The molecular structures of precursors play a critical role in determining the properties of mesophase pitch (MP) for mesophase pitch-based carbon fibers. In this study, a series of polycondensation pitches (PPs) with different molecular characteristics were prepared from fluid catalytic cracking slurry oil by varying the thermal polycondensation time. These precursors were then converted into spinnable MPs through solvent extraction followed by secondary thermal treatment. The molecular structural evolution of PPs and its influence on the molecular structure, softening point, and optical texture of MPs were systematically investigated. The results show that the molecular composition of PPs is governed by highly reactive components in the early stage of polycondensation. With increasing reaction time, the components generated from less reactive species gradually become dominant. The anisotropic content of MP is primarily determined by the proportion of small molecules (<1200 Da), such that a fully anisotropic MP cannot be formed when their content exceeds 30%. Under such conditions, a continuous anisotropic matrix with dispersed isotropic domains forms only when the content of large molecules (>1600 Da) exceeds 50%. Otherwise, dispersed anisotropic spheres are observed. Furthermore, in this study, increasing the content of intermediate molecules (1200-1600 Da) effectively lowers the softening point, thereby improving MP spinnability. Regulating the molecular composition of MP enables effective control over the texture of MP-based carbon fibers, allowing the formation of either radial or onion-skin structures. These findings provide structural guidance for the rational design of spinnable mesophase pitch precursors with a balanced combination of anisotropy and processability.

For carbon fiber-reinforced polymer composites (CFRPCs), the final properties strongly rely on the interfacial adhesion which is related not only to the fiber surface roughness but also to interaction between the components. Therefore, simultaneously improving fiber surface roughness and optimizing its reactivity via convenient method is of great value for high performance CFRPCs. Herein, by arraying NPA (calcium carbonate as the core while calcium norbornene dicarboxylate as the shell) nanoparticles on acidized carbon fiber felt (HCFF) surface, hybrid carbon fiber felt (HCFF@NPA) with both rough surface and high reactivity was synthesized, and strengthening effect for polydicyclopentadiene (PDCPD) was investigated. The results indicated that HCFF@NPA could form a robust interface with PDCPD matrix, which was ascribed to the rough hybrid fiber surface and copolymerization of norbornene units on NPA with DCPD monomers. The obtained PDCPD/HCFF@NPA composites exhibited significantly enhanced interlaminar shear strength and flexural strength of 24.1 f 0.3 MPa, 243.4 f 4.0 MPa as compared with those of 10.8 f 0.2 MPa, 145.2 f 14.7 MPa for the pristine PDCPD/CFF sample. This work paves a novel pathway for designing hybrid fibers with nanoparticles and high-performance fiber-reinforced polymer composites.

Hard carbon (HC) with an ultramicropore structure has emerged as a promising material for sodium-ion batteries. However, it is still a challenge to fabricate high-performance ultramicropore structures at low temperatures. Herein, low-temperature (900 degrees C) force-field (20 MPa) induced esterification reactions were proposed to prepare HC rich in ultramicropores (0.4-0.7 nm). The force field promotes the esterification reaction between carboxyl and hydroxyl groups to form O 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 C-O bonds, inducing carbon layer bending. Simultaneously, the force field accelerates the growth and stacking of carbon layers to construct abundant ultramicropores. HC-20 exhibits a large pore volume and a small entrance diameter, which not only increases reversible capacity but also limits the contact between solvated sodium ions and pores. The optimized HC showed an excellent ICE of 82.2% and a high reversible capacity of 316.2 mA h g-1, as well as 98.0% capacity retention at 25 mA g-1 after 100 cycles. Besides, the HC-20//NFM full cell exhibits a high energy density of 231.5 Wh kg-1 and excellent cycle stability. This study provides a novel strategy for preparing HC rich in ultramicropores at low temperature, offering guidance for research on high-performance HC materials.

Na2S, as the terminal discharge product of room-temperature sodium-sulfur (Na-S) batteries, is electronically and ionically insulating. When it deposits as a compact film on the cathode, the cathode will become passivated, hindering electron transport and inhibiting further sulfur conversion reactions. Existing catalyst strategies promote the formation of Na2S thermodynamically by enhancing polysulfide adsorption, but this does not address the kinetics passivation issue. Here, we adopt the exchange current density (j0) as a kinetic descriptor of the Na2S nucleation mode. Finite-element simulations reveal that increasing j0 drives the nucleation pathway from progressive to instantaneous nucleation. The deposit morphology then evolves from a compact passivating film to uniformly dispersed nanoparticles, and ion and electron transport channels are preserved. This pathway prevents Na2S aggregation and electrode passivation, maintaining electrochemical activity at deep discharge. Guided by this kinetic insight, nitrogen-doped porous carbon-supported V single-atom catalysts (NPC-V SACs) with high apparent j0 were fabricated, and instantaneous Na2S nucleation was achieved on their surfaces. The resulting Na-S battery retains 976.3 mAh g-1 after 200 cycles at 0.2 A g-1, with a decay rate of only 0.08% per cycle. This work establishes a kinetic design perspective for regulating Na2S nucleation in durable Na-S batteries.

Hard carbon, as a preferred anode material for sodium-ion batteries (SIBs), faces significant challenges in constructing a closed-pore structure and a rapid diffusion pathway under low-temperature carbonization. This severely hinders the reversible storage of sodium in hard carbon at high rates. This work proposes a thermal-mechanical coupling strategy to prepare biomass-derived carbon with abundant closed-pore structures and rapid diffusion kinetics for high-performance sodium storage. Under the dual influence of thermal and force fields, graphitic microcrystalline layers undergo reconstruction through slip and rearrangement processes. This transforms disordered amorphous carbon into an ordered carbon layer, forming effectively curved closed-pore walls that create abundant closed-pore structures within the carbon matrix. The PPHC-10 delivers a high reversible capacity of 333.01 mAh g-1 at 25 mA g-1, with a remarkable initial Coulombic efficiency of 84.6% and outstanding rate performance. Through in situ and ex situ characterizations, the sodium storage mechanism of PPHC-10 is elucidated as follows: an adsorption-insertion-pore filling. This study introduces a strategy for designing high-performance SIB anode materials with significant potential for industrial-scale production.

Boosting rate performance in potassium-ion batteries (PIBs) anodes is of crucial importance. However, conventional nanostructuring and defect engineering strategies inevitably sacrifice initial Coulombic efficiency (ICE), packing density, and the average K+ storage potential. Herein, we propose texture engineering from a novel perspective to boost the comprehensive potassium storage capability of carbon anodes. Pitch with different mesophase content is used as the precursor to prepare texture-tailored micron-sized carbon fibers. These tailored fibers serve as model systems to systematically reveal the intrinsic mechanism of texture engineering on potassium storage performance. Experimental and finite element simulation analyses indicate that the ordered texture of carbon anodes reduces ion transport tortuosity, facilitating K+ intercalation/deintercalation kinetics and thus boosting the rate performance (135.3 mAh g-1 at 2 A g-1). Such an ordered texture suppresses irreversible K+ consumption and homogenizes internal K+ distribution, leading to a significantly enhanced ICE (71.7%). Additionally, its abundant low-potential sp2 hybridized carbon active sites afford an ultrahigh reversible capacity below 1 V (316.0 mAh g-1 at 0.05 A g-1). This study delivers novel insights into advanced carbon anode design for high-performance PIBs.

The nitrogen/sulfur (N/S) co‐doping strategy has gained significant attention in the development of carbon‐based anodes for potassium‐ion batteries (PIBs) due to its capapcity to enhance specific capacity and accelerate reaction kinetics. Yet, the C─S bond‐driven conversion reaction would inevitably induce critical challenges, including poor stability and high charging voltage, thereby severely impeding the commercialization of N/S co‐doped carbon anodes. Herein, a novel sulfonic group dominated N/S co‐doped carbon (NSAC‐600) is synthesized via a facile low‐temperature carbonization strategy with coal tar pitch as a precursor. The sulfonic groups in NSAC‐600 have strong sulfur‐locking ability, that can suppress the formation of potassium polysulfides during K storage. Moreover, the N and sulfonic groups synergistically create abundant active sites for K + adsorption, expand the carbon interlayer spacing, and help to create rapid charge diffusion pathways. Thereby, the NSAC‐600 can deliver high‐rate performance (217.0 mAh g −1 at 5 A g −1 ), good cycling stability (without any capacity decay after 1400 cycles at 2 A g −1 and stable operation for 5600 cycles at a high current density of 5 A g −1 ) and low depotassium voltage. An “adsorption/intercalation/limited‐conversion” mechanism is proposed to elucidate the potassium storage behavior in this novel carbon material. This work may provide a new horizon for advanced N/S co‐doped carbon anodes.

N-doped porous carbon materials are promising potassium-ion battery anodes for overcoming the depressing rate performance and poor cycling stability issues associated with the oversized radius of K-ion. However, the relatively low initial coulombic efficiency (ICE) as a result of porous structure and doped heteroatoms may limit the future application of potassium-ion batteries. Herein, a novel N-doped porous graphite-like carbon armored with dense amorphous shell is synthesized through a Trojan horse strategy by etching and doping the carbon matrix from inside out using oxidized coal tar pitch coated C3N4 as precursor. The N-doped porous interior, which endows anode outstanding rate performance (156.5 mAh g-1 at 10 A g-1) and superior reversible capacity (412.3 mAh g-1 at 0.05 A g-1), is isolated from the electrolyte by the external dense shell to gain a high ICE of 62.6%. In addition, the integrated structure mitigates the risk of phase separation between the shell and core, thereby high-current stability over 6000 cycles obtained. This work shed a new light on the fabrication of the well-balanced carbon anodes to meet the demand of the future PIBs industry.

In order to break through the difficulty of balancing the thermal insulation and mechanical properties of composites, a mathematical model of the effects of thermal insulation fillers and reinforcing fibers on the thermal insulation and mechanical properties of composites was proposed using a mixture design approach. The synergistic interaction between fillers was investigated. Multi-objective optimization method was used to optimize the formulation under specific conditions. The optimized composites were prepared with a low thermal conductivity of 0.108 W m(-1) K-1, and the compressive and flexural strengths reached 111.098 MPa and 26.985 MPa, respectively. Meanwhile, the tests showed that the composites had excellent thermal insulation effect and thermal stability.

The low-voltage charging capacity and rate performance are two crucial but mutually restricted properties of K-ion batteries. Herein, a sulfonamide and amide linkages-triggered N doping high-temperature removal strategy is proposed to obtain porous carbon with rich carbon vacancies, high sp(2) hybridized C content (65.3%), and large interlayer spacing using coal tar pitch as carbon precursor. Carbon vacancies and sp(2) hybridized C are proved to be not only active sites for low-voltage potassium storage but also conducive to the fast transfer of ions and electrons, endowing reversible and fast potassium storage at low voltage. Moreover, abundant carbon vacancies and large carbon interlayer spacing alleviate volume variation, improving the cycling stability for 8500 cycles (about 3700 h). This work sheds new light on the design of low-voltage, durable, and fast potassium storage carbon anodes, and promotes the development of practical carbon anodes for high energy density K-ion batteries in the future.

In this study, a series of high temperature resistant water-soluble thermoplastic sizing agents were designed and synthesized to improve the interfacial bonding of CF/PPESK composites. The effects of the ratio of water-soluble functional monomer (PPL) and high temperature resistant monomer (DHPZ) on the performance of the pastes were investigated. The results showed that the sizing agent with PPL: DHPZ = 6: 4 had the best performance, and its thermal decomposition temperature was up to 348 degrees C, which met the requirements of the composite molding process. The ILSS and flexural strength reached the peaks of 67.2 MPa and 1526.5 MPa. The retention rates were 89.7 % and 81.8 %, respectively, after hydrothermal aging treatment, compared with 77.7 % and 79.2 % for the epoxy sizing agent. The bottleneck of traditional epoxy sizing agent and CF/PPESK composites molding process mismatch has been broken.

Lithium metal anode (LMA) is expected to be the ideal anode material for future high-energy-density batteries, but regulating the complex electrolyte-anode interface remains a challenge. In this work, a stable Li2Te coating is formed on the surface of commercial copper mesh (LTCM) using a simple and quick method to improve lithium metal anode interfacial kinetics. Li2Te possesses a strong affinity for both Li+ and TFSI- anions, which reduces the lithium nucleation barrier and guides the formation of inorganic-rich SEI, accelerates the diffusion of Li+, and promotes the growth of lithium metal along the plane. The highly conductive Li2Te and Cu generated by in situ lithiation reaction together constitute an effective electron-conducting network, which synergistically enhances the interfacial kinetics and the cycling stability of LMA. As a result, the LTCM maintains high Coulombic efficiency (98%) even after 2200 cycles at 1 mA cm(-2), whereas the symmetric cell has a long cycle life of over 5400 h at 1 mA cm(-2). In addition, the full cells with LFP display a high capacity retention ratio (80%) after 480 cycles at 1 C and the corresponding pouch cell can cycle steadily more than 464 cycles at 1 C, which has good application prospects.

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. A novel graphitic anode was designed from com-mercial mesocarbon microbeads (MCMBs) by KOH treatment. Using limited oxidation and slight intercalation, the interlayer spa-cing of graphitic layers on the surface of the MCMBs was increased, causing the K+ diffusion rate to be significantly improved. When this modified material was combined with carboxymethyl cellulose as a binder (79.2％) and used as a PIB anode, it had 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 a high initial coulombic efficiency. This work provides a simple strategy to prepare graphitic materials with an excellent potassium storage performance.

Disordered nucleation sites and a fragile solid electrolyte interphase on the reactive interface tend to cause uncontrolled growth of lithium dendrites, which induce severe safety concerns and prevent lithium metal batteries from finding practical applications. Herein, novel stepped carbon nanosheets with abundant step edges and ultra‐high fluorine content (37.44 at%) are fabricated by combining an improved molten salt synthesis method with C 4 F 8 vacuum plasma treatment. The solvent‐induced spatial confinement effect, i.e., orientation carbonization of pitch macromolecules, leads to the formation of step‐edge‐enriched nanoarrays. Meanwhile, the adequate exposure of edge sites on the basal plane of carbon nanosheets is conducive to achieve the ultra‐efficient doping of elemental fluorine in only 10 min. Further experiments and theoretical calculations demonstrate that the coupling effect of sufficient edge sites and active semi‐ionic CF/covalent CF 2 groups on the carbon surface can not only form 2D fluorinated lithium chain and a robust LiF network, but also effectively facilitate Li ion redox kinetics and morphological stability, presenting a step‐edge‐guided plating process. As such, the developed anodes deliver an ultra‐low nucleation overpotential (≈10.5 mV), high Coulombic efficiency (>98% over 385 cycles), ultra‐long cycling duration for up to 3000 h under ≈10 mV, and excellent full battery performance.

Soft carbon has been regarded as one of the most promising anode materials for potassium-ion batteries. However, the rearrangement of planar aromatics at high carbonization temperature usually yields a highly graphitized structure, which generally leads to inferior rate and cycle performance. In addition, the role of intrinsic carbon defects on potassium storage has not been well reported yet. In this work, crosslinked pitch-based soft carbon nanosheets have been synthesized through the iodination/dehydroiodination process at low temperature and carbonization with NaCl template. The iodine-treatment efficiently crosslinks the planar aromatics to three-dimensional framework by alkyl-bridged linkages, and reduces the strong π-π interaction during carbonization. This unique microstructure yields an ordered-in-disordered carbon microstructure, enlarged interlayer spacing, and abundant intrinsic defect sites. Benefited from these merits, the optimal sample displays 140% increase of reversible capacity to the pristine pitch-based carbon at 5 A g-1. Particularly, it also presents 87.4% capacity retention after 1000 cycles at 1 A g-1. This facile but simple strategy is expected to expand to other high-performance carbon materials and further understand the effect of intrinsic defects for potassium storage and beyond.

Photocatalytic H2 evolution is considered one of the most important processes for H2 production. Carbon materials are potential candidates for large-scale and cost-effective photocatalytic water splitting, yet their activity needs to be further improved. We report the synthesis of nitrogen-doped porous carbons using peat moss as a precursor and urea as a nitrogen source. The properties of carbons as photothermal-assisted visible-light photocatalysts were investigated. Due to the photothermal effect, the system temperature increased quickly to 55 °C in 15 min under visible light irradiation, which subsequently helps increase the photocatalytic activity by about 25%. It has been found that the crystallinity and nitrogen content of the carbon materials can be changed by changing the carbonization temperature, and these have an impact on their photocatalytic activity. A peat-derived carbon carbonized at 800 °C, with a N content of 4.88 at.% and an appropriate crystallinity has an outstanding photocatalytic activity with a high H2 evolution rate of 75.6 μmol H2 g−1 h−1 under visible-light irradiation.

Despite much efforts to stabilize sodium metal anodes for promoting their commercial applications, achieving a safe cycling process without intrinsic dendrite growth remains difficult owing to the unstable reaction interface and irregular sodium metal propagation. Herein, fluorine‐superdoped carbon nanotubes with a fluorine content of 14.38 at% are achieved using a new oxidation‐assisted plasma strategy, and then alternately assembled with cellulose nanofibrils to form periodical conductive/dielectric composite paper with outstanding mechanical properties. The superdoping of fluorine facilitates the construction of a NaF‐dominated solid electrolyte interphase layer, while the periodical conductive/dielectric network re‐homogenizes electric field distribution around irregular sodium protrusions, realizing a “bottom‐up” sodium orientation deposition and the “self‐correction” functionality during sodium plating/stripping process. Density functional theory calculations reveal that the specific oxygen species (CO/CO) and fluorine species (semi‐ionic CF/covalent CF 2 ) on the surface of carbon matrix, could remarkably trap active fluorine fragments and generate NaF with sodium metal, respectively, which promotes the superdoping of fluorine and forms dendrite‐free sodium anodes. This delicate structure renders the sodium anodes a low nucleation overpotential of ≈7 mV, high Coulombic efficiency of 99.5% over 300 cycles at 3 mA cm −2 , stable operation for up to 2100 h under ≈16 mV, and excellent full battery performance.

Biomass shows great potential in synthesizing carbon materials for energy applications because of its renewability and low price. Rationally designing porous carbons with proper morphology and compo-sition are beneficial to promoting its application in energy storage devices. Here, an environmentally friendly approach is proposed to prepare three-dimensional (3D) N, P co-doped hierarchical porous carbon (NP-HPC) for supercapacitors. The 3D cross-linked porous network not only promotes the infil-tration of electrolytes, but also boosts the transportation of ion/electron. The high microporosity com-bined with heterogeneous doping provides more defects and active sites, improving the surface charge storage. Hence, the NP-HPC electrode achieves a high capacitance of 358 F g(-1) at 0.05 A g(-1) as well as good rate performance of 238 F g(-1) at 50 A g(-1). Moreover, NP-HPC-based all-solid-state supercapacitor exhibits a long lifespan over 10,000 cycles. The impressive performance of NP-HPC indicates the potential of biomass-derived porous carbons for supercapacitors through simultaneous morphology and doping engineering. (C) 2021 Elsevier Ltd. All rights reserved.

Pitch-based porous carbons with the abundant resources and high conductivity have potential advantages as potassium-ion battery anode materials. However, they suffer from small interlayer distance and rare potassium storage sites. Herein, nitrogen and phosphorus dual-doped coal tar pitch-based porous carbons (NPPC) was prepared in one-step carbonization using ammonium polyphosphate as N and P source and studied as the anodes for the potassium ion batteries. NPPC delivers a high capacity retention of 81.8% over 400 cycles at 1.0 A g(-1). When the current density is raised to 10 A g(-1), it can still retain a reversible capacity of 126 mAh g(-1). The effects of carbonation temperature and ratio of ammonium polyphosphate to coal tar pitch on nitrogen and phosphorus doping contents were investigated by in situ Fourier transform infrared and synchronous thermal analysis. This work may shed light on the design of advanced potassium-ion battery by employing heteroatom doped functionalized soft carbons. (C) 2021 Elsevier Ltd. All rights reserved.

Carbon materials are considered as one of the most promising electrocatalysts for the electrochemical CO2 reduction which can convert CO2 to value-added chemical products in a clean, cheap and efficient manner. However, the carbon-based catalysts still suffer from low partial current density under high Faradaic efficiency of products, which results from their poor intrinsic electrocatalytic activity and the use of insulating binders. Herein, we design a novel monolithic electrocatalyst by combining the carbon foam with Ni-N-x active sites, which possesses high electrical conductivity, low mass transfer resistance and abundant active sites. Benefiting from these structural advantages, this monolithic electrocatalyst exhibits a large partial current density (71.6 mA cm(-2) at -1.4 V versus reversible hydrogen electrode) and a stable Faradaic efficiency of CO (>90 %) at the applied potential range from -1.0 to -1.4 V.