Carbon nanofibers films are typical flexible electrode in the field of energy storage,but their application in Zinc-ion hybrid capacitors(ZIHCs)is limited by the low energy density due to the lack of active adsorption...Carbon nanofibers films are typical flexible electrode in the field of energy storage,but their application in Zinc-ion hybrid capacitors(ZIHCs)is limited by the low energy density due to the lack of active adsorption sites.In this work,an in-situ exfoliation strategy is reported to modulate the chemisorption sites of carbon nanofibers by high pyridine/pyrrole nitrogen doping and carbonyl functionalization.The experimental results and theoretical calculations indicate that the highly electronegative pyridine/pyrrole nitrogen dopants can not only greatly reduce the binding energy between carbonyl group and Z n2+by inducing charge delocalization of the carbonyl group,but also promote the adsorption of Zn2+by bonding with the carbonyl group to form N–Zn–O bond.Benefit from the multiple highly active chemisorption sites generated by the synergy between carbonyl groups and pyridine/pyrrole nitrogen atoms,the resulting carbon nanofibers film cathode displays a high energy density,an ultralong-term lifespan,and excellent capacity reservation under commercial mass loading(14.45 mg cm-2).Particularly,the cathodes can also operate stably in flexible or quasi-solid devices,indicating its application potential in flexible electronic products.This work established a universal method to solve the bottleneck problem of insufficient active adsorption sites of carbon-based ZIHCs.Imoproved should be changed into Improved.展开更多
In this study, with borneol fragments in the crystallized mother liquor of natural borneol used as the raw materials, supercritical carbon dioxide method is adopted for refining to get high purity borneol. The result ...In this study, with borneol fragments in the crystallized mother liquor of natural borneol used as the raw materials, supercritical carbon dioxide method is adopted for refining to get high purity borneol. The result of the experiment shows that the yield and purity are excellent with an extraction pressure of 11 MPa, an extracting temperature of 40°C, a carbon dioxide flow rate of 25 L·h<sup>-</sup><sup>1</sup> and an extraction time of 20 minutes. After detected by gas chromatography, the purity of the crystallization products could reach 96%.展开更多
With the emergence of wearable electronics,flexible energy storage materials have been extensively studied in recent years.However,most studies focus on improving the electrochemical properties,ignoring the flexible m...With the emergence of wearable electronics,flexible energy storage materials have been extensively studied in recent years.However,most studies focus on improving the electrochemical properties,ignoring the flexible mechanism and structure design for flexible electrode materials with high rate capacities and long-time stability.In this study,porous,kinked,and entangled network structures are designed for highly flexible fiber films.Based on theoretical analysis and finite element simulation,the bending degree of the porous structure(30%porosity)increased by 192%at the micro-level.An appropriate increase in kinking degree at the meso-level and contact points in entanglement network at the macro-level are beneficial for the flexibility of fiber films.Therefore,a porous and entangled network of sulfur-/nitrogen-co-doped kinked carbon nanofibers(S/N-KCNFs)is synthesized.The nanofiber films synthesized from melamine as nitrogen sources and segmented vulcanization exhibited a porous,kinked,and entangled network structure,and the stretching degree increased several times.The flexible S/N-KCNFs anode delivered a higher rate performance of 270 mAh g−1 at a current density of 2000 mA g−1 and a higher capacity retention rate of 93.3%after 2000 cycles.Moreover,the foldable pouch cell assembled by potassium-ion hybrid supercapacitor operated safely at large-angle bending and showed long-time stability of 88%capacity retention after 4000 cycles.This study provides a new idea and strategy for the flexible structure design of high-performance potassium-ion storage materials.展开更多
Potassium-based energy storage devices(PEDS)are considered as hopeful candidates for energy storage applications because of the abundant potassium resources in nature and high mobility in the electrolyte.although carb...Potassium-based energy storage devices(PEDS)are considered as hopeful candidates for energy storage applications because of the abundant potassium resources in nature and high mobility in the electrolyte.although carbon materials show great potential for potassium-ion storage,poor rate performance,and unsatisfactory cycle lifespan in existing carbon-based PIBs anode,it also cannot match the dynamics and stability of the capacitor cathode.Nitrogen doping has been proven to be a effective modification strategy to improve the electrochemical performance of carbon materials.Hence,we prepare carbon nanofibers and g-C_(3)N_(4)composites with high nitrogen contents(19.78 at%);moreover,the sum of pyrrolic N and pyridinic N is up to 59.51%.It achieves high discharge capacity(391 m Ah g^(-1)at0.05 A g^(-1)),rate capacity(141 m Ah g^(-1)at 2 A g^(-1)),and long cycling performance(201 m Ah g^(-1)at 1 A g^(-1)over 3000 cycles)when as an anode for PIBs.Furthermore,it can deliver promising discharge capacity of132 m Ah g^(-1)at 0℃.Moreover,as battery anode for potassium-ion hybrid capacitors(PIHC)device with an active carbon cathode,it delivers energy/power density(62 and 2102 W kg^(-1))as well as high reversible capacity(106 m Ah g^(-1)at 1 A g^(-1)).展开更多
Nickle sulfides are attractive anode materials for sodium-ion batteries(SIBs) due to their rich structures and natural abundance. However, their applications are greatly hindered by the large volume expansion and poor...Nickle sulfides are attractive anode materials for sodium-ion batteries(SIBs) due to their rich structures and natural abundance. However, their applications are greatly hindered by the large volume expansion and poor cycling properties. The introduction of hollow structures and heteroatom-doped carbon layers are effective ways to solve these issues. Here, nitrogen, sulfur co-doped carbon coated Ni3S2(abbreviated as, Ni3S2@NSC) nanotubes were prepared by a novel templating route. During the annealing process, NiS2 acts as both a precursor to Ni3S2 and an S-doped sulfur source.No additional sulfur source was used during the S-doping procedure, suggesting an atomically economic synthesis process. As anodes for sodium-ion half-cells, Ni3S2@NSCs exhibited high discharge capacity of 481 mA h g^-1 at 0.1 A g^-1 after 100 cycles with exceptional capacity retention of 98.6%.Furthermore, they maintained excellent rate capability of 318 mA h g^-1 even at elevated current density of 5 A g^-1. Sodium-ion full-cells assembled from the Ni3S2@NSC anodes and Na3V2(PO4)3(NVP@C) cathodes also presented superior capacities and cyclabilities. These features can be attributed to the N, S co-doped carbon coated hollow structure that provided sufficient contact between the electrode and electrolyte,enhanced surface ion storage performance(capacitive effect),and improved structural stability of electrode materials.展开更多
Iron selenide(FeSe)has drawn attention due to its resource-rich,environment-friendly,and low toxicity advantages.However,FeSe,like many transition metal selenides,has some limitations,including low conductivity and ma...Iron selenide(FeSe)has drawn attention due to its resource-rich,environment-friendly,and low toxicity advantages.However,FeSe,like many transition metal selenides,has some limitations,including low conductivity and massive volume expansion during charge and discharge.Thus,graphene oxide-controlled FeSe nanoparticles embedded in carbon nanofibers were created using graphene oxide as an additive in the electrospinning precursor.The composites as the anodes for potassium-ion batteries(KIBs)can maintain an excellent capacity of 409 mA h g^(-1)at a current density of 0.2 A g^(-1) after 400 cycles with the capacity retention of nearly 100%.Even at 2 A g^(-1),the capacity can maintain 200 mA h g^(-1) after 1700 cycles with the capacity retention of about 80.9%.It was discovered that the addition of graphene oxide can reduce the diameter of FeSe nanoparticles and cause most nanoparticles to be wrapped in carbon fibers,which can relieve volume expansion and improve composite stability.Furthermore,the graphene and carbon fiber matrix can result in high K-ion diffusion kinetics,improved material conductivity,and enhanced pseudo-capacitance performance,endowing composites with excellent cycling and rate performance.The strategy of using graphene oxide to control the microstructure and improve the conductivity of carbon fiber composites may provide a new idea for future application and development of carbon fibers in other energy devices.展开更多
过渡金属硫化物作为钾离子电池的高理论容量阳极,由于其电导率低、循环过程体积膨胀大,导致其倍率性能和循环稳定性较差.本文采用氧化石墨烯(GO)来控制纳米颗粒在纤维中的粒径和分布,以提高复合纤维的导电性和拉伸变形.此外,由异质结构...过渡金属硫化物作为钾离子电池的高理论容量阳极,由于其电导率低、循环过程体积膨胀大,导致其倍率性能和循环稳定性较差.本文采用氧化石墨烯(GO)来控制纳米颗粒在纤维中的粒径和分布,以提高复合纤维的导电性和拉伸变形.此外,由异质结构和氧化石墨烯组成的三维导电碳网络(ZnS-CoS@GO@CNFs)可以加速钾离子储存的动力学并稳定钾离子储存.作为钾离子电池的阳极材料,该复合材料在3 A g^(−1)下具有210 mA h g^(−1)的优异倍率性能.在2 A g^(−1)的大电流下经历2800次循环后仍表现出171 mA h g^(−1)的容量,容量保持率为97.7%.此外,当纳米纤维膜用作自支撑阳极时,仍然可以保持稳定的容量输出(在0.1 A g^(−1)下100次循环后容量为302 mA h g^(−1)).由钾离子混合电容器组装的可折叠袋状电池在多角度重复弯曲和最终恢复的情况下仍然可以安全地工作,并且可以提供大的能量密度(134 W h kg^(−1))和功率密度(5815 W kg^(−1)).优异的电化学性能进一步揭示了多功能氧化石墨烯复合纤维膜的应用前景.展开更多
Metal sulfides with high specific capacities have drawn considerable attention in the field of sodium-ion batteries(SIBs).As a typical metal sulfide,FeV_(2)S_(4)always suffers rapid decay of capacities because of its ...Metal sulfides with high specific capacities have drawn considerable attention in the field of sodium-ion batteries(SIBs).As a typical metal sulfide,FeV_(2)S_(4)always suffers rapid decay of capacities because of its low stability arising from large volume change.FeV_(2)S_(4)nanoparticles with controllable sizes and distribution are encapsulated in carbon nanofibers(CNFs)with the help of graphene oxide(GO)to fabricate FeV_(2)S_(4)@GO@CNF.As a result,FeV_(2)S_(4)@GO@CNF anodes show enhanced electrochemical performances for Na+storage when compared with FeV_(2)S_(4)@CNF with more particles on the surface.Typically,the capacity of FeV_(2)S_(4)@GO@CNF can be maintained at 411 mA h g^(−1)after 200 cycles(0.1 A g^(−1))and 227 mA h g^(−1)over 500 cycles(1 A g^(−1))in SIBs.Moreover,they can deliver a capacity of 170.2 mA h g^(−1)after 150 cycles(0.1 A g^(−1))at 0℃.In addition,full cells based on FeV_(2)S_(4)@GO@CNF anodes and Na3V2(PO4)3/C cathodes achieve a remarkable capacity of 164 mA h g^(−1)after 100 cycles at 0.5 A g^(−1).The high specific capacities and stability of FeV_(2)S_(4)@GO@CNF can be attributed to GO,which controls the size of FeV_(2)S_(4)nanoparticles and their distribution in CNFs,resulting in the enhanced stability of FeV_(2)S_(4)@GO@CNF.This study may provide a new strategy for the synthesis of nanoparticle–CNF composites in catalysts and batteries.展开更多
基金funds from the National Natural Science Foundation of China(51772082,51804106,and 51574117)the Natural Science Foundation of Hunan Province(2019JJ30002,2019JJ50061 and 2020CB1007)Natural Science Foundation of Guangdong Providence(2018A030310571)。
文摘Carbon nanofibers films are typical flexible electrode in the field of energy storage,but their application in Zinc-ion hybrid capacitors(ZIHCs)is limited by the low energy density due to the lack of active adsorption sites.In this work,an in-situ exfoliation strategy is reported to modulate the chemisorption sites of carbon nanofibers by high pyridine/pyrrole nitrogen doping and carbonyl functionalization.The experimental results and theoretical calculations indicate that the highly electronegative pyridine/pyrrole nitrogen dopants can not only greatly reduce the binding energy between carbonyl group and Z n2+by inducing charge delocalization of the carbonyl group,but also promote the adsorption of Zn2+by bonding with the carbonyl group to form N–Zn–O bond.Benefit from the multiple highly active chemisorption sites generated by the synergy between carbonyl groups and pyridine/pyrrole nitrogen atoms,the resulting carbon nanofibers film cathode displays a high energy density,an ultralong-term lifespan,and excellent capacity reservation under commercial mass loading(14.45 mg cm-2).Particularly,the cathodes can also operate stably in flexible or quasi-solid devices,indicating its application potential in flexible electronic products.This work established a universal method to solve the bottleneck problem of insufficient active adsorption sites of carbon-based ZIHCs.Imoproved should be changed into Improved.
文摘In this study, with borneol fragments in the crystallized mother liquor of natural borneol used as the raw materials, supercritical carbon dioxide method is adopted for refining to get high purity borneol. The result of the experiment shows that the yield and purity are excellent with an extraction pressure of 11 MPa, an extracting temperature of 40°C, a carbon dioxide flow rate of 25 L·h<sup>-</sup><sup>1</sup> and an extraction time of 20 minutes. After detected by gas chromatography, the purity of the crystallization products could reach 96%.
基金funds from the National Natural Science Foundation of China(51772082,51804106,and 51574117)the Natural Science Foundation of Hunan Province(2019JJ30002,2019JJ50061)the China Postdoctoral Science Foundation(2018T110822,2017M610495).
文摘With the emergence of wearable electronics,flexible energy storage materials have been extensively studied in recent years.However,most studies focus on improving the electrochemical properties,ignoring the flexible mechanism and structure design for flexible electrode materials with high rate capacities and long-time stability.In this study,porous,kinked,and entangled network structures are designed for highly flexible fiber films.Based on theoretical analysis and finite element simulation,the bending degree of the porous structure(30%porosity)increased by 192%at the micro-level.An appropriate increase in kinking degree at the meso-level and contact points in entanglement network at the macro-level are beneficial for the flexibility of fiber films.Therefore,a porous and entangled network of sulfur-/nitrogen-co-doped kinked carbon nanofibers(S/N-KCNFs)is synthesized.The nanofiber films synthesized from melamine as nitrogen sources and segmented vulcanization exhibited a porous,kinked,and entangled network structure,and the stretching degree increased several times.The flexible S/N-KCNFs anode delivered a higher rate performance of 270 mAh g−1 at a current density of 2000 mA g−1 and a higher capacity retention rate of 93.3%after 2000 cycles.Moreover,the foldable pouch cell assembled by potassium-ion hybrid supercapacitor operated safely at large-angle bending and showed long-time stability of 88%capacity retention after 4000 cycles.This study provides a new idea and strategy for the flexible structure design of high-performance potassium-ion storage materials.
基金supported by the National Natural Science Foundation of China(Grants 51772082,51574117,and 51804106)the Research Projects of Degree and Graduate Education Teaching Reformation in Hunan Province(JG2018B031)+2 种基金the Natural Science Foundation of Hunan Province(2019JJ30002,2019JJ50061)the Guangdong Basic and Applied Basic Research Foundation(No.2019B151502045)the National Natural Science Foundation of China(Nos.51802361,51972351)
文摘Potassium-based energy storage devices(PEDS)are considered as hopeful candidates for energy storage applications because of the abundant potassium resources in nature and high mobility in the electrolyte.although carbon materials show great potential for potassium-ion storage,poor rate performance,and unsatisfactory cycle lifespan in existing carbon-based PIBs anode,it also cannot match the dynamics and stability of the capacitor cathode.Nitrogen doping has been proven to be a effective modification strategy to improve the electrochemical performance of carbon materials.Hence,we prepare carbon nanofibers and g-C_(3)N_(4)composites with high nitrogen contents(19.78 at%);moreover,the sum of pyrrolic N and pyridinic N is up to 59.51%.It achieves high discharge capacity(391 m Ah g^(-1)at0.05 A g^(-1)),rate capacity(141 m Ah g^(-1)at 2 A g^(-1)),and long cycling performance(201 m Ah g^(-1)at 1 A g^(-1)over 3000 cycles)when as an anode for PIBs.Furthermore,it can deliver promising discharge capacity of132 m Ah g^(-1)at 0℃.Moreover,as battery anode for potassium-ion hybrid capacitors(PIHC)device with an active carbon cathode,it delivers energy/power density(62 and 2102 W kg^(-1))as well as high reversible capacity(106 m Ah g^(-1)at 1 A g^(-1)).
基金supported by the National Natural Science Foundation of China (51772082, 51804106 and 51574117)the Natural Science Foundation of Hunan Province (2019JJ30002 and 2019JJ50061)the China Postdoctoral Science Foundation (2018T110822 and 2017M610495)
文摘Nickle sulfides are attractive anode materials for sodium-ion batteries(SIBs) due to their rich structures and natural abundance. However, their applications are greatly hindered by the large volume expansion and poor cycling properties. The introduction of hollow structures and heteroatom-doped carbon layers are effective ways to solve these issues. Here, nitrogen, sulfur co-doped carbon coated Ni3S2(abbreviated as, Ni3S2@NSC) nanotubes were prepared by a novel templating route. During the annealing process, NiS2 acts as both a precursor to Ni3S2 and an S-doped sulfur source.No additional sulfur source was used during the S-doping procedure, suggesting an atomically economic synthesis process. As anodes for sodium-ion half-cells, Ni3S2@NSCs exhibited high discharge capacity of 481 mA h g^-1 at 0.1 A g^-1 after 100 cycles with exceptional capacity retention of 98.6%.Furthermore, they maintained excellent rate capability of 318 mA h g^-1 even at elevated current density of 5 A g^-1. Sodium-ion full-cells assembled from the Ni3S2@NSC anodes and Na3V2(PO4)3(NVP@C) cathodes also presented superior capacities and cyclabilities. These features can be attributed to the N, S co-doped carbon coated hollow structure that provided sufficient contact between the electrode and electrolyte,enhanced surface ion storage performance(capacitive effect),and improved structural stability of electrode materials.
基金supported by the National Natural Science Foundation of China(51772082 and 51804106)the Natural Science Foundation of Hunan Province(2019JJ30002 and 2019JJ50061)。
文摘Iron selenide(FeSe)has drawn attention due to its resource-rich,environment-friendly,and low toxicity advantages.However,FeSe,like many transition metal selenides,has some limitations,including low conductivity and massive volume expansion during charge and discharge.Thus,graphene oxide-controlled FeSe nanoparticles embedded in carbon nanofibers were created using graphene oxide as an additive in the electrospinning precursor.The composites as the anodes for potassium-ion batteries(KIBs)can maintain an excellent capacity of 409 mA h g^(-1)at a current density of 0.2 A g^(-1) after 400 cycles with the capacity retention of nearly 100%.Even at 2 A g^(-1),the capacity can maintain 200 mA h g^(-1) after 1700 cycles with the capacity retention of about 80.9%.It was discovered that the addition of graphene oxide can reduce the diameter of FeSe nanoparticles and cause most nanoparticles to be wrapped in carbon fibers,which can relieve volume expansion and improve composite stability.Furthermore,the graphene and carbon fiber matrix can result in high K-ion diffusion kinetics,improved material conductivity,and enhanced pseudo-capacitance performance,endowing composites with excellent cycling and rate performance.The strategy of using graphene oxide to control the microstructure and improve the conductivity of carbon fiber composites may provide a new idea for future application and development of carbon fibers in other energy devices.
基金supported by the National Natural Science Foundation of China(51772082 and 51804106)the Science and Technology Projects of the State Grid Corporation of China(5500-202323102A-1-1-ZN)the Natural Science Foundation of Hunan Province(2023JJ10005).
文摘过渡金属硫化物作为钾离子电池的高理论容量阳极,由于其电导率低、循环过程体积膨胀大,导致其倍率性能和循环稳定性较差.本文采用氧化石墨烯(GO)来控制纳米颗粒在纤维中的粒径和分布,以提高复合纤维的导电性和拉伸变形.此外,由异质结构和氧化石墨烯组成的三维导电碳网络(ZnS-CoS@GO@CNFs)可以加速钾离子储存的动力学并稳定钾离子储存.作为钾离子电池的阳极材料,该复合材料在3 A g^(−1)下具有210 mA h g^(−1)的优异倍率性能.在2 A g^(−1)的大电流下经历2800次循环后仍表现出171 mA h g^(−1)的容量,容量保持率为97.7%.此外,当纳米纤维膜用作自支撑阳极时,仍然可以保持稳定的容量输出(在0.1 A g^(−1)下100次循环后容量为302 mA h g^(−1)).由钾离子混合电容器组装的可折叠袋状电池在多角度重复弯曲和最终恢复的情况下仍然可以安全地工作,并且可以提供大的能量密度(134 W h kg^(−1))和功率密度(5815 W kg^(−1)).优异的电化学性能进一步揭示了多功能氧化石墨烯复合纤维膜的应用前景.
基金supported by the National Natural Science Foundation of China (51772082, 51804106 and 51574117)China Postdoctoral Science Foundation (2018T110822 and 2017M610495)the Natural Science Foundation of Hunan Province (2019JJ30002 and 2019JJ50061)
文摘Metal sulfides with high specific capacities have drawn considerable attention in the field of sodium-ion batteries(SIBs).As a typical metal sulfide,FeV_(2)S_(4)always suffers rapid decay of capacities because of its low stability arising from large volume change.FeV_(2)S_(4)nanoparticles with controllable sizes and distribution are encapsulated in carbon nanofibers(CNFs)with the help of graphene oxide(GO)to fabricate FeV_(2)S_(4)@GO@CNF.As a result,FeV_(2)S_(4)@GO@CNF anodes show enhanced electrochemical performances for Na+storage when compared with FeV_(2)S_(4)@CNF with more particles on the surface.Typically,the capacity of FeV_(2)S_(4)@GO@CNF can be maintained at 411 mA h g^(−1)after 200 cycles(0.1 A g^(−1))and 227 mA h g^(−1)over 500 cycles(1 A g^(−1))in SIBs.Moreover,they can deliver a capacity of 170.2 mA h g^(−1)after 150 cycles(0.1 A g^(−1))at 0℃.In addition,full cells based on FeV_(2)S_(4)@GO@CNF anodes and Na3V2(PO4)3/C cathodes achieve a remarkable capacity of 164 mA h g^(−1)after 100 cycles at 0.5 A g^(−1).The high specific capacities and stability of FeV_(2)S_(4)@GO@CNF can be attributed to GO,which controls the size of FeV_(2)S_(4)nanoparticles and their distribution in CNFs,resulting in the enhanced stability of FeV_(2)S_(4)@GO@CNF.This study may provide a new strategy for the synthesis of nanoparticle–CNF composites in catalysts and batteries.
