiwall carbon nanotubes (NBC@MWCNTs), which can be used as anodes for LIBs. The electrochemical results demonstrate that the designed NBC@MWCNTs electrode possesses high stable capacity over an ultra-long cycling lifespan (5000 cycles) and superior rate capability even at very high current density (67.5 A g⁻¹). Such impressive lithium storage properties could be ascribed to the synergistic coupling effect of the distinctive structural features, the reduced diffusion length of lithium ions, more active sites generated by doped atoms for lithium storage, as well as the enhancement of the electrode structural integrity. Taken together, these results indicate that the N, B-doped carbon@MWCNTs materials may have great potential for applications in next-generation high performance rechargeable batteries.

Li2 S-Based Li-Ion Sulfur Batteries: Progress and Prospects

The great demand for high-energy-density batteries has driven intensive research on the Li-S battery due to its high theoretical energy density. Consequently, considerable progress in Li-S batteries is achieved, although the lithium anode material is still challenging in terms of lithium dendrites and its unstable interface with electrolyte, impeding the practical application of the Li-S battery. Li₂ S-based Li-ion sulfur batteries (LISBs), which employ lithium-metal-free anodes, are a convenient and effective way to avoid the use of lithium metal for the realization of practical Li-S batteries. Over the past decade, studies on LISBs are carried out to optimize their performance. Herein, the research progress and challenges of LISBs are reviewed. Several important aspects of LISBs, including their working principle, the physicochemical properties of Li₂ S, Li₂ S cathode material composites, LISBs full batteries, and electrolyte for Li₂ S cathode, are extensively discussed. In particular, the activation barrier in the initial charge process is fundamentally analyzed and the mechanism is discussed in detail, based on previous reports. Finally, perspectives on the future direction of the research of LISBs are proposed.

Regulating the carbon distribution of anode materials in lithium-ion batteries

The exploration of electrode materials is considered to be a crucial process affecting the development of lithium-ion batteries. However, the large-scale commercial application of the great mass of anode materials has been hampered by the challenges with conductivity and volume change. These problems can be solved by the combination of a carbon-matrix with anode materials, which has proven to be an effective strategy. This review aims to outline recent advances in carbon-matrix composite anodes based on different dimensions (0D, 1D, 2D, 3D and atomic scale) and functions, with the emphasis on the regulation of carbon distribution of composite anodes. Besides, the matrix forms and carbon sources have also been summarized. This review will provide some light on the future carbon-matrix electrode design trends for LIBs.

Carbon nanotubes assembled on porous TiO2 matrix doped with Co3O4 as sulfur host for lithium-sulfur batteries

Advanced design and fabrication of high performance sulfur cathodes with improved conductivity and chemical adsorption towards lithium polysulfides (LiPS) are crucial for further development of Li-S batteries. Hence, we designed a TiO₂/Co₃O₄-CNTs composite derived from Ti-MOF (MIL-125) as the host matrix for sulfur cathode. The polar nature of metal oxides (TiO₂, Co₃O₄) creates the adsorptive sites in the composite and leads to an efficient chemical capture of LiPS. The CNTs ensure the contact between S/Li₂S and the host material with high conductivity, enhanced charge transfer and fast electrochemical kinetics. At the same time, the CNTs strengthen the stability of the electrode material. Consequently, the as-prepared TiO₂/Co₃O₄-CNTs composite showed excellent electrochemical performance. The cell with S-TiO₂/Co₃O₄-CNTs delivers an initial specific capacity of 1270 mAh g^-1 at 0.2 C and high rate performance with a capacity of 603 mAh g^-1 at 3 C.

Sulfur nanoparticles/Ti3C2Tx MXene with an optimum sulfur content as a cathode for highly stable lithium-sulfur batteries

Lithium-sulfur batteries have a high theoretical energy density but they need better sulfur host materials to retain the lithium polysulfide shuttle effect, which results in the batteries' capacity fading. Titanium carbide MXene (Ti3C2Tx MXene) is an excellent host for the sulfur cathode because of its layered-stacked structure and many surface termination groups. The sulfur content in S/Ti3C2Tx MXene composites is an important factor affecting the cathodes' electrochemical performance. In this work, S/Ti3C2Tx MXene composites with different sulfur contents are prepared by a one-step hydrothermal process, and the influence of the sulfur content in the S/Ti3C2Tx MXene composite on the S/Ti3C2Tx MXene cathode's electrochemical performance is studied. When the mass ratio of sulfur to MXene in the reactant is 4 : 1, the sulfur nanoparticles are uniformly filled in the layered-stacked structure. The layered-stacked structure can buffer the volume expansion of sulfur during cycling and the surface termination groups exhibit strong adsorption of LiPSn. Thus, the S/MXene composite with an optimum sulfur content (67.0 wt%) demonstrates an excellent electrochemical performance, including a high initial reversible capacity (1277 mA h g-1 at 0.5 C) and the best cycling performance (1059 mA h g-1 at 0.5 C after 100 cycles). This work offers a guide to developing advanced S-based cathode materials with an appropriate S content for lithium sulfur batteries.

Hierarchical structure TiNb2O7 microspheres derived from titanate for high-performance lithium-ion batteries

Hierarchical structure TiNb₂O₇ microspheres derived from titanate displayed satisfactory long-term cycling stability and prominent rate capability for lithium-ion batteries.

Gold-carbonaceous materials based heterostructures for gas sensing applications

The carbon nanostructures such as carbon nanotubes and graphene decorated with gold nanoparticles exhibit promising gas sensing applications with enhanced sensitivity.

Recent Advancements of N-Doped Graphene for Rechargeable Batteries: A Review

Graphene, a 2D carbon structure, due to its unique materials characteristics for energy storage applications has grasped the considerable attention of scientists. The highlighted properties of this material with a mechanically robust and highly conductive nature have opened new opportunities for different energy storage systems such as Li-S (lithium-sulfur), Li-ion batteries, and metal-air batteries. It is necessary to understand the intrinsic properties of graphene materials to widen its large-scale applications in energy storage systems. In this review, different routes of graphene synthesis were investigated using chemical, thermal, plasma, and other methods along with their advantages and disadvantages. Apart from this, the applications of N-doped graphene in energy storage devices were discussed.

Precise Synthesis of Fe-N2 Sites with High Activity and Stability for Long-Life Lithium-Sulfur Batteries

Precisely tuning the coordination environment of the metal center and further maximizing the activity of transition metal-nitrogen carbon (M-NC) catalysts for high-performance lithium-sulfur batteries are greatly desired. Herein, we construct an Fe-NC material with uniform and stable Fe-N₂ coordination structure. The theoretical and experimental results indicate that the unsaturated Fe-N₂ center can act as a multifunctional site for anchoring lithium polysulfides (LiPSs), accelerating the redox conversion of LiPSs and reducing the reaction energy barrier of Li₂S decomposition. Consequently, the batteries based on a porous carbon nitride supported Fe-N₂ site (Fe-N₂/CN) host exhibit excellent cycling performance with a capacity decay of 0.011% per cycle at 2 C after 2000 cycles. This work deepens the understanding of the relationship between electronic structure of M-NC sites and the catalysis effect for the conversion of LiPSs. This strategy also provides a potent guidance for the further application of M-NC materials in advanced lithium-sulfur batteries.

Theoretical Insights into the Favorable Functionalized Ti2C-Based MXenes for Lithium-Sulfur Batteries

Because of the high specific surface area, excellent electronic conductivity, facile Li diffusion, and rich functional groups, Ti₂C-based MXenes have been widely used to improve the electrochemical property of lithium-sulfur batteries. The complex surface functionalization (such as -OH, -S, -F, and -O) of MXenes boosts the performance but also causes controversies about the favorable functionalized surface in the electrochemical reaction during the charge and discharge process. In the present work, a theoretical study based on density functional theory has been carried out to clarify the favorable functionalized surface by comparing pristine Ti₂C and -OH-, -S-, -F-, and -O-functionalized Ti₂C surfaces from the aspects of adsorption ability, electronic conductivity, and kinetic conversion ability. It is found that compared with severe polysulfide deformation on pristine Ti₂C and Ti₂C(OH)₂ surfaces, Ti₂CO₂, Ti₂CS₂, and Ti₂CF₂ have effective polysulfide adsorption. Ti₂CO₂ has the largest surface adsorption energy, followed by Ti₂CS₂, and Ti₂CF₂ is the weakest. Meanwhile, the narrow-band gap semiconductor property of Ti₂CO₂ during adsorption indicates worse electronic conductivity than metallic Ti₂CS₂ and Ti₂CF₂. In addition, for the kinetic conversion ability, the Ti₂CS₂ surface has the fastest polysulfide conversion and Li diffusion, followed by Ti₂CF₂, and Ti₂CO₂ represents the slowest conversion and diffusion. Accordingly, because of the medium binding energy, good electronic conductivity, and fast polysulfide conversion and Li diffusion, Ti₂CS₂ is revealed to be the favorable functionalized surface. More importantly, the origin for the Ti₂CS₂ surface with medium adsorption ability represents the fastest polysulfide conversion, and Li diffusion is further clarified. The great affinity of the Ti₂CS₂ surface to the product Li₂S leads to facile polysulfide conversion. The uniform charge distribution on the Ti₂CS₂ surface contributes to the fast Li diffusion.

Superior Anchoring of Sodium Polysulfides to the Polar C2N 2D Material: A Potential Electrode Enhancer in Sodium-Sulfur Batteries

Despite the high theoretical specific energy in rechargeable sodium-sulfur batteries, the shuttle effect severely hampers its capacity and reversibility, which could be overcome by introducing an anchoring material. We, herein, use first-principles calculations to study the low-cost, easily synthesized, environmentally friendly, and stable two-dimensional polar nitrogenated holey graphene (C₂N) and nonpolar polyaniline (C₃N) to investigate their performance as anchoring materials and the mechanism behind the binding to identify the best candidate to improve the performance of sodium-sulfur batteries. We gain insight into the interaction, including the lowest-energy configurations, binding energies, binding nature, charge transfer, and electronic properties. Sodium primarily contributes to binding with the nanosheets, which is in accordance with their characteristics as anchoring materials. Sodium polysulfides (NaPSs) and the S₈ cluster adsorb at the pores of C₂N, where there are six electron lone pairs, one for each N atom. The polar C₂N binds the NaPSs much strongly than the nonpolar C₃N. In contrast to C₃N, the charge population substantially modifies by adsorbing NaPSs on C₂N, with a substantial charge transfer from the sulfur atoms. The calculated work function of 6.04 eV for pristine C₂N, comparable with the previously reported values, decreases on adsorption of the NaPSs formed from battery discharging. We suggest that the inclusion of C₂N into sulfur electrodes could also improve their issue with poor conductivity.

Carbon Microtube Textile with MoS2 Nanosheets Grown on Both Outer and Inner Walls as Multifunctional Interlayer for Lithium-Sulfur Batteries

The shuttle effect of soluble lithium polysulfides during the charge/discharge process is the key bottleneck hindering the practical application of lithium-sulfur batteries. Herein, a multifunctional interlayer is developed by growing metallic molybdenum disulfide nanosheets on both outer and inner walls of cotton cloth derived carbon microtube textile (MoS2@CMT). The hollow structure of CMT provides channels to favor electrolyte penetration, Li+ diffusion and restrains polysulfides via physical confinement. The hydrophilic and conductive 1T-MoS2 nanosheets facilitate chemisorption and kinetic behavior of polysulfides. The synergic effect of 1T-MoS2 nanosheets and CMT affords the MoS2@CMT interlayer with an efficient trapping-diffusion-conversion ability toward polysulfides. Therefore, the cell with the MoS2@CMT interlayer exhibits enhanced cycling life (765 mAh g-1 after 500 cycles at 0.5 C) and rate performance (974 mAh g-1 at 2 C and 740 mAh g-1 at 5 C). This study presents a pathway to develop low-cost multifunctional interlayers for advanced lithium-sulfur batteries.

Susceptibility Factors in Chronic Lung Inflammatory Responses to Engineered Nanomaterials

Engineered nanomaterials (ENMs) are products of the emerging nanotechnology industry and many different types of ENMs have been shown to cause chronic inflammation in the lungs of rodents after inhalation exposure, suggesting a risk to human health. Due to the increasing demand and use of ENMs in a variety of products, a careful evaluation of the risks to human health is urgently needed. An assessment of the immunotoxicity of ENMs should consider susceptibility factors including sex, pre-existing diseases, deficiency of specific genes encoding proteins involved in the innate or adaptive immune response, and co-exposures to other chemicals. This review will address evidence from experimental animal models that highlights some important issues of susceptibility to chronic lung inflammation and systemic immune dysfunction after pulmonary exposure to ENMs.