Porous carbon materials with developed porosity,high surface area and good thermal-and chemicalresistance are advantageous for gas adsorption and separation.However,most carbon adsorbents are in powder form which exhi...Porous carbon materials with developed porosity,high surface area and good thermal-and chemicalresistance are advantageous for gas adsorption and separation.However,most carbon adsorbents are in powder form which exhibit high pressure drop when deployed in practical separation bed.While monolithic carbons have largely addressed the pulverization problem and preserved kinetics and usually suffer from abrasion during multiple adsorption-desorption cycles.Herein,we proposed the designed synthesis of mechanically robust carbon monoliths with hierarchical pores,solid nitrogen-containing framework.The synthesis started with the polymerization of resorcinol and formaldehyde under weakly acidic conditions generated from cyanuric acid,and then an appropriate amount of hexamethylenetetramine(HMTA)was added as a crosslinker to prompt the formation of three dimensional frameworks.After carbonization process,the as-obtained porous carbon monoliths have a high radial compressive strength of 886 N/cm as well as a BET specific surface area of up to 683 m2/g.At approximately 1 bar,the CO2 equilibrium capacities of the monoliths are in the range of 3.1–4.0 mmol/g at 273 K and of 2.3–3.0 mmol/g at 298 K,exhibiting high selectivity for the capture of CO2 over N2 from a stream which consists of 16.7%(v%)CO2 in N2.Meanwhile,they undergo a facile CO2 release in an argon stream at 298 K,indicating a good regeneration capacity.After cycle testing,sieving and regeneration,the adsorbent has no mass loss,compared to that of its fresh counterpart.展开更多
To improve the initial coulombic efficiency and bulk density of ordered mesoporous carbons, active Fe203 nanoparticles were introduced into tubular mesopore channels of CMK-5 carbon, which possesses high specific surf...To improve the initial coulombic efficiency and bulk density of ordered mesoporous carbons, active Fe203 nanoparticles were introduced into tubular mesopore channels of CMK-5 carbon, which possesses high specific surface area （〉1700 m2.g-1） and large pore volume （〉1.8 cm3-g-1）. Fine Fe203 nanoparticles with sizes in the range of 5-7 nm were highly and homogenously encapsulated into CMK-5 matrix through ammonia-treatment and subsequent pyrolysis method. The Fe203 loading was carefully tailored and designed to warrant a high Fe203 content and adequate buffer space for improving the electrochemical performance. In particular, such Fe203 and mesoporous carbon composite with 47 wt% loading exhibits a considerably stable cycle performance （683 mAh.g-1 after 100 cycles, 99% capacity retention against that of the second cycle） as well as good rate capability. The fabrication strategy can effectively solve the drawback of single material, and achieve a high-performance lithium electrode material.展开更多
Assembly of the top-down graphene units mostly results in 3D porous structure with randomly organized pores.The direct bottom-up synthesis of macroscopic 2D graphene sheets with organized pores are long sought in mate...Assembly of the top-down graphene units mostly results in 3D porous structure with randomly organized pores.The direct bottom-up synthesis of macroscopic 2D graphene sheets with organized pores are long sought in materials chemistry field,but rarely achieved.Herein,we present a self-catalysisassisted bottom-up route usingL-glutamic acid and iron chloride as starting materials for the fabrication of the millimeter-sized few-layer graphene sheets with aligned porous channels parallel to the 2D direction.The amino-and carboxyl-functional groups inL-glutamic acid can coordinate with iron cations,thus allowing an atomic dispersion of iron cations.The pyrolysis thus initiated the growth of graphene catalyzed by in-situ generated iron nanoparticles,and a dynamic flow of iron nanoparticles eventually led to the formation of millimeter-sized few-layer graphene sheets with aligned channels(60-85 nm in diameter).Used as anodes in lithium-ion batteries,these graphene sheets showed a good rate capability(142 m A h g^(-1) at 2 A g^(-1))and high capacity retention of 93%at 2 A g^(-1) after 1200 cycles.Kinetic analysis revealed that lithium ions storage was dominated by diffusion behavior and capacitive behavior together,in that graphene sheets with aligned channels could accelerate electron transfer and shorten lithium ions transport pathway.This work provides a novel approach to prepare unique porous graphene materials with specific structure for energy storage.展开更多
Alumina materials are widely applied either as a catalyst or support in various industrial catalytic processes. Impurities in alumina that are unfriendly to catalytic performance are inevitably present during the prod...Alumina materials are widely applied either as a catalyst or support in various industrial catalytic processes. Impurities in alumina that are unfriendly to catalytic performance are inevitably present during the production processes. Facing this problem, we here report that the use of sulfur-containing alumina as the support can generate active alumina-supported platinum catalyst, which exhibits superior propylene selectivity and anti-coking ability during propane dehydrogenation. It demonstrated that the sulfur impurity in alumina is not entirely detrimental. During the reduction process, the formation of gas-phase sulfur species increased the electrons and poisoned unsaturated sites of platinum particles. The sulfur impurity in alumina can be removed through a hydrogen reduction process, and the degree of desulfurization is correlated with the operating temperature. This study demonstrated that the rational use of impurity will contribute to the design of a catalyst with high reactivity for potential applications.展开更多
Anisotropic nanoparticles,giving rise to a large number of novel physicochemical properties and functionalities,have provoked increasing attentions in nanoscience and nanotechnology.The remained challenge is to develo...Anisotropic nanoparticles,giving rise to a large number of novel physicochemical properties and functionalities,have provoked increasing attentions in nanoscience and nanotechnology.The remained challenge is to develop synthetic methods for the fabrication of anisotropic nanoparticles with less symmetry under the principle of minimum surface free energy.Here,we established a crystallization-assisted asymmetric assembly method for the synthesis of anisotropic polymer nanocrescents and their carbonaceous analogues by using triblock copolymer F127 and octadecanol in aqueous solution.With the aid of molecular dynamics(MD)simulation,we demonstrate that the observed crescent structure is caused by asymmetry distribution of octadecanol crystal within the hydrophobic core of F127 micelles,via the formation of intermediate elliptic micelles bearing hydrophobic ends that further fuse with each other end-to-end at an angle into curing nanocrescent morphology.The influences of annealing time,annealing temperature,and mole ratios of precursors that govern the kinetics of the assembly and polymerization process were systematically investigated and a series of polymer nanocrescents with tunable length of~85 to~262 nm and aspect ratio of~1.1 to~3.0 were prepared.The ability to create novel crescent-shaped polymer and carbon nanoparticles and the identification of asymmetric assembly process by combining experiment and simulation study will provide a valuable contribution both to theoretical and technological researches.展开更多
Designing a better carbon framework is critical for harnessing the high theoretical capacity of Li-S batteries and avoiding their drawbacks, such as the insulating nature of sulfur, active material loss, and the polys...Designing a better carbon framework is critical for harnessing the high theoretical capacity of Li-S batteries and avoiding their drawbacks, such as the insulating nature of sulfur, active material loss, and the polysulfide shuttle reaction. Here, we report an ingenious design of hollow carbon nanofibers with closed ends and protogenetic mesopores in the shell that can be retracted to micropores after sulfur infusion. Such dynamic adjustable pore sizes ensure a high sulfur loading, and more importantly, eliminate excessive contact of sulfur species with the electrolyte. Together, the high aspect ratio and thin carbon shells of the carbon nanofibers facilitate rapid transport of Li^＋ ions and electrons, and the closed-end structure of the carbon nanofibers further blocks polysulfide dissolution from both ends, which is remarkably different from that for carbon nanotubes with open ends. The obtained sulfur-carbon cathodes exhibit excellent performance marked by high sulfur utilization, superior rate capability （1,170, 1,050, and 860 mA.h.g-1 at 1.0, 2.0, and 4.0 C （1 C = 1.675 A·g^-1）, respectively）, and a stable reversible capacity of 847 mA·h·g^-1 after 300 cycles at a high rate of 2.0 C.展开更多
Lithium sulfur battery has been identified as a promising candidate for next storage devices attributing to ultrahigh energy density.However,non-conductive nature of sulfur and shuttling effect of soluble lithium poly...Lithium sulfur battery has been identified as a promising candidate for next storage devices attributing to ultrahigh energy density.However,non-conductive nature of sulfur and shuttling effect of soluble lithium polysulfides are intractable remaining problems.Herein,we develop a highly conductive nickel-rich Ni12P5/CNTs hybrid with high specific surface area as sulfur host to address these issues.The polar nature of Ni12Ps/CNTs can significantly relieve the shuttle effect by means of a strong affinity towards lithium polysulfides and enhance kinetics of polysulfides redox reactions.In addition,the Ni12P5/CNTs with a superior conductivity (500 S·m^-1) and high surface area of 395 m^2·g^-1 enables the effective electron transfer and expedited interfacial reaction.As a result,Ni12P5/CNTs hosted sulfur cathode exhibits high rate capability (784 mAh·g^-1 at 4 C) and stable cycling performance with a negligible capacity fading of 0.057 % per cycle over 1,000 cycles at 0.5 C.This work paves an alternative way for designing high performance sulfur cathodes involved metal-rich phosphides.展开更多
Porous carbon spheres with an internal gridded hollow structure and microporous shell have always been attractive as carbon hosts for electrochemical energy storage. Such carbon hosts can limit active species loss and...Porous carbon spheres with an internal gridded hollow structure and microporous shell have always been attractive as carbon hosts for electrochemical energy storage. Such carbon hosts can limit active species loss and enhance electronic conductivity throughout the entire framework. Herein, a synthesis approach of internal gridded hollow carbon spheres is developed from solid polymer spheres rather than originally gridded polymer spheres under a controlled pyrolysis micro-environment. The crucial point of this approach is the fabrication of a silica fence around solid polymer spheres, under which the free escaping of the pyrolysis gas will be partly impeded, thus offering a reconstitution opportunity for an internal structure of solid polymer spheres. As a result, the interior of carbon spheres is sculptured into a gridded hollow structure with microporous skin. Furthermore, the size and density of carbon-bridge grids can be modulated by altering the crosslinking degree of polymer spheres and varying pyrolysis conditions. Such gridded hollow carbon spheres show good performance as sulfur hosts for Li-S battery.展开更多
The commercialization of lithium-sulfur (Li-S) battery could be accelerated by designing advanced sulfur cathode with high sulfur utilization and stable cycle life at a high sulfur loading. To allow the energy density...The commercialization of lithium-sulfur (Li-S) battery could be accelerated by designing advanced sulfur cathode with high sulfur utilization and stable cycle life at a high sulfur loading. To allow the energy density of Li-S batteries comparable to that of commercial Li-ion batteries, the areal capacity of sulfur cathode should be above 4 mA·h·cm−2. In general, a high sulfur loading often causes rapid capacity fading by slowing electron/ion transport kinetics, catastrophic shuttle effect and even cracking the electrodes. To address this issue, herein, a multilevel structured carbon film is built by covering highly conductive CNTs and hollow carbon nanofiber together with carbon layer via chemical vapor deposition. The self-standing carbon film exhibits well-interweaved conductive network, hollow fibrous structure and abundant N, O co-doped active sites, which combine the merits of high electronic conductivity (1200·S·m−1), high porosity and polar characteristic in one host. Benefiting from this attractive multilevel structure, the obtained sulfur cathode based on the carbon film host shows an ultra-high areal capacity of 8.9 mA·h·cm−2 at 0.2 C with outstanding cyclability over 60 cycles. This work shed light on designing advanced sulfur host for Li-S batteries with high areal capacity and high cycle stability, and might make a contribution to the commercialization of Li-S batteries.展开更多
Summary of main observation and conclusion We demonstrate the synthesis of cathode material with nanosized sulfur by a precipitation method making use of the alterable solubility of chitosan (CTS) in aqueous solution....Summary of main observation and conclusion We demonstrate the synthesis of cathode material with nanosized sulfur by a precipitation method making use of the alterable solubility of chitosan (CTS) in aqueous solution.Mesoporous Ketjen Black (KB) and carbon nanotube (CNT) are added as conductive agents to provide the three-dimensional electric channels.This method can reduce the size of the sulfur particles,thus the nanosized sulfur obtained can fully contact with the conductive agent,which could increase the utilization of sulfur and improve the capacity of Li-S batteries.Moreover,CTS with abundant hydroxyl and amine groups has strong interaction with polysulfides,which can improve the stability of Li-S batteries.As a result,the obtained CTS/C-S cathode containing 76 wt% sulfur delivers an impressively initial discharge specific capacity of 1141.6 mA.h.g^-1 at 0.5 C and maintains a capacity of 842.3 mA·h·g-1 after 300 cycles.Our finding paves a way for the rational design of high-performance sulfur cathodes for advanced Li-S batteries.展开更多
Carbon nanosheets with a tunable mesopore size, large pore volume, and good electronic conductivity are synthesized via a solution-chemistry approach. In this synthesis, diaminohexane and graphene oxide （GO） are use...Carbon nanosheets with a tunable mesopore size, large pore volume, and good electronic conductivity are synthesized via a solution-chemistry approach. In this synthesis, diaminohexane and graphene oxide （GO） are used as the structural directing agents, and a silica colloid is used as a mesopores template. Diaminohexane plays a crucial role in bridging silica colloid particles and GO, as well as initiating the polymerization of benzoxazine on the surfaces of both the GO and silica, resulting in the formation of a hybrid nanosheet polymer. The carbon nanosheets have graphene embedded in them and have several spherical mesopores with a pore volume up to 3.5 cm^3·g^-1 on their surfaces. These nuerous accessible mesopores in the carbon layers can act as reservoirs to host a high loading of active charge-storage materials with good dispersion and a uniform particle size. Compared with active materials with wide particle-size distributions, the unique proposed configuration with confined and uniform particles exhibits superior electrochemical performance during lithiation and delithiation, espedaUy during long cycles and at high rates.展开更多
Confined nanospace pyrolysis(CNP)has attracted increasing attention as a general strategy to prepare task-specific hollow structured porous carbons(HSPCs)in the past decade.The unique advantages of the CNP strategy in...Confined nanospace pyrolysis(CNP)has attracted increasing attention as a general strategy to prepare task-specific hollow structured porous carbons(HSPCs)in the past decade.The unique advantages of the CNP strategy include its outstanding ability in control of the monodispersity,porosity and internal cavity of HSPCs.As a consequence,the obtained HSPCs perform exceptionally well in applications where a high dispersibility and tailored cavity are particularly required,such as drug delivery,energy storage,catalysis and so on.In this review,the fundamentals of the CNP strategy and its advances in structural alternation is first summarized,then typical applications are discussed by exemplifying specific synthesis examples.In addition,this review offers insights into future developments for advanced task-specific hollow structured porous materials prepared by the CNP strategy.展开更多
基金financially supported by a Joint Sino-German Research Project(21761132011)the National Natural Science Foundation of China(No.21776041)the Cheung Kong Scholars Programme of China(T2015036).
文摘Porous carbon materials with developed porosity,high surface area and good thermal-and chemicalresistance are advantageous for gas adsorption and separation.However,most carbon adsorbents are in powder form which exhibit high pressure drop when deployed in practical separation bed.While monolithic carbons have largely addressed the pulverization problem and preserved kinetics and usually suffer from abrasion during multiple adsorption-desorption cycles.Herein,we proposed the designed synthesis of mechanically robust carbon monoliths with hierarchical pores,solid nitrogen-containing framework.The synthesis started with the polymerization of resorcinol and formaldehyde under weakly acidic conditions generated from cyanuric acid,and then an appropriate amount of hexamethylenetetramine(HMTA)was added as a crosslinker to prompt the formation of three dimensional frameworks.After carbonization process,the as-obtained porous carbon monoliths have a high radial compressive strength of 886 N/cm as well as a BET specific surface area of up to 683 m2/g.At approximately 1 bar,the CO2 equilibrium capacities of the monoliths are in the range of 3.1–4.0 mmol/g at 273 K and of 2.3–3.0 mmol/g at 298 K,exhibiting high selectivity for the capture of CO2 over N2 from a stream which consists of 16.7%(v%)CO2 in N2.Meanwhile,they undergo a facile CO2 release in an argon stream at 298 K,indicating a good regeneration capacity.After cycle testing,sieving and regeneration,the adsorbent has no mass loss,compared to that of its fresh counterpart.
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. DUT12ZD218)the National Natural Science Foundation of China (Grant No. 21103184)the Ph. D. Programs Foundation (Grant No. 20100041110017) of Ministry of Education of China
文摘To improve the initial coulombic efficiency and bulk density of ordered mesoporous carbons, active Fe203 nanoparticles were introduced into tubular mesopore channels of CMK-5 carbon, which possesses high specific surface area （〉1700 m2.g-1） and large pore volume （〉1.8 cm3-g-1）. Fine Fe203 nanoparticles with sizes in the range of 5-7 nm were highly and homogenously encapsulated into CMK-5 matrix through ammonia-treatment and subsequent pyrolysis method. The Fe203 loading was carefully tailored and designed to warrant a high Fe203 content and adequate buffer space for improving the electrochemical performance. In particular, such Fe203 and mesoporous carbon composite with 47 wt% loading exhibits a considerably stable cycle performance （683 mAh.g-1 after 100 cycles, 99% capacity retention against that of the second cycle） as well as good rate capability. The fabrication strategy can effectively solve the drawback of single material, and achieve a high-performance lithium electrode material.
基金supported by the National Natural Science Foundation of China(No.21776041 and No.21875028)the Cheung Kong Scholars Programme of China(T2015036)。
文摘Assembly of the top-down graphene units mostly results in 3D porous structure with randomly organized pores.The direct bottom-up synthesis of macroscopic 2D graphene sheets with organized pores are long sought in materials chemistry field,but rarely achieved.Herein,we present a self-catalysisassisted bottom-up route usingL-glutamic acid and iron chloride as starting materials for the fabrication of the millimeter-sized few-layer graphene sheets with aligned porous channels parallel to the 2D direction.The amino-and carboxyl-functional groups inL-glutamic acid can coordinate with iron cations,thus allowing an atomic dispersion of iron cations.The pyrolysis thus initiated the growth of graphene catalyzed by in-situ generated iron nanoparticles,and a dynamic flow of iron nanoparticles eventually led to the formation of millimeter-sized few-layer graphene sheets with aligned channels(60-85 nm in diameter).Used as anodes in lithium-ion batteries,these graphene sheets showed a good rate capability(142 m A h g^(-1) at 2 A g^(-1))and high capacity retention of 93%at 2 A g^(-1) after 1200 cycles.Kinetic analysis revealed that lithium ions storage was dominated by diffusion behavior and capacitive behavior together,in that graphene sheets with aligned channels could accelerate electron transfer and shorten lithium ions transport pathway.This work provides a novel approach to prepare unique porous graphene materials with specific structure for energy storage.
基金supported by the National Natural Science Foundation of China(21733002)Joint Sino-German Research Project(2161101168)Cheung Kong Scholars Program of China(T2015036)~~
基金supported by the National Key Research and Development Project(2018YFA0209404)the State Key Program of the National Natural Science Foundation of China(21733002)the National Natural Science Foundation of China(U1908203)。
文摘Alumina materials are widely applied either as a catalyst or support in various industrial catalytic processes. Impurities in alumina that are unfriendly to catalytic performance are inevitably present during the production processes. Facing this problem, we here report that the use of sulfur-containing alumina as the support can generate active alumina-supported platinum catalyst, which exhibits superior propylene selectivity and anti-coking ability during propane dehydrogenation. It demonstrated that the sulfur impurity in alumina is not entirely detrimental. During the reduction process, the formation of gas-phase sulfur species increased the electrons and poisoned unsaturated sites of platinum particles. The sulfur impurity in alumina can be removed through a hydrogen reduction process, and the degree of desulfurization is correlated with the operating temperature. This study demonstrated that the rational use of impurity will contribute to the design of a catalyst with high reactivity for potential applications.
基金supported by the National Natural Science Foundation of China(Nos.21875028 and 22288101)Liaoning Revitalization Talents Program(No.XLYC1902045)the Science and Technology Innovation Fund of Dalian(No.2020JJ26GX030).
文摘Anisotropic nanoparticles,giving rise to a large number of novel physicochemical properties and functionalities,have provoked increasing attentions in nanoscience and nanotechnology.The remained challenge is to develop synthetic methods for the fabrication of anisotropic nanoparticles with less symmetry under the principle of minimum surface free energy.Here,we established a crystallization-assisted asymmetric assembly method for the synthesis of anisotropic polymer nanocrescents and their carbonaceous analogues by using triblock copolymer F127 and octadecanol in aqueous solution.With the aid of molecular dynamics(MD)simulation,we demonstrate that the observed crescent structure is caused by asymmetry distribution of octadecanol crystal within the hydrophobic core of F127 micelles,via the formation of intermediate elliptic micelles bearing hydrophobic ends that further fuse with each other end-to-end at an angle into curing nanocrescent morphology.The influences of annealing time,annealing temperature,and mole ratios of precursors that govern the kinetics of the assembly and polymerization process were systematically investigated and a series of polymer nanocrescents with tunable length of~85 to~262 nm and aspect ratio of~1.1 to~3.0 were prepared.The ability to create novel crescent-shaped polymer and carbon nanoparticles and the identification of asymmetric assembly process by combining experiment and simulation study will provide a valuable contribution both to theoretical and technological researches.
基金This work was supported by the National Basic Research Program of China （No. 2013CB934104）, the National Natural Science Foundation of China （Nos. 21225312 and 21376047）, and Cheung Kong Scholars Program of China （No. T2015036）.
文摘Designing a better carbon framework is critical for harnessing the high theoretical capacity of Li-S batteries and avoiding their drawbacks, such as the insulating nature of sulfur, active material loss, and the polysulfide shuttle reaction. Here, we report an ingenious design of hollow carbon nanofibers with closed ends and protogenetic mesopores in the shell that can be retracted to micropores after sulfur infusion. Such dynamic adjustable pore sizes ensure a high sulfur loading, and more importantly, eliminate excessive contact of sulfur species with the electrolyte. Together, the high aspect ratio and thin carbon shells of the carbon nanofibers facilitate rapid transport of Li^＋ ions and electrons, and the closed-end structure of the carbon nanofibers further blocks polysulfide dissolution from both ends, which is remarkably different from that for carbon nanotubes with open ends. The obtained sulfur-carbon cathodes exhibit excellent performance marked by high sulfur utilization, superior rate capability （1,170, 1,050, and 860 mA.h.g-1 at 1.0, 2.0, and 4.0 C （1 C = 1.675 A·g^-1）, respectively）, and a stable reversible capacity of 847 mA·h·g^-1 after 300 cycles at a high rate of 2.0 C.
基金the National Natural Science Foundation of China (Nos.21776041 and 21875028)Cheung Kong Scholars Programme of China (No.T2015036).
文摘Lithium sulfur battery has been identified as a promising candidate for next storage devices attributing to ultrahigh energy density.However,non-conductive nature of sulfur and shuttling effect of soluble lithium polysulfides are intractable remaining problems.Herein,we develop a highly conductive nickel-rich Ni12P5/CNTs hybrid with high specific surface area as sulfur host to address these issues.The polar nature of Ni12Ps/CNTs can significantly relieve the shuttle effect by means of a strong affinity towards lithium polysulfides and enhance kinetics of polysulfides redox reactions.In addition,the Ni12P5/CNTs with a superior conductivity (500 S·m^-1) and high surface area of 395 m^2·g^-1 enables the effective electron transfer and expedited interfacial reaction.As a result,Ni12P5/CNTs hosted sulfur cathode exhibits high rate capability (784 mAh·g^-1 at 4 C) and stable cycling performance with a negligible capacity fading of 0.057 % per cycle over 1,000 cycles at 0.5 C.This work paves an alternative way for designing high performance sulfur cathodes involved metal-rich phosphides.
基金The authors are grateful to the financial support by the National Natural Science Foundation of China(Nos.21776041 and 21875028)Cheung Kong Scholars Programme of China(No.T2015036).
文摘Porous carbon spheres with an internal gridded hollow structure and microporous shell have always been attractive as carbon hosts for electrochemical energy storage. Such carbon hosts can limit active species loss and enhance electronic conductivity throughout the entire framework. Herein, a synthesis approach of internal gridded hollow carbon spheres is developed from solid polymer spheres rather than originally gridded polymer spheres under a controlled pyrolysis micro-environment. The crucial point of this approach is the fabrication of a silica fence around solid polymer spheres, under which the free escaping of the pyrolysis gas will be partly impeded, thus offering a reconstitution opportunity for an internal structure of solid polymer spheres. As a result, the interior of carbon spheres is sculptured into a gridded hollow structure with microporous skin. Furthermore, the size and density of carbon-bridge grids can be modulated by altering the crosslinking degree of polymer spheres and varying pyrolysis conditions. Such gridded hollow carbon spheres show good performance as sulfur hosts for Li-S battery.
基金This work was supported by the National Science Fund for the National Natural Science Foundation of China(Nos.21776041 and 21875028)Cheung Kong Scholars Programme of China(No.T2015036).
文摘The commercialization of lithium-sulfur (Li-S) battery could be accelerated by designing advanced sulfur cathode with high sulfur utilization and stable cycle life at a high sulfur loading. To allow the energy density of Li-S batteries comparable to that of commercial Li-ion batteries, the areal capacity of sulfur cathode should be above 4 mA·h·cm−2. In general, a high sulfur loading often causes rapid capacity fading by slowing electron/ion transport kinetics, catastrophic shuttle effect and even cracking the electrodes. To address this issue, herein, a multilevel structured carbon film is built by covering highly conductive CNTs and hollow carbon nanofiber together with carbon layer via chemical vapor deposition. The self-standing carbon film exhibits well-interweaved conductive network, hollow fibrous structure and abundant N, O co-doped active sites, which combine the merits of high electronic conductivity (1200·S·m−1), high porosity and polar characteristic in one host. Benefiting from this attractive multilevel structure, the obtained sulfur cathode based on the carbon film host shows an ultra-high areal capacity of 8.9 mA·h·cm−2 at 0.2 C with outstanding cyclability over 60 cycles. This work shed light on designing advanced sulfur host for Li-S batteries with high areal capacity and high cycle stability, and might make a contribution to the commercialization of Li-S batteries.
基金supported by the National Natural Science Foundation of China (Nos.21776041 and 21875028)the Cheung Kong Scholars Programme of China (No.T2015036).
文摘Summary of main observation and conclusion We demonstrate the synthesis of cathode material with nanosized sulfur by a precipitation method making use of the alterable solubility of chitosan (CTS) in aqueous solution.Mesoporous Ketjen Black (KB) and carbon nanotube (CNT) are added as conductive agents to provide the three-dimensional electric channels.This method can reduce the size of the sulfur particles,thus the nanosized sulfur obtained can fully contact with the conductive agent,which could increase the utilization of sulfur and improve the capacity of Li-S batteries.Moreover,CTS with abundant hydroxyl and amine groups has strong interaction with polysulfides,which can improve the stability of Li-S batteries.As a result,the obtained CTS/C-S cathode containing 76 wt% sulfur delivers an impressively initial discharge specific capacity of 1141.6 mA.h.g^-1 at 0.5 C and maintains a capacity of 842.3 mA·h·g-1 after 300 cycles.Our finding paves a way for the rational design of high-performance sulfur cathodes for advanced Li-S batteries.
文摘Carbon nanosheets with a tunable mesopore size, large pore volume, and good electronic conductivity are synthesized via a solution-chemistry approach. In this synthesis, diaminohexane and graphene oxide （GO） are used as the structural directing agents, and a silica colloid is used as a mesopores template. Diaminohexane plays a crucial role in bridging silica colloid particles and GO, as well as initiating the polymerization of benzoxazine on the surfaces of both the GO and silica, resulting in the formation of a hybrid nanosheet polymer. The carbon nanosheets have graphene embedded in them and have several spherical mesopores with a pore volume up to 3.5 cm^3·g^-1 on their surfaces. These nuerous accessible mesopores in the carbon layers can act as reservoirs to host a high loading of active charge-storage materials with good dispersion and a uniform particle size. Compared with active materials with wide particle-size distributions, the unique proposed configuration with confined and uniform particles exhibits superior electrochemical performance during lithiation and delithiation, espedaUy during long cycles and at high rates.
基金financially supported by the National Natural Science Foundation of China(Nos.20873014 and 21073026)National Natural Science Foundation for Distinguished Young Scholars(No.21225312)the Cheung Kong Scholars Program of China(No.T2015036).
文摘Confined nanospace pyrolysis(CNP)has attracted increasing attention as a general strategy to prepare task-specific hollow structured porous carbons(HSPCs)in the past decade.The unique advantages of the CNP strategy include its outstanding ability in control of the monodispersity,porosity and internal cavity of HSPCs.As a consequence,the obtained HSPCs perform exceptionally well in applications where a high dispersibility and tailored cavity are particularly required,such as drug delivery,energy storage,catalysis and so on.In this review,the fundamentals of the CNP strategy and its advances in structural alternation is first summarized,then typical applications are discussed by exemplifying specific synthesis examples.In addition,this review offers insights into future developments for advanced task-specific hollow structured porous materials prepared by the CNP strategy.
