## 留言板

Ordered and disordered carbons have been commonly used as coating materials for silicon (Si) anodes, however the effect of carbons with different crystallinities and pore structures on their electrochemical performance remains controversial. We used pitch and phenolic resin (PR) as the precursors of ordered and disordered carbon, respectively, to prepare carbon-coated silicon (Si@C) with strictly controlled carbon contents and surface functional groups. Their electrochemical behavior was investigated. An ordered crystalline structure is favorable for electron transport, and mesopores and macropores are conducive to the diffusion of lithium ions. Such a coating with a small pore volume is an excellent buffer for the expansion of Si, and the electrode maintains structural integrity for 50 cycles. A disordered porous structure is less robust and produces a large polarization, which produces continuous volume expansion with cycling and leads to inferior electrochemical performance. As a result, the capacity and capacity retention after 100 cycles at 0.5 A g−1 of Si@C-Pitch are respectively 8 times and 1.9 times those of Si@C-PR. This study provides theoretical guidance for the selection of carbon materials used in Si@C anodes.

Hard carbon is considered the most promising anode material for sodium-ion batteries, but its volume change during sodiation/desodiation limits its cycle life. Hard carbon microspheres (HCSs) with no binder were composited with a MXene film to form an electrode and its sodium storage properties were studied. The microspheres were prepared using Shanxi aged vinegar as a liquid carbon source. Two-dimensional Ti3C2Tx MXene (T is a functional group) was used as a multifunctional conductive binder to fabricate the flexible electrodes. Remarkably, because of the three-dimensional conductive network, the HCS/Ti3C2Tx film electrode has a high capacity of 346 mAh g−1, excellent rate performance and outstanding cycling stability over 1 000 cycles. This remarkable electrochemical performance indicates that the flexible film is a very promising anode for next-generation sodium-ion batteries.

Three dimensional (3D) printing is a modern technology in the 4th engineering revolution that has the possibility to transform existing production methods. It offers a novel production method of layered manufacturing and layer-by-layer stacking based on the forming principle, which radically simplifies the manufacturing process and enables large-scale customizable production. However, there are still numerous issues with this new technology. Except pure graphene, sp2 carbons can be 3D printed with little difficulty because of their hydrophilicity. The hydrophobic nature of pure graphene makes it difficult to print and process in water-based media. Thanks to the advancement of capillary inks, which allow for the 3D printing of pure graphene. The current review focuses on the most recent developments in 3D printing of sp2 carbons. A concise overview of 3D printing technologies is presented, followed by a summary of 3D printed sp2 carbons and their diverse applications. Finally, perspectives and opportunities for this new field are discussed.

Graphene oxide (GO) obtained by the Hummers method from coal-based graphite was composited with TiO2 by hydrothermal and wet mixing methods to obtain (H-rGO)/TiO2 and M-TiO2/rGO composites, respectively, which were used as catalysts for photocatalytic degradation of rhodamine B (Rh B) and methyl orange (MO). Compared with the M-TiO2/GO and M-TiO2/rGO composites, the TiO2 nanoparticles in H-TiO2/rGO were more uniformly decorated on both sides of rGO sheets, forming a stacked-sheet structure while apparent aggregation of TiO2 nanoparticles was found in both M-TiO2/GO and M-TiO2/rGO. H-rGO@TiO2 had the highest catalytic activity towards degradation of Rh B and MO under visible light irradiation among the three, where the incorporation of rGO into TiO2 helps to narrow the band gap of TiO2, inhibits the recombination rate of electron–hole pairs and provides conductive networks for electron transfer.

In the context of sustainable development, tackling the severe solid waste pollutions has become extremely urgent. Herein, the solid waste gangue was used to synthesize the ceramic-based microwave absorbing composites decorated with Co particles by a novel synthesis method, where the magnetic Co particles were uniformly loaded in the ceramic matrix by pelletizing gangue accompanied by spraying a solution containing Co2+, followed by in-situ carbothermal reduction using the fixed carbon in gangue as the reduction agent. The Co contents in ceramic composites are precisely controlled by adjusting the Co2+ concentration in the solutions. The fixed carbon in gangue is partially consumed and there are residue carbons in the composites, which have more defects as compared with that in gangue and play an important role as an dielectric constitute. Compared with gangue, the optimized composite exhibits excellent microwave absorbing properties with the minimum reflection loss value of −48.2 dB and the effective absorbing band of 4.3 GHz under a coating thickness of 1.5 mm. which is mainly attributed to the enhanced magnetic loss and multiple interface polarization in the composite. Such use of gangue in this work can effectively realize the resource utilization and production of low-cost and light-weight of microwave absorbing materials.

Using CO2 as a renewable carbon source for the production of high-value-added fuels and chemicals has drawn global attention lately. Photoelectrocatalytic (PEC) CO2 reduction (CO2RR) is one of the most realistic and attractive way, which can be realized effectively under sunlight illumination at low overpotential. Here, oxygen-incorporated carbon nitride (CNs) porous nanosheets were synthesized, which were used as photoanodes with Bi2CuO4 as the photocathode to realize the PEC CO2 reduction to formate. The electrical conductivity and the photoelectric response of CNs were tailored by changing the oxygen source. The oxygen obtained from the oxygen-containing precursor could improve the conductivity due to the more negative electronegativity. The oxygen obtained from the calcination atmosphere has lower photoelectric response due to the energy band structure. Under the optimal conditions, the CN has a photocurrent density of 587 μA cm−2 and an activity of PEC CO2 reduction to formate of 273.56 µmol cm−2 h−1, which is nearly 19 times higher than that of the conventional sample. Moreover, the optimal CN sample shows excellent stability with the photocurrent kept constant for 24 h. This work provides a new avenue to achieve catalysts efficient for PEC CO2 reduction to formate, which may be expanded to different PEC reactions using different cathode catalysts.ode catalysts.

With the rapid development of electric vehicles and large-scale power grids, lithium-ion batteries inevitably face the dilemma in that the limited energy density and high cost fail to meet the growing demand. Room temperature sodium-sulfur (RT Na-S) batteries, which have the potential to replace lithium-ion batteries, have become the focus of attention. However, the challenging problem of poor cycling performance arising from “shuttle effect” of the reaction intermediates (sodium polysulfides) needs to be addressed. We report a method to incorporate TiO2 nano particles into multichannels of electrospun carbon fibers (TiO2@MCCFs) to stabilize sulfur compounds to produce high-performance RT Na-S batteries. The TiO2@MCCFs were prepared by electrospinning followed by heat treatment, which were infiltrated by molten sulfur to fabricate S/TiO2@MCCF cathode materials. The addition of TiO2 nanoparticles enhances the affinity to polysulfides and promotes the conversion of polysulfides to lower order products, which was verified by DFT calculations. The S/TiO2@MCCF cathode with a S content of 54% has improved electrochemical performance with a specific capacity of 445.1 mAh g−1 after 100 cycles at 0.1 A g−1 and a nearly 100% Coulombic efficiency. Even at 2 A g−1, the cathode still exhibits a capacity of 300.5 mAh g−1 after 500 cycles, demonstrating excellent rate and cycling performance. This work provides a new way to construct high performance RT Na-S battery cathodes.

Biomorphic hard carbons have attracted widely interest as anode materials for potassium ion batteries (PIBs) recently owing to their high reversible capacity. But, the high preparation cost and poor cycle stability significantly hinder their practical applications. In this study, coconut shell-derived hard carbon (CSHCs) were prepared from waste biomass coconut shell using a one-step carbonization method, which were used as anode materials for potassium ion batteries. The effects of the carbonization temperature on the microstructures and electrochemical properties of the CSHCs were investigated by X-ray diffraction, nitrogen adsorption, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and cyclic voltammetry, etc. Results indicate that the CSHC carbonized at 1 000 °C (CSHC-10) possesses a suitable graphite microcrystalline size, pore structure and surface defect content, which exhibits the best electrochemical performance. Specifically, it presents a high reversible specific capacity of 254 mAh·g−1 at 30 mA·g−1 with an initial Coulombic efficiency of 75.0%, and the capacity retention rates are 87.5% after 100 cycles and 75.9% after 400 cycles at 100 mA·g−1, demonstrating its excellent potassium storage performance.

Carbon fiber reinforced epoxy resin composites (CFRCs) have been used in automotive and aerospace fields due to their excellent mechanical properties. The recycling of CFRCs attracts attention worldwide in recent years. Chemical recycling is a more promising method, which can selectively destroy the specific bond of resin to achieve controllable degradation. Matrix epoxy resins are degraded into monomers or oligomers, and high-value carbon fibers can be recycled. Therefore, we focus on summarizing the progress of chemical recovery method, mainly including super- and subercritical fluids, oxidation, solvolysis, alcoholysis, electrochemical recycling and so on. In addition, the insertion of reversible chemical bonds into the resin to prepare recyclable resins is beneficial for recyling and reuse of components in CFRCs. Therefore, we also briefly introduce the synthesis and depolymerization mechanism of recyclable thermosetting resins. Finally, the possible development directions of chemical recovery of CFRCs and preparation of high-performance recyclable epoxy resins are proposed.

In this work, graphites with various microstructures were prepared by cost-effective anthracite and industrial silicon powder as precursor and catalyst, respectively. The mechanism of catalytic reaction and the electrochemical properties of the as-prepared coal-based graphite as lithium anode were investigated. The correlation between structure and properties of graphite was discussed. The results demonstrate that the as-obtained sample with 5% silicon catalyst (G-2800-5%) exhibits the best overall lithium storage performance. In detail, G-2800-5% displays the best graphite structure with graphitization degree of 91.5%. As anode materials, a high reversible capacity of 369.0 mAh g−1 can be achieved at 0.1 A g−1. Meanwhile, the reversible capacity of 209.0 mAh g−1 can be obtained at the current density of 1 A g−1. It also delivers good cyclic stability with the retention rate of 92.2% after 200 cycles at 0.2 A g−1. The highly developed graphite structure, which is favorable to the formation of stable SEI and reduces lithium ion loss should be responsible for the superior electrochemical performance.

Capacitive deionization (CDI) has rapidly become a promising approach for water desalination. The technique removes salt from water through applying an electric potential between two porous electrodes to cause adsorption of charged species on the electrode surfaces. The nature of CDI favors the use of nanostructured porous carbon materials with high specific surface area and appropriate surface functional groups. Electrospun carbon nanofibers (CNFs) are quite ideal as they have high specific surface area and surface characteristics for doping/grafting with electroactive agents. Compared with powdered materials, CNF electrodes are free-standing and don’t require binders that increase resistivity. Hierarchically structured CNFs with an appropriate distribution of mesopores and micropores have better desalination performance. Compositing CNFs with faradaic materials enhances ion storage by additional pseudocapacitance besides the electric double layer capacitance. Herein, the use of electrospun CNFs as electrodes for CDI is summarized with emphasis on the major precursor materials used and structure modification, and their relations to the performance in salt electrosorption.

Tailor-made fabrication of sulfur host is very effective for solving the main challenges of lithium-sulfur (Li-S) batteries, such as the shuttle effect and sluggish redox kinetics, due to that sulfur host as a reactor for redox reactions determines the electrochemical properties of the sulfur cathode. Under this guidance, sulfur is in-situ confined in a hollow thin-walled C/Mo2C reactor with size smaller than 7 nm, in which these nanosized primary particles are connected each other to form secondary microsized particles. In such composites, the nanoscale sulfur core and continuous conductive network can facilitate lithium-ion and electron transport. Moreover, the microporous C/Mo2C shell can mitigate the outward diffusion of polysulfides via the physical/chemical obstruction and enhance redox kinetics by effectively catalytic conversion of polysulfides. Stem from these merits, the S@C/Mo2C cathode materials can achieve a high reversible capacity of 1210 mA h g−1 at 0.5 C with a low capacity fading rate of 0.127% per cycle over 300 cycles and high rate performance (780 mA h g−1 at 3.0 C). The present work may shed light on designing advanced sulfur host for Li-S batteries with high rate performance and high cycle stability.

An anodized carbon fiber tow is sized continuously. The effects of aqueous polyurethane as the sizing agent for enhancing the interfacial properties of carbon fiber reinforced polyurethane composite is investigated based on interlaminar shear strength (ILSS), elemental and functional group analysis, thermal gravimetric analysis and differential scanning calorimetry. The results show the polyurethane as the sizing agent of carbon fiber can significantly improve the interfacial properties of the composites. The ILSS of the sized carbon fiber reinforced composite is increased by 17.5%, from 39.5 MPa to 46.4 MPa compared with that the oxidized carbon fiber reinforced. Treating the sized carbon fiber reinforced composite at 170 °C can further increase the ILSS by 9.5%, to 50.8 MPa. It is considered the sizing agent can form chemical binding with the oxygen-contained functional groups on the oxidized carbon fiber surface and form hydrogen bonds with the matrix resin. After heat treatment at 170 °C, the blocking groups in the sizing agent are unblocked to reveal the isocyanate roots that react with the carbamate of the matrix to form allophanate. It can be concluded that the polyurethane sizing agent is suitable for improving the interface performance of carbon fiber reinforced polyurethane resin composites. Unsealing the sizing agent at high temperature treatment after curing can further improve the interface performance of the composite.

Mesophase pitch-based carbon fibers (MPCFs) have the characteristics of high modulus, low resistivity and high thermal conductivity, so it has broad application prospects in many fields. High-performance carbon fibers were prepared from naphthalene-based mesophase pitches synthesized by HF/BF3 catalytic one-step method (AR-MP) and AlCl3 catalytic two-step method (N-MP), respectively. These two mesophase pitches, and spun pitch fibers, pre-oxidized fibers carbonized fibers and graphitized fibers produced from them were characterized by TG-MS, FT-IR, 13 C-NMR, MALDI-TOF-MS, XRD, SEM and elemental analysis. The molecular structures and properties of mesophase pitches prepared by different catalytic polymerization processes were compared, and the effects of molecular structure differences of mesophase pitches on the structure and properties of carbon fibers were further explored. In comparison to N-MP, AR-MP possesses a rod-like semi-rigid molecular configuration containing more naphthenic structures and methyl side chains. The pre-oxidized fibers derived from AR-MP show better carbon layer orientation, thus their graphitized fibers have higher thermal conductivity of 716 W/m·K. N-MP with higher aromaticity possesses a disc-like rigid molecular configuration. Therefore, the graphitized fibers prepared from N-MP have higher tensile strength of 3.47 GPa due to their fewer resulted defects during the preparation. The molecular structures of AR-MP and N-MP have an obvious influence on the structure and properties of their graphited fibers.

As a key material in nuclear reactors, nuclear graphite is affected by the high-flux irradiation in the reactor, and its irradiation behavior is an important factor for the reactor operation. In order to understand the irradiation behavior of nuclear graphite, IG-110 nuclear graphite, as a representative of nuclear graphite, was chosen to study the evolution of morphology and microstructure caused by 7 MeV Xe26+ irradiation. The topography and microstructure changes of IG-110 were characterized by scanning electron microscopy, atomic force microscopy, grazing incidence X-ray diffraction, Raman spectroscopy and nano-indentation, respectively. The ridge-like structure on the surface of the IG-110 graphite, mainly the binder region, and the roughness increases slowly. As the irradiation damage dose increases, the ridge-like structure also appears in the filler region. The shrinkage of pores increases and its distribution is discrete. The roughness also increases rapidly as the pores close. The changes in topography and microstructure of IG-110 graphite caused by irradiation are attributed to the expansion of graphite along the C-axis direction. Defect density and the degree of in-plane disorder in the graphitic structure increases with the increase of irradiation damage dose. The mechanical properties of IG-110 graphite increase with increasing neutron fluence due to dislocation pinning and a closure of the fine pores. At higher irradiation dose, the mechanical properties reduce, which is attributed to the generation of internal porosity or amorphous structure.

The phenolic resin was coated on the surface of nano-Si by microencapsulation technology, and then carbonized under the Ar protection to prepare nano-Si@C nanocomposite. Firstly, four mass ratios of phenolic resin to nano-Si (1∶2, 1∶4, 1∶6, 1∶8) were employed to prepare nano-Si@C nanocomposites. The obtained average thickness of amorphous carbon coating was 7, 4.5, 3.7, 2.8 nm, respectively. By comparing the cycling and rate capability, the best electrochemical performance was obtained when the mass ratio of phenolic resin to nano Si was 1∶4, that is, the amorphous carbon coating was 4.5 nm.. The electrochemical properties of optimized nano-Si@C nanocomposite was then evaluated comprehensively, which exhibited excellent electrochemical performance as anode material for Li-ion batteries. Under a current density of 100 mAg−1, the nano-Si@C nanocomposite delivered a first discharge specific capacity of 2382 mAhg−1, first charge specific capacity of 1667 mAhg−1, and a first coulombic efficiency of 70%. Moreover, the discharge specific capacity of 835.6 mAhg−1 could be retained after 200 cycles with a high coulombic efficiency of 99.2%. In addition, nano-Si@C nanocomposite also demonstrated superior rate performance. Under the current densities of 100, 200, 500, 1000 and 2000 mAg−1, the average discharge specific capacities were 1716.4, 1231.6, 911.7, 676.1, and 339.8 mAhg−1, respectively. When the current density returned to 100 mAg−1, the specific capacity restored to 1326.4 mAhg−1.

The present manuscript reports a coal-based fluorescent CDs which fabricated at room temperature through a friendly method with mixture of hydrogen peroxide (H2O2) and formic acid (HCOOH) as an oxidant instead of concentrated acid (HNO3 or H2SO4). The prepared CDs show the excitation dependent behavior with high QY approximately 7.2%. The as-made CDs are water soluble, robust photo-stability, good resistance to salt solution, insensitive to pH in a range of 2.0-12.0. The coal-based CDs served as a very sensitive nano-probe for the turn-off sensing of Fe3+ ion with a minimum LOD as low as 600 nM in a dynamic range 2 to 100 μM. This efficient, rapid synthesis of coal-based CDs will not only increase high value-added utilization of coal, but also have potential application value in sensing and several another analytical applications.

In this study, a novel pantograph carbon slider (PCS) was designed by incorporating a sulfonated graphene (SG). This enhanced the mechanical and wear performances of the slider. The PCS was prepared through mold pressing, hot extrusion and roasting. A mock current-carrying wear test showed that the wear rate of the PCS reinforced by 1 wt % SG was lower by 50.0% in the normal environment and 51.0% in the rainy weather environment, compared with the control group. In addition, the flexural strength of samples with SG was higher by 41.8% compared to those without SG. Moreover, the dragging effect of SG decreased that number of random cracks and increased the compactness of fracture surface of slider materials. These changes markedly inhibited the electro-erosion of the PCS, thus improving mechanical and wear resistance significantly.

The development of high-performance electromagnetic wave absorbing materials (EWAMs) posed a prospective way to solve electromagnetic wave radiation issues in both military and civil fields. The desirable EWAMs feature strong absorption intensity, broad bandwidth, lightweight, thin thicknesses as well as other exceptional properties such as oxygen resistance, wear resistance, high-temperature resistance and high strength. In these regards, carbon-based materials, including carbon nanostructures and carbonaceous composites have become the significant participants of EWAMs, standing out for their unique structures and properties compared with the other absorption materials. In this review, we summarized the recent inspiring achievements in carbon-based EWAMs involving different dimensional (0D, 1D, 2D and 3D) carbon nanostructures and various types of carbonaceous composites (binary dielectric-carbon composite, binary magnetic-carbon composite and heterogeneous composite). Firstly, the influential factors affecting the electromagnetic microwave absorption (EWA) performances involving conductivity $\sigma$, permittivity $\varepsilon$and permeability $\mu$ were discussed based on the EWA mechanisms. Secondly, the representative reports and corresponding mechanisms about improving the EWA performance of carbon-based EWAMs were highlighted and analyzed in detail such as self-modification and composite structure construction. Finally, the current modification strategies and research prospects of carbon-based EWAMs were summarized and outlined.

Metal-nitrogen carbon catalysts have received great attention in the field of gas-involving electrocatalysis due to their high activity, large specific surface area and efficient gas diffusion pathways. Carbon nanofibers embedded with iron-nitrogen active sites were synthesized through an electrospinning approach followed by high-temperature treatment. We found that the introduction of g-C3N4 can enhance the anchoring of iron-nitrogen sites in the nanofiber, thus avoiding the formation of inorganic nanoparticles during high-temperature annealing. Compare with Fe3C/CNFs prepared without g-C3N4, Fe/CNFs showed an outstanding 4e oxygen reduction reaction (ORR) activity in both alkaline and acidic media. Furthermore, as air electrodes in Zn-air batteries, Fe/CNFs catalyst exhibit excellent performance with an open-circuit voltage of up to 1.49 V, a power density of 146 mW cm−2 and a specific capacity of 703 mAh gZn−1.This work proposes an effective strategy to prepare metal-nitrogen-carbon catalysts for energy-related electrocatalytic applications.

Interfacial adhesion between carbon fiber (CF) and polyetherketoneketone (PEKK) is the key factor to affect the mechanical performances of their composites, and thus it is very critical to impregnate PEKK into CF bundles as efficiently as possible. Here we report that owing to the high dissolubility, PEKK can be introduced onto CF surfaces via a wet strategy. The excellent wettability of PEKK guarantees a full covering and tight binding on CFs, making it possible to evaluate the interfacial shear strength (IFSS) with the microdroplet method. Furthermore, the interior of CF bundles can be completely and uniformly filled with PEKK by the solution impregnation, leading to a high interlaminar shear strength (ILSS). The maximum IFSS and ILSS can reach 107.8 and 99.3 MPa, respectively. Such superior shear properties are ascribed to the amorphous PEKK confined in the limited spacing between CFs.

In the paper, Ni/NiO nanoparticles coated with a conductive carbon layer were synthesized by hydrothermal method. They were subjected to mild gradient calcination in argon, followed by partial oxidation in oxygen. Unique 3D consecutive electron conductive network as well as synergetic effect of Ni, NiO, carbon layer and graphene sheets can effectively alleviate a large volume expansion, which can restrain the electrode crushing and aggregation, and improve the conductivity. Moreover, Ni nanoparticles can reversibly decompose Li2O during delithiation procedure, which remarkably increases the reversible capacity of Ni/NiO@C/GN anodes. Thanks to these advantages, the Ni/NiO@C/GN hybrid material has better lithium-ion storage performance than Ni/NiO/C. Compared with the initial cycle (711.6 mA h g−1), the reversible capacity of 772.1 mA h g−1 can be maintained after 300 repetitions. The property assessment enables Ni/NiO@C/GN materials to be used in the next generation of large-capacity, high-rate, stable and environmentally friendly lithium-ion batteries.

Polyether ether ketone (PEEK) has favorable mechanical properties. However, its high melt viscosity limits its applications because it is hard to process. In this study, PEEK nanocomposites modified with carbon nanotubes (CNTs) and polyether imide (PEI) were prepared using a direct wet powder blending method. The melt viscosity of the nanocomposites decreased by approximately 50%. Under optimal conditions, the addition of CNTs and PEI resulted in a synergistic increase in the toughness of the nanocomposites. The elongation at break increased by 129%, and the fracture energy increased by 97%. The uniformly dispersed CNTs/PEI powder reduces the processing difficulty of PEEK nanocomposites without affecting the heat resistance. The nanocomposites prepared by this method have lower melt viscosity. This improvement of the properties of PEEK would facilitate its use in the preparation of thermoplastic composites by powder impregnation or laser sintering technology.

Hollow-shaped porous carbon fiber for Li-S batteries electrodes is prepared by KOH activation using polyacrylonitrile (PAN) as the precursor. The obtained porous carbon fiber has a high specific surface area of 2491 m2·g−1 and a large pore volume of 1.22 cm3·g−1. And it exhibits an initial specific capacity of 330 mAh·g−1 at current density of 1 C. To further improve electrochemical performance, the fiber precursor is modified using hydrazine hydrate to prepare nitrogen doped hollow-shaped porous carbon fiber. The modified fiber shows a specific surface area of 1690 m2·g−1, a pore volume of 0.84 cm3·g−1 and a high nitrogen content of 8.81 at%. Since nitrogen doping can increase the polarity and adsorption capacity, the initial specific capacity of the nitrogen doped porous carbon fiber can be increased to 420 mAh·g−1 at current density of 1 C.

Carbon-based oxygen reduction reaction (ORR) catalysts are considered a potential substitution for the expensive platinum-based ORR catalysts in the aspect of energy conversion. Recently, metal and nitrogen codoped carbon materials (M-N-C) formed by transition metals and nitrogen-doped carbon materials have attracted much attention from researchers due to their low cost and excellent activity. Herein, a cobalt- and nitrogen-codoped porous carbon material (Co-N@CNT-C800) is prepared via a simple one-step pyrolysis method by well-designed carambola-shaped MOFs (ZIF-8@ZIF-67). The obtained Co-N@CNT-C800 consists of many carbon nanotubes (CNTs) with substantial Co doping and N doping. A large surface area (428 m2·g−1) and a favorable three-dimensional structure are also observed. The obtained Co-N@CNT-C800 exhibits excellent performance in half-wave potential and limited current density in alkaline media with a value of 0.841 V and 5.07 mA·cm−2, respectively. In addition, Co-N@CNT-C800 also shows excellent electrochemical stability and methanol tolerance compared with commercial Pt/C materials. The proposed strategy inspires a effective way to fabricate low cost and high activity electrocatalysts used for energy conversion.

An innovative and efficient preparation method of mesocarbon microbeads (MCMBs) was developed based on the dripping behavior and rheological theory of pitch during the melt-spinning process, named as the delayed capillary breakup (DCB) method. In this work, the MCMBs were prepared by the DCB method with different receiving solvents (water or tetrahydrofuran (THF)), and their microstructure evolutions were compared systematically. Moreover, the MCMBs were further activated with KOH at 750 °C or graphitized at 2800 °C to prepare the A-MCMBs or G-MCMBs, and their electrochemical performance as electrode materials for electronic double layer capacitors (EDLC) or lithium-ion batteries (LIB) was investigated, respectively. The results showed that both MCMB-W prepared from water and MCMB-T prepared from THF had great spherical structure with the size of 1~2 μm. In addition, A-MCMB-T had a high specific surface area (1391 m2 g−1), micropore volume (0.55 cm3 g−1) and mesopore volume (0.24 cm3 g−1), exhibiting 30% higher specific capacitance than the original material, and its capacitance retention was also significantly improved when it was used as an electrode material for EDLC. Moreover, G-MCMB-T had high graphitization degree (0.895) and orderly lamellar structure, which demonstrated high specific capacity of 353.5 mAh g−1 after 100 cycles at 100 mA g−1 when it was used as an electrode material for LIB. Therefore, this work proposed and verified a new preparation method of MCMBs, which could provide a strategy for designing and developing traditional energy storage materials.

To obtain excellent carbonaceous precursors, the oxidation reaction mechanism and kinetics of ethylene tar were investigated. The oxidation process of ethylene tar was divided into three stages (350-550 K, 550-700 K and 700-900 K) according to the thermogravimetric curve. To reveal the oxidation reaction mechanism of ethylene tar, the components of evolved gases at different stages were further analyzed online by mass spectrometry and infrared technology. Then, based on the thermogravimetric curve of ethylene tar at different reaction temperatures, the whole reaction process was divided into four parts to perform kinetics simulation calculation. With the help of the iso-conversional method (Coats-Redfern) to analyze the linear regression rates (R2) between 17 common reaction kinetics models and experimental data, the optimal reaction kinetics model for expressing oxidation process of ethylene tar was determined. The results show that: (1) In the oxidation process, the side chains of aromatic compounds firstly react with oxygen to form alcohols and aldehydes, leaving peroxy-radicals to aromatic rings. After that, the aromatic compounds with peroxy-radicals undergo polymerization/condensation reaction to form larger molecular. (2) The fourth-order of reaction model is adopted to describe the first three parts of the oxidation process, and the activation energies are 47.330 kJ·mol−1, 18.689 kJ·mol−1 and 9.004 kJ·mol−1 respectively. The three-dimensional diffusion model is applied to the fourth part of the oxidation process, and the activation energy is 88.369 kJ·mol−1.

Li-Se Batteries has been considered as promising lithium-ion batteries due to their super volumetric energy density and high electrical conductivity of Se. However, the development of Li-Se batteries application is impeded by the boring volume expansion and polyselenide dissolution of electrodes during cycling, as well as the low selenium loading. A feasible and effective approach to settle these three issues is to keep selenium into a carbon host with sufficient pore volume and simultaneously enhance the interfacial interaction between selenium and carbon. A novel cathode material of Se encapsulated into honeycomb 3D porous carbon (HPC@Se) with Se-C bonds for Li-Se Batteries is synthesized by impregnating Se into the tartrate salt derived honeycomb 3D porous carbon. The pore volume of the obtained honeycomb 3D porous carbon is up to 1.794 cm3 g−1, which allows 65%wt selenium to be uniformly encapsulated. Moreover, the strong chemical bonds between selenium and carbon are beneficial for stabilizing selenium, thus further relieving its huge volume expansion and polyselenide dissolution as well as promote the charge transfer during cycling. As expected, HPC@Se cathode presents fantastic cyclability and rate performance. After 200 cycles, its specific capacity remained at 561 mA h g−1 (83% of the theoretical specific capacity) at 0.2 C. And the capacity recession is just 0.058 percentage each cycle. Besides, HPC@Se cathode can also demonstrate a considerable capacity of 472.8 mA h g−1 under the higher current density of 5 C.

Graphite is one of the most promising anode materials for potassium-ion batteries (PIBs) due to its low cost and stable discharge plateau. However, its poor rate performance still needs to be improved. Herein, a novel graphitic anode was designed from commercial mesocarbon microbeads (MCMB) by KOH treatment. Through limited oxidation and slight intercalation, an expanded layer with enlarged interlayer spacing formed on the surface of MCMB, by which the K+ diffusion rate was significantly improved. When served as the PIB anode, this modified MCMB delivered a high plateau capacity below 0.25 V (271 mAh g−1), superior rate capability (160 mAh g−1 at 1.0 A g−1), excellent cycling stability (about 184 mAh g−1 after 100 cycles at 0.1 A g−1), and high initial coulombic efficiency with carboxymethyl cellulose as binder (79.2%). This work provides a facile strategy to prepare graphitic materials with superior potassium storage property.

2022, 37(5): 1-4.

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2022, 37(5): 2-2.

2022, 37(5): 781-801.   doi: 10.1016/S1872-5805(22)60640-1

Micro-supercapacitors hold great promise for powering the Internet of Things devices owing to their high power density and long cycling life. However, the limited energy density hinders their practical use. Electrode materials play an important role in the performance of micro-supercapacitors. With the advantages of a large specific surface area and a high electrical conductivity, graphene has been considered a good candidate for the electrode material of micro-supercapacitors. The two-dimensional surface of graphene is parallel to the direction of transport of the electrolyte ions for micro-supercapacitors with an in-plane structure, which helps improve the ion accessibility of the electrodes. Therefore, the construction of graphene-based in-plane micro-supercapacitors has aroused great interest among researchers. Here, we summarize the recent advances in graphene and graphene-based materials for in-plane micro-supercapacitors from the perspective of electrode material design. The electrode materials include graphenes produced by chemical vapor deposition, liquid-phase exfoliation, reduction of graphene oxide, laser induction and heteroatom doping, as well as graphene-based composites, such as carbon nanotube/graphene, transition metal oxide/graphene, conducting polymer/graphene and two-dimensional material/graphene composites. Challenges and opportunities in graphene-based in-plane micro-supercapacitors are discussed, and future research directions and development trends are proposed.

2022, 37(5): 802-826.   doi: 10.1016/S1872-5805(22)60638-3

A silicon anode with a high specific capacity is one of the most promising candidates for developing advanced rechargeable lithium-ion batteries (LIBs). However, the problems of low electrical conductivity, severe volume changes during use and an unstable solid electrolyte interface seriously hinder their use in LIBs. Although using the carbon materials used to construct Si/C composite anodes have demonstrated their advantages in improving the performance of Si-based anodes, the binder, another key component of the electrode, also has a significant effect on the electrochemical performance of a battery. A self-healing binder uses non-covalent and reversible covalent bonds to effectively improve the cycling stability of LIBs by repairing the internal/external damage caused by the huge volume change of a Si-based anode. As for the solid-state polymer electrolytes (SPEs) of flexible lithium batteries, the use of self-healing polymers can also quickly repair the damages or cracks in the SPEs, and have a promising prospect in the development of flexible and wearable electronics. The paper gives an overview of the synthesis, characterization and self-healing mechanisms of the self-healing polymer binders for use in Si and Si/C anodes and their recent application in flexible lithium batteries is briefly summarized. The related technical challenges and design requirements for self-healing polymer binders used in the Si and Si/C anodes of LIBs are discussed.

2022, 37(5): 827-851.   doi: 10.1016/S1872-5805(22)60628-0

The ever-growing demands for wearable devices has stimulated the development of advanced flexible energy storage devices. Aqueous rechargeable zinc ion batteries (ZIBs) have gained much attention due to their low cost and intrinsic safety. Carbon materials with excellent conductivity, high mechanical strength, and light weight, can be used to construct flexible ZIBs (FZIBs). Here, we summarize the recent advances in carbon materials (e.g., carbon nanotubes, carbon fibers, graphene) for high-performance FZIBs with one-dimensional cable-shaped, two-dimensional planar, and three-dimensional sandwich configurations. Ways for constructing different types of FZIBs for better electrochemical performance are emphasized. The vital roles of carbons as the conductive materials and current collectors of cathodes, the current collectors and host materials of anodes, and modifiers of functional separators are discussed. The challenges and prospects of advanced carbon materials for next-generation FZIBs are also briefly discussed.

2022, 37(5): 852-874.   doi: 10.1016/S1872-5805(22)60631-0

With the rapid growth of the flexible and wearable electronics market, there have been big advances in flexible electrochemical energy storage technologies. Developing flexible electrodes with a low cost, superior safety, and high performance remains a great challenge. In recent years, potassium-based electrochemical energy storage devices have received much attention by virtue of their cost competitiveness and the availability of potassium resources. Carbon materials have been widely used as electrode materials or substrates for flexible energy storage devices due to their excellent properties, such as low weight, non-toxicity and abundance. Here, we summarize the recent advances in carbon materials (e.g. carbon nanofibers, carbon nanotubes, and graphene) for use in flexible electrochemical potassium storage devices, including potassium-ion batteries, potassium-ion hybrid capacitors, and K-S/Se batteries. Strategies for the synthesis of carbon-based flexible electrodes and their reported electrochemical performance are outlined. Finally, the challenges of future developments in this field are discussed.
2022, 37(5): 875-897.   doi: 10.1016/S1872-5805(22)60637-1

The construction of flexible supercapacitors with high electrochemical performance and excellent mechanical properties to power flexible electronics and sensors is very important. Freestanding electrodes play a crucial role in flexible supercapacitors, and carbon has been widely used in this role because of its high electronic conductivity, tunable porosity, adjustable surface area, excellent mechanical properties, low density and easy functionalization. It is also abundant and cheap. Recent progress on the fabrication of freestanding carbon electrodes based on various carbon materials for use in flexible supercapacitors is summarized, and remaining challenges and future opportunities are discussed.

2022, 37(5): 898-917.   doi: 10.1016/S1872-5805(22)60634-6

Next-generation wearable and portable devices require rechargeable microbatteries to provide energy storage. Three-dimensional (3D) printing, with its ability to build geometrically complex 3D structures, enables the manufacture of microbatteries of different sizes and shapes, and with high energy and power densities. Lightweight carbon materials have a great advantage over other porous metals as electrode materials for rechargeable batteries, because of their large specific surface area, superior electrical conductivity and high chemical stability. In recent years, a variety of rechargeable microbatteries of different types have been successfully printed using carbon-based inks. To optimize their electrochemical performance and extend their potential applications, it is important to analyze the design principles with respect to the 3D printing technique, printable carbon materials and promising applications. This paper provides a perspective on recent progress in the four major 3D printing techniques, elaborates on conductive carbon materials in addressing the challenging issues of 3D printed microbatteries, and summarizes their applications in a number of energy storage devices that integrate with wearable electronics. Current challenges and future opportunities for carbon-based microbattery fabrication by 3D printing techniques are discussed.

2022, 37(5): 918-935.   doi: 10.1016/S1872-5805(22)60642-5

Along with the emergence of wearable electronic devices, green energy devices like Zn-ion hybrid supercapacitors (ZHSCs), which are extremely safe and cheap, and have excellent stability and high power energy densities, have received great attention. Carbonenes, mainly including graphene and carbon nanotubes (CNTs), are promising materials for ZHSCs because of their exceptional electrical conductivity and excellent mechanical stability. A comprehensive overview of strategies for the modification of carbonene-based materials for ZHSCs, and a brief summary of their energy storage mechanisms is given and topics for potential research are suggested.

2022, 37(5): 936-943.   doi: 10.1016/S1872-5805(22)60633-4

2022, 37(5): 944-955.   doi: 10.1016/S1872-5805(22)60617-6

A coaxial anode with a carbon fiber core encapsulated in nanocrystalline FeNiMnO4 with a nitrogen-doped carbon sheath was prepared using carbon fiber cloth as the core, FeNiMnO4 nanocrystallite arrays as the first coating layer and nitrogen-doped carbon derived from F127 (a kind of triblock copolymer)-resorcinol-melamine gel as the outer layer. After annealing at 600 °C it was used as the anode material of an all solid flexible lithium ion battery using LiFePO4 as the cathode material and boron nitride modified polyethylene oxide as the electrolyte. The battery had a large areal capacity of ~1.40 mAh cm−2 and satisfactory cycling stability under different bending and strain states. Annealing below 600 °C leads to incomplete carbonization of the nitrogen-doped carbon and thus a low electrical conductivity while above 600 °C aggregation of FeNiMnO4 nanocrystallites and their detachment during cycling are observed under bending and strain.

2022, 37(5): 956-967.   doi: 10.1016/S1872-5805(22)60627-9

The rapid development of micro/nanomanufactured integrated microsystems in recent years requires high performance micro energy storage devices (MESDs). Li-ion microbatteries (LIMBs) are the most studied MESDs, but the low mass loading of active materials and the less-than-perfect energy density hinder their further application. A 3D printed ZnSe/N-doped carbon (ZnSe/NC) composite electrode was designed and fabricated by extrusion-based 3D printing and a post-treatment strategy for use as the anode of LIMBs. The high capacity ZnSe nanoparticles are confined in the NC, where the NC not only improves the conductivity but also acts as a buffer layer to reduce the volume expansion and provide additional active sites for electrochemical reactions. The interconnected design of the 3D printed electrode is good for fast mass transfer and ion transport. A freestanding 3D printed ZnSe/NC electrode with a high mass loading of 3.15 mg cm−2 was achieved by direct ink printing, which had a superior energy density and decent reversibility in high-power LIMBs. This strategy can be used for other high-performance electrodes to achieve a high-mass-loading of active materials for microbatteries, opening up a new way to construct advanced MESDs.

2022, 37(5): 968-977.   doi: 10.1016/S1872-5805(22)60629-2

Following the fast growth of micro-energy storage devices, there is an urgent need to develop miniaturized electronic devices with excellent performance that are both green and safe. Planar interdigitated rechargeable Zn microbatteries (MBs) have gained widespread attention in recent years due to their ease of series-parallel integration, mechanical flexibility and no need for traditional separators. We prepared a patterned cathode of NiCo layered double hydroxide (LDH)@indium tin oxide (ITO) nanowires (NWs) @carbon cloth (CC) by the chemical vapor deposition of ITO NWs on the carbon fibers in a CC, laser patterning, and finally the electrodeposition of NiCo-LDH to coat the ITO NW@carbon fibers. The cathode was combined with a patterned Zn foil anode to form a planar MB. Because of the highly conductive ITO NWs@CC current collector, the interdigitated MB had a satisfactory performance. The planar MB has a high specific capacity of 453.5 mAh g−1 (corresponding to 0.56 mAh cm−2) in an alkaline water-based electrolyte at 1 mA cm−2. After 4 000 cycles the capacity increased to 216% of the initial value due to gradual penetration of electrolyte into the three-dimensional NiCo-LDH@ITO NW@CC network. It also had excellent energy (798.4 μWh cm−2, corresponding to 649.9 Wh kg−1) and power densities (4.1 mW cm−2, corresponding to 3 282.7 mW kg−1). Furthermore, MBs connected in series-parallel in lighting tests illustrate the excellent performance of the device. Therefore, these fast and simple Zn MBs with an in-plane interdigital structure provide a reference for next-generation high-performance, environmentally-friendly, and scalable planar micro-energy storage systems.

2022, 37(5): 978-987.   doi: 10.1016/S1872-5805(22)60641-3

Three-dimensional carbon nanonetworks (3D CNNs) have interconnected conductive skeletons and accessible pore structures, which provide multi-level transport channels and thus have promising applications in many areas. However, the physical stacking of these network units to form long-range conductive paths is hard to accomplish, and the introduction of micropores and small mesopores is usually difficult. We report a simple yet efficient strategy to construct CNNs with a nitrogen-doped micro-meso-macroporous carbon nanonetwork using Schiff-base gelation followed by carbonization. Using a polyacrolein-grafted graphene oxide molecular brush as the building block and tetrakis (4-aminophenyl) methane as the crosslinking agent, the obtained molecular brush nanonetworks have a high carbon yield and largely retain the original morphology, leading to the formation of a 3D continuous nanonetwork after carbonization. The materials have a micro-meso-macroporous structure with a high surface area and a highly conductive N-doped carbon backbone. This unique structure has a large number of exposed active sites and excellent charge/mass transfer ability. When loaded on carbon cloth and used as the electrodes of a flexible supercapacitor, the CNN has a specific capacitance of 180 F g−1 at 1 A g−1 and a high capacitance retention of 91.4% after 10 000 cycles at 8 A g−1 .

2022, 37(5): 988-999.   doi: 10.1016/S1872-5805(22)60639-5

Organic-inorganic hybrid perovskite films made by low-temperature solution processing offer promising opportunities to fabricate flexible solar cells while formidable challenges regarding their environmental and mechanical stability remain due to their ionic and fragile nature. This work explores the possibility of chemical crosslinking between adjacent grains by the interfacial embedding of laser-derived carbon dots with halogen-terminated surfaces to improve the flexibility and stability of the polycrystalline films. A series of halogen-terminated carbon dots was generated in halobenzene solvents by pulsed laser irradiation in the liquid, and were then placed in the surface and grain boundaries of the perovskite film by an antisolvent procedure, where an immiscible solvent was poured onto the coating surface with a suspension containing carbon dots and perovskite precursors to cause precipitation. Strong interaction between perovskite and the carbon dots results in effective defect passivation, lattice anchoring and a change in the carrier dynamics of the perovskite films. Because of this, unencapsulated flexible perovskite solar cells after the interfacial embedding have power conversion efficiencies up to 20.26%, maintain over 90% of this initial value for 90 days under a relative humidity of 40% and have a thermal stability of 200 h even at 85 °C. The flexible devices withstand mechanical deformation, retaining over 80% of their initial values after 500 bend cycles to a radius of curvature of 4 mm.

2022, 37(5): 1000-1010.   doi: 10.1016/S1872-5805(22)60632-2

Due to the difference of energy storage mechanisms between the anode and cathode materials, the power density or rate performance of a lithium-ion capacitor is greatly limited by its anode material. Hard carbon is a promising anode material for lithium ion capacitors, and its modification is an important way to improve the electrochemical performance of lithium-ion capacitors. A commercial hard carbon from Kuraray Inc was modified by oxidation followed by intercalation with ZnCl2 (ZnCl2―OHC). The reversible capacity of a half-cell prepared using this material was 257.4 mAh·g−1 at 0.05 A·g−1, which is obviously higher than the unmodified one (172.5 mAh·g−1). The capacity retention of a full cell prepared using ZnCl2―OHC as the anode and activated carbon as the cathode reached 43.3% when the current density increased from 0.1 to 10 A·g−1, which is more than twice that of the untreated hard carbon. After 5 000 charge-discharge cycles at 1 A·g−1, the capacity retention of the full cell was about 98.4%. The modification of hard carbon by surface oxidation and intercalation is therefore a promising way to improve its anode performance for lithium ion capacitors.

2022, 37(5): 1011-1020.   doi: 10.1016/S1872-5805(22)60648-6

C/C复合材料因优异的高温性能被认为是高温结构件的理想材料。然而,C/C复合材料在高温高速粒子冲刷环境下的氧化烧蚀问题严重制约其应用。因此,如何提高C/C复合材料的抗烧蚀性能显得尤为重要。笔者综述C/C复合材料抗烧蚀的研究现状。目前,提高C/C复合材料抗烧蚀性能的途径主要集中于优化炭纤维预制体结构、控制热解炭织构、基体中陶瓷掺杂改性和表面涂覆抗烧蚀涂层等4种方法。主要介绍以上4种方法的研究现状,重点介绍基体改性和抗烧蚀涂层的最新研究进展。其中,涂层和基体改性是提高C/C复合材料抗烧蚀性能的两种有效方法。未来C/C 复合材料抗烧蚀研究的潜在方向主要集中于降低制造成本、控制热解炭织构、优化掺杂的陶瓷相以及将基体改性和涂层技术相结合。